• Increasing the uptake of HIV testing among black African communities living in England
• Increasing the uptake of HIV testing among men who have sex with men

The free access support tools from NICE includes:

• Online educational module developed in conjunction with BMJ Learning to help healthcare professionals in primary care and non-HIV specialist settings improve their knowledge of key clinical areas in relation to HIV testing
• Audit support for general practice, secondary care and specialist services to assist with the audit process, thereby helping to ensure that practice is in line with the NICE recommendations. This consists of audit criteria and data collection tool(s) and can be edited or adapted for local use
• Self assessment tools for services or local partnerships to establish how close their current practice is to that recommended in the guidance and to help with prioritising implementation activity
• Costing report which provides an overview of both the potential costs and savings from putting the NICE guidance into practice
• Costing template helps individual NHS organisations and local health economies to quickly assess any impact that the NICE guidance may have on local budgets
• Slide set for primary and secondary care featuring key recommendations for clinical practice: developed to support professionals in general practice and secondary care who are not specialists in HIV testing or treatment
• Clinical indicator diseases table (reproduced with kind permission from the British HIV Association) to accompany the above slide set
• Slide set for commissioning of specialist sexual health services developed for those involved in the commissioning or strategic planning of sexual health services, it provides an overview of all recommendations from both pieces of guidance.

The NICE tools and guidance are online via the following guidance pages:

• http://guidance.nice.org.uk/PH33
• http://guidance.nice.org.uk/PH34

On 17 November a large international Phase 2b study looking at interventions to reduce HIV sexual transmission announced that it will discontinue use of a 1% tenofovir vaginal gel and matched placebo gel due to the study’s data and safety monitoring board (DSMB) finding no difference in efficacy between these two groups. [1]

In the latest review the DSMB found a 6% HIV incidence rate among participants in both the tenofovir gel group and the placebo gel group. No other safety concerns (other than efficacy) have been reported with any of the studied interventions.

This is the second major change in the US NIH funded VOICE study (Vaginal and Oral Interventions to Control the Epidemic) in two months. In September, we reported in HTB that the use of daily oral tenofovir was discontinued for a similar lack of efficacy. [2]

The study originally enrolled more than 5,000 HIV-negative women at 15 clinical research sites in Uganda, South Africa and Zimbabwe. The study randomised women to one of five groups: daily oral tenofovir, daily oral Truvada, daily oral placebo tablet, daily tenofovir gel or daily placebo gel.

Only the daily oral Truvada and oral placebo arms will continue to be studied, with results expected in 2013.

References:

1. NHI press statement: NIH discontinues tenofovir vaginal gel in ‘VOICE’ HIV prevention study: product safe but no more effective than placebo. (25 November 2011).
   http://www.niaid.nih.gov/news/newsreleases/2011/Pages/VOICEdiscontinued.aspx
2. DSMB stops oral tenofovir monotherapy arm of VOICE PrEP study due to lack of difference compared to placebo. HIV Treatment Bulletin (HTB), October 2011.
   http://i-base.info/htb/15779

Further information:

Statement and Q&A from Microbicide Trials Network (MTN):
http://www.mtnstopshiv.org/node/3909

The number of people living with HIV in the UK reached an estimated 91,500 in 2010, with a quarter of those unaware of their infection, according to Health Protection Agency (HPA) figures published just ahead of World AIDS Day on 1 December.

The report also showed how in 2010, one in five people visiting an STI clinic did not accept an HIV test. This comes as the HPA calls for universal testing for HIV, so that no one leaves an STI clinic without knowing their HIV status.

The HPA is concerned that over half of people diagnosed in 2010 came forward for testing after the point at which treatment for their infection should ideally have begun. Late diagnosis is associated with an increased risk of AIDS and death. Among the 680 people with HIV who died in 2010, two thirds were people who had been diagnosed late. The HPA report recommends that in areas where prevalence of HIV is high, there should be universal testing for the infection in all new GP registrants and patients admitted to hospital so as to reduce late diagnosis.

The HPA’s annual ‘HIV in the UK’ report found 6,660 people were newly diagnosed with HIV in the UK. The report confirmed that infections probably acquired within the UK almost doubled in the last decade from 1,950 in 2001 to 3,640 in 2010 and exceed those acquired abroad – 3,020. This rise is mostly due to infections acquired among men who have sex with men, who remain the group most at risk of HIV infection in the UK.

In 2010, over 3,000 gay men were diagnosed with HIV – the highest ever annual number. One in 20 gay men are now infected with HIV nationally with one in 12 in London.

Dr Valerie Delpech, consultant epidemiologist and head of HIV surveillance at the HPA, said: “HIV is an infection which can nowadays be treated and those diagnosed promptly can expect to experience similar life expectancy as an individual without the infection. However, we are very concerned that a large number of people in the UK are unaware of their HIV status and are diagnosed late.

“We want to see increased access to HIV testing routinely offered in clinical settings such as new registrants at GPs and hospital general admissions, in areas of the country where rates of HIV infection are high. We are also urging sexual health clinics to ensure that HIV testing is offered as part of a universal sexual health screen at every new attendance.

“Research by the HPA has shown that routine and universal testing is feasible to undertake and acceptable to patients. Increased testing and greater access will help reduce the number of people who are unaware of their HIV status and increase the chances of early diagnosis, when treatment is more successful.”

Dr Delpech added: “Thanks to the development of anti-retroviral treatments and universal access to world class health care through the NHS, HIV is a manageable illness for the vast majority of people affected in this country. But an HIV diagnosis means a lifetime of medication and the costs of providing specialist HIV treatment and care are substantial and accelerating, so avoiding the infection altogether is essential for controlling the epidemic in the UK.

“If you are having sex, using condoms with any new or concurrent partners is the best way to prevent HIV. We encourage all people to take up the offer of an HIV test in whatever health care setting.”

Reference:

HPA press statement: HPA urges ‘universal testing’ for HIV as it is revealed more than 21,00 people are unaware they have the infection. (29 November 2011).
http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1317131678707x

Amidst the excitement about HPTN 052 at the Rome IAS meeting, the results of the ANRS Orange Farm circumcision programme received little publicity, despite stunning data.

Orange Farm was the site of the first of three randomised control trials that showed that circumcision reduces the risk of men contracting HIV in a predominantly heterosexual population. Following the trial, the researchers implemented a scaled up circumcision programme in Orange Farm. Bertran Auvert presented a late-breaker describing the results of this programme. [1]

There are several important findings from this study:

• Post-trial uptake was large. Orange Farm has now carried out approximately 25,000 circumcisions.
• No deaths or permanent injuries have occurred due to circumcision. There have been ten hospitalisations and in all these cases the adverse events were resolved.
• The benefit of circumcision on HIV incidence is durable.
• There was no evidence that incidence was affected by risk compensation.

Orange Farm is a township of about 110,000 adults about 45kms from Johannesburg. Since January 2008, free voluntary medical male circumcision to all boys and men older than 15 has been offered by the ANRS-sponsored project. The intervention includes community mobilisation and outreach, counselling, condom distribution, STI treatment, HIV voluntary counselling and testing and ART if eligible.

A baseline cross-sectional survey was done in 2007. This was a random sample of just under 1,200 males aged 15 to 49 years. The response rate was 74%. Male circumcision status was determined by genital examination. A second cross-sectional survey was done in 2010. It was almost the same size and the response rate was 88%. This survey included a background and sexual behaviour questionaire. Again male circumcision status was determined by genital examination. Blood samples were tested for HIV, ARVs and for recent infection (within 6 months) using a population incidence detuned HIV test (Calypte EIA BED).

Uptake

Male circumcision prevalence changed from 15.6% (95%CI: 13.6%-17.8%) of 15-49 year-olds in 2007 to 49.4% (95%CI: 46.5%-52.3%) in 2010. Using this data, the researchers calculated uptake, which increased across all age groups in the 2008-2010 period. In 15-49 year-olds it was 40% (95%CI: 38.0% to 43.5%) and 49.1% in 20 to 24 year-olds (95%CI: 42.1% to 52.4%). This substantial increase led Auvert to comment, “We are changing the social norms.”

In a comparison of 590 circumcised versus 605 uncircumcised men, circumcised men were younger, more educated, less likely to be married and more often aware of their HIV status. No difference in sexual behaviour was detected. For example reported condom usage was consistent (adjusted OR: 0.84; 95%CI: 0.63-1.1; p=0.26).

HIV prevalence and incidence

Among 586 uncircumcised men in the survey, 117 were HIV-positive (20%; 95%CI: 16.7%-23.2%). Among circumcised men, 36 out of 582 men were HIV-positive (6.2%; 95%CI: 4.3%-8.2%). This is a 55% reduction (95%CI: 39% to 70%).

In the 15-34 age group, the BED assay indicated that incidence in uncircumcised men was 3.7 per 100 person-years (95%CI: 2.2-6.1) and 0.6 per 100 person-years in circumcised men (0.19-1.9). The adjusted relative risk was 0.24 (95%CI: 0-0.66). Interestingly, this is equivalent to a 76% reduction that is exactly what the as-treated effect of the Orange Farm randomised control trial was.

Because of problems with the BED assay, a modelling exercise was also done in which HIV incidence was calculated from HIV prevalence data to determine the effect of circumcision on incidence. In this separate analysis the reduction in incidence was 83% (95%CI: 64%-98%) in 15-34 year-olds, consistent with the BED-based estimate.

It was estimated that without male circumcision, HIV prevalence would have been 25.1% higher in 15-49 year-olds in Orange Farm (95%CI: 13.1%-39.1%) and HIV incidence would have been 57.9% higher (95%CI: 17.0%-131%).

comment

The key limitation to a study like this is that it is observational. But randomised controlled trials have already proven the efficacy of circumcision. This was the first prospective study to show the benefits of circumcision in a real-world operational setting.

A widely expressed concern about circumcision is that risk compensation would undo much of its benefit. The finding that the operational effect of circumcision matched the as-treated effect of the Orange Farm clinical trial addresses this concern. The lack of difference in reported condom usage also indicates that risk compensation is not a factor, but this must be discounted against the fact that survey participants give answers that they believe are consistent with societal expectations rather than what they actually do.

There should be no further objections to scaling up voluntary medical male circumcision in appropriately equipped facilities. The South African Department of Health has committed to scaling up circumcision and implementation is taking place in several provinces. PEPFAR and the Gates Foundation have both committed to funding circumcision programmes across sub-Saharan Africa. However South African guidelines have still not been published, albeit that a draft exists. These guidelines need to be finalised and published. An implementation plan also needs to be devised.

The Orange Farm researchers hope soon to be able to do an analysis of the effect of medical male circumcision on incidence in women.

Reference:

Auvert B. 2011. Effect of the Orange Farm (South Africa) male circumcision roll-out (ANRS-12126) on the spread of HIV. 6th IAS Conference on HIV Pathogenesis, Treatment and Prevention. 17-20 July 2011, Rome, Italy.
http://pag.ias2011.org/Abstracts.aspx?SID=43&AID=4792

Thank you to Bertran Auvert, Dino Rech and Dirk Taljaard for assisting my understanding of this study.

Declaration of interest: Nathan Geffen am a member of the Orange Farm circumcision scientific committee.

On 28 September 2001, the Microbicides Trial Network (MTN), announced that following an interim review by the Data and Safety Monitoring Board (DSMB), the study would be unable to show a reduction in transmissions in patients using daily oral teneofovir and that this arm of the study would be stopped.

Previous studies have reported a strongly protective effect in both high-risk MSM (iPrEX study) and heterosexual populations (Partners in Prevention and TDF2 studys) with a negative result reported in heterosexual women (FEM-PrEP study). The Caprisa 004 study found a 43% protective effect of daily tenofovir gel.

The phase 2b VOICE (Vaginal and Oral Interventions to Control the Epidemic) study has enrolled more than 5,000 HIV-negative women at 15 clinical research sites in Uganda, South Africa and Zimbabwe.

The study randomised women to one of five groups: daily oral tenofovir, daily oral Truvada, daily oral placebo tablet, daily tenofovir gel or daily placebo gel.

The remaining four arms will continue to be studied, with results expected in 2013.

Information on the numbers of HIV infections that have occurred in any of the study arms will not be available until this time. Without this analysis it is impossible to know explain the current study results.

References:

MTN press release. MTN statement on decision to discontinue use of oral tenofovir tablets in VOICE, a major HIV prevention study in women. (28 September 2011):
http://www.mtnstopshiv.org/node/3619

Questions and Answers about the modification of VOICE study:
http://www.mtnstopshiv.org/node/3622

Summary of other PrEP studies:

http://www.avac.org/ht/d/sp/i/326/pid/326.

Simon Collins, HIV i-Base

Four of the six oral presentations in the ‘Treatment is prevention: the proof is here’ session reported on the results from HPTN 052. [1] This study had been unblinded four years earlier than planned due to a review by the data and safety monitoring board (DSMB), with all patients now being offered active treatment.

In summary, HIV-positive people on treatment had a 96% reduction in sexual transmission to their HIV-negative partners if they started ARVs with a CD4 count of 350-550 cells/mm3 compared to waiting until it dropped below 250 cells/mm3. As with all prevention studies, condoms, testing and intensive counselling was included throughout the study.

The main study results were presented by Myron Cohen from University of North Carolina. [2]

HPTN 052 screened over 10,000 couples in order to randomise 1763 HIV-positive people with CD4 counts 350-550 to either immediate or delayed HIV treatment (CD4 confirmed <250 or an AIDS-defining illness). Screening failure was mostly due to CD4 or other criteria in the positive partner, but 300 couples were already both HIV-positive. This was an international study predominantly recruiting in Africa (Botswana, Kenya, South Africa and Zimbabwe, n=954), Asia (India and Thailand, n=531) and Latin America (Brazil, n=276). Men and women were equally distributed as the positive partners. Median baseline CD4 count was 436 cells/mm3 (IQR 365-522) and viral load was approximately 25,000 copies/mL (IQR 6,000-80,000) respectively.

This was generally a low risk population with only 6-8% reporting recent unprotected sex and only 16% aged 18-25 years (~ 60% were 25-40 years and ~20% > 40 years).

The primary transmission endpoint was the prevention of virologically linked transmissions with a primary clinical endpoint of WHO Stage 4 events (including pulmonary TB, severe bacterial infections and death).

Transmission events (n=39) occurred significantly less frequently in the immediate (n=4) compared to the deferred (n=35) treatment arms, p<0.0001. Of these, only 28/39 were linked transmissions (within the couple) with 1 case in the immediate arm vs 27 cases in the deferred arm, p=0.001 (see below for details). Eleven transmissions were either unlinked or undetermined. This translated to incidence rates of linked transmission of 0.1 (95%CI 0.00-0.04) vs 1.7 (95%CI 1.1-2.5) per 100 person years respectively over a median follow-up of 1.7 years.

The single transmission in the immediate treatment arm was detected at the first follow-up visit. However viral diversification analysis estimated that transmission occurred prior to the positive partner initiating treatment (baseline 87,000 viral load) or certainly prior to viral suppression to <400 copies/mL which was recorded at day 28.

Other transmission risk factors were similar between arms, including rates of STIs (low at <5% in both index and partner at baseline and during the study), sexual activity (approximately 70%) and condom use (>90% by all throughout).

Viral suppression (<400 copies/mL) was maintained by >90% of participants in the immediate arm. There was a slow increase in this percentage over time in the deferred arm as people started treatment (from <10% over the first year, 20% by month 24 and increasing to 50% at month 45, though with much fewer patients). The median viral load closest to the time of transmission in the deferred arm was considerable at 80,000 copies/mL but had a wide range from 600 to 630,000 copies/mL.

In multivariate analysis, treatment was the strongest protective effect [HR=0.04, 95%CI 0.01-0.28] compared to condom use [HR=0.33; 95%CI 0.12-0.91]. Factors associated with increased transmission included baseline viral load [per log increment: HR 2.84, 95%CI 1.51-5.41] and baseline CD4 count [per 100 count increment: HR 1.24 95%CI 1.00-1.54].

The second presentation by Susan Eshelman from Johns Hopkins University School of Medicine focused on the analysis of linked transmission. [3] This included a helpful introduction to the three types of phylogenetic analyses used: phylogenetic analysis of HIV pol sequences using population sequencing, and statistical analysis of genetic distances from pol sequence pairs for the clearest cases (n=26), and phylogenetic analysis of env sequences obtained by deep sequencing for more complex cases (n=12). Together these provided a high level of reliability for indentifying whether the source of new infections was the HIV-positive partner or whether this was from another partner.

Transmissions in previous serodifferent couple studies have been from outside the main relationship in 25-50% cases.

The deep sequencing (‘ultradeep pyrosequencing’) supported linked two further cases and confirmed non-linkage for seven others (4 in the immediate and 3 in the deferred arm). Three cases remained unidentified (all in the deferred arm). Transmission linkage was not associated with index partner gender or CD4 count, geographical regions or time on study but this was strongly associated with study group and number of sexual partners in the three months prior to new seroconversions.

Results on the clinical outcomes for the HIV-positive participants in HPTN 052 were presented by Mina Hosseinipour from the UNC Project, Malawi. [4]

Results comparing the two groups were presented as ITT analyses and included the approximate 20% (184/877) people randomised to the deferred arm who started treatment during follow-up.

Over two years, median CD4 counts increased from 442 to 662 cells/mm3 in the immediate group compared to reducing from 428 to 390 cells/mm3 in the deferred arm. These differences are blunted as the deferred arm includes the response for the 20% people who started treatment. Viral suppression was achieved and maintained <400 copies/mL by >90% of the immediate arm. Less than 5% of patients on immediate treatment experienced virological failure during follow-up with most (60%) of these switching to a second-line combination.

The decision to start treatment in the deferred arm was driven by CD4 declines in 75% of cases. This occurred at a median count of 225 cells/mm3 (IQR 199–247), with 25% over people not starting until their CD4 count was less than 200. Treatment in both arms was predominantly AZT/3TC/efavirenz (70%) with ~10% using AZT/3TC/atazanavir, and ~10% using tenofovir/3TC/efavirenz. CD4 responses in the deferred arm were similar to absolute increase in the immediate treatment arm but remained significantly lower at all timepoints, reflecting the lower counts when starting treatment. Although there are fewer patients with longer duration of follow-up in the deferred arm, other studies have reported that baseline CD4 correlates with CD4 response after treatment.

The analysis by geographical region reported that about 80% of both the linked and unlinked transmission events occurred in African sites, likely a reflection of the higher background population prevalence rates in those countries, although the researchers highlighted higher rates of unprotected sex in the last week (by 9% vs 4% of African vs non-African) and higher sexual activity (>3 acts). However, baseline CD4 count, viral load and adjusted time to initiation, median adherence (99%) and treatment responses were similar between African and Asian sites.

Further details on clinical outcomes were presented by Beatriz Grinsztejn from the Oswaldo Cruz Foundation, Rio de Janeiro. [5]

Primary clinical events occurred at least once in 105 participants over 3304 person-years (PY) of follow-up; 40 in the immediate arm (2.4/100PY) and 65 in the delayed arm (4.0/100PY), hazard ratio (HR) 0.59, 95% CI: (0.40, 0.88), p=0.01. Seventeen people experienced more than one event. Time to event was significantly shorter in the deferred arm (HR 0.6, 95%CI 0.4, 0.9, p=0.01)

CD4 counts were significantly higher in the immediate arm vs deferred arms for all clinical endpoints (TB 518 vs 316; bacterial infection (mainly pneumonia) 551 vs 337 and death 476 vs 372 cells/mm3 respectively).

The between-arm difference was driven by extrapulmonary tuberculosis with 3 cases in the immediate versus 17 cases in deferred arms (p< 0.002). These were peripheral lymph nodes (2 vs 4), abdominal (0 vs 8), pleural (1 vs 3), skeletal (0 vs 1) and meningeal (0 vs 1). Isoniazid prophylaxis was only being used by 4% of patients in each arm at baseline.

Of the 23 deaths observed, there was no difference between arms: 10 in the immediate arm and 13 in the delayed arm [HR 0.77, 95% CI: (0.34, 1.76), NS p>0.5]. Causes of death were similar, but with 3 vs 3 suicides; 0 vs 2 accidents; and 3 vs 6 unknown).

Adverse events potentially related to ART were reported in 24% of subjects in the immediate arm and 5% in the delayed arm, but severe or life-threatening events occurred equally in 14% of each group and grade 4 lab events were also similar (in <1-2% of participants).

Since the DSMB recommendation in April 2011, all participants in the deferred arm have been offered HAART based on the strength of the study findings. This study continues to monitor all participants and results will add to clinical data from use of earlier vs later treatment in people with CD4 counts >350 cells/mm3.

comment

These results add to research that not only correlates viral load with risk of sexual transmission but specifically demonstrates a protective impact with treatment. The two cases of transmission in the early treatment arm (a second was discussed during the presentation) were both detected at the beginning of the study prior to the positive person reaching suppressed viraemia <400 copies/mL.

The fewer clinical endpoints from earlier treatment for the HIV-positive partners in this study are important but were driven by extrapulmonary TB. This clinical difference has significance for people in geographical regions where this study was run, but this aspect of the results was unexpected and has yet to be explained. A more generalisable benefit to people in Western countries is probably the reduced CD4 response in the deferred arm and this needs to be supported by longer follow-up. The ongoing START study will report on whether clinical benefits result from earlier treatment in Western countries.

It would be interesting to model the potential number of transmissions that have already been prevented over the last ten years from the seven million people globally on HAART. Given the financial constraints of access to treatment the additional impact on prevention should be included in future cost: benefit analysis.

The results from HPTN 052 clearly support offering an option for treatment to HIV-positive people who have HIV negative partners. This has been included in UK (BHIVA) guidelines for many years.

When access to treatment is limited with a waiting list using CD4 upper cut-offs to access treatment, those with the most severe medical should clearly be prioritised. However, the majority of the nine million people currently identified by UNAIDS and WHO analyses as requiring but not yet able to access treatment are likely to be undiagnosed. Broadening the CD4 criteria for access to treatment as prevention at higher CD4 counts is unlikely to directly deny access to treatment for more advanced patients.

It was unfortunate that a WHO guideline due to be launched at the IAS meeting, that included the recommendation for treatment people with CD4 counts higher than 350 and who have HIV-negative partners, based on the HPTN 052 study was withdrawn at the last minute. [6]

Although printed for a launch at the conference there is concern that while the scientific evidence is clear – and this should be the focus for clinical guidelines – practical issues on implementation have stalled their release perhaps under pressure from prominent WHO funders. It is difficult to understand how such a useful document that included broad community consultation and approval to the stage of print would have been retracted at such a late stage. WHO say this is due to a need to make “small modifications” and “to review their modeling data they used to inform investment structures”. The timeline for these changes are 2-3 months.

This plausibility for intervention from outside the extensive WHO guidelines writing and advisory panels is supported by an article in Science magazine that names the Gates Foundation specifically related to their interest in the latest PrEP results also being included. [7]

References

Unless stated otherwise, all references are the Programme and Abstracts of the 16th IAS Conference on HIV Pathogenesis, Treatment and Prevention, 17–20 July 2011, Rome.

1. Treatment is prevention: the proof is here. Oral abstract session: Monday 4.30-6.00pm.
2. Cohen M et al. Antiretroviral treatment to prevent the sexual transmission of HIV-1: results from the HPTN 052 multinational randomized controlled trial. Oral abstract MOAX0102. Webcast
3. Eshleman S et al. Analysis of genetic linkage of HIV from couples enrolled in the HIV Prevention Trials Network (HPTN) 052 trial. Oral abstract MOAX0103.
4. Hosseinipour M et al. Immunologic and virologic disease progression and responses to ART across geographic regions: outcomes from HPTN 052 study. Oral abstract MOAX0104. Webcast
5. Grinsztejn B et al. Effects of early versus delayed initiation of antiretroviral therapy (ART) on HIV clinical outcomes: results from the HPTN 052 randomized clinical trial. Oral abstract MOAX0105. Webcast.
6. WHO. Couples HIV testing and counselling and antiretroviral therapy for treatment and prevention in serodiscordant couples: Recommendations for a public health approach. 2011. Final version approved but not yet released. (PDF file)
7. Cohen J. New prevention data leads WHO to delay guidelines for couples. Science Insider (25 July 2011).

Simon Collins, HIV i-Base

Results from the double-blind placebo-controlled TDF2 study presented in an oral presentation in Rome provided additional supportive data for the benefit of daily oral tenofovir/FTC (Truvada) to reduce sexual heterosexual transmission. [1]

While the iPrEX study first reported a strongly protective impact in high risk MSM, the lack of protection in the FemPrEP study earlier this year has still to be explained. [2, 3]

TDF2 randomised 1200 sexually active HIV-negative adults (age 18-49: approximately 90% were between 21-29 years) and followed them for a year. Over 90% of participants were single with only 3% having low educations (primary or less) with >70% having secondary and >20% having post-secondary education. HIV testing was monthly and as with all prevention studies, intensive counselling on safer sex and free condom distribution was provided throughout the study. An indication of the background risk in this population is that 16% of people failing screening (197/2533) were excluded due to already being HIV-positive and 20% due to not being sexually active.

A slightly higher percentage of people in the active vs placebo arm (34% vs 31%) did not complete the study due to loss to follow-up, withdrawal of consent, relocations or other reason. The study had a good gender balance with 45% women.

With 33 seroconversions, primary efficacy results reported a 63% reduced risk of transmission with Truvada based on 9 new infections in the active arm compared to 24 in placebo group (difference 62%: 95%CI 21.5 to 83.4, p=0.0133).

When restricting the analysis (post hoc?) to infections within 4 weeks of a study visit (ie where the monthly visit schedule was being followed and the participant was under a prescription period) the association became stronger. Out of 23 seroconversions, 4 occurred in the active arm and 19 in the placebo group with 78% protection efficacy (95% CI 41.2 to 93.6, p=0.0053).

Although it was emphasised that the study was underpowered to draw any conclusion by gender, in an ITT analysis (33 cases) the intervention appeared protective in men (p=0.026) but not women (p=0.107) and in the observed results (23 cases) the protection was seen on women (p=0.021) but not men (p=0.065). Whilst interesting to see if a gender effect can shed light on the results from FemPREP, this will need to come from larger study numbers.

Resistance developed in one person enrolled in the active arm whose acute HIV infection was undiagnosed with K65R, M184V and A62V conferring nucleoside cross resistance. The person has achieved viral suppression after starting treatment with AZT/3TC/lopinavir/ritonavir. One person in the placebo group had low-level K65R suggesting an infection with drug resistant HIV.

Side effects were commonly reported in both arms, usually mild, with nausea (19% vs 7%, p=0.0001) and vomiting (11% vs 7%, p=0.005) occurring more significantly in the active arm compared to the placebo arm, but resolving within the first month. There were no differences in laboratory abnormalities with one case of elevated creatinine in the active group that resolved when treatment was stopped.

References

1. Thigpen MC et al. Daily oral antiretroviral use for the prevention of HIV infection in heterosexually active young adults in Botswana: results from the TDF2 study. Oral abstract WELBC01. Webcast.
2. Grant RM et al. Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. NEJM. 23 November 2010 (10.1056/NEJMoa1011205). Free full access.
3. FHI statement on the FEM-PrEP HIV prevention study: FHI to initiate orderly closure of FEM-PrEP. (18 April 2011).

Simon Collins, HIV i-Base

The final presentation in the Treatment is Prevention session was a summary of the first results from the Partners PrEP study that randomised the HIV-negative partner in 4758 HIV serodifferent heterosexual couples to daily tenofovir (TDF) vs tenofovir/FTC (TVD) vs placebo in a 1:1:1 ratio. [1]

The results presented were based on a DSMB analysis a week before the conference that recommended unblinding the placebo arm and switching those participants to active drugs. This was based on significantly reduced risks of transmission in both the active arms and was 18 months earlier than the planned study endpoint.

This study was run in nine sites in Kenya and Uganda with all participants receiving intensive healthcare and adherence counselling including free condoms. The negative partners were seen monthly for counselling with HIV and pregnancy testing and the positive partners were monitored for their HIV care every three months.

Baseline demographics were similar across the three arms and included age (of the negative partner) 33 years (IQR 28-40), with the positive partner diagnosed a median of 0.4 years (IQR 0.1-2.0 years), CD4 count 490 cells/mm3 (IQR 370-660) and viral load 3.9 log copies/mL (3.2-4.5 logs).

Nearly all couples were married (98%) with duration of relationship a median of 7 years (IQR 3-14). The positive partner was a woman in 40% of couples. Approximately 20% of positive partners started treatment during the study for their own health.

Study retention was high with fewer than 5% discontinuations over 7337 person years of follow up (median 12 months). Adherence was also estimated high at 97% based on pill count using returned bottles (98% of bottles were returned).

Up to May 2011, there were 90 new infections, 12 of which were HIV-positive at randomisation (3 TDF, 3 TVD, 6 placebo). Of the 78 transmissions that occurred as events for the primary endpoint, 18, 14 and 47 occurred in the TDF, TVD and placebo arms respectively. The was an incidence of 0.74, 0.53 and 1.92 per 100 patient years that produced protection rates of 62% (95%CI 34-78%, p=0.0003) in the tenofovir and 73% (95%CI 49-85%, p<0.0001) in the tenofovir/FTC arms compared to placebo.

The study reported of a similar response between the two active arms (p=0.18 for comparison, NS). However, protection was numerically greater with the dual therapy and the gender analysis reported wider confidence intervals for tenofovir monotherapy with lower levels that were lower.

For women, protection rates were 68% (29-85%) and 62% (19%-82%) in the TDF vs TVD arms; for men these were 55% (4-79%) vs 83% (49-94%). The plausibility for greater protection from dual therapy would be extended with either lower adherence or less-than-daily dosing, both of which might be key public health factors for considering use of PrEP outside of clinical trials.

Safety results were very similar between all three arms for serious events and lab abnormalities including creatinine increases (1%, mainly grade 1) and reduced phosphorus (9%, equal across arms). As with other PrEP studies, nausea and diarrhoea were significantly more common in the active arms, but generally only for the first month of treatment.

As with other PrEP research, results from the pharmacokinetic will be important to correlate drug levels with level of protection and partner viral load with risk of infection. Resistance results will also be analysed.

Reference

Baeten J et al. Antiretroviral Pre-Exposure Prophylaxis for HIV-1 prevention among heterosexual African men and women: the Partners PrEP Study. Oral abstract MOAX0106. Webcast.

Initiation of Antiretroviral Treatment Protects Uninfected Sexual Partners from HIV Infection (HPTN Study 052): 96% reduction in HIV transmission, according to study conducted by HIV Prevention Trials Network

Men and women infected with HIV reduced the risk of transmitting the virus to their sexual partners through initiation of oral antiretroviral therapy (ART), according to findings from a large multinational clinical study conducted by the HIV Prevention Trials Network (HPTN), a global partnership dedicated to reducing the transmission of HIV through cutting-edge biomedical, behavioral, and structural interventions.

The study, known as HPTN 052, was designed to evaluate whether immediate versus delayed use of ART by HIV-infected individuals would reduce transmission of HIV to their HIV-uninfected partners and potentially benefit the HIV-infected individual as well. Findings from the study were reviewed by an independent Data and Safety Monitoring Board (DSMB).The DSMB recommended that the results be released as soon as possible and that the findings be shared with study participants and investigators. The DSMB concluded that initiation of ART by HIV-infected individuals substantially protected their HIV- uninfected sexual partners from acquiring HIV infection, with a 96 percent reduction in risk of HIV transmission. HPTN 052 is the first randomised clinical trial to show that treating an HIV-infected individual with ART can reduce the risk of sexual transmission of HIV to an uninfected partner.

HPTN 052 began in April 2005 and enrolled 1,763 HIV-serodiscordant couples (couples that have one member who is HIV-infected and the other who is HIV-uninfected), the vast majority of which (97 percent) were heterosexual. The study was conducted at 13 sites across Africa, Asia and the Americas. The HIV-infected person was required to have a CD4 cell count between 350-550 per cubic millimeter (cells/mm3) at enrollment, and therefore did not require HIV treatment for his or her own health. Couples were randomized to one of two groups. In one group, the HIV-infected person immediately began taking ART (immediate ART group). In the other group, the HIV-infected person began ART when his or her CD4 cell count fell below 250 cells/mm3 or if he/she developed an AIDS-related illness (the delayed ART group).

Throughout the study, both groups received HIV-related care that included counseling on safe sex practices, free condoms, treatment for sexually transmitted infections, regular HIV testing, and frequent evaluation and treatment for any complications related to HIV infection. Each group received the same amount of care and counseling. Any HIV-uninfected person who became HIV-infected during the course of the study was referred to local services for appropriate medical care and treatment.

In its review, the DSMB found a total of 39 cases of HIV infection among the previously uninfected partners. Of those, 28 were linked through genetic analysis to the HIV-infected partner as the source of infection. Seven infections were not linked to the HIV-infected partner, and four infections are still undergoing analysis. Of the 28 linked infections, 27 infections occurred among the 877 couples in which the HIV-infected partner did not begin antiretroviral therapy immediately. Only one case of HIV infection occurred among those couples where the HIV-infected partner began immediate antiretroviral therapy. This finding was statistically significant and means that earlier initiation of antiretrovirals led to a 96 percent reduction in HIV transmission to the HIV-uninfected partner. The infections were confirmed by genetic analysis of viruses from both partners.

Additionally, 17 cases of extrapulmonary tuberculosis occurred in the HIV-infected partners in the deferred treatment arm compared with three cases in the immediate treatment arm, a statistically significant difference. There were also 23 deaths during the study. Ten occurred in the immediate treatment group and 13 in the deferred treatment group, a difference that did not reach statistical significance.

The press release noted that the ongoing international clinical study called Strategic Timing of Antiretroviral Therapy (START) also funded by NIAID is examining the optimal time for asymptomatic HIV-infected individuals to begin antiretrovirals.

http://www.niaid.nih.gov/news/newsreleases/2011/Pages/START.aspx

Source: NIAID Press release. (12 May 2011)

For additional information about the HPTN 052 study, see the Questions and Answers information on the NIAID website.

http://www.niaid.nih.gov/news/QA/Pages/HPTN052qa.aspx

The phrase “product pipeline” typically conjures up the notion of multiple experimental candidates incrementally advancing along a pre-plumbed path toward licensure and widespread availability. But for most of the approaches described in this section of the report, the route toward a pharmacy shelf is far more convoluted and uncertain. Few large pharmaceutical companies are involved in the development of the candidates listed here; the majority are collaborative efforts between small biotech firms, academic researchers, non-profits, and government funders. And even those with the support of a major manufacturer can face unique obstacles related to their novelty, because there are as yet no approved precedents in any of these realms.

The current state of the biomedical prevention pipeline offers illustrative examples. After decades of disappointment and frustration, the past few years have seen low but statistically significant efficacy reported for each of the main approaches: vaccines, microbicides and, most recently, pre-exposure prophylaxis (PrEP). The vaccine trial, named RV144, involved an ALVAC canarypox vector made by Sanofi-Pasteur combined with an envelope protein booster shot, AIDSVAX. While Sanofi-Pasteur remains committed to following up on the marginal degree of protection (31%) observed among recipients of the regimen (Rerks-Ngarm 2009), the company that made AIDSVAX, VaxGen, ceased to exist several years ago after the product failed to show efficacy given alone. Attempts to duplicate and improve upon the results have thus been slowed by the need to secure a new manufacturer for the envelope protein boost.

Greater success was reported last year with a microbicide consisting of a gel form of the antiretroviral drug tenofovir (Viread), which demonstrated 39% protective efficacy in the CAPRISA 004 trial in South Africa (Abdool Karim 2010). However, the next steps toward licensure have proven surprisingly slippery. The US Food and Drug Administration (FDA) has indicated that at least one more confirmatory trial (in addition to an ongoing study called VOICE) will be sufficient for them to consider the product for approval, but securing the relatively small amount of funding necessary for the new efficacy evaluation proved difficult and time-consuming. The trial, FACTS 001, is now expected to get underway in August 2011. The maker of Viread, Gilead Sciences, has licensed the gel form to the non-profit organization CONRAD, so the development of the microbicide also represents a test case for the viability of non-profit manufacturing and marketing.

Among the most significant biomedical prevention news since the last TAG pipeline report in 2010 was the announcement of the long-awaited first efficacy results of PrEP in HIV negative gay men and transsexual women at high risk of infection (Grant 2010). The iPrEx study found that individuals assigned to receive Truvada (a pill combining two antiretroviral drugs, tenofovir and emtricitabine) experienced a 44% reduction in risk of HIV infection, with additional analyses indicating that protection was significantly better among participants who closely adhered to the regimen. While Gilead donated Truvada for this and other PrEP studies, it was not otherwise involved and it was unclear whether the company would pursue a prevention indication for the drug. After the iPrEx findings were announced, Gilead expressed its intent to submit the data to FDA for consideration, which provoked a vociferous and at times acrimonious debate regarding whether such a filing would be appropriate or premature. Subsequently, the picture was further complicated when news emerged that a trial of Truvada as PrEP in women was being stopped after an interim analysis found it would be unable to show efficacy. A broad lesson from all these biomedical prevention developments is that an approach can get tantalising close to the end of the pipeline, yet still face significant impediments to actually emerging from it.

Immune-based therapies (IBTs) and gene therapies for HIV have long been entrenched in a distant corner of the research field. This is partly due to uncertainties about mechanisms of action and how best to define and measure success, particularly in light of the dramatically beneficial effects of HIV suppression with antiretroviral drugs. But resurgent interest in curing HIV infection is now helping to move these types of approaches toward the mainstream. In particular, the widely reported case of Timothy Brown, who has remained off antiretroviral therapy and free of detectable HIV for four years and counting after a complex series of high-risk treatments for cancer – including stem cell transplants from a donor lacking the CCR5 receptor – is viewed as a compelling proof of concept that a cure for chronic HIV infection is possible (Allers 2011). The goals for potentially curative therapies are relatively straightforward: either eradicate HIV completely (to the extent that this can be verified with current testing technologies) or induce long-term control of the virus in the absence of ongoing treatment (referred to as a functional cure). In addition to IBTs and gene therapies, cure research includes treatments – most notably histone deacetylase (HDAC) inhibitors – that aim to awaken the latent HIV that otherwise can persist for life in dormant form, integrated into the host cell’s DNA, invisible to the immune system, yet subject to reactivation by immune stimuli or to renewed replication when the resting infected cell divides.

Another potential role for IBTs and gene therapies is addressing the immune system dysfunction that can persist in some individuals despite HIV suppression. Examples include inadequate CD4 T cell recovery, elevated levels of immune activation and inflammation, and an accelerated aging of the immune system called immunosenescence. Studies have linked all of these phenomena to an increased risk of ill health (Marin 2009; Tan 2008; Tien 2010; Deeks 2011), suggesting that an IBT and/or gene therapy capable of addressing them could conceivably offer clinical benefits.

Table 1. HIV vaccines pipeline 2011

Spurred by the borderline but statistically significant protection observed in the RV144 trial of ALVAC/AIDSVAX, HIV vaccine research continues to move ahead on multiple fronts.

Identifying correlates of protection in RV144

Many scientists are engaged in the search for immunological markers that might have been linked to protection against HIV in the RV144 trial. Identification of such “correlates of protection” is one of the Holy Grails of vaccine research and currently, according to Jerome Kim from the US HIV Military HIV Research Programme, 35 investigators from 20 institutions are working on 32 different assays that could potentially be used to analyze RV144 samples (Kim 2011). Data from this work should start to become available toward the end of 2011. In the meantime, Kim and colleagues have unveiled some of their results hinting that CD4 T cells targeting the V2 region of the HIV envelope could have played a role in the trial outcome (Currier 2011).

Replicating and extending the RV144 results

While the vaccine field has been buoyed by RV144, there remains a deflating possibility that the observed evidence of protection was not a consequence of immunization, but simply a result of chance. A recently published statistical reevaluation of the efficacy result argues there is a 22% or greater probability it was spurious, which the authors note is “an inference that reflects greater uncertainty than has much of the discussion about this trial” (Gilbert 2011).This uncertainty emphasises the importance of efforts to try and replicate and extend the RV144 findings.

The HIV Vaccine Trials Network (HVTN) has published plans for adaptive trial designs (Corey 2011) which will be used to rapidly evaluate a variety of prime-boost vaccine regimens in the high prevalence setting of South Africa. The US HIV Military Research Programme is also planning a new efficacy trial in men who have sex with men (MSM) in Thailand, using the same or a similar regimen to RV144 but with an additional booster immunization at the 12 month time point (the last shot in RV144 was at six months). This trial is slated to begin in 2014 (Kim 2011).

There is only one ongoing HIV vaccine efficacy trial, HVTN 505. It involves a prime-boost regimen comprising a DNA vaccine followed by an adenovirus serotype 5 (Ad5) vector.The target population is circumcised MSM and male-to-female (MTF) transgender persons who have sex with men. The design of the trial has gone through myriad iterations, and until recently the primary goal was to look at whether the vaccines reduced viral load in recipients who subsequently acquired HIV. In light of the RV144 results, consideration is now being given to expanding HVTN 505 in size so that the effect of vaccination on risk of HIV acquisition can also be evaluated.

Developing new vectors, immunogens and adjuvants

As the term implies, vectors are delivery vehicles – often weakened forms of viruses – that carry vaccine ingredients into the body. Immunogens are the ingredients derived from HIV that the vaccine aims to induce immune responses against, and adjuvants are substances designed to enhance the magnitude and/or quality of those immune responses. The HIV vaccine pipeline contains a variety of vector/immunogen/adjuvant combinations, most commonly administered in prime-boost regimens. New vectors in human trials in 2011 include measles virus, vesicular stomatitis virus (VSV), and a chimpanzee adenovirus (Lorin 2004; Cooper 2008; Rosario 2010). Also in the mix are vaccines that deliver proteins or protein fragments directly, similar to the AIDSVAX envelope protein vaccine used as a booster shot in the RV144 trial.

A novel HIV vaccine vector that has received widespread media coverage due to promising results in macaques is cytomegalovirus (CMV). The vector is under development by the Vaccine and Gene Therapy Institute (VGTI) in collaboration with the International AIDS Vaccine Initiative (IAVI), but has not yet entered human testing. In a study published in the journal Nature, the use of CMV as an SIV vaccine vector led to an unprecedented degree of immunological control of a highly pathogenic challenge virus, SIVmac251 (Hansen 2011). Although large swathes of the human population are already infected with CMV, pre-existing immunity to the vector is not considered an issue because the virus has evolved immune evasion mechanisms that allow it to re-infect (Hansen 2010). There is, however, an important caveat about the use of CMV that was conspicuously absent from press reports about this study; over the last couple of decades, evidence has accumulated that CMV infection has an array of pernicious long-term effects on human health, contributing to cardiovascular disease (Stassen 2006), earlier mortality (Simanek 2011), and a type of immune system damage called immunosenescence that is associated with morbidity and mortality as people reach old age (Pawelec 2011). Although researchers are attempting to render CMV vectors safe for human use, it is currently unclear if – and how – safety can be sufficiently demonstrated to allow clinical trials.

New approaches to immunogen design attempt to improve the ability of vaccines to induce immune responses against a broad array of HIV targets. Oxford University and Tomas Hanke are testing HIVconsv, an immunogen incorporating fourteen parts of HIV that are highly conserved among multiple different clades (Létourneau 2007). Mosaic HIV immunogens represent another approach with the same goal; human testing is anticipated to start within the next year (Corey 2010).

Adjuvants that have ambled into clinical trials since the last TAG pipeline report include heat shock protein 70 (Hsp70), a naturally occurring protein under study as an enhancer of mucosal immune responses (Lehner 2004), and the cumbersomely-named cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF for short), which the company GeoVax is investigating as an adjuvant for its DNA/MVA vaccine after obtaining promising results in macaques (Lai 2011).

The multitude of candidates in the HIV vaccine pipeline prompts the question of how products will be selected for advancement into efficacy trials. At one time, the major criteria were the nature and magnitude of the anti-HIV immune responses invoked by the vaccines in early studies, along with evidence from pre-clinical research in the SIV/macaque model. However, one of the implications of the RV144 trial is that current immune response assays and animal models may not necessarily predict protective efficacy in humans (the ALVAC/ AIDSVAX combination performed dismally by both criteria). It has also become clear that ostensibly similar regimens can induce immune responses that differ substantially in quality, with unclear implications for their effectiveness (Pillai 2011). The uncertainty regarding predictors of success is an additional motivation behind HVTN’s adaptive efficacy trial design proposal, which allows for multiple parallel trials of different vaccine approaches with pre-planned interim analyses for the purpose of both rapidly discarding ineffective candidates and quickly identifying and advancing those showing promise (Corey 2011).

Inducing neutralising antibodies

Scientists continue to wrestle with the spiky problem of inducing antibodies that can effectively inhibit HIV. As described in last year’s report, several new broadly neutralising antibodies have been isolated from HIV positive individuals and their structures and targets are now being characterised in detail (Davenport 2011; Pancera 2010; Pejchal 2010; Zhou 2010). There has also been potentially significant progress in understanding how these rare antibodies are generated by the immune system. The production of antibodies by B cells involves a complex process called somatic hypermutation. Essentially, a B cell that is stimulated to make antibodies undergoes several rounds of division during which the genetic code for producing the antibody is shuffled each time, leading to alterations in the antibody structure. If the B cell’s genetic mutations produce an antibody with an improved ability to glom onto its target, the cell is selected to undergo more rounds of division. Repeated cycles of this mutation and selection process (referred to as “affinity maturation”) lead to the generation of antibodies with a high affinity for their targets. Typically, affinity maturation takes an average of around 10-15 mutations. Remarkably, the broadly neutralising antibodies against HIV that have been identified show evidence of a more arduous affinity maturation process involving more than 60 mutations. The next step for vaccine researchers is to figure out whether this complex pathway can be recapitulated with a vaccine, leading to the generation of similarly effective antibodies. Signs so far are encouraging, but considerable work remains (Kwong 2011).

Table 2. PrEP and Microbicides Pipeline 2011

Preexposure prophylaxis

Preexposure prophylaxis (PrEP) is the prophylactic use of antiretroviral drugs to prevent HIV infection. In late 2010, the long-awaited first human PrEP efficacy results were announced and published in the New England Journal of Medicine (Grant 2010). The trial, named iPrEx, recruited 2,470 MSM and 29 transgender women at high risk of HIV infection, assigning them to receive daily Truvada (a combination pill containing the antiretrovirals tenofovir and emtrictabine) or placebo. Trial sites were located in Brazil, Ecuador,Peru,South Africa,Thailand,and the United States.Over an average of 1.2 years of follow up, the risk of acquiring HIV infection was reduced by 43.8% among participants in the Truvada arm compared to the placebo arm, a highly statistically significant result. There were a total of 36 infections in Truvada recipients compared to 64 in those on placebo. Additional follow up from May through August 2010 was reported in February of this year: the number of HIV infection endpoints increased to 48 vs. 83 for a final efficacy estimate of 42% (with a 95% confidence interval of 18-60%) (Grant 2011). Importantly, there was a strong correlation between adherence to the PrEP regimen and protection; a subset analysis of the Truvada arm comparing individuals with detectable drug levels to those without found that the presence of drug was associated with a greater than 90% reduction in HIV acquisition risk. However, this analysis also revealed that drug levels were undetectable in around half the participants assigned to Truvada, providing an indication that adhering to daily PrEP was problematic for a large proportion of the trial population.

In terms of tolerability, relatively few side effects were reported. Only nausea and unintentional weight loss of 5% or more were reported more frequently in the Truvada arm compared to placebo (in both cases, these side effects were noted by around 2% of Truvada recipients vs. 1% placebo). There were a total of five confirmed cases of elevated creatinine, a potential marker for kidney toxicity, all in the Truvada group. Four out of five of these individuals stopped and then restarted the drug without a recurrence of the problem. No other abnormal laboratory values were reported. No cases of drug resistance were observed in the participants who became HIV infected during the trial. However, there were three instances of resistance to emtrictabine documented among 10 people who were found to have had undetected, pre-seroconversion HIV infection at the time of study enrollment.

The iPrEx research team, led by Robert Grant at UCSF, now has funding from NIAID to conduct an open label evaluation (dubbed iPrEx OLÉ) of Truvada as PrEP; all participants from the original randomised trial are being invited to participate. The goals for the study are to assess whether knowledge regarding Truvada’s efficacy has any effect on adherence and/or sex practices, and also to gather more safety data over a longer period of follow up.

The iPrEx data has generated considerable excitement in the PrEP field, but results are pending from trials being conducted in other populations. In a sobering development announced earlier this year, a trial of Truvada as PrEP at sites in Kenya, Malawi, South Africa, and Tanzania (the FEM-PrEP trial, sponsored by Family Health International) was stopped midstream after a review by the Data and Safety Monitoring Board (DSMB) found that it would not be able to show efficacy even if carried to completion.The DSMB decision was based on the observation that 56 HIV infections had occurred, evenly divided between the placebo and Truvada arms. The explanation for the FEM-PrEP outcome is as yet unclear.

The US Centers for Disease Control and Prevention (CDC) is sponsoring two ongoing PrEP efficacy trials: one is evaluating tenofovir (Viread) compared to placebo in 2,400 injection drug users in Thailand, the other is looking at Truvada in a population of 2,000 heterosexual men and women in Botswana. The University of Washington is comparing tenofovir to Truvada as PrEP in a trial involving 3,900 serodiscordant couples in Kenya and Uganda. The Microbicide Trial Network’s VOICE study has successfully completed enrolment of 5,000 African women and will compare three strategies: oral PrEP using tenofovir or Truvada and a tenofovir-containing vaginal microbicide gel. A recent DSMB review of VOICE gave it the green light to continue; follow up is due to end in June 2012 with results becoming available in early 2013.

The evidence from iPrEx regarding the difficulty of adhering to daily PrEP has renewed interest in intermittent dosing strategies. The HIV Prevention Trials Network (HPTN) is launching the “ADAPT” study (Alternate Dosing to Augment PrEP Tablet-taking, also known as HPTN 067) which plans to compare different Truvada dosing schemes in 180 MSM and 180 heterosexual women at high-risk of acquiring HIV infection. The trial is not of sufficient size to evaluate efficacy but will compare tolerance, acceptability and drug levels.

Since the 2010 TAG pipeline report two novel PrEP agents have entered phase I trials:

• TMC278LA is a long-acting, injectable formulation of the approved antiretroviral drug rilpivirine that is being studied at four sites in the UK under the sponsorship of the St Stephens Aids Trust.
• Ibalizumab is a monoclonal antibody delivered via intermittent injection; it interferes with the interaction between HIV and the CD4 molecule, thereby inhibiting infection. Studies in people with HIV have documented significant viral load reductions (Bruno 2010). The phase I trial of ibalizumab as PrEP is unusual in that it is recruiting HIV negative volunteers at risk for HIV infection; normally, early-phase studies are restricted to participants with low or no risk of exposure to the virus.

Microbicides

Microbicides are substances that aim to prevent HIV infection via application to the vagina or rectum prior to (and in some cases also after) sex. Last year witnessed the first major microbicide breakthrough with the announcement of the results of CAPRISA 004, a phase IIb trial of tenofovir gel conducted in South Africa (Abdool Karim 2010). Women randomised to receive the gel had a statistically significant 39% reduction in risk of acquiring HIV infection. In raw numbers, there were 38 infections in the group of 445 tenofovir gel recipients and 60 among the 444 placebo recipients over an average of 18 months of follow up. The product was well tolerated and there was a strong association between drug levels in cervicovaginal fluid and protection from HIV (Kashuba 2010), echoing the findings from iPrEx and adding to the plausibility of the result.

Unexpectedly, CAPRISA 004 also showed that tenofovir gel offers significant protection against HSV-2 infection. Risk of acquiring HSV-2 was reduced by 51% (95% confidence interval: 30-78%) among women assigned to the active gel arm.This impressive finding suggests that tenofovir gel could have a dual impact on susceptibility to HIV, because HSV-2 infection is associated with an approximately 3-fold increase in relative risk of HIV acquisition in women (Freeman 2006).Tenofovir only inhibits HSV-2 at very high concentrations that cannot be achieved with oral dosing, but pharmacologist Angela Kashuba has shown that the gel form can reach sufficient levels in the genital tract (Kashuba 2010).

Since the initial presentation of the CAPRISA 004 results at the International AIDS Conference in Vienna in July 2010, the US Food and Drug Administration (FDA) has indicated that two additional confirmatory trials would provide sufficient data for the agency to consider the product for licensure. One trial, VOICE (described in the previous section), is ongoing. A second, called FACTS 001, has taken longer to secure funding than was anticipated, but is now expected to begin in South Africa in August 2011. The fate of a third tenofovir gel efficacy trial planned by the UK’s Microbicide Development Programme, MPD 302, is less certain.

Gilead Sciences has licensed the rights to produce tenofovir gel to the non-profit organization CONRAD, which is exploring options for manufacturing and marketing globally. CONRAD has recently announced that the South African government’s Technology Innovation Agency (TIA) will be granted the rights to manufacture and distribute tenofovir gel in Africa. TIA has, in turn, set up a joint venture called ProPreven consisting of TIA, Cipla Medpro and iThemba Pharmaceuticals. ProPreven will handle the registration, manufacturing and marketing of the gel if and when the data accrue to support licensure. A recent modeling study based on the results of CAPRISA 004 concluded that, over a twenty year period, the use of tenofovir gel in South Africa could avert up to two million new HIV infections and a million AIDS deaths (Williams 2011).

The next microbicide product that appears likely to undergo efficacy testing is a gel form of the nonnucleoside reverse transcriptase inhibitor drug dapirivine, which is being developed by the International Partnership for Microbicides (IPM). Phase I/II trials have shown that dapirivine gel can be safely delivered via a matrix intravaginal ring (Nel 2009), and IPM has ambitious plans to conduct two phase III efficacy trials of the approach involving a total of 6,000 women.

Table 3. Research toward a cure

Not so long ago, prospects for an HIV cure were deemed so dim that even mentioning the word was generally frowned upon, lest it create false hopes. But it is important to appreciate that this semantic reticence did not equate to an absence of research; most of the trials and approaches included in the table above were in development long before the breakthrough case of Timothy Brown was reported. What Brown’s experience has done, however, is provide invaluable momentum for the research effort while at the same time bringing the possibility of a cure into the public consciousness. The elevated profile of the field has also spurred a flurry of review articles and opinion pieces in the scientific literature, delineating the challenges that lie ahead (Deeks 2010; Lafeuillade 2011; Lewin 2011a; Lewin 2011b; Margolis 2011; Siliciano 2010).

While the term “cure research” is now increasingly invoked, it is not well defined. In terms of human trials, current strategies can be divided into three broad categories:

• Cell-protecting: approaches designed to protect potential target cells from HIV infection, e.g. via gene therapy.
• Reservoir-depleting: approaches that aim to reduce the amount of residual HIV that persists after viral replication is suppressed by ART.
• Immune-enhancing: approaches to bolster the immune response to HIV in hopes of enabling the body to control or even gradually eliminate residual viral reservoirs.

Sangamo Biosciences is pursuing a cell-protecting strategy based on a proprietary technology that allows targeting of specific genes. By pairing zinc finger proteins with enzymes called nucleases that can break up DNA, Sangamo’s approach disrupts the CCR5 gene and thus prevents expression of the CCR5 co-receptor on modified cells (Urnov 2010). In current trials, CD4 T cells are extracted from participants via apheresis, subjected to the zinc finger nuclease procedure in the laboratory, and then expanded in number and re-infused. Presentation of preliminary phase I results early in 2011 generated considerable excitement because the researchers were able to document significant CD4 T cell count increases and persistence of CCR5-deleted CD4 T cells at low but detectable levels in peripheral blood (Lalezari 2011). In a small subset of participants who underwent sampling from the gastrointestinal tract there was evidence that the majority of CD4 T cells in their gut were CCR5-deleted, suggesting that the modified cells had a particular survival advantage in this location, which is known to be a major site of HIV replication (Tebas 2011). Further results from these trials are eagerly anticipated. Unlike many cash-strapped biotech companies, Sangamo is better positioned to move its candidate HIV therapy through the pipeline due to a robust revenue stream obtained from licensing their gene modification technology for laboratory and agricultural use. Researchers are also collaborating with Sangamo to study the effects of CCR5-deleted stem cells in individuals with HIV who require stem cell transplants for AIDS-related lymphoma; the trial is not yet open for enrollment but is slated to take place at the City of Hope in Los Angeles (Cannon 2011).

While Sangamo ultimately has marketing ambitions for its gene therapy, the other examples of cure-related trials are more exploratory in nature. Laboratory experiments indicate that a class of anticancer drugs called HDAC inhibitors can activate the otherwise silent latent HIV reservoir and one such drug – vorinostat (SAHA) – is now being studied for this purpose in both the US and Australia (the principal investigators are David Margolis at the University of North Carolina and Sharon Lewin at Monash University, respectively). The downside of HDAC inhibitors is a daunting toxicity profile that has led these trials to proceed with extreme caution. The goal is not to develop vorinostat but rather to find out if HDAC inhibition can have measurable effects on the HIV reservoir in humans; a positive outcome would justify investment in the development of safer candidates with similar mechanisms of action. Two large pharmaceutical companies, Merck and Gilead, have publicly acknowledged having research programmes looking at HIV latency reversal and Merck is involved in the vorinostat trials for this reason.

Disulfiram (Antabuse) is an approved drug used to treat alcoholism, its HIV latency-reversing properties emerged from a large drug screening study conducted by the laboratory of Robert Siliciano at Johns Hopkins University (Xing 2011). The discovery is a testament to the impact of the recently formed amfAR Research Consortium for HIV Eradication (ARCHE), which funded the work of Siliciano and collaborator Steve Deeks at the University of California San Francisco; Deeks’s group is now conducing a small trial to investigate whether disulfiram has an effect on latent HIV reservoirs in vivo.

Objectif Recherche Vaccins SIDA (ORVACS) is a foundation based in France that was originally established to support therapeutic HIV vaccine research. ORVACS is sponsoring two trials, Eramune 01 and 02, that are investigating combination approaches to HIV reservoir reduction. Eramune 01 will look at intensifying standard antiretroviral therapy (ART) with the integrase inhibitor raltegravir and CCR5 inhibitor maraviroc, with or without the addition of the cytokine IL-7. Eramune 02 employs the same ART intensification, with or without the addition of a DNA/Ad5 prime-boost therapeutic vaccine developed by the Vaccine Research Center at the National Institutes of Health.

At the National Cancer Institute, an alternate means of ART intensification is being explored. Frank Malderelli’s research group is conducting a pilot study of the cytokine alpha interferon as an adjunct.The trial was motivated by an observation that individuals co-infected with HIV and hepatitis C may have declines in residual HIV viral load levels during alpha interferon treatment.

Although only a limited number of clinical trials can reasonably be described as cure-related at the current time, this is likely to rapidly expand. Plans are afoot at the AIDS Clinical Trials Group (ACTG) to investigate a PD-1 inhibitor made by Merck; this approach is intriguing as it may have the potential to both enhance the immune response to HIV and activate latent viral reservoirs (Kaufmann 2009; DaFonseca 2010). The company VIRxSYS has therapeutic vaccine candidate, VRX1273, that is on the verge of phase I; the construct is unusual in that it consists of a lentiviral vector based on HIV itself (Lemiale 2010). Many older gene therapies and therapeutic vaccines that remain in the pipeline (see Tables 4 and 5) could potentially fit under the new rubric of “cure-related” (and may eventually feature in trials for that purpose), because they aim to protect susceptible cells from HIV or improve immune responses to the virus.

If appropriate circumstances arise, researchers also intend to try and duplicate the case of Timothy Brown. This is a complex goal as it involves identifying people with HIV and cancer requiring stem cell transplantation, then finding a matched donor who lacks the CCR5 receptor (in genetic terms, a donor homozygous for the CCR5∆32 mutation). The doctors involved in Brown’s case, led by clinician Gero Hütter, are spearheading this ongoing effort (Hütter 2011).

Immune-based & gene therapies

The developmental pathway for these types of candidate HIV therapies is particularly complex. Because of the effectiveness of antiretroviral drugs in treating HIV, IBTs and gene therapies needs to be able to supplement their effects, or replace them (either intermittently or permanently); the latter goal obviously overlaps with the idea of a “functional cure” described in the previous section.

There are potential opportunities for supplementing ART because a proportion of HIV-positive individuals experience persistent immune dysfunction despite suppression of viral replication to undetectable levels. The features of this dysfunction typically include poor recovery of CD4 T cell numbers in peripheral blood, persistent skewing of the CD4:CD8 T cell ratio (usually around 2:1 in healthy individuals but often <1 in people with HIV), elevated immune activation and inflammation, decreased numbers of naive CD4 and CD8 T cells and increased numbers of dysfunctional, worn-out CD4 and CD8 T cells that are termed “senescent” (Deeks 2011; Erikstrup 2010; Fernandez 2006; Massanella 2010; Robbins 2009). The senescent cells resemble those that have been shown to accrue in very elderly individuals without HIV infection. The most significant risk factor for experiencing these persistent immunological perturbations on ART is initiating treatment at a low CD4 T cell count. Importantly, research shows that there is a link between these phenomena and an increased risk of illness and mortality (Kesselring 2011; Schechter 2006; Zoufaly 2011); therefore, therapies capable of enhancing the restoration of the immune system might be able to improve the prognosis for this subset of people with HIV. Currently the cytokine IL-7 appears to be the only IBT with any prospect of being evaluated for clinical benefit in this setting.There are however several other approaches that attempt to address different aspects of immune dysfunction, including anti-inflammatories and bone marrow stimulants.

Table 4. Immune-based & gene therapy pipeline 2011

Anti-inflammatories

The antimalarial drugs chloroquine phosphate and hydroxychloroquine are being assessed for their potential to reduce immune activation and improve CD4 T cell recovery in individuals on ART. A very small pilot trial of chloroquine phosphate that was published last year reported significant reductions in markers of immune activation over two months of treatment (Murray 2010).

Mesalamine is an oral anti-inflammatory drug that acts particularly on the cells of the gut (Iacucci 2010), and the US Food and Drug Administration has approved it for the treatment of ulcerative colitis, proctitis, and proctosigmoiditis. The research group of Steve Deeks at the University of California–San Francisco (UCSF) is conducting a small study to ascertain if mesalamine can reduce inflammation levels in HIV-positive people on ART. The study is motivated by evidence that leakage of normally friendly gut bacteria into systemic circulation (microbial translocation) contributes to immune activation in HIV infection (Brenchley 2006) and is associated with poor immune reconstitution on ART (Marchetti 2008). The same research group has also probed the contribution of CMV co-infection to immune activation in people on ART by conducting a trial of the anti-CMV drug valganciclovir. The study, now published, found that markers of activation on CD8 T cells were significantly reduced by this intervention, suggesting suppression of CMV replication could have benefits in co-infected people with HIV (Hunt 2011a). Unfortunately the toxicity profile of valganciclovir makes it a poor candidate for chronic use, so safer anti-CMV therapies will be needed in order for this potential lead to be followed.

A number of investigators are evaluating whether the approved CCR5 inhibitor maraviroc can dampen immune activation and enhance immune reconstitution. Results from two trials presented at the Conference on Retroviruses and Opportunistic Infections in 2011 were not particularly encouraging, however. In one uncontrolled, single-arm experiment markers of immune activation were reported decrease (Wilkin 2011), but in the other randomised placebo-controlled study these markers increased in blood and gut samples (Hunt 2011b). In neither case did CD4 T cell counts increase significantly.

Two new clinical trials are looking at the anti-inflammatory effects of the pain medication etoricoxib and the lipid lowering agent simvastatin in HIV, respectively. The etoricoxib trial is enrolling people naive to ART due to a prior study finding that the drug reduced immune activation and improved T cell function in individuals for whom ART was not indicated based on European guidelines (Pettersen 2011). Researchers at the University of Pennsylvania are recruiting individuals off ART for their study of simvastatin, in order to assess if the drug can reduce the monocyte inflammation and inflammatory cytokine production that has been linked to brain disease in HIV.

Cell infusion and gene therapies

In addition to being involved in the Sangamo Biosciences trials described in the section on research toward a cure, Carl June’s research group at the University of Pennsylvania is evaluating a different gene therapy that modifies CD8 T cells ex vivo, equipping them with a T cell receptor (TCR) that is particularly adept at recognising HIV-infected cells (Varela-Rohena 2008). The souped-up CD8 T cells are then expanded and re-infused back into the individual. The ultimate goal is to combine both CD4 and CD8 T cell gene therapy approaches in order to enhance the ability of both subsets to deal with HIV.

Last year, researcher John Rossi from City of Hope in Los Angeles published results from a phase I trial of a combined gene therapy approach in HIV-infected individuals undergoing hematopoietic stem cell (HSC) transplantation for AIDS-related lymphoma (DiGiusto 2010). Genes encoding three different anti-HIV RNA molecules were introduced into a subset of transplanted HSCs in four individuals, and long-term persistence in multiple cell lineages was demonstrated, albeit at very low levels. Although no therapeutic effect could be demonstrated, the study offers evidence that the concept is feasible. Rossi’s group is now collaborating with Paula Cannon at the University of California at Los Angeles (UCLA) and Sangamo Biosciences to study the deletion of the CCR5 gene in HSCs, in the same setting of AIDS-related lymphoma.

IL-7

The cytokine IL-7 plays a key role in supporting T-cell development and the proliferation and survival of naive and memory T-cells. Results from two phase I trials of IL-7 in people with HIV reported substantial increases in CD4 and CD8 T-cell counts even at the lowest dose (Levy 2009; Sereti 2009). The cytokine was well tolerated. A new glycosylated form of IL-7 that allows less frequent administration is currently in phase II trials. The manufacturer is a French company named Cytheris. The ACTG is considering the possibility of studying the clinical effects of IL-7 in individuals with poor CD4 recovery despite HIV suppression.

The ability of IL-7 to reduce HIV reservoirs is also under investigation, but there is debate regarding its potential in this setting; while viral load blips were observed in one phase I study (Sereti 2009), it has been argued that the source of this virus was not long-lived reservoirs (Imamichi 2011). Furthermore, it has been shown that under some circumstances IL-7 may expand the number of latently HIV-infected CD4 T cells by stimulating their division (Chomont 2009).

Table 5. Therapeutic vaccines pipeline 2011

Therapeutic vaccines

The proposal that therapeutic vaccination might enhance the immune response to HIV was floated soon after the virus was first discovered. But clinical trials of a variety of candidates proved consistently disappointing, with no clear evidence of benefit. The most publicised was a large clinical endpoint study of Jonas Salk’s candidate, Remune, which showed no significant differences in health outcomes between vaccine and placebo (Khan 2000). The arrival of combination ART lessened the need for a therapeutic vaccine, but also opened up a window of opportunity because it became possible to try and induce new immune responses to HIV without interference from the potentially immune-suppressive effects of ongoing viral replication. An array of therapeutic vaccines are undergoing testing in this context.

Scientists at the University of Barcelona published the first data on their dendritic cell-based approach earlier this year (Garcia 2011). A small but statistically significant viral load reduction was observed in the vaccine recipients, along with some evidence for an inverse association between HIV-specific T cell responses and viral load. The company Argos Therapeutics is also developing a dendritic cell-based therapeutic vaccine, with the twist that it is “personalised” by loading the cells with viral RNA from the person who is going to receive the vaccine; the goal is to induce immune responses that are exquisitely specific to each individual’s HIV infection (Routy 2010).

Italian researcher Barbara Ensoli at the National AIDS Center at the Istituto Superiore di Sanità in Rome continues to plug away with studies of a therapeutic Tat protein vaccine that has been in development for over a decade now. Ensoli and colleagues took the dubious step of publishing interim results from an ongoing trial in people on ART, claiming a variety of beneficial effects associated with vaccination, including reductions in markers of immune activation (Ensoli 2010).

A novel approach to therapeutic immunization that recently entered human testing is Opal Immunotherapy. Developed by Stephen Kent’s research group at the University of Melbourne, it involves repurposing sets of overlapping peptides derived from HIV that are normally only used in laboratories to measure T cell responses against the virus. Kent had the idea to try and use the peptides as a vaccine by mixing them with either peripheral blood mononuclear cells (PBMC) or whole blood, then infusing this mixture. Studies in SIV-infected macaques have shown some promise (De Rose 2008) and a phase I trial is now underway.

An alternate strategy being pursued by some therapeutic vaccine manufacturers is immunization of HIV-positive people prior to any significant CD4 T-cell decline, with the aim of delaying the need for ART. At the 2010 International AIDS Conference, results from a 60-person randomised controlled study of this type were reported, showing that a DNA vaccine manufactured by FIT Biotech lowered viral load by around half a log after two years of follow up. A small but statistically significant increase in CD4 T cell counts was also observed (Vardas 2010).

The largest pharmaceutical company involved in this research area is GlaxoSmithKline. Their vaccine candidate, obscurely designated 732462, consists of a fusion protein including several HIV antigens (p24, p17, reverse transcriptase and Nef ) in a proprietary adjuvant, AS01B. GSK is conducting a phase II trial exploring the potential for immunization to delay the need for ART.

Conclusion

As incremental as it may be, there is no doubt that significant progress has occurred over the past few years. Until quite recently, there was no evidence of efficacy from any vaccine, microbicide, or PrEP trial. But the investment in research is starting to pay off, and while it may be frustrating that no product is yet available, there is definitely light at the end of these pipelines.

For cure research, the shift from the laboratory to clinical trials is only just beginning. But there is already hope in the form of Timothy Brown, and an increasing demand for science to push beyond the ART-for-life paradigm that currently prevails. The rising profile of cure research is also providing a welcome opportunity for immune-based and gene therapies to emerge from relative obscurity and enter the mainstream.

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In this study Truvada or placebo was being taken daily as a pre-exposure prophylaxis prevention (PrEP) treatment against HIV. When the decision to stop the study was taken, almost 2000 women from Kenya, Tanzania and South Africa were enrolled, just over half the planned number of particiapants.

These results are both extremely disappointing and surprising given that a similar study in gay men at high risk of infection (young, multiple partners and exposures, high alcohol use etc) showed a strongly protective effect. [2]

FEM-PrEP was also being run in a high-risk group: 20% of 3752 women who came forward to participant were already HIV positive when screened.

The approximate rate of new HIV infections among trial participants was 5% per year. The 56 new HIV infections were equally distributed between the active and placebo arm. Although adherence was reported at 95% similar to self-reported adherence in the iPrEX study, a pharmacokinetic sub-study in iPrEX indicated that actual adherence was far lower.

Further analyses from the study are needed to explain the starkly different results compared to iPrEX. The level of protection was expected to be similar based on systemic exposure to the same prophylactic drugs, but this would also be dependent on drug levels achieved in the genital tract.

As with all prevention studies, all participants were given support to reduce their risk of HIV, including advice to always use condoms.

References:

1. FHI statement on the FEM-PrEP HIV prevention study: FHI to initiate orderly closure of FEM-PrEP. (18 April 2011).
   http://www.fhi.org/en/Research/Projects/FEM-PrEP.htm
2. Grant RM et al. Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. NEJM. 23 November 2010 (10.1056/NEJMoa1011205). Free access:
   http://www.nejm.org/doi/full/10.1056/NEJMoa1011205

On 27 January 2011 the US Centre for Disease Control (CDC) issued preliminary guidance for the use of tenofovir/FTC (Truvada) as primary prophylaxis against HIV infection for gay men at high risk of exposure. [1]

This was based on results from the iPrEX study [2] and is notable as Truvada is not licensed as a prevention medication. The preliminary guidelines were issued in the hope they will reduce “potentially less effective PrEP-related practices” by health providers and in the community. Completing the full guidelines and obtaining expert input and public comment is expected to take several months.

The guidelines emphasise PrEP use only in a similar setting to the iPrEX study – ie only in men who have sex with men and only if they are at high risk. Additionally this should be part of broad health protection care, with limited prescriptions and regular HIV testing.

The guidance in Table 1 is an outline for healthcare providers who decide to prescribe Truvada for PrEP prior to licensing.

Table 1. CDC interim guidance for health-care providers electing to provide preexposure prophylaxis (PrEP) for the prevention of HIV infection in adult men who have sex with men and who are at high risk for sexual acquisition of HIV

Before initiating PrEP

Determine eligibility:

• Document negative HIV antibody test(s) immediately before starting PrEP medication.
• Test for acute HIV infection if patient has symptoms consistent with acute HIV infection.
• Confirm that patient is at substantial, ongoing, high risk for acquiring HIV infection.
• Confirm that calculated creatinine clearance is ≥60 mL per minute (via Cockcroft-Gault formula).

Other recommended action:

• Screen for hepatitis B infection; vaccinate against hepatitis B if susceptible, or treat if active infection exists, regardless of decision about prescribing PrEP.
• Screen and treat as needed for STIs.

Beginning PrEP medication regimen

• Prescribe 1 tablet of Truvada (tenofovir 300 mg plus FTC 200 mg) daily.
• In general, prescribe no more than a 90-day supply, renewable only after HIV testing confirms that patient remains HIV-uninfected.
• If active hepatitis B infection is diagnosed, consider using TDF/FTC for both treatment of active hepatitis B infection and HIV prevention.
• Provide risk-reduction and PrEP medication adherence counseling and condoms.

Follow-up while PrEP medication is being taken

• Every 2–3 months, perform an HIV antibody test; document negative result.
• Evaluate and support PrEP medication adherence at each follow-up visit, more often if inconsistent adherence is identified.
• Assess STI symptoms and, if present, test and treat for STI as needed.
• Every 6 months, test for STI even if patient is asymptomatic, and treat as needed.
• 3 months after initiation, then yearly while on PrEP medication, check blood urea nitrogen and serum creatinine.

On discontinuing PrEP (at patient request, for safety concerns, or if HIV infection is acquired)

• Perform HIV test(s) to confirm whether HIV infection has occurred.
• If HIV positive, order and document results of resistance testing and establish linkage to HIV care.
• If HIV negative, establish linkage to risk-reduction support services as indicated.
• If active hepatitis B is diagnosed at initiation of PrEP, consider appropriate medication for continued treatment of hepatitis B.

Abbreviations:

HIV = human immunodeficiency virus
STI = sexually transmitted infection
TDF = tenofovir disoproxil fumarate
FTC = emtricitabine.

References:

1. Interim Guidance: Preexposure Prophylaxis for the Prevention of HIV Infection in Men Who Have Sex with Men. Morbidity and Mortality Weekly Report (MMWR) January 28, 2011 / 60(03);65-68.
   http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6003a1.htm
2. The iPrEX study was reported in HTB November/December 2010
   http://i-base.info/htb/14191

The published results and the supportive supplementary appendix from a large international study (conducted in Peru, Equador, Brazil, US, Thailand and South Africa) provide the first human evidence that daily tenofovir/FTC (Truvada) can reduce the risk of HIV sexual transmission in men who have sex with men (MSM) at a high risk of HIV exposure. [1, 2]

The results should challenge approaches to HIV prevention and they have the potential to drive improved access to tenofovir as an ARV treatment.

The iPrEx study results, together with the full protocol and supplementary information was published online in the New England Journal of Medicine, and are all available without subscription. The top-level results – reducing infection by 44% with minimal safety side effects were widely publicised but the adherence and drug level analyses suggest a far higher potential for protection.

The study randomised just under 2500 men (including 29 transgender women (male-to-female, <1%) to either daily tenofovir/FTC or placebo. As with other prevention studies, iPrEx included intensive risk-reduction counselling, free condoms (monthly), behaviour interview (quarterly) and sexual health monitoring (at least 6-monthly).

Importantly, participants were at high risk of infection due to their behaviour risk. Ten percent of the approximately 5000 people initially screened for the study were already HIV-positive and a further 10 became infected between screening and enrolment.

Participants were young (~50% aged 18-24; 20% 25-29 and 20% 30-39 years); sexually active in the previous 12 weeks (18 partners; SD +35); at high risk (~80% having had unprotected anal intercourse (UAI) in the previous 6 months with a partner of unknown HIV status); high STI incidence (13% syphilis, 35% HSV-2 at baseline). Over 40% participants had transactional sex in the previous 6 months, alcohol use was common and high (>4 drinks per drinking day in >50% participants) and HIV awareness/disclosure was low (only 2% had knowingly have sex with an HIV-positive person in the previous 6 months). Baseline characteristics were similar between the two arms.

The primary endpoint of at least 85 HIV infections was therefore reached quickly – after a median of 1.2 years (maximum 2.8 years), and total of 3324 patient years of follow-up (PYFU). This was despite a self-reported reduction in risk behaviour (a 50% reduction in the number of partners for receptive intercourse and increasing condom use for receptive intercourse from 50% to 75% of partners) – both potentially the result of a greater focus on HIV risk form the counselling and/or awareness of risk from using a daily prophylaxis.

New infections were reported in 100 participants (36 vs 64 in the active vs placebo group) and demonstrated a crude 44% protection rate (95%CI: 15 to 63; p=0.005) for the active group. Protection was higher in people who reported highest risk sex (recent UAI); 58% protection, 95% CI, 32 to 74). There was no significant between-group difference in protection by geographical region, race or ethnic group, circumcision, level of education, alcohol use, or age.

The analysis of adherence (>95% by self report and 90-95% by pill count; both from week 8 onwards, and slightly lower during the first 8 week) reported higher protection with greater adherence. In a post hoc analyses, pill use on 90% or more of days was recorded at 49% of visits on which efficacy was 73% (95% CI, 41 to 88; p<0.001)

However, results from a small pharmacokinetic sub-study looking at drug levels (both in plasma and intracellular) suggested actual adherence rates could have been dramatically lower. Although the drug level results should be interpreted with caution due to their low number, the associations with infections and suboptimal or undetectable levels were compelling.

Drug levels (testing was sensitive to tenofovir and FTC taken within 14 days, though tested a median of 35 days (IQR 28–56) post-infection) were only detected in plasma or cells in 3/34 (9%) newly infected people in the active arm. Of the 3 people with detectable levels, none had cell-associated drug levels higher than median levels in 22 HIV-negative controls. Conversely, 91% of infections in this sub-group appeared not to be taking tenofovir/FTC on a fortnightly–let alone daily–basis). Rates in an active-arm matched control group of 43 people who were not infected, detected drug levels in approximately 50% of people. Only 8% of this HIV-positive group who were considered high adherence (>50% pills) by self-report were considered on treatment by drug level (compared to 54% of HIV-negative controls).

The odds of HIV infection in people in the active arm with detectable drug levels were 12.9-fold lower (95%CI;1.7 to 99.3; p<0.001), corresponding to a relative reduction in HIV risk of 92% (95% CI, 40 to 99; p<0.001). After adjustment for reported unprotected receptive anal intercourse, the relative risk reduction was 95% (95% CI, 70 to 99; p<0.001).

There was a reassuringly high concordance (>95%) between both plasma and their respective intracellular active moieties and between each drug (both drug were similarly detected in each compartment).

Side effects and tolerability

Although side effects were frequently reported, these were similar between active and placebo groups (70% each, p=0.50) and a similar incidence of serious adverse events (5% each group, p=0.57; NS). Moderate nausea (Grade 2 or higher) was reported more frequently in the active group during the first four weeks (p=0.04)). Unexplained weight loss (>5% weight) occurred more frequently in the active arm (34 vs 19 events, p=0.04).

Creatinine levels were raised (1.1 x ULN or 1.5 x baseline) for 26 measurements in the active arm vs 15 times in the placebo group (2% vs 1% respectively, p=0.08), with 44% remaining in the normal range and 88% of elevated levels not confirmed on the subsequent test. Seven people in the active arm and three in the placebo arm discontinued due to elevated creatinine.

Resistance

While correlation between protection and active drug levels suggests that pre- and post-exposure dosing may be more critical than daily dosing, the risk of resistance in people who become infected is more complicated. Although resistance was not detected in any of the 34 people in the active arm who became infected – potentially exposed to intermittent or continuous dual-therapy – the lack of difference between viral load in infected people in the active and placebo arms (5.15 vs 5.10 log copies/mL in the tenofovir/FTC and placebo groups respectively, p=0.72) suggests low or non-adherence.

However, in 2/10 people in the active arm who were subsequently found to be HIV-positive at baseline, were found to have M184 mutations that could have potentially developed during early exposure to dual tenofovir/FTC therapy. While this could also be explained by infection with drug-resistant HIV (a third person had broad NNRTI and RTI resistance). Further studies, supported by modelling, would help determine whether a higher risk of resistance would be likely to come from daily PrEP (exposure to dual therapy during seroconversion) or intermittent PrEP (exposure to suboptimal drug levels between drug use).

comment

These results are overwhelmingly supportive for a potent new prevention option to reduce the risk of sexual acquisition of HIV in gay men. On an individual risk with good drug levels (PK supports this being taken 24 hours before and within 2 hours after exposure) the reduction in single exposure risk may be as significant as that conferred by an undetectable viral load (<50 copies/mL) in reducing infectiousness of an HIV-positive partner (each >90% reductions). Nevertheless, results from ongoing studies of intermittent PrEP will inform this assumption.

These data do not address the practicality of daily PrEP as a population intervention to reduce infection but they do strongly inform individual protection in the context of high adherence prior to and after exposure risk.

Concerns about the practicality of PrEP as a population-based intervention were quickly raised to challenge the optimism of these positive results: and the efficacy levels in iPrEx clearly don’t support policy changes. Three of these concerns focus on i) 44% efficacy being too low to support population-based widespread use, ii) the ethics of using a lifesaving treatment that is currently accessed by less than 20% of people on treatment in resource-limited settings and iii) implementation. distribution and access.

The first issue may change significantly given positive impact that use of PrEP has now shown, especially if PrEP is combined with other risk reduction options. The second may determine that PrEP will initially be an option used more in Western countries – as with condoms, or antiretroviral treatment. If PrEP safely reduces he risk of sexual transmission then it should be an option that people can chose, whether through private or public health care – as with condoms. If PrEP really works (with careful adherence) the global demand should theoretically drive greater demand, lower prices and more rapid access within ARV treatment programmes.

References:

1. Grant RM et al. Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. NEJM. 23 November 2010 (10.1056/NEJMoa1011205).
   Free access:
   http://www.nejm.org/doi/full/10.1056/NEJMoa1011205
   Direct PDF download:
   http://www.nejm.org/doi/pdf/10.1056/NEJMoa1011205
2. Supplementary appendix: (direct PDF download)
   http://www.nejm.org/doi/suppl/10.1056/NEJMoa1011205/suppl_file/nejmoa1011205_appendix.pdf

Further information:

iPrEx Study press release and fact sheets:
http://www.iprexnews.com

iPrEx study materials NIAID: Press Release:
http://www.niaid.nih.gov/news/newsreleases/2010/Pages/iPrEx.aspx

Q&A:
http://www.niaid.nih.gov/news/QA/Pages/iPrExQA.aspx

A late breaker by Bailey and Colleagues presented at the International AIDS Conference reported on the follow-up to the randomized male medical circumcision trial conducted in Kisumu, Kenya, involving 2874 men aged 18 to 24 years at enrollment. [1]

The authors had previously reported a 60% protective effect of male circumcision against HIV acquisition at 24 months after enrollment, and 64% at 42 months. This poster indicates that this protective effect extends to at least 54 months after enrollment.

As of March 2010, 1552/1740 men (89%) consented to extended follow-up: 767 in the circumcision group and 785 in the control group. The age and number of sexual partners at baseline were the same in both groups. 49% (387/795) of those in the control group have been circumcised since December 2006.

The number of HIV seroconversions by 54 months of follow-up was 39 in the circumcised group and 79 in the uncircumcised group (RR = 0.34; 95%CI: 0.23-0.51). The estimated cumulative incidence [95% CI] at 54 months was 4.0% [95%CI: 2.8-5.7] in the circumcised group and 10.6% [95%CI: 8.2-13.6] in the uncircumcised group (p<0.0002, RR=0.36; 95%CI: 0.24-0.55). The annualised incidence in the circumcised group was 0.91 per 100 person-years and 2.45 per 100 person-years in the uncircumcised group (p=0.0007).

The authors conclude that they found that the 60% protective effect of circumcision against HIV acquisition over 24 months is sustainable, and possibly strengthened, over 54 months of study. They write that these results provide support for policy makers, donors and implementers to scale up comprehensive, safe, voluntary medical male circumcision in appropriate regions as rapidly as possible.

comment

This important finding demonstrates the lasting preventative effect of voluntary male medical circumcision. On 14 July the Bophelo Pele Male Circumcision Project in Orange Farm, one of the sites for the other two randomised controlled trials that showed the efficacy of circumcision, announced that they had reached the milestone of 20,000 safe circumcisions.

This intervention has long-term efficacy and has been proven that it can be conducted at scale and safely. It is therefore sensible to roll it out in areas with large heterosexual epidemics. It needs to be scaled up across sub-Saharan Africa.

References:

1. R.C. Bailey et al. 2010. The protective effect of adult male circumcision against HIV acquisition is sustained for at least 54 months: results from the Kisumu, Kenya trial. XVIII International AIDS Conference, Vienna, July 18-23. Late breaker poster FRLBC101.
   http://pag.aids2010.org/Abstracts.aspx?SID=643&AID=17707
2. Bophelo Pele Male Circumcision Project. 2010. 20 000 safe circumcisions performed in Orange Farm.

In terms of conference headlines, the biggest news came from the results of a prevention study called Caprisa 004. This study reported that a microbicide gel containing 1% tenofovir reduced the risk of infection to women when used before sex to protect against HIV by 39%. [1, 2] Previous microbicides (not using HIV drugs) have not shown a benefit, so a positive result, no matter how slight, was likely to be greeted enthusiastically. When the results were presented, the audience gave the presenters a standing ovation.

Importantly, the presenters stressed that these preliminary results justified further research. This study was based on 98 endpoints for the primary analysis and the sample size ensured that they could be 90% confident of detecting a doubling/halving in the risk (ie an OR of 2 or 0.5). However, because the endpoints are by definition fewer in subgroup analyses, the study is not powered to analyse some of those interesting results. One of the most helpful aspects of the study is that the detailed results were published in a free-access article in Science Express. [3]

The theoretical benefit from an antiretroviral microbicide is similar to the use of pre- and post-exposure prophylaxis (PrEP and PEP) but instead of taking oral drugs, applying a gel enables the active drug to be absorbed in the tissues that are first exposed to the virus. If the cells in the genital tissues have antiretroviral activity, the hope is that this will reduce the risk of infection.

As with all studies, the complexity of the results is in the details, and the presenters themselves cautioned that their results primarily signaled the urgency of running additional studies.

Women were advised to use the microbicide ‘up to 12 hours before sex’ and ‘as soon after as possible’, using a maximum of two doses in any single 24 hour period. The gel was applied with a special pre-filled applicator, similar to a tampon container.

This phase 2b study was in around 900 women aged 18–40 years, living in two districts in South Africa where the risk of HIV for women reaches 50% by the age of 24. One trial site was in urban Durban (n=278) and the second was in a rural location 90 miles from Durban (n=611). This was a double-blind study with women randomised 1:1 to either the active gel or a placebo gel. Free condoms and counselling on the importance of safe sex were provided to all women, with monthly HIV testing and monitoring.

There were significant differences between the rural and urban women. Rural women were younger (mean 23.3 vs 25.1), poorer (86% vs 69% monthly income <R1000), less likely to have a stable partner (77% vs 93%), had fewer lifetime partners (mean 2 vs 6), used condoms less consistently (22% vs 42%) and had lower HSV-2 prevalence (48% vs 60%), see Table 1. However, randomisation ensured that there was no difference in these baseline characteristics between the active and placebo group.

* NS = non significant differences

The predetermined endpoint of 98 events was reached after a mean 18 months with 1341 person years (PY) of follow-up, with a low drop-out rate (~5%).

Of the 98 women who became HIV-positive over 12–30 months, 38 were in the active gel group and 60 were in the placebo group. The HIV incidence rate per 100 PY was 5.6 (CI: 4.0, 7.7) in the tenofovir gel arm compared to 9.1 (CI: 6.9, 11.7) in the placebo gel arm (incidence ratio rate [IRR]=0.61; CI: 0.40, 0.94; p=0.017). After adjusting for baseline covariates including, age, site, anal sex history, contraceptive method, HSV-2 antibody status, and condom use, the hazard ratio was 0.63 (CI: 0.42, 0.94; p=0.025). Sensitivity analysis produced similar results. Although this fell just short of the predetermine OR of 0.50, the results remained statistically significant.

The combined rural/urban analysis produced a protection rate of 39% from using the active compared to placebo gel. However, the 95% confidence intervals are 6% and 60%. Further studies are likely to focus on dosing, adherence and other factors in order to see whether higher protection rates can be seen. Although the results were presented by site, showing effectiveness at the rural site of 43% (95%CI 5, 57; p=0.023) but not at the urban site (26%; 95%CI –59, 67; p=0.380), see Table 2. However, as the study was not designed to compare efficacy by site, while interesting, it was not powered for this comparison to be meaningful.

NOTE: Study was not powered for the subgroup analyses by site and adherence.

† Adherence could not be calculated for the 5 women who reported no sex during their follow-up in the study. NS=non significant

Adherence is essential to monitor in any intervention study, see Table 2. In Caprisa 004, the researchers determined that two applications of the gel were used for over 70% of occasions when participants had sex. While approximately 40% women reported >80% adherence, a similar proportion reported that they used the gel less than half the time. When adherence was 80% or higher (n=336), the protection increased from 39% to 54% (95%CI 4, 80; p=0.025). There appeared to be a trend between adherence and efficacy, and this is clearly plausible, though again the study was not powered for this comparison. The Science Express paper reported 38% protection (95%CI –67, 77; p=0.343) at 50–80% adherence (n=181) dropping to 28% (95%CI –40, 64; p=0.303), when less than 50% (n=367).

The mean number of sex acts in the high, intermediate and low adherence groups was 3.2, 5.0 and 6.7 per month respectively. Median adherence in the women who become HIV-positive was similar throughout the study at approximately 60%, whereas in the HIV-negative women this started at 55% and increased to 75% in the first and last six months respectively. Even with an intensive education and support programme, only a minority of women achieved >80% adherence, and these were the women who had less sex (3 times a month). Condoms were reportedly used 80% of the time, though this may have been over-reported given the rough per-exposure risk this generates for the study, which is not uncommon in prevention studies.

No serious or significant safety issues (from the 4692 reported events) were associated to using the gel in terms of side effects, including renal toxicity or in the 54 unplanned pregnancies that occurred. Mild diarrhoea was reported in 16% people using the active gel compared to 11% of the placebo group. No safety concerns in terms of flares in liver enzymes were seen relating to the use of tenofovir in the small numbers of women who entered the study with active hepatitis B (19 in the active and 15 in the placebo group) or who acquired HBV during the study (22 women, 19 or who cleared the virus without additional treatment). The concern that continued exposure to tenofovir prior to HIV being diagnosed might exert sufficient pressure to generate drug resistance was not supported in genotypic results from 35 women (no K65R, K70E or RTI-associated mutations). Of interest, the use of the active gel had no impact of viral set point after infection (4.65 vs 4.30 log; p=0.15) and participation in the study did not lead to any increase in risk behaviour.

The study also reported an impact on transmission of HSV-2, the virus responsible for genital herpes. Of the 434 women who tested negative for HSV-2 at the beginning of the study, 29 became infected in the active gel group compared to 58 in the placebo group (IR/100PY 9.9 (6.6, 14.2) vs 20.2 (15.3, 26.1). This was reported as tenofovir providing 51% protection against HSV-2 (95%CI: 22%–70%; p = 0.003). Because genital herpes increases the risk of catching HIV, these results are complicated to understand. Although tenofovir has not shown protective effects against HSV-2 in mouse and test-tube studies, drugs with a similar structure to tenofovir such as cidofovir have activity against HSV-2.

Results from the pharmacology substudy of CAPRISA 004 were presented in the same session by Angela Kashuba from the University of North Carolina. [5]

For the HIV analysis, 90 samples were available (37 active and 13 placebo in the HIV-positive women plus 24 active and 16 placebo from women who remained HIV-negative. Tenofovir levels were measured in blood plasma (BP), and cervicovaginal fluid (CVF) for all samples and additionally in vaginal and cervical tissue biopsy samples in the HIV-positive women. Plasma concentrations were minimal (<1 ng/mL), with detectable levels in only 12% of the HIV-positive women (median 0, range 0–0.1 ng/mL) a median 6 days (range 1-25) after application vs 50% of the HIV-negative women (median 0.1, range 0–0.8 ng/mL) after a median of 4.5 days (range 2–28), indicating very low systemic uptake even given the delay in sampling.

Tenofovir was more frequently detected and at higher CVF levels in the HIV-negative compared to HIV-positive women at 45% (median 1 ng/mL range 0–300,000) vs 96% (median 520 ng/mL (range 0–1,340,000), both at 4.5 days. CVF concentrations correlated well with infections and also importantly with intracellular levels of tenofovir diphosphate. This will help establish the target dose in future formulations. A separate PK study of 250 samples from 172 highly adherent HIV-negative women showed a mean half-life of about two days with most concentrations over the first few days of ~1000 ng/mL. It is important to note that there are currently no data on appropriate target levels of either tenofovir or tenofovir diphosphate and that data, as for early absorption (ie how soon before sex would you get protection?) will be the focus of the next studies. These results suggest that drug levels are a marker for adherence rather than poor absorption potentially due to interpatient variability of cellular transporters such as MRPs.

A similar relationship was observed between drug levels and acquisition of HSV-2. While oral tenofovir is not able to achieve sufficient drugs levels to suppress HSV-2 (EC50 ~10,000 ng/mL), this is possible with a topical gel. 24% of the women with levels below this became HSV-2 positive compared to only 6% of women who had levels above.

Very low levels of tenofovir found in two women in the placebo arm was explained by possible shared sexual partners.

comment

The proof of principal that an antiretroviral microbicide can protect against HIV and HSV infection is clearly important news.

The discussion in the published paper suggests that many of the infections may be due to infrequent but very high risk exposures with migrant workers and the investigators noted that the HIV incidence rate was similar in the low frequency placebo group to women who reported much more frequent sex.

In this high-risk setting, infection rates remained high in the women using the active gel (>5/100PY) and protection dropped significantly after 18 months for reasons that are unclear.

The differences in the urban/rural results may just be an issue of overall sample size (as opposed to something connected to the difference in lifetime sex partners or other factors). A good precedent for caution over the adherence analysis however comes from an earlier microbicide study. A similar adherence analysis in the phase 2b PRO2000 HPTN 035 study showed protection rates of 9%, 44% and 78% in low gel users, high gel users, and low condom/high gel users, respectively. Yet this microbicide was subsequently shown not to work.

Of note, the findings on prevention of HSV-2 transmission were more significant and robust than protection against HIV, and this will clearly be the focus for further research study.

References:

Unless otherwise stated, all references are to the Programme and Abstracts of the 17th International AIDS Conference, 18-23 July 2010, Vienna.

1. Karim QA et al. Effectiveness of 1% tenofovir vaginal microbicide gel in South African women: results of the CAPRISA 004 trial. Oral abstract TUSS0502.
   http://pag.aids2010.org/session.aspx?s=13
2. Karim SA et al. Safety of 1% tenofovir vaginal microbicide gel in South African women: results of the CAPRISA 004 trial. Oral abstract TUSS0502.
   http://pag.aids2010.org/Abstracts.aspx?SID=13&AID=17761
3. Karim QA et al. Effectiveness and safety of tenofovir gel, an antiretroviral microbicide, for the prevention of HIV infection in women. Science Express. Published Online 19 July 2010. Science DOI: 10.1126/science.1193748.
   http://www.sciencemag.org/cgi/content/abstract/science.1193748
4. Kashuba ADM et al. Do systemic and genital tract tenofovir concentrations predict HIV seroconversion in the CAPRISA 004 tenofovir gel trial? Oral abstract TUSS0503.

Further information: www.caprisa.org

Heiko Jensen from Praxis presented the results of a large randomised placebo-controlled study in over 4000 men in 18 countries of the Merck quadrivalent HPV vaccine (active against types 6/11/16/18) that was initially studied and approved for use in women. Participants needed to be HIV-negative, HPV seronegative, HPV PCR negative, without genital lesions and to have had fewer than seven sexual partners.

The primary efficacy objective was to demonstrate whether the vaccine reduces the incidence of external genital lesions (EGL) related to HPV6/11/16 or 18.

After approximately two years follow-up, in a per protocol analysis, there were 3 cases of lesions in the active arm vs 31 in the placebo group. This produced efficacy rates of 65.5% (95% CI: 45.8, 78.6) in the ITT and 90.4% (95% CI: 69.2, 98.1) in the per protocol analyses.

The majority of EGL observed were condylomata acuminata; no cases of penile/perianal/perineal intraepithelial neoplasia were observed, though this was a period, follow-up in the study will extend to ten years.

For other endpoints, the rapporteur report noted 89% efficacy in preventing condyloma, 75% efficacy in preventing high grade anal intra-epithelial neoplasia (AIN 2 or more), 78% efficacy in preventing a combined endpoint of AIN or anal cancer over all, and 86% efficacy against “persistent infection” (defined by positive DNA PCR on 2 samples 4 months apart).

References:

1. Jessen H et al. Quadrivalent HPV vaccine efficacy against HPV 6/11/16/18 infection and disease in men. 18th IAS Conference, 18–23 July 2010, Vienna. Late breaker oral abstract THLBB0101.
   http://pag.aids2010.org/Abstracts.aspx?AID=17491
2. Garland et al. Quadrivalent vaccine against Human Papillomavirus to prevent anogenital diseases. N Engl J Med 2007; 356:1928-1943
   http://www.nejm.org/doi/full/10.1056/NEJMoa061741

Every few years an abstract reports anecdotal use of lemon or lime juice as a douche prior to sex to reduce the risk of HIV transmission. The risk associated with this has been demonstrated by many groups, even when lime/lemon diluted, as the acidity causes tissue damage that is more likely to increase the risk of HIV transmission. [1, 2] It was worrying to see this presented again at an IAS meeting in 2010.

This small in vitro data reported that lime juice negatively impacts on healthy, potentially protective, bacteria. The conclusion that ‘future research should proceed with caution” should instead have reported the currently known risks that obviate the need for additional research. [3]

Of interest, another in vitro study in the Jul 2010 edition of AIDS Research and Therapy using lime, lemon and vinegar similarly concluded “The data from this study and previous reports clearly demonstrate that the use of citrus juices as topical microbicides is potentially more toxic than nonoxynol-9 and thus not recommended for vaginal application.” [4]

References:

1. TheBody.com. Why women should NOT use lemon or lime juice as a microbicide. (June 2008)
   http://www.thebody.com/content/treat/art48598.html
2. Shattock R et al. Preclinical evaluation of lime juice as a topical microbicide candidate. Retrovirology 11 January 2008. doi: 10.1186/1742-4690-5-3.
   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2259360/
3. Onyejepu N et al. Assessing the mutagenicity of lime juice: a potential microbicide. 18th IAS Conference, 18–23 July 2010, Vienna.
   http://pag.aids2010.org/Abstracts.aspx?AID=13260
4. Lackman-Smith CS et al. Safety and anti-HIV assessments of natural vaginal cleansing products in an established topical microbicides in vitro testing algorithm. AIDS Research and Therapy 2010, 7:22doi:10.1186/1742-6405-7-22.
   http://www.aidsrestherapy.com/content/7/1/22

Unlike the other pipelines discussed in this report, there are no approved immune-based therapies or biomedical preventive technologies for HIV—aside from antiretroviral therapy itself—(see 2010 Pipeline Summary) to offer a guidepost for product developers. For those attempting to navigate this uncharted terrain, 2009 proved to be another year of vertiginous ups and downs.

In the realm of biomedical prevention, a microbicide candidate (PRO2000 gel) that came within a whisker of showing statistically significant protection in a phase IIb study (Abdool Karim 2009) failed to show any efficacy in a larger, definitive phase III trial (Chisembele 2010). PRO2000 gel was essentially the last in a class of broad-spectrum microbicide candidates and the focus has now shifted to products with more potent and specific anti-HIV effects (after the first edition of this report went to press, encouraging results from a trial of the first antiretroviral-based microbicide were announced – see later in this chapter).

Meanwhile, a huge HIV vaccine trial that took place in Thailand involving two ancient candidates (ALVAC and AIDSVAX) surprised everyone by showing a meager (31.2%) but just about statistically significant degree of protection (Rerks-Ngarm 2009). Despite the size of the trial, however, there were relatively few HIV infection endpoints and the confidence intervals—a statistical measure of the uncertainty associated with a result—were vast, raising the specter that the findings may be as illusory as those of the phase IIb PRO2000 gel trial. Nevertheless, after the paucity of good news in HIV vaccine research, and despite the possibility of a statistical fluke, the Thai trial results have been widely hailed as historic. Plans are now afoot to try and reproduce and improve upon them with similar regimens.

Results from the first efficacy trials of pre-exposure prophylaxis (PrEP) are due to become available later this year, after this report is printed. The antiretrovirals being studied for PrEP are tenofovir and the combination of tenofovir and emtricitabine in a single pill (Truvada). Several other agents are under consideration but, unsurprisingly, PrEP research is currently in a holding pattern awaiting the crucial first efficacy data. Several small studies are evaluating the safety and acceptability of intermittent rather than continuous PrEP, but as yet no efficacy studies are planned.

As in previous years, there remains an imbalance between the need for novel immune-based and gene therapies for HIV and the limited number of candidates trickling sluggishly through the pipeline. Similar to HIV vaccines, the immune-based therapy (IBT) pipeline is prone to tortuous plumbing; even apparently promising candidates often seem to circle back to earlier phase trials rather than progress onward. An example is IL-7, which is widely viewed as the lead CD4 T-cell-boosting candidate: after showing promising results in two phase I trials reported in 2007 (Levy 2007; Sereti 2007), this cytokine therapy was modified to ease its dosing schedule and only recently re-entered phase I testing in its new form. Over the same time period, data have accumulated demonstrating that poor CD4 T-cell reconstitution is a significant risk factor for illness and death in the antiretroviral therapy (ART) era (Marin 2009; Tan 2008; Tuboi 2010). Concern about the overlap between the immunological effects of HIV and aging—particularly depletion of a subset of T cells called naive cells—has renewed interest in boosting the function of the thymus, but there is a striking lack of therapies with any demonstrated potential. IL-7 may have some effect, but appears to preferentially stimulate naive T-cell division rather than enhancing thymic production (Fry 2005). The one approach proven to increase thymus function in people, human growth hormone, is associated with a counterproductive panoply of side effects (Napolitano 2008; Smith 2010).

Beyond general immune-boosting, achievement of a “functional cure”—defined as an absence of detectable HIV replication in the absence of any ongoing treatment—is an ambitious goal of some IBTs and gene therapies. Once almost unimaginable, this possibility has been pushed back into the spotlight by the case of an individual who appears to have been cured of HIV infection after receiving a stem cell transplant while undergoing treatment for a life-threatening cancer (Hütter 2009). The German doctor who performed the transplant, Gero Hütter, smartly sought out a donor with the mutation that abrogates expression of CCR5 (the major HIV coreceptor) on cells. The result was that the individual’s immune system was repopulated with cells highly resistant to HIV infection. More than three years after the procedure, despite a slow and complicated recovery from the cancer and its treatment, the individual remains off ART and lacks any detectable HIV in blood or tissues. The case is being viewed as a “proof of concept” that a cure for HIV is possible, providing a welcome impetus for research efforts in this area.

Table 1. HIV Vaccines Pipeline 2010

The HIV vaccine field has been deluged by disappointment over the years, but September 2009 saw the first sliver of encouragement emerge from Thailand. A huge 16,402-person efficacy trial of two candidates widely viewed as en route to the scrap heap, ALVAC and AIDSVAX, reported evidence of 31.2% efficacy in protecting against HIV infection, a result that just scraped across the boundary of statistical significance. In raw numbers, this represented 51 infections among the 8,192 people randomised to receive the vaccines and 74 infections among the 8,198 placebo recipients (5 participants were excluded from these analyses after being found to have been HIV infected at baseline). However, it is important to note that the statistical robustness of a trial result derives not just from the total sample size but is crucially dependent on the number of endpoints that occur, which in this case was very few relative to the overall number of participants. The upshot is that the confidence intervals around the 31.2% reduction in risk of HIV infection are extremely wide, ranging from 1.1% to 52.1%. In statistical terms, the confidence interval represents the range of possible outcomes if the experiment were to be repeated. From a glass-half-full perspective, it may be considered encouraging that the efficacy of the vaccines might have been as high as 52.1%. But given the poor track record of the candidates involved, the glass-half-empty view inevitably must consider that a large swathe of the numerical territory between 1.1% and 52.1% is indistinguishable from the efficacy of the vaccines being zero.

Beyond the borderline nature of the findings, there was some controversy at the time of the initial announcement by the trial’s sponsors—the U.S. Military HIV Research Program, the Thai Ministry of Health and the U.S. National Institutes of Allergy and Infectious Diseases (NIAID). Rumors abounded that the statistically significant result was undermined by other unreported analyses. The publication of the data in the New England Journal of Medicine a few weeks later set these concerns to rest, as the issue turned out to be related to the strictest “intent-to-treat” (ITT) approach, under which the five individuals found to be HIV infected at baseline had to be included. Using this method the result no longer reached statistically significance, but given that exclusion of people who were infected prior to receipt of any vaccine is both logical and standard in these trials there was no reason for this to be controversial. The fact that so few infection endpoints could affect significance in this way does, however, highlight the statistical fragility of the main result (which is described as the “modified ITT” analysis).

But even if the Thai trial had produced a statistical trend toward efficacy rather than achieving significance, it would have been important for the vaccine field to follow up, and this is indeed what is occurring. Data from participants will be mined in the hope of revealing vaccine-induced immune responses associated with reduced risk of acquiring HIV, known as correlates of immunity. While discovering correlates would be a huge advance, the marginal efficacy and limited numbers of samples may stymie the effort. Currently, the main theories point to some type of antibody-mediated effect, either relating to binding antibodies or antibody-dependent cellular cytotoxicity (ADCC) wherein nonneutralizing antibody responses promote killing of virus-infected cells. The reasoning behind these theories is partly based on evidence of a short-term protective effect in the trial; after the first year, infection rates in the vaccine and placebo groups were very similar, and this observation tracks with binding antibody responses, which peaked in magnitude after the last vaccine booster at six months and declined precipitously thereafter (Michael 2010). Evidence of ADCC was observed in the majority of recipients of the vaccine regimen in earlier trials (Karnasuta 2005). Less likely candidates for immune correlates include HIV-specific CD4 T-cell responses, detected in around 50–90% of vaccinees (as measured by lymphoproliferation to p24 or gp120 antigens) and HIV-specific CD8 T-cell responses that, while detected in around 20% of recipients in prior studies (Nitayaphan 2004), were essentially undetectable in the analyses reported in the New England Journal of Medicine paper (Rerks-Ngarm 2009). The lack of CD8 T cell responses is consistent with the failure of vaccination to measurably affect post-infection viral load among the trial participants who became infected.

The Thai trial follow-up

The main stakeholders in HIV vaccine research have outlined a variety of plans for new studies informed by the Thai trial outcome. Future research needs to address and try and disentangle several interrelated issues:

The Population

The vast majority of the Thai study population were heterosexuals at very low risk for HIV infection, and the entry criteria limited the age range of participants to between 18 and 30. This contrasts with prior trials, which have focused on higher-risk gay men and intravenous drug users as well as recruiting from a broader age range. The extent to which the study population may have affected the Thai trial outcome is unclear, and needs to be addressed. Additional population-specific factors potentially relevant to efforts to replicate or build upon the results elsewhere include circulating HIV strains, routes of HIV exposure, other prevalent sexually transmitted diseases, and co-infections (such as tuberculosis, helminths, and hepatitis B & C).

The Vaccine Constructs

Contrary to a number of erroneous media stories published when the results were first announced, Sanofi Pasteur’s ALVAC vector was not previously tested for efficacy. The vector is made of a bird virus that is harmless to humans called canarypox, and it is not known if there might be unique aspects of this virus that could contribute to immune protection against HIV. ALVAC was not previously regarded as very promising because it only provokes weak immune responses to the HIV antigens it contains. Now it will be necessary to study whether similar poxvirus vectors that appear better at inducing immune responses (such as MVA and NYVAC) have superior or inferior protective efficacy compared to ALVAC. According to a letter sent to collaborators on April 23, 2010, Sanofi Pasteur is in the process of producing additional doses of ALVAC for research purposes. New supplies of vCP1521 are expected to become available in the fall.

The vaccine used as a booster in the Thai trial, AIDSVAX, consists of two recombinant HIV Env proteins from clades B and CRF01_AE and had previously failed to show any efficacy when tested alone in two large trials involving high-risk gay men and intravenous drug users (Flynn 2005; Pitisuttithum 2006). It is impossible to know what role, if any, AIDSVAX played in the trial outcome because there was no comparison with ALVAC alone. One principal investigator, Nelson Michael, has spoken of the need to “deconvolute” the contribution of the two constructs. A planned US-based phase III trial that would have compared ALVAC alone to ALVAC+AIDSVAX did not take place because a prespecified level of immunogenicity was not achieved in phase II (Russell 2007). The company that manufactured AIDSVAX, VaxGen, no longer exists and the rights are held by a non-profit organization called Global Solutions to Infectious Diseases (GSID). Currently planned studies are using existing lots of AIDSVAX and GSID is not being funded to produce additional supplies, at least as yet.

The HIV Vaccine Trials Network (HVTN) has developed a proposal for “sequential adaptive design phase IIb trials” that are intended for the higher-incidence setting of South Africa. The population would be high-risk heterosexual people, with each trial enrolling 1,500 per arm. Based on an annual HIV infection rate of 4%, the HVTN calculates that a nonworking vaccine could be identified and discarded within 20 months, and by 24 months an efficacy signal would be detectable. Around 50 HIV infection endpoints would be enough to know if a vaccine wasn’t working, while 80 would be sufficient to show evidence of efficacy (a 40% or greater reduction in risk of infection). A variety of DNA, poxvirus vector, and protein prime-boost combinations are under consideration for these trials, including DNA+NYVAC+gp120, NYVAC+NYVAC+gp120 and ALVAC+ALVAC+gp120. The exact types of inserts and envelope boosts are still under discussion.

The U.S. Military HIV Research Program (USMHRP) is looking to shed more light on the Thai trial results by conducting new, detailed phase I immunogenicity studies of the vaccine regimen, particularly focusing on mucosal immune responses. Another plan is to boost a small subset of the original trial participants (~100) with another dose of ALVAC or AIDSVAX, or a combination of the two. The USMHRP also has additional candidates waiting in the wings, including a DNA prime MVA boost approach (Earl 2009; Gudmundsdotter 2009).

The Collaboration for AIDS Vaccine Discovery (CAVD), supported by the Bill and Melinda Gates Foundation, is developing a clade C DNA prime/NYVAC boost regimen that has shown immunogenicity in early phase trials (Harari 2008; McCormack 2008). A replication-competent version of the NYVAC vector is also under consideration (vectors currently being studied cannot replicate in humans). The current plan is for an efficacy trial to be conducted in Africa starting in 2013 or 2014.

A DNA prime/adenovirus serotype 5 (Ad5) boost approach developed by the Vaccine Research Center (VRC) at NIAID is being evaluated in an ongoing phase IIb trial designated HVTN 505. The main goal is to assess the effect of the vaccines on viral load levels among recipients who become infected. The Thai trial results provoked some discussion as to whether the size of HVTN 505 should be increased in order to find out if the vaccines could reduce risk of acquiring HIV infection, but this has not occurred. The DNA/Ad5 combination has demonstrated the ability to induce HIV-specific CD4 and CD8 T-cell responses, along with binding (but mostly nonneutralizing) antibodies (Koup 2010). However, whatever the outcome of HTVTN 505, Ad5 vectors will not be developed further due to evidence suggesting they may increase risk of HIV infection among people with preexisting antibody responses against adenovirus serotype 5 (which many people have been exposed to in its natural form, as it is a common cause of bad colds) (Buchbinder 2008). To try and circumvent this problem, the VRC is developing vectors based on adenovirus serotypes that are far less common in nature, Ad26 and Ad28.

Overall, the major repercussion of the Thai trial results has been the re-prioritization of prevention of HIV infection as the major goal for vaccines. This is a significant shift from the previous focus on slowing post-infection disease progression using candidates that only induce T-cell responses against HIV.

The antibody revival

HIV’s mutating, sugar-clustered outer envelope presents a daunting obstacle to antibody-mediated neutralization. Up until last year, only a few rare antibodies capable of broadly neutralizing a diverse array of primary HIV isolates had been identified. These antibodies were cloned from HIV-infected people and, while they are unable to retard disease progression in the setting of chronic infection, it is hoped they could protect an uninfected person if similar antibodies could be induced by vaccination. Reverse engineering a vaccine from an antibody is not easy, however, and only limited progress has been reported to date (Walker 2010). The year 2009 saw notable advances in this area with the discovery of several new broadly neutralizing antibodies (Corti 2010; Walker 2009; Wu 2010). These newer antibodies are far more potent than prior candidates, meaning they exert their inhibitory effect at lower concentrations. While efforts are ongoing to uncover their precise targets on HIV (Kwong 2010; Pejchal 2010), many stakeholders in vaccine research are considering conducting a trial in which a combination of the antibodies would be passively infused in order to test their efficacy at preventing HIV infection.

The International AIDS Vaccine Initiative (IAVI) is planning a phase I trial using adeno-associated virus (AAV) in a manner more akin to gene therapy than traditional vaccination: the AAV vector will encode a gene that persistently manufactures neutralizing antibodies after injection, an approach that has shown promise in macaques challenged with simian immunodeficiency virus (SIV) (Johnson 2009).

Vaccine approaches in human trials

The majority of HIV vaccine candidates in trials represent variations on the prime-boost theme, in which one vaccine is used to initiate immune responses to HIV antigens and a second boosts the responses to higher levels. The goal is to create “memory” immune responses specifically targeting HIV, including CD4 T cells (also called helper cells), CD8 T cells (known as killer T cells due to their primary role of killing infected cells) and B cells that act as factories for the production of antibodies. Exactly which components of HIV represent the best targets for immune responses remains uncertain, so many different possibilities are being studied. Although it has been argued that the viral envelope makes a poor target for immune responses (Kiepiela 2007), the Thai trial results have been interpreted as a strong counterargument, and most vaccines in trials include an envelope antigen or antigens.

A key issue identified after the failure of Merck’s HIV vaccine candidate is the need to improve the breadth of immune responses. T cells and B cells specifically recognise fragments of viral proteins called epitopes, and HIV contains hundreds of potential epitope targets. However, recipients of the Merck vaccine showed CD8 T cell responses against only three epitopes on average (McElrath 2008). To try and address this problem, researchers have developed a new type of antigen called a mosaic which has improved the breadth of epitope targeting in macaque studies (Barouch 2010). Vaccines containing mosaic HIV antigens are expected to enter human studies soon.

ALVAC

Prior to the results of the Thai trial, a plethora of different versions of the ALVAC canarypox vector had been studied in phase I and II trials involving well over a thousand volunteers. The construct used in Thailand, vCP1521, contains the gene encoding the gp120 protein from a virus code named 92TH023 isolated from a Thai individual in Bangkok in the early 1990s. The virus was originally designated as belonging to subtype E, but it has since been recognised that this subtype is largely a circulating recombinant form now known by the name CRF01_AE. The vCP1521 vector also contains a portion of the gp41 protein from the first HIV ever isolated, LAI, which belongs to subtype B. The other two antigens encoded by the ALVAC vector are Gag and protease, also derived from LAI.

Adenovirus Vectors

Controversy persists regarding evidence that Merck’s Ad5 HIV vaccine candidate enhanced susceptibility to HIV infection among study participants with preexisting antibodies against Ad5. A series of analyses conducted by Susan Buchbinder and colleagues considering the impact of multiple variables on the infection rate was unable to rule out an independent contribution of Ad5 vaccination, but the enhancement effect was almost exclusively seen in circumcised men with antibodies against Ad5, whose main risk factor for acquiring HIV infection was insertive anal sex (Robertson 2008). One hypothesis put forward to explain the results was that the vaccine activated Ad5-specific CD4 T cells in a way that provided more targets for HIV infection. Two studies subsequently argued against this possibility by showing that Ad5-specific CD4 T-cell levels—as measured by cytokine production—were not linked to baseline Ad5 antibody status (Hutnick 2009; O’Brien 2009). But a UK-based group has since reported that Ad5-specific CD4 T-cell responses measured by their ability to proliferate do correlate with Ad5 antibody levels, and these CD4 T cells become more susceptible to HIV after stimulation and display markers associated with homing to mucosal tissues (Benlahrech 2009). These researchers argue that there is a link between the extent of prior exposure to natural Ad5 infection and the likelihood of generating mucosal-homing Ad5-specific CD4 T cells in response to Ad5 vaccination. New data has revealed that natural adenovirus infection can be remarkably persistent, with 75% of a small sample of HIV-positive Peruvian men who have sex with men showing detectable virus DNA in rectal swabs (Curlin 2010). More studies are needed to address this concern, which may also apply to other adenovirus vectors because adenovirus-specific CD4 T-cell responses cross-react with multiple different serotypes. A number of alternate adenovirus serotype HIV vaccines are in trials, including Ad26, Ad35, and Ad5HVR48 (the latter uses a backbone of Ad5 but the major antibody target, the hexon protein, is from the rarer Ad48 serotype).

Modified Vaccinia Virus Ankara Strain

The Modified Vaccinia Virus Ankara strain (MVA) is an attenuated, nonpathogenic derivative of the cowpox virus. The Karolinska Institute and the USMHRP are advancing a DNA/MVA prime-boost approach into phase II studies. Published studies indicate the approach induces HIV-specific CD4 and CD8 T-cell responses in the majority of volunteers (Aboud 2010; Sandström 2008). A similar DNA/MVA approach developed by a company called GeoVax is in a phase IIa immunogenicity trial under the aegis of the HVTN.

Vaccinia-based Vectors

NYVAC is a highly attenuated derivative of the Copenhagen strain of vaccinia virus being studied as an HIV vaccine vector by the CAVD. The vector is being manufactured by Sanofi Pasteur. Judith Hurwitz at St. Jude Children’s Hospital in Memphis, Tennessee, is employing a vaccinia vector as part of an experimental HIV vaccine regimen that delivers a cocktail of 23 different viral envelope proteins (Sealy 2009).

DNA Vaccines

DNA vaccines represent one of the simplest approaches to vaccination. They consist of DNA sequences encoding protein antigens and typically contain little in the way of extraneous components. Despite encouraging initial results in mice, DNA vaccines have proven poorly immunogenic in people. One promising approach for improving the immune response to DNA vaccines is called electroporation, which involves using a special wand to deliver a brief electrical charge to the muscle into eiwhich the vaccine is being injected. The electricity opens transient pores in local cell membranes, allowing the DNA easier access to the cell’s nucleus, where it produces vaccine-encoded antigens. Electroporation also attracts inflammatory cells—including antigen-presenting dendritic cells—to the immunization site. Preliminary results from a phase I trial conducted by the Aaron Diamond AIDS Research Center, the International AIDS Vaccine Initiative, and Ichor Medical Systems suggest that the approach may be able to improve the magnitude, breadth and rate of response to DNA immunization (Vasan 2009).

MYM-V101

One of relatively few vaccines not following the DNA or vector model is a candidate developed by the Swiss company Mymetics. The approach involves components from the HIV envelope encased in a mimic of the viral membrane called a “virosome.” The intent is not the induction of traditional neutralizing antibodies, but rather antibodies that can inhibit the transport of HIV across mucosal surfaces. In a study presented at CROI last year, the vaccine completely protected monkeys from a hybrid SIV/HIV virus called SHIV162p3 (which, unlike prior simian-human immunodeficiency viruses, includes the envelope from an R5-using primary HIV isolate) (Bomsel 2009). Mymetics is now working with animal model expert Chris Miller at the University of California–San Diego to establish whether these results can be independently confirmed. Phase I human trials are also underway.

DCVax-001

Dendritic cells are responsible for initiating immune responses and have been dubbed “nature’s adjuvant” by immunologist Ralph Steinman. Steinman’s own laboratory has recently entered the vaccine development arena with a phase 1 trial of a vaccine that specifically targets dendritic cells via a receptor called DEC-205 (Nchinda 2010). The prototype under study only encodes the HIV-1 Gag p24 protein, but additional inserts are planned if the approach shows promising immunogenicity.

Pre-exposure prophylaxis

Pre-exposure prophylaxis (PrEP) is the prophylactic use of antiretroviral drugs to prevent HIV infection. Currently two drugs are being evaluated in phase II and III studies as PrEP: the nucleotide reverse transcriptase inhibitor tenofovir (Viread) and a combination pill called Truvada, which contains tenofovir and the nucleoside reverse transcriptase inhibitor emtrictabine (Emtriva).

The U.S. Centers for Disease Control and Prevention (CDC) is sponsoring two ongoing PrEP efficacy trials: a study among 2,400 injection drug users in Thailand is evaluating tenofovir alone, while a study in Botswana is looking at Truvada in a population of 2,000 heterosexual men and women. Results from these trials are anticipated later in 2010. An NIH-sponsored efficacy trial of Truvada as PrEP in high-risk gay men in Brazil, Ecuador, Peru, South Africa, Thailand, and the United States—which underwent a long period of community consultation, planning, and preparation—is now well underway, with interim results possibly also becoming available before the end of 2010.

More recently initiated trials include a comparison of tenofovir to Truvada as PrEP in 3,900 serodiscordant couples, being conducted by the University of Washington in Kenya and Uganda. The Microbicide Trial Network’s VOICE study is enrolling 4,200 African women and will compare three strategies: oral PrEP, using tenofovir or Truvada, versus a tenofovir-containing vaginal microbicide gel. Family Health International has launched a trial of Truvada as PrEP in 3,900 women at sites in Kenya, Malawi, South Africa, and Tanzania. Finally, a smaller pilot study looking at the acceptability and feasibility of PrEP among men who have sex with men aged 18–22 is taking place in Chicago under the sponsorship of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Table 2. PrEP and Microbicides Pipeline 2010

Microbicides

Microbicides are substances that aim to prevent HIV infection via application to the vagina or rectum prior to sex. As mentioned in the introduction (and covered in last year’s Pipeline Report), a presentation by Salim Abdool Karim at the 2009 Conference of Retroviruses and Opportunistic Infections (CROI) generated a great deal of excitement because it suggested that PRO2000 gel might have been mildly efficacious at preventing HIV infection in a trial among high-risk South African women (Abdool Karim 2009). In a comparison with a control group that received no gel, PRO2000 appeared to reduce risk by 33% with a p-value of 0.06 (the standard threshold for significance is 0.05). A CROI audience member noted that a comparison between the PRO2000 gel group and a combination of two control groups in the trial (one that received no gel and another that received a placebo gel) would push the result into significance. To his credit, Abdool Karim explicitly resisted this illegitimate statistical maneuver because combining the control groups was not part of the prespecified plan.

Abdool Karim’s caution proved prescient when the results of a far larger phase III efficacy trial of PRO2000 gel (which enrolled close to 10,000 women) were announced at the end of 2009. HIV infection rates were essentially identical between placebo and active gel recipients (Chisembele 2010). While disappointing, the outcome has reinforced a shift in microbicide research toward antiretroviral-based products. Efficacy results from an important first test of this approach—a phase IIb study of a gel form of the reverse transcriptase inhibitor tenofovir (Viread) called CAPRISA 004—were published in the journal Science on July 19, 2010 (Karim 2010) and presented at the International AIDS Conference in Vienna the following day. In an extremely encouraging development for the microbicide field, recipients of tenofovir gel showed a 39% reduction in risk of HIV acquisition that was highly statistically significant (p=0.017). In raw numbers, there were 38 infections out of a total of 445 tenofovir gel recipients and 60 among the 444 placebo recipients. An analysis of genital tract tenofovir levels, presented in Vienna by Angela Kashuba but not yet published, found significant associations between the amount of drug present and risk of HIV infection, bolstering the case that the observed protective efficacy was real (Kashuba 2010). However, there are limitations: the study was relatively small and the 95% confidence interval was wide, ranging from 6-60% protection. Plans are now afoot to rapidly try and confirm the findings. There is also a large ongoing trial sponsored by the Microbicides Trial Network called the VOICE study which includes an arm in which women are receiving tenofovir gel. The 2011 edition of the TAG pipeline report will include a more detailed and extensive discussion of the CAPRISA 004 findings and follow-up planning.

A number of other antiretroviral microbicides are advancing in human trials. The reverse transcriptase inhibitor UC-781, originally developed by Uniroyal Chemical and Biosyn, is in a phase I trial sponsored by CONRAD (Schwartz 2008). UC-781 is also being explored for potential rectal use, with encouraging results from a phase I trial published recently (Ventuneac 2010).

The International Partnership for Microbicides (IPM) is developing a nonnucleoside reverse transcriptase inhibitor, dapirivine gel (licensed from Tibotec and formerly known as TMC120), that is currently in phase I/II trials. The IPM has pioneered studies of novel delivery methods, and results indicate that dapirivine can be safely delivered via a matrix intravaginal ring (Nel 2009).

The push toward long-acting delivery methods for microbicides reflects longstanding concerns about the usability and efficacy of topically applied candidates. Adherence to the use of coitally dependent products has been reported to be an issue in some trials (Skoler-Karpoff 2008), and even if adherence is optimal there is evidence that the physical act of sex may affect the genital-tract distribution of a topical microbicide and thereby reduce its ability to inhibit HIV infection (Keller 2010).

Immune-based therapies

The designation immune-based therapy encompasses a broad range of approaches that aim to produce health benefits by affecting the function of the immune system. IBTs can be subdivided into candidates that seek to improve immune function and/or clinical health overall (e.g., cytokines like IL-7 and anti-inflammatory approaches), those that try to enhance the immune response to HIV itself (e.g., therapeutic vaccines), and gene therapies that alter the makeup of the immune system in ways intended to ameliorate the harmful effects of HIV (or perhaps even shut down the virus completely).

Suppression of viral replication by ART is associated with a huge reduction in risk of illness and death, closing the life expectancy gap between HIV-positive people and their HIV-negative counterparts (Antiretroviral Therapy Cohort Collaboration 2008, 2009; Lohse 2007; van Sighem 2010). However, in most studies, a gap still exists. Furthermore, poor CD4 recovery despite viral load control and persistently elevated levels of immune activation and inflammation on ART are associated with an increased risk of morbidity and mortality (Kuller 2008; Rodger 2009). These findings suggest that IBTs capable of enhancing immune reconstitution and/or reducing residual immune activation and inflammation could provide significant health benefits to a subset of people with HIV on ART. Unfortunately however, there remains a dearth of candidates in the pipeline.

An interrelated concern is the association between HIV infection and immune senescence, which is characterised by the accumulation of dysfunctional memory T-cell populations in the CD4 and the CD8 T-cell pools—particularly the latter. These dysfunctional cells are stubbornly resistant to apoptosis (cell death), produce large amounts of proinflammatory cytokines and are characterised by lack of cell surface expression of the costimulatory molecule CD28 and elevated expression of a senescence marker, CD57 (Effros 2005). A similar phenomenon is seen in the elderly in the absence of HIV infection; in this setting, elevated levels of senescent CD8 T cells designate an “immune risk phenotype” that is associated with frailty, ill health, and earlier mortality (Larbi 2008). A number of recent studies suggest that people with HIV may face similar issues at a younger age due to an acceleration of immune senescence (Desai 2010). Researchers such as Rita Effros from the University of California–Los Angeles are working on strategies aiming to reverse senescence and/or eliminate senescent cells, but they are as yet only at the preclinical stages of development (Fauce 2008). Another important immunological consequence of both aging and HIV infection is the decline in thymus function and resultant diminution of naive T cells (Schacker 2010) and, as stated in the introduction, researchers continue to look for approaches that may halt or reverse this process.

Table 3. Therapeutic Vaccines Pipeline 2010

Table 4. Cytokine, Immunomodulator, and Gene Therapy Pipeline 2010

Therapeutic Vaccines

A bewildering array of therapeutic vaccine candidates continues to undergo testing. The large body of evidence suggesting that HIV-specific CD4 and CD8 cells play a key role in individuals who control viral replication in the absence of ART has prompted this research. (Hersperger 2010; Saag 2010). For the most part, the hope is that therapeutic vaccines may be able to induce the maturation of new HIV-specific T-cell responses while viral load is suppressed by ART, and these responses may be better equipped to battle HIV when ART is subsequently interrupted. Results from a phase IIb treatment interruption trial of Vacc-4x, a peptide-based therapeutic vaccine developed by Bionor Immuno, are anticipated before the end of 2010.

Another strategy being employed is the immunization of HIV-positive people prior to any significant CD4 T-cell decline, with the aim of delaying the need for ART. Two new studies of peptide-based therapeutic vaccines, HIV-v and AFO-18, are taking this tack. At the 2010 International AIDS Conference, results from a 60-person randomised controlled study of this type were reported, showing that a DNA vaccine manufactured by FIT Biotech lowered viral load by around half a log after two years of follow up. A small but statistically significant increase in CD4 T cell counts was also reported (Vardas 2010).

One possibility receiving little attention is that therapeutic vaccination might reduce HIV-induced inflammation by bolstering virus-specific T cell responses. This may seem counterintuitive, but decreased immune activation was been reported many years ago in a trial of Jonas Salk’s now discontinued whole-killed therapeutic HIV vaccine (Fernandez-Cruz 2002).

Anti-inflammatory Approaches

The associations between inflammatory markers and adverse clinical events have bolstered the rationale for studying approaches that might reduce immune activation in people with HIV infection. The malaria drug chloroquine phosphate is being studied for both direct anti-HIV and anti-inflammatory effects. Aspirin and pentoxifylline are also being studied in combination with ART, but not to assess their impact on HIV progression; instead, the outcome measures being looked at are markers of cardiovascular disease risk. Encouraging results from the phase I trial of pentoxifylline have been published (Gupta 2010), leading to the opening of a larger phase II study.

Mesalamine

Mesalamine is an oral anti-inflammatory drug that acts particularly on the cells of the gut (Iacucci 2010), and the U.S. Food and Drug Administration has approved it for the treatment of ulcerative colitis, proctitis, and proctosigmoiditis. Researchers at the University of California–San Francisco are conducting a small study to ascertain if mesalamine can reduce inflammation levels in HIV-positive people on ART. The study is motivated by evidence that leakage of normally friendly gut bacteria into systemic circulation (microbial translocation) contributes to immune activation in HIV infection (Brenchley 2006) and is associated with poor immune reconstitution on ART (Marchetti 2008).

Cell Infusion and Gene Therapies

Several phase I and II studies of gene therapies are ongoing. The broad goal of these approaches is to enable CD4 T cells to resist HIV infection. Results from the phase II trial of Johnson & Johnson’s OZ-1 anti-Tat gene therapy were published in 2009; the product failed to meet the primary endpoint of significantly reducing viral load during an ART interruption but several exploratory analysis suggested that there may have been a mild antiviral effect (Mitsuyasu 2009).

Carl June’s research group has launched a novel study in which CD4 T cells are sampled and manipulated in the laboratory so that they can no longer express the CCR5 coreceptor. This is achieved using a zinc finger nuclease technology developed and manufactured by Sangamo Biosciences. The zinc finger nucleases act like biological scissors and snip out the CCR5 gene from the CD4 T cells’ DNA. The CCR5-negative CD4 T cells are then expanded and reinfused into the individual. Interest in this approach has been piqued by the case of the apparently cured individual cited in the introduction (Hütter 2009). June gave an update on the status of the trial at a Keystone HIV pathogenesis meeting in January 2010: the research is proceeding slowly due to careful safety evaluations and so far only one person has been infused. No concerns have arisen and preliminary evidence suggests that the CCR5-negative CD4 T cells are persisting and expanding slightly in vivo, representing 2.1% of peripheral blood CD4 cells at 140 days of follow up (June 2010). June’s research group is also evaluating a different gene therapy that modifies CD8 T cells ex vivo, equipping them with a T cell receptor (TCR) that is particularly adept at recognizing HIV-infected cells (Varela-Rohena 2008). The souped-up CD8 T cells are then expanded and re-infused back into the individual. The ultimate goal is to combine the CD4 and CD8 T cell gene therapy approaches in order to bolster the ability of both subsets to deal with HIV.

Just prior to this report going to press, researcher John Rossi published results from a phase I trial of a combined gene therapy approach in HIV-infected individuals undergoing hematopoietic stem cell (HSC) transplantation for AIDS-related lymphoma (DiGiusto 2010). Genes encoding three different anti-HIV RNA molecules were introduced into a subset of transplanted HSCs in four individuals, and long-term persistence in multiple cell lineages was demonstrated, albeit at very low levels. Although no therapeutic effect could be demonstrated, the study has been hailed as proof that the concept is feasible.

A similar protocol is being employed by researchers developing M87o, a gene therapy that encodes an HIV entry inhibitor similar to the drug Fuzeon (van Lunzen 2007). A phase I trial is being performed in individuals with AIDS-related lymphoma who require stem cell transplantation, and the M87o gene is added to a subset of the stem cells prior to the procedure.

IL-7

IL-7 is a cytokine that plays a key role in T-cell development and naive and memory T-cell proliferation and survival. Results from two phase I trials of IL-7 in people with HIV reported substantial increases in CD4 and CD8 T-cell counts even at the lowest dose studied (Levy 2007; Sereti 2007). The drug was well tolerated. These results suggest that IL-7 may be an excellent candidate for studies in people with inadequate immune reconstitution despite ART. A new glycosylated form of IL-7 that allows less frequent dosing is now in phase I trials. The manufacturer is a French company called Cytheris.

Maraviroc

Maraviroc is an approved antiretroviral drug (marketed under the name Selzentry) that works by blocking the interaction between HIV and the chemokine receptor CCR5. Five clinical trials are evaluating whether adding maraviroc can increase CD4 T-cell counts in people on ART with poor CD4 T-cell recovery despite prolonged viral load suppression. Researchers from the U.S.-based AIDS Clinical Trials Group recently presented results of a study addressing this question and, while receipt of maraviroc was associated with declines in immune activation markers, there was no significant CD4 T-cell increase compared to standard ART (Wilkin 2010).

TXA127

TXA127 is one of the very few IBTs being studied in individuals with poor CD4 T-cell reconstitution despite viral load suppression by ART. The other name for the drug is angiotensin 1-7 and it has been shown to stimulate bone marrow production of hematopoietic progenitor cells in animal models (Heringer-Walther 2009). These progenitor cells give rise to multiple lineages of immune cells, including CD4 T cells, hence the rationale for study in HIV. A small phase I/II trial has reported a reduction in the incidence of low blood cells after chemotherapy for breast cancer (Rodgers 2006).

Conclusion

The Thai results have boosted flagging hopes for HIV vaccine research, but it will be some time before it is known whether they can be repeated in other settings. The apparent success of the trial has shone on a spotlight on the shortsightedness of the design which, as the investigators have acknowledged, made the relative contributions of the two components impossible to disentangle. TAG drew attention to this obvious issue when the trial first began (Jefferys 2004). From a policy perspective this is problematic: on the one hand the urgent need for an HIV vaccine is emphasised to the public to promote support for research funding, while on the other investigators unabashedly propose repeating a huge, lengthy trial in order to “deconvolute” the results. In the future, trials must be designed in a way that precludes the contribution of the individual vaccine components becoming convoluted in the first place. The PreP and microbicide fields are united in anticipation of imminent efficacy trial results. The findings from these trials will be crucial in determining the next steps in these research areas. Immune-based therapies continue to appeal on paper while struggling in the real world. But renewed attention to the importance of translational (bench-to-bedside) research and some encouraging signs from the cancer field offer hope that breakthroughs are possible. Ultimately, it is to be hoped that the reinvigorated research effort into curing HIV infection, along with a successful sterilizing vaccine, will render these pipelines moot.

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Many other studies at the conference deserve further reporting but can only be briefly summariesed here. For full details please refer to the conference abstracts and contact the lead authors.

All references are to the Abstracts of the 2nd Joint conference of the BHIVA and BASHH, 20–23 April 2010, Manchester.

Abstracts from the conference are published as a supplement to the May 2010 edition of HIV Medicine; Volume 11, Supplement 1.

http://www.aegis.org/conferences/BHIVA/2010/16BHIVA-2010.pdf

Transmission and late diagnosis in older people: half of late diagnoses in people over 50 years old

An oral presentation from the Health Protection Agency highlighted some aspects of how older people are affected by HIV. The number of older adults who are HIV-positive in the UK from 2333 in 2000 to 8268 in 2007, accounting for 16% of adults accessing care in 2007 and 8% of all HIV diagnoses between 2000–2007. [1]

Compared to younger adults, newly diagnosed adults aged 50 years and over were more likely to be men (74% vs. 58%; p<0.001), infected through sex between men (40% vs. 34%; p<0.001) and of white ethnicity (60% vs. 38%; p<0.001). Older heterosexuals adults were more likely to be infected within the UK (16% vs. 12%; p<0.001), with evidence of travel abroad amongst white heterosexual men.

Late diagnosis (CD4 count <200) was significantly higher amongst older adults (48% vs. 33%; p<0.001); with older MSM being twice as likely to present late than younger MSM.

This study estimated that nearly half (48%; 1486) of persons diagnosed between 2000 and 2007 acquired their infection aged 50 and over.

Ref: Smith R et al. Refocusing our efforts – transmission and late diagnosis of HIV among adults aged 50 and over. Oral abstract O3.

Ocular syphilis at first presentation of HIV

Three cases were described where ocular syphilis was the presenting symptom: a 33-year old heterosexual man, a 20-year old gay man, and a 39-year old gay man. The study concluded: “Syphilis should be excluded in cases of uveitis and optic neuritis; other features of secondary syphilis may be absent. All patients had improving visual symptoms after neurosyphilis therapy, and had preceding oral steroids to prevent Jarisch-Herxheimer reaction, as this can worsen ocular symptoms. Early diagnosis is important as ocular syphilis can rapidly cause blindness.

Ref: Dhairyawan R et al. Ocular syphilis as the first presentation of HIV infection. Poster abstract P132.

Perinatally infection diagnosed in late adolescence

Two cases of extremely late diagnosis, in a young man and woman, both 20-year old Ugandan patients, presenting with multiple complications, including HIV-related dementia. These rare cases highlight the importance of family history and HIV testing in children and young adults who were potentially exposed to HIV during pregnancy and at birth.

Ref: Ross S et al. Vertical HIV infection in young adults presenting with HIV-associated dementia. Poster abstract P169.

A poster discussion session included studies looking at different aspects of dual infection and reinfection and included two case studies that showed where this had a clinical outcome. Two other studies, one from London and one from San Francisco, reported on aspects of dual infections.

Erika Castro from University of Vaudois Hospital, Lausanne, and colleagues presented a useful case of reinfection between two men (M1 and M2) who had been sexual partners since 2006. [1]

M1 was initially diagnosed in 2000 during primary infection and had been suppressed on HAART through to 2007 with no history of drug resistance. M2 had been on HAART for five years with detectable viral load (range 3–4 log) and documented triple class resistance. In February 2008, viral load in M1 rebounded to 280 copies/mL and continued increasing. Resistance and phylogenetic tests were compared from 2000 and 2008 (86 sequences:  whole-genome (n=28), env (n=28), and gag (n=25).

All sequences were sub-type B. The genotypic analysis from 2008 showed 25 new related drug resistance mutations in M1 (11 in RT and 14 in protease), of which 23 were also present in M2. Additionally, M1-2008 sequences clustered within the M2-2008 branches and distinct from M1-2000 sequence clusters in all trees. Recombination between the original M1 and M2 strains was not observed, with M1 being replaced with M2 sequences following superinfection.

The case is important for highlighting several aspects of HIV reinfection:

• That reinfection can occur in established infection.
• That it can occur between regular partners (that no immune protection develops to repeated exposure to one virus).
• That reinfection can occur after several years of exposure (as with initial infection, chance and probability are low).
• That there is a clinical risk from reinfection when partners have different resistance profiles (most reinfection cases are only discovered because of unexplained viraemia in stable patients).
• That ART did not offer protection against reinfection, probably because any PEP effect would be negligible if the new MDR virus was resistant to the ARVs in that combination.

Martine Braibant from University de Tours Hospital and colleagues presented another case of sub-type B being reinfected with subsequent sub-type B infection. [2]

This patient entered a long-term non-progressor (LTNP) cohort in 1995 aged 58, following a ten year history of HIV infection, with a CD4 count >600 cells/mm3 for the previous 5 years and viral load of 135 copies/mL on study entry. From 1995–1999, viral load slowly increased to around 10,000 copies/mL and CD4 count dropped steadily to <500 cells/mm3. The initial infection was found to have a 20 nucleotide deletion in nef (consistent in 28 sequences) and the loss of viral control and immunologic progression from 1995 was associated with detection of subsequent sequential reinfection with two fully competent phylogentically different strains. Both new strains were also sub-type B.

The patient responded well to HAART, achieving viral suppression and CD4 recovery >700 cells/mm3 within the first year of therapy, but potentially would have maintained the option to remain off-treatment for many years if reinfection hadn’t occurred.

This case highlighted that:

• Progression rates may be determined by both virologic and immunologic factors
• Reinfection in the absence of resistance may have clinical implications on disease progression, requiring earlier treatment
• That long-term exposure to low level sub-type B virus did not promote an immune response that was protective of subsequent sub-type B infections,

The authors highlighted in their conclusion that this last point showed the inherent difficulties for development of a preventative vaccine.

Jane Deayton and colleagues from St Barts Hospital, London report three cases of inter-clade dual infection detected during routine genotype testing. The three cases were Caucasian UK-born MSM whose only risk factor was sexual exposure in the UK. Case 1 had been diagnosed in 2001 and received a genotype test in 2008 prior to starting therapy that indicated dual infection with sub-types B and G. Cases 2 and 3 were tested after their HIV diagnoses in 2007 and 2008 and showed dual infections with B and CRF02_AG, and B and A, respectively. Both these patients were reported to be stable off treatment.

None of the cases included significant drug resistance mutations.

The authors concluded that these were the reports of cross-clade dual infection from sexual transmission in MSM in the UK are rare (only one other was known). Additionally this indicated onward transmission of clades associated with African epidemics and an increasing cross-over of viruses between different demographic groups.

Finally, Larry Bragg and colleagues in San Francisco presented a poster looking at cases where majority viruses change in an individual though competitive expression following dual infection. Whilst difficult to distinguish from superinfection (ie reinfection after an initial infection) sequential expression of dual infections (SEDI) theoretically could come from dual initial infection or reinfection shortly after initial infection, especially prior to seroconversion. [4]

The group included 220 recently infected persons with at least two genotypes (560 person-years of follow-up). The mean age was 37 and median time from infection to first test was 107 days. Divergent viruses appeared in 7 cases, an overall incidence density of 1.24/100 person-years.

Their model estimated a risk of SEDI that was 16-fold higher in the first year post-infection compared to after one year. The estimated rate of SEDI was 4.1/100 person-years (95% CI, 1.8 to 9.2) in the first year following infection and was 0.2 per 100 person-years beyond 1 year post-infection (95% CI, 0.03 to 1.8).

This study highlighted that in the case of dual infection or early reinfection the predominant infection is determined within the first year.

References

1. Castro E et al. HIV-1 superinfection with a drug-resistant strain in a patient successfully controlled with ART. Poster abstract 480.

http://www.retroconference.org/2010/Abstracts/37374.htm

2. Braibant M et al. Disease progression after intrasubtype superinfection in an HLA-B57+ asymptomatic LTNP initially infected with a nef-defective HIV-1 strain. Poster abstract 302.

http://www.retroconference.org/2010/Abstracts/38615.htm

3. Deayton J et al. Inter-clade dual HIV-1 infection: an emerging phenomenon. Poster abstract 447.

http://www.retroconference.org/2010/Abstracts/38460.htm

4 Bragg L et al. HIV-1 Superinfection Surveillance in an Acute Infection Cohort Using pol Sequences from Resistance Genotyping: 1996 to 2008. Poster abstract 446.

http://www.retroconference.org/2010/Abstracts/39292.htm

CROI was important this year because of the profile given to further studies supporting the role of treatment as prevention. Together they support the argument that universal treatment is perhaps the most powerful prevention tool we are likely to have for many years, perhaps with the potential to even eradicate the virus on a population level.

In a lecture prior to the main conference, Brian Williams from the South African Centre for Epidemiological Modelling and Analysis, Stellensbosch, detailed the modeling data for the direct and indirect impact of ARVs on prevention, [1] elaborating on the research paper published last year in the Lancet. [2]

At its most optimistic, this includes the potential for universal treatment to eliminate new infections in South Africa within 5-10 years on a cost neutral budget, at the same time saving millions of lives (and preventing millions of new infections). The science on which the model is based shows an impact on dramatically reducing infections that few can ignore.

The epidemiology for the model included low HIV infectivity (~0.001 per heterosexual encounter), 10-fold individual variability in infectivity, a slow epidemic doubling time (~1-3 years), a long period of potential infectiousness (5-15 years) and an average case reproduction number (~7 additional people infected per case): leading to a calculation showing that virtual eradication of HIV could be achieved if transmission could be reduced by 7-fold.

Viral load is commonly reduced by 10,000 times on treatment, and although infectivity reduces in smaller proportions (roughly in relation to the cubic root of viral load), the net impact of treatment on infectivity was estimated to be a 96% reduction.

The impact on reducing TB and for continuous treatment after pregnancy were also included, and for interventions based only on PrEP alone or in combination with ARVs. For South Africa, the model was based on a conservative treatment programme, treating at a CD4 count of 200 cells/mm3, but similar costs and benefits were shown when starting universal treatment at 350, 500 or even at diagnosis. The initial outlay (an adjusted US $60 billion) was compensated by lower cost of hospitalisations and reduced new infections, and saved an additional 3 million lives over 40 years, at stable costs.

The discussion after the presentation stressed the need for pilot operational research on each aspect of a universal treatment model, including willingness to test, virological response rates with earlier treatment, the actual impact on transmission – and the need to develop new heath structures to allow such scale-up.

A first step in confirming treatment reduces HIV transmission in real world settings was shown in results from the Partners in Prevention HSV/HIV Transmission (PARTNERS) Study in over 3400 serodifferent heterosexual couples in seven southern African countries (Botswana, Kenya, Rwanda, South Africa, Tanzania, Uganda, and Zambia).  The HIV-positive partner was a man in 32% and a woman in 68% of couples. [3]

This study previously reported that HSV therapy with daily acyclovir failed to protect against HIV infections, explained by a massive increase in localised CD4 target cells, and persistence for up to two months after the healing of HSV lesions.

All HIV-positive partners entered the study with CD4 counts >250 cells/mm3 and were not on treatment. Over two years, approximately 10% of study participants required HIV treatment for their own care, and this allowed for the HIV transmission rates to be compared by use of ARV treatment. Intensive risk reduction support was supplied throughout the study, to minimise HIV risk for the HIV-negative partners.

People with more advanced HIV at baseline were more likely to start treatment; with higher baseline viral loads (mean 4.4 vs 3.9 log copies/mL, p<0.001), and lower CD4 counts (375 vs 540 cells/mm3, p<0.001). A higher proportion of men than women (12% vs 9%, p=0.01) strated treatment, at slightly lower median CD4 counts (192 vs 204 cells/mm3, p=0.05). People starting treatment were also older (mean 35.2 vs 32.7 years, p<0.001).

ART was initiated at CD4 counts <200 cells/mm3 in 52% patients, between 200 and 349 cells/mm3 in 33%, and >350 cells/mm3 in 15% (30% of this group were for prevention of mother to child transmission).

New HIV infections were detected in 151 of the HIV-negative partners, over 24 months of follow-up, with testing and prevention support provided every 3 months. Phylogenetic analysis suggested that slightly less than one third (43/151) of the infections were not from the relationship partner. Five cases were excluded from the transmission analysis due to uncertain use of ARVs.

This left an overall transmission rate in 103 remaining transmissions of 2.1%.

Of these, 102/103 were in the non-ARV group (102/4558 person years; rate 2.24 95%CI 1.82-2.72) compared to 1/103 from partners using ARV treatment (1/233 person years; rate 0.37 95%CI 0.09-2.04). This produced an unadjusted relative risk of 0.17 (p=0.037), which became even more significant when adjusting for time on study and CD4 count, showing a 92% reduction in risk: RR=0.08 (95%CI 0.002, 0.57, p=0.004).

The single transmission case occurred in someone whose partner started treatment 18 days before the 9 month assessment, when they were still HIV-negative (details on whether this was by HIV-antigen or PCR testing were not provided), but who seroconverted by the month 12 evaluations. Viral load was undetectable at month 12 in the HIV-positive partner.

Details on CD4 count in the HIV-positive partner showed transmissions at all CD4 levels, with a considerably higher risk when the partner had a count <200 cells/mm3 (rate = 8.79 vs 2.79 at 200-350 and 1.7 at 350-500).

This is likely to be an indirect marker of higher viral load relating to more advanced infections, but surprisingly, the presentation provided no further information on viral load levels of the source partner, other than showing that after a median of 7 months treatment (IQR 3-12months) the median viral load dropped to undetectable, indicating excellent responses.

Importantly, and perhaps showing the positive results from the behavioural interventions, the percentage of visits at which people reported unprotected sex dropped from 6.2% to 3.7% at the pre- and post-treatment visits, respectively, with no change in frequency of sex.

Two other studies at CROI, in a largely MSM population in San Francisco, supported the impact of ARVs to reduce transmission.

Moupali Das-Douglas and colleagues from the San Francisco Department of Public Health and the University of California presented results from a model that estimated values for average and total community viral load (CVL) from 2004-2008 and then compared these with the expected and actual number of new diagnoses over the same period. [4]

Average CVL was defined as the mean of the most recent viral load of all reported HIV-positive individuals in a particular population, divided by the number of reported HIV-positive individuals in the population. Total CVL was the sum of the most recent viral loads of all HIV-positive individuals in a particular population.

The context for this study was an effective ‘test and treat’ programme that from 2004 to 2008 increased the percentage of MSM testing within 12 months from 65% to 72% and within 6 months from 41% to 53%. The percentage of HIV-positive MSM unaware of their status dropped from 24% to 14.5% (comparable UK figures vary from 30-50%). By 2008, 90% of patients in care were on HAART, with 72% virologically suppressed (<75 copies/mL).

The decreases in mean CVL and reductions in actual diagnoses (from 798 in 2004 to 434 in 2008) were both statistically significant (p=0.005), as were the decreases in total CVL (p=0.019) and percentage of virologically suppressed patients (p=0.002). The presentation acknowledged that a limitation in these results is that cases may be diagnosed chronic rather than new infections, which was addressed in methodology for expected and actual incidence rates.

However, using a more conservative meta-regression analysis (different to the reported abstract), the 30% reduction in CVL and almost 40% reduction in incidence (rather than cases) was not significant (p=0.3) due to the degree of imprecision in the estimates.

While this makes it too early to link CVL with incidence, the reductions in newly diagnosed and reported cases, at the same time as increased testing, greater ARV coverage and greater virological suppression strongly support close following of subsequent data from this model.

In a related poster, Edwin Charlebois and colleagues modeled the impact of earlier treatment and broader test and treat programmes in San Francisco, suggesting that HIV prevalence could fall from the current 25% to around 10% by 2030 if the programme shifted to universal test and treat. [5]

As this issue of HTB went to press, a policy shift in San Francisco to offer HIV treatment to all newly diagnosed patients, regardless of CD4 count or viral load, was announced by public health officials. [6]

comment

The positive correlation between viral load and risk of transmission for every route, whether sexual, from shared injection equipment, during pregnancy, at birth and from breast milk, and from needle stick exposure to health workers, is now convincingly demonstrated.  For some of these transmission routes, antiretroviral treatment to reduce viral load is already widely used to reduce transmission (principally for mother to child transmission, PEP and PEPSE).

Treatment dramatically extends life, reduces morbidity and should now be additionally valued for reducing transmission. An estimated 70% of HIV-positive people globally in need of immediate treatment for their own care are still unable to access it.

References:

Unless stated otherwise, all references are to the Programme and Abstracts of the 17th Conference on Retroviruses and Opportunistic Infections. 16-10 February 2010, San Francisco. All oral abstracts are available as webcasts.

http://www.retroconference.org

1. Williams B and Dye C. Put your money where your model is: ART for the prevention and treatment of HIV/AIDS.  Webcast: Guiding the global response. Tuesday 2.30pm.

http://www.retroconference.org/2010/data/files/webcast_2010.htm

2. Granich RM et al. Universal voluntary HIV testing with immediate antiretroviral therapy as a strategy for elimination of HIV transmission: a mathematical model. The Lancet, Volume 373, Issue 9657, p48-57, 3 January 2009. doi:10.1016/S0140-6736(08)61697-9.

http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(08)61697-9/abstract

3. Donnell D et al. ART and risk of heterosexual HIV-1 transmission in HIV-1 serodiscordant African couples: a multinational prospective study. 17th CROI 2010. Oral abstract 136.

http://www.retroconference.org/2010/Abstracts/39222.htm

Webcast: New Insights into Transmission and Acute Infection. Friday 9.30am.

http://www.retroconference.org/2010/data/files/webcast_2010.htm

4. Das-Douglas M et al. Decreases in community viral load are associated with a reduction in new HIV diagnoses in San Francisco. 17th CROI 2010. Oral abstract 33.

http://www.retroconference.org/2010/Abstracts/38232.htm

Webcast: Testing and Transmission. Wednesday 9.30am.

http://www.retroconference.org/2010/data/files/webcast_2010.htm

5. Charlebois E et al. Effect of Expanded ART Strategies on the MSM HIV Epidemic in San Francisco. 17th CROI 2010. Poster abstract 996.

http://www.retroconference.org/2010/Abstracts/39042.htm

6. San Francisco endorses starting HIV treatment immediately after diagnosis. (5 April 2010)

http://www.aidsmeds.com/articles/treatment_HIV_diagnosis_1667_18253.shtml

The protective mechanism for reducing heterosexual HIV transmission to circumcised men has been attributed to two factors relating to the properties of the inner foreskin:  a thinner keratin layer reducing the physical barrier and a higher concentration of CD4 and Langerhans cells that are primary targets for infection. A third factor may be that the foreskin prolongs the time that fluid that contains HIV remains in contact with genital tissue. In theory, the size of the foreskin should also positively correlate to the risk from these mechanisms, and this is supported by results from a study published in the 23 October edition of the journal AIDS. [1]

HIV infection rates were collected from 965 men in Rakai, Uganda, who were recruited for two randomised circumcision studies. These men were initially HIV-negative and followed for a total of 3920 person years, prior to circumcision as part of the trial protocol. The results from these trials have already been reported. [2, 3]

After circumcision, the foreskin surface area was calculated (length x width; cm2) and infection rates prior to circumcision were calculated by quartile. Men who became infected compared to those who remained HIV-negative were found to have a significantly greater foreskin surface area (mean 43.3 (+2.1) vs 36.8 (+0.5) cm2 (p-0.01).

HIV incidence/100 person years (PY) was 0.80, 0.92, 0.90 and 2.48 for men with foreskin surface areas in the lower (7.0-26.3 cm2), second (26.4-35.0 cm2), third (35.2-45.5 cm2) and upper quartiles (45.6-99.8 cm2) respectively.

The incidence rate ratio (IRR) of HIV acquisition, after adjusting for age, education, religion, number of sex partners and condom use, was significantly higher for men in the highest compared to the lowest quartiles of foreskin surface area (IRR 2.37; 95%CI 1.05-5.31).
There was, however, no significant difference in HIV incidence between the lower three quartiles. In the adjusted analysis, older age (IRR 4.16; 95%CI 1.55, 11.19, and IRR 4.00; 95%CI 1.46, 10.74; for ages 25-30 and >30 respectively, each compared to 15-24 years), lower education level (0.40; 0.18, 0.91; secondary/tertiary vs primary/none) and catholic religion (IRR 0.37; 0.16, 0.82; Catholic vs non-Catholic) were also significantly associated with risk of HIV acquisition.

The authors concluded that their findings, in addition to the observational studies and randomised trials, add plausibility to the hypothesis that the foreskin is a tissue vulnerable to HIV acquisition.

They suggested that minimising retention of residual foreskin tissue after male circumcision using dorsal slit and sleeve procedures rather than the forceps-guided procedure (which leaves 0.5-1.0 cm of mucosal skin proximal to the corona) is a theoretical concern. However, they also reported that they did not observe any increased risk of HIV acquisition among men with smaller foreskin surface areas that were substantially larger than residual tissue retained after circumcision surgery.

COMMENT

While the study states that these findings need to be replicated in other studies, it is difficult to see how this could be supported.

Firstly, although circumcision studies have shown protection against HPV, HSV and syphilis, men primarily want to be circumcised in order to reduce their risk of HIV infection, and should be told if they are HIV-positive at the time of surgery. It is unclear whether the men in this study would have undertaken circumcision, had they been made aware that they had already caught HIV prior to the intervention.

Secondly, now that circumcision had been proven to reduce heterosexual transmission in high prevalence settings, it is difficult to see why participants would be followed for any significant period prior to surgery.

References

1.    Kigozi G et al. Foreskin surface area and HIV acquisition in Rakai, Uganda (size matters). AIDS. 23(16):2209-2213, October 23, 2009. doi: 10.1097/QAD.0b013e328330eda8.

2.    Gray RH et al. Male circumcision for HIV prevention in men in Rakai, Uganda: a randomised trial. Lancet 2007; 369:657-666.

3.    Wawer MJ et al. Circumcision in HIV-infected men and its effect on HIV transmission to female partners in Rakai Uganda: a randomised controlled trial. Lancet 2009; 374:229-237.

Important limitations to the protective benefits from circumcision, prompted by a 2008 WHO review by Robert Bailey and colleagues, of complications during male circumcision in Kenya [1], were discussed in a recent editorial article in the 2 January 2010 journal AIDS. [2]

The original study, available online without subscription, deserves reading in full by anyone rushing to roll-out circumcision programmes on a community level.

The WHO study prospectively followed approximately 1000 men (IQR ~13-15, range 5-21 years), who were circumcised in July-August 2004, who were interviewed about complications 30-89 days after surgery. Twenty-four men were directly observed during circumcision and after 3, 8, 30 and 90 days.

The participants had either a traditional circumcision performed in a village or within a household compound, or a medical circumcision performed by someone the participant considered to be a clinician in a hospital, health centre, dispensary or private office. The researchers also interviewed 21 traditional and 20 clinical people who carried out the circumcisions.

After interviewing approximately two-thirds of participants and directly following the 24 cases, the researchers found very high rates of complications and decided to directly examine and interview the remaining 298 men, (range 45 – 89 days after circumcision).
One or more complications were reported by 35% men circumcised traditionally and by 17% men circumcised medically (OR 2.53; 1.89–3.38; p <0.001). These rates were significantly higher than the approximate 1-3% observed in clinical trials, or in infants circumcised in developed countries.

Although rates for each complication were not given, the most common self-reported complications were excessive bleeding, infections and excessive pain, with bleeding the most common. Pain upon urination, incomplete circumcision requiring repeat surgery, and lacerations of the glans, the scrotum and the thighs were also reported. Many traditional circumcisions continued to bleed and needed medical support.

Infections were equally common among subjects circumcised medically and traditionally. Those circumcised traditionally were more likely to report receiving antibiotics from local practitioners, often from “travelling nurses” with few or no qualifications. These informal practitioners often sold injections to address infections and bandaged the wound after applying gravacine (a talcum powder with penicillin). Whether it prevented infections we cannot be sure, but it tended to cake in the wound, delay healing and result in thick scarring and, in a few cases, permanent discolouration.

In 24% of the traditional cases and 19% of the medical cases, the wound had still not healed after 60 days (p=0.056) in contrast to 96% healed by 30 days in the randomised male circumcision in Kisumu, Kenya.

In the interviews with 298 men, traditionally circumcision was much more likely not to have healed (21% vs 10%, AOR 0.43; 0.22–0.84, p=0.014), to have significant swelling (14% vs 5%, AOR 3.20; 1.27–8.07, p=0.014), to have a culturally unacceptable amount of foreskin remaining (12% vs 3%, AOR 5.32; 1.54–18.31, p=0.008); and to higher trend to have lacerations (17% vs 10%, AOR 1.91; 0.93–3.91, p=0.077), and keloid scarring (17% vs 10%, AOR 1.99; 0.98–4,06, p=0.059.

Compared to developed country settings, delayed healing, swellings and lacerations were also prevalent among those circumcised medically.

The researchers concluded that “extensive training and resources will be necessary to build the capacity of health facilities in sub-Saharan Africa before safe circumcision services can be aggressively promoted for HIV prevention” and that “the rate of serious complications from traditional circumcisions should also serve as an alarm to ministries of health and the international health community that focus cannot only be on areas where circumcision prevalence is low”.

References

1.    Bailey RC, Egesah O, Rosenberg S. Male circumcision for HIV prevention: a prospective study of complications in clinical and traditional settings in Bungoma, Kenya. Bull World Health Organ 2008;86 (9):669-677.

http://www.who.int/bulletin/volumes/86/9/08-051482/en/index.html

2.    Crabb C. Male circumcision to prevent heterosexual HIV transmission gets (another) green light, but traditional circumcision in Africa has ‘shocking’ number of complications. AIDS. 24(1):N1-N2, January 2, 2010. doi: 10.1097/QAD.0b013e32832faec0

A poster from C Kraft and colleagues from the Zambia Emory HIV Research Project reported on the incidence of HIV subtype C reinfection in heterosexual couples infected with genotypically different viruses.

The study aimed to see whether reinfection could be detected, together with the frequency, and any virologic consequences.

Seventeen unlinked couples were screened with a gp41-based heteroduplex mobility assay for reinfection and the results were confirmed by phylogenetic analysis of single genome amplified env genes.

Three cases of reinfection were confirmed, only two of which occurred during early infection. In one case a newly infected partner was reinfected by their chronically infected spouse, and, in the second, reinfection of the seroconverting partner resulted from a second non-spousal transmission. In the third case, reinfection in a chronically infected partner occurred during acute infection of his partner’s unlinked infection.

In two cases, reinfection was accompanied by a 10-fold increase in viral load. Phylogenetic analyses were consistent with rapid recombination between the reinfecting strains in each individual.

The authors concluded “in this retrospective study of a limited number of HIV-1 infected cohabiting couples, superinfection appears to be a frequent event (3/34).

COMMENT

Similar rates of reinfection have been reported in several at least one other heterosexual study, although rates in MSM are still poorly studied.

It may be important that the case reinfection during chronic infection was from a partner in acute infection when vireamia is highest.

Ref: Kraft CS et al. HIV-1 superinfection in cohabiting Zambian heterosexual couples. 48th ICAAC, 25-28 October 2008. Washington. Abstract H-4049.

Two-dose intermittent pre-exposure prophylaxis (PrEP) with Truvada (tenofovir plus emtricitabine) protected male macaques from rectal exposure to a simian-HIV hybrid virus (SHIV) as well as daily Truvada did in an earlier study by scientists from the US Centers for Disease Control (CDC). [1]

But two-dose PReP did not protect all animals in any of the four 6-monkey groups who got the drugs at different times relative to SHIV exposure.

Trials of daily Truvada PrEP are now under way in different human populations at high risk of HIV infection. An earlier monkey trial of emtricitabine alone and tenofovir/emtricitabine found better protection from SHIV with the two drugs. [2]

In the new study Gerardo Garcia-Lerma and CDC colleagues rectally exposed 24 male Rhesus macaques to SHIV, a simian immunodeficiency virus with an HIV coat, once weekly over 14 weeks. They split the monkeys into four groups of 6, giving human-equivalent doses of Truvada to each group through a mouth-to-stomach tube at different times:

• Group 1: 2 hours before and 22 hours after SHIV exposure
• Group 2: 22 hours before and 2 hours after SHIV exposure
• Group 3: 3 days before and 2 hours after SHIV exposure
• Group 4: 2 hours after and 26 hours after (postexposure prophylaxis, or PEP)

In a comparison group of 24 untreated monkeys, 23 became infected with SHIV (detected in plasma and blood cells) after a median of 2 rectal exposures (range 1 to 12). In contrast 3 of 6 group-1 animals did not pick up SHIV after 14 exposures, 5 of 6 group-2 animals remained free of SHIV after 14 exposures, 5 of 6 group-3 animals remained uninfected after 14 exposures, and (in an ongoing study) 3 of 6 group-4 animals are free of virus after 12 exposures.

Compared with the untreated macaques, group 1 had a 3.7-fold lower risk of SHIV infection (P = 0.04), group 2 had a 15.5-fold lower risk (P = 0.008), and group 3 had a 14.0-fold lower risk (P = 0.01). Risk of SHIV infection in these three groups did not differ significantly from infection risk in monkeys who received daily Truvada PrEP in the earlier trial. In animals that did become infected, viremia was about 10-fold lower than in control animals. Resistant virus did not emerge in animals whose PrEP failed.

Garcia-Lerma and coworkers speculated “the long intracellular drug half-life of tenofovir and emtricitabine may explain the extended window for protection by the pre-exposure dosing and provides opportunities for different intermittent PrEP regimens.”

In a separate study also reported by NATAP, tenofovir/FTC formulated in a stable vaginally applied gel protected 6 of 6 female pigtail macaques from 20 SHIV exposures. [3]

Source:
http://www.natap.org

References
1. Garcia-Lerma J, Cong M, Masciotra S, et al. Intermittent pre-exposure prophylaxis (PrEP) with oral Truvada protects macaques against repeated rectal SHIV exposures. 3rd International Workshop on HIV Transmission: Principles of Intervention. 31 July -2 August 2008, Mexico City. Abstract 40.
2. Garcia-Lerma JG, Otten RA, Qari SH, et al. Prevention of rectal SHIV transmission in macaques by daily or intermittent prophylaxis with emtricitabine and tenofovir. PLoS Med. 2008;5(2):e28
http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0050028
3. Parikh UM, Sharma S, Cong M, et al. Complete protection against repeated vaginal SHIV exposures in macaques by a combination emtricitabine and tenofovir topical gel. 3rd International Workshop on HIV Transmission: Principles of Intervention. 31 July -2 August 2008, Mexico City. Abstract 41.

Vaginal microbicide research in humans took a recent setback with reports that two products did not protect women from HIV infection. But neither of those microbicides (Carraguard and cellulose sulfate) used antiretroviral agents to ward off HIV.

Urvi Parikh and colleagues at the US Centers for Disease Control (CDC) and Emory University randomized 14 female pigtail macaques to three study groups: 2 received no gel, 6 received a placebo gel (hydroxyethyl cellulose only), and 6 got the tenofovir/FTC gel (5% FTC plus 1% tenofovir, which is equivalent to one Truvada dose, in 2% hydroxyethyl cellulose). [1]

The tenofovir/FTC gel was clear, odorless, viscous, and stable at 37 degrees Celsius for 6 months. Technicians applied the gels vaginally 30 minutes before challenging the monkeys with SHIV, a simian immunodeficiency virus with an HIV coat, at a dose of about 1,160,000 RNA copies. After exposure the investigators used blood tests and polymerase chain reaction to search for SHIV in plasma. The challenges occurred twice weekly for 10 weeks.

Both monkeys who got no gel and 5 of the 6 who got the placebo gel became infected after a median of 3.5 challenges (range 2 to 11). All 6 pigtails treated with tenofovir/FTC before SHIV exposure remained free of infection after 20 challenges (p < 0.005 versus control groups). The CDC team could detect no viral RNA, no proviral DNA, and no viral antibody in any of the 6 tenofovir/FTC-treated animals.

Parikh and coworkers detected low levels of FTC (median 67 ng/mL) and tenofovir (median 22 ng/mL) in plasma samples 30 minutes after vaginal application. Those findings, the investigators proposed, suggest “rapid drug absorption with relatively higher levels of drug remaining in vaginal tissue.”

Ongoing trials are testing oral tenofovir/FTC (Truvada) as pre-exposure prophylaxis in humans, and a separate study at this workshop showed that oral tenofovir/FTC partially protected male monkeys from rectal SHIV exposure. [2] An earlier study of 1% tenofovir without FTC applied rectally in a single high dose found only a 60% protection rate. [3] Double therapy clearly did better in this vaginal trial, but Charles Boucher (Erasmus University, Rotterdam) worried about the wisdom of developing drugs for both prevention and treatment because acquired resistance could compromise use of those and other drugs.

A vaginal tenofovir/FTC gel has yet to be tested in humans.

Source:
http://www.natap.org

References
1. Parikh UM, Sharma S, Cong M, et al. Complete protection against repeated vaginal SHIV exposures in macaques by a combination emtricitabine and tenofovir topical gel. 3rd International Workshop on HIV Transmission: Principles of Intervention. 31 July -2 August 2008, Mexico City.
Abstract 41.
2. Garcia-Lerma J, Cong M, Masciotra S, et al. Intermittent pre-exposure prophylaxis (PREP) with oral Truvada protects macaques against repeated rectal SHIV exposures. 3rd International Workshop on HIV Transmission: Principles of Intervention. 31 July -2 August 2008, Mexico City. Abstract 40.
3. Cranage M, Sharpe S, Cope A, et al. Pre-exposure prophylaxis in macaques against rectal SIV challenge by mucosally applied PMPA: potential for complementation of microbicide and vaccination strategies. 14th Conference on Retroviruses and Opportunistic Infections. February 25-28, 2007. Los Angeles. Abstract 29.

Most new HIV cases in Quebec, Canada, can be traced to recently infected but still untreated people in the province, according to an 859-person analysis [1]. The study traced genetic links among 56% of viruses from newly infected people, a slight increase from the clustering rate reported in a previous study by the same research group [2].

Mark Wainberg (McGill University, Montreal) analysed HIV-1 pol gene sequences of subtype B virus from 859 people infected within 6 months of first viral sampling from 1998 through 2007. Comparing the sequences through phylogenetic analysis, he classified the viruses as unique, parts of small clusters (2 to 4 linked viruses), or parts of large cluster (5 or more linked viruses). The proportion of viruses that could be assigned to clusters rose from 49% in December 2005 to 56% in June 2007. Of course all HIV infections are linked to at least one other infection, but the source virus cannot always be identified.

Of the 423 unique and small-cluster viruses identified before 2006, 403 (95%) represented dead-end viruses for which no further transmission could be identified. In contrast, viruses in 21 large clusters were parts of growing transmission cascades: The cluster rate grew from 6.6 to 10.3 viruses per cluster over the course of the study.

Viruses carrying mutations that make HIV resistant to nucleosides were less frequent in large clusters (1.2%) than in small clusters (3.4%) or in unique viral samples (7.9%). In contrast, the nonnucleoside mutations K103N/R and G190A were significantly more frequent in large clusters (12.1%) than in small clusters (3.3%) (P < 0.0001).

One immense cluster included 27 viruses harboring the G190A mutation, which made the viruses more than 50-fold resistant to nevirapine. But those viruses remained susceptible to efavirenz and were more than 10-fold hypersusceptible to etravirine (TMC125), the newest NNRTI.

Wainberg concluded that in the population studied, most new HIV infections “arise from untreated persons at early stages of infection, often unaware of their serostatus.” He cautioned that newly infected people with a high viral load who are unaware of their HIV status pose a special risk of onward HIV transmission.

Source:
http://www.natap.org

References
1. Wainberg M, Brenner B, Roger M, Routy J, Moisi D. Impact of clustering on the transmission of HIV-1 variants harbouring drug resistance. 3rd International Workshop on HIV Transmission: Principles of Intervention. July 31-August 2, 2008, Mexico City. Abstract 36.
2. Brenner BG, Roger M, Routy JP, et al. High rates of forward transmission events after acute/early HIV-1 infection. J Infect Dis. 2007;195:951-959.

…In heterosexual couples with enough other risk factors, transmission risk can climb as high as 1-in-10 for penile-vaginal sex and 1-in-3 for penile-anal sex…..heterosexual sex can be a remarkably efficient way to transmit HIV….

One commonly cited estimate of heterosexual HIV-1 transmission risk – 1 infection per 1000 sexual acts – is probably inaccurate because it fails to account for other factors that raise or lower the risk of HIV transmission. [1]

That conclusion emerged from a multi-study analysis by Kimberly Powers (University of North Carolina at Chapel Hill), who pinpointed five variables that have a potent impact on heterosexual HIV transmission. With enough cofactors in play, Powers estimated that men and women risk transmitting the virus once every three times they have insertive sex.

The investigators suspected the 1-per-1000 ratio may be too low to explain raging heterosexual HIV epidemics in many countries, partly because it does not factor in sexually transmitted infections (STIs), HIV disease stage, circumcision, and other variables known to boost or blunt transmission risk. Yet that ratio gets cited time and again in government reports, peer-reviewed studies, and media offerings, leaving the impression that heterosexual coitus is a highly inefficient way of infecting a partner. To get a better handle on sexual transmission dynamics, the North Carolina team systematically searched published studies estimating heterosexual infectivity of HIV-1. Then they used statistical tools to sort out infectivity differences according to risk cofactors.

Powers found 27 studies involving 15 distinct populations. Transmission estimates varied strikingly from one study to the next, depending on these cofactors. Estimates ranged from 0 transmissions after more than 100 penile-vaginal contacts to 1 transmission for every 3.1 episodes of heterosexual anal intercourse. The multistudy statistical analysis weighing the impact of cofactors identified five variables that boosted risk of HIV transmission:

• Transmission 33.8 times more likely with penile-anal sex than penile-vaginal sex.
• Transmission 8 times more likely for uncircumcised versus circumcised men.
• Transmission 6 times more likely with than without a genital ulcer disease.
• Transmission 2.5 times more likely with early versus mid-stage HIV infection.
• Transmission 1.85 times more likely with late versus mid-stage HIV infection.

Powers and colleagues concluded that the 1-in-1000 estimate adequately represents transmission risk only in stable couples with low rates of other transmission risk factors. In other words, 1-in-1000 “represents a lower bound” of a capacious risk spectrum. In heterosexual couples with enough other risk factors, transmission risk can climb as high as 1-in-10 for penile-vaginal sex and 1-in-3 for penile-anal sex.

The investigators encouraged researchers to consider such cofactors in future infectivity estimates, and they advised public health officials and clinicians to emphasise that heterosexual sex can be a remarkably efficient way to transmit HIV. The study will be published next week in Lancet Infectious Diseases.

Source:
http://www.natap.org

Reference
1. Powers K, Poole C, Pettifor A, Cohen M. Rethinking the heterosexual infectivity of HIV-1: A systematic review and meta-analysis. 3rd International Workshop on HIV Transmission: Principles of Intervention. July 31-August 2, 2008, Mexico City. Abstract 14.

An Australian research group, led by David Wilson from the University of New South Wales, Sydney, published a study in the Lancet modelling the potential impact of a low-level residual transmission risk. [1] This was in response to the Swiss Statement relating to low-to-zero risk of HIV transmission when an HIV-positive person had shown a durable response to treatment (> 6 months with viraemia suppressed to <50 copies/mL) and other conditions are met (good adherence, no other STIs etc). [2]

The model looked at the risk of unprotected sexual transmission per act and cumulatively over many exposures, within couples where one partner is HIV-positive and the other is HIV-negative.

They assumed that each couple had 100 sexual encounters per year, and calculated a cumulative probability of transmission to the HIV-negative partner each year. Transmission risk assumptions were based on the Rakai data (a heterosexual Ugandan study from 1991 looking at transmission risks in 415 sero-defferent couples). The Rakai group reported that each ten-fold increment in viral load is associated with a 2.45-fold (95% CI 1.85-3.26) increase in the risk of HIV transmission per sexual contact. [3]

The model used per-transmission rates (from studies that hadn’t factored the impact of viral load) from 0.001 to 0.0005 per exposure and an assumption that on-treatment viral load was 10 copies/mL (see Table 1). Current transmission rates were estimated assuming 80% condom use, and 95% effect protection from condom use.

Table 1: Modelled cumulative transmission risk by type of exposure

This modelling suggested per exposure risk rates from an HIV-positive partner on ARV treatment, fulfilling the above criteria,from 1 in 43,000 for anal sex to less than 1 in 220,000 for vaginal sex and suggested an approximate four-fold increase in risk across all three groups if sero-different stopped using condoms.

While this is interesting, it didn’t closely relate to the motivation behind the Swiss Statement, nor the clinical situations in which they suggested it be applied. These were i) ability to safely conceive a baby without dependence on sperm-washing (a procedure that is
difficult to access or afford and which carries a reduced conception rate) and ii) to allay anxiety and worry over perceived risk of infection during regular sex (using condoms) and in the event of a condom break.

For many HIV-negative partners, single exposure risks of between 1 in 43,000 for anal sex to less than 1 in 220,000 for vaginal sex may often be acceptable in the context of general quality of life for family planning or a less anxious, healthy, sex life.

Importantly, a weakness in the model, from assuming a linear relationship between viral load and transmission was raised both in the original article and in an accompanying comment by Geoffrey Garnet from UCL and Brian Gazzard from the Chelsea and Westminster Hospital, published in the same issue of the Lancet. [4]

Assuming a log-linear relationship that supposes a risk at every level of viral load they argued “extrapolates the model beyond the available data, assuming that there is a continuous reduction in risk rather than a threshold below which no transmission is possible”.

The model doesn’t address the likelihood that most sero-different couples are likely to continue to use both ARVs and condoms, or the additional reduction in transmission risk from ARVs in this setting.

The comment concludes “In many ways, the Swiss statement provides the opportunity for positive public-health messages, by promoting adherence to treatment and concern over other sexually transmitted infections. The use of condoms, in addition to antiretrovirals, to further reduce risk and prevent other sexually transmitted infections can then also be promoted.”

COMMENT

More than ten years after HAART has been able to reduce viral load to very low levels, it is notable that we have no prospective trial results looking at its impact on transmission, on either a population or individual level. Lack of data on whether treatment brings most people below a minimum threshold for transmission is clearly key in any further discussion.

The lack of data on transmission risk for anal sex (heterosexual and MSM) is also worryingly sparse although some research groups are looking to address this, hopefully with funding for sufficiently powered conclusions, and with some urgency.

The focus on ARVs as a prevention strategy, also a key topic at the Mexico conference, is long overdue. Many research groups have highlighted that 25-50% of new diagnoses are likely to be driven by people who are undiagnosed, especially those recently infected when vireamia is highest by a magnitude of several logs. [5-9]

Many groups have also reported that risk behaviour generally falls after diagnosis, especially once patients are within care. [10]

Increased testing, reducing late diagnosis and seeing treatment as protective of both health and transmission risk – rather than as something to delay until as late as possible – are likely to develop as increasingly important themes for managing the HIV epidemic in the 21st century.

References
1. Wilson DP, Law MG, Cooper D et al. Relation between HIV viral load and infectiousness: a model-based analysis.The Lancet: 372, p314-320. ( 26 July 2008).
http://www.thelancet.com/journals/lancet/article/PIIS0140673608611150/fulltext
2. Vernazza P, Hirschel B, Bernasconi E, Flepp M. HIV seropositive persons without sexually transmitted diseases under fully suppressive
antiretroviral treatment do not sexually transmit HIV. Bulletin des médecins Suisses 2008; 89:165-169.
3. Quinn TC, Wawer MJ, Sewankambo N, et al. Viral load and heterosexual transmission of HIV type 1. Rakai Project Study Group. N Engl J Med 2000; 342: 921-929.
4. Garnett GP, Gazzard B. Comment: Risk of HIV transmission in discordant couples. The Lancet 2008; 372:270-271. (26 July 2008).
http://www.thelancet.com/journals/lancet/article/PIIS0140673608610892/fulltext
5. Brenner BG et al. High rates of forward transmission events after acute/early HIV-1 infection. J Infect Dis 195: 951-59, 2007.
6. Hughes G et al. Recent phylodynamics of the HIV epidemic among MSM in the UK 15th Conference on Retroviruses and Opportunistic Infections, Boston. Abstract 13, 2008.
http://www.retroconference.org/2008/Abstracts/31334.htm
7. Yerly S et al. The contribution of individuals with recent infection to the spread of HIV-1 in Switzerland: a 10-year survey. 15th Conference on Retroviruses and Opportunistic Infections, Boston. Abstract 512, 2008.
http://www.retroconference.org/2008/Abstracts/31699.htm
8. Pao D et al. Transmission of HIV-1 during primary infection: relationship to sexual risk and sexually transmitted infections. AIDS. 2005 Jan 3;19(1):85-90.
http://www.ncbi.nlm.nih.gov/pubmed/15627037
9. Pilcher CD et al. Amplified transmission of HIV-1: comparison of HIV-1 concentrations in semen and blood during acute and chronic infection. AIDS 2007 Aug 20;21(13):1723-30.
http://www.ncbi.nlm.nih.gov/pubmed/17690570
10 Metsch LR et al. HIV transmission risk behaviors among HIV-infected persons who are successfully linked to care. Clinical Infectious Diseases 15 August 2008, Vol. 47, No. 4: 577-584.
http://www.journals.uchicago.edu/doi/abs/10.1086/590153

A case report published in Antiviral Therapy in Sepetember is important to inform the discussion on risk of sexual transmission by patients meeting the factors outlined in the Swiss Statement earlier this year (durable viral suppression to <50 copies/mL for >6 months, perfect adherence, no STIs).

Martin Stürmer from the Goethe University Hospital, Frankfurt, and colleagues described the case of a monogamous gay couple where the HIV-negative partner became infected. The HIV-positive partner, diagnosed in January 1999, started AZT/3TC/efavirenz in July 2000, achieving undetectable viral load within four months that was maintained for the next four years.

The man’s partner tested HIV-negative in June 2002 but HIV-positive in July 2004. The couple did not have other partners, but reported having unprotected sex from May 2003.

Phylogenetic analysis showed close relationship between the two viruses and ruled out the source of infection being a third party. Throughout the period, the HIV-positive partner reported good adherence, with no STIs, confirmed by his medical records.

The authors concluded “this should be added to the discussion of prevention strategies, which should not advise the abandonment of safer-sex practices without referring to the relatively low but not impossible risk of HIV-1 transmission in this context”.

COMMENT

Accurate, verified cases are important because of the lack of post-HAART data on transmission. No one is looking at it and no one is reporting it. One criticism of the Australian paper in the Lancet that modelled population risk from stopping condom use by assuming a linear relationship between viral load and risk, was that there maybe a cut-off level below which no transmission occurs. This case shows that criticism may not be valid for anal sex. We now need to know if there are similar cases for vaginal sex transmission?

Prevention risks are individual. An acceptable risk for one person is unacceptable for another. Without this case everything is theoretical.

With it, you can say that the risk is likely to be real for anal sex.

The report raises two issues for which we need more information: anal sex (most modelling is based on vaginal sex) and viral load in semen (the report below from the sperm-washing service in Paris highlighted 5% discordance between blood and semen).

The conclusions from this case report are different, based on each of the practical example used for the context of the Swiss statement.

Firstly, if trying for a baby, it is important to have semen viral load checked. Secondly, that risks are still very low for serodifferent couples, for example in cases of a single condom break, but not low enough to stop using condoms routinely.

Ref: Stürmer M et al. Case report: Is transmission of HIV-1 in non-viraemic serodiscordant couples possible? Antivir Ther 2008; 13:729.
http://www.ncbi.nlm.nih.gov/pubmed/18771057?dopt=Abstract

In the context of quantifying levels of risk relating to natural conception in sero-different couples in relation to the recent Swiss Statement relating to undetectable viral load and risk of transmission [1], Anne-Geneviève Marcelin from Hôpital Pitié Salpêtrière and colleagues reported rates of discordance between levels of HIV RNA in blood and semen in a cohort of 145 HIV-positive men enrolled in an assisted reproductive (sperm-washing) programme in Paris. [2]

The group, writing in a research letter to the August 2008 issue of AIDS, found that 5% of men in this group had detectable HIV RNA in semen.

264 paired blood and semen samples were collected between January 2002 and January 2008 with some patients providing up to six samples. Viral load was quantified using tests sensitive to 40 copies/mL and 200 copies/mL in blood and in seminal plasma respectively.

Thirty-two blood plasma samples were detectable (median 6,325 copies/ml (range = 222-28,300). Sixteen seminal plasma samples were detectable and the median level of HIV-1 RNA in semen was 1770 copies/ml (range = 255-25,100). Overall, 234 paired samples were concordant, with 225 samples with undetectable HIV-1 RNA both in blood and semen (85.3%) and nine with detectable HIV-1 RNA in blood and semen (3.4%). However, 23 blood samples had detectable HIV-1 RNA although the seminal viral load was undetectable and seven seminal samples had detectable HIV-1 RNA although the
blood viral load was undetectable (range 257-1230 copies/mL).

These seven discordant paired samples corresponded to seven distinct patients who had undetectable viral load in blood for greater than six months and no current STIs. Interestingly, 6/7 had undetectable concordant results in blood and semen on at least one occasion during follow-up indicating variability over time. Antiretroviral drug levels in semen showed no relationship between choice of drug and viraemia: 3TC, FTC, tenofovir and indinavir showed higher penetration but were
also included in many of the regimens that these seven patients were using.

The researchers concluded that their findings justify measuring HIV-1 RNA in semen when sero-different couples are planning a pregnancy. They also cautioned that a residual risk of transmission relating to these discordant results should be included in the information available to couples who would like to have unprotected sexual intercourse in the context of conceiving a baby.

COMMENT

It is interesting that level of discordance was intermittent in the seven patients with detectable viral load in semen, and that levels of viral load were generally low (maximum 1200 copies/mL).

As with the previous article, establishing whether a minimum threshold exists for transmission remains a crucial research question.

RNA testing of semen in the context of minimizing risks in the context of conceiving a baby without sperm-washing is clearly an additional safety measure that should be used whenever possible – along with limiting conception attempts to the most fertile days of the woman’s cycle and possibly use of single-doses of tenofovir/FTC PrEP and PEP.

Reference
1. Vernazza P, Hirschel B, Bernasconi E, Flepp M. HIV seropositive persons without sexually transmitted diseases under fully suppressive antiretroviral treatment do not sexually transmit HIV. Bulletin des médecins Suisses 2008; 89:165-169.
2. Marcelin A-G et al. Detection of HIV-1 RNA in seminal plasma
samples from treated patients with undetectable HIV-1 RNA in blood plasma. Research Letter. AIDS:Volume 22(13)20 August 2008p 1677-1679.

The new PLoS Medicine features a study conducted by Martin Cranage and colleagues evaluating tenofovir gel as a potential rectal microbicide in the SIV challenge model. The researchers report that application of the gel two hours prior to exposure to the SIVmac251/32H challenge virus protected six out of nine macaques. Of the remaining three, two showed lowered viral loads post-infection compared to controls. Interestingly, most of the protected animals also displayed detectable SIV-specific
T cell responses even though sensitive assays could find no trace of virus.

The PLoS editor’s summary raises the concern that these SIV-specific T cells may be associated with enhanced susceptibility to infection upon re-exposure; however, Cranage et al note in their discussion that transient tenofovir treatment immediately post SIV infection has been shown to lead to induction of SIV-specific T cell responses, and macaques (http://jvi.asm.org/cgi/content/full/75/21/10187) in this study subsequently resisted both homologous and heterologous SIV challenges. The question of whether the SIV-specific T cell responses observed in Cranage’s study have the potential to be protective can
only be definitively addressed by another experiment in which the macaques are re-challenged with SIV.

An additional implication of these data is that human trials of microbicides and pre-exposure prophylaxis (PrEP) should include monitoring for HIV-specific T cell responses.

Source: TAG Basic Science Blog 06 Aug 2008
http://tagbasicscienceproject.typepad.com/tags_basic_science_vaccin/
2008/08/tenofovir-gel-a.html

Ref: Cranage M et al. Prevention of SIV Rectal Transmission and Priming of T Cell Responses in Macaques after Local Pre-exposure Application of Tenofovir Gel. PLoS Medicine Vol. 5, No. 8, e157 doi:10.1371/journal.pmed.0050157
http://medicine.plosjournals.org/perlserv/
?request=get-document&doi=10.1371/journal.pmed.0050157

A new and complex study has identified a possible genetic influence on susceptibility to HIV acquisition that preferentially impacts Africans and people of recent African descent. [1] The paper is available free on the website of the journal Cell Host & Microbe (link below).

The major points are as follows:

• The Duffy Antigen Receptor for Chemokines (DARC) [2] on red blood cells can bind a slew of different chemokines and also HIV itself (X4-using HIV isolates much more than R5-using isolates).
• A genetic change (called a single nucleotide polymorphism or SNP) can lead to a lack of DARC receptors on red blood cells. This SNP is very common in Africans and people of recent African descent, because it once protected against a form of malaria caused by the pathogen Plasmodium vivax.
• In a large cohort of African American individuals from the US military, having the DARC-negative SNP was associated with a significantly increased risk of having HIV infection, even in multivariate analyses controlling for various confounding variables. However, the confidence intervals on the multivariate analyses ppear to approach a relative risk of 1.0 at the low end (in other words, based on the numbers in this study, it is within the bounds of possibility that the SNP has little impact on susceptibility). The result appears to rest on the finding that perhaps ~60% of 814 HIV-negative African Americans lacked the DARC receptor compared to ~70% of 470 HIV-infected African Americans. [3]
• If the result holds up, the fact the SNP is nearly ubiquitous among African populations could contribute to the higher incidence of HIV infection on that continent (the researchers estimate it might explain ~11%).
• The absence of the DARC receptor is associated with lower levels of CCL5 (formerly called RANTES), a chemokine with strong anti-HIV activity, providing a possible mechanistic explanation of the finding. A prior study has reported that persistently exposed, uninfected sex workers have ten-fold higher levels of CCL5 in the genital tract compared to both infected individuals and uninfected study participants who had recently started sex work and thus had little prior exposure to HIV. [4] Higher CCL5 production has also been reported in highly exposed but uninfected gay men. [5]
• Although at first blush it might sound paradoxical, the absence of DARC was also associated with a slight but significant slowing of disease progression in the HIV-infected members of the study cohort. The researchers suggest that this is likely explained by the association between the presence of DARC and higher levels of proinflammatory chemokines such as CCL2. Once infection occurs, the authors propose, the presence of DARC may exacerbate immune activation due to this association with elevated levels of pro-inflammatory chemokines (immune activation is the single strongest predictor of the pace of disease progression in people with HIV). While this hypothesis remains speculative, the authors argue it is supported by an association they have reported previously; in that case, a SNP that increases CCL2 levels in European Americans was shown to be linked to reduced susceptibility to acquisition of HIV infection and also faster disease progression in infected individuals. [6] Another non-exclusive possibility raised by the authors is that the absence of DARC slows progression by
  preventing transfer of DARC-bound HIV particles to CD4 T cells.

In discussing their results, the study authors acknowledge that there is a possibility that the associations they have observed are connected to an unknown factor or factors that are linked to the DARC SNP, and stress that confirmation of these results in other cohorts will be necessary to ensure they are valid. If it does turn out that there is a protective effect
mediated by elevated levels of CCL5, this information could potentially assist vaccine development, as it would suggest that using adjuvants that elevate CCL5 levels and/or inducing HIV-specific T cell responses that produce CCL5 could be useful strategies for HIV vaccines.

References
1. He W, Neil S, Ahuja SK et al. Duffy Antigen Receptor for Chemokines Mediates trans-Infection of HIV-1 from Red Blood Cells to Target
Cells and Affects HIV-AIDS Susceptibility. Cell Host and Microbe, Vol 4, 52-62, 17 July 2008.
2. http://en.wikipedia.org/wiki/Duffy_antigen_system
3. http://www.cellhostandmicrobe.com/content/article/image?uid=
PIIS193131280800190X&imageid=fig2
4. http://www.ncbi.nlm.nih.gov/pubmed/16088822
5. http://www.ncbi.nlm.nih.gov/pubmed/15166527
6. http://www.ncbi.nlm.nih.gov/pubmed/12374865

Free online access:
http://www.cellhostandmicrobe.com/content/article/fulltext?uid=PIIS193131280800190X

Source: TAG Basic Science Blog. Expression of the Duffy antigen receptor for chemokines may impact susceptibility to HIV infection. (16 Jul
2008).

In the first 7 months after oral fluid testing was introduced, 35 (0.16%) of 21,722 tests were false positive by Western blot, consistent with the 99.8% (95% confidence interval [CI] = 99.6%-99.9%) specificity claim by the manufacturer in the product package insert. However, in October 2005, staff members at the clinics noticed an increase in the number of false-positive oral fluid test results each month.

From an average of five false-positive tests per month, the monthly number of false-positive tests increased to 11 (0.27% of 4,024 tests) in October 2005 and to 36 (0.97% of 3,735 tests) in November 2005 (with a specificity of 99.03%, lower than the lower limit of the manufacturer’s CI specifications).

Despite the increased number of false-positive results, testing with the noninvasive oral fluid specimens was popular with clinic patients and both testing rates and patients returning for results remained significantly higher than before they had been introduced.

However, in the period November 2007 to April 2008, nearly half of reactive oral fluid tests in the STD clinics were false positive, prompting a shift to using rapid finger-stick tests.

The information highlights the importance of confirmatory testing, as required by product labeling, to confirm both oral fluid and whole-blood reactive rapid HIV tests.

Before testing, all patients should be informed that reactive rapid HIV test results are preliminary and require confirmation. In general, testing with blood or serum specimens is more accurate than testing with oral fluid and is preferred when feasible, especially in settings where blood specimens already are obtained routinely.

The complete article is available on the CDC web site at:
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm57e618a1.htm?s_cid=mm57e618a1_e

A list of the FDA-approved rapid HIV antibody screening tests is available at:
http://www.cdc.gov/hiv/topics/testing/rapid/rt-comparison.htm

Overview of epidemology studies

Several epidemiological studies contributed to a generally optimistic atmosphere at the workshop, by suggesting that the potential for widespread multi drug resistance has generally been limited, and that rates of resistance to 2- or 3-classes of drugs may be still remain consistently low.

Trends in resistance, as expected, generally mirror changes in ARV use, with prevalence of PI-associated mutations dropping as NNRTI-based regimens became more widely used – and within class changes – generally reduction in TAMS and ddI-related mutations and an increase in K65R reflecting wider use of tenofovir. Similarly, D30N decreased and I50L increased reflecting lower use of nelfinavir and higher use of atazanavir. As usual, regional and national variations were reported among studies. [1, 2, 3]

However, lower prevalence in many of these cross-sectional studies, may miss the cumulative increase of resistance, that would be picked up from longitudinal studies. The importance of this methodology was raised at the 2004 Workshop by researchers from the UK-CHIC cohort. [4]

The importance of collecting longitudinal data tracked in individual patients, was addressed by Akash Shah from Yale University in a poster at this years meeting, which reported longitudinal retrospective data (every 6 months) from around 400 US patients enrolled in the two clinics in Connecticut. [5]

Although complete data from month 0, 6, 12, and 18 was only available for 396, 204, 153 and 84 patients respectively, the cumulative presence of resistance increased from around 32% to 46% in patients with 18 months data (p=0.08), and from 31% to 50% in patients with 12 months data (p=0.001). The study reported that genotypic resistance increased at approximately 5% per 6 months, but with current follow-up appeared to plateau at 50%.

Previous presentations from the UK CHIC group showed cumulative resistance to a single drug of approximately 10% occurring every two years, and importantly linked this to a similar increase in risk of virological failure over a similar period. While incidence of 3-drug resistance was ~1% the cumulative risk of 3-drug resistance increased to ~4% over 6 years. [4]

In looking at the results from the following studies that reported a generally stable incidence of resistance, including multi-drug resistance, it is important to bear these methological differences in mind.

Lisa Ross and colleagues from GSK presented results from the largest US prevalence study at the meeting, with samples from 1795 treatment naïve patients from 33 states, who enrolled into clinical trials from 2000-2004. [6]

Incidence of IAS mutations for this cohort was around 10% (2000/2004: 5/13% – NRTI 3/4%, NNRTI 2/7%, PI 2/5%, by year). Geographical differences were reported for increases in the South (4/14%) and Northeast (8/16%) compared to more constant incidence in the Midwest (10/10%) and the West (6/6%). While multi-class resistance mutations didn’t increase over time in this cohort the incidence of overall resistance doubled from 2000 to 2004 in the South and Northeast.

Viktor von Wyl and colleagues from the Swiss cohort presented data from just over 2,500 patients, followed for over 6,000 patient years, and with 1443 resistance tests linked to treatment failure. [7] They reported no increasing trend over time of resistance to one or more drug class, and that the prevalence of triple class resistance slightly fell over a five year period from 1999. However, a second Swiss study from the same research group, looking at around 10% of all recent infections from 1996 to 2005, while reporting a generally stable rate of transmission of resistant virus (NRTI being highest at 5.8%, and 2- and 3-class resistance present in 1.8% samples), did report a significant increase in NNRTI transmitted virus in 2005. [8]

Deenan Pillay and colleagues calculated the viral burden of drug resistance in a largely MSM clinic cohort of 1482 patients in follow-up from 1998 who had median of 9 viral load results, and a total of almost 500 resistance tests. [9]

Looking at common mutations (at 41, 103, 184 and 215 in RT; and at 90 in protease) they multiplied presence of each mutations by related viral load, accounting for differences over time, and calculated an overall burden of 6.8% resistant virus. This proportion reduced over the study period (2000-2003). The relative frequency of specific mutation burden in the cohort was T215any > M41L > K103N > M184V > L90M. Over the same period, resistance was transmitted to 24/150 acutely infected individuals, with frequency of K103N > 215any > M41L > L90M and no cases of M184V. The viral burden of resistant virus has fallen during this period, with greater viral control, and the researchers used this data to support an optimistic prediction that the transmission of resistance is likely to continue to fall.

Hong-Ha Truong and colleagues from San Francisco reported a reduction of drug resistant in just over 100 recently diagnosed individuals in 2004 (8-12% depending on site) compared with rates in 1996-2001 of between 18 and 27% depending on year. [10] Data from 2004 came from a primary HIV infection study and from patients seen at STD clinics, but showed no statistically significant differences between the two settings.

In Europe, Annemarie Wensing from Utrecht Medical Centre, and the EU-sponsored SPREAD programme, reported that prevalence of resistance in recent diagnoses was 9.1%, most of whom (71%) showed only single mutations (although acknowledging that viral reversion could underestimate these rates). [11]

These findings were from almost 1100 patients, recruited prospectively and diagnosed during 2002-3 in 17 European countries. The prevalence of NRTI, NNRTI and PI mutations was 5.4%, 2.6% and 3.0%. Interestingly, people from high prevalence countries had half the risk of transmission of drug resistant infection (OR=0.49; 0.24-0.99, p=0.046). 52% of resistant virus included a mutation or mixed virus at RT 215. 1.3% of patients were infected with three-class resistant virus.

Susan Little and colleagues from University of San Diego, California, reported an increasing in transmission of NNRTI resistance in North America and Australia in a cohort of 1535 patients who were largely male (94%), non-Hispanic white (70%) and who were diagnosed with recent infection following sexual exposure. [12]

Genotype and phenotype results were available for almost 1200 and 1000 patients respectively, with 650 patients having results from both tests. When comparing the periods 1995 to June 2000 and July 2000 to 2006, they found high level NNRTI resistance increased from 6 to 11% (p=0.014), although overall resistance did not (9 to 15%, p=0.096). The group reported higher NNRTI resistance in the Californian patients (compared to New York or other areas), and that a decrease in NRTI resistance was only significant in New York. MDR remained stable at 2-4%, by both genotype and phenotype, throughout the study.

Methamphetamine use linked to transmission of drug resistance

A second presentation from Susan Little’s group, reported results from a preliminary study, that linked use of recreational drug methamphetamine (crystal meth) with acquiring drug-resistant HIV. [13]

Among 214 MSM diagnosed with recent infection between 2002 and 2006, and who completed self-assessed interviews on substance use, 12.6% had transmitted drug resistance. Among those with drug resistance, 19% reported use of methamphetamine and 9.5% did not, and this was statistically significant in a multivariate analysis (OR=4.29, p=0.01). Use of other substances was not significant, though annual income (>$10k, or $10-30k, compared to >50k or higher) had a similar impact.

Joe Eron from University of North Carolina, looked at prevalence of triple-class resistance (defined as at least one mutation to each of the NRTI, NNRTI and PI classes) in a cohort of just under 1600 treatment-experienced patients, half of whom (n=789) had been exposed to 3 classes. [14]

The first treatment for 50% of these patients had been 3-drug HAART, with 20% and 30% having started with either dual- or monotherapy respectively. In 609 patients with genotype results, the overall prevalence of triple-class resistance was 20%; but this was only 10% in HAART initiators (over median 4 years follow-up) compared to 26% in patients who first treatment was mono- or dual-therapy. Only the number of prior ARVs and non-HAART exposure were independent predictors of triple-class resistance.

Transmission of resistance to T-20

Bernard Masqulelier from Laboratoire de Virologie, CHU de Bordeaux, reported on 56 recently infected (seroconversion during 2004-2005) treatment-naïve French patients in the Aquitaine cohort, and reported an overall prevalence of 16% transmitted resistance. Importantly, they reported the first two cases of transmission of resistance to T-20 (enfuvirtide). [15]

The first case had N42D mutation in the HR region of gp-41, along with additional mutations in protease (D30N, M36I, N88D) and RT (M41L, L210W, T215D). Phylogenetic analysis from the sexual partner (who was also treatment naïve) showed the same genotype, suggesting consecutive MDR transmission. The second case had G36D mutation in the HR1 region, with no additional protease of RT changes.

The authors suggested that broadening the genotype range to include resistance to fusion inhibitors is important for surveillance studies, and that genotyping the gp-41 region should be considered before starting patients on T-20.

Finally, Mark Oette from University of Düsseldorf, prospectively tested 831 patients who started their first HAART regimen from 2001-2005. [16]

Pre-treatment samples with resistance increased from 4.8% in 2001, to 7.3%, 8.7%, 11.6% and 9.0% in each subsequent year to 2005, although this trend did not reach statistical significance. Importantly, the researchers concluded that further surveillance of primary drug resistance was essential, and that genotypic resistance testing prior to starting HAART should be regarded as standard of care for all patients.

Similarly, Davey Smith and colleagues, after reporting one of the highest prevalence of resistance in newly diagnosed individuals (24.5% in 106 new diagnoses), reported that modeling healthcare costs and showed that resistance testing was at least as cost-effective as other healthcare interventions, when resistance in treatment-naive patients was 8-10% or higher. [17]

References:

Unless stated otherwise, all references to abstracts relate to the Programme and Abstracts from the XV International Drug Resistance Workshop, 13-17 June 2006, Sitges, Spain. The abstract book is published as a supplement to Antiviral Therapy 2006, Volume 11.
1. Balotta C et al. Study of antiretroviral resistance in treated patients with virological failure (START study): an Italian survey over the period 2003–2005. Abstract 119.
2. Kagan R et al. Newer antiretroviral treatment regimens drive HIV-1 RT and PR mutational patterns in a national reference laboratory database. Abstract 120.
3. Camacho R et al. Rise and fall of the RT K65R incidence in the Portuguese resistance database. Abstract 121.
4. Collins S. Resistance in the UK: new approach to epidemiological studies. HIV Treatment Bulletin, July 2004.

http://www.i-base.info/pub/htb/v5/htb5-6/Resistance.html

5. Shah AD et al. Cumulative prevalence of HIV drug resistance in HIV+ patients in 122 clinical care. Abstract 122.
6. Ross L et al. Prevalence of HIV-1 drug resistance-associated mutations in a large cohort of ART-naïve HIV-infected individuals in the United States from 2000-2004. Abstract 107.
7. von Wyl V, Yerly S, Boni I et al. Prevalence of HIV-1 drug resistance in Switzerland between 1999 and 2004: no trend for an increase. Abstract 104.
8. Yerly S, von Wyl V, Boni J et al. Transmission of HIV-1 drug resistance in Switzerland: a 10-year molecular epidemiology approach. Abstract 105.
9. Pillay D, Sabin C, Poa D et al. What is the drug resistance mutational infectious burden in an HIV-1 prevalent cohort and the relationship to incidence of transmitted resistance? Abstract 101.
10. Truong H-H et al. Reduced levels of primary resistance to nRTIs in San Francisco is discernable using two independent sentinel populations. Abstract 102.
11. Wensing AM, Vercauteren J, van de Vijver et al. Transmission of drug-resistance in Europe is characterised by single mutations and revertants. Abstract 98.
12. Little S et al. Increases n transmitted NNRTI drug resistance among recently HIV infected patients from North America and Australia. Abstract 97.
13. Drumright LN, Gorback PM, Little SJ et al. Transmitted HIV drug resistance is associated with methamphetamine use among recently HIV infected MSM in southern California, USA. Abstract 99.
14. Eron J et al. Prevalence and predictors of triple-class antiretroviral viral drug resistance in routine HIV primary care. Abstract 78.
15. Masqulelier B, Peuchant O, Capdepont S et al. Primary resistance of enfuvirtide in recently infected, antiretroviral naïve patients, ANRS CO3 Aquitaine Cohort. Abstract 95.
16. Oette M, Kaiser R, Däumer M et al. Trends of primary drug resistance in chronically HIV-infected patients in Germany, 2001-2005. Abstract 112.
17. Smith D, Pesano R, Cachay E et al. Prevalence of HIV drug resistance among antiretroviral naive individuals of unknown infection duration. Abstract 108.

Walid Heneine from CDC Atlanta, presented results showing that adding FTC to tenofovir provided greater protection against SIV infection that standard dose tenofovir. A separate study with FTC monotherapy found an independent protective effect.

Six rhesus macaques were injected subcutaneously with 22 mg TDF and 20 mg FTC per kg once daily, started nine days prior to HIV exposure, and untreated six animals were used as a control group. The FTC dose is comparable to standard human dose, and tenfovir exposure was slightly higher. All animals were exposed rectally with SHIV comparable to viral load levels found in semen during acute HIV infection. Historic data on control macaques using this repeat exposure model shows that 4 virus challenges infect ~75% of the animals.

Of 6 controls, 4 (67%) became infected after 4 challenges (median = 2.5; range = 2 to 4). In contrast, all 6 animals treated with TDF/FTC were fully protected. After 10 additional virus challenges, 1 of 2 remaining controls became infected while all 6 TDF/FTC-treated animals remained uninfected.

The experiment was repeated using FTC monotherapy, with up to 10 HIV exposures, with one animal becoming infected at week 5 and another at week 10. Surprisingly, resistance data on the first animal remained wild-type with no M184V after a further 5 weeks monotherapy.

COMMENT

Studies are clearly required to understand whether a similar level of protection would be provided for adults. In this study the theoretical advantage of dual therapy appeared to result in reduced transmission.

Ref: Heneine W, Garcia-Lerma J, Qari S et al. Prevention of Rectal SHIV Transmission in Macaques by Tenofovir/FTC Combination. 13th CROI. Abstract 32LB.

Jeffrey Johnson and colleagues from CDC Atlanta and the University of California performed longitudinal resistance tests on plasma sample from eleven SIV-infected macaques, receiving 30mg/kg tenofovir daily using a test sensitive to 0.2% mutant virus.

K65R was detected after one week in 4 animals, and by week 6 in another 4 animals. All animals had a one-week treatment interruption at week 6. The remaining 3 macaques developed K65 by week 9.

Mutations were originally at frequencies too low to be detected by population sequencing (~1-10%) in 5 or 11 animals, but increased to sequence-detectable levels 2 to 4 weeks after their initial identification by the real-time PCR assay.

The researchers concluded that ’despite the high fitness cost conferred by the K65R mutation, resistance can emerge rapidly’, and that ‘this may have implications for people who become infected with HIV while using tenofovir pre-exposure prophylaxis.

COMMENT

The emergence of K65R over such short periods in most of these animals, is too rapid to be detected by any real world monitoring within human trials.

This increases the importance of treatment programmes to be established in trials of tenofovir pre-exposure prophylaxis (PrEP), especially as the human trials are proposed in high-risk populations.

It would be very important to know whether the addition of FTC provided any level of protective benefit, as anecdotally, Truvada is being used instead of tenofovir therapy, when used off-label as chemoprophylaxis.

Ref: Johnson J, Van Rompay K, Delwart E et al. Rapid emergence of drug-resistant SIV in tenofovir-treated macaques: implications for tenofovir chemoprophylaxis against HIV. 13th CROI, Denver, 2006. Abstract 609.

Steve O’Brien of the NCI reviewed the understanding gained by his group and others over the past decade on human genes which either reduce or increase the transmission of HIV and the progression of HIV infection to AIDS.

The best known protective human genetic trait is the “delta 32” deletion in the chemokine receptor CCR5. Along with the CD4 receptor, HIV requires a chemokine co-receptor, most often CCR5 to enter cells. About 1% of white Northern Europeans carry a 32-base pair deletion (termed delta 32) of CCR5 on both copies of their CCR5 genes that does not impair immune function but prevents infection by CCR5-using strains of HIV. Phylogenenetic have shown that this mutation occurred after migration of humans from Africa to Northern Europe.

Linkage disequilibrium analysis suggests that the delta 32 event happened about 700 years ago, around the time of the Black Death, an epidemic of plague in Europe. Studies in transgenic mice in whom the CCR5 gene has been disrupted and expression of CCR5 is “knocked out” have shown that yersinia pestis, the plague bacteria, replicates with 30-fold lower efficiency in the macrophages of these mice. So it is argued that the Black Death exerted a selective pressure on Northern Europeans, resulting in some who carry a gene that generations later provides protection against a second, viral, plague.

Since the discovery of the delta 32 CCR5 mutation, at least 4 other mutations have been described that affect CCR5 receptor, and several other human leukocyte antigen (HLA) markers have been found that regulate T cell function and either increase or decrease risk of acquisition or progression of HIV. Six variations in genes related to the innate immune system (primitive immune responses not enacted by T or B cells) have also been described that alter the risk of HIV infection or disease.

O’Brien and others have searched for relationships between known human genotypes or haplotypes for relationships to the risk of HAART failure, post-HAART survival, and HAART-related toxicities. Many genetic markers have been found that have a statistical relationship to increased or decreased risk of progression to AIDS after HAART. However, thus far, these relationships are very complex, and it is not yet possible to guide clinical practice by genetic screening. However, this is certainly the goal of this work in the future.

O’Brien’s group is now studying 332 single nucleotide polymorphisms (single site DNA variations in the human genome) within 8 known ARGs in a sample of over 2600 HIV-infected patients. The group hopes to construct a genetic map to predict risk of HIV disease and complications. The group is working out methods and controls for this endeavor, but O’Brien is optimistic that a genome-wide scan for useful ARGs can be performed.

Overall, various genetic markers, or AIDS restriction genes (ARGs) can be shown to increase the relative risk (>2.0) of morbidity and mortality in HIV infection. That is to say that those with such genes have a 2-fold increased risk of morbidity or mortality despite HAART. However, only about 10% of the total risk is explained by ARGs. This is similar to studies attempting to predict the risk of lung cancer, in which factors such as smoking increase the risk of lung cancer greatly, despite the fact that most smokers do not get lung cancer.

Ref: O’Brien S. AIDS Restriction genes: discovery, assessment and implications. Plenary lecture Tuesday 7 February, 13th CROI, 2006, Denver. Webcast available on conference website.

Source: www.natap.org

Tom Quinn of Hopkins and the NIAID reviewed the maturing data that show that male circumcision confers protection against HIV infection. The biological basis for the protective effect of circumcision is not clear, but the foreskin is not keratinised and heavily enriched in dendritic cells, making it a potentially advantageous entry site for the virus. Quinn reported a number of epidemiological facts that suggested circumcision protects against HIV infection:

• The relative risk of HIV infection was 0.56 in circumcised men.
• The relative protective effect is even greater in men with high-risk demographics, in whom the relative risk in circumcised high-risk men for acquisition of HIV was only 0.29.
• Countries in which >80% of the men are circumcised have lower HIV prevalence than countries in which <20% of the men are circumcised.
• In a cohort of HIV sero-discordant partners in Rakai, none of 50 circumcised men acquired HIV, irregardless of their partner’s viral load.
• Kenyan truck drivers are 2.5-fold more likely to be HIV infected if uncircumcised
• In circumcised Indian men presenting to STD clinics, 88% did not acquire HIV despite the fact that their acquisition rate of HSV, syphilis and GC rates were the same as uncircumcised men This hypothesis has been preliminarily tested in a South African study in which sterile circumcision was provided to a cohort of at-risk men. A 75% reduction in HIV acquisition risk was reported, with 58 adverse events (3.8%) related to the procedure. The study’s conclusions are limited, as follow-up is so far short-term, protection was incomplete, and it is unclear if these results could be generalised outside of southern Africa. Two other studies are expected to be reported in the summer of 2006.

Quinn suggested that as a public health measure safe circumcision should be made available now, and further data developed. In a model of the effect of circumcision, a 50% reduction in relative HIV acquisition risk would cut HIV incidence from 0.8 per 100 person years to 0.4 in women, in addition to the 50% protective effect in men. But if 30% of men believed that sex was now safe and stopped using condoms, the beneficial effect would be abrogated.

The procedure was estimated to cost $69 in Rakai, and therefore would cost 1000 to 3000$ per HIV case prevented. This cost is similar to that of nevirapine prophylaxis for pregnant mothers, in which the cost of an averted infection is estimated to be $2500. Quinn felt that overall circumcision could reduce HIV and STD transmission, reduce cervical cancer, balanitis, and penile cancer. He suggested that preparations be made to offer safe surgery and educate to maintain low-risk behavior.

Ref: Quinn T. Circumcision and HIV transmission: the cutting edge. Plenary lecture Wednesday 8 February, 13th CROI, 2006, Denver. Abstract 120. Webcast available on conference website.

Source: www.natap.org

Topical microbicides, preparations able to kill HIV on contact and prevent infection, are a critical complement to vaccines and other prevention strategies. They can protect women, for example, who cannot protect themselves by other means. Gels are in development and testing, but a plan is needed for future approaches if the results of trials expected in 2006-07 are not encouraging.

John Moore of Cornell provided an excellent overview of what is needed in the field. A microbicide must be safe, effective, affordable, and acceptable. To accomplish this, a preparation must not damage the epithelium, not alter bacterial flora, and must not cause inflammation (as has led to increased HIV transmission following the use of past microbicides).

Several HIV reverse transcriptase inhibitors, AZT-like drugs, are in development. Among them are TMC 120, UC781, and tenofovir. Reagents that block chemokine receptors such as cyanovirin, psc-rantes, and others are under study. In the SIV model, PSC-Rantes formulated in a gel protected monkeys from vaginal and rectal challenge, and did not induce inflammation. The “triple-therapy” of compound 167 (a Merck CCR5 inhibitor), combined with BMS 387806 (a CD4-blocking molecule from BMS), and c52L (a T-20 like fusion inhibitor molecule produced in engineered bacterial) were tested by Ron Veazey in macaques treated with progesterone to enhance their susceptibility to infection.

8/10, 6/8, and 3/5 monkeys were protected by each agent. 16/20 given two agents, and all 3/3 given all 3 agents were protected from high-dose HIV mucosal challenge. In a delayed challenge SHIV (a SIV-HIV hybrid) experiment, microbicides were 80% effective 30 minutes after application, but only 33% protective at 12 hrs. 2 of 5 animals were protected against 5 daily high-dose challenges by daily triple application.

In addition to being effective, microbicides must be affordable. Moore estimated that a product could only cost $0.25-0.50/application. This is a challenge as the amount of compound needed to be effective varied from as little as 3 mg/application to 50 mg. Compounds must reach the millimolar range to protect in the monkey model, which is several-fold higher than in vitro models. In general, receptor blockers need to achieve higher concentrations than antivirals.

In the real world, the challenges will be great. Viral load (innoculum) is likely to be high in many settings as transmission is associated with other active STDs. A product requiring daily application is unlikely to achieve perfect adherence. The cheapest candidates as polyanion detergent-like antivirals at <0.01$ dose, antiviral drugs come in at $0.01-0.10/dose, and small peptides or molecules are the Rolls Royce at $1-20/dose. An interesting idea that Moore mentioned was Dean Hamer’s proposal to engineer live bacterial flora to secrete antivirals, a clever and interesting idea that would need proof of concept in a model system, and acceptance by the public.

Ref: Moore J. Preventing HIV transmission by topical microbicides. Plenary lecture Wednesday 8 February, 13th CROI, 2006, Denver. Abstract 121. Webcast available on conference website.

Source: www.natap.org

In an important proof of concept study, Nicolas Nagot and colleagues from London School of Hygiene and Tropical Medicine, investigated whether HSV suppressive treatment could impact on HIV transmission.

The study randmised 140 women who were coinfected with HIV and HSV and not eligible for ARV treatment, in a 1:1 ratio, to either 1g valacyclovir (VACV) daily for 3 months or placebo. Patients were followed for 3 months prior to randomisation and for the 3 month study duration, with HSV DNA and HIV RNA shedding measured by PCR from cervical swabbing every two weeks.

Mean CD4 count at baseline was 519 and 482 cells/mm³ in the VACV and placebo groups respectively, Overall visit attendance was reported as 93% and treatment adherence as 97%.

The reduction in HIV-1 RNA genital shedding was significantly greater in the VACV group than in the placebo group (–0.26 vs +0.09 log copies/mL, p = 0.003). HIV-1 shedding was significantly less persistent in the VACV group (14.3% vs 27.1% shed at each visit; 27.1% vs 44.3% shed at ≥50% of visits; 32.9% vs 14.3% shed at <50% of visits; and 25.7% vs 14.3% never shed, p = 0.007). HIV-1 plasma viral load was also reduced in the VACV group ( – 0.39 vs +0.12 log copies/mL, p <0.001), as was HSV-2 DNA shedding (–0.22 vs +0.18 log copies/mL, p <0.001). The proportion of women shedding HSV-2 at least once was 18.6% in the VACV arm and 54.3% in the placebo arm (p <0.001).

COMMENT

A meta analysis by Freeman et al of studies in this area concluded that a person with genital herpes is at an approximately 3-fold greater risk of aquiring HIV infection after sexual exposure. [2]

Genital ulcers provide an reduced physical barrier and a higher activation of local CD4 and dendritic cells. If the source partner is coinfected with HIV and HSV they may have higher HIV viraemia in genital fluids and therefore be more infectious.

Previous studies have highlighted the protective effect of VACV treatment on the transmission of HSV to non-nonfected partners [3], and data in this study supporting reduced risk of HIV transmission is clearly important. A similar benefit is likely using the less expensive off-patent acyclovir.

Link

An interesting article on HSV trials to reduce HIV transmission was published in the November 2005 issue of IAVI Vax Bulletin.

http://www.iavireport.org/vax/VAXNovember2005.asp#1

References

1. Nagot N, Ouedraogo A, Mayaud P et al. Effect of HSV-2 suppressive therapy on HIV-1 genital shedding and plasma viral load: a proof of concept randomised double-blind placebo controlled trial (ANRS 1285 Trial). 13th CROI, Denver 2006. Abstract 33LB.
2. Freeman EE, Weiss HA, Glynn JR et al. Herpes simplex virus 2 infection increases HIV acquisition in men and women: systematic review and meta-analysis of longitudinal studies. AIDS 2006;20:73-83.
3. Corey L, Wald A, Patel R et al. Once-Daily Valacyclovir to Reduce the Risk of Transmission of Genital Herpes. NEJM Volume 350:11-20 January 1, 2004.

Previous observational data from over 30 published studies, the earliest dating from 1986, have suggested that men who have been circumcised are at a reduced risk from female-to-male sexual HIV transmission, but up until now this has not been supported by evidence from a prospective randomised trial.

In an oral session Bertran Auvert presented compelling results from the Orange Farm Trial (ANRS 1265) – a randomised intervention trial to assess the effect of male circumcision on HIV incidence among young men in an urban setting close to Johannesburg (‘there are no oranges, there is no farm’). This is an area of high HIV prevalence (31.6%) and largely heterosexual transmission. In an earlier study to determine acceptability, 70% of uncircumcised young men said that they would be circumcised if it could prevent HIV. The local prevalence of male circumcision was 20%.

Participants (n=3,273) were between 18-24 years of age, willing to be circumcised, in good health, and were willing to accept the randomisation and to give informed consent. The trial was designed so participants were randomised directly after screening. Circumcision in the intervention group was performed by medical doctors immediately, using the forceps guided method, with local anaesthetic and post-operative analgesia. In the control group, circumcision was deferred until after the 21-month visit. Both groups had scheduled clinic visits at 3, 12 and 21 months. Approximately 90% of young men in the overall study were sexually active.

After an interim analysis showed a highly significant statistical difference in outcome between the two arms (p<0.0095), the trial was stopped by the study’s Data and Safety Monitoring Board. Circumcision was then proposed to the men in the control group. There were 4664 person years of follow up, with a mean of 17.9 months (IQR 12.7-21.0 months). In the intervention group 4.8% (68/1427) were not circumcised and in the control group 8.4% (92/110) were circumcised. 7.9% of the intervention group and 9.7% of the control group were lost to follow up.

The investigators reported 69 infections overall: 18 in the intervention group (2, 7 and 9 at months 3, 12 and 21 respectively) and 51 in the control group (11, 22 and 36 at months 3, 12 and 21 respectively). The incidence rates were 0.77 (0.49-1.23) and 2.2 (1.7-2.9) per year in the intervention and control arms respectively.

With an unadjusted RR=0.35 (95% CI 0.20-0.60, p=0.00013), the intervention offered 65% protection (95%CI 40-80%). The RR did not vary significantly (RR=0.34, protection 66%) even after controlling for other factors, including condom use and sexual behaviour . Analysis per protocol (ie ignoring the effect of the crossover between the intervention and control arms) the authors reported an unadjusted RR=0.25 and 75% protection.

There was a very low complication rate (3.8%, mainly relating to pain, but with no reports of permanent damage and no deaths. Out of 60/1582 complications pain (n=13), swelling (n=10), excessive bleeding (n=9) and problems with appearance (n=9) were the most frequently reported.

Dr Auvert explained that this is the, “First RCT demonstrating a strong protective effect of safe male circumcision on HIV acquisition by males.” He added that the results were consistent with the expectations of the study but acknowledged that the results were not predictive of the long-term protective effect of circumcision on HIV acquisition. He posed the question whether this strategy should be considered as a public health intervention.

COMMENT

The primary mechanisms for protection conferred by male circumcision were proposed in a study presented at last years Bangkok conference and reported in the HTB coverage from that meeting. [2] These include the high density of CD4-receptor rich langerhans cells near to the surface of the inner foreskin and thicker keratinisation that occurs after circumcision. Additionally the foreskin may provide a humid area to trap HIV allowing for a longer period for transmembrane entry.

There still remains a very low awareness of these mechanisms of infection in prevention interventions and literature, which still misleadingly and implausibly tend to refer to abrasions and cuts rather than the porous nature of membranes, particularly on the glans and foreskin, but also other sexual mucosa.

The protective value of circumcision in this study relates to the context of >30% HIV prevalence in a heterosexual setting for young men. This setting also probably explains the high level of acceptance of circumcision as an intervention. It is not possible to draw conclusions from this study about the effectiveness in other settings, or level of protection in other populations, such as MSM.

It is also important that the circumcision in the study was performed in a medical setting and resulted in no death or serious complications. Monitoring of the safety aspects outside a clinical trial, and appropriate training for practitioners performing circumcision, will also be important if this intervention becomes widely adopted.

The press conference for this study, which can be viewed online, also highlighted the importance of waiting for results from three trials that are already underway in Uganda and Kenya. [3]

References

1. Auvert B, Puren A, Taljaard D et al. Impact of male circumcision on the female-to-male transmission of HIV. 3rd IAS Conference on HIV Pathogenesis and Treatment, Rio de Janeiro, 2005. Abstract TuOa0402.

http://www.iasociety.org/Default.aspx?pageId=11&abstractId=2177418

2. McCoombe SG et al – How HIV enters the human penis. XV Intl AIDS Conference, Bangkok. Abstract MoPeA3048. See HIV Treatment Bulletin, August 2004.

http://i-base.info/htb/8959

3. Webcast of joint IAS/ANRS press conference on the results of an ANRS-sponsored study on the effects of male circumcision on HIV transmission. 26 July. 3rd IAS Conference on HIV Pathogenesis and Treatment, Rio de Janeiro, 2005.

http://www.kaisernetwork.org/rio2005/

McCoombe and colleagues from University of Melbourne presented results of a study designed to determine where HIV enters the penis, hoping to understand the reported lower incidence of circumcised men in many African countries.

They studied the distribution of target cells in the glans penis, frenulum, foreskin and urethral meatus from five uncircumcised penises obtained at autopsy and measured the thickness of the overlying layer of keratin. Keratin potentially prevents HIV gaining access to these penile receptors.

Langerhans cells, dendritic cells, macrophages and T-cells and keratin thickness were studied using histochemical staining techniques and microscopy.

HIV target cells expressing CD4 and CCR5 were found in the inner and outer foreskin, frenulum and glans penis, but at lower levels in the urethral meatus and penile urethra. Dendritic cells, macrophages and T cells expressing these receptors were observed in high densities in the dermis of all regions of the penis except the urethra. HIV susceptible Langerhans cells in the inner foreskin and frenulum were closer to the epithelial surface, but less frequent than in the outer foreskin and glans.

There was little if any protective covering of keratin overlying the inner foreskin and frenulum (Langerhans cells were within 4.5um of the epithelial surface), in contrast to the glans penis and outer foreskin which were heavily keratinized and (rarely coming with 20um of the epithelial surface), thus protecting them from viral entry.

The study concluded that HIV is likely to enter the penis of uncircumcised men via superficial Langerhans cells on the inner aspect of the foreskin and frenulum since these sites are not keratinised. These two area are also highly vascular and most prone to trauma. The major protective effect of male circumcision can best be explained by the removal of most HIV receptor sites in the foreskin and frenulum.

Ref: McCoombe SG, Cameron PU, Short RV – How HIV enters the human penis. XV Intl AIDS Conference, Bangkok. Abstract MoPeA3048.

A large number of observational studies has estimated the average probability of male-female transmission of HIV per unprotected coital act to be 1/384—1/2000 transmission events per coital act during established (ie no-acute) HIV infection.

In a study using survey-based data on sexual behaviours in the United States, Pinkerton et al calculated that these probabilities of transmission per coital act would result in low rates of lifetime transmission (0.190.40 infected partners/man; 0.090.18 infected partners/woman), which, by themselves, could not sustain an epidemic.

The fact that genital fluids (not blood) are the principal vehicles for sexual transmission of HIV presents a particular problem for modeling the likelihood of HIV transmission during acute HIV infection on the basis of blood data. This is because acute HIV infection represents the period of initial establishment of anatomic HIV reservoirs; therefore, the viral dynamics in blood, which have been well described for acute HIV infection, cannot be assumed to apply to the genital tract.

Researchers in the Quest Study Group and the Duke-Emory Acute HIV Consortium examined whether viral dynamics in the genital tract during the natural history of acute HIV-1 infection could explain efficient heterosexual transmission of HIV. The investigators measured HIV concentration in blood and semen samples from patients with acute and long-term HIV infection. They than explored the effect of changes in viral dynamics in semen on the probability of transmission per coital act, using a probabilistic model published elsewhere.

Considered over time from infection, semen HIV concentrations, in men with acute infection, increase and decrease in approximate parallel with changes occurring in blood. Modeling suggests that these acute dynamics alone are sufficient to increase probability of heterosexual transmission by 810-fold between peak (day 20 after infection, based on the model) and virologic set points (day 54 and later after infection). Depending on the frequency of coitus, men with average semen HIV loads and without sexually transmitted diseases (STDs) would be expected to infect 7%-24% of susceptible female sex partners during the first 2 months of infection. The predicted infection rate would be much higher when either partner has an STD. The authors conclude: “Empirical biological data strongly support the hypothesis that sexual transmission by acutely infected individuals has a disproportionate effect on the spread of HIV infection. Acute hyperinfectiousness may, in part, explain the current pandemic in heterosexual individuals.”

The present study provides empirical evidence that men with acute HIV infection are biologically hyper-infectious because of increased genital shedding of HIV. In addition, the present study has provided evidence that, during acute infection, HIV load increases and decreases in semen in approximate parallel with changes occurring in blood, which have been well described. The present model of viral dynamics in semen suggests that, on average, individuals are hyper-infectious beginning before the onset of the acute retroviral syndrome and continuing for approximately 6 weeks thereafter.

© Copyright 2004 by HIV and Hepatitis.com. All Rights Reserved. Reproduction for personal or educational use is encouraged and does not require permission. Written permission is required to re-print copyrighted articles but is almost always granted (emailpublisher@HIVandHepatitis.com).

Ref: Pilcher CD, Tien HC, Eron JJ Jr et al. Brief but efficient: acute HIV infection and the sexual transmission of HIV. J Infect Dis. 2004 May 15;189(10):1785-92. Epub 2004 Apr 28.

Confirmation of the increase in transmission of drug resistance was presented in several studies, and in pooled results in one large European study. The CATCH study (Combined Analysis of resistance Transmission over time of Chronically and acute HIV-infected patients in Europe) whose title doesn’t exactly trip off the tongue provided evidence of an alarmingly high rate of transmission of drug resistance in Europe.

Wensing and colleagues presented results from an analysis of more than 1,400 baseline genotypic samples collected between 1996 and 2002 in 16 countries.

Reverse transcriptase (RT) and protease (PI) sequences were received from the following countries: Austria (60), Belgium (61), Denmark (132), Finland (8), Germany (62), Greece (40), Israel (104), Italy (296), Luxembourg (163), the Netherlands (25), Norway (23), Poland (35), Portugal (124), Serbia-Montenegro (10), Spain (23) and Switzerland (262). Mutations conferring resistance to nucleosides were seen in 6.9% of isolates, resistance to NNRTIs in 2.6% of cases and to PIs in 2.2%. Multi-drug resistant virus was observed in 1.7% of subjects.

Population characteristics were available for 975 samples, and primary drug mutations associated with protease inhibitors and reverse transcriptase were detected in 11% and 9% respectively from these treatment naïve individuals. Primary mutations were detected in 11% (63/596) of seroconverters (infected <1 year) and 8% (30/379) of those with chronic infection. Thirty-one percent of the sequences were classified as non-B and in all countries except Israel, resistance was higher in subtype B sequences than non-B (12% versus 5%).

The UK appears to have higher levels than shown in this European study: the British picture was detailed in an abstract by Deenan Pillay on behalf of the UK HIV Drug Resistance Database – a collaboration between virology laboratories and major clinical centres to pool resistance data in the UK.

Firstly reporting on treatment experienced patients, just over 9,800 test results from around 7,000 patients were available from 1996 to March 2003, and the results were divided into three time periods: 1996-1998, 1999-2000 and 2001-2003. As resistance testing in widely used in early treatment failure, it is not unexpected that around 70% of samples in each period from treatment experienced patients showed at least one key RTI mutation. PI resistance in this group was detected in 26, 32 and 27% of the samples in each period and NNRTI resistance is still increasing in prevalence at 20, 40 and 48% of experienced patients over time – reflecting the prescribing practice for NNRTI first-line therapy in the UK.

Key resistance mutations in treatment naïve individuals (to compare to the CATCH study) were detected in 10, 16 and 17% of samples for the 1998-1999, 1999-2001 and 2001-2003 periods respectively.

comment

These data support the decision in the BHIVA Treatment Guidelines to now recommend baseline resistance testing in the UK for all newly diagnosed individuals, even when immediate treatment is not being considered.

UK guidelines also now recommend resistance testing for chronically infected patients prior to initiation of therapy due to this increasing prevalence and the low cost.

With the high rate of transmitted drug resistance now in circulation this would seem entirely prudent. For those citing cost as an obstacle, deferral of commencement of treatment for just one month will cover the cost of assay.

References:

1. Wensing AMJ et al – Prevalence of transmitted drug resistance in Europe is largely influenced by the presence of non-B sequences: analysis of 1400 patients from 16 countries: the CATCH-Study. XII International HIV Drug Resistance Workshop, Los Cabos, Mexico, 10-14 June 2003. Abstract 117.
2. Pillay D, Green H et al – The UK HIV Drug Resistance Database: development and use for national surveillance. XII International HIV Drug Resistance Workshop, Los Cabos, Mexico, 10-14 June 2003. Abstract 124.

Several abstracts provided additional data on cases of HIV superinfection or coinfection. The term coinfection is usually preferred when there is evidence that the initial infection occurred with two or more different viral strains at the same time, or before an immune response to the first virus has developed. (the latter is sometimes called serial infection).

The term superinfection refers to instances when a second distinct virus infects an individual after they have developed an immune response to the first. The clinical concerns regarding superinfection are essentially twofold. Firstly the second virus may be more virulent and fitter than the initial strain. This may lead to a more rapid disease progression than might otherwise occur with the first virus only. Secondly, it is possible that the second strain may harbour drug resistant mutations, which may compromise the recipient’s future or current treatment options.

On a very basic level the plausibility of coinfection or superinfection is evidenced by the very wide genetic variability of HIV and the frequency of recombinant viral forms in existence. (For viral recombination to occur at all infection of a single cell by two different viruses is required). However, detection of superinfection and coinfection is not straightforward and is an extremely labour intensive scientific process. In fact most cases have only been detected when individuals have been part of intensive primary infection studies. It is unlikely that superinfection will be the focus for large-scale studies and this has perhaps driven some of the scepticism of reporting and discussion.

Perrin and colleagues from the Swiss HIV Cohort Study followed five IVDUs who were either coinfected or superinfected with distinct viral types to study the persistence of different viral strains within a single individual over time. Three patients were coinfected with two different strains at the time of primary infection (sub-type B and Circulating Recombinant Form-11 (CRF-11)) and two patients initially infected with sub-type B and were later superinfected with CRF-11. All patients had been identified from their IVDU cohort, and cases of superinfection had been detected following unexpected clinical events.

The three coinfected patients were followed for 14, 20 and 24 months respectively and subtype specific PCR continued to detect both viruses over this period. Two of these individuals had viral loads >400,000 copies/ml.

The two cases of superinfection were both originally infected with subtype B and had previously controlled their HIV without treatment, maintaining CD4 counts >500 cells/mm3 and viral loads <50 copies/ml for three and five years respectively. Superinfection with CRF-11 in these two cases was associated with high viraemia, rapid CD4 drop and acute retroviral syndrome. Interestingly CRF-11 was the only detectable virus shortly after the time of superinfection and during subsequent monitoring, although both viruses remained detectable in proviral DNA.

Palmer and colleagues provided further details on a patient infected with multidrug resistant virus that was detected during primary infection and reported at the 9th CROI (Daar et al, abstract 96). Within two months of infection, viral load dropped to <1000 copies/ml without treatment but four months after this rebounded to 10,000 copies and at this time point showed no evidence of resistant mutations.

Phylogenetic analysis showed two distinct subtype B viruses at different times after the initial infection. At month one this was entirely resistant virus (0.025% viral diversity) with all sequences containing 69SS insertion and K103N. Subsequent samples at months five, 13 and 17 showed contained a different viral strain and were wild-type with regard to drug resistance associated mutations. Single genome sequencing showed the wild type virus to be almost homogeneous (0.007% sequence diversity) indicating very recent infection (diversity increased to 0.062 and 0.18% at month 13 and 17 respectively).

Phylogenetic analysis showed two distinct subtype B viruses at different times after the initial infection. At month one this was entirely resistant virus (0.025% viral diversity) with all sequences containing 69SS insertion and K103N. Subsequent samples at months five, 13 and 17 showed contained a different viral strain and were wild-type with regard to drug resistance associated mutations. Single genome sequencing showed the wild type virus to be almost homogeneous (0.007% sequence diversity) indicating very recent infection (diversity increased to 0.062 and 0.18% at month 13 and 17 respectively).

Readers interested in tracking these reports will be interested to know of a further two abstracts presented at the IAS meeting.

Burger and colleagues reported the case of a Kenyan woman who was infected prior to 1986 with subtype A virus. Complete RNA sequences from 1995 and 1997 were subtype A/C recombinants and heteroduplex tracking assays were unable to find evidence of subtype C in the 1986 samples.

Manigart and colleagues reported four cases of coinfection from a cohort of 147 commercial sex workers in Burkina Faso, two of which showed two distinct phylogenetic populations existing. Retrospective analysis of stored samples showed that each patient acquired a second virus at the same time that they experienced increases in plasma viraemia.

Although this study commented that superinfection is not an uncommon phenomenon, given the multiple opportunities for exposure, it is also surprising that it was detected as such a low level in the cohort as a whole.

Numerous posters on molecular epidemiology also documented geographical prevalence and development of both new and already recognised populations of recombinant virus within the diversity of HIV infections, including vertical transmission of dual infection.

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These additional cases of superinfection add to the already published literature on this subject (Jost et al NEJM: September 2002; Altfeld et al. Nature. November 2002; Koelsch et al. AIDS May 2003).

They prove beyond doubt that superinfection with a second strain of HIV can occur with detrimental consequences to the individual affected. Several questions remain unanswered. Will superinfection with drug resistant HIV always lead to treatment failure in a person well controlled on drugs? Secondly, just how common is superinfection in day-to-day practice? A recent article published by Gonzalez et al in JID suggests this is a relatively rare event. However in the absence of the further clarification it is important to at least advise patients on the potential risks of superinfection.

References:

Unless stated otherwise, references refer to the XII International HIV Drug Resistance Workshop, Los Cabos, Mexico, 10-14 June 2003; published as part of Antiviral Therapy Volume 8 Issue 3.

1. Palmer S et al – Population genetics in HIV-1 superinfection. Abstract 62.
2. Perrin L et al – Co- and super-infection: persistent replication of both HIV-1 strains? Abstract 63.
3. Burger H, Fang G, Kuikero C et al – Recombination following superinfection by HIV-1. 2nd IAS Conference, Paris. 13-16 July 2003. Abstract 71.
4. Manigart O, Courgnaud V, Sanou O et al – HIV-1 superinfections in a cohort of commercial sex workers in Burkina Faso as assessed by a novel autologous heteroduplex mobility procedure, ANRS 1245 study. 2nd IAS Conference, Paris. 13-16 July 2003. Abstract 72.

Californian and Scottish researchers report in the 2 May issue of AIDS on a case of intraclade HIV-1 superinfection by wild-type virus in the absence of antiretroviral therapy in a patient initially infected with drug-resistant HIV. They conclude that the substantially different in vivo viral growth characteristics they observed illustrate the potential for superinfection to impact disease progression.

The immunological response to HIV-1 infection has been postulated to impede superinfection with a second virus; however, a few recent reports have documented cases of HIV-1 superinfection in humans either from different viral clades or from the same clade. Kersten K Koelsch, of the University of San Diego, and colleagues set their objective to differentiate between coinfection and superinfection in a patient harboring a distinct wild-type HIV four months after primary infection with drug-resistant HIV.

They used detailed dye primer and clonal sequencing along with length polymorphism analysis to investigate the evolutionary linkage between viral populations sampled at different time points.

They found that after a set point viral load of 6000 copies HIV RNA/ml, viral load jumped to 34,000 copies/ml at month four and, shortly after, to almost 200 000 copies/ml. At that time a second viral strain was first detected by dye primer sequencing of a pol fragment. These findings were confirmed by analysis of a 1300 bp gag-pol fragment and clonal sequencing and phylogenetic analysis of the V3 region. Length polymorphism analysis of the gp120 V4-V5 region showed that the second viral population was absent even as a minority population until month four, when it was found to be the majority population, and the initial variant was present only as a minority. Both strains were subtype B.

In their Discussion the researchers write: “Infection by viral variants with differing replication capacities and their variable susceptibility to the host immune response might be expected to have a significant impact on disease progression. Indeed, in the case described here, an abrupt increase in plasma viremia occurred coincident with the appearance of the second variant and consistent with the hypothesis that this second variant had greater in-vivo fitness than the initial, drug-resistant virus. The theoretical acceleration of disease progression that might result from a higher post-superinfection viral setpoint appears to be reflected in the steeper trajectory of the CD4 cell decline in this patient after superinfection.

“A second issue of importance is the impact of superinfection on treatment response. An obvious scenario for concern is that of a patient with drug-sensitive virus responding well to therapy who then becomes superinfected with drug-resistant virus. The transmission of drug-resistant virus is a common event. However, the case described here highlights a more insidious danger arising as a consequence of superinfection. In this case, standard drug susceptibility testing at late time points would fail to detect the occult drug-resistant virus. Nevertheless, if this patient were to initiate therapy, it seems likely that drug-resistant virus would quickly re-emerge.”

The authors cite a handful of recent publications and conclude: “Together, these recent reports suggest that superinfection may occur more commonly than has previously been assumed, which has broad implications for HIV treatment, epidemiology, vaccine development and pathogenesis.”

Ref: Koelsch K, Smith DM, Little SJ et al. Clade B HIV-1 superinfection with wild-type virus after primary infection with drug-resistant clade B virus. AIDS 17(7):F11- F16, 2003.

The full text of this article is available online following single free registration:
http://www.medscape.com/viewpublication/744_toc?vol=17&iss=7

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Growing evidence affirms the previous plausibility of re-infection. The frequency of this remains difficult to determine. With the fragility of combination therapy dependent retaining drug sensitivity, drug absorption, food and drug interactions and adherence, the additional risk from reinfection is rarely suspected or investigated.

Large numbers of such cases are never likely to be reported, but this does not mean that they are only occurring infrequently.

Despite dramatic advances in the treatment of HIV infection and the resultant decrease in deaths from AIDS, new HIV infections continue to occur among Americans at a relatively steady rate of 40 000 to 45 000 per year. More than 90% of cases of acute HIV infection go undiagnosed despite the fact that more than 50% of persons with the disease are symptomatic. Although many of these symptomatic patients seek medical attention at emergency departments, urgent care centres, and primary care offices, they often receive the true but highly misleading diagnosis of “viral syndrome” and are told to go home, take aspirin and plenty of fluids, and call if the symptoms do not resolve. Usually, the symptoms do resolve. Acute infection occasionally has severe sequelae, which may include neurologic syndromes (such as meningitis or myelopathies) or opportunistic infections caused by profound decreases in CD4 cell count (such as Pneumocystis carinii pneumonia or Candida esophagitis).

Why have we, as a medical profession, been so lax in diagnosing acute HIV infection? There are two primary reasons. The first is that treatment and often diagnosis of HIV infection have been relegated to specialists. Sometimes this is due to lack of knowledge of newer tests or therapies, and sometimes it is due to discomfort related to the difficult issues surrounding HIV, such as high-risk sexual behaviour and substance abuse. Sometimes it is simply caused by a clinician’s inability to spend the additional time that the subject of HIV frequently requires. Relegating diagnosis and management of HIV infection to specialists has severely impaired our ability as a profession to diagnose this syndrome. Patients with primary HIV infection most often present to non-HIV specialists, such as dermatologists, emergency department physicians, or primary care physicians, with mononucleosis-like symptoms, including fever and myalgias. Rather than considering acute HIV infection and ordering the appropriate tests, the clinician often refers the patient to a specialist in some other building and some other part of town. More often than not, the patient never gets there.

The second reason it has been difficult to diagnose acute HIV infection is that laboratory testing can be complicated and the results may be difficult to interpret. The article by Daar and colleagues in this issue [of Annals of Internal Medicine] provides an important contribution regarding appropriate testing for acute or “primary” HIV infection. The authors pooled their collective experience among three cohorts involving 436 patients to evaluate the sensitivity and specificity of two different testing strategies. Patients who were potentially exposed to HIV through high-risk sexual behaviour or needle sharing and had symptoms compatible with primary HIV infection were referred for evaluation at two centres in California. Primary HIV infection was diagnosed in 54 patients (12.4%).

The authors evaluated a commercially available p24 antigen assay and a commercially available plasma HIV RNA assay that used branched-chain DNA. The latter test is frequently referred to as a plasma viral load assay and is used to monitor chronic HIV infection, particularly the effectiveness of therapy. The costs of these two assays are quite different (at our institution, a patient is charged $220.00 for a plasma viral load assay and $75.00 for a p24 antigen assay, although the actual cost is significantly less). In the study by Daar and colleagues, the p24 antigen assay had a sensitivity of 88.7% for primary infection in patients who had negative results on enzyme immunoassay or an indeterminate result on Western blot, compared with a sensitivity of 100% for the plasma viral load assay. The specificity of the p24 antigen test was 100% compared with 97.4% for the plasma viral load assay. Patients with primary HIV infection who had a negative result on enzyme immunoassay or an indeterminate result on Western blot had a plasma viral load that consistently exceeded 100 000 copies/mL.

The HIV-1 plasma viral load assay is certainly newer and, because it is based on polymerase chain reaction technology, “higher tech.” However, these results demonstrate that the plasma viral load assay is costly and may be less useful for screening large numbers of persons in whom the prevalence of primary HIV infection is relatively low. Although the plasma viral load assay has better sensitivity, its relatively poor specificity may make it less desirable for screening in primary care settings. For individual circumstances, physicians may choose to use the plasma viral load assay because of its better sensitivity. In a symptomatic patient with negative results on enzyme immunoassay or an indeterminate result on Western blot, a plasma viral load less than 10 000 copies/mL should be interpreted cautiously as a potentially false-positive result.

The costs and benefits of screening for acute infection with these two assays can be demonstrated as follows. In a large urban emergency department that has 50 000 visits per year, one might anticipate screening 500 patients for primary HIV infection on the basis of symptoms. If 1% of persons screened, or 5 of 500, had primary HIV infection, then the p24 antigen assay would be expected to diagnose HIV infection in at least 4 of these patients without any false-positive results. On the other hand, if a plasma viral load assay was used, 5 of 5 primary infections would be detected, but up to 3% of persons screened, or 15 persons, might have a false-positive result. In these circumstances, the false-positive plasma viral load is usually low (<10 000 copies/mL), whereas in true-positive cases of primary HIV infection, the plasma viral load is usually more than 100 000 copies/mL. Extensive counselling, as well as further testing, would be necessary for the 15 patients with false-positive results, and the emotional toll would also be great. For large-scale screening, the p24 antigen assay seems to be more desirable, although it will miss a small number of HIV-infected persons. The cost of screening 500 people by p24 assay at $75 per test, in addition to the standard HIV serologic assays, is $37 500. In comparison, it would cost $110 000 to screen 500 people by viral load assay at $220 per test.

Do symptoms help predict which persons might have primary HIV infection? In the study by Daar and colleagues, patients with primary HIV infection were significantly more likely to report fever, myalgia, arthralgia, rash, and night sweats. Combining fever, myalgia, and rash increased the predictive value of symptoms; however, no combination of symptoms identified more than 75% of patients with primary infection. Because these symptoms are highly nonspecific, no good symptom scale can definitively indicate which patients should be tested for primary HIV infection.

It is also important to realize that screening for primary HIV infection should not be limited to persons with “high-risk” behaviours, because this categorization leads clinicians to miss most patients with heterosexual or unspecified risk factors. Although the study by Daar and colleagues was carried out in Los Angeles and San Diego, where men with primary HIV infection were more likely to be homosexual, this cannot be assumed to be the case in other regions of the country. The HIV epidemic is spreading most rapidly among heterosexual persons, particularly adolescents and young adults nationwide. Limiting screening for primary HIV infection to certain risk groups would be a mistake.

Diagnosing primary HIV infection can be enormously beneficial, both from the individual and public health perspectives. Persons who receive appropriate counselling may decrease their high-risk behaviour and thereby decrease HIV transmission. Identification of new infections will allow the development of targeted prevention strategies throughout relevant communities. Patients who receive a diagnosis of primary HIV infection should be considered for early therapy and should be screened for other infections, such as sexually transmitted diseases, hepatitis, and tuberculosis. In addition, they should be vaccinated to prevent pneumococcal pneumonia and hepatitis A and B. The National Institutes of Health have funded a national (US) network (the Acute HIV Infection and Early Disease Research Program [AIEDRP]) that will coordinate research efforts to better understand immunologic and virologic events associated with primary HIV infection. Because early treatment of HIV infection may provide better immunologic control of infection, providers and patients are encouraged to consider enrolment in trials of primary HIV infection.

The broader medical community has successfully incorporated routine HIV testing among pregnant women regardless of risk group. We now need to take the next step and incorporate screening for primary HIV infection among all patients who present for evaluation with compatible symptoms. Primary care physicians and the primary care network, which includes health care clinics, urgent care centres, and emergency departments, should consider evaluating primary HIV infection by using the standard serologic tests enzyme immunoassay and Western blot and adding a p24 antigen assay for all persons with compatible symptoms. Primary care physicians should immediately begin to integrate routine screening for acute HIV infection so that individual patients and communities may benefit as soon as possible.

The fully referenced text of this editorial is available at:

http://www.annals.org/issues/v134n1/full/200101020-00017.html

The full text of the “Brief Communication” from Daar and colleagues is also available at:

http://www.annals.org/issues/v134n1/full/200101020-00010.html