Aquabirnavirus-induced Protection of Marine Fish against Piscine Nodavirus Infection

Abstract

ABSTRACT--Experimental dual-infections with a non-lethal aquabirnavirus (ABV) and a lethal betanodavirus (redspotted grouper nervous necrosis virus: RGNNV) were carried out in Japanese flounder Paralichthys olivaceus and sevenband grouper Epinephelus septemfasciatus.In the dual-infection group, ABV was intramuscularly (IM) injected into fish seven days before the IM-injec tion with RGNNV. In the experiments with flounder, a high expression of an Mx gene, a molecular marker for type I interferon(s) (IFN) production, occurred in the head kidneys and brains at Day 7 post-ABV injection. Although no mortality was found not only in the dual-infected group but also in the single infection group with RGNNV (control group), the infective titers of RGNNV in the tissues of the dual-infected group were significantly lower at any sampling times than those in the control group. In the experiments with grouper, the preceding ABV infection resulted in complete protec tion against RGNNV infection. The infective titers of RGNNV in the tissues were also lower in the dual-infected group than in the control group throughout the experiments, and finally the virus dis appeared from the head kidneys and brains of the dual-infected group at Day 14 and Day 56 post injections, respectively. These results suggest that an ABV-induced IFN(s) effectively suppresses the progression of secondary betanodavirus infection.

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

“…These results were consistent with those observed in rainbow trout with Poly(I:C) injection and IHNV challenge (Kim et al 2008). Also, Japanese flounder and sevenband grouper pre-infected with ABV were protected from VHSV and/or RGNNV infection, and in that study it was confirmed that fish Mx gene, an indicator of IFN, was expressed after the ABV injection (Pakingking et al 2004(Pakingking et al , 2005. Kim et al (2009) demonstrated that an antiviral state was established by injecting rainbow trout with Poly(I:C), as a substitute for IPNV.…”

“…Furthermore, primary infection with ABV in Japanese flounder and sevenband grouper Epinephelus septemfasciatus involved protection of fish from other pathogenic viruses, such as VHSV and fish nodavirus (Pakingking et al 2003(Pakingking et al , 2005. It was also reported that protection from VHSV and infectious hematopoietic necrosis virus (IHNV) was induced in rainbow trout Oncorhynchus mykiss by pre-exposure to infectious pancreatic necrosis virus (IPNV), aquareovirus or a picornavirus (de Kinkelin et al 1992, Hedrick et al 1994, La Patra et al 1995, Byrne et al 2008.…”

Study of the viral interference between infectious pancreatic necrosis virus (IPNV) and infectious haematopoietic necrosis virus (IHNV) in rainbow trout (Oncorhynchus mykiss)

“…An anti-VHSV activity was also demonstrated in the serum of Japanese flounder infected by an aquatic Birnavirus (ABV) and a high expression of a Mx gene, a molecular marker of type I interferon occurred in the head kidneys of the ABV-challenged flounder suggesting IFN activity [20]. It was also shown that ABV induced IFN activity against a secondary Betanodavirus infection [17].…”

“…The primary infection of Salmonids by an Aquabirnavirus, a Picornavirus or an Aquareovirus involves a protection of fish to other viruses such as viral haemorrhagic septicaemia virus (VHSV), IHNV [14e16] or Nodavirus [17]. This protection, transient or partial, has been shown both in vivo and in vitro [11,13,18].…”

Protection of rainbow trout from infectious hematopoietic necrosis (IHN) by injection of infectious pancreatic necrosis virus (IPNV) or Poly(I:C)

“…Furthermore, in marine fishes, primary infection of Japanese flounder and sevenband grouper Epinephelus septemfasciatus by aquabirnavirus confers protection from other pathogenic viruses, such as VHSV and fish nodavirus (Pakingking et al 2003(Pakingking et al , 2005. The protection from the secondary infection of virus was due to an interferon (IFN) activity induced in the fish by the primary infection (Pakingking et al 2004, Das et al 2007, McBeath et al 2007).…”