Viral and Immunologic Factors Contributing to the Lack of HIV Transmission Among Couples in Rakai, Uganda

This study will look at viral and immunologic factors involved in protecting against sexually transmitted HIV infection in couples in which one partner is infected and the other is not. This study will include 50 couples who reside in Rakai, Uganda, and who have been together for at least 2 years. In some couples, both partners will be HIV-infected, in some couples only one partner will have HIV, and in some couples neither partner will have HIV. Participants undergo the following procedures at each of four study visits: * HIV counseling and testing * Medical history, including questions about personal behaviors such as sexual practices and use of condoms * Blood sample collection * Urine sample collection * Vaginal swab for women Blood, urine and vaginal fluid samples are tested for HIV and other sexually transmitted diseases, such as syphilis. Blood and vaginal samples are also tested for HIV viral levels and immune response in HIV-infected individuals and for evidence of exposure to HIV in non-infected participants. Some blood is also tested for genetic markers to investigate whether certain proteins are related to resistance to HIV infection. ...