The progestin-based hormonal contraceptive Depot Medroxyprogesterone Acetate (DMPA) is widely used in sub-Saharan Africa, where HIV-1 is endemic. Meta-analyses have shown that women using DMPA are 40% more likely than women not using hormonal contraceptives to acquire Human Immunodeficiency Virus (HIV-1). Therefore understanding how DMPA increases susceptibility to HIV-1 is an important public health issue. Using C57BL/6 mice and our previously optimized humanized mouse model (
NOD-Rag1 tm1Mom Il2rg tm1Wjltransplanted with hCD34-enriched hematopoietic stem cells; Hu-mice) where peripheral blood and tissues are reconstituted by human immune cells, we assessed how DMPA affected mucosal barrier function, HIV-1 susceptibility, viral titres, and target cells compared to mice in the diestrus phase of the estrous cycle, when endogenous progesterone is highest. We found that DMPA enhanced FITC-dextran dye leakage from the vaginal tract into the systemic circulation, enhanced target cells (hCD68+ macrophages, hCD4+ T cells) in the vaginal tract and peripheral blood (hCD45+hCD3+hCD4+hCCR5+ T cells), increased the rate of intravaginal HIV-1 infection, extended the window of vulnerability, and lowered vaginal viral titres following infection. These findings suggest DMPA may enhance susceptibility to HIV-1 in Hu-mice by impairing the vaginal epithelial barrier, increasing vaginal target cells (including macrophages), and extending the period of time during which Hu-mice are susceptible to infection; mechanisms that might also affect HIV-1 susceptibility in women.