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

Abstract

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. The antiviral state was induced by administration of Poly(I:C) doses ranging from 12.5 to 200 µg fish(-1). Minimum dose to induce the antiviral state (relative percentage survival, RPS: 90%) was 12.5 µg fish(-1). No curative effect of Poly(I:C) was observed in fish pre-infected with VHSV. Fish injected with 200 µg Poly(I:C) fish(-1) were highly protected (RPS: 100%) from an artificial challenge with VHSV, and specific antibodies against VHSV were detected. The corresponding high level of antiviral state against VHSV was attained 1 d post Poly(I:C) injection, lasted for 6 d and susequently decreased. Moreover, the surviving fish were highly protected from re-challenge with VHSV (RPS: 100%). Thus, it was considered that an immunity against viral hemorrhagic septicemia was induced in the Japanese flounder by injecting live VHSV following Poly(I:C) administration

Length-dependent innate antiviral effects of double-stranded RNA in the rainbow trout (Oncorhynchus mykiss) cell line, RTG-2

“…The antiviral state inhibits the replication of DNA and RNA viruses [37]. This has been observed in both in vitro and in vivo studies in mammals and fish [18,37,41]. Poly I:C can induce an antiviral state in both fish and fish cell lines.…”

Cell Culture Medium Inhibits Antigen Binding Used in an ELISA for Detection of Antibodies against Nervous Necrosis Virus

“…Several studies using ELISA systems for the detection of specific fish antibodies have been reported for aquatic animals (Jorgensen et al 1991;Yoshimizu et al 1992;Dixon et al 1994;Pilström 1994, 1995;LaPatra 1996;Nishida et al 1998;Watanabe et al 1998;Swain and Nayak 2003;Okuda et al 2006;Kim et al 2007Kim et al , 2008Kim et al , 2009Takami et al 2010). However, use of an ELISA for fish antibody detection can be problematic because of difficulties such as low reproducibility, which is partly due to high background optical density (OD) caused by nonspecific reactions between fish antibodies and antigens Pilström 1994, 1995;Knopf et al 2000;Kibenge et al 2002;Guo and Woo 2004).…”

Assessment of the sevenband grouper Epinephelus septemfasciatus with a live nervous necrosis virus (NNV) vaccine at natural seawater temperature

“…Unfortunately, almost no live virus vaccines for fish have been investigated, except our previous studies [17][18][19][20][21][22][23][24]; one of the reasons could be due to the possibility of viral spread from vaccinated fish into the aquaculture environment. Thus, we investigated the possibility of horizontal infection from fish with the live NNV vaccine to naïve fish by cohabitation.…”

“…Moreover, surviving fish can mount a protective immune response against NNV [21]. It is conceivable that these live vaccine concepts will eventually be applicable to a wide range of fish species as well as other viruses [22][23][24].…”