Oral Administration of Expressing Flagellin A Protein Confers Effective Protection against in Common Carp, .

is a pathogen capable of infecting humans, livestock and aquatic animals, resulting in serious economic losses. In this study, two recombinant expressing flagellin A (FlaA) of , Lc-pPG-1-FlaA (surface-displayed) and Lc-pPG-2-FlaA (secretory) were constructed. The immune responses in fish administered with recombinant were evaluated. The two recombinant were orally administered to common carp, which stimulated high serum IgM and induced higher ACP, AKP, SOD and LYZ activity. Using qRT-PCR, the expression of IL-10, IL-8, IL-1β, TNF-α and IFN-γ in the tissue of fish immunized with recombinant was significantly ( < 0.05) upregulated, which indicated that recombinant could activate the innate immune system to trigger the cell immune response and inflammatory response. Furthermore, recombinant was able to survive the intestinal environment and colonize in intestine mucosal. The study showed that after being challenged by , fish administered with Lc-pPG-1-FlaA (70%) and Lc-pPG-2-FlaA (50%) had higher survival rates compared to Lc-pPG and PBS, indicating that recombinant might prevent infection by activating the immune system to trigger immune responses. We demonstrated that flagellin as an antigen of vaccine, is acceptable for preventing infection in fish. The recombinant expressing FlaA may be a novel mucosal vaccine for treating and controlling .