Gene variant may raise AIDS risk

Could explain African levels

WASHINGTON - A gene variant that emerged thousands of years ago to protect Africans from malaria may raise their vulnerability to HIV infection but help them live longer once infected, researchers said yesterday.

The findings could help explain why AIDS has hit Africa harder than all other parts of the world.

People with the version of the gene have a 40 percent higher risk of becoming infected with the human immunodeficiency virus, or HIV, researchers in the United States and Britain wrote in the journal Cell Host & Microbe.

In Africa, the gene variant may account for 11 percent of HIV infections, the researchers said.

Sexual behavior and other social factors cannot completely explain why more than two-thirds of the world's 33 million people infected with HIV live in sub-Saharan Africa, the researchers said. But even as the gene elevates a person's susceptibility to HIV infection, having this version of the gene seems to slow the progression of AIDS. Those with the variant who have been infected with HIV live roughly two years longer than people who do not have it, the researchers said.

Having the variant has become "a double-edged sword," said researcher Sunil Ahuja of the University of Texas Health Science Center at San Antonio.

About 90 percent of people in sub-Saharan Africa have this gene variant, and about 60 percent of Americans of African descent also possess it, according to the researchers.

Of the 2.1 million people who died of AIDS worldwide last year, 1.6 million were from sub-Saharan Africa, according to the United Nations.

The protein linked to the gene is called Duffy Antigen Receptor for Chemokines, or DARC. People with the variant do not have this particular receptor - a type of molecular doorway into cells - on their red blood cells.

The researchers believe the gene variant arose long ago, perhaps protecting people in Africa against a deadly strain of malaria.