(51) Lactobacillus crispatus mitigates Group B Streptococcus-induced inflammation in the cervicovaginal epithelium

Group B Streptococcus (GBS) is a common vaginal microbe involved in adverse perinatal outcomes, including preterm birth, chorioamnionitis, and neonatal sepsis. Features of vaginal ecosystems may modify GBS pathogenicity. Previous work has shown that Lactobacillus crispatus (LC), a marker of reproductive health, mitigates proinflammatory cytokines in response to select vaginal pathogens. We sought to investigate the effect of LC on GBS-mediated inflammation in the cervicovaginal epithelium.


Study Design:

We leveraged an in vitro epithelial-microbial co-culture model. Ectocervical, endocervical, and vaginal epithelial cells were treated with 10⁵ CFUs of LC for 24h. Cells were then treated with 10⁴ CFUs of GBS clinical isolates (serotypes IA, III, and IV) for an additional 24h. Concentration of proinflammatory cytokine IL-8 was measured in cell culture media by ELISA. Cytotoxicity was assessed using LDH assays. Outcomes were compared by one-way ANOVA with correction for multiple comparisons. Microbial count (CFU/well) was measured on De Man-Rogosa-Sharpe and Granada agar plates to select for GBS growth.  



Results:

LC had no effect on IL-8 expression, while all GBS serotypes induced IL-8 across cells (p < 0.05 for all, Fig. 1). LC rescued GBS induction of IL-8 to near basal levels (p < 0.05 for all, Fig. 1). LC did not alter LDH in GBS-treated cells (data not shown), indicating that IL-8 reduction was not attributable to cell death. To test if immune mitigation occurred due to LC outcompeting GBS growth, we assessed microbial counts at the time of IL-8 measurement. LC did not alter the number of viable GBS colonies, and unexpectedly no live LC was detected (Table 1).



Conclusion:

LC mitigates host inflammatory response to a vaginal microbe implicated in adverse pregnancy outcomes. Microbial competition does not appear to underlie this protective effect, suggesting that immune-mediated mechanisms are at play. Whether LC microbial components or secreted factors, such as metabolites, modify GBS-epithelial interactions warrants future investigation. University of Pennsylvania Research Foundation Award (KDG)