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
In 2011, a total of US$11.8 million was provided for HSV-2 vaccine research. While the US NIH provided the majority of funding, the ARC and Australia’s NHMRC also provided funding for R&D. Commercial investors were often subsidized or entirely funded by public-sector institutions. Vical was awarded a grant by the US NIH for its HSV- 2 vaccine program, which is developing a plasmid DNA-based vaccine to inhibit recurring lesions in patients latently infected with HSV-2. Preclinical results from Vical show a significant reduction in viral lesion occurrence. Other pharmaceutical and biotechnology companies investing in HSV-2 vaccine R&D include GSK, Genocea Biosciences and Juvaris.
In 2010, GSK decided to halt its NIH-funded Phase III trial assessing the company’s HSV vaccine, Simplirix, because the vaccine did not show efficacy against HSV-2. In mid-2012, results of the trial were published in the New England Journal of Medicine, validating GSK’s decision to halt development of the vaccine. GSK and NIH investigators are conducting additional studies to gain further understanding of the results.