Oncolytic Virus-Engineered Extracellular Vesicles Rewire Glioblastoma Immunity.

Immunotherapy with oncolytic Herpes simplex virus type 1 (oHSV-1) shows promise for glioblastoma; however, clinical benefit remains uncommon due to tumour- and host-mediated immunosuppression, which limits immune targeting of residual glioblastoma stem-like cells (GSCs). To address this barrier, extracellular vesicles (EVs) harvested from oHSV-1-infected GSCs (EVOV) were evaluated for their immunomodulatory capacity by priming peripheral blood mononuclear cells (PBMCs) ex vivo and in vivo. In GSC-PBMC organoids analysed by single-cell RNA sequencing, IFN-response and antigen-presentation programs were induced in both immune and tumour compartments, despite the GSC state. EVOV organoid transcriptome associated with patient tumour antigen-processing programs linked to improved clinical outcome, and EVOV immunopeptidomics identified candidate biomarker peptides that were also detected in patient immunopeptidomes from the clinical-trial cohort. In PBMC-engrafted NOD scid gamma mice bearing intracranial GSC xenografts, EVOV delivery increased circulating interferon (IFN) levels and enhanced systemic activation of T-cell subsets, while spatial transcriptomics revealed recruitment of peripheral immune cells to the tumour, accompanied by reprogramming of GSC states. Blocking vesicle-associated major histocompatibility complex I (MHC-I) attenuated EVOV-driven PBMC cytotoxicity against GSCs, supporting an MHC-I peptide-dependent mechanism of immune priming and a vaccine- or adjuvant-like, non-infectious, vesicle-based immunotherapeutic strategy.