Evolutionary Effect

A human gene that evolved over millions of years that helps protect Africans from malaria unfortunately also may make them more prone to HIV infection, scientists report in the journal Cell Host and Microbe. The gene, called DARC-46C/C genotype, is carried by about 90% of Africans and about two thirds of African-Americans. It blocks a receptor on red blood cells that malaria-causing protozoa use to infect the cells. But blocking these receptors also prevents a process where red blood cells trap and hold HIV, rendering the virus unable to attack CD-4 cells. The researchers estimate that carriers of the gene have a 40% greater risk of HIV infection, which they say helps to explain the high HIV prevalence rates in African nations and which may be a factor in HIV's disproportionate impact on African-Americans.