A respiratory mucosal vaccine based on chitosan/aluminum adjuvant induces both mucosal and systemic immune responses

The respiratory mucosa serves as a critical barrier against the invasion of pathogens. Effective mucosal vaccines are essential for enhancing local immunity. However, there is an urgent need to develop new mucosal adjuvants. Chitosan is preferred as a mucosal adjuvant due to its mucosal adhesion and immunostimulatory properties. In this work, a novel mucosal adjuvant was synthesized by combining nano-aluminum hydroxide and chitosan (Al-CS), formulating a particle size approximately 1.5 μm. In vitro assays revealed that Al-CS notably promotes antigen uptake by enhancing activation and maturation of dendritic cells and macrophages. Furthermore, in vivo experiments indicated that Al-CS could extend antigen release duration, facilitate immune cell migration to the lungs, stimulates antigen-presenting cell maturation, enhances antigen presentation and significantly improves both humoral and cellular immunity as well as B/T cell memory differentiation. The immunological potential of Al-CS exceeds that of either aluminum or chitosan alone, making it a promising and safe adjuvant for the advancement of mucosal vaccine carrier systems.