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P019. T cell specific loss of PTPN2 results in aggravated colitis and pronounced intestinal dysbiosis as observed in Crohn's disease patients

M. Spalinger1, C. Chassard2, S. Kasper1, L. Biedermann1, S. Vavricka3, I. Frey-Wagner1, K. Atrott1, C. Lacroix2, M. Fried1,4, G. Rogler1,4, M. Scharl1,4, 1University Hospital Zurich, Gastroenterology & Hepatology, Zurich, Switzerland, 2ETH Zurich, Institute of Food, Nutrition and Health, Zurich, Switzerland, 3Hospital Triemli, Gastroenterology & Hepatology, Zurich, Switzerland, 4Zurich Institute for Human Physiology, University Zürich, Zürich, Switzerland

Background

Presence of a genetic loss-of-function variant within the gene locus encoding protein-tyrosine phosphatase non-receptor type 2 (PTPN2) results in increased risk for Crohn's disease (CD). In CD, deregulated immune responses with enhanced levels of T helper (Th)1 and Th17 cells are observed. Th cells are crucially involved in shaping the host response towards the intestinal microbiota, and CD correlates with changes in the composition of the gut microbiota. Here we address the role of PTPN2 in Th cell differentiation during intestinal inflammation and the resulting effects on the intestinal microbiota.

Methods

Mice lacking PTPN2 in T cells (PTPN2deltaT mice) and control littermates were treated with DSS to induce acute or chronic colitis. Th cell subsets and cytokine expression/secretion were analyzed by FACS, RT-PCR and ELISA; intestinal microbiota was analyzed by pyrosequencing. Patient samples were analyzed for Th associated transcription factors (TF) and cytokines by RT-PCR and ELISA.

Results

Upon 7 d DSS treatment, PTPN2deltaT mice suffered from aggravated colitis, as characterized by enhanced weight loss, increased endoscopic and microscopic colitis scores, pronounced shortening of the colon and enhanced MPO levels. In the intestine, proportions of Th1 and Th17 cells and associated TF/cytokines (TBX21/IFNgamma and RORC/IL-17, respectively) were enhanced while Th2 and regulatory T (Treg) cells were reduced in PTPN2deltaT mice. Similar results were observed in chronic DSS induced colitis. In CD patients featuring the CD-associated PTPN2 loss-of function variant, we also observed enhanced expression/secretion of T-bet/IFNgamma and RORC/IL-17 in the intestine and serum, while IL-10 and IL-13 levels were reduced when compared to samples from PTPN2 wild-type patients. In mice, both, acute and chronic DSS treatment resulted in intestinal dysbiosis with an increase of Bacteriodetes and Proteobacteria with concomitant decrease in Firmicutes abundance. Of interest, in PTPN2deltaT mice, levels of Bacteriodetes and Proteobacteria were already enhanced even without DSS challenge and these effects were maximal in DSS treated PTPN2deltaT mice. The decrease in Firmicutes was mainly due to a pronounced reduction in butyrate producing Coprococcus.

Conclusion

Our data demonstrate that T cell specific loss of PTPN2 results in profound changes in the Th cell compartment with an increase in pro-inflammatory Th1 and Th17 cells/cytokines and a reduction in regulatory mechanisms. In addition to increased intestinal inflammation, this also results in pronounced intestinal dysbiosis, which is very similar to the changes in the intestinal microbiota observed in IBD patients.