In a paper published today in the journal Nature, Joseph Sodroski and his colleagues at Harvard University identify this factor as a protein called TRIM5-alpha. Preventing TRIM5-alpha activity in monkey cells made infection with HIV possible, the researchers report, whereas adding the protein to human cells prevented HIV from taking hold. The protein may function by inhibiting the virus’s ability to shed its protective coating, which must be removed before the virus can replicate.

The team’s discovery lays the foundation for many creative approaches to developing new therapies for HIV infection and AIDS, Sodroski says. One possibility is that monkey TRIM5-alpha could be delivered to HIV patients via gene therapy to rescue as-yet-uninfected cells. Alternatively, Sodroski offers, because humans make a protein that is 87 percent identical, investigators might also focus on rendering the human version of TRIM5-alpha more potent. --Alla Katsnelson