| Summary: | 碩士 === 國立臺灣大學 === 動物學研究研究所 === 93 === Nervous necrosis virus (NNV) is the most economically important pathogen of cultured groupers in Taiwan causing mass mortality 80~100% in fry and larvae. The aim of this study is to develop inactivated NNV vaccine, and a method of treating or preventing VNN through immersion immunization of grouper fry. The culture supernatant of NNV-infected GF-1 cells was collected after cytopathic effect (CPE) complete, and used for the preparation of inactivated vaccine and for challenge test. The effectiveness of vaccine was expressed by relative percentage survival (RPS), and significant protection usually means a RPS for vaccinated fish of at least above 30%. Four sorts of inactivated NNV vaccines (F-I, F-II, BPL, BEI) were prepared and used for immersion immunization of grouper fry. The result revealed that the inactivated vaccines (F-I, F-Il, BEI) could protect grouper fry from NNV infection, but BPL-prepared NNV vaccine failed to provide protection. Particularly, the RPS of BEI group was very high (83%~95%), and no virus was detected in vaccinated fish. Subsequently, the comparative results of vaccine without and with nano-encapsulation showed that effectiveness of nano-encapsulated vaccine improved. The RPS of fish immunized by encapsulated F-II vaccine was 83%, much higher than that of un-capsulated F-II vaccine with 100-fold viral concentration. The minimal NNV concentration for effective protection of BEI un-capsulated vaccine was 106 TICD50/ml. In addition, it was found that 20 min was enough for immersion immunization, but one month was necessary for the development of efficacious immunity after vaccination. Finally, the result of immersion challenge indicated that the protection of the vaccination could last for at least three months (RPS=82%). Consequently, NNV inactivated vaccine is believed to become an important approach for the control of NNV disease.
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