Alpha-chain centric TCR metaclones in T1D

The National Institute of Allergy and Infectious Diseases awarded Benaroya Research Institute At Virginia Mason $267,000 on July 20, 2026, under the Allergy and Infectious Diseases Research program (CFDA 93.855) to investigate the role of shared T cell receptor alpha-chain junctions in Type 1 Diabetes autoimmunity.

The project examines human islet antigen-reactive CD4+ memory T cells from peripheral blood and their relationship to pancreatic-infiltrating T cells. Prior cross-sectional analysis found that 30 percent of islet antigen-reactive T cell receptors from circulating blood share T cell receptor alpha (TRA) junction sequences with perfect or single-mismatch alignment to pancreatic T cell receptors, with these shared TRA chains paired to diverse beta chains (TRB) to form TRA-chain-centric metaclones. The research tests the hypothesis that shared TRA junctions govern binding specificity and cross-reactivity toward islet autoantigens in Type 1 Diabetes. Aim 1 will use ectopic expression to determine whether metaclone T cell receptors sharing a TRA chain but bearing distinct TRB chains recognize the same islet and viral epitopes. Aim 2 will test whether shared TRA chains confer T cell receptor specificity and cross-reactivity when paired with diverse TRB chains from the endogenous T cell receptor repertoire.

Work is performed in Seattle, Washington. The period of performance runs through June 30, 2028.

Abstract

Human islet antigen reactive CD4+ memory t cells (IAR CD4+ t cells) from blood are widely studied for their role in autoimmune β cell destruction during type 1 diabetes (T1D). Despite much study, the role of IAR t cells during T1D remains poorly understood and IT is unclear whether and how rare autoreactive cells in peripheral blood represent autoimmunity in the pancreas. To address this GAP in knowledge, we examined the extent of IAR t cell infiltration in the pancreas by cross-sectional comparisons of paired α/β (TRA/TRB) t cell receptor (TCR) junction sequences between circulating IAR t cells and pancreatic infiltrating t cells (PIT) from different donors. Surprisingly, 30% of IAR tcrs from peripheral blood shared TRA junctions with perfect- or single- mismatch TRA junction protein sequences with PIT tcrs. Shared TRA chains were paired with diverse TRB chains in different cells, forming TRA-chain centric TCR metaclones, which had increased use of germline- encoded residues in epitope engagement, and a potential for cross-reactivity. However, the precise role of shared TRA sequences in TCR specificity and cross reactivity towards islet autoantigens is unknown. We hypothesize shared TRA junctions in TRA-chain centric metaclones govern the binding specificity and cross- reactivity of IAR tcrs, which contribute to autoreactivity in T1D. We propose two independent specific aims. Aim 1 will test IAR TRA chain junctions to determine the specificity and cross-reactivity of TRA chain- centric metaclone tcrs. We will utilize ectopic expression to test whether metaclone tcrs sharing a TRA chain, but distinct TRB chains recognize the same islet and viral epitopes associated with the shared chain. Aim 2 will test the hypothesis that that shared TRA chains confer TCR specificity and cross-reactivity when paired with diverse TRB chains from the endogenous TRB repertoire. We will express individual shared IAR TRA chains in TRA-deficient primary CD4⁺ t cells and assess whether they confer islet- and viral-epitope recognition when paired with diverse TRB chains from the endogenous TRB repertoire in T1D subjects. Successful completion of the proposed studies will provide new insight into antigen binding of TRA-centric IAR tcrs and will form the basis for future studies to determine their role in the development of T1D, and as potential biomarkers for disease onset and TCR- and t cell- based therapeutics.