185-OR: T-Cell Receptor Repertoires during Type 1 Diabetes Development
Authors: MITCHELL ANGELA M. , BASCHAL ERIN E. , MCDANIEL KRISTEN , PYLE LAURA , WAUGH KATHLEEN , STECK ANDREA , YU LIPING , GOTTLIEB PETER , REWERS MARIAN , NAKAYAMA MAKI , MICHELS AARON W. 
Published: May 2022

In type 1 diabetes (T1D) , T cells target and destroy pancreatic beta cells. T cells express T cell receptors (TCRs) which recognize peptide antigens, and each TCR is unique to a given T cell. To understand the TCR repertoire during T1D development, we used next generation sequencing to detect TCRβ chains from longitudinal peripheral blood DNA samples at four time points from genetically at-risk cases (n=29) who progressed to T1D and age/sex/HLA matched controls (n=25) beginning early in life (median age 1.4 years) in the Diabetes Autoimmunity Study in the Young (DAISY) . Over 50 million TCRβ chains were sequenced, and the repertoires became less diverse (i.e., more clonal) over time with age in both groups (p&lt;0.001) . Principal component analyses of TCRβ V gene usage identified a subset of cases (n=11) that had higher frequencies of specific V genes beginning early in life before islet autoantibody seroconversion compared to the remaining cases and controls. The subset of cases were more likely to be double positive for GADA and IA-2A compared to the remaining cases (p=0.008) . Previously, we sequenced ∼3,500 αβTCRs from the residual islets of T1D organ donors (n=9) and identified 44 TCRs that recognize preproinsulin (PPI) . We searched for the PPI-reactive TCRβs (identical V gene, J gene, and CDR3) , and 15 TCRβs (6 CD4 and 9 CD8) were found to be shared in DAISY participants. The PPI CD4 TCRβ sequences (templates) were more frequent in cases compared to controls, 180 vs. 14 (p&lt;0.001) , but CD8 PPI templates were similar between cases and controls, 29 vs. 25. Using an algorithm to identify additional TCRs predicted to recognize similar PPI peptides, we found that these TCR clusters were more frequent in cases compared to controls and accumulated after islet autoantibody seroconversion. Lastly, PPI TCRs and clusters were identified in a separate cohort of new onset T1D patients (n=143, mean age 12.5 years) . Our results demonstrate that islet-derived TCR clusters have the potential to be a biomarker prior to clinical T1D onset.

Disclosure
A.M.Mitchell: None. M.Nakayama: None. A.W.Michels: Employee; ImmunoMolecular Therapeutics, Stock/Shareholder; ImmunoMolecular Therapeutics. E.E.Baschal: None. K.Mcdaniel: None. L.Pyle: None. K.Waugh: None. A.Steck: None. L.Yu: None. P.Gottlieb: Advisory Panel; Janssen Research & Development, LLC, ViaCyte, Inc., Other Relationship; IM Therapeutics, Research Support; Caladrius Biosciences, Inc., Immune Tolerance Network, National Institute of Diabetes and Digestive and Kidney Diseases, Novo Nordisk, Precigen, Inc., Tolerion, Inc. M.Rewers: Consultant; Janssen Research & Development, LLC, Medscape, Provention Bio, Inc., Research Support; Dexcom, Inc., JDRF, Roche Diagnostics USA.

Funding
National Institutes of Health (DK108868, DK110845, DK032083, DK032493, DK116073) Juvenile Diabetes Research Foundation (3-PDF-2020-943-A-N) Leona M. & Harry B. Helmsley Charitable Trust (2103-05093) Colorado Clinical and Translational Science Institute (TR002535)