Engineered CD40-biosensor-expressing Treg cells as a cell therapy approach for inflammatory diseases

Restoring immune tolerance by engineered regulatory T cell (Treg) therapy is a promising strategy to treat patients suffering from autoimmune and inflammatory diseases. However, in many of these conditions, relevant disease-driving antigens are unknown. Therefore, suitable target (auto-)antigens for antigen-specific Treg cell therapy are rarely available. We present a novel artificial immune biosensor for Treg cells that circumvents this limitation by targeting the immune costimulatory protein CD40-ligand (CD40L), transiently expressed by activated T cells. The artificial immune receptor (AIR) comprises a CD40-derived extracellular binding domain, an intracellular costimulatory signaling domain, and a T cell receptor signaling domain of the CD3-ζ-chain. After interaction with its membrane-bound ligand, this synthetic receptor triggers a TCR-like activation program in Treg cells including induction of Treg effector molecules and cell proliferation. In a mouse model of graft-versus-host disease, transfer of CD40-AIR Treg cells significantly improved survival and demonstrated immune control of the alloantigen-reactive T cell compartment. Expression and signaling of the corresponding human CD40-AIR illustrate the potential for translating this concept. Engineering Treg cells with a CD40L-targeting sensor that detects activated T cells presents a promising therapeutic approach for a broad range of T cell-mediated inflammatory diseases.