Question
What is the difference between HIV-1 and HIV-2?
27 September 2006. Related: All topics, Other tests.
What is the difference between HIV1 and HIV2 with regards to structure, function, occurence and survival in the environment?
Answer
HIV-1 and HIV-2 are two different viruses. HIV-1 is the main family of HIV and accounts for 95% of all infections worldwide. HIV-2 is mainly seen in a few West African countries. The spread in the rest of the world is negligible.
Although HIV-2 generally progresses more slowly than HIV-1, some HIV drugs (NNRTIs like nevirapine and efavirenz) do not work against HIV-2.
On a structural level HIV-1 and HIV-2 have important genetic differences. A technical description of the difference is that the vpu gene found in HIV-1 is replaced by the vpx gene in HIV-2. In addition, the protease enzymes from the two viruses, which are aspartic acid proteases and have been found to be essential for maturation of the infectious particle, share about 50% sequence identity.
There are, however, differences in substrate and inhibitor binding between these enzymes. Most notably between the CGP 53820 inhibitory binding.
On functional level, there is a difference between the two viruses in terms of how easy it is for the virus to infect someone. HIV-1 enters the immune system by attaching onto the CD4+ receptor found on the surface of certain white blood cells. HIV-2 has a harder time gaining such a foothold.
So HIV-2 generally progresses much more slowly, with lower viral laod and slower risk of becoming sick. However, some HIV drugs (including NNRTIs) are not active against HIV-2.
Both viruses are fragile and highly susceptible to physical and chemical agents and therefore do not survive well outside the human body. HIV in blood or sexual fluid for example is not infectious after it has been outside the body for a few minutes.
Notes: this answer was updated in January 2018.
Hi Sayyad,
There is a comprehensive overview of what ART is, and how it works etc, in the following guide:
http://i-base.info/guides/starting
If you need any info after having read it, please get in touch. Also, do you know what your CD4 count is and viral load?
I am suffering from HIV at initial stage by confirming Elisa test. I want to know about ART treatment for HIV.
Hi Kano,
HIV progresses differently from person to person. However eventually if people don’t take meds their CD4 will drop. There viral load will also rebound, and they will get ill. They will also become more prone to opportunistic infections.
The only thing that can help a persons HIV is treatment.
Is it possible to survive HIV without treatment? I mean some people don’t even know they are infected and they never get sick.
Hi Sairam,
At the moment there isn’t a cure for either HIV1 or HIV2. However, there are people all over the world working on a possible cure.
Are you on medication?
Hi Sairam,
If you have HIV2 when you start treatment its important that don’t take NNRTIs. NNRTIs, don’t work on HIV2.
At first it may be better to start with intergrace inhibitors rather than PIs.
What these drugs are is discussed here:
http://i-base.info/guides/category/arvs
Medicine for hiv-2,kindly give reply.
Dear,
I had confirmed infection of HIV2 in 2008. My CD4 count is now 350.Is there a cure for this disease?
Hi Mimi,
Are you on medication? If you are how long have you been on it for? Do you know what your CD4 is?
Is there any specific reason why you think you will die soon? I ask this as HIV is a very treatable health condition. Also, a lot of people who are positive can expect to live long and health lives. See question 10 here:
http://i-base.info/qa/?s=life+expectancy
Am scared that I’ll die soon