Tumor-derived extracellular vesicles induce invalid cytokine release and exhaustion of CD19 CAR-T Cells

Although CD19 chimeric antigen receptor-T (CAR-T) cells therapy has achieved unparalleled success in B cell malignancies. The dysfunction of CAR-T cells due to exhaustion is considered as a key factor for treatment failure, and the mechanisms of exhaustion remain elusive. Extracellular vesicles (EVs), important media for communication between tumor and immune cells, may contribute to CAR-T cell exhaustion. Here, we demonstrated that CD19+ tumor cells derived EVs (NALM6-EVs) can carry CD19 antigen and activate CD19 CAR-T cells. The transient activation induced a supraphysiologic inflammatory state with increased release of multiple cytokines. Besides, the sustained activation led CD19 CAR-T cells to enter an exhausted state with upregulated inhibitory receptors, decreased expansion ability, exaggerated effector cell differentiation and impaired antitumor activity. Transcriptomic profiling validated these findings and identified dynamic changes in CD8+ effector T, CD8+ exhausted T, CD8+RRM2+ T and T helper cell subpopulations during activation to exhaustion, as well as changes in many cytokines, inflammatory and immune-related pathways. Our findings identify a credible mechanism of CAR-T cell exhaustion that driven by tumor-derived EVs and provide a novel possible trigger for early cytokine release syndrome.