title: Protection of rainbow trout from infectious hematopoietic necrosis (IHN) by injection of infectious pancreatic necrosis virus (IPNV) or poly(I:C).
abstract: It was recently reported that prophylaxis against infectious hematopoietic necrosis virus (IHNV) in fish was induced by pre-exposure to the infectious pancreatic necrosis virus (IPNV). Here the establishment of IHNV immunity in rainbow trout Oncorhynchus mykiss was investigated by IHNV challenge following non-lethal pre-infection with IPNV. Also, synthetic double-stranded RNA polyinosinic polycytidylic acid, Poly(I:C), an inducer for interferon (IFN), was evaluated as a substitute for IPNV induction of the non-specific antiviral state and subsequent IHNV-specific immunity in fish. Rainbow trout pre-infected with IPNV were protected from IHNV challenge 7 d later (relative percentage survival, RPS: 68.8%), and IHNV-specific antibodies were detected in sera from the survivors. Moreover, these surviving fish showed 91.6% RPS when re-challenged with IHNV 28 d after the primary IHNV challenge. Thus, fish appear to acquire IHNV-specific immunity through the IHNV challenge following pre-injection with IPNV. Fish pre-injected with Poly(I:C) were also highly protected from IHNV challenge 2 d later (RPS: 95.2%), and IHNV-specific antibodies were also detected amongst survivors. The survivors showed a 100% survival rate following re-challenge with IHNV both 21 and 49 d after the primary IHNV challenge. Thus, IHNV immunity in rainbow trout is induced by challenge with live IHNV following pre-injection with either IPNV or Poly(I:C). The use of Poly(I:C) to induce an anti-viral state protecting rainbow trout from an otherwise lethal vaccination dose of IHNV may have application to a wider range of fish species and fish pathogenic viruses.
authors.affiliation: Faculty of Fisheries Sciences, Hokkaido University, Hakodate 041-0811, Japan.
authors.forename: Hyoung Jun
authors.initials: HJ
authors.lastname: Kim
authors.forename: Norihisa
authors.initials: N
authors.lastname: Oseko
authors.forename: Toyohiko
authors.initials: T
authors.lastname: Nishizawa
authors.forename: Mamoru
authors.initials: M
authors.lastname: Yoshimizu