93-OR: Clonal Expansion of Islet Reactive CD4 T-Cells with Early Disease Progression in Type 1 Diabetes Free

Introduction & Objective: Islet antigen reactive (IAR) T cells play an important role in pancreatic β-cell destruction in type 1 diabetes (T1D) and are clonally expanded after T1D diagnosis, indicative of in vivo antigen exposure. The objective of this study was to determine if clonal expansion of IAR CD4 T cells occurs prior to T1D onset and is associated with risk for disease progression.

Methods: The study included prospective blood samples collected from islet autoantibody (Aab) positive individuals enrolled in the TrialNet Pathways to Prevention and Long Term Investigative Follow-up in TrialNet studies. IAR CD4 T cells were isolated using a CD154 activation assay from PBMC samples of a cross-sectional cohort of Aab negative (n=6), 1 Aab+ >18y (n=6), 1 Aab+ <14y (n=3), and >1 Aab+ (n=6) donors with increasing risk for progression to T1D. Cells were analyzed by single-cell RNA-sequencing to identify T cell receptor α/β pairs and full transcript profiles. Clonal expansion was visualized using circos plots and analyzed using Simpson’s diversity. Transcript profiles were analyzed by unsupervised clustering and differential gene expression using Seurat v4.

Results: Clonal expansion of IAR CD4 T cells was observed primarily in the >1 Aab+ at-risk group compared to the single Aab+ or Aab negative groups. The transcript profiles of IAR CD4 T cells formed clusters based on differentiation status from naïve to T effector memory phenotypes and revealed an enrichment of T effector memory cells in >1 Aab+ at-risk subjects.

Conclusion: These results suggest that IAR CD4 T cell clonal expansion and enrichment of an effector memory transcript profile may accompany the progression to multiple Aab and increased risk for development of T1D. Further studies with longitudinal samples from subjects progressing from single to multiple Aab and T1D onset will validate and extend these findings to determine if IAR CD4 T cells are a biomarker of disease progression.