Introduction: Recent successes in xenogeneic organ transplantation in humans raise hopes of overcoming the worldwide organ shortage. The availability of cells, tissues, but also solid organs of porcine origin could counteract this critical circumstance from a medical point of view and reduce the increasing gap between available donor organs and patients with end-stage organ dysfunction by xenotransplantation. In contrast, the immunological barrier must be overcome. With the development of new immunosuppressants and the generation of less immunogenic donor animals, this barrier can be reduced. However, it is unclear whether this approach will lead to long-term acceptance.

Methods: Here, we describe the generation of a specific chimeric antigen receptor (CAR) that recognizes the porcine SLA*0401 molecule.

Results: Modification of natural Tregs (nTregs) with the SLA CAR alters the specificity of polyspecific Tregs for antigen-specific regulators without affecting their phenotype, stability, or epigenetics. Compared to nTregs, SLA CAR-Tregs showed significantly better ability to control strong immune responses in vitro and in vivo. In the humanized mouse model (NRG mice), the use of SLA CAR-Tregs resulted in the prevention of xenogeneic target cell rejection. In the highly immunogenic skin transplantation model, adoptive SLA CAR-Treg transfer protected porcine skin from recipient-driven immune responses. In the streptozotocin-induced diabetes model in NRG mice, porcine islet cells transplanted under the kidney capsule were able to restore normoglycemia after SLA CAR-Treg transfer.

Conclusion: These modified CAR-Tregs have great potential for inclusion in xenogeneic organ transplantation protocols in humans, extending graft longevity through their potent immunoregulation.