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Gene Variant May Increase HIV Vulnerability

Posted on: Thursday, 17 July 2008, 16:35 CDT

New research has found that a gene variant may make Africans more vulnerable to HIV infection, while also helping them live longer once infected. The genetic variation originated thousands of years ago to protect Africans from malaria, the researchers said Wednesday.

The gene involved in the study controls a surface protein on red blood cells. Those with the genetic variation were found to have a 40 percent higher risk of becoming infected with HIV, researchers in the United States and Britain wrote in a report about the study. 

In Africa, the gene variant may account for 11 percent of HIV infections, the researchers said, and could help explain why Africans have been hit harder by AIDS compared with people in other parts of the world.

Sexual behavior and other social factors cannot fully explain why more than two-thirds of the 33 million people with HIV worldwide live in sub-Saharan Africa. And genes may be playing a critical role, the researchers said.

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

Although the genetic variation was found to raise a person's susceptibility to HIV infection, it also appears to hinder the progression of AIDS. In fact, those with HIV infections who have the genetic variant live nearly two years longer than those who do not have it, according to researchers.

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

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

The protein linked to the gene is known as DARC, short for Duffy Antigen Receptor for Chemokines. Those possessing the gene variant do not have the receptor on their red blood cells. 

People lacking the receptor, a type of molecular gateway into the cells, are protected against infection by a malaria parasite called Plasmodium vivax.  However, the parasite is not the one responsible for the large number of malaria deaths occurring in Africa, but is instead seen in some parts of Asia and the Middle East.

The researchers believe the gene variant originated long ago, perhaps to provide protection against a deadly strain of malaria that may have swept through large swaths of the population.

"We're probably talking about tens of thousands of years ago," Robin Weiss of University College London told Reuters.

The study examined 1,266 HIV-infected black Americans, not in an African population, in the U.S. Air Force who were monitored for roughly 20 years. They also tracked 2,000 people who were not infected with HIV. They researchers found the gene variant was far more common among the U.S. blacks infected with HIV than among those not infected.

Only a tiny percentage of people not of African descent carry this genetic variation, and it is all but absent in people of European descent, the researchers noted.

The study was published in the journal Cell Host & Microbe.

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On the Net:

• REPORT: Duffy Antigen Receptor for Chemokines Mediates trans-Infection of HIV-1 from Red Blood Cells to Target Cells and Affects HIV-AIDS Susceptibility

Source: redOrbit Staff & Wire Reports

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