Protective Efficacy of Recombinant Glyceraldehyde-3-Phosphate Dehydrogenase Vaccine Against Vibrio alginolyticus in Asian Seabass (Lates calcarifer)

Vibriosis caused by Vibrio alginolyticus is a major bacterial disease in Asian seabass (Lates calcarifer) farming and leads to significant economic losses. The overuse of antibiotics has contributed to antimicrobial resistance, so there is a need for an effective prevention and control method, such as a vaccine against V. alginolyticus. In this study, we developed and evaluated formulations of a recombinant glyceraldehyde-3-phosphate dehydrogenase (rGAPDH) subunit vaccine against V. alginolyticus in Asian seabass. The GAPDH gene of V. alginolyticus was expressed in ClearColi BL21(DE3) Escherichia coli cells, and the 37 kDa rGAPDH protein was purified. Fish in the V1–V4 groups were intraperitoneally immunized with purified 37 kDa rGAPDH protein formulations comprising 5 µg rGAPDH without Algel (V1), 5 µg rGAPDH with Algel (V2), 10 µg rGAPDH without Algel (V3), and 10 µg rGAPDH with Algel (V4). Vaccinated fish exhibited significantly enhanced immune responses compared to the control group. The 10 µg adjuvanted formulation induced the highest serum agglutination titer at 14 days post-vaccination (DPV), which was sustained through 21 DPV, together with the greatest serum lysozyme and bactericidal activities. Expression analysis of complement factor H, cystatin B, HSP70, and HSP90α revealed tissue-specific and temporal transcriptional changes following vaccination, with distinct response patterns across vaccine formulations. Following challenge with V. alginolyticus, the V4 group achieved 100% relative percent survival (RPS), whereas V1, V2, and V3 groups provided RPS values of 39.47%, 63.16%, and 63.16%, respectively. These findings demonstrate that the 10 µg rGAPDH formulation containing aluminum hydroxide conferred complete protection following experimental challenge with V. alginolyticus under the conditions tested. The developed 37 kDa rGAPDH vaccine could serve as a promising and effective vaccine candidate for preventing vibriosis in Asian seabass farming.