Oral vaccination with recombinant Lactobacillus casei expressing Aeromonas hydrophila Aha1 against A. hydrophila infections in common carps

Abstract

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.

Immunogenicity and protective efficacy of OmpA subunit vaccine against Aeromonas hydrophila infection in Megalobrama amblycephala: An effective alternative to the inactivated vaccine

“…LZM has high bactericidal or hemolytic activity against pathogens, and ACP and AKP may contribute to promoting immunogenic responses (42)(43)(44), which thereby play vital roles in host defense system. In the present study, the levels of LZM, ACP and AKP in vaccinated groups were up-regulated, which was similar to the results in C. carpio with A. hydrophila Aha1 vaccine immunization and other previous studies, indicating that both OmpA subunit vaccine and inactivated vaccine can improve host non-specific immunity and enhance their ability to resist infection (10,36).…”

“…Indian carp immunized with OmpC subunit vaccine also achieves immune protective effect, and detectable cross-reacts of rOmpC antiserum with different Aeromonas lysates ( 34 ). In addition, other studies have evaluated the high immunogenicity of A. hydrophila OMPs, including Omp38 ( 24 ), OmpA1 ( 26 ), OmpF ( 35 ), Aha1 ( 36 ). In this study, we evaluated the relative survival rate of the prepared A. hydrophila inactivated vaccine and OmpA subunit vaccine upon bacterial infection, and both vaccines exhibited excellent immune protection to the juvenile M. amblycephala , among which the OmpA subunit vaccine showed better immune protective effect than that of the inactivated vaccine.…”

Importance of Probiotics in Fish Aquaculture: Towards the Identification and Design of Novel Probiotics

“…L. lactis has also been used to immunize against hirame novirhabdovirus (HIRRV) in flounder ( Paralichthys olivaceus ) [ 131 ]. In C. carpio (common carp), oral administration of recombinant L. casei expressing epitopes of A. veronii [ 132 , 133 , 134 , 135 ] or A. hydrophila confers protection against these pathogens [ 136 ], while the administration of L. plantarum expressing G protein of spring viremia of carp virus (SVCV) [ 137 ] and the ORF81 protein of koi herpesvirus (KHV) grants protection against both viruses in challenge assays, with high titers of IgM after its oral administration to C. carpio [ 138 ]. L. lactis has also been successful in triggering immunization against SVCV in C. carpio [ 139 ].…”

“…The oral administration of these probiotics either, in the feed or by intubation every 3 days, was enough to induce the presence of IgM in serum mucosa in Nile tilapia and rainbow trout 4 days post-immunization [ 125 , 126 , 127 , 128 , 129 , 130 , 142 ]. The level of antibodies increased in the case of a booster applied in most cases 30 days after the first immunization [ 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 140 , 141 ] ( Table 2 ). The fusion of the antigen to a CWA domain did not increase the level of serum antibodies with respect to the construction without the CWA domain.…”

“…In the case of L. plantarum NC8 expressing the IAG-52X antigen from I. multifiliis , oral administration for four weeks was enough to induce the expression of C3, IgM, and MHC-I and increase survival from 40% to 60% in challenge assays [ 144 ]. L. casei CC16 expressing outer membrane protein of A. veronii TH0426 [ 132 , 133 , 134 , 135 , 140 ] or A. hydrophila [ 136 , 142 ] was also able to stimulate immune responses, increasing lysozyme activity, alkaline and acid phosphatases, and superoxide dismutase activity in serum, which suggests stimulation of the innate immune response. This stimulation was also associated with an induction of the expression of IL-1β and IFN-γ in the spleen, and TNF-α in the head-kidney.…”