Pediatric studies from 10th CROI

Polly Clayden, HIV i-Base

There were a number of reports pertaining to paediatric HIV at the tenth Conference on Retroviruses and Opportunistic Infections, particularly focusing on neonates and vertical transmission and metabolic abnormalities in children receiving antiretrovirals.

Simplification of neonatal prophylaxis

Since the widespread adoption of the 076 protocol in the industrialised world, the maternal monotherapy component of this strategy has largely been replaced by combination therapy to treat maternal disease in pregnancy. However, neonates born to HIV-positive mothers still typically receive zidovudine (ZDV, Retrovir) four times a day, in accordance with the original protocol, for the first six weeks of life to reduce mother to child transmission.

A poster from O’Meara and colleagues from Dublin reported substitution of a four week, twice daily regimen for the original six week four times a day strategy.[1] The rationale for this was based upon the success of four-week post exposure prophylaxis strategies for adults.

The investigators speculate that regimen simplification could help adherence and limit toxicity, particularly ZDV-associated anaemia, and they report findings from an audit of 229 infants born to mothers with HIV, performed between November 1994 and June 2002.

Of the group studied, 67% of the 202 HIV-positive mothers were African and 94% received ARV during pregnancy (67% triple therapy, 23% dual therapy, and 9% ZDV). 90% of the women had intrapartum intravenous ZDV; 14 infants received only the post partum component.

Mode of delivery included: 61% vaginal deliveries, 25% elective C-section, and 14% emergency C-section. Of 229 infants, 41% received triple therapy (four weeks ZDV/3TC/NVP, 2mg/kg, one or two doses), 25% received 3TC/ZDV, and 31% ZDV. Prescribed duration of post partum prophylaxis was four weeks for 223 infants. Out of the group of infants receiving ZDV monotherapy – 99 (43%) received 4mg/kg BID and 130 (57%) 2mg/kg four times a day. Some 97% of infants completed the prescribed regimen and 225 were uninfected. Only one infant was not followed up after delivery.

Overall, 33/228 (14%) had Grade 3 or 4 anaemia (15% BD vs 14% four times a day zidovudine); 88/228 (38%) had Grade 3 or 4 neutropenia (30% BD vs 40% four times a day zidovudine). All resolved to ≤ grade 2 after 12 weeks. A slight trend toward less neutropenia in BD zidovudine recipients was also observed.

Despite the limitations of a retrospective audit spanning eight years and using various ZDV regimens, the investigators reported that this study suggests that efficacy will not be affected by shortening the six-week neonatal component. The overall transmission rate was 1.3- 1.7% and the three known infected infants were reported to have been infected in utero so that the reduced duration of therapy would not have affected outcome.

Concern that a switch to BD zidovudine dosing might be accompanied by greater haematologic toxicity was not proved and the only predictor of neonatal anaemia was in utero exposure. The incidence of anaemia and/or neutropenia was not increased in infants receiving dual or triple therapy in this study.

Anecdotally it seems that several groups already use simplified strategies for neonate prophylaxis (and regimens that do not contain ZDV in cases where the mother has resistance to this agent) but to date there have been no published data to support this.

IL-2 production in HIV exposed uninfected infants of mothers given NVP prophylaxis

Single dose nevirapine (NVP, Viramune) given to HIV-positive mothers in labour followed by a single dose to the neonate is used widely as a strategy to reduce mother to child transmission in resource poor settings. However, the mechanisms of this strategy are unclear.

A poster from Kuhn and colleagues reported from a study investigating immunologic responses among infants born to HIV-infected mothers [2]. In this study cord blood was collected from 25 deliveries in which nevirapine was given at the onset of labour and compared to cord blood from 115 deliveries in which no antiretrovirals were given. In addition cord blood from 20 HIV-negative mothers was used as a control.

IL-2 production was measured using the Quantiglo immunoassay (R&D, Oxon, UK) and HIV-stimulated IL-2 production was detected among 18/115 (16%) deliveries if no antiretroviral drugs were given prior to birth, but among 0/25 deliveries if nevirapine was given (p = 0.03). No HIV-stimulated responses were detected among the control group.

The investigators reported similar results if the evaluation was restricted to those deliveries in which the infant was confirmed to be uninfected. Maternal plasma viral load and CD4 counts at delivery were similar among those with or without HIV-stimulated IL-2 responses (mean 4.23 log10 copies/ml vs ml vs 4.11 log10 copies/ml; mean 479 vs 541 cells/ml respectively).

They concluded that single-dose nevirapine given shortly before birth may have immunologic consequences detectable in cord blood and that further characterisation of these consequences may help identify how single dose nevirapine is effective in reducing perinatal HIV transmission. The investigators noted: “Studies of newborn immune responses to HIV need to take into consideration use of antiretroviral drugs prior to birth.”

Mother to child transmission of mixed maternal HIV variants

A poster from Cosgrove and colleagues compared maternal and infant isolates from HIV-positive mothers and their infected infants in order to track mixed variants detected in maternal samples, following mother to child transmission [3].

HIV isolates from 18 mothers enrolled in the WITS study, at or near delivery, were compared with paired sequences either for their infected infants at birth (n=5) or at first available positive culture (n=13) and with follow-up infant isolates within the first year (n=18). Nucleotide sequences for protease codon 1 through RT codon 324 were determined using Bioinformatics software created to analyse positions with mixed sequence in maternal and/or infant isolates.

Fifty-four (54) total isolates from 18 mother/baby pairs were sequenced. The investigators observed 327 mixed positions, including 208 maternal mixed sites, three infant birth mixtures, and 50 mixed positions at first available infant culture. Maternal mixtures per isolate (median 13.5, mean 14.3) were much more prevalent than mixtures in earliest infant isolates (median 0, mean 3.1) (p < 0.001, chi squared). Of 208 maternal mixed positions, only 17 were transmitted to the infant, all of these in three mother/baby pairs with high numbers of maternal mixed positions (19, 20, and 26). Of the remaining 191 maternal mixtures, infants showed wild type alone significantly more frequently (143/191, 75%), than mutant alone (48/191, 25%) (p < 0.05). Most maternal mixtures were at third codon positions.

From maternal mixtures, wild-type alone was most likely to be transmitted to the infants (68%), especially at resistance positions (6/6, 100%). Very few maternal mixtures were transmitted to the infant (8%).

The investigators concluded that mother to child transmission represents a “…population bottleneck for the virus” and only a small fraction of maternal genotypes are transmitted vertically. They added: ”From maternal mixtures the wild type component is more likely to be transmitted to the infant, including at resistance positions.”

Influence of maternal viral load on infant disease progression

A meta analysis from Tatsioni and colleagues evaluated whether HIV RNA levels of mothers at or close to the time of delivery affects the rate of disease progression among vertically infected children, and whether it correlates with early levels of HIV RNA in the infant and has an influence on infant disease progression [4].

The investigators performed their analysis using data from eight studies from centres in Europe and the US with 574 HIV-infected infants with available maternal viral load measurements at or close to the time of delivery and clinical follow-up. The primary outcomes were disease progression to category C or death (n = 178). The secondary outcome was death (n = 86).

Maternal viral load significantly increased the risk of disease progression (p = 0.02). The association with disease progression risk was strong in the first six months of life (p = 0.001), but not subsequently. Across all studies, maternal viral load at or close to delivery correlated with early infant viral load (r = 0.26, p < 0.001).

It is hoped that according to current standard of care in the industrialised world, treating maternal disease appropriately for a woman’s own health and in turn preventing mother to child transmission would be reason enough to aim for an undetectable maternal viral load particularly at or close to delivery. This analysis also reveals (in keeping with previous data) maternal viral load to be a strong independent predictor of infant disease progression especially in the first six months of life. The correlation was similar whether or not mother and infant pairs received antiretroviral therapy.

Gender differences in mother to child transmission

An investigation into gender and susceptibility to infection and disease progression in children, reports a significant increase in transmission to girls and in particular African girls, compared to boys [5].

This poster from Newell and colleagues on behalf of the European Collaborative Study (ECS) found, in this non-breastfeeding population, a higher prevalence of mother to child transmission among girls (adjusted odds ratio 1.44 p=0.018). ECS is a prospective cohort study, in which infected and uninfected children born to HIV-infected mothers are followed from birth in nine European countries.

This study, initiated in 1987, recorded an overall vertical transmission rate of 10.9%, which has declined significantly in recent years to a current average of less than 1%. The study also evaluated various virological and immunological parameters in both infected and uninfected children.

Distinct gender differences observed in mother to child transmission suggesting an “…underlying important genetic component in immune response to HIV-1” which the investigators speculate could have implications for therapy decisions.

In contrast an oral presentation from Read and colleagues on behalf of the Breastfeeding and International Transmission Group, reported that girls were 40% less likely to become infected with HIV through breastfeeding transmission (late postnatal transmission) [6].

In this meta-analysis combining data from nine randomised, placebo controlled trials of breastfeeding populations in South, East and West Africa (PETRA, ANRS, HIVNET 012 etc), the investigators set out to estimate the contribution of late postnatal transmission of HIV through breastfeeding to the overall risk of mother-to-child transmission, to characterise the timing and to identify determinants of breastfeeding transmission. Data for children born before January 2000 were analysed.

The investigators defined early transmission as being infants having a positive DNA PCR before four weeks and late transmission as infants having a negative DNA PCR before they were four weeks old, but a positive test after four weeks. Unknown timing of transmission was defined as one positive DNA PCR after four weeks.

There were 5,871 deliveries evaluated, including 4,085 children with appropriate data. Of these, 993 (24%) were definitively infected, with 314(32%) early, 225 (23%) late infection and 454 (46%) unknown timing of transmission. The probability of transmission was 7%, 12% and 15.6% at six, 12 and 15 months respectively. Late transmission occurred throughout the period of breastfeeding, and the estimated risk of late transmission throughout the breastfeeding period was fairly constant.

In addition the investigators reported lower CD4 count (women with CD4 < 200 cells had an eight-fold increased risk of transmission to their infants) and that girls were 40% less likely to become infected with HIV through breastfeeding despite identical duration of breastfeeding between the sexes.

Gender theorists in the audience were quick to speculate that behavioral mechanisms could be responsible for this significant difference: are male children likely to be fed for longer or fed more frequently, or are genetic factors responsible? But this study did not evaluate breastfeeding practices, and many questions remain concerning nurture vs nature. The investigators suggest that, “the association of gender with late transmission of HIV should prompt further research into the potential underlying mechanism(s), both biological and cultural.”

It was very clear though (particularly given the impressive sample size) that breastfeeding risk varies according to maternal CD4 count, with lower CD4 count associated with higher risk, reflecting more advanced maternal HIV disease and, possibly, higher viral loads in maternal plasma and breast milk. And that late transmission makes a considerable contribution to mother to child transmission rates overall (24% – 42%) among breastfeeding populations.

ALVAC vaccine in neonates

An oral presentation and a poster from McFarland and colleagues presented findings from the PACTG 326 phase I/II study of the safety and immunogenicity of ALVAC vCP205 vaccine given to neonates [7,8]. In the absence of antiretroviral therapy for the mother to prevent vertical transmission, an effective vaccine for the neonate could be a potential strategy for reducing mother to child transmission through breastfeeding.

ALVAC-HIV vCP205 (Aventis Pasteur) is recombinant canarypox, expressing gag, env and protease genes of HIV that is safe and immunogenic in adults.

Twenty-eight infants were randomised to receive high dose, low dose or placebo vaccine. Doses were given to 28 infants at week 0 (≤ 72 hours of birth), and at weeks four, eight, and 12. All infants were monitored for local/systemic toxicity, laboratory abnormalities, lymphoproliferative (LPA), and cytotoxic T-cell (CTL) responses. Infants in both high and low vaccine arms showed positive LPA responses to gp160 and p24. These responses were observed as early as two weeks (and as late as two years after immunisation). CTL responses were also observed to gag, env or env/gag as early as two weeks and up to a year following immunisation. The investigators also reported some CTL response from the infants in the placebo arm.

Some mucosal response was demonstrated in 33% of infants in the high dose arm at 12 weeks and 22% at 24 weeks. The investigators reported that overall the vaccine produced cell mediated responses in approximately one third of neonates immunised. They also reported a transient mucosal response in infants in the placebo arm that they speculated could be explained by HIV exposure in uninfected infants.

Although the sample size is extremely small and the degree of immunogenicity modest, the investigators concluded that these data suggest that vCP205 is safe and immunogenic in infants. HIV-specific cell-mediated responses could be induced early in life, warranting further study of HIV vaccines in neonates.

Structured treatment interruption

Studies of structured treatment interruptions (STI) in adults have reported induction of HIV-specific responses mediated by CD4 and CD8 cells that may enhance control of viremia. To date there have been no reports of the effect of STI in children.

A poster from McFarland and colleagues on behalf of the PACTG 1015 group (with a second poster describing additional details on virologic effects) reports interim data from an ongoing study looking at a novel approach to antiretroviral therapy in children [9,10].

In this study eligible patients are aged four to 21 years old, with a CD4 percentage of >20%, an undetectable viral load <400 copies/mL for a year prior to study entry, and are receiving HAART including a PI but excluding abacavir or an NNRTI.

Children undergo sequences of HAART and treatment interruptions – beginning with three days interruption and subsequently lengthening by two days alternated with a minimum of three weeks of HAART (or time to achieve <50 copies/mL). The maximum interruption allowed in the protocol was seven weeks off therapy.

The investigators report results from 10 children. They found that viral load largely rebounded fairly quickly (within five to nine days of interrupted therapy) and in addition they reported, increases in the frequency of HIV specific CD4+ and CD8+ interferon gamma secreting T cells and modest increases in the percentage of activated CD8 cells (CD38+/HLA-DR+).

They conclude that “these data suggest that STI during established HIV infection in children increases the frequency and antigenic breadth of HIV-specific CD4+ and CD8+ cell responses” and they also report that “in the early stages of a progressively increasing STI regimen in paediatric populations, viremia has resumed sooner than has been reported in adults, and there have been no difficulties in achieving subsequent virologic suppression.”

STI strategies for children are currently being mooted among paediatric groups including the European PENTA network and clearly there are interesting scientific questions to be answered in children. This strategy would almost certainly be too complicated to perform other than within a research setting though – families already undergo considerable challenges achieving adherence in children with HIV, although for some simpler strategies may be welcome. At present many groups treating children with HIV would consider interrupting their therapy far too much of a risk.

Metabolic complications

A number of posters investigated metabolic complications in children, often with conflicting findings.

Ramos and colleagues assessed the prevalence in their cohort of such abnormalities [11]. The investigators reported findings from a group of 49 white children (25 girls, median age of 127 months [53-219]). Of this group the median CD4 count was 842 and 59% had HIV-RNA below 300 copies/ml. Median duration of HAART was 54 months (16-68) and all but three children were receiving a PI-containing regimen.

They describe a high prevalence of metabolic complication, with hypercholesterolemia and hypertriglyceridemia present in 69% and 23% of children respectively. Hyperinsulinemia was detected in 24% whereas an increase in C-peptide occurred in 10%. Hyperlactatemia was observed in three children (all asymptomatic). Lipodystrophy was diagnosed in 12 children (11 female) and osteopenia in 21 (38%). They found no association with lipodystrophy and osteopenia, hyperlipidemia, or hyperinsulinemia.

In a larger study by Vigano and colleagues on behalf of the Italian Register on HIV in Children and the European Collaborative Study, the investigators performed a similar analysis of 374 children from 23 clinics across Europe [12].

One hundred and ninety-six of the children evaluated were female, and their median age was five years. Seventy-four per cent of the children were receiving triple therapy. They reported that 28% of children had one clinically determined sign of fat redistribution, of whom 23% had signs of peripheral lipoatrophy alone (fat wasting of the face, arms, legs or buttocks), 37% signs of central obesity alone (fat accumulation in the abdomen or dorsocervical spine, or breast enlargement), and 41% combined lipodystrophy. The most common sites of fat redistribution were the abdomen, face, legs, and arms (21%, 12%, 12% and 11% of the group respectively). Dyslipidemia was present in children, of whom 42% (42/101) also showed fat redistribution.

The investigators found female gender, CDC clinical stage C and current use of triple therapy to be significantly and independently associated with any fat redistribution (and also for lipoatrophy and central obesity). They also reported that older children (> 12 years) were more likely to develop central obesity. They did not find length of time on ARV to be associated with fat redistribution or metabolic abnormalities.

Duration of PI therapy was evaluated, in addition to age and adherence as factors in elevated total cholesterol (TC) in addition to the relationship of TC with hypertension and obesity in children.

Farley and colleagues on behalf of the PACTG 219C team evaluated 1,927 children between four and 19 years. [13] PACTG 219C is a prospective cohort study to examine long-term outcomes in HIV-infected children and in HIV- children born to HIV-infected women.

12.8% of children had abnormal cholesterol levels, defined as a level higher than 95th percentile of the gender, race and age specific targets (TC > 95). The gender distribution was balanced and the median age was 10 years. They found that TC > 95 was significantly associated with white race (prevalence shown in brackets) – (19%), younger age < 6 yrs (19%), current PI use (17%), > 3 yrs of PI use (16%), parent/patient report of no missed doses in the past three days (15%), HIV-1 RNA < 400 copies/ml (22%), and CD4% > 25 (14%).

However, TC > 95 was not associated with hypertension or obesity. Receipt of an NNRTI non-PI regimen was protective (p = 0.033).

The investigators reported the following independent variables to be highly statistically significant (all p < 0.004): present PI use, two or more PIs currently used, report of no missed doses past three days, younger age, and white/Hispanic ethnicity. Current PI usage was associated with 3.6 times the risk of TC > 95. Each additional PI currently being taken resulted in 72% increase in risk. Duration of treatment with the specific PIs lopinavir/ritonavir or nelfinavir was associated with increased risk (p = 0.011 and 0.028, respectively).

They concluded that hypercholesterolemia was associated with PI use (particularly dual/triple PI), excellent adherence, younger age, and white/Hispanic ethnicity, but not hypertension or obesity

Another poster from Vigano and colleagues – whose group in Milan has generated some of the most interesting research into metabolic disorders in children – assessed the effect of impaired growth hormone (GH) secretion on excess accumulation of visceral fat as characterised in adults [14].

In this study, 25 pubertal HAART-treated children were assessed for growth hormone (GH) secretion. Additionally fasting serum insulin-like growth factor-1 (IGF-1), IGF binding protein 3 (IGFBP3), insulin, cholesterol (total, HDL, LDL), triglycerides, and nitric oxide levels were also determined. Total and regional body composition and intra abdominal adipose tissue content (IAT) were also assessed.

Of the children evaluated, 10 had visceral fat accumulation and 15 did not. The two groups were similar in the following parameters: age (14.8 vs 13.8 yrs), BMI (19.3 vs 20.2), female/male ratio (7/8 vs 7/3), and months of HAART exposure (55.5 vs 54.5).

Children with excess accumulation of visceral fat showed lower GH area under the curve (AUC, 16.4 vs 31.6 mcg/hr/l; p < 0.05), IGF-1 (384 vs 515 ng/ml, p < 0.05), IGFBP3 (4.3 vs 4.7 mcg/ml, p < 0.05), nitric oxide (11.5 vs 27.9 mmol/l, p < 0.05) and higher insulinemia (17.8 vs 9.8 mcIU/ml, p < 0.05) than children without. Lipid profiles were similar in both groups.

Children with excess visceral fat, as compared to children without, showed increased fat mass (11.0 vs 6.8 kg, p < 0.005), trunk fat (6.6 vs 3.7 kg, p < 0.0001) and fat/lean ratio (0.31 vs 0.17, p < 0.001.

The investigators conclude: “Impaired GH secretion is detectable in pubertal HAART-treated children with increased visceral adiposity and hyperinsulinemia.” And they recommend that “the monitoring of GH secretion could be included in the evaluation of HIV-associated lipodystrophy in children,” and speculate that their data may indicate a possible role for rGH therapy.

Schwarzwald and colleagues reported findings from a prospective cross-sectional study evaluating the prevalence and relationship to protease inhibitor-containing HAART of osteopenia and osteoporosis in HIV-infected children [15].

Twenty-seven children were evaluated in this study of which 66% were receiving a PI, the mean duration of therapy was 42 months, 13 were girls and the mean age was 11 years old. The investigators reported that of this group, 52% had osteopenia and 23% osteoporosis. Boys were more likely to have osteopenia or osteoporosis than girls (p=0.02) and longer duration of PI therapy correlated with greater risk (p<0.001). Neither age, ethnicity nor CDC classification correlated with greater risk of osteopenia or osteoporosis.

From this small sample size a high prevalence of osteopenia and osteoporosis (74% overall) was reported. This is of great concern as most bone formulation takes place before the age of 30 and failure to form adequate bone mass during this critical period of childhood and young adulthood development may have serious consequences in later life.

Finally, McComsey and colleagues report findings from a study of a nine month course of calcium and vitamin D supplements received by 23 children receiving ARV, 48% of whom were classified as osteoporotic [16].

The investigators reported that during the study period no significant decrease in bone mineral density occurred. In addition, no improvement in bone loss was observed in the children who received the course of calcium/vitamin D supplements.

It appears as with reports from adult cohorts that the prevalence of metabolic complications is high in children and the long term consequences of these effects are of great concern. Additionally as with adults there is still a lack of clear case definitions for these complicated disorders.

References:

Unless stated otherwise, all references are to the Programme and Abstracts of the 10th Conference on Retroviruses and Opportunisitc Infections (CROI), 10–14 February 2003, Boston.

http://www.retroconference.org/2003/

O’Meara M, Goode M, Hayes E et al. Simplification of neonatal component of regimens to prevent perinatal HIV transmission. Abstract 853.
Kuhn L, Meddows-Taylor S, Gray G et al. HIV-stimulated IL2 production among exposed-uninfected infants of HIV-infected mothers given nevirapine prophylaxis. Abstract 861.
Cosgrove R, Bauer G, Pitt J et al. Selective vertical transmission of mixed maternal HIV variants. Abstract 864.
Tatsioni A, Abrams EJ, Bulterys M et al. Maternal viral load and infant disease progression in vertically HIV-1 infected infants: an international meta-analysis. Abstract 870.
Newell ML, Thorne C, European collaborative study. Gender differences in vertically acquired HIV infection. Abstract 871.
Read JS, Newell ML, Leroy V et al. Late postnatal transmission of HIV in breastfed children: an individual patient data meta-analysis (The breastfeeding and HIV international transmission study). Abstract 97.
McFarland E, Johnson D, Fenton t et al. A phase I/II study of the safety and immogenicity of an HIV-1 ALVAC vaccine in infants born to HIV-1 infected mothers. Abstract 99.
Johnson D, McFarland E, Muresan P et al. PACTG 326: a phase I/II study to evaluate the safety and immunogenicity of ALVAC HIV vaccines alone and with AIDSVax B/B in children born to HIV-infected mothers: preliminary results. Abstract 404.
McFarland E, Borkowsky W, Mureasan P et al. Increases in HIV-specific CD4 and CD8 T-cell mediated responses in children undergoing structured treatment interruption. Abstract 884.
Borkowsky W, Yogev R, Mureasan P et al. T-cell and virologic outcomes of a progressively increasing structured treatment interruption study in chronically-infected children and adolescents. Abstract 885.
Ramos JT, Garcia L, Rojo P et al. High prevalence of metabolic abnormalities in HIV infected children treated with HAART. Abstract 772.
Vigano A, Thorne C, Italian register on HIV in children, European collaborative study fat redistribution and metabolic abnormalities in HIV-infected children and adolescents in Europe. Abstract 774.
Farley J, Gona P, Crain M et al Prevalence of hypercholesterolemia and associated risk factors among perinatally HIV-infected children (4 -19 Years) in PACTG 219C. Abstract 773.
Vigano A, Mora S, Brambilla P et al Impaired GH secretion corrolates with increased visceral adiposity and hyperinsulinemia in HAART-treated children Abs 776.
Schwarzwald H, Ellis KJ, Evans DL et al Effect of HAART on bone density in HIV-infected children. Abstract 778.
McComsey GA, Leonard EG. The effect of calcium and vitamin D on bone mineral density in HIV-infected children with osteoporosis Abstract 779.