An oral vaccine based on chitosan/aluminum adjuvant induces both local and systemic immune responses in turbot (Scophthalmus maximus)

Oral vaccination is the most convenient method for disease protection in aquaculture due to possibility of adding vaccines as part of fish diet. However, low protective efficiency is the major problem of oral vaccination owing to some reasons, especially for antigens degradation. In this study, we developed an oral inactivated vaccine based on a chitosan/aluminum adjuvant system, and investigated immune response induced by the vaccine. As a result, Th1 and Th2 cells mediated immune responses were observed after the vaccination according to the upregulation of IL-6, IL-12, IFNγ and IgM genes expression that were deemed as the driver cytokines for triggering the responses. Moreover, ratio of IgT/IgM B cells was elevated in intestine after vaccination, while IgM antibodies were also observed in the sera of vaccinated fish, suggested that both local and systemic immune responses were induced by the inactivated vaccine. Totally, this oral vaccine can be used for V. anguillarum protection and this chitosan/aluminum system is an efficient candidate adjuvant for developing more vaccines in the future.