Investigation on the immune effect of a chitosan-based particle-in-oil-in-water emulsion.

[Display omitted] • Particle-in-oil-in-water multiple emulsion adjuvant is a promising vaccine adjuvant. • The adjuvant with chitosan nanoparticles as the internal water phase had good cellular and humoral immune effects. • The increase in the content of the internal aqueous phase helps to reduce antigen concentration and reduce the cost of antigen purification. Particle-in-oil-in-water (P/O/W) multiple emulsion adjuvants introduce particles into the internal water phase of a water-in-oil-in-water emulsion, combining the advantages of both particle and emulsion adjuvants to enhance humoral and cellular immune responses. In this study, we optimized P/O/W multiple emulsion adjuvants. Chitosan, poly (lactic-co-glycolic acid), and aluminum gel were used to prepare the particles, which were introduced into a water-in-oil-in-water emulsion to obtain three P/O/W multiple emulsion adjuvants. The immune enhancement effects and safety of the three adjuvants were compared, and it was proven that the adjuvant with chitosan nanoparticles in the internal water phase had good cellular and humoral immune effects. Simultaneously, the proportion of the internal water phase increased from 13% to 20%, reducing the antigen concentration required for embedding to one-third of the original concentration and expanding the application range of the composite adjuvant. [ABSTRACT FROM AUTHOR]