Study on the immune enhancement of different immunoadjuvants used in the pentavalent vaccine for turbots

In this study, we investigated the immune enhancing effects of different adjuvants used in a pentavalent vaccine for turbots. The pentavalent vaccine consisted of inactive bacterial cells from five common pathogenic strains (Vibrio anguillarum, Vibrio scophtalmi, Edwardsiella tarda, Vibrio harveyi and Vibrio alginolyticus) and the adjuvants were astragalus polysaccharides (APS), propolis, and the Freund's complete adjuvant (FCA). Turbots were immunized with the pentavalent vaccine alone or with one of the adjuvants, and the immune efficiency was evaluated by measuring the activities of lysozyme (LSZ) and superoxide dismutase (SOD), and serum antibody titers. Fish were also challenged with the pathogens after immunization and the relative percent survival (RPS) was assessed. Our results showed that APS, propolis, and FCA had significant immune-enhancing effects on turbots as shown by the higher titers of antibodies against the pathogens, increased LSZ and SOD activities, and enhanced RPS after challenge with pathogens. Among the three adjuvants, FCA had the most significant immune synergistic effects with the vaccine, and APS and propolis had lower and similar immune synergies.