Respiratory mucosal vaccination can induce robust humoral and cellular immune responses, as well as effective mucosal immunity at the primary site of pathogen entry, and has been shown to provide superior protection against respiratory viral infections compared with traditional approaches. Among current vaccine technologies, mRNA vaccines offer unique advantages, including rapid development, flexible antigen design, and potent immunogenicity. However, efficient mucosal delivery of mRNA remains challenging due to biological barriers within the respiratory tract, including mucus clearance, limited cellular uptake, and instability during aerosolization. Furthermore, mRNA formulations intended for respiratory mucosal delivery require more stringent safety and tolerability profiles. Recent advances in nanoparticle engineering have accelerated the development of mRNA delivery systems optimized for respiratory mucosal immunization. This review aims to evaluate how nanoparticle engineering strategies can overcome respiratory mucosal barriers and improve the safety, stability, delivery efficiency, extrahepatic expression, and immunogenicity of mRNA vaccines and therapeutics. We summarize recent progress in engineered mRNA nanoparticle platforms for respiratory mucosal immunity, encompassing modified lipid nanoparticles (LNPs), polymer-based mRNA nanoparticles, and hybrid nanoparticle systems, including lipid-inorganic, polymeric hybrid, and lipid-extracellular vesicle (EV) nanoparticles. We further discuss optimization strategies for mucosal mRNA delivery, including the incorporation of appropriate adjuvants, the development of polyethylene glycol (PEG) alternatives, and advanced delivery approaches. Finally, we highlight current challenges and future directions for the rational design of next-generation mRNA nanoparticle platforms that can induce durable and broadly protective mucosal immunity against respiratory viral infections.
