By Jon Cohen
BOSTON—Some people naturally handle HIV infection better than others, but only two clear genetic explanations have ever been found. Now, a new study reported here today at the Conference on Retroviruses and Opportunistic Infections finds a third: a genetic signature that leads to a better control of the virus in people of African descent. It could clarify sometimes puzzling differences in the way the disease progresses in untreated people, and it might offer clues about new treatment strategies.
Weeks after a person is infected with HIV, levels of the virus in the blood skyrocket before dropping down to a “set point” that remains relatively constant after the immune response kicks in. Lower set points confer a couple benefits: Even without HIV/AIDS drugs, people progress more slowly to disease, and they’re less likely to transmit the virus to others. About 25% of the time, genetic factors drive the lower set point, according to previous genome-wide association studies.
Of the two known genetic factors, the most powerful comes from genes that control proteins known as human leukocyte antigens (HLAs). Different HLAs determine the strength of a person’s immune response against HIV. The second factor is white blood cells that are naturally resistant to HIV infection. HIV needs to dock on two different receptors to enter a cell, and mutations in one of them, known as CCR5, thwart HIV.
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