title: Role of Shiga toxin versus H7 flagellin in enterohaemorrhagic Escherichia coli signalling of human colon epithelium in vivo.
abstract: Enterohaemorrhagic Escherichia coli O157:H7 (EHEC) is a clinically important foodborne pathogen that colonizes human colon epithelium and induces acute colonic inflammation, but does not invade the epithelial cells. Whereas Shiga toxin (Stx) and bacterial flagellin have been studied for their ability to upregulate the production of proinflammatory chemokines by cultured human colon cancer cell lines, the relevance of studies in colon cancer cell lines to the production of proinflammatory signals by normal epithelial cells in EHEC-infected human colon is not known. We show herein that Stx does not bind to human colon epithelium in vivo. Moreover, globotriaosylceramide (Gb3/CD77) synthase, the enzyme required for synthesis of the Gb3/CD77 receptor for Stx, was not expressed by normal or inflamed human colon epithelium in vivo. In contrast, Toll-like receptor (TLR) 5, the receptor for bacterial flagellin, was expressed by normal human colon epithelium and by colon epithelium in human intestinal xenografts. EHEC H7 flagellin instilled in the lumen of human colon xenografts that contain an intact human epithelium upregulated the expression of epithelial cell proinflammatory chemokines, which was accompanied by a subepithelial influx of neutrophils. Isogenic mutants of EHEC that lacked flagellin did not significantly upregulate prototypic neutrophil and dendritic cell chemoattractants by model human colon epithelia, irrespective of Stx production. We conclude that EHEC H7 flagellin and not Stx is the major EHEC factor that directly upregulates proinflammatory chemokine production by human colon epithelium in vivo.
authors.affiliation: Laboratory of Mucosal Immunology, Department of Medicine, University of California at San Diego, La Jolla, CA, USA.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Miyamoto
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Iimura
authors.forename: James B
authors.initials: JB
authors.lastname: Kaper
authors.forename: Alfredo G
authors.initials: AG
authors.lastname: Torres
authors.forename: Martin F
authors.initials: MF
authors.lastname: Kagnoff
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D002460:Cell Line; D018925:Chemokines / Q000276:immunology / Q000378:metabolism; D003106:Colon / Q000378:metabolism* / Q000382:microbiology / Q000637:transplantation; D004927:Escherichia coli Infections / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000378:metabolism / Q000502:physiology*; D005408:Flagellin / Q000378:metabolism*; D005700:Galactosyltransferases / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D051379:Mice; D016513:Mice, SCID; D009504:Neutrophils / Q000276:immunology; D022621:Shiga Toxin / Q000378:metabolism*; D015398:Signal Transduction; D051198:Toll-Like Receptor 5 / Q000378:metabolism; D014183:Transplantation, Heterologous
chemical_list: D018925:Chemokines; C495346:TLR5 protein, human; D051198:Toll-Like Receptor 5; D005408:Flagellin; D022621:Shiga Toxin; D005700:Galactosyltransferases; C045097:UDP-galactose-lactosylceramide alpha 1-4-galactosyltransferase