Effects of recombinant Lactobacillus casei from Aeromonas hydrophila ompA and flaA genes on the growth and immunity in common carp (Cyprinus carpio)

To construct recombinant Lactobacillus casei with ompA and flaA of Aeromonas hydrophila and to detect the growth and immunogenicity of their expression products to common carp, Cyprinus carpio, the target genes were cloned into Lactobacillus Shuttle expression plasmid pPG612, and electric-transfered into L. casei. Fish were fed with dietary mixed with different recombinant L. casei for 56 days, and we weighed and collected serum and tissues, and analyzed the growth and related immune index changes; feeding at 56 days after the immunization, the growth index results showed that the recombinant L. casei had no significant difference compared with the control group, which showed that it had no effect on growth, immune indexes. Results showed that level of IgM in serum was significantly increased, alkaline phosphatase (AKP), lysozyme (LZM), superoxide dismutase (SOD), catalase (CAT), Complement 3 (C3) and Complement 4 (C4) were also significantly increased, qRT-PCR detection found that the expression levels of Interleukin 1β (IL-1β), Interleukin 8 (IL-8), Tumor Necrosis Factor α (TNF-α), Nuclear factor-kappa B (NF-κB), Toll-like receptor 5 (TLR) and myeloid differentiation factor 88 (MYD88) in liver, spleen, kidney and intestinal tissues after immunization increased significantly to varying degrees; the expression of TLR5 in the Lc-mcs-flaA group was higher than that in Lc-mcs-ompA groups; after challenge, the immune protection rates of Lc-mcs-ompA and Lc-mcs-flaA were 59% and 54%, respectively, and the survival rate was significantly higher than control group. The constructed recombinant L. casei Lc-mcs-ompA and Lc-mcs-flaA immuned carp could stimulate the body to activate immune response, thereby increasing its survival rate. It is an oral solution for preventing fish Aeromonas hydrophila infection. The research and development of immune preparations laid the foundation and provided scientific theoretical basis.