 The amount of maraviroc compared with the drugs in the current drugs used for PrEP tenofovir emtricitabine in the blood and genital tract of HIV-negative healthy female volunteers before, during, and after they are given maraviroc versus tenofovir emtricitabine for 7 days will be measured. We will also study immune cells from the blood and genital tract from these women to see if maraviroc, tenofovir, or emtricitabine have an effect on these cells that would prevent them from becoming infected with HIV. 