THE ROLE OF SEMEN TRANSFORMING GROWTH FACTOR BETA 1 IN MODULATING IMMUNE RESPONSES DURING HIV-1 INFECTION

Abstract

Thirty five million people are currently living with HIV-1 today with women accounting for half of infected individuals globally. Sexual transmission is the main route of HIV transmission with approximately 40% of HIV infections occurring when the mucosal lining of the female genital tract (FGT) is exposed to HIV in semen from an infected male partner. Seminal plasma (SP), the fluid portion of semen, is a complex fluid which plays an immunomodulatory role in the FGT for successful conception, largely due to its high concentrations of TGF-β1. Several factors in SP from HIV-uninfected men have been shown to either inhibit or enhance HIV infection in target cells, however it is not clear how SP from HIV infected men would modulate genital epithelial cells (GECs), the first cells that encounter HIV in the FGT. The overall goals of this thesis were to compare inflammatory and regulatory cytokine concentrations in SP from HIV-uninfected and infected men, and subsequently compare GEC cytokine responses following exposure to SP from HIV-uninfected and HIV-infected men. I also investigated how SP and TGF-β regulated cytokine production and barrier function in GECs in the presence of HIV. The results summarized in this thesis demonstrated that HIV infection leads to different cytokine profiles in SP, based on stage of HIV-1 infection. HIV-infected men in acute stage contained higher levels of proinflammatory cytokines in their SP compared to HIV-uninfected and chronically infected men (CI men) which subsequently lead to higher levels of proinflammatory cytokines from GECs compared to CI men. In the follow up to this study we found that active TGF-β, which was found in higher concentrations in SP from CI men and led to decreased inflammatory response from GECs, was compartmentalized between blood plasma and seminal plasma. Higher levels of active TGF-β in SP correlated with decreased semen viral load and the immune activation marker sCD14 leading us to believe that ART-naive CI men in our cohort were naturally controlling their immune activation status, as active TGF-β levels were lower in ART-treated men. Short-term exposure of GECs to SP from CI men or TGF-β at comparable concentrations to SP protected the GEC barrier against HIV by decreasing inflammatory cytokines and preventing tight junction breakage. However, long-term exposure to TGF-β in the presence of HIV further increased inflammation in GECs suggesting a biphasic role for TGF-β in the FGT. This body of work summarized in this thesis demonstrates for the first time how semen from HIV-infected men modulates FGT epithelial cell cytokine responses and barrier function, an important consideration in the design of local therapeutic strategies to protect the FGT against HIV infection.