Tracking GAD-specific T-cell expansions in Type 1 diabetes by intradermal GAD-Alum challenge

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Abstract

Identifying and monitoring autoreactive T cells that drive beta cell destruction remains a major obstacle to developing effective immunotherapies for type 1 diabetes (T1D). These cells are extremely rare in peripheral blood and cannot be accessed directly from the pancreas. We used intradermal injection of Glutamic Acid Decarboxylase (GAD)-Alum to recruit GAD-specific T cells to accessible sites in the skin and skin-draining lymph nodes (LNs), sampled by skin suction blisters and ultrasound-guided LN aspiration. Peripheral blood samples obtained before GAD injection were restimulated with GAD in vitro to detect reactive CD4+ T cells. Single-cell RNA sequencing (scRNAseq) followed by re-expression of selected T cell receptors (TCRs) confirmed antigen specificity. Up to 70% of T cells at the skin injection site were clonally-expanded and 4 of 14 (28%) re-expressed TCRs were GAD-reactive. In LNs 1 of 14 (4%) clonally-expanded TCRs was GAD-reactive, representing ~0.08% of all T-cells. GAD-reactive cells across compartments displayed Th1 and Th17-associated transcription signatures. These results demonstrate the intradermal autoantigen challenge and scRNAseq, enable direct identification and molecular profiling of autoreactive T cells in vivo. This minimally invasive approach provides a powerful platform for tracking antigen-specific T cells to monitor disease activity and evaluate immune interventions in T1D.

Authors

Stephanie J. Hanna, Emma J.S. Robinson, Terri C. Thayer, Maki Nakayama, Laurie Landry, Robert Andrews, Garry Dolton, Joanne Davies, Evangelia Williams, James A. Pearson, Andrew K. Sewell, Parth Narendran, David Wraith, Alexandra Howell, Philippa Young, Mary Hart, Anton Lindqvist, F. Susan Wong, Tim I.M. Tree, Colin M. Dayan, Danijela Tatovic