Construction and analysis of the immune effect of Vibrio harveyi subunit vaccine and DNA vaccine encoding TssJ antigen

Abstract Vibrio harveyi, a severe pathogen infects different kinds of sea animals, causes huge economic loss in aquaculture industry. In order to control the Vibriosis disease caused mainly by V. harveyi and other Vibrio spp., the best solution lies in developing corresponding efficient vaccines. In this study, we have cloned and analysed a putative antigen TssJ from the T6SS of V. harveyi, which has the potential as a vaccine against infection. The sequence analysis and western blotting experiments indicated that TssJ anchored in outer membrane and there were several antigenic determinants existed on its extracellular region. Two forms of universal vaccines, subunit vaccine and DNA vaccine, were developed based on TssJ and applied in Trachinotus ovatus. The results showed that both of the two vaccines could generate a moderate protection in fish against V. harveyi. The relative percentage survival (RPS) of subunit vaccine and DNA vaccine were 52.39% and 69.11%, respectively. Immunological analysis showed both subunit vaccine and DNA vaccine enhanced acid phosphatase, alkaline phosphatase, superoxide dismutase, and lysozyme activities. Specific serum antibodies against TssJ in the fish vaccinated with subunit vaccine was much higher than that in the DNA vaccine group. Several immune-related genes, i.e., IL10, C3, MHC Iα, MHC IIα, and IgM, were induced both by the two forms of vaccines. TNFα and Mx were only upregulated in the DNA vaccine group. However, the induction levels of these genes induced by DNA vaccine were higher than subunit vaccine. All these findings suggested that TssJ from V. harveyi had a potential application value in vaccine industry.