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* = Presenting author

OP001 Transmissive Crohn's disease-like ileitis is caused by functional dysbiosis in the intestinal microbiota independent of inflammation-driven Paneth cell failure

M. Schaubeck*1, T. Clavel2, I. Lagkouvardos1, J. Calasan1, S.B. Haange3, N. Jehmlich3, M. von Bergen4, M. Basic5, A. Bleich6, D. Haller2

Table 1. 

Proportion of patients with mucosal healing (MH — Mayo 0 or 1) by treatment group, visit, and extent of evaluation. n= No. of patients with mucosal healing; N= total no. of patients with evaluable videos. P values: vs placebo.






1Technische Universität München, Chair of Nutrition and Immunology, Weihenstephan, Germany, 2Technische Universität München, Chair of Nutrition and Immunology, Freising-Weihenstephan, Germany, 3Helmholtz-Centre for Environmental Research, UFZ, Department of Proteomics, Leipzig, Germany, 4University of Aalborg, Department of Biotechnology, Aalborg, Denmark, 5Hannover Medical School, Institute for Laboratory AnimHannover Medical School, Hannover, Germany, 6Hannover Medical School, Institute for Laboratory AnimHannover Medical School, Hannover, Germany

Background

Dysbiosis of the intestinal microbiota is associated with Crohn´s disease (CD). Functional evidence for a causal role of bacteria in the development of small intestinal inflammation is still lacking. Similar to human pathology, TNFdeltaARE/+ (ARE) mice develop a CD-like transmural inflammation with predominant ileal involvement.

Methods

Mice (C57BL6/N-heterozygous ARE and respective WT littermates) were housed under conventional (CONV), specific-pathogen-free (SPF) or germfree (GF) conditions. CONV-ARE mice were treated with vancomycin and metronidazole and disease activity was monitored at the age of 12 to 18 weeks. GF mice were colonized with Escherichia coli LF82 or caecal content from ARE mice. Pathology was assessed by microscopic evaluation of ileal and colonic tissue sections. Granulocyte infiltration and Paneth cell function was quantified by immunofluorescence analysis. Microbial communities were analyzed by high-throughput 16S rRNA gene sequencing (V3/V4 regions). Metaproteomes were measured using LC-MS analysis.

Results

GF-ARE mice were completely free of intestinal inflammation and antibiotic treatment of CONV-ARE mice induced remission of ileitis but not colitis, demonstrating that disease severity and location are microbiota dependent. SPF-ARE mice were free of colitis but developed three different ileitis phenotypes associated with changes in histopathology, granulocyte infiltration, TNF and IL-17 expression and loss of Paneth cell function. 16S rRNA gene sequencing and metaproteomic analysis identified compositional and functional divergence of gut bacterial communities according to the three disease phenotypes. Members of the Clostridiales and specific bacterial enzymes involved in nucleotide and carbohydrate metabolism were associated with inflammation. Transfer of microbiota from SPF-ARE into GF-ARE recipient mice caused CD-like inflammation only with dysbiotic communities from inflamed SPF donors, while recipients of non-inflamed ARE microbiota showed no signs of intestinal inflammation. Loss of Paneth cell function was associated with aberrant lysozyme and UEA-1 expression pattern in the crypt base showing a concomitant but not preceding failure of Paneth cell function in the development of inflammation-driven ileal pathology. Monoassociation with CD-associated E. coli strain LF 82 did not induce inflammation, suggesting that complex bacterial communities are required for disease initiation.

Conclusion

The transfer of a functionally dysbiotic microbiota from inflamed ARE mice induced ileal inflammation in GF mice independent of disease preceding Paneth cell failure, supporting a causal role of bacteria for the development of CD-like pathologies in the susceptible host.