Development of the Antibody Response to a Vaccine during Growth of Juvenile Japanese Amberjack

We investigated the antibody dynamics at different growth stages of Japanese amberjack Seriola quinqueradiata to determine the timing of first IgM production. Vaccination trials of juveniles were then conducted using a formalin-inactivated Vibrio anguillarum serotype J-O-3 vaccine to characterize the changes in vaccine-specific IgM and efficacy at each growth stage. In whole-body analyses, although total IgM was slightly detected at 1 day post-hatching (dph), it was undetectable until 15 dph and then increased from 23 to 57 dph. Levels of IgM specific to V. anguillarum J-O-3 were significantly elevated in fish vaccinated at and after 60 dph. Relative percentage survival of vaccinated fish was 52.6% and 100% at 51 dph and ≥61 dph, respectively. These results suggest that the IgM response to the vaccine developed between 51 and 60 dph (body weight: 0.45 ± 0.04 to 1.15 ± 0.06 g; standard length: 2.68 ± 0.09 to 3.90 ± 0.08 cm), coinciding with the increase in vaccine efficacy. These data also suggest that development of the humoral immunity was delayed from the initiation of IgM production.