Evaluation of Immune Protection of a Bivalent Inactivated Vaccine against Aeromonas salmonicida and Vibrio vulnificus in Turbot

The Aeromonas salmonicida is responsible for causing furunculosis in various fish species. Furunculosis is a ubiquitous disease that affects the aquaculture industry and causes the mass mortality of turbot. Vibrio vulnificus is a pathogen that causes skin ulcers and hemorrhagic septicemia in fish, resulting in significant mortality in aquaculture. In this study, we have established a bivalent inactivated vaccine against A. salmonicida and V. vulnificus with Montanide™ ISA 763 AVG as an adjuvant. This bivalent inactivated vaccine was used to immunize turbot by intraperitoneal injection, and the relevant immune indexes were detected. The results demonstrate that the bivalent inactivated vaccine exhibited a relative percent survival (RPS) of 77% following A. salmonicida and V. vulnificus intraperitoneal challenge. The vaccinated group exhibited higher levels of acid phosphatase activity and lysozyme activity compared to the control group. ELISA results showed a significant increase in serum antibody levels in immunized turbot, which was positively correlated with immunity. In the kidney tissue, related immune genes (TLR5, CD4, MHCI and MHCII) were up-regulated significantly, showing that the vaccine can induce cellular and humoral immune responses in turbot. In conclusion, the bivalent inactivated vaccine against A. salmonicida and V. vulnificus was immunogenic, efficiently preventing turbot from infection, which has the potential to be applied in aquaculture.