The goal of Research Project III (Evaluation of AFE inhibitors for protection from SHIV vaginal challenge in macaques) is to evaluate the safety and potency of suitably formulated combinations of AFE inhibitors in the rhesus macaque vaginal challenge model. The Leader will be Ronald Veazey, DVM, PhD, at the Tulane National Primate Research Center, Tulane, LA. We will receive inhibitors and formulations from Core A after confirmation of their potency and non-toxicity in the in vitro models (Research Projects I and II, and Core A). We will examine the safety of the inhibitors and formulations after topical application to the macaque vagina, by performing colposcopy and vaginal biopsy after repeated vaginal administrations of the drugs, to ensure they do not cause local inflammatory responses. Inhibitors with suitable safety profiles will be assessed, alone and in combination, for their ability to prevent the vaginal transmission of the R5 SHIV-162P3 challenge virus, and/or the X4 virus SHIV-89.6P. The outcome of infection will be determined by measuring plasma viremia and confirmed by Western blots for anti-viral antibodies. We may also explore the ability of selected inhibitors to prevent vaginal transmission, or to counter established infection, after systemic or oral administration, if we judge it likely that this information will assist us in evaluating safety and toxicity profiles. For efficacy studies, we will primarily use progesterone-treated macaques, in which the vaginal epithelium is thinned prior to vaginal challenge. This enables us to infect >90% of control animals with a relatively low challenge dose (300 TCID50). This model will also be used for evaluating compound safety as the thin vaginal epithelium allows much more sensitive detection of vaginal inflammation. However, we will also explore the potential of the multiple, low dose vaginal challenge model, administering a much lower dose (10 TCID50) of virus weekly to macaques without prior progesterone treatment. These studies will help identify the most suitable AFE inhibitors for advancement into human safety trials in Research Project IV.