Verotoxin 2 Enhances Adherence of Enterohemorrhagic Escherichia coli O157:H7 to Intestinal Epithelial Cells and Expression of β1-Integrin by IPEC-J2 Cells

Abstract

Verotoxin (VT) has been implicated in the promotion of adherence to and colonization of intestinal epithelial cells by enterohemorrhagic Escherichia coli (EHEC) O157:H7. The present study investigated the effect of VT2 on the adherence of EHEC O157:H7 strain 86-24 to porcine jejunal (IPEC-J2), human colon (CaCo-2), and human laryngeal carcinoma (HEp-2) cell lines and on the expression in IPEC-J2 cells of synthases for ␤1-integrin and nucleolin, both of which are implicated in bacterial adherence. The effect on expression of globotriaosylceramide (Gb3) synthase, the receptor for VT, was also examined. Data were obtained by adherence assays and quantitative reverse transcriptase PCR, using EHEC O157 strain 86-24, a vt2 deletion mutant, a vt2 phage-negative strain, and complemented mutants in which the vt2 gene was restored. Compared with the adherence of the parent and complemented mutant strains, the vt2-negative strains adhered significantly less to all three types of cells. Adherence of the wild-type EHEC strain to IPEC-J2 cells was accompanied by increased expression of ␤1-integrin, nucleolin, and Gb3 synthase. IPEC-J2 cells in association with wild-type EHEC O157:H7 or the complemented mutants expressed higher levels of ␤1-integrin than did cells in association with the vt2-negative strains or with no bacteria. Expression of nucleolin was decreased by association with the vt2-negative mutant, but complementation failed to restore wild-type expression. The data indicate that VT2 plays a role in the adherence of EHEC O157:H7 to intestinal epithelial cells, possibly by increasing the expression of the host receptor ␤1-integrin.

Differential Virulence of Clinical and Bovine-Biased Enterohemorrhagic Escherichia coli O157:H7 Genotypes in Piglet and Dutch Belted Rabbit Models

“…Recent studies using in vitro cell culture and mouse models suggest that besides inducing systemic disease, Stx2 production can also promote the colonization of epithelial cells by enhancing the expression of host cell intimin receptors (40,57). In contrast to this, similar studies conducted in cattle and rabbits suggested no effect of Stx on colonization on intestine (55,61).…”

Essential Role of Invasin for Colonization and Persistence of Yersinia enterocolitica in Its Natural Reservoir Host, the Pig

“…Not much is known about expression of ␤ 1 -integrin receptors in porcine tissues. However, some evidence has shown that ␤ 1 -integrins are expressed in the porcine intestine and in isolated intestinal epithelial cells of swine (47,48). Efficient invasin-mediated engagement of ␤ 1 -integrin receptors in the intestine could inhibit spread to other host sites and enable the pathogen to remain in the intestine of the pigs for extended time periods.…”

Competition during enrichment of pathogenicEscherichia colimay result in culture bias

“…As one study demonstrates, Shiga toxins may act as a bacterial defense against Eukaryotic predators (Lainhart et al 2009). Shiga toxins have also been implicated in the promotion of adherence and colonization of O157:H7 to human intestinal epithelial cells in comparison to stx-negative strains (Liu et al 2010). However, selective advantages are more likely to operate in the bovine reservoir or external environment than in the human gastrointestinal tract as they are considered "accidental hosts," and STEC/enterohemorrhagic E. coli (EHEC) are unlikely to have evolved specifically to cause human infection (Franz et al 2014).…”