Oral therapy with colonization factor antigen I (CFA/I) prevents development of type 1 diabetes in the Non-obese Diabetic (NOD) mice

Antigen (Ag)-specific tolerization prevents type 1 diabetes (T1D) in experimental models, but is less effective in humans. Several auto-Ags are fundamental to disease development, suggesting the etiology of T1D is heterologous and limiting the effectiveness of Ag-specific therapy. To address this limitation, we utilized colonization factor antigen I (CFA/I) fimbriae from Escherichia coli, which can inhibit murine models of autoimmune diseases via the induction of bystander tolerance. We hypothesize that CFA/I fimbriae can prevent onset of T1D in non-obese diabetic (NOD) mice through Ag-independent stimulation of regulatory T cells (Tregs). To test this hypothesis, an oral dosing regimen was applied to NOD mice and showed a 50% reduction of disease incidence, and an 8-fold increase in IL-10- and IFN-?-producing Tregs. Tregs analyzed at different disease time-points showed varied phenotypes, Foxp3+CD4+ T cells appearing early and IL-10+IFN-?+Foxp3+CD4+ Tr1s appearing late. Notably, LL-CFA/I treatment suppressed splenic TNF-a+CD8+ T cells 6-fold at 11 weeks and promoted a distinct and healthier microbiome. At 17 weeks, IFN-?+CD4+ T cells were suppressed 10-fold, and at 30 weeks, Tbet+CD4+ T cells were suppressed in the pancreas. These results suggest that the Treg response stimulated by LL-CFA/I evolves with the pathogenesis of T1D to protect against disease.