Direct delivery of immune modulators to tumour-infiltrating lymphocytes using engineered extracellular vesicles.

Extracellular vesicles (EVs) are important mediators of cell-cell communication, including immune regulation. Despite the recent development of several EV-based cancer immunotherapies, their clinical efficacy remains limited. Here, we created antigen-presenting EVs to express peptide-major histocompatibility complex (pMHC) class I, costimulatory molecule and IL-2. This enabled the selective delivery of multiple immune modulators to antigen-specific CD8 T cells, promoting their expansion in vivo without severe adverse effects. Notably, antigen-presenting EVs accumulated in the tumour microenvironment, increasing IFN-γ CD8 T cell and decreasing exhausted CD8 T cell numbers, suggesting that antigen-presenting EVs transformed the 'cold' tumour microenvironment into a 'hot' one. Combination therapy with antigen-presenting EVs and anti-PD-1 demonstrated enhanced anticancer immunity against established tumours. We successfully engineered humanized antigen-presenting EVs, which selectively stimulated tumour antigen-specific CD8 T cells. In conclusion, engineering EVs to co-express multiple immunomodulators represents a promising method for cancer immunotherapy.