This article is part of our October 2022 Immune Health special issue. Download the full issue here.
To investigate the effect of a live biotherapeutic vaginal agent containing L crispatus CTV-05 (LACTIN-V) on genital immunology and key vaginal bacteria
This study suggests that the vaginal application of LACTIN-V is associated with sustained reductions in mucosal inflammation and possibly improved mucosal barrier function.
A substudy of a randomized, placebo-controlled, phase 2b trial of LACTIN-V to reduce bacterial vaginosis recurrence
The original study recruited 228 women (aged 18–45 years) to partake in a phase 2b trial of LACTIN-V to reduce bacterial vaginosis recurrence. The study subset reviewed here included 66 highly adherent women who were randomly selected from the original study (32 in the LACTIN-V group; 34 in the placebo group). The median age was 33 years.
None of the women tested positive for human immunodeficiency virus (HIV), syphilis, Neisseria gonorrhoeae, Chlamydia trachomatis, or Trichomonas vaginalis at baseline. Women were negative for pregnancy and urinary tract infection. Baseline participant characteristics and sexual behaviors, including recent sex and hormonal-contraceptive use and ethnicity, did not substantially differ between groups. Women who met at least 3 of 4 clinical Amsel criteria for bacterial vaginosis and had a Nugent score of 4 to 10 from Gram staining were eligible.
All participants received a 5-day course of vaginal metronidazole 0.75% gel. After this treatment, they were randomly assigned to receive either LACTIN-V or placebo, applied vaginally once per day for 5 days for the first week and then twice per week for 10 more weeks. Follow-up visits occurred 4, 8, 12, and 24 weeks after enrollment.
Lactobacillus crispatus CTV-05 (LACTIN-V) is a live biotherapeutic product that contains a naturally occurring strain of L crispatus. LACTIN-V is composed of a powder containing 2 x 109 colony-forming units of L crispatus CTV-05 preserved with inactive ingredients and administered by a prefilled applicator.
Study Parameters Assessed
Investigators assayed soluble immune factors and the absolute abundance of bacterial taxa using multiplex ELISA and quantitative polymerase chain reaction (PCR).
The primary outcomes were the vaginal interleukin 1 alpha (IL-1a) and soluble E-cadherin concentrations at 24 weeks (ie, 13 weeks after treatment cessation, whether LACTIN-V or placebo).
Other outcomes included vaginal concentrations of soluble immune factors and the absolute abundance of key vaginal bacteria including L crispatus, L crispatus strain CTV-05, L iners, L jensenii, L gasseri, Gardnerella vaginalis, Atopobium vaginae, Megasphaera species, and Prevotella species.
LACTIN-V treatment was associated with significantly lower concentrations of the proinflammatory cytokine IL-1a (P=0.042), a marker of inflammation, and soluble E-cadherin (P=0.035), a biomarker of epithelial barrier disruption.
In addition, among the 6 exploratory endpoints, LACTIN-V was associated with elevated concentrations of induced protein 10 (IP-10) at 23 weeks. Interferon (IFN) alpha 2a and IL-17A were undetectable in more than 50% of the samples. Detectability of IFN-alpha 2a or IL-17A was not significantly associated with treatment.
This study was funded by the Canadian Institutes of Health and Research and the National Institutes of Health (NIH) National Institute of Allergy and Infectious Diseases (NIAID). One of the authors of this study, CR Cohen, MD, is chair of the scientific advisory board for Osel, the biotherapeutics company whose product pipeline includes LACTIN-V. He reports grants from NIAID and the NIH National Institute of Child Health and Human Development. He holds stock options in Osel and Evvy. Another author, B Coburn, PhD, reports grants from the Western Foundation, Canadian Institutes of Health Research, Canadian Cancer Society, McLaughlin Foundation, National Cancer Institute, and Cystic Fibrosis Foundation and receipts for research from Nubiyota, a microbiome therapeutics company focused on the development of novel microbiota-based drugs to restore gut equilibrium. Coauthor R Kaul reports a grant from Canadian Institutes of Health Research.
Practice Implications and Limitations
Bacterial vaginosis (BV) affects 15% to 50% of reproductive-aged women worldwide1 The recurrence rate is quite problematic, and even after treatment with an indicated antibiotic agent, 20% to 75% of women have a recurrence within 3 months.2 BV is associated with increased risk of sexually transmitted infections (STIs) including HIV, as well as premature birth.3 BV also leads to negative emotional, sexual, and social effects and is an economic burden for patients. If we could reduce the risk of recurrence, let alone promote primary prevention, we would be helping provide a much-needed solution in women’s health.
I’ll get to the study implications and limitations of the current study in a moment, but first, let’s look at the original study that spawned the current substudy. I see that study as having greater practice implications. The original study (Cohen et al, NEJM, 2020) involved a phase 2b trial to assess whether treatment with LACTIN-V after vaginal metronidazole for BV lowered the incidence of recurrence of BV. Women aged 18 to 45 years with BV completed a 5-day course of vaginal metronidazole gel (0.75%). Within 48 hours of completing that treatment, they were randomized to vaginal LACTIN-V for 11 weeks vs placebo. This intervention required participants to insert an applicator nightly for 5 days, then twice weekly for 10 weeks. The primary outcome was the percentage of women who had a recurrence of BV by week 12. Investigators randomized 228 women, with 152 in the treatment group and 76 in the placebo group. By week 12, BV recurrence was significantly lower in the LACTIN-V group, with a 30% rate of recurrence in the LACTIN-V group (compared to a 45% rate of recurrence in the placebo group) and with a sustained effect in the treatment group at week 24.
The recurrence rate is quite problematic, and even after treatment with an indicated antibiotic agent, 20% to 75% of women have a recurrence within 3 months.
Now, to our current substudy, which resulted in a sustained reduction in genital inflammation and a biomarker of epithelial integrity. LACTIN-V was associated with the concentrations of soluble immune factors and an abundance of multiple bacterial taxa, which bodes well for genital immunity. These sustained genital immune effects were primarily mediated by a reduced amount of bacterial vaginosis–associated taxa, especially Prevotella spp and Megasphaera spp, and to a lesser extent, an elevated amount of L crispatus. There are strong links between vaginal microbiota and HIV risk, suggesting that promoting a predominance of L crispatus in the vagina might reduce the risk of HIV.
Women with L crispatus predominance in their vaginal ecosystems also exhibit fewer transitions to bacterial vaginosis–type microbiota than women with other Lactobacillus species dominating, such as L iners predominance. This suggests that L crispatus can competitively inhibit or exclude inflammatory bacterial vaginosis–associated bacteria. This is, in part, mediated by the production of lactic acid and antimicrobial metabolites. We have other evidence that shows that L crispatus is a key producer of lactic acid in the vagina.4
There are some limitations of the study. Investigators assessed STIs only at initial screening, and they only tested for them again if women were symptomatic. The stage of the menstrual cycle was not recorded unless the women were menstruating. A fluctuation in the normal sex hormones is a potential determinant of genital immunology and pH. The testing used was targeted qPCR rather than 16SrRNA gene sequencing, which limited the ability to evaluate the vaginal microbiota and identify contributions by other microbes. The study involved only US American women, though it was an ethnically heterogeneous cohort.
Conflict of Interest Disclosure
Dr Tori Hudson is the co-owner of a women’s supplement company, Vitanica, which offers a broad range of women’s health, nutritional, and herbal products including oral and vaginal-use probiotic species and strains for prevention and treatment of urogynecological conditions. She is also a medical advisor to Nutritional Fundamentals for Health, Symphony, Integrative Therapeutics, and Gaia Herbs Pro.