A10 EARLY LIFE SENSITIZATION TO GLUTEN INDUCES SUSTAINED IMMUNOPATHOLOGY IN DR3-DQ2 MICE

Abstract Background Celiac disease (CeD) is an autoimmune T-cell mediated enteropathy, triggered by gluten, a group of proteins found in wheat, barley, and rye. The defined role of gluten as a dietary trigger, necessary genes (HLA-DQ2 and/or DQ8), and tissue transglutaminase (TG2) as the autoantigen together, are unique features of CeD. Although CeD onset can occur at any age, first dietary introduction of gluten during infancy is a critical window of exposure, especially in infants homozygous for the HLA DQ2.5 allele. While adult sensitization studies have been recently performed in DR3-DQ2 mice, the consequences of early life gluten sensitization timing remain unexplored. Aims Our aim was to characterize gluten-immunopathology and CeD-specific serology in specific pathogen free (SPF) DR3-DQ2 transgenic mice sensitized to gluten, 1 week before weaning. Methods Seven-week-old SPF DR3-DQ2 transgenic mice, kept on a gluten-free diet (GFD), were paired for breeding. At post-natal day 3, pups were standardized to 4 per litter (n=2 male, n=2 female) to ensure equal nutrition across litters. At 14 days of age, pups were sensitized with pepsin-trypsin digested gliadin and cholera toxin (CT) three times in one week (n=15). At 21 days of age, pups were weaned and placed either on a gluten-containing diet (n=7), (equivalent of 20g/d of gluten in a human diet -high dose-) or an isocaloric GFD (n=8) until 10 weeks of age. Non-sensitized controls (n=7) received only CT and were kept on the GFD. At sacrifice, serum was collected for anti-TG2 and anti-gliadin antibodies (AGA). Jejunal tissue was collected for histological analysis using villus-to-crypt (V/C) ratios and CD3+ intraepithelial lymphocytes (IEL) counts. Results Gluten-sensitized mice placed on a gluten-containing diet post-weaning had lower V/C ratios and higher CD3+ IEL counts compared with controls (p<0.01). Pre-weaning sensitized mice that were kept on a GFD post-weaning had sustained decreases in V/C ratios and higher CD3+ IEL counts (p<0.01). Out of 15 sensitized mice, 7 developed positive anti-gliadin IgA (p=0.02) and 4 had positive anti-TG2 IgA antibodies (p=0.01) in intestinal contents, irrespective of gluten in the diet. None of the controls had detectable AGA or anti-TG2 antibodies. Conclusions Pre-weaning gluten sensitization of DR3-DQ2 mice induced prolonged gluten immunopathology that did not reverse after 5 weeks on a GFD. Our results indicate that young DR3-DQ2 mice are susceptible to gluten sensitization, with sustained immunopathology, suggesting a critical window of vulnerability in familial carriers of DQ2.5. This novel model will be useful to investigate environmental cofactors at the first time of gluten introduction to the diet. Funding Agencies CIHR

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