Group B streptococcus exploits vaginal epithelial exfoliation for ascending infection
Jay Vornhagen, … , Elizabeth Nance, Lakshmi Rajagopal
Jay Vornhagen, … , Elizabeth Nance, Lakshmi Rajagopal
Published April 9, 2018
Citation Information: J Clin Invest. 2018;128(5):1985-1999. https://doi.org/10.1172/JCI97043.
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Research Article Infectious disease Reproductive biology

Group B streptococcus exploits vaginal epithelial exfoliation for ascending infection

Abstract

Thirteen percent of pregnancies result in preterm birth or stillbirth, accounting for fifteen million preterm births and three and a half million deaths annually. A significant cause of these adverse pregnancy outcomes is in utero infection by vaginal microorganisms. To establish an in utero infection, vaginal microbes enter the uterus by ascending infection; however, the mechanisms by which this occurs are unknown. Using both in vitro and murine models of vaginal colonization and ascending infection, we demonstrate how a vaginal microbe, group B streptococcus (GBS), which is frequently associated with adverse pregnancy outcomes, uses vaginal exfoliation for ascending infection. GBS induces vaginal epithelial exfoliation by activation of integrin and β-catenin signaling. However, exfoliation did not diminish GBS vaginal colonization as reported for other vaginal microbes. Rather, vaginal exfoliation increased bacterial dissemination and ascending GBS infection, and abrogation of exfoliation reduced ascending infection and improved pregnancy outcomes. Thus, for some vaginal bacteria, exfoliation promotes ascending infection rather than preventing colonization. Our study provides insight into mechanisms of ascending infection by vaginal microbes.

Authors

Jay Vornhagen, Blair Armistead, Verónica Santana-Ufret, Claire Gendrin, Sean Merillat, Michelle Coleman, Phoenicia Quach, Erica Boldenow, Varchita Alishetti, Christina Leonhard-Melief, Lisa Y. Ngo, Christopher Whidbey, Kelly S. Doran, Chad Curtis, Kristina M. Adams Waldorf, Elizabeth Nance, Lakshmi Rajagopal

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Figure 4

GBS induces β-catenin signaling.

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GBS induces β-catenin signaling. (A) Expression of β-catenin target gene...
(A) Expression of β-catenin target genes in GBS-infected hVECs compared with expression in mock-treated controls 24 hours after infection (n = 3; **P < 0.005 and ****P < 0.00005, by 1-way ANOVA followed by Sidak’s multiple comparisons test; data represent the mean ± SEM). (B) Localization of β-catenin (white) in GBS-infected hVECs compared with mock-treated controls 24 hours after infection (nuclei are stained with DAPI [blue]; overlap is shown in yellow). Images are from 1 of 3 experiments. Original magnification, ×100. (C) Expression of β-catenin target genes in murine vaginal tissues 96 hours after vaginal inoculation with WT GBS compared with expression in control PBS–treated tissues (n = 4/group; *P < 0.05, ***P < 0.0005, ****P < 0.00005, and P = 0.1, by 1-way ANOVA followed by Sidak’s multiple comparisons test; data represent the mean ± SEM). (D) c-Myc immunostaining in murine vaginal tracts 96 hours after vaginal inoculation with PBS or WT GBS. Images are from 1 of 3 experiments. Scale bars: 100 μm. (E) Quantification of c-Myc immunostaining in murine vaginal tracts 96 hours after vaginal inoculation with WT GBS or control PBS (6 mice/group; *P < 0.05, by 2-sided, unpaired t test; data represent the mean). (F) Western blot (WB) for p-GSK3β in GBS-infected hVECs compared with mock-treated controls, 0 and 4 hours after infection. GAPDH was used as a loading control. Blots are from 1 of 4 experiments. (G) Quantification of p-GSK3β band intensity. The band intensity was first normalized to GAPDH and then to t0 of the corresponding treatment (n = 4/group; *P < 0.05, **P < 0.005, and P = 0.98, by 1-way ANOVA followed by Sidak’s multiple comparisons test; data represent the mean ± SEM). (H) hVECs were left untreated or were treated for 16 or 24 hours with the β-catenin signaling inhibitor FH535 (15 μM) prior to WT GBS infection, and cell detachment was measured. Data were normalized to the uninfected controls (n = 3; *P < 0.05 and ***P < 0.0005, by ANOVA followed by Sidak’s multiple comparisons test; data represent the mean ± SEM). (I and J) Flow cytometric analysis of surface E-cadherin (I) and N-cadherin (J) on mock-treated or WT GBS–infected hVECs, with or without FH535 pretreatment (n = 3; *P < 0.05, **P < 0.005, and P = 0.06; data represent the mean ± SEM by ANOVA followed by Sidak’s multiple comparisons test.