Vaginal microbe-binding antibody interactions with a Lactobacillus crispatus live biotherapeutic following treatment for bacterial vaginosis

ABSTRACT The vaginal application of LACTIN-V, a live biotherapeutic containing Lactobacillus crispatus CTV-05, reduces the recurrence of bacterial vaginosis (BV) and promotes L. crispatus colonization; however, colonization success is variable. In 65 women with BV randomized to LACTIN-V or placebo following metronidazole treatment, we evaluated whether pre-existing or treatment-induced vaginal L. crispatus CTV-05-binding antibodies shaped colonization outcomes. CTV-05-binding IgA and IgG were commonly detected prior to BV treatment, with IgA predominating. Neither total nor CTV-05-binding IgA or IgG predicted colonization resistance; instead, baseline CTV-05-binding IgA was associated with colonization permissiveness. LACTIN-V application did not change overall vaginal antibody concentrations or induce CTV-05-binding IgA or IgG. Overall, L. crispatus CTV-05-binding IgA and IgG were common but are not a barrier to CTV-05 colonization, nor induced by LACTIN-V application. IMPORTANCE Recent clinical trials show that vaginal live biotherapeutics (therapeutic grade probiotics) containing the “optimal” vaginal species Lactobacillus crispatus have the potential to enhance vaginal health. However, application of these live biotherapeutics often does not lead to successful colonization of the vagina by L. crispatus . Prior studies have shown that the vagina often contains antibodies that bind L. crispatus , and we used samples from a clinical trial of the product Lactin-V to test the hypothesis that such antibodies may be induced by application and prevent colonization. Importantly, we confirmed that these antibodies were frequently found in the vagina of participants before application, but that they did not block (and may even have helped) colonization, and were not induced by the product. This is important information for the growing field of vaginal live biotherapeutics. CLINICAL TRIALS This study is registered with ClinicalTrials.gov as NCT02766023 .