HLA-B*57 (B57) is an immune gene variant that is found in less than 5 per cent of the general population but in 40 to 85 per cent of slow progressors.
According to investigators from the Multi-Center AIDS Cohort Study (MACS) at UCLA AIDS Institute, a killer T-cell immune response that occurs early on in HIV infection and targets a section or epitope of the HIV protein called IW9.
"Since the hope for a vaccine is that it would elicit immune control, the thought has been that understanding how B57 protection works would yield helpful lessons and principles for vaccine design," said researcher Catherine Brennan said.
"There have been a lot of efforts to understand how the immune response to HIV in B57 carriers is superior to the response in non-B57 carriers, but it has been hard to nail anything down conclusively," Brennan said in a statement.
HLA-B genes are known to work by activating killer T cells that recognize unique sections of proteins, or epitopes, but it has been a mystery which section or sections of HIV protein HLA-B57 and the killer T cells work through.
Previous research had largely focused on the killer T-cell response after several years of infection.
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However, researcher Beth D Jamieson believes that the most critical responses are likely to occur early during infection, when the T cells are still strong and can reduce the number of places where HIV hides out in the human body.
Although the average time between HIV infection and AIDS in the absence of antiretroviral treatment is about 10 years, some individuals succumb within two years, while so-called slow progressors can stay healthy for 20 years or longer.
The study has been published in the Journal of Virology.