Generation of recombinant viral hemorrhagic septicemia viruses (VHSVs) harboring G gene of hirame rhabdovirus (HIRRV) and their ability to induce serum neutralization activity in olive flounder (Paralichthys olivaceus)

Recently, we have reported the rescue of a recombinant viral hemorrhagic septicemia virus (VHSV) that has enhanced green fluorescent protein (EGFP) gene ORF instead of NV gene ORF (rVHSV-ΔNV-EGFP), and demonstrated that intramuscular injection or oral administration of the recombinant VHSV induced high protection against wild-type VHSV challenge in olive flounder (Paralichthys olivaceus). In the present study, we have firstly generated two types of recombinant VHSV chimeras; one has hirame rhabdovirus (HIRRV) G gene instead of VHSV G gene (rVHSV-HG-ΔNV-EGFP), the other harbors both HIRRV G and VHSV G genes (rVHSV-HG-VG-ΔNV-EGFP), and analyzed their ability to induce serum neutralization activity against VHSV and HIRRV. The neutralization activity against each virus (HIRRV and VHSV) was dependent on the presence of the corresponding G gene in the genome, supporting that G protein is the major antigen to induce neutralizing antibodies against rhabdoviruses. Induction of high neutralization activity against both VHSV and HIRRV by immunization with rVHSV-HG-VG-ΔNV-EGFP suggests that recombinant VHSVs might be expected to be used as combined vaccines in fish.

► Recombinant VHSVs harboring HIRRV G gene were rescued by reverse genetics.
► rVHSVs immunization induced G gene-specific neutralization against VHSV and HIRRV.
► rVHSV with both VHSV and HIRRV G genes showed the strongest neutralization activity.