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. https://doi.org/10.1172/JCI97043.
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Categories: 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 1

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

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GBS stimulates exfoliation and disrupts vaginal epithelial cell barrier ...
(A) hVECs were infected with WT GBS for 0, 16, or 24 hours and stained with 10% crystal violet for 30 minutes. Loosely adherent cells were removed by centrifugation, and crystal violet staining intensity was measured. Data were normalized to mock-infected controls (n = 3; **P < 0.005 and P = 0.08, by ANOVA followed by Sidak’s multiple comparisons test; data represent the mean ± SEM). (B) hVECs were infected with WT GBS for 24 hours and analyzed by scanning electron microscopy. Images show hVEC detachment 24 hours after infection with control PBS (mock) or WT GBS. Scale bars: 10 μm. (C) The barrier function of hVEC monolayers was monitored in real time using ECIS. Infection with WT GBS led to a disruption in barrier function as determined by the decrease in resistance of the infected monolayers compared with the uninfected control (n = 3; data represent the mean). (D) hVECs grown on Transwells were infected with WT GBS for 24 hours or treated with 0.1% Triton X-100, which was used as a positive control. After 24 hours, fluorescein dye was added to the apical compartment of the Transwell, and migration of the dye to the basal compartment was measured after 1 hour (n = 3; ****P < 0.00005, by ANOVA followed by Sidak’s multiple comparisons test; data represent the mean ± SEM). (E) hVECs grown on Transwells were either mock infected or infected with WT GBS for 24 hours. At 0, 16, and 24 hours after infection, the basal compartment of each well was sampled and stained with SYTO9 nucleic acid to enumerate bacteria (n = 3; **P < 0.005, by ANOVA followed by Sidak’s multiple comparisons test; data represent the mean ± SEM). RFU, relative fluorescence units.