A combined oral contraceptive affects mucosal SHIV susceptibility factors in a pigtail macaque (Macaca nemestrina) model.

BackgroundInjectable hormonal contraception may increase women's risk of HIV acquisition and can affect biological risk factors in animal models of HIV. We established, for the first time, a model to investigate whether combined oral contraceptives (COC) alter SHIV susceptibility in macaques. MethodsSeven pigtail macaques were administered a monophasic levonorgestrel (LNG)/ethinyl estradiol (EE) COC at 33% or 66% of the human dose for 60days. Menstrual cycling, vaginal epithelial thickness, and other SHIV susceptibility factors were monitored for a mean of 18weeks. ResultsMean vaginal epithelial thicknesses were 290.8m at baseline and 186.2m during COC (P=0.0141, Mann-Whitney U-test). Vaginal pH decreased from 8.5 during treatment to 6.5 post-treatment (0.0176 two-tailed t-test). Measured microflora was unchanged. ConclusionsCOC caused thinning of the vaginal epithelium and vaginal pH changes, which may increase SHIV susceptibility. 0.033mg LNG+.0066mg EE appeared effective in suppressing ovulation.