A genetic mutation that originally protected Africans from a virulent form of malaria now renders them 40 percent more susceptible to HIV infections, offering a partial explanation for the disproportionate spread of the virus among Africans and African-Americans, researchers reported Thursday.
The mutation, however, has an unusual benefit. It also slows the progression of the disease, giving patients an extra two years of life, said Dr. Sunil Ahuja of the South Texas Veterans Health Care System, lead author of the paper in the journal Cell Host & Microbe.
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The genetic variation is the first found to increase susceptibility to HIV and the first linked to people of African descent, said virologist Robin Weiss of University College London, a co-author of the paper.
About 90 percent of Africans have the mutation, and it could account for as much as 11 percent of HIV infections on that continent, the researchers said. Sub-Saharan Africa now accounts for about three-quarters of the world’s 33 million HIV-infected people.
The mutation also affects about 60 percent of African-Americans and could partly explain why the infection is more common among blacks than whites in the United States. Blacks make up 13 percent of the U.S. population but account for nearly half of all newly diagnosed infections.
The study appears to confirm the theory that the risk of contracting HIV is not solely connected to behavior, said Phill Wilson, chief executive of the Black AIDS Institute, an HIV/AIDS think tank in Los Angeles.
“Black gay men’s behavior is no more risky — and often less risky — than white gay men, yet their vulnerability is so much greater,” he said.
Ahuja cautioned, however, that social factors — such as poverty, lack of access to health care and sexual behavior — are probably more important contributors to the risk of HIV infection.
The mutation in question involves a single letter of DNA in the gene for a receptor found on the surface of red blood cells known as the Duffy antigen. Virtually all Caucasians have the antigen, while 90 percent of Africans and 40 percent to 50 percent of African-Americans do not.