title: Modulation of pathogen-induced CCL20 secretion from HT-29 human intestinal epithelial cells by commensal bacteria.
abstract: BACKGROUND
  Human intestinal epithelial cells (IECs) secrete the chemokine CCL20 in response to infection by various enteropathogenic bacteria or exposure to bacterial flagellin. CCL20 recruits immature dendritic cells and lymphocytes to target sites. Here we investigated IEC responses to various pathogenic and commensal bacteria as well as the modulatory effects of commensal bacteria on pathogen-induced CCL20 secretion. HT-29 human IECs were incubated with commensal bacteria (Bifidobacterium infantis or Lactobacillus salivarius), or with Salmonella typhimurium, its flagellin, Clostridium difficile, Mycobacterium paratuberculosis, or Mycobacterium smegmatis for varying times. In some studies, HT-29 cells were pre-treated with a commensal strain for 2 hr prior to infection or flagellin stimulation. CCL20 and interleukin (IL)-8 secretion and nuclear factor (NF)-kappaB activation were measured using enzyme-linked immunosorbent assays.
  
  
  RESULTS
  Compared to untreated cells, S. typhimurium, C. difficile, M. paratuberculosis, and flagellin activated NF-kappaB and stimulated significant secretion of CCL20 and IL-8 by HT-29 cells. Conversely, B. infantis, L. salivarius or M. smegmatis did not activate NF-kappaB or augment CCL20 or IL-8 production. Treatment with B. infantis, but not L. salivarius, dose-dependently inhibited the baseline secretion of CCL20. In cells pre-treated with B. infantis, C. difficile-, S. typhimurium-, and flagellin-induced CCL20 were significantly attenuated. B. infantis did not limit M. Paratuberculosis-induced CCL20 secretion.
  
  
  CONCLUSIONS
  This study is the first to demonstrate that a commensal strain can attenuate CCL20 secretion in HT-29 IECs. Collectively, the data indicate that M. paratuberculosis may mediate mucosal damage and that B. infantis can exert immunomodulatory effects on IECs that mediate host responses to flagellin and flagellated enteric pathogens.
authors.affiliation: Alimentary Pharmabiotic Centre, University College Cork, National University of Ireland, Cork, Ireland. shomiksibartie@gmail.com
authors.forename: Shomik
authors.initials: S
authors.lastname: Sibartie
authors.forename: Ann M
authors.initials: AM
authors.lastname: O'Hara
authors.forename: Jude
authors.initials: J
authors.lastname: Ryan
authors.forename: Aine
authors.initials: A
authors.lastname: Fanning
authors.forename: Jim
authors.initials: J
authors.lastname: O'Mahony
authors.forename: Shaun
authors.initials: S
authors.lastname: O'Neill
authors.forename: Barbara
authors.initials: B
authors.lastname: Sheil
authors.forename: Liam
authors.initials: L
authors.lastname: O'Mahony
authors.forename: Fergus
authors.initials: F
authors.lastname: Shanahan
mesh_terms: D001419:Bacteria / Q000276:immunology*; D001424:Bacterial Infections / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D054418:Chemokine CCL20 / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005408:Flagellin / Q000276:immunology / Q000378:metabolism; D005786:Gene Expression Regulation; D019073:HT29 Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D018928:Immunity, Mucosal; D056747:Immunomodulation; D016209:Interleukin-8 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D054418:Chemokine CCL20; D016209:Interleukin-8; D016328:NF-kappa B; D005408:Flagellin