DAO 45:33-44 (2001)  -  doi:10.3354/dao045033

Immune response to a recombinant capsid protein of striped jack nervous necrosis virus (SJNNV) in turbot Scophthalmus maximus and Atlantic halibut Hippoglossus hippoglossus, and evaluation of a vaccine against SJNNV

Súsanna Húsgar71,*, Sindre Grotmol1, Brit K. Hjeltnes1, Odd Magne Rødseth2, Eirik Biering2

1Institute of Marine Research, Department of Aquaculture, PO Box 1870, 5817 Bergen-Nordnes, Norway
2Intervet Norbio AS, Thormøhlensgt. 55, 5008 Bergen, Norway

ABSTRACT: Immunisation by intraperitoneal injection of an oil-emulgated recombinant partial capsid protein (rT2) from striped jack nervous necrosis virus (SJNNV) was performed on adult turbot Scophthalmus maximus and Atlantic halibut Hippoglossus hippoglossus. A specific humoral immune response was recorded in both species, and the levels of rT2-specific antibodies increased markedly in all groups during the 20 wk experiment. A challenge model for SJNNV was established by intramuscular injection of juvenile turbot. The turbot developed viral encephalopathy and retinopathy (VER), also known as viral nervous necrosis (VNN), with cumulative mortality in the range of 25 to 66%, after intramuscular inoculation with SJNNV propagated in the striped snake head cell line (SSN-1). Although neither clinical signs nor mortality were registered, SJNNV was neuroinvasive after bath exposure. The infection after both modes of challenge was verified by means of immunohistochemistry and RT-PCR, and SJNNV was reisolated in cell culture. The results indicate that SJNNV may have entered the central nervous system (CNS) by axonal transport through motor nerves after intramuscular inoculation. A vaccine efficacy test was performed on juvenile turbot, employing oil emulsified rT2 as a test vaccine and intramuscular inoculation of SJNNV. Significant protection was observed when the challenge was performed 10 wk post-vaccination.

KEY WORDS: Viral encephalopathy and retinopathy (VER) · Nodavirus · Challenge model · Recombinant vaccine · Turbot · Atlantic halibut

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