Different Approaches To Expressing Edwardsiella Tarda Antigen GAPDH In Attenuated Vibrio Anguillarum For Multivalent Fish Vaccines

With the development of gene technology, live multivalent vector vaccine has been used in aquaculture industry. In our previous work, an attenuated Vibrio anguillarum named MVAV6203, has been developed and proved to be a good vaccine candidate. In this work, we aimed to effectively express protective antigen GAPDH of Edwardsiella tarda in attenuated Vibrio anguillarum to establish a multivalent V. anguillarum vector vaccine. Several strategies were compared between low vs high copy plasmid-mediated antigen expression, in vivo inducible vs constitutive antigen expression, intracellular vs surface-displaying antigen expression. Zebrafish (Danio rerio) was applied as the fish model to evaluate the immune protection of the V. anguillarum vector vaccine candidates. Our results demonstrated that V. anguillarum MVAV6203 (patLNG40) which harbors a low copy plasmid-loaded antigen surface-display system under the control of a constitutive promoter presented the best protective efficacy against the infection of Vibrio anguillarum and Edwardsiella tarda. And further experiments based on turbot also showed the same results. The established multivalent vaccine showed potential value for further application in aquaculture.