People of African descent commonly do not express DARC on their red blood cells - this gene variation has been found to increase the risk of HIV/AIDS infection.

Researchers have discovered that people of African descent commonly carry a genetic variation that protects them against malaria, which in turn makes them up to 40% more susceptible to HIV/AIDS infection – proving that sexual behaviour and social factors are not the only explanations for the spread of the disease.

The 22-year study also revealed that those carrying the gene, who are also HIV-positive, have a survival rate two years higher than those without the gene because it causes AIDS to develop more slowly.

It is all down to a gene called the Duffy Antigen Receptor for Chemokines (DARC), which influences the levels of inflammatory and chemokines, anti-HIV blood factors.

Professor Robin Weiss, from the University College London (UCL), is a leading international authority on HIV and AIDS, and co-author of the study. He explained the significance of the DARC gene: “In sub-Saharan Africa, the vast majority of people do not express DARC on their red blood cells and previous research has shown that this variation seems to have evolved to protect against a particular form of malaria. However, this protective effect actually leaves those with the variation more susceptible to HIV.”

The gene has been described by the lead author of the study, Professor Sunil K. Ahuja from the University of Texas, as a “double-edged sword” because of its two effects. It is estimated that the gene variation may be responsible for around 11% of HIV cases in sub-Saharan Africa, where as many as 25 million people are infected. However, according to the UN’s Roll Back Malaria partnership, there are 300 million severe cases of malaria every year around the world, of which 90% are reported in Africa.

The full study is published in Cell Host & Microbe journal.