The variation is one of the first genetic risk factors for HIV identified only in people of African descent, spotlighting how genetics play a role in susceptibility to Human Immunodeficiency Virus, the virus that causes AIDS, the University of Texas Health Science Center at San Antonio said Wednesday in a news release.

In a population of 1,266 HIV-positive U.S. military personnel and 2,000 non-infected healthy personnel, researchers studied the gene that expresses Duffy antigen receptor, a molecule on the surface of red blood cells where the malaria species Plasmodium vivax attaches.

"Duffy antigen influences levels of inflammatory and anti-HIV blood factors called chemokines," said Dr. Weijing He, first author of the paper published in Cell Host & Microbe. "Other as-yet undefined host factors likely exert population-specific effects on HIV-AIDS, such that individuals of European or African descent are likely to have distinct host factors that affect their respective susceptibilities to HIV and AIDS."

The majority of people in sub-Sahara Africa don't express Duffy on their red blood cells, said senior lead author Robin Weiss of University College London.

"This is one of the first genetic factors particularly common in Africans that has been shown to confer more susceptibility to HIV," Weiss said.