Background/Purpose: Autoantigen-specific regulatory T cells (Tregs) are potent, and specific, suppressors of pathogenic autoimmunity, and can be harnessed to treat autoimmune disease. In primary Sjögren’s disease (pSjD), a key target autoantigen is the Ro60 RNA-binding protein, characterised by a strong association with the inheritance of HLA-DRB1*03:01. However, no antigen-specific treatment exists for pSjD. Thus, we propose that an engineered Ro60-specific T cell receptor (TCR)-Tregs could be used to treat patients with pSjD.

Methods: Data and biospecimens from patients with pSjD and healthy control (HC) participants were sourced from the South Australian SjD Registry & Biobank, and Monash University, respectively. Identification of the immunogenic regions of Ro60 was carried out using in vitro co-culture assays with Ro60 derived peptides; then binding and presentation of the lead immunogenic autoepitope were proved by solving the crystal structure of the peptide-HLA protein complex. Ro60-specific TCR were identified by performing high-throughput 10X single cell TCR sequencing, and a lead Ro60-specific TCR was selected. Then, the Ro60-specific TCR was lentivirally-transduced onto HC and pSjD patient-derived Tregs to produce engineered Ro60-specific Tregs (Ro-Tregs). The immunosuppressive capacity of these Ro-Tregs was tested using in vitro co-cultures.

Results: We successfully identified a Ro60-derived autoepitope and solved the crystal structure of this autoepitope in complex with HLA-DRB1*03:01. Ro-Tregs from both HC and patients with pSjD were characterised by activation and proliferation upon recognition of the Ro60 autoepitope and upregulation of CD69 and GARP. Importantly, Ro-Tregs from both HC and patients with pSjD displayed a 2-fold increase in suppressive effect on CD4+ T conventional cells as compared to non-engineered polyclonal Tregs.

Conclusion: We demonstrated that the Ro60 autoepitope is presented in the context of HLA-DRB1*03:01, and showed that engineered Ro-Tregs surpass non-engineered polyclonal Tregs in suppressing Ro60-specific pro-inflammatory responses from CD4+ T conventional cells.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/genetically-engineered-ro-specific-regulatory-t-cells-to-treat-primary-sjogrens-disease/