Impact of ATEVs and EV-DNA on transcriptional profile of dendritic cells in lymph nodes

Antigen processing and presentation (APP) is essential for adaptive immunosurveillance in all nucleated cells. Here we describe a novel mechanism through which secreted factors other than cytokines, specifically extracellular vesicles (EVs) released from activated T cells (ATEVs) drive a positive feedback loop that enhances antigen presentation and immune responses in normal physiology and cancer. ATEV-induced immunogenicity relies on extravesicular double-stranded DNA (EVDNA) and granzyme B (Gzmb). ATEV-DNA is notably abundant, primarily consisting of genomic DNA enriched in copies of specific genes, including numerous APP machinery genes. Mechanistically, ATEV transfer of APP machinery genes to recipient dendritic or tumor cells is facilitated by Gzmb disruption of recipient cell nuclear integrity. DNAse treatment of ATEVs removed the majority of EVDNA, preventing APP machinery upregulation in recipient cells, which in turn failed to recruit T lymphocytes into tumors. Notably, ATEVs hold promise as an immune-boosting therapeutic, particularly in restoring MHC-I antigen processing and presentation, and synergize with checkpoint blockade therapy in several immunotherapy-refractory tumors. Collectively, our findings uncover a novel mechanism through which ATEVs boost APP and anti-tumor immunity. Gzmb-mediated nuclear transfer opens new avenues for non-viral gene delivery, offering potential for enhanced intranuclear gene transport and expression efficiency. Naïve C57BL/6 mice received i.v. injections retro-orbitally of PBS, 50 µg of NTEVs or 25 µg of ATEVs (containing 10 µg of EV-DNA), or 25 µg of Baseline-ZERO DNase-pretreated ATEVs every other day for in total 3 doses. Subsequently, cervical lymph nodes were subjected to FACS sorting of CD45+CD11b-CD11c+ dendritic cells (DCs) for RNAseq profiling