Engineering Extracellular Vesicles for Direct and Cross-Presentation in Tumor Vaccines

ABSTRACT: The central goal of therapeutic tumor vaccines is to activate tumor-specific CD8⁺ cytotoxic T lymphocytes (CTLs), a process critically dependent on efficient antigen presentation through major histocompatibility complex class I (MHC-I). Extracellular vesicles (EVs), natural mediators of intercellular communication, offer a versatile platform for tumor vaccine development because of their biocompatibility, lymphatic trafficking, and engineering flexibility. In this review, we summarize the biological basis of EV-mediated antigen presentation and highlight engineering strategies to enhance cross-presentation, including DC targeting, antigen–adjuvant co-delivery, and modulation of intracellular antigen processing. We further discuss strategies for direct antigen presentation, encompassing DC-derived EVs, tumor cell-derived pMHC-enriched EVs, and artificial antigen-presenting EVs (AP-EVs). In addition, we discuss synergistic strategies that integrate direct presentation with cross-presentation through EV hybridization and physiological modulation. By combining these complementary pathways, EV-based vaccines may achieve both rapid T-cell activation and sustained antitumor immunity. Finally, we discuss current challenges in standardized production, engineering efficiency, in vivo behavior, and clinical translation, and highlight future opportunities for intelligent, personalized, and AI-assisted EV vaccine design.