Oncolytic virus OH2 induces PD-L1 upregulation via NF-κB signaling and synergizes with anti-PD-L1 therapy in prostate cancer through a targeted extracellular vesicle delivery system

BACKGROUND: Prostate cancer (PCa) is a prevalent malignancy with limited treatment options for advanced stages. Oncolytic virotherapy represents a promising immunotherapeutic approach, but its efficacy and underlying mechanisms in PCa, particularly concerning immune checkpoint regulation, remain unclear. METHODS: The antitumor effects of the oncolytic virus oncolytic herpes simplex virus type 2 (OH2) were evaluated in PCa cell lines and mouse models. Transcriptome sequencing, western blot, chromatin immunoprecipitation-sequencing-quantitative PCR, and flow cytometry were employed to investigate the mechanism of programmed death 1 ligand 1 (PD-L1) regulation. A targeted delivery system, reactive oxygen species (ROS)-responsive aptamer-conjugated anti-prostate-specific membrane antigen (PSMA) extracellular vesicles (RRA-AP-EVs), was engineered from anti-PSMA single chain variable fragment (scFv)-modified extracellular vesicles and an ROS-responsive PD-L1 blocking aptamer. OH2 was loaded via membrane extrusion, and the resulting OH2@RRA-AP-EVs were tested for targeting and therapeutic efficacy following intravenous administration. RESULTS: OH2 effectively killed PCa cells but simultaneously activated the IKK/I-κBα/p65 pathway, leading to PD-L1 upregulation and adaptive immune resistance. While combining OH2 with anti-PD-L1 improved outcomes, clinical translation was hindered by delivery challenges. The novel OH2@RRA-AP-EVs system demonstrated precise tumor targeting and ROS-triggered local PD-L1 blockade. Intravenous injection of OH2@RRA-AP-EVs showed superior tumor control (inhibiting tumor growth by 70% vs free OH2) and enhanced CD8+T cell infiltration and function compared with free OH2 (greater than twofold increase in intratumoral CD8+T cell infiltration along with over twofold upregulation of key effector molecules). CONCLUSION: This study identifies a mechanism of OH2-induced PD-L1 expression in PCa and provides a versatile, targeted delivery platform that enables effective intravenous viro-immunotherapy, overcoming key translational barriers.