Immunogenicity and Protective Efficacy of Three Inactivated Vibrio anguillarum Serotype O3 Vaccine Preparations

Abstract:

Vibrio anguillarum, an etiological agent of fish septicemia, has caused great economic losses in many marine and fresh water fish. Vaccination is an effective and safe approach to control fish septicemia. The pathogenicity V. anguillarum serotype O3 in cultured marine fish of China promotes us to evaluate the immunogenicity and protective efficacy of three V. anguillarum serotype O3 inactivated vaccine. Three V. anguillarum serotype O3 strains (SMP1, SMP3, and SMP4) were rejuvenated in flounder Paralichthys olivaceus and then were determined for lethal dose 50% (LD50) in Trichogaster trichopterus which had been acclimated to 10 salinity. The result showed that LD50 of SMP1, SMP3 and SMP4 were 105.1 CFU/ml, 104.7 CFU/ml and 105.4 CFU/ml, respectively. Three inactivated vaccine were obtained by incubation of V. anguillarum with 0.2% formaldehyde for 36 h at 28℃. Each vaccine was used to vaccinate flounder P. olivaceus via intraperitoneal injection with a dosage of 108 CFU/ml. Specific serum antibody titers against V. anguillarum cells were detected evidently (P<0.05) at 7 d post vaccination, and the highest titers of 1:1280(SMP1), 1:640 (SMP3) and 1:905 (SMP4) were detected at 4 weeks post vaccination (P<0.05). Meanwhile, the relative percent survival rates (RPS) were 94.4% (SMP1), 100% (SMP3) and 73.7% (SMP4). These results indicated that V. anguillarum serotype O3 inactivated vaccines were able to induce immune response in fish and provide effective protection against V. anguillarum infection, and SMP3 is the best candidate for vaccine development and application.