Virologic and Immunologic Factors Contributing to the Lack of HIV-1 Transmission in HIV-Discordant Couples in Rakai, Uganda

Understanding the factors that contribute to the transmission of human immunodeficiency virus (HIV) infection is of great importance for the development of preventive and therapeutic strategies. Evidence suggests that a number of host immunologic and virologic factors play critical roles in protection against sexually transmitted HIV infection in HIV-discordant partners. Among these, the antiviral role of CD8+ T cells in HIV-infected individuals has been extensively studied. At least two types of CD8+ T cell-mediated antiviral activities have been described in HIV infection. The first is a suppressive activity against HIV involving lysis of infected cells in an antigen-specific, HLA-restricted fashion, while the second mechanism inhibits viral replication via either cell- or soluble mediated factors in the absence of cell killing. It has been demonstrated that cytotoxic CD8+ T lymphocytes (CTL) are present in both cervical and peripheral blood mononuclear cells (PBMC) from a subpopulation of highly-HIV-exposed but persistently seronegative individuals. However, studies addressing the effect of non-cytotoxic soluble factor-mediated antiviral activity by CD8+ T cells in preventing seroconversion in HIV-discordant couples have been lacking. This study proposes to examine the role of CD8+ T cell-derived CC-chemokine activities and the copy numbers of one of the chemokine genes, CCL3L1, along with other host anti-HIV and virologic factors in resistance to HIV infection in persistently seronegative HIV-discordant partners of HIV infected individuals.