The immunogenicity of Aha1, an OMP of
Aeromonas hydrophila
mediating the adhesion of bacteria onto the mucosal surface of hosts has been established. In this study, recombinant vectors, pPG1 and pPG2, carrying a 1366 bp DNA fragment that was responsible for encoding the 49 kDa Aha1 from
A. hydrophila
were constructed, respectively, then electroporated into a probiotic strain
Lactobacillus casei
CC16 separately to generate two types of recombinants,
L. casei-
pPG1-Aha1 (Lc-pPG1-Aha1) and
L. casei
-pPG2-Aha1 (Lc-pPG2-Aha1). Subsequently, these were orally administered into common carps to examine their immunogenicity. The expression and localization of the expressed Aha1 protein relative to the carrier
L. casei
was validated via Western blotting, flow cytometry, and immune fluorescence separately. The recombinant vaccines produced were shown high efficacies, stimulated higher level of antibodies and AKP, ACP, SOD, LZM, C3, C4 in serum in hosts. Immune-related gene expressions of cytokines including IL-10, IL-1β, TNF-α, IFN-γ in the livers, spleens, HK, and intestines were up-regulated significantly. Besides, a more potent phagocytosis response was observed in immunized fish, and higher survival rates were presented in
common carps
immunized with Lc-pPG1-Aha1 (60%) and Lc-pPG2-Aha1 (50%) after re-infection with virulent strain
A. hydrophila
. Moreover, the recombinant
L. casei
were shown a stronger propensity for survivability in the intestine in immunized fish. Taken together, the recombinant
L. casei
strains might be promising candidates for oral vaccination against
A. hydrophila
infections in common carps.