Semen Protects HIV From Microbicide Attack

Microbicides that kill HIV in the lab often fail in clinical trials. A study finds that semen may be the culprit. Cynthia Graber reports. November 14, 2014 | |

They were thought to have great promise in the fight to stop the . Indeed, vaginal microbicides did a fine job killing in the lab. But they failed to work in clinical trials.

In previous studies, scientists had looked at the HIV virus on cells protected by microbicides. But the latest tests evaluated microbicides in the more real-world situation where semen is present. And semen stopped the microbicides from working. Probably because semen contains protein fragments that help HIV to attach to cell surfaces and infect cells.

The research is in the journal Science Translational Medicine. [Onofrio Zirafi et al, ]

There’s good news, though—a drug not currently used as a microbicide did seem to offer protection. It’s an antiretroviral called Maraviroc. Conventional microbicides target the virus itself. But Maraviroc binds to receptors on host cells. That action forms a barrier that prevents the HIV from attaching to the cell. Maraviroc is currently approved as an HIV drug, and is being considered as a microbicide to try to stop infection in the first place.

The research is a reminder that, in drug testing, context is crucial.

—Cynthia Graber