Wednesday, July 16, 2008
A gene which apparently evolved to protect people from malaria increases their vulnerability to HIV infection by 40%
People of African descent have a variation of the "DARC" gene which may interfere with their ability to fight HIV in its early stages. The Cell Host and Microbe study says the gene accounts for millions of extra HIV cases in sub-Saharan Africa. Research at University College London and the University of Texas focused on the Duffy Antigen Receptor for Chemokines (DARC) gene. The gene influences the levels of chemicals called chemokines, which play a role in the body's defences against viruses, and a variation is held by approximately 90% of Africans. The origins of the variation are unclear, but it is thought to have evolved in response to widespread malaria outbreaks by offering protection against that disease. The researchers did not use volunteers living in Africa, but analysed data from a 25-year study of Americans from different ethnic backgrounds with HIV. They calculated that, after taking account of social and economic differences, people with the genetic variation were 40% more likely to be susceptible to the illness. If the gene variant were not present in sub-Saharan Africa, they said, they would expect to see approximately an 11% lower burden of HIV in the region. An estimated 24.5 million people are living with the disease there, and there are approximately 2 million deaths per year.