Identifying and preventing antigen specific T cells in diabetes

SUMMARY Type 1 diabetes (T1D) is an autoimmune disease resulting from a breakdown in immunological tolerance caused by T cell-mediated destruction of islet beta cells. Diabetes is orchestrated by HLAII- restricted CD4+ T cells, through cellular interactions with both B cells and CD8+ T cells, resulting in autoantibody production and beta cell death, respectively. While anti-islet autoantibodies are currently the best predictors of T1D development, screening is limited to four islet antigens and no T cell biomarkers exist. Despite years of research, it is still unclear which antigen-specific CD4+ T cells initiate T1D. New evidence suggests that hybrid peptides (HP) formed from the fusion of islet β cell proteins may be critical antigens in T1D as recent studies identified HP-reactive CD4+ T cells from T1D patients and diabetic mice in vitro. These neo-antigens escape central tolerance and must be controlled by peripheral mechanisms including anergy or regulatory T cell control. In preliminary studies, we identified HP-specific CD4+ T cells in diabetic mouse models using tetramer reagents, and showed they are pathogenic and cause T1D in mouse transfer models. More importantly, we can block spontaneous T1D in the NOD mouse model targeting one hybrid peptide when presented in mouse MHCII using peptide-specific:MHCII blocking antibodies. Thus, we hypothesize that HPs are critical antigens and that autoreactivity to HPs initiates T1D. The goals of this proposal are to determine if HP-specific CD4+ T cells initiate T1D and if targeting them can lead to tolerance as a prevention or cure for T1D. The second goal of the grant is to determine if HP specific cells are relevant for human T1D and use of scRNA-seq analysis to uncover critical clues about shared transcriptional programs related to the pathogenic potential between human and mouse HP reactive T cells. Completion of this project could lead to better biomarkers to predict T1D risk and disease progression.