VIENNA—A widely anticipated presentation here at the 18th International AIDS Conference turned out to be doubly sweet. As Science reported yesterday, researchers have announced that South African women who received a vaginal gel that contains the anti-HIV drug tenofovir had a 39% lower chance of becoming infected by the virus than did those who received a placebo. But the researchers are also reporting that the microbicide gel had an even more powerful effect against herpes simplex virus-2 (HSV-2).
"It's very interesting and clearly needs to be followed," says Zeda Rosenberg, who heads the International Partnership for Microbicides, a nonprofit based in Silver Spring, Maryland.
Quarraisha and Salim Abdool Karim, the husband-and-wife team who led the study, called CAPRISA 004, presented the bulk of the data during an afternoon session today. As Salim explained, nearly half of the women did not have HSV-2 infection at the start of the study. Of this group, 58 of 224 women in the placebo arm of the study became infected with HSV-2 versus 29 of the 202 who received the gel. The difference, 51%, was statistically significant, and the microbicide's effect on HIV infection was independent of the HSV-2 finding, noted Salim Abdool Karim.
The finding is especially heartening because HSV-2 infection increases a person's risk of becoming infected by HIV-1. "Once confirmed and replicated, tenofovir gel has the potential to alter the course of the HIV epidemic," said Salim Abdool Karim.
As he explained, a precursor compound to tenofovir actually is a marketed drug to treat HSV-2 infection. But few AIDS researchers knew the connection, and many were stunned that tenofovir had such a powerful impact on HSV-2.
"It goes to show that sometimes you learn unexpected things from well-designed science projects," says Robert Grant of the University of California, San Francisco, who is studying a related prevention strategy that uses an anti-HIV pill to protect uninfected people. "It's a nice example of how prevention interventions can synergize with each other."
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