Tuning peptide specificity for T cell tolerance in Type 1 diabetes

Abstract Type 1 Diabetes (T1D) is a classical T-cell mediated autoimmune disease, and fundamental data have implicated insulin as the dominant autoantigen in T1D disease. In the NOD mouse model of T1D, notable studies have found that mice lacking native insulin expression but with an altered insulin sequence to maintain blood glucose levels are protected from insulitis and diabetes. Growing evidence also indicates how the insulin peptide is bound within MHC Class II (peptide register) is essential in determining the strength of interactions and recognition of autoreactive T-cells. We have uncovered a unique peptide binding characterized by the dominant insulin epitope InsB:9–23. The majority of InsB:9–23-specific CD4 T-cells in the periphery recognize insulin bound in the unusual register 3, and knocking in this single amino acid variation into just one copy of the insulin gene in NOD mice, confers protection against T1D. In addition, these mice were protected from T1D, even when treated with checkpoint inhibitor blockade, unlike their wild-type littermates. Introducing this superagonist epitope into the NOD mouse has allowed us to address several key questions surrounding pathways of peptide generation, presentation by MHC molecules, and recognition by auto-reactive pathogenic T cells. In addition, we have been able to model how central and peripheral tolerance mechanisms can be altered when major epitopes in the Insulin gene are mutated, allowing us to explore means of dominant tolerance to understand the potential for translation into treatments for T1D. Supported by grants from NIH (R01 DK133443-01A)