Immunogenicity of inactivated formalin-killed Photobacterium damselae subsp. piscicida combined with Toll-like receptor 9 agonist in Cobia Rachycentron canadum

• Published in: Aquaculture Vol. 492; pp. 369 - 378
• Main Authors: Byadgi, Omkar, Uyen, Nguyen Hoang Nhat, Chou, R.L., Guo, Jiin-Ju, Lee, Yan-Horn, Lee, Jai-Wei, Cheng, Ta-Chih
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2018
• Subjects: Adjuvanticity; Cobia Rachycentron canadum; Immune response; Photobacterium damselae subsp. piscicida; Vaccination; Photobacterium damselae subsp. piscicida; Immune response; Adjuvanticity; Vaccination; Cobia Rachycentron canadum
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2018.04.035

The immune responses and protection efficacy of a vaccine containing inactivated formalin-killed Photobacterium damselae subsp. piscicida formulated with alum and different unmethylated Cytosine phosphorothioate Guanine oligodeoxynucleotides (CpG-ODN, including 2006, 2395, 1668, and control ODN 2137) as the adjuvant were investigated in cobia Rachycentron canadum. Results showed that, formulation with CpG-ODN 1668 significantly (P < .05) increased the expression of rctlr9a (11 and 20 fold in spleen and liver, respectively) and il-1β (4 fold in liver) in immunized fish. The highest lysozyme and peroxidase activities were also observed in fish immunized with CpG-ODN 1668 formulation. In addition, compared to other treatments, bactericidal activity using the bacterial survival percentage was significantly less in CpG-ODN 1668 formulation (25%). The antibody titer was significantly higher at 6 and 21 dpi from CpG-ODN 1668 (OD = 0.27 ± 0.02) and CpG-ODN 2006 (OD = 0.24 ± 0.018) formulations. Fish immunized with CpG-ODN 1668 and 2395 formulations protected R. canadum with survival rate of 90 & 70% by P. damselae subsp. piscicida until 3 weeks post-challenge. This study has indicated that different tlr9 agonists have different abilities to augment immune response and protection against Photobacterium. CpG-ODN 1668 can be used as an adjuvant for R. canadum vaccination. •In-vivo co-administration of CpG 1668 + FKB + alum increased expression of tlr9a and il-1β.•CpG 1668 + FKB + alum compounds jointly elicited a humoral response in serum.•CpG 1668 + FKB + alum combination protected R. canadum after P. damselae subsp. piscicida challenge.•Demonstrated that different CpG-ODNs have different protection abilities in cobia upon P. damselae subsp. piscicida challenge.