Required dose of fish nervous necrosis virus (NNV) for Poly(I:C) immunization of sevenband grouper Epinephelus septemfasciatus

• Published in: Aquaculture 2011-02, Vol.311 (1-4), p.100-104
• Main Authors: Nishizawa, Toyohiko, Takami, Ikuo, Yoshimizu, Mamoru, Oh, Myung-Joo
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Animal aquaculture; Animal diseases; Animal productions; Animal vaccines; antibodies; application methods; Aquaculture; Biological and medical sciences; dosage; dose response; double-stranded RNA; Epinephelus; Epinephelus septemfasciatus; Fish; fish diseases; Fundamental and applied biological sciences. Psychology; General aspects; Grouper; immersion (application method); immunity; Immunization; intramuscular injection; Live vaccine; live vaccines; Marine; marine fish; mortality; nervous system diseases; Nodaviridae; Poly(I:C) immunization; polyinosinic-polycytidylic acid; Red-spotted grouper nervous necrosis virus; vaccination; vaccine adjuvants; vertebrate viruses; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; viral diseases of animals and humans; Viral nervous necrosis; Viruses
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2010.12.009

It was recently reported that Poly(I:C) immunization of fish confers protection against viral infection. In this process, fish are immunized with a live pathogenic virus followed by administration of Poly(I:C), which induces a transient, non-specific antiviral state. As a result, fish survive the initial immunization with live virus, which would otherwise be lethal. In the present study, we tried to determine the exact dosage of red-spotted grouper nervous necrosis virus (RGNNV), the causative agent of viral nervous necrosis, required for Poly(I:C) immunization of sevenband grouper Epinephelus septemfasciatus. In Poly(I:C) immunization with more than 90% relative percentage survival (RPS) against RGNNV challenge with 104.3 TCID50/fish, approximately 104.0 TCID50/fish or greater of RGNNV was administered by intramuscular (IM) injection, whereas 105.3 TCID50/fish or greater of RGNNV was required for immersion methods. It was concluded that the degree of RGNNV infection must be similar to a fatal dose in order for the fish to become immune to RGNNV. Interestingly, antibody against RGNNV was not detected in the sera of fish immunized by immersion. Thus, Poly(I:C) immunization by immersion may have some interesting effects on the epidermal immune response in fish.