Faithful Modeling of Terminal CD8 T Cell Dysfunction and Epigenetic Stabilization In Vitro

Epigenetic scarring of terminally dysfunctional CD8 T cells hinders long-term protection and response to immune checkpoint blockade during chronic infections and cancer. We developed a faithful in vitro model for CD8 T cell terminal dysfunction as a platform to advance T cell immunotherapy. Using TCR-transgenic CD8 T cells, we found that 1-week peptide stimulation, mimicking conditions in previous models, failed to induce a stable exhaustion program in CD8 T cells. In contrast, prolonged stimulation for 2-3 weeks induced T cell dysfunction but triggered activation-induced cell death, precluding long-term investigation of exhaustion programs. To better mimic in vivo exhaustion, we provided post-effector, chronic TGFβ1 signals, enabling survival of chronically stimulated CD8 T cells for over 3 weeks. These conditions induced a stable state of terminal dysfunction (T _Dysf ), marked by a stable loss of effector, cytotoxicity, and memory programs, along with mitochondrial stress and impaired protein translation. Importantly, transcriptomic and epigenetic analyses confirmed the development of terminal exhaustion-specific signatures in T _Dysf cells. Adoptive transfer of T _Dysf cells revealed their inability to recall effector functions or proliferate after acute LCMV rechallenge. This novel tractable model system enables investigation of molecular pathways driving T cell terminal dysfunction and discovery of new therapeutic targets for cancer or chronic infections.