Non-invasive vaccination enhances immune response and protects Asian seabass (Lates calcarifer) against Vibrio vulnificus infection

Abstract

Vibriosis, caused by Vibrio vulnificus, is a significant threat to the production of a commercially important species Asian seabass (Lates calcarifer). This study assessed the efficacy of a non-invasive vaccination strategy employing an immersion prime followed by oral boosts with an inactivated V. vulnificus vaccine. Juvenile seabass was initially vaccinated via immersion, followed by oral booster doses at 14- and 28-days post-vaccination (dpv). The immune response was assessed through the expression of immune-related genes - cytokines (IL1β, TNFα), T-cell markers (CD4, CD8), and immunoglobulin (IgM), in the head kidney and spleen; as well as systemic and mucosal antibody production in serum, mucus, and gut fluid. Vaccinated fish exhibited a significant upregulation of IL1β and TNFα in the head kidney and spleen, followed by sustained elevations in CD4 and CD8 expression. The antibody response showed a correlation with gene expression. Systemic, mucosal, and gut-associated antibody responses achieved peaks on day 35 before gradually declining, yet remaining significantly higher than in unvaccinated controls until day 49. A laboratory challenge at 43 dpv demonstrated that vaccinated group achieve an 84.6 % relative percent survival (RPS). These findings highlight that the immersion prime-oral boost strategy was effective in enhancing both systemic and mucosal immunity, providing robust protection against V. vulnificus. This approach offers a feasible, non-invasive vaccination strategy for prevention of vibriosis in farmed Asian seabass.