Beyond the genetic code: orchestrating epigenetic and immune landscapes with multivalent mRNA-exosome vaccines.

mRNA therapeutics are transitioning from transient anti-viral vaccines into precise cancer immunotherapies capable of orchestrating potent antigen-specific T-cell and humoral responses. However, therapeutic resistance within immunologically "cold" tumors remains a formidable barrier, necessitating multiaxial optimization across transcript architecture, neoantigen selection, delivery vector engineering, and tumor microenvironment (TME) reprogramming. This review synthesizes critical breakthroughs in mRNA biochemistry-including chemical nucleotide modifications, optimized untranslated regions, structural codon adjustments, and stringent purification methodologies-that extend transcript longevity while limiting off-target reactogenicity to maximize functional antigen expression. We evaluate multiomic neoantigen discovery workflows leveraging genomics, transcriptomics, immunoproteomics, and computational HLA-binding algorithms to refine patient-specific target selection. Next, we dissect advanced lipid nanoparticles, surface-functionalized biomaterials, and engineered extracellular vesicles optimized to enhance antigen-presenting cell tropism and lymphoid homing. We further detail how vaccine-induced cytokine fluxes actively remodel the TME, successfully reversing local immune tolerance and driving robust effector leukocyte infiltration into the tumor stroma. Specifically, we highlight the convergence of mRNA-mediated cytokine signaling and epigenetic imprinting, which cooperatively induce trained immunity for durable preventive surveillance. Finally, we delineate rational combinations with immune checkpoint blockades while addressing translational challenges: identifying predictive biomarkers, mapping presentation kinetics, and structuring adaptive clinical trial frameworks.