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 2013, a total of US$5.8 million was provided for HSV-2 vaccine research from the US NIH, an increase of US$3.5 million over 2012. As in previous years, commercial investors were often subsidized by public-sector institutions, such as the US NIH. Pharmaceutical and biotechnology companies investing in HSV-2 vaccine R&D include Agenus Inc., GSK, Genoccea Biosciences, Juvaris and Vical.
Genocea presented promising data on a Phase I/IIa trial of its HSV-2 protein subunit vaccine and is continuing research. In 2013, Genocea filed an initial public offering in an effort to raise US$75 million. Genocea’s most recent funding came from the BMGF. GSK’s venture arm, SR One, is also a top investor in the biotech company. GSK’s vaccine, containing a glycoprotein D (gD-2) did not show efficacy in a Phase II trial ending in 2012. Efforts to prevent HSV-2 using gD-2 subunit vaccines were ongoing for over 20 years with nearly US$100 million invested in the research.19 gD-2 is one of the proteins in Genocea’s vaccine and the other is infected cell protein.
Agenus Inc. also has an HSV-2 vaccine, presenting results in November 2013 from a Phase II study of Herpv, a recombinant therapeutic vaccine. Vical, with NIH funding,is developing a plasmid DNA-based vaccine to inhibit recurring lesions in patients latently infected with HSV-2. The program advanced to a Phase I/II trial in December 2013 after promising preclinical results.