Resting CD4+ T Cells Have Protection Against HIV, But Protection Fails When Cells Become Active, Study Shows
Resting CD4+ T cells have a "powerful" protein shield that protects them from being invaded by HIV, but the cells lose that protection when they are activated to fight an infection, allowing HIV to enter the cells, according to a paper published on Wednesday in the online edition of the journal Nature, the San Francisco Chronicle reports. CD4+ T cells play a central role in the immune system, and they are the primary type of cell that HIV attacks. However, HIV can invade CD4+ T cells only when they are active, posing an ongoing "paradox" to researchers who could not understand how HIV destroyed the immune system when about 95% of the cells are in a resting state (Russell, San Francisco Chronicle, 4/14). The shield is composed of the enzyme APOBEC3G -- A3G for short -- a small version of which is able to repel HIV and is found on resting cells. Dr. Warner Greene, senior author of the study and director of the Gladstone Institute of Virology and Immunology at the University of California-San Francisco, and colleagues found that A3G becomes a large molecule when the CD4+ T cells are activated and the shield becomes porous, allowing HIV to enter the cell (Chase, Wall Street Journal, 4/14). The scientists do not understand why the CD4+ T cells "abandon" this defense when they are activated or how the mechanics of the shield work, according to the Chronicle. The findings "open up exciting new possibilities for drug development" because scientists could design drugs that support the cells' natural defense or create similar shields in cells that are vulnerable to the virus if they understand the way the mechanism works, according to the Chronicle (San Francisco Chronicle, 4/14).This is part of the KHN Morning Briefing, a summary of health policy coverage from major news organizations. Sign up for an email subscription.