Simulating CD8 T cell exhaustion: A comprehensive approach

Abstract Immunotherapy has revolutionised the treatment of multiple cancer types, however, these treatments only work for a proportion of patients and biomarkers to predict response are lacking. One correlate of response is the reinvigoration of a subset of CD8 T cells that have an exhausted phenotype and impaired functionality. In order to develop new therapies, reproducible models are required to identify candidate target genes that enables the reversal of key hallmarks of T cell exhaustion. Here we describe the development of an in vitro model by chronically stimulating T cells with their cognate antigen and performed an in depth temporal phenotypic characterisation. This model recapitulates many of the critical hallmarks of exhaustion, including increased expression of canonical exhaustion surface markers, impaired proliferation, reduced cytokine production, decreased release of cytotoxic granules, and metabolic alterations, including dysfunctional mitochondria. These exhaustion hallmarks were validated using an in vivo model and a gene signature identified which robustly define the shared in vitro and in vivo exhausted state. Critically, this signature is also observed in tumour infiltrating T cells from multiple human tumour types, validating the translational potential of this model for discovering and triaging new therapies.