Multi-adjuvant emulsion system stabilized via mannosylated chitosan nanoparticles for subunit vaccine delivery

Adjuvants, which are vaccine ingredients substances that amplify antigen-specific immune responses, enhance the ability of antigen-presenting cells (APCs) to process and present antigens and hold great market potential. However, the development of adjuvants faces various challenges, including limited functionality, poor stability, and weak effects on cellular immunity, considerably restricting their application. Herein, we prepared a Pickering emulsion using mannose-modified chitosan nanoparticles (CNPs) and squalene for subunit vaccine delivery. In this delivery system, mannose-modified chitosan can target APCs and promote endocytosis. Chitosan and squalene synergistically function as dual adjuvants, enhancing immune responses. This delivery system can substantially improve cellular immunity, which is inadequate in case of commercial subunit vaccines. Furthermore, the emulsion exhibits good stability and antigen reservoir effect after injection to ensure continuous antigen release. This study presents an innovatively designed polysaccharide emulsion vaccine, demonstrating the strong immune response of the associated multi-adjuvant system and providing a valuable practical reference for the fabrication of vaccine adjuvant formulations.