Chitosan and mannose-modified dual-functional mRNA-LNP vaccines for robust systemic and mucosal immune responses.

Mucosal vaccination plays a crucial role in activating frontline immune responses, preventing infection and transmission of respiratory pathogens. However, the development of effective mRNA mucosal vaccines faces multiple challenges, including mucosal barriers, suboptimal immune cell targeting, and limited induction of mucosal immunity. In this study, we develop a dual-functional mRNA-LNP-CS+Man vaccine by utilizing DMG-PEG2000-Chitosan and DMG-PEG2000-Mannose, capable of penetrating the pulmonary mucosal barrier and targeting immune cells in the lungs. The results show that, following intratracheal administration, mRNA-LNP-CS+Man exhibits prolonged retention in the lungs for up to 72 h, with widespread distribution across the entire lung and achieving high mRNA transfection throughout the lung, particularly in immune cells. After two immunizations, the vaccine induces strong systemic and mucosal immune responses compared to the unmodified LNP, including efficient production of IgG and IgG2a in serum, IgG and SIgA in bronchoalveolar lavage fluid, and Th1-type cytokines. Significant activation of lung germinal center B (GC B) cells and tissue-resident memory T (TRM) cells were observed, alongside the establishment of effective immune memory. The vaccine demonstrates strong protective efficacy against SARS-CoV-2 D614G pseudovirus in the lungs, offering a novel strategy for mRNA mucosal vaccine development.