Abstract 3869: A human in-vitro T cell exhaustion model for assessing immuno-oncology therapies

Abstract Chronic stimulation of CD8 T cells either as a result of viral infection or within the tumor microenvironment can lead to a state of exhaustion, whereby T cells no longer make a productive effector response. Remobilisation of exhausted tumor specific CD8 T cells (TEX) presents a possible therapeutic strategy for driving anti-tumor T cell responses. The success of biologics targeting receptors and ligands associated with exhausted T cells such as PD-1/PD-L1 and CTLA-4 has spurred an acceleration of research to unravel the molecular processes that drive or maintain the exhausted state with the goal of developing treatments that target them. Effective therapeutic development necessitates reliable human in-vitro models that closely mimic disease conditions. To achieve this we adapted an in-vitro TEX model via application of flowing cytometry and time-lapse imaging techniques to kinetically assess TEX cell phenotype and function. Persistent and repeated rounds of polyclonal human CD8 T cell stimulation recapitulated distinctive characteristics of exhausted T cells including high expression of checkpoint receptors and upregulation of transcription factors known to suppress immune activation. Over 8 days and 4 rounds of stimulation TEX cells lost effector capabilities, producing lower levels of pro-inflammatory cytokines and became refractory to re-stimulation through the TCR. In functional cytotoxicity assays TEX cells exhibited substantial deficits in target killing compared to donor matched Teff cell counterparts. Checkpoint receptor blockade partially restored Teff function by enhancing immune mediated target cell death. Overall, this in-vitro TEX assay models key aspects of CD8 T cell exhaustion and offers a versatile and accessible platform to test novel therapeutics targeting exhaustion pathways either individually or in combination with checkpoint inhibitors to test if they fully restore effector function. Citation Format: Paulina Goral, Louise Brackenbury, Robert Nunan, Rhiannon Jenkinson. A human in-vitro T cell exhaustion model for assessing immuno-oncology therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3869.