Exopolysaccharides of Lactobacillus crispatus mediate key balancing interactions with the vaginal mucosa.

Study Design

Population: human vaginal samples of healthy volunteers
Methods: integrate bacterial genetics, in vitro epithelial systems, human-derived data and proteomic approach (Olink®); Functional disruption of epsE; In human vaginal epithelial monolayers and a 3D vaginal organotypic model

Lactobacillus crispatus is a dominant member of the healthy vaginal microbiota, yet the mechanisms by which it modulates host immunity remain poorly defined, in part due to the lack of tractable in vivo models. Here, we integrate bacterial genetics, in vitro epithelial systems, human-derived data and proteomic approach (Olink®) to uncover a critical role for L. crispatus exopolysaccharides (EPS) in shaping the bacteria-vagina interactions. Comparative genomics identified a conserved EPS biosynthetic locus, with the priming glycosyltransferase gene epsE emerging as a regulatory node, in line with its distinct expression in human vaginal samples. Functional disruption of epsE abrogated L. crispatus EPS production and revealed its role for immune modulation. In human vaginal epithelial monolayers, EPS presence enhanced immune-regulatory (LAP TGF-beta-1) and anti-inflammatory (CST5) responses, whereas its absence triggered elevated pro-inflammatory cytokines (IL1β, IL6, IL8) and matrix metalloproteinase (MMP10). In a 3D vaginal organotypic model, EPS increased chemokines (CXCL5, CXCL6) linked to immune surveillance and the presence of the markers was validated in vaginal samples of healthy volunteers. These findings position EPS as a key immunomodulatory structure of L. crispatus, advancing our mechanistic understanding of host-commensal interactions and informing microbiome-based strategies to promote vaginal health.

Research Insights

Supplement	Dose	Health Outcome	Effect Type	Effect Size	Source
Lactobacillus crispatus	—	Improved Immune Regulation	Beneficial	Moderate	View source EPS presence enhanced immune-regulatory (LAP TGF-beta-1) and anti-inflammatory (CST5) responses, whereas its absence triggered elevated pro-inflammatory cytokines (IL1β, IL6, IL8) and matrix metalloproteinase (MMP10).
Lactobacillus crispatus	—	Improved Immune Surveillance	Beneficial	Moderate	View source In a 3D vaginal organotypic model, EPS increased chemokines (CXCL5, CXCL6) linked to immune surveillance and the presence of the markers was validated in vaginal samples of healthy volunteers.
Lactobacillus crispatus	—	Reduced Vaginal Inflammation	Beneficial	Moderate	View source EPS presence enhanced immune-regulatory (LAP TGF-beta-1) and anti-inflammatory (CST5) responses, whereas its absence triggered elevated pro-inflammatory cytokines (IL1β, IL6, IL8) and matrix metalloproteinase (MMP10).