Defining the HIV neutralizing activity of antiproteases within the female genital tract and evaluating the HIV inhibitory mechanism of Serpin B1
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The HIV/AIDS pandemic continues to be one of the most devastating global health pandemics in history. With women accounting for approximately 60% of all new HIV infections, preventative strategies that provide women with the ability to protect themselves is imperative. To this end, identifying natural factors expressed in the female genital tract (FGT) capable of inhibiting HIV may prove to be novel candidates for female-controlled microbicide preventative strategies. The work in this thesis examined the differences in CVL (cervicovaginal lavage) composition between HESN (HIV-exposed seronegative) women and HIV-susceptible women. Distinct differences in the female genital tract proteomes, and HIV inhibitory activity exhibited by CVL, were observed among women highly exposed to HIV compared to women at lower exposure. Furthermore, while HESN women as a group did not demonstrate stronger inhibitory effects compared to susceptible women from the Pumwani cohort, it was apparent that CVL from individual women was capable of inhibiting HIV consistently over longitudinal analysis. From the antiproteases that were identified as over-expressed within the CVL of HESN women, Serpin B1 exhibited the strongest and most consistent HIV inhibitory activity. The mechanism for this activity does not appear to be directly against HIV but rather through effects exerted on HIV target cells. Specifically, Serpin B1 alters the proliferative capacity and induces early apoptotic markers on these cells. Proteomic pathway analysis of the proteins over-expressed following treatment, suggests that Serpin B1 may up-regulate the expression of proteins associated with inhibition of the mTOR pathway. This inhibition may be caused by induction of increased production of ROS (reactive oxygen species) by macrophages or through Granzyme A activity, and subsequent dysfunction of the mitochondria, potentially inducing an autophagic state. However, this would need to be confirmed with further molecular studies. These results defined a potential mechanism of HIV inhibition for Serpin B1. Hence, the overabundance of Serpin B1 in the CVL of HESN women may, in fact, be contributing to their protective phenotype against HIV infection. These findings suggest that Serpin B1 could be considered as a candidate in future microbicides. However, these findings must be validated in in vivo models.