Repeated stimulation or tonic-signaling chimeric antigen receptors drive regulatory T cell exhaustion

Regulatory T cell (Treg) therapy is a promising approach to improve outcomes in transplantation and autoimmunity. In conventional T cell therapy, chronic stimulation can result in poor in vivo function, a phenomenon termed exhaustion. Whether or not Tregs are also susceptible to exhaustion, and if so, if this would limit their therapeutic effect, was unknown. We studied how two methods which induce conventional T cell exhaustion – repetitive stimulation or expression of a tonic-signaling chimeric antigen receptor (CAR) – affect human Tregs. With each repetitive polyclonal stimulation Tregs progressively acquired an exhausted phenotype, and became less suppressive in vitro. Tregs expressing a tonic-signaling CAR rapidly acquired an exhausted phenotype and had major changes in their transcriptome and metabolism. Although tonic-signaling CAR-Tregs remained stable and suppressive in vitro, they lost in vivo function, as tested in a model of xenogeneic graft-versus-host disease. The finding that human Tregs are susceptible to exhaustion has important implications for the design of Treg adoptive immunotherapy strategies.Competing Interest StatementMKL received research funding from TxCell, Bristol-Myers Squibb, Pfizer, Takeda and CRISPR Therapeutics for work unrelated to this report. CLM holds several patent applications in the area of CAR based immunotherapy, and is a founder of, holds equity in, and receives consulting fees from Lyell Immunopharma which develops CAR based therapies. EWW holds several patent applications in the area of CAR based immunotherapy and receives consulting fees from Lyell Immunopharma. CLM is a member of the Parker Institute for Cancer Immunotherapy, which supports the Stanford University Cancer Immunotherapy Program.AbbreviationsCARChimeric antigen receptorECARextracellular acidification rateOCARoxygen consumption rateTconvconventional T cellTregRegulatory T cellTStonic signalingTSDRRegulatory T-cell-Specific Demethylated RegionView Full Text