Synthetic bacterial consortia transplantation attenuates vaginal inflammation and modulates the immune response in a mouse model of Gardnerella vaginalis-induced bacterial vaginosis

Abstract

This study aimed to evaluate the efficacy of synthetic bacterial consortia transplantation (SBCT) and compare it with VMT (vaginal microbiota transplantation) in a mouse model of Gardnerella vaginalis-induced Bacterial vaginosis (BV). A murine model of G. vaginalis-induced BV was established, and mice were treated with SBCT, VMT, or saline. Histopathological changes, inflammatory cytokine levels, pro-inflammatory biomarker expression, helper T cell transcription factor expression, and vaginal microbiota composition were assessed. SBCT and VMT effectively suppressed G. vaginalis growth, reduced inflammation, and restored vaginal microbiota diversity. Both treatments attenuated epithelial damage, downregulated pro-inflammatory cytokines (IL-1β and IL-8), and upregulated the anti-inflammatory cytokine IL-10. SBCT and VMT also inhibited NF-κB activation, suppressed IL-17 expression, and enhanced Foxp3 expression in vaginal tissues. SBCT is a promising therapeutic approach for treating BV, as it effectively modulates the immune response and restores vaginal microbiota diversity in a mouse model of G. vaginalis-induced BV.

Keywords: Bacterial vaginosis; Gardnerella vaginalis; Immune response; Inflammation; Synthetic bacterial consortia transplantation; Vaginal microbiota transplantation.

Fig. 1

Longitudinal assessment of G. vaginalis burden in vaginal lavage fluids. Bacterial load was quantified on days 4, 6, 8, 10 and 21 post-inoculation. Data are presented as mean ± standard error of the mean from three independent experiments. Number of mice in each group = 6 (total animals: n = 12).

Fig. 2

Histopathological analysis of H&E stained vaginal tissues in a mouse model of G. vaginalis-induced vaginitis. (a) CON, normal control mice; (b) GVI, G. vaginalis-infected mice; (c) SBCT, mice treated with synthetic bacterial consortia; (d) VMT, mice treated with vaginal microbiota transplantation. Images were captured using a Pannoramic MIDI digital section scanner at 100 × magnification; Scale bar: 1 μm; Number of mice in each group = 6 (total animals: n = 24).

Fig. 3

Serum levels of inflammatory cytokines in different experimental groups. (a) IL-1β, interleukin-1β; (b) IL-8, interleukin-8; (c) IL-10, interleukin-10. CON, normal control mice; GVI, G. vaginalis-infected mice; SBCT, mice treated with synthetic bacterial consortia; VMT, mice treated with vaginal microbiota transplantation. Data are presented as mean ± standard error of the mean from three independent experiments. Number of mice in each group = 6 (total animals: n = 24). ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001 vs. GVI group.

Fig. 4

Relative gene expression of pro-inflammatory biomarkers in vaginal tissues. (a) TNF-α, tumor necrosis factor-α; (b) iNOS, inducible nitric oxide synthase; (c) COX-2, cyclooxygenase 2. CON, normal control mice; GVI, G. vaginalis-infected mice; SBCT, mice treated with synthetic bacterial consortia; VMT, mice treated with vaginal microbiota transplantation. Data are presented as mean ± standard error of the mean from three independent experiments. Number of mice in each group = 6 (total animals: n = 24). ^#P < 0.05 vs. normal control group; ∗P < 0.05 vs. GVI group.

Fig. 5

Relative gene expression of helper T cell transcription factors in vaginal tissues. (a) IL-17, interleukin-17; (b) FOXP3, Forkhead Box Protein P3. CON, normal control mice; GVI, G. vaginalis-infected mice; SBCT, mice treated with synthetic bacterial consortia; VMT, mice treated with vaginal microbiota transplantation. Data are presented as mean ± standard error of the mean from three independent experiments. Number of mice in each group = 6 (total animals: n = 24). ^#P < 0.05 vs. normal control group; ∗P < 0.05 vs. GVI group.

Fig. 6

Assessment of vaginal microbiota diversity in mice with vaginal dysbiosis using high-throughput sequencing. (a) Scalar Venn representation of shared and unique OTUs among the experimental groups; (b) Chao1 index; (c) Shannon index. CON, normal control mice; GVI, G. vaginalis-infected mice; SBCT, mice treated with synthetic bacterial consortia; VMT, mice treated with vaginal microbiota transplantation. Data are presented as mean ± standard error of the mean from three independent experiments. Statistical analyses were performed using one-way ANOVA for normally distributed data and the Kruskal-Wallis test followed by Dunn's multiple comparison tests for non-normally distributed data. Number of mice in each group = 6 (total animals: n = 24). Statistical significance was determined using one-way ANOVA for normally distributed data and the Kruskal-Wallis test with Dunn's multiple comparison tests for non-normally distributed data, with results presented as mean ± standard error of the mean from three independent experiments, where ∗P < 0.05 and ∗∗P < 0.01 denote significant differences.