Immune effects of the vaccine of live attenuated Aeromonas hydrophila screened by rifampicin on common carp (Cyprinus carpio L)

Abstract Aeromonas hydrophila , as a strong Gram-negative bacterium, can infect a wide range of freshwater fish, including common carp Cyprinus carpio , and cause the huge economic loss. To create the effective vaccine is the best way to control the outbreak of the disease caused by A. hydrophila . In this study, a live attenuated A. hydrophila strain, XX1LA, was screened from the pathogenic A. hydrophila strain XX1 cultured on medium containing the antibiotic rifampicin, which was used as a live attenuated vaccine candidate. The immune protection of XX1LA against the pathogen A. hydrophila in common carp was evaluated by the relative percent survival (RPS), the specific IgM antibody titers, serum lysozyme activity and the expression profiles of multiple immune-related genes at the different time points following immunization. The results showed that the variable up-regulations of the immune-related genes, such as the pro-inflammatory cytokine IL-1β , the chemokine IL-10 and IgM , were observed in spleen and liver of common carp injected in the vaccines with the formalin-killed A. hydrophila (FKA) and the live attenuated XX1LA. Specific antibody to A. hydrophila was found to gradually increase during 28 days post-vaccination (dpv), and the RPS (83.7%) in fish vaccinated with XX1LA, was significant higher than that (37.2%) in fish vaccinated with FKA ( P P A. hydrophila , which can be applied in aquaculture of common carp to prevent from the disease outbreak in the future.