Protection efficacy of NNV, GIV and NNV-GIV vaccines in giant groupers
Date Issued
2015
Date
2015
Author(s)
Chen, Wei-Hsu
Abstract
Grouper is an economically important fish species for aquaculture industry in Taiwan. Nervous necrosis virus (NNV) and grouper iridovirus (GIV) are two major viral pathogens of grouper fries and fingerlings, and have caused mass mortality during epidemics. Vaccination is an effective prophylaxis strategy for viral disease. To date, many research papers focus on NNV and GIV monovalent vaccines, but no report concerns NNV-GIV bivalent vaccine. The aim of this study is to compare the protection efficacy of NNV-GIV bivalent vaccine with those of NNV and GIV monovalent vaccines in giant groupers. At 4 weeks post vaccination (wpv), both NNV monovalent and NNV-GIV bivalent vaccines could induce high neutralizing antibody titers (ND50 ≥ 473) against NNV, and protect fish against NNV infection with cumulative mortalities 40% lower than that of control fish. High relative percent survival (RPS = 81.8 and 92.9) after NNV challenge tests were consistently observed in the fish with high neutralizing antibody titers (ND50 ≥ 781). By indirect ELISA, NNV-specific antibody titers in the serum of immunized fish peaked at 2 and 3 wpv, and kept significantly higher than those of control fish until 24 wpv. On the contrary, the neutralizing antibody titers against GIV induced by GIV and NNV-GIV vaccines were much lower than those against NNV induced by NNV monovalent and bivalent vaccines; however, the RPS of GIV monovalent and bivalent vaccine groups were all higher than 70 in GIV challenge experiments. In bivalent vaccine-immunized fish, the expression levels of MHC-I and MHC-II gene at 2 wpv were significantly higher than those in the control fish; furthermore, the expression levels of CD8α gene at 2 wpv and CD4 gene at 4 wpv both elevated. Therefore, it is suggested that NNV-GIV bivalent vaccine may also provide protection through induction of cellular immunity. In conclusion, NNV-GIV bivalent vaccine could provide good protection against NNV and GIV similar to two monovalent vaccines, and it will reduce labor cost and injection stress of fish during vaccination.
Subjects
nervous necrosis virus (NNV)
grouper iridovirus (GIV)
inactivated vaccine
bivalent vaccine
antibody
cellular immunity
SDGs
Type
thesis
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