Background and Aims: A cohort of patients with inflammatory bowel disease (IBD) exhibit expansion of the gut pathobiont, adherent invasive E. coli (AIEC). Loss of activity of the IBD susceptibility gene, protein tyrosine phosphatase type 2 (PTPN2), results in dysbiosis of the gut microbiota both in human subjects and mice. Further, constitutive Ptpn2 knock-out (Ptpn2–KO) mice display expansion of AIEC compared to wildtype littermates. CEACAM6, a host cell surface glycoprotein, is exploited by AIEC to attach to and enter intestinal epithelial cells (IECs). Here, we investigate the role of IEC-specific PTPN2 in restricting AIEC invasion. Methods: Biopsies from IBD patients heterozygous (CT) or homozygous (CC) for the PTPN2 SNP (single nucleotide polymorphism) rs1893217 were processed for immunohistochemistry. HT29 intestinal epithelial cells (IEC) were transfected with control shRNA (PTPN2–CTL), or a shRNA targeted towards PTPN2 (PTPN2–KD). The rs1893217 SNP was inserted (PTPN2–KI), or a complete knock-out of PTPN2 (PTPN2–KO) was generated, with CRISPR-Cas9 gene editing of Caco-2BBe IEC lines. Adherence and invasion assays were performed with either the human IBD AIEC isolate, LF82, or a novel fluorescent-tagged mouse adherent invasive E. coli (mAIECred) at multiplicity of infection (MOI) of 10. IL–6 and the pan–JAK inhibitor tofacitinib were administered to interrogate JAK–STAT signaling. Protein expression was determined by western blotting and densitometry. Results: CEACAM6 expression was elevated (colon and ileum) in IBD patients carrying the PTPN2 rs1893217 SNP (CT, CC) compared to wildtype (TT) IBD patients. HT29 and Caco-2BBe cell lines deficient in PTPN2 expressed significantly higher levels of CEACAM6. Further, PTPN2–KI and PTPN2–KO cell lines also displayed greater adherence and invasion by AIEC LF82 and higher mAIECred invasion. CEACAM6 expression was further elevated after administration of IL–6 in PTPN2–deficient cell lines compared to untreated controls. Silencing of STAT1 and 3 partially reduced CEACAM6 protein expression. Tofacitinib significantly reduced the elevated CEACAM6 protein expression and the higher AIEC adherence and invasion in PTPN2–KI and PTPN2–KO cell lines compared to DMSO controls. Conclusion: Our findings highlight a crucial role for PTPN2 in restricting pathobiont entry into host cells. Our study also describes a role for the FDA-approved drug, tofacitinib (Xeljanz) in correcting the JAK–STAT–mediated overexpression of CEACAM6, used by pathobionts as an entry portal into host cells. These findings suggest a role for JAK-inhibitors in mitigating AIEC colonization in IBD susceptible hosts.

DF McCole has received research support from Pfizer Inc. DPB McGovern has received consulting fees from Takeda, Prometheus Biosciences Inc, Prometheus Labs.

This work was supported by the Crohns and Colitis Foundation - Senior Research Award (D.F.M.). NIH-2R01-DK091281; 1R01AI153314-01; R21AI152017 and R01AI165490 (D.F.M.). NIH P30 DK120515 (L.E.). American Gastroenterological Association IBD Research Award (D.F.M.)

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The IRB of Cedars-Sinai Medical Center gave ethical approval for collection of human intestinal tissues.

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