Page 16 - Abstract Book ICOH4

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Development and evaluation of vaccines against Vibrio harveyi in orange-spotted grouper,
Epinephelus coioides

Shih Chu Chen

Abstract

Vaccination is the best strategic to prevention infectious diseases. Vibrio harveyi is a major bacterial
pathogen that causes serious vibriosis in cultured groupers, so considerable efforts are in practice to control the
pathogen. In the present study, we developed and evaluated the immune responses and protective efficacy of
inactivated and recombinant outer membrane protein (rOMP) vaccines against V. harveyi in orange-spotted
groupers. The vaccine candidates were (1) V. harveyi formalin-killed cells (FKC) plus Montanide ISA 763 AVG, (2)
TM
V. harveyi FKC combined with CpG ODN 1668-enriched plasmids (p30CpG and p60CpG), and (3) V. harveyi rOMPs
in addition to Montanide ISA 763 AVG. Antibody titers were significantly elevated in the vaccinated fish. A pivotal
TM
observation was that the vaccine highly protected the grouper from a homologous V. harveyi strain challenge with
relative percentage survival values of 100% and 91.7% at 6 and 12 weeks post-immunization, respectively.
Vaccinated fish also demonstrated strong cross-protection against a heterologous V. harveyi isolate challenge. The
vaccines containing V. harveyi FKC and CpG ODN 1668-enriched plasmids stimulated remarkably greater antibody
titers in vaccinated fish 2 weeks post-immunization. The relative percent survival after V. harveyi challenge was
significantly higher in FKC + p60CpG-vaccinated fish (96.2%) than in FKC + p30CpG-vaccinated (79.8%) and FKC-
vaccinated fish (59.9%). Notably, an enhanced immune response and significant protective efficacy against V.
harveyi infections were observed in the fusion protein vaccine-injected fishes with relative percent survival value of
81.8%. Additionally, the rOmpK-OmpU antisera presented a high bactericidal effect on not only V. harveyi, but also
V. parahaermolyticus and V. alginolyticus.

Keywords: V. harveyi, vaccines, immune responses, protective efficacy, orange-spotted grouper

THE 4 INTERNATIONAL CONFERENCE ON ONE HEALTH (ICOH)
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“Strengthening Collaboration in One Health Systems”