311 - Group B Streptococcus β-hemolysin/cytolysin Modulates Intestinal Tight Junction Protein Gene Expression

Poster Number: 311
Publication Number: 311.124

Kristen Dominguez, University of South Florida, tampa, FL, United States; April K. Lindon, University of South Florida, Tarpon Springs, FL, United States; Sophie E. Darch, University of South Florida, Tampa, FL, United States; Tara M. Randis, University of South Florida, Tampa, FL, United States

Background: Group B Streptococcus (GBS) is a leading cause infant sepsis worldwide. Colonization of the gastrointestinal tract is a critical precursor to late-onset infection in exposed newborns. Neonatal susceptibility to GBS intestinal translocation stems from intestinal immaturity (e.g., differentially expressed tight junction proteins (TJP)) but, the mechanisms by which GBS exploits the immature host remain unclear. β-hemolysin/cytolysin (βH/C) is a highly conserved, pore-forming toxin produced by GBS capable of disrupting extraintestinal epithelial barriers, with unknown roles in intestinal colonization and translocation.

Objective: In this study, our aim was to determine the contribution of βH/C to the establishment of GBS intestinal colonization and its effects on TJP expression.

Design/Methods: We used our established mouse model of sustained GBS colonization to compare TJP expression in intestinal tissues. Animals were gavaged with GBS wild type strain COH-1 (WT, n=7), its isogenic, βH/C-deficient mutant (ΔβH/C, n=4), or PBS (sham, n=4). Intestinal tissues were harvested at 96 hours post-exposure and processed for determination of bacterial burden and RNA isolation. We used RT-qPCR to compare candidate TJP (Marveld2, Cldn2, Tjp-1) gene expression (ΔΔ-CT method, normalized to β-actin) in the proximal colon and distal small intestine.

Results: GBS ΔβH/C did not exhibit a colonization defect as determined by CFU/cm tissue (Table 1). Marveld2 gene expression was significantly increased in the intestinal tissues of pups colonized with WT GBS as compared to GBS ΔβH/C or sham. Cldn2 gene expression was significantly increased in colonic samples of pups colonized with WT GBS as compared to GBS ΔβH/C or sham. There were no significant differences in Tjp-1 expression among study groups (Figure 1).Conclusion(s): GBS induced changes in Cldn2 and Marveld2 gene expression in intestinal tissues are dependent on the expression of βH/C toxin. Our results demonstrate an important role of βH/C in modulating intestinal epithelial protein expression that may contribute to overall barrier disruption and GBS translocation.
KDominguez CVKDominguez CV .pdf
Figure 1. Intestinal tight junction gene expression.Relative gene expression of Tjp-1, Cldn2, and Marveld2 normalized to β-actin in the distal small intestine and proximal colon. [ΔΔ-CT method, normalized to β-actin; One-way ANOVA with Šídák's multiple comparison test. * p < 0.05, ** p < 0.005]