Potentiality of a live vaccine with nervous necrosis virus (NNV) for sevenband grouper Epinephelus septemfasciatus at a low rearing temperature.

Nervous necrosis virus (NNV) is the causative agent of viral nervous necrosis (VNN), one of the most serious diseases in over 30 species of cultured marine fishes worldwide. Although several kinds of NNV vaccines have been developed, none of these vaccines have been yet marketed. Here, we demonstrate the potentiality of a live NNV vaccine for sevenband grouper Epinephelus septemfasciatus at a low rearing temperature (17°C).

Live vaccine of viral hemorrhagic septicemia virus (VHSV) for Japanese flounder at fish rearing temperature of 21°C instead of Poly(I:C) administration.

The process of "Poly(I:C) immunization" involves immunization of fish with a pathogenic live virus, followed by administration of Poly(I:C), which induces a transient, non-specific antiviral state. As a result, fish in an antiviral state survive the initial immunization with live virus. Moreover, these fish are able to mount a specific protective immune response against the injected pathogenic virus.

Protection of Japanese flounder Paralichthys olivaceus from viral hemorrhagic septicemia (VHS) by Poly(I:C) immunization.

In immunization of fish with polyinosinic-polycytidylic acid (poly[I:C], a synthetic double-stranded RNA, injection of Poly(I:C) followed by challenge with a live virus induces a transient, non-specific antiviral state by interferon activity. When exposed to a virus while in this antiviral state, the fish acquire a specific and protective immunity against the corresponding viral disease and survive. In the present study, the effiacy of Poly(I:C) immunization was investigated in japanese flounder Paralichthys olivaceus using viral hemorrhagic septicemia virus (VHSV) as a model; the minimum dose of Poly(I:C) required for inducing protection and the duration of the antiviral state were determined, and a potentially curative effect of Poly(I:C) administration was assessed.

Fish immunization using a synthetic double-stranded RNA Poly(I:C), an interferon inducer, offers protection against RGNNV, a fish nodavirus.

Viral nervous necrosis (VNN), caused by a fish nodavirus, is one of the most serious fish diseases worldwide. Here we report a unique vaccination method in sevenband grouper Epinephelus septemfasciatus using a synthetic double-stranded RNA polyinosinic polycytidylic acid (Poly(I:C)), an interferon inducer, followed by challenge with a live fish nodavirus. Fish injected with Poly(I:C) at 200 microg fish(-1) were highly protected from artificial challenge with red-spotted grouper nervous necrosis virus (RGNNV) (relative percentage survival, RPS: 100%), and specific antibodies against RGNNV were detected in sera from survivors.