HSV-2 Suppression for HIV Prevention
What is HSV-2 Suppression for HIV Prevention?
Why is HSV-2 suppressive treatment or HSV-2 prevention a possible HIV risk reduction strategy? Genital herpes is caused by the sexually transmitted virus herpes simplex virus type 2 (HSV-2). There is a possibility that prevention of HSV-2 or suppressive use of antivirals—acyclovir and valcyclovir—can reduce the recurrence of HSV-2 lesions. There is also the possibility that HSV-2 infection can be prevented by a vaccine. This may have the added benefit of reducing the risk of HSV-2 infected/HIV-uninfected people acquiring HIV, and of HSV-2/HIV dually-infected people transmitting HIV to their sexual partners. HSV-2 is found in 20 to 30 percent of HIV-uninfected people in industrialized world compared to 40 to 70 percent of HIV-uninfected people in resource-limited settings. HSV-2 prevalence is highest (>80%) in HIV-infected people. Therefore, preventing HSV-2 or treating HSV-2 in both HIV negative and positive people could potentially have an impact on the HIV epidemic.
HSV-2 Suppression Investment
Although HSV-2 suppression with acyclovir has not been shown to affect HIV acquisition,prevention of HSV-2 infection in HIV-negative people may be an effective HIV prevention strategy. The NIH provided all of the public sector investment for research into HSV-2 vaccines in 2010, a total of US$908,000. HSV-2 vaccines have also received modest commercial investment from pharmaceutical companies (such as GSK) and from biotech companies (such as BioVex, Genocea Biosciences, Juvaris, and Vical). Results from the NIH funded a Phase III trial to assess GSK’s HSV vaccine released in September 2010 showed that the vaccine did not prevent HSV-2 infection. These disappointing trial results may further discourage investment in this area despite its warranting further research and the need for an HSV-2 vaccine. One unexpected and exciting finding from CAPRISA 004 was that among women who were uninfected with HSV-2 at the start of the trial, those who used 1% TDF gel were at 51% lower risk of acquiring HSV-2, as compared to HSV-2 negative women using placebo. This finding may guide new research and suggests an additional important benefit to women using the 1% TDF gel.
