The anti-herpes drug acyclovir did not reduce the risk of acquiring sexually transmitted HIV when given to men and women infected with herpes simplex virus-2 (HSV-2), according to the authors of a study reported last week at the 15th Conference on Retroviruses and Opportunistic Infections (CROI) in Boston.
Multiple studies indicate that people infected with HSV-2 are at increased risk of acquiring HIV, given that herpes sores allow HIV to easily enter the body and establish infection. There have also been studies suggesting that people coinfected with HIV and HSV-2 who use anti-herpes medications are potentially less likely to transmit HIV to their sex partners. The new research presented at CROI, however, will likely dampen the hope that these drugs can be used to reduce the risk of HIV infection among people with HSV-2.
The study, known as HPTN 039, is the largest clinical study ever conducted to examine herpes suppression as a possible means of reducing the risk of HIV transmission. The results were reported at CROI by Connie Celum, MD, of the University of Washington in Seattle, and her colleagues.
HPTN 039 was designed to determine if acyclovir—a cheap, safe and widely available generic herpes treatment—could reduce an HSV-2-positive person’s risk of acquiring HIV infection. The clinical trial was conducted at nine sites in Peru, South Africa, the United States, Zambia and Zimbabwe, and involved 3,172 total HSV-2-infected volunteers, including heterosexual women as well as men who have sex with men. The women were enrolled at the three African study sites, and the men at the six study sites in Peru and the United States.
The participants received either 400 mg twice-daily dose of acyclovir tablets or placebo. Throughout the course of the study, volunteers were extensively counseled on how to avoid exposure to HIV and were supplied with condoms.
The researchers found no evidence that the standard acyclovir regimen prevents HIV infection among HSV-2 infected people. Specifically, there were 75 new infections (3.9 percent) among the 1,637 participants who received acyclovir, while there were 64 new cases (3.3 percent) among the 1,640 participants who received placebo.
“The difference in HIV rates in the acyclovir and placebo group is not statistically significant, indicating that when acyclovir is used twice daily at the 400 mg dose, the drug does not prevent HSV-2-infected individuals from becoming infected with HIV,” says Dr. Celum. “More research is needed to understand ways to reduce HIV susceptibility among persons with HSV-2.”
