In a phase-IIa trial, we investigated the influence of 90 days continuous-delivery tenofovir (TFV) intravaginal rings (IVRs) with/without levonorgestrel (LNG) on the genital microbiota of Kenyan women. Eligible women (n = 27; 18-34 years; negative for HIV, sexually transmitted infections, and Amsel-bacterial vaginosis) were randomized 2:2:1 to use of IVRs containing TFV, TFV/LNG, or placebo. Using vaginal wall and IVR swabs at IVR insertion and removal, the genital microbial composition was determined using 16S rRNA gene sequencing. The presence of Candida spp. was determined using qPCR. The vaginal total bacterial burden appeared to decrease with TFV and TFV/LNG IVR use (log100.57 and log100.27 decrease respectively; p > 0.05). The TFV/LNG IVR was more 'stabilizing': 50% of the participants' microbiota community state types remained unchanged and 50% shifted towards higher Lactobacillus abundance. Specifically, TFV/LNG IVR use was accompanied by increased abundances of Lactobacillus gasseri/hominis/johnsonii/taiwanensis (16.3-fold) and L. fermentum/reuteri/vaginalis (7.0-fold; all p < 0.01). A significant shift in the overall microbial α-diversity or β-diversity was not observed for either IVR, and IVR use did not influence Candida spp. prevalence. TFV/LNG and TFV IVRs did not adversely affect the genital microbiota and are safe to use. Our findings support further studies assessing their efficacy in preventing HIV/HSV-2 and unintended pregnancies.
Trial registration: ClinicalTrials.gov NCT03762382.
© 2022. The Author(s).