Variations in two key genes influence how quickly HIV-infected people develop AIDS, says a U.S. study that challenges the long-held belief that viral load -- the amount of HIV in the blood -- is the main factor that determines progression to AIDS.
Variations in the CCR5 and CCL3L1 genes may affect immune system response to HIV and replication of the virus. Other genes may also play a role but more research is required to determine that, Agence France-Presse reported.
CCR5 controls a key receptor on the surface of the CD4 immune cell onto which HIV attaches, while CCL3L1 controls an immune system signaling molecule called a chemokine, which blocks HIV from attaching to the CCR5 receptor, the researchers said.
In this study, the researchers analyzed thousands of HIV-infected patients and healthy people and found that viral load accounted for only nine percent of the difference in how rapidly HIV-infected patients developed AIDS.
"The genetic variations contribute nearly as much to the extent of inter-individual variability in AIDS progression rates as does HIV-1 viral load," team leader Sunil Ahuja of the University of Texas Health Science Center in San Antonio, told AFP.
"Even after accounting for the detrimental effects of a high viral burden, these genetic factors influence the pace of HIV-1 disease progression," said study first author Hemant Kulkarni, assistant professor of medicine at the Health Science Center.