CAR-Tregs as a Strategy for Inducing Graft Tolerance.

Purpose Of The Review: The adoptive transfer of alloantigen-specific regulatory T cells (Tregs) following organ transplantation is an emerging treatment paradigm that may induce tolerance and reduce the risk for graft rejection. In particular, redirecting Treg specificity via expression of synthetic chimeric antigen receptors (CARs) has demonstrated therapeutic promise in several preclinical studies. In this review, we highlight recent progress and remaining barriers to the clinical translation of CAR-Treg therapies.

Recent Findings: CAR Tregs targeting human leukocyte antigen (HLA)-A2 showed antigen-specific activation and superior protective function relative to polyclonal Tregs. Adoptively transferred anti-HLA-A2 CAR Tregs prolonged the survival of HLA-A2-positive grafts in humanized mouse models.

Summary: Donor HLA molecules are attractive candidate antigens to target with CAR Tregs in transplantation due to mismatched HLA only expressed on the transplanted organ. The feasibility of this approach has been demonstrated by several independent groups in recent years. However, substantial challenges in CAR design and preclinical modeling must be more extensively addressed prior to clinical application.