The innate immune system is at the interface between the host's immune system and the initial contact with HIV. Understanding the correlates of innate immune protection against Human Immunodeficiency Virus is an important goal for development of effective anti-HIV therapies or vaccines. Not all exposures to HIV end in infection. The innate immune system has been linked to the reduced susceptibility of HIV-exposed seronegative (HESN) female commercial sex workers in Kenya by a number of studies. This thesis is a comparison of Toll-like receptor (TLR) responses in different immune cells in peripheral blood mononuclear cells (PBMCs) from HESN and HIV negative (susceptible) female commercial sex workers (CSWs). This study tested the hypothesis that higher TLR8 responsiveness in PBMCs of HESN to ssRNA analogous to HIV's genetic material, would result in higher effector responses capable of making HIV target cells more refractory in vitro, compared to susceptible controls. The results showed that PBMCs of HESN were often hypo-responsive to TLR4 and TLR7 stimulations evidenced by often reduced cytokine responses to the corresponding ligands, but hyper-responsive to TLR8 following stimulation with ssRNA analogous to HIV's genetic material. The 'dichotomy' in TLR responsiveness of HESN PBMCs was associated with differential expression of cognate TLRs in PBMCs, and altered activation of TLR signalling pathways. The opposing pattern of TLR7 and TLR8 responsiveness corresponded to the ability of HIV to infect target cells in vitro; where pre-treatment of PBMCs with TLR7 enhanced HIV replication whereas TLR8 stimulation inhibited HIV replication. The differences in outcomes of the HIV infection assays were associated with distinct cytokine profiles, where TLR7 stimulation induced robust type I IFNs responses without proinflammatory TNF-α and IL-12 cytokine responses,while TLR8 stimulations produced type II IFN responses accompanied by robust proinflammatory responses in both groups. The cytokine milieu of HESN PBMCs prior to and following TLR4 and TLR8 stimulations was more tightly regulated, but was associated with higher activation of CD8+, NK cells, monocytes but not blood DCs. These results demonstrate that the lower activation or 'quiescent' state of HESN PBMCs did not limit the ability of their cells to recognize ssRNA analogous to HIV derived genetic material and mount potent responses capable of limiting HIV infection in vitro, supporting the overall hypothesis tested. This thesis contributes to the growing knowledge on the dichotomous outcomes between TLR7 and TLR8 treatments with respect to HIV infection that could be instrumental in the design of novel HIV inventions such as vaccines or microbicides. / May 2016

Understanding natural mechanisms of protection against HIV infection and disease progression are key priorities for informing vaccine and microbicide design. The research presented in this thesis aimed to characterize mechanisms of defence in HIV-exposed seronegative (HESN) individuals, who naturally resist infection by HIV, and HIV-controllers, who are HIV-infected, but suppress viral replication in the absence of treatment. Previous studies have linked resistance to HIV infection with low basal levels of gene transcription and reduced production of inflammatory mediators, suggesting an overall state of immune quiescence in HESN. Immune quiescence may also be protective in HIV-infected individuals, as immune activation drives disease progression. The central hypothesis of this thesis is that immune quiescence protects against HIV infection and disease progression by limiting the pool of activated target CD4+ T cells susceptible to HIV infection. This hypothesis was addressed by evaluating immune function in HESN from the Pumwani commercial sex worker cohort and HIV-controllers from the Manitoba elite controller cohort. In HESN, immune quiescence was marked by low levels of circulating activated T cells and low levels of the proinflammatory mediators IL-1α and IL-8 in the cervical mucosa. Regulatory T cells (Tregs), which suppress T cell activation, were elevated in HESN, and may represent a driver of immune quiescence. Low T cell activation and elevated Tregs were associated with reduced cellular susceptibility to infection in vitro. These data suggest that immune quiescence protects against infection by limiting the activated target CD4+ T cell pool, in support of the central hypothesis. HIV-controllers expressed low levels of the proinflammatory chemokines IP-10 and MCP-1 and low frequencies of activated T cells. These data demonstrate that immune quiescence is not only protective prior to exposure, but is also beneficial following infection. HIV-controllers also had elevated MIP-1α, reduced TGFβ and HIV-specific T cell proliferation responses, which contribute to protection by mechanisms other than immune quiescence. Taken together, these data support a role for immune quiescence in protection from HIV infection and disease progression. Mechanisms of reducing inflammation and target cell activation should be considered during future HIV vaccine and microbicide development.

Understanding natural mechanisms of protection against HIV infection and disease progression are key priorities for informing vaccine and microbicide design. The research presented in this thesis aimed to characterize mechanisms of defence in HIV-exposed seronegative (HESN) individuals, who naturally resist infection by HIV, and HIV-controllers, who are HIV-infected, but suppress viral replication in the absence of treatment. Previous studies have linked resistance to HIV infection with low basal levels of gene transcription and reduced production of inflammatory mediators, suggesting an overall state of immune quiescence in HESN. Immune quiescence may also be protective in HIV-infected individuals, as immune activation drives disease progression. The central hypothesis of this thesis is that immune quiescence protects against HIV infection and disease progression by limiting the pool of activated target CD4+ T cells susceptible to HIV infection. This hypothesis was addressed by evaluating immune function in HESN from the Pumwani commercial sex worker cohort and HIV-controllers from the Manitoba elite controller cohort. In HESN, immune quiescence was marked by low levels of circulating activated T cells and low levels of the proinflammatory mediators IL-1α and IL-8 in the cervical mucosa. Regulatory T cells (Tregs), which suppress T cell activation, were elevated in HESN, and may represent a driver of immune quiescence. Low T cell activation and elevated Tregs were associated with reduced cellular susceptibility to infection in vitro. These data suggest that immune quiescence protects against infection by limiting the activated target CD4+ T cell pool, in support of the central hypothesis. HIV-controllers expressed low levels of the proinflammatory chemokines IP-10 and MCP-1 and low frequencies of activated T cells. These data demonstrate that immune quiescence is not only protective prior to exposure, but is also beneficial following infection. HIV-controllers also had elevated MIP-1α, reduced TGFβ and HIV-specific T cell proliferation responses, which contribute to protection by mechanisms other than immune quiescence. Taken together, these data support a role for immune quiescence in protection from HIV infection and disease progression. Mechanisms of reducing inflammation and target cell activation should be considered during future HIV vaccine and microbicide development.