W141 - Redirecting TCR Specificity in Regulatory T Cells Toward Class I HLA Antigens Mediates Tissue-specific Homing

Abstract Text: Background
Type 1 diabetes (T1D) is marked by the overexpression of class I major histocompatibility complex (MHC) antigens in pancreatic islets, which are targeted by islet-specific CD8+ T cells. Here, we aimed to improve regulatory T cell (Treg) infiltration into pancreatic islets by redirecting their specificity toward class I-restricted islet antigens.
Methods
Two HLA-A2 (*02:01) restricted TCRs were generated, one specific for ZnT8186-194 (clone D222D), the second for IGRP265-273 (clone 32), and were inserted into the TRAC locus of primary T cells and Tregs by homology-directed repair. In parallel, the CD4 co-receptor was swapped with either CD8 or CD8 molecules into the CD4 locus.
Results
The functional avidity of clone D222D was peptide-specific, CD8β dependent, and mediated in vivo trafficking towards transgenic cell lines expressing the Znt8 peptide but not HLA-A2+ human pancreatic islets. Interestingly, clone 32 exhibited antigen promiscuity despite a tetramer-specific staining, CD8α dependency, and mediated trafficking into HLA-A2 human pancreatic islets. Swapping the CD4 co-receptor to the CD8 and CD8 in engineered D222D and 32 CD4 T cells, respectively, enables specific recruitment in vivo. Engineered CD4to8 TCR Tregs maintained stable phenotypes, with significantly higher suppression activity than their polyclonal counterpart and showed co-receptor-dependent migration in vivo.
Conclusion
Tregs can be redirected against class I MHC-restricted islet antigens by co-engineering their TCRs and co-receptor. This approach demonstrates that TCR specificity, reflected by its functional activity, is crucial for tissue-specific trafficking, paving the way to improve the efficacy of Treg therapies for T1D.