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 2

GBS stimulates exfoliation and disrupts vaginal epithelial cell barrier function in vivo.

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GBS stimulates exfoliation and disrupts vaginal epithelial cell barrier ...
(A) Female WT C57BL6/J mice were vaginally inoculated with approximately 108 CFU of either WT GBS or an equal volume of control PBS (n = 3/group). Vaginal tissues were analyzed by scanning electron microscopy, and bacterial burden was assessed in vaginal and uterine tissues. Images show significant vaginal epithelial exfoliation 72 and 96 hours after inoculation with WT GBS and not with control saline. Scale bars: 100 μm. (B) Exfoliated vaginal epithelial cells 24, 48, 72, and 96 hours after inoculation were quantified in a blinded fashion (n = 3 images/2 tissues/group; **P < 0.005 and ****P < 0.00005, by ANOVA followed by Sidak’s multiple comparisons test; data represent the mean ± SEM). (C) High-magnification images of the vaginal epithelium show that GBS was associated with exfoliated epithelial cells. Scale bars: 10 μm; Original magnification, ×1900 (enlarged inset). Images are from 1 of at least 3 experiments. (D) Nanoparticle penetration into mouse vaginal epithelia in control saline– or WT GBS–treated animals 24 and 96 hours after vaginal inoculation, respectively. Nuclei were stained with DAPI and are shown in blue, PEGylated nanoparticles (120 nm diameter) are shown in white, and red arrows indicate intraepithelial nanoparticles. Images are from 1 of at least 2 experiments. Scale bars: 100 μm. Quantitative measurements were calculated using the equation: ([mean area of intraepithelial nanoparticle coverage]/[mean epithelial area]) × 10,000 ± SD. (E) GBS penetration into mouse vaginal epithelia in control saline– or WT GBS–treated animals 24 and 96 hours after vaginal inoculation. Nuclei were stained with DAPI and are shown in blue, GBS are shown in white, and yellow arrows indicate intraepithelial GBS. Images are from 1 of at least 4 experiments. Scale bars: 10 μm.