Effect of Wild-Type Shigella Species and Attenuated Shigella Vaccine Candidates on Small Intestinal Barrier Function, Antigen Trafficking, and Cytokine Release

Abstract

Bacterial dysentery due to Shigella species is a major cause of morbidity and mortality worldwide. The pathogenesis of Shigella is based on the bacteria's ability to invade and replicate within the colonic epithelium, resulting in severe intestinal inflammatory response and epithelial destruction. Although the mechanisms of pathogenesis of Shigella in the colon have been extensively studied, little is known on the effect of wild-type Shigella on the small intestine and the role of the host response in the development of the disease. Moreover, to the best of our knowledge no studies have described the effects of apically administered Shigella flexneri 2a and S. dysenteriae 1 vaccine strains on human small intestinal enterocytes. The aim of this study was to assess the coordinated functional and immunological human epithelial responses evoked by strains of Shigella and candidate vaccines on small intestinal enterocytes. To model the interactions of Shigella with the intestinal mucosa, we apically exposed monolayers of human intestinal Caco2 cells to increasing bacterial inocula. We monitored changes in paracellular permeability, examined the organization of tight-junctions and the pro-inflammatory response of epithelial cells. Shigella infection of Caco2 monolayers caused severe mucosal damage, apparent as a drastic increase in paracellular permeability and disruption of tight junctions at the cell-cell boundary. Secretion of pro-inflammatory IL-8 was independent of epithelial barrier dysfunction. Shigella vaccine strains elicited a pro-inflammatory response without affecting the intestinal barrier integrity. Our data show that wild-type Shigella infection causes a severe alteration of the barrier function of a small intestinal cell monolayer (a proxy for mucosa) and might contribute (along with enterotoxins) to the induction of watery diarrhea. Diarrhea may be a mechanism by which the host attempts to eliminate harmful bacteria and transport them from the small to the large intestine where they invade colonocytes inducing a strong inflammatory response.

Reconstituted Human Polyclonal Plasma-derived Secretory-like IgM and IgA Maintain the Barrier Function of Epithelial Cells Infected with an Enteropathogen

“…Although one has to acknowledge that the Caco-2 cell line may not recapitulate all functions of normal intestinal epithelial cells, their pattern of cytokines following exposure to S. flexneri was consistent with that of other cell lines and that found in vivo (41,42). The availability of polyreactive IgA and IgM Abs with well characterized biochemical properties (29) allowed us to directly address their modes of action in the absence of any other cellular and molecular partners involved in clearance of S. flexneri, therefore allowing a comparison of their respective functional characteristics.…”

Cryptosporidium parvumdisrupts intestinal epithelial barrier function via altering expression of key tight junction and adherens junction proteins

“…It appears from various studies that occludin could be a regulator of TJs, rather than an essential component, an interpretation that could explain the absence of intestinal barrier defects in unstressed occludin-deficient mice (France & Turner, 2017). Previous studies have also reported that levels of high-and low-MW occludin differing in phosphorylation levels could change in response to infection by enteric pathogens (Beau, Cotte-Laffitte, Amsellem, & Servin, 2007;Fiorentino, Levine, Sztein, & Fasano, 2014). However, the levels of high-MW form of the occludin in the detergent-insoluble fraction representing hyperphosphorylated occludin appeared to be unaltered in response to CP infection.…”

“…4.11 | Immunoblotting of occludin in Triton X-100 soluble and insoluble fractions Triton X-100 soluble and insoluble fractions were prepared as described previously (Fiorentino et al, 2014). Briefly, monolayers were harvested on ice in lysis buffer (1% Triton X-100, 100 mM NaCl, 10 mM HEPES, 2 mM EDTA, 4 mM Na 3 VO 4 , 40 mM NaF and a protease inhibitor cocktail [Complete Mini, Roche Molecular Biochemicals, Mannheim, Germany] and phosphatase inhibitors [Sigma]).…”

Toxoplasma gondiiInfection Promotes Epithelial Barrier Dysfunction of Caco-2 Cells

“…In accordance, Salmonella typhi and Shigella infections lead to claudin-1, ZO-1 and occludin redistribution, occludin phosphorylation and disengagement from the TJ complex. 38,39 Also, Yersinia enterocolitica induces epithelial barrier dysfunction through regional TJ changes. 40 These findings suggest that TJ proteins are frequent targets of intestinal pathogens in the process of invasion and infection.…”