Effectiveness of formalin-killed vaccines containing CpG oligodeoxynucleotide 1668 adjuvants against Vibrio harveyi in orange-spotted grouper

Enhanced immune responses and effectiveness of refined outer membrane protein vaccines against Vibrio harveyi in orange‐spotted grouper (Epinephelus coioides)

“…The bacterial recoveries from internal tissues of the Japanese flounder were also significantly reduced when fish were immunized with antiserum before being infected with V. harveyi (Yu et al., ). The capacity to inhibit bacterial invasion in the bloodstream was indicated in vaccinated groupers that were highly protected from V. harveyi infections in our previous studies (Nguyen, Nguyen, Wang et al., ; Nguyen, Nguyen, Tsai et al., ). Therefore, the cross‐reactivity and bactericidal effect of the sera obtained from groupers immunized with rOmpK‐OmpU suggest that this vaccine is potentially capable of protecting groupers against heterologous vibrio pathogens.…”

“…The immunization of fishes with different vaccines induced higher antibody titres and demonstrated a positive correlation with protective efficacy following challenge with V. harveyi (Chuang et al., ; Nguyen, Nguyen, Wang et al., ; Nguyen, Nguyen, Tsai et al., ; Zhang et al., ). In our study, the immunization of groupers with V. harveyi rOMPs vaccines generated high levels of antibodies (IgM) against V. harveyi, with a salient increase observed in the rOmpK‐OmpU treatment group.…”

“…Our previous study highlighted a remarkably upregulated cytokine expression at the early stages postimmunization, elevated antibody titre, along with high protection conferred against challenge by both homologous and heterologous V. harveyi strains in groupers injected with a V. harveyi inactivated vaccine (Nguyen, Nguyen, Tsai et al., ). The degree of immune response following vaccination was also positively related to the protection rate in this species of fish receiving V. harveyi formalin‐killed vaccine formulated with plasmids carrying different a copy number of CpG ODN 1668 (Nguyen, Nguyen, Wang et al., ). The improved protective efficacy in the rOmpK‐OmpU fusion protein vaccine upon being challenged with V. harveyi indicated that the enhancement of immunity could be important for combating infection and preventing pathogenic infections.…”

“…The specific primers used for RT‐qPCR in this study are listed in Table . The β‐actin gene, shown to be the most stable reference gene, has also been widely used for studying immune gene expression in groupers; thus, it was utilized as an internal control gene (Dan, Zhang, Li, & Li, ; Huang et al., ; Nguyen, Nguyen, Wang, Wang, & Chen, ; Nguyen, Nguyen, Tsai et al., ). RT‐qPCR was performed in the CFX96 Touch™ Real‐Time PCR Detection System (Bio‐Rad, USA) using the iQSYBR Green Supermix (Bio‐Rad, USA) in 10‐μl reaction volumes, and each sample was run in duplicates.…”

“…Six weeks after PI, the V. harveyi rOmpK‐, rOmpU‐, rOmpK‐OmpU‐, ISA‐ and PBS‐injected fishes ( n = 20) were intraperitoneally injected with 0.1 ml of the Vh strain (1.6 × 10 8 CFU/ml) (Nguyen, Nguyen, Wang et al., ; Nguyen, Nguyen, Tsai et al., ); testing was carried out in duplicate. An additional group of twenty groupers were kept in the same culturing system as a nonchallenge control group.…”