Genetic Variation Responsible for HIV Resistance Not Caused by Black Plague, Study Says

Some people with a genetic variation in the CCR5 receptors of their immune cells are resistant to HIV, but a theory that the mutation was caused 800 years ago by selective pressure from the Black Plague appears to be unfounded, according to a study published in this week's issue of the journal Nature, Reuters reports. People with the variation, called the CCR5-delta-32 mutation, are resistant to HIV because the virus can only latch on to normal CCR5 receptors when trying to enter immune cells. Dr. Donald Mosier of the La Jolla, Calif.-based Scripps Research Institute and colleagues infected mice that had normal CCR5 and mice that had the variant CCR5-delta-32 mutation with Yersinia bacterium, which caused the plague. The researchers found no difference between the groups in severity of infection or mortality rates. The CCR5-delta-32 mutation is more common in people of Northern European descent, occurring in 20% of people in areas of Scandinavia and in as few as 3% of people in southern regions of Europe. Previous research has indicated that smallpox could have caused the mutation, and the researchers now plan to infect CCR5-deficient mice with mousepox, a close relative of smallpox, to test that theory (Gale, Reuters, 2/11). Several drug companies on Wednesday at the 11th Conference on Retroviruses and Opportunistic Infections announced results from clinical trials of experimental antiretroviral drugs that target the CCR5 receptors (Kaiser Daily HIV/AIDS Report, 2/12).