Intratracheal Delivery of mRNA Lipid Nanoparticles Reprograms Alveolar Macrophages for Pulmonary Cancer Immunotherapy

Pulmonary delivery of lipid nanoparticle (LNP)-based mRNA vaccines offers a promising strategy for localized lung cancer immunotherapy, yet how distinct pulmonary administration routes determine cellular targeting and therapeutic efficacy remains poorly understood. Here, we systematically evaluate intranasal and intratracheal delivery of mRNA-LNP vaccines and reveal a route-dependent immunological mechanism governing lung-targeted tumor vaccination. Although intratracheal administration yields only a 2.6-fold increase in total pulmonary protein expression compared to intranasal delivery, it produces a striking 26.8-fold enhancement in functional mRNA transfection efficiency within alveolar macrophages, the dominant antigen-presenting cell population in the alveolar space. This selective targeting reprograms alveolar macrophages toward an activated antigen-presenting phenotype, promoting efficient antigen presentation, robust CD8+ T-cell responses, and superior prophylactic and therapeutic efficacy in pulmonary tumor models. Notably, local depletion of alveolar macrophages completely abolishes the antitumor protection conferred by intratracheal vaccination, establishing their indispensable role in mediating pulmonary mRNA vaccine efficacy. Together, these findings provide mechanistic insights into lung-targeted mRNA cancer vaccination driven by alveolar macrophage engagement, providing critical insights for the design of next-generation LNP-based nanomedicines for lung cancer immunotherapy.