Abstract

This study was carried out to determine the protective efficacy of inactivated recombinant cell vaccine expressing OmpTs (37 kDa) and OmpW (22 kDa) of Aeromonas hydrophila against the virulent strain of A. hydrophila strain Ah1sa5 in African catfish and to observe the presence of GALT in fish after vaccinated with the recombinant protein vaccine compared to control and placebo vaccine groups. Two hundred and forty African catfish were divided into five major groups. Three groups were vaccinated intraperitoneally (IP) with inactivated recombinant cells concentration of 1 x 10⁷ CFU/ml and one group that was vaccinated with recombinant cell alone without insert and the last group was an unvaccinated group. Vaccines were injected on day 0 and booster dose given on day 14. On day 28 challenge test were done where all fish from all groups were IP injected with virulence bacteria, A. hydrophila strain Ah1sa5 inoculums with concentration of 4.0 x 10⁸ CFU/ml. During the course of study, fish were collected randomly from all groups and guts were collected for histological examination to observe the aggregation of GALTs. All of the vaccinated groups had a significantly higher protection (P < 0.05) than placebo vaccine and control groups. This level of protection may be due to high antibody responses as demonstrated by aggregation of GALTs following vaccination. These results suggest that the recombinant cell vaccines OmpTs and OmpW could effectively stimulate both specific and non-specific immune responses and protect against A. hydrophila infection. Therefore, OmpTs and OmpW may be developed as potential vaccine candidates against A. hydrophila infection.