Immune responses in giant groupers after vaccination with inactivated bivalent vaccine against betanodavirus and ranavirus

• Published in: Aquaculture 2024-11, Vol.592, p.741179, Article 741179
• Main Authors: Kai, Yu-Hsuan, Chang, Chun-Kuei, Li, Hong-Qi, Chen, Wei-Hsu, Chi, Shau-Chi, Wu, Yu-Chi
• Format: Article
• Language: English
• Subjects: antibody formation; aquaculture; Asia; Betanodavirus; Bivalent vaccine; Epinephelus lanceolatus; gene expression; Grouper; histology; Infectious spleen and kidney necrosis virus; Iridovirus; kidneys; mortality; Ranavirus; spleen; vaccination; vaccines; viral genome
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2024.741179

Nervous necrosis virus (NNV) and grouper iridovirus (GIV) are the two major viral pathogens affecting farmed groupers in Asia. In this study, an inactivated bivalent vaccine for preventing viral infections caused by both NNV and GIV was developed. Histological changes in organs were not observed in groupers immunized with the bivalent vaccine. In challenge tests, the cumulative mortality of giant groupers (Epinephelus lanceolatus) immunized with the bivalent vaccine was lower than that of groupers in the control and monovalent vaccine groups. Compared with monovalent vaccines, the bivalent vaccine exhibited synergistic and inhibitory effects on antibody production, including reducing the NNV-specific antibody titer, increasing the GIV-specific antibody titer, and decreasing the GIV-neutralizing antibody titer. Immune gene expression analyses revealed that only the bivalent vaccine induced CD8α gene expression in the spleen, unlike the monovalent vaccines. Furthermore, Mx gene expression was increased in the spleen and head kidney after immunization with the bivalent vaccine but not after immunization with the monovalent vaccines. The inactivated forms of NNV and GIV contained in the bivalent vaccine retained their viral genomes, which elicited Mx gene expression in vitro. Additionally, immunization with the GIV monovalent vaccine and the NNV–GIV bivalent vaccine decreased cumulative mortality in groupers after a red sea bream iridovirus (RSIV) challenge; however, the cross-protective effect of the NNV–GIV bivalent vaccine against RSIV was smaller than that of the GIV monovalent vaccine. In conclusion, the NNV–GIV bivalent vaccine is safe and exhibits protective effects against NNV and GIV in groupers. •NNV–GIV bivalent vaccine was safe and exhibited protective effect in groupers.•NNV–GIV bivalent vaccine showed some synergy and inhibition on antibody production.•NNV–GIV bivalent vaccine induced CD8α and Mx gene expression in vivo.•GIV monovalent vaccine exhibited cross-protection against RSIV.•Cross-protection against RSIV of NNV–GIV bivalent vaccine was diminished.