Research suggests ability of HIV to cause AIDS is slowing

The rapid evolution of HIV, which has allowed the virus to develop resistance to patients' natural immunity, is at the same time slowing the virus's ability to cause AIDS, according to new research. The study, published recently in theProceedings of the National Academy of Sciences (PNAS), also indicates that the virus is becoming less “virulent” because of widespread access to antiretroviral therapy (ART). Researchers enrolled more than 2,000 women with chronic HIV infection to take part in the study. The first part of the study looked at whether the interaction between the body's natural immune response and HIV leads to the virus becoming less virulent. Central to this investigation are proteins in the blood called human leukocyte antigens (HLA), which enable the immune system to differentiate between the human body's proteins and the proteins of pathogens. People with a gene that expresses a particular HLA protein called HLA-B*57, are known to benefit from a “protective effect” to HIV. Infected patients with the HLA-B*57 gene find their progression to AIDS slower than usual.

This study showed that in Botswana, where HIV has evolved to adapt to HLA-B*57 more than in South Africa, patients no longer benefit from this gene's protective effect. However, the team's data show that the cost of this adaptation to HIV is that its ability to replicate is significantly reduced, therefore making the virus less virulent. The authors show that viral adaptation to protective gene variants, such as HLA-B*57, is driving down the virulence of transmitted HIV and is thereby contributing to HIV elimination.

In the second part of the study the authors examined the impact of antiretroviral therapy (ART) on HIV virulence. They developed a mathematical model, which concluded that selective treatment of people with low CD4 counts will accelerate the evolution of HIV variants with a weaker ability to replicate.