Medroxyprogesterone acetate increases HIV-1 infection of unstimulated peripheral blood mononuclear cells in vitro

Objective: Several observational studies suggest that medroxyprogesterone acetate (MPA) injectable contraceptives may increase a woman's risk of sexual HIV-1 acquisition. In-vitro studies are conflicting, mainly due to differences in the type of progestin studied or activation status of the primary cells. We sought to determine whether MPA increases infection of unstimulated peripheral blood mononuclear cells (PBMCs). Methods: Freshly isolated PBMCs from normal blood donors were treated with physiologic MPA concentrations ranging from 0.003 to 5 ng/ml and infected with GFP-tagged R5-tropic or X4-tropic HIV-1 pseudoviruses by spinoculation. The infection was limited to a single cycle. Cells were stained with CD3, CD8 and CD14. Infection was quantified as the percentage of GFP cells by flow cytometry. Results: Absolute infection was greater among unstimulated MPA-treated CD3⁺CD8^- T cells vs. untreated cells across MPA concentrations of 0.003-3 ng/ml using R5 (P<0.003) and 0.03-0.3 ng/ml using X4 (P<0.005) pseudovirus. There was increased relative infection of CD3⁺CD8^- T cells in MPA-treated whole PBMC cultures but not after monocytes were depleted (P<0.02). HIV-1 infection of stimulated PBMC showed no differences in R5 or X4 infection across all MPA concentrations (P>0.5). Conclusion: The CD3⁺CD8^- T-cell population of MPA-treated unstimulated PBMCs were more susceptible to HIV-1 infection than untreated cells. The increased infection was partly due to monocytes and was lost when PBMC were exogenously stimulated. These data provide confirmation of a biological association between MPA exposure and increased susceptibility to HIV-1 infection, particularly among women who inject drugs.