Evaluation of the protective immunogenicity of the N, P, M, NV and G proteins of infectious hematopoietic necrosis virus in rainbow trout Oncorhynchus mykiss using DNA vaccines

The protective immunogenicity of the nucleoprotein (N), phosphoprotein (P), matrix protein (M), non-virion protein (NV) and glycoprotein (G) of the rh abdovirus infectious hematopoietic necrosis virus (IHNV) was assessed in ra inbow trout using DNA vaccine technology. DNA vaccines were produced by amp lifying and cloning the viral genes in the plasmid pCDNA 3.1. The protectiv e immunity elicited by each vaccine was evaluated through survival of immun ized fry after challenge with Live virus. Neutralizing antibody titers were also determined in vaccinated rainbow trout Oncorhynchus mykiss fry (mean weight 2 g) and 150 g sockeye salmon Oncorhynchus nerka. The serum from the 150 g fish was also used in passive immunization studies with naive fry. O ur results showed that neither the internal structural proteins (N, P and M ) nor the NV protein of IHNV induced protective immunity in fry or neutrali zing antibodies in fry and 150 g fish when expressed by a DNA vaccine const ruct. The G protein, however, did confer significant protection in fry up t o 80 d postimmunization and induced protective neutralizing antibodies. We are currently investigating the role of different arms of the fish immune s ystem that contribute to the high level of protection against IHNV seen in vaccinated fish.