title: AIEC pathobiont instigates chronic colitis in susceptible hosts by altering microbiota composition.
abstract: BACKGROUND
  Inflammatory bowel disease (IBD) is driven by a seemingly aberrant immune response to the gut microbiota with disease development dictated by genetics and environmental factors. A model exemplifying this notion is our recent demonstration that colonisation of adherent-invasive Escherichia coli (AIEC) during microbiota acquisition drove chronic colitis in mice lacking the flagellin receptor TLR5 (T5KO). T5KO colitis persisted beyond AIEC clearance and requires TLR4 and the NLRC4 inflammasome. We hypothesised that AIEC instigates chronic inflammation by increasing microbial lipopolysaccharide (LPS) and flagellin levels.
  
  
  OBJECTIVE
  Examine if transient AIEC colonisation lastingly alters levels of LPS and flagellin and changes microbiota composition.
  
  
  METHODS
  Germ-free mice (wild type (WT) and T5KO) were inoculated with AIEC strain LF82 and placed in standard housing allowing a complex microbiota that eliminated AIEC in both mice strains. Faeces were assayed for the inflammatory marker, lipocalin-2, bacterial loads, and microbiota composition by pyrosequencing. Faecal LPS and flagellin bioactivity were measured via a cell-based reporter assay.
  
  
  RESULTS
  Transient AIEC colonisation, in WT mice, did not alter inflammatory markers, bacterial loads, microbiota composition, nor its pro-inflammatory potential. By contrast, transient AIEC colonisation of T5KO mice drove chronic inflammation which correlated with microbiota components having higher levels of bioactive LPS and flagellin. Such AIEC-induced elevation of LPS and flagellin persisted well beyond AIEC clearance, required AIEC be flagellated, and was associated with alteration in microbiota species composition including a loss of species diversity.
  
  
  CONCLUSIONS
  AIEC, and perhaps other pathobionts, may instigate chronic inflammation in susceptible hosts by altering the gut microbiota composition so as to give it an inherently greater ability to activate innate immunity/pro-inflammatory gene expression.
authors.affiliation: Department of Biology, Center for Inflammation, Immunity, and Infection, Georgia State University, Atlanta, Georgia, USA.
authors.forename: Benoit
authors.initials: B
authors.lastname: Chassaing
authors.affiliation: Department of Microbiology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA.
authors.forename: Omry
authors.initials: O
authors.lastname: Koren
authors.affiliation: Department of Pharmacology, Inserm, U1107, NEURO-DOL, Université d'Auvergne, Clermont-Ferrand, France.
authors.forename: Frederic A
authors.initials: FA
authors.lastname: Carvalho
authors.affiliation: Department of Microbiology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Ley
authors.affiliation: Department of Biology, Center for Inflammation, Immunity, and Infection, Georgia State University, Atlanta, Georgia, USA.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Gewirtz
mesh_terms: D000209:Acute-Phase Proteins / Q000378:metabolism; D000818:Animals; D001422:Bacterial Adhesion / Q000276:immunology; D058491:Bacterial Load; D015415:Biomarkers / Q000378:metabolism; D002908:Chronic Disease; D003092:Colitis / Q000276:immunology / Q000382:microbiology*; D003106:Colon / Q000382:microbiology*; D004269:DNA, Bacterial / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology; D004927:Escherichia coli Infections / Q000150:complications* / Q000276:immunology; D005243:Feces / Q000737:chemistry / Q000382:microbiology; D005408:Flagellin / Q000378:metabolism; D005856:Germ-Free Life; D007113:Immunity, Innate; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology*; D000071068:Lipocalin-2; D054834:Lipocalins / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D064307:Microbiota; D015513:Oncogene Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D051198:Toll-Like Receptor 5 / Q000172:deficiency*
chemical_list: D000209:Acute-Phase Proteins; D015415:Biomarkers; D004269:DNA, Bacterial; D000071068:Lipocalin-2; D054834:Lipocalins; D008070:Lipopolysaccharides; D015513:Oncogene Proteins; D051198:Toll-Like Receptor 5; C071332:Lcn2 protein, mouse; D005408:Flagellin
keywords: COLONIC MICROFLORA; CROHN'S DISEASE; INFLAMMATORY BOWEL DISEASE
references.citation: Helicobacter. 2005 Jun;10(3):223-30
references.pmid: 15904480
references.citation: Infect Immun. 1998 Nov;66(11):5157-66
references.pmid: 9784517
references.citation: J Exp Med. 2009 Sep 28;206(10):2179-89
references.pmid: 19737864
references.citation: Gastroenterology. 2011 May;140(6):1720-28
references.pmid: 21530738
references.citation: Gastroenterology. 2002 Jan;122(1):44-54
references.pmid: 11781279
references.citation: Mol Microbiol. 2003 May;48(3):781-94
references.pmid: 12694621
references.citation: Annu Rev Immunol. 2010;28:573-621
references.pmid: 20192811
references.citation: Infect Immun. 1999 Sep;67(9):4499-509
references.pmid: 10456892
references.citation: Gastroenterology. 2004 Aug;127(2):412-21
references.pmid: 15300573
references.citation: Nat Methods. 2010 May;7(5):335-6
references.pmid: 20383131
references.citation: Pediatrics. 2012 Oct;130(4):e794-803
references.pmid: 23008454
references.citation: Gut. 2004 May;53(5):685-93
references.pmid: 15082587
references.citation: PLoS One. 2012;7(9):e44328
references.pmid: 22957064
references.citation: Science. 2010 Apr 9;328(5975):228-31
references.pmid: 20203013
references.citation: Nat Rev Gastroenterol Hepatol. 2011 Aug 16;8(9):523-31
references.pmid: 21844910
references.citation: J Clin Invest. 2007 Jun;117(6):1566-74
references.pmid: 17525800
references.citation: Nature. 2007 Mar 29;446(7135):557-61
references.pmid: 17361131
references.citation: J Clin Invest. 2013 Feb;123(2):700-11
references.pmid: 23281400
references.citation: ISME J. 2012 Mar;6(3):610-8
references.pmid: 22134646
references.citation: Nature. 2007 Jul 26;448(7152):427-34
references.pmid: 17653185
references.citation: J Clin Invest. 2007 Dec;117(12):3909-21
references.pmid: 18008007
references.citation: Nature. 2001 May 31;411(6837):599-603
references.pmid: 11385576
references.citation: Nat Methods. 2008 Mar;5(3):235-7
references.pmid: 18264105
references.citation: Int J Med Microbiol. 2002 Sep;292(3-4):185-93
references.pmid: 12398209
references.citation: Proc Natl Acad Sci U S A. 2002 May 14;99(10):6567-72
references.pmid: 12011421
references.citation: J Clin Invest. 2004 May;113(9):1296-306
references.pmid: 15124021
references.citation: Cell Host Microbe. 2012 Aug 16;12(2):139-52
references.pmid: 22863420
references.citation: Inflamm Bowel Dis. 2007 Oct;13(10):1191-201
references.pmid: 17712838
references.citation: Nature. 2007 Jun 7;447(7145):661-78
references.pmid: 17554300
references.citation: Nat Genet. 2007 Jul;39(7):830-2
references.pmid: 17554261
references.citation: Appl Environ Microbiol. 2005 Dec;71(12):8228-35
references.pmid: 16332807
references.citation: Science. 2006 Dec 1;314(5804):1461-3
references.pmid: 17068223
references.citation: Gastroenterology. 2004 Jul;127(1):80-93
references.pmid: 15236175
references.citation: Gut. 2012 Mar;61(3):373-84
references.pmid: 21646247
references.citation: Proc Natl Acad Sci U S A. 2011 Mar 15;108 Suppl 1:4592-8
references.pmid: 20937873
references.citation: Infect Immun. 2010 Feb;78(2):639-50
references.pmid: 19933833
references.citation: Mol Biol Evol. 2009 Jul;26(7):1641-50
references.pmid: 19377059