A171 intestinal interferon-lambda receptor 1 expression and responses are significantly decreased in pediatric inflammatory bowel disease patients

Abstract Background While interferon-lambdas (IFN-λs) were initially discovered for their role in antiviral immunity at mucosal barriers such as the lung and gut, there are many unanswered questions for how IFN-λs uniquely dampen inflammatory immune responses. In mouse colitis models, IFN-λs were shown to play a significant role in promoting epithelial barrier integrity and mucosal healing. Microbes present in the gut naturally induce IFN-λs, but how chronic inflammation, such as in patients with inflammatory bowel diseases (IBD), affects IFN-λ biology has not been well studied, especially in humans. Purpose Here, we tested the hypothesis that children with active, more severe IBD would present with lower intestinal IFN-λR levels and IFN-λ responses which could contribute to IBD pathology through exacerbated inflammation, decreased mucosal healing and impaired barrier function. Method We screened 14 novel antibodies to find the optimal clone that accurately stains the unique IFN-λ receptor subunit (IFN-λR1) protein in human intestinal tissue and IFN-λR1 levels were quantified by immunohistochemistry and flow cytometry in biopsy samples from children without IBD, Crohn’s disease, or ulcerative colitis (n=35 total). Fresh patient biopsies (ascending colon or terminal ileum) were also treated in media +/- IFN-λ for 24hrs using our novel ex vivo biopsy assay and changes in gene expression were quantified by RT-qPCR. Intestinal washes were also collected and microbes profiled by shotgun metagenomics. Result(s) We identified 2 new antibodies that accurately stained human cell lines and immune cells known to express IFN-λR1 protein (gut epithelial cells and B cells). We found that IFN-λ receptor (IFN-λR) levels are significantly reduced in gut epithelial and immune cells within pediatric IBD intestinal tissue, even at non-inflamed sites (p<0.01, 30-50% reduction) and this was even more pronounced when comparing moderate/severe disease compared to children with no disease activity. This led to lower IFN-λ responsiveness in IBD compared to non-IBD biopsies when investigating IFN-stimulated gene expression (p<0.05, up to 7-fold reduction). Paired patient gut microbe analyses identified specific species that correlated with changes in IFN-λ receptor expression. Conclusion(s) Together, our findings demonstrate pediatric IBD patients may be less able to induce critical IFN-λ-mediated antimicrobial responses and protective anti-inflammatory pathways. This work supports the goal to restore and promote IFN-λ responses as a novel therapeutic strategy for pediatric IBD. Please acknowledge all funding agencies by checking the applicable boxes below Other Please indicate your source of funding; Children's Hospital Research Institute of Manitoba Disclosure of Interest None Declared