Immune engineered extracellular vesicles to modulate T cell activation in the context of type 1 diabetes

Extracellular vesicles (EVs) are small, biologically active, cell-secreted vesicles that can affect immune responses through antigen presentation and co-stimulation or co-inhibition. We generated designer EVs to modulate autoreactive T cells in the context of type 1 diabetes by engineering K562 cells to express HLA-A*02 (HLA-A2) alongside co-stimulatory CD80 and/or co-inhibitory PD-L1. EVs presenting HLA-A2 and CD80 activated CD8+ T cells in a dose, antigen, and HLA-specific manner. Adding PD-L1 to these EVs produced an immunoregulatory response, reducing CD8+ T cell activation and cytotoxicity in vitro. EVs alone could not stimulate T cells without antigen presenting cells (APCs), suggesting that EVs act by cross-dressing APCs. EVs lacking CD80 were ineffective at modulating CD8+ T cell activation, suggesting that both peptide-HLA complex and costimulatory molecules are required for EV-mediated immune modulation through APC cross-dressing. These results provide mechanistic insight into the rational design of EVs as a cell-free, yet precision medicine-based approach to immunotherapy that can be tailored to promote antigen-specific immune tolerance or pro-inflammatory responses.