A Study of Acyclovir to Help Prevent HIV Infection in People With Genital Herpes

Genital herpes (HSV-2) is the most common cause of genital sores worldwide, and the presence of genital sores is a significant risk factor for becoming infected with HIV. This study will test the effectiveness of twice-daily dosing of acyclovir, a commonly prescribed anti-herpes drug, in preventing HIV infection in HSV-2 infected women who sleep with men (WSM) and men who sleep with men (MSM). Study hypothesis: Given that genital herpes is a significant risk factor to HIV acquisition, twice-daily HSV-2 suppressive therapy - 400 mg of acyclovir - will prevent HIV infection among high risk, HSV-2 seropositive WSM and MSM.