Bacterial Outer Membrane Vesicle-Based Versatile In Situ Nanovaccine Enhancer Synergized With Radiofrequency Ablation Against Hepatocellular Carcinoma.

Radiofrequency ablation (RFA) is the primary curative therapy for early hepatocellular carcinoma (HCC). However, incomplete ablation inevitably occurs in clinical practice, leaving residual tumors that are highly immunosuppressive, refractory to immune checkpoint inhibitors, and prone to recurrence and metastasis. To address this, we developed a novel nanoformulation, OMVbsAb-MAL, by modifying bacterial outer membrane vesicles (OMVs) with DEC205/PD-L1 bispecific antibodies and maleimide (MAL) groups. Following local administration after RFA, OMVbsAb-MAL forms thioether bonds with tumor proteins, thereby capturing abundant tumor-associated antigens (TAAs) released in situ. The nano-sized OMVbsAb-MAL penetrates the tumor stroma and traffics efficiently to tumor-draining lymph nodes. Significantly, the bispecific antibodies on the nanoplatform enable specific DC recognition, mediating targeted delivery of TAAs to DCs within tumors and lymph nodes. Concurrently, OMVbsAb-MAL blocks PD-L1, thereby restoring DC function and alleviating PD-L1-mediated immune suppression. In combination with TAAs, the immunogenic vesicles markedly promote DC maturation, resulting in robust antigen presentation and potent T cell activation. Consequently, OMVbsAb-MAL synergizes with RFA to elicit both local and systemic antitumor immune responses, effectively suppressing residual and distant tumors, and thus provides a promising strategy for integrating RFA with immunotherapy in HCC.