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 Global public-sector and philanthropic investment in HSV-2 suppression for HIV prevention using acyclovir totaled US$51 million from 2002 to 2008. In May 2009, the results from the Partners in Prevention trial were released. The Partners trial, conducted at 14 sites in seven African countries, found that on going suppressive acyclovir therapy for HSV-2 in HIV-positive people did not reduce their risk of transmitting HIV to their HIV-negative partners. The trial also found that acyclovir treatment does not reduce the risk of acquiring HIV, but trial investigators saw a 0.25 log reduction in plasma HIV level in the acyclovir suppression group. Although this modest reduction in plasma HIV level with acyclovir suppression did not translate to reduced HIV transmission, there was a reduction in CD4 decline and HIV disease progression.
The Working Group has identified over US$7 million in investment in HSV-2 vaccine research. HSV-2 vaccines have received commercial investment from pharmaceutical companies such as GSK and Sanofi Pasteur and from biotech companies such as BioVex, GenVec, and Vical. Because the Working Group was unable to verify investment by some companies engaged in HSV-2 vaccine research, US$7 million is likely an underestimation of this investment. Future commercial investment may be positively or negatively affected by the results from the Phase III trial of its HerpeVac vaccine as a preventive HIV vaccine for genital herpes in HSV-1– and -2 seronegative young women. This NIH-funded trial expects to release results in late 2010.