Pancreatic islet-specific engineered T _regs exhibit robust antigen-specific and bystander immune suppression in type 1 diabetes models

Adoptive transfer of regulatory T cells (T regs ) is therapeutic in type 1 diabetes (T1D) mouse models. T regs that are specific for pancreatic islets are more potent than polyclonal T regs in preventing disease. However, the frequency of antigen-specific natural T regs is extremely low, and ex vivo expansion may destabilize T regs , leading to an effector phenotype. Here, we generated durable, antigen-specific engineered T regs (EngT regs ) from primary human CD4 + T cells by combining FOXP3 homology-directed repair editing and lentiviral T cell receptor (TCR) delivery. Using TCRs derived from clonally expanded CD4 + T cells isolated from patients with T1D, we generated islet-specific EngT regs that suppressed effector T cell (T eff ) proliferation and cytokine production. EngT regs suppressed T effs recognizing the same islet antigen in addition to bystander T effs recognizing other islet antigens through production of soluble mediators and both direct and indirect mechanisms. Adoptively transferred murine islet-specific EngT regs homed to the pancreas and blocked diabetes triggered by islet-specific T effs or diabetogenic polyclonal T effs in recipient mice. These data demonstrate the potential of antigen-specific EngT regs as a targeted therapy for preventing T1D.