title: Genetically similar VHSV isolates are differentially virulent in olive flounder Paralichthys olivaceus.
abstract: Two viral hemorrhagic septicemia virus (VHSV) isolates, VHSV-KR-CJA and VHSV-KR-YGH, were isolated from viral hemorrhagic septicemia disease outbreaks in flounder farms in South Korea. The VHSV-KR-CJA isolate was isolated from a flounder farm with high mortality (80%), while the VHSV-KR-YGH isolate was isolated from a flounder farm with low mortality (15%), suggesting that these isolates differ in virulence. The virulence of these isolates was evaluated in juvenile flounder via intraperitoneal injection. Consistent with their virulence in the field, mortality data revealed that the VHSV-KR-CJA isolate was highly pathogenic (cumulative mortality of 80%), while the VHSV-KR-YGH isolate was less pathogenic in flounder (cumulative mortality of 20%). To characterize the genotypes of these viruses, the full open reading frames (ORFs) encoding nucleoprotein N, phosphoprotein P, matrix protein M, glycoprotein G, nonstructural viral protein NV, and polymerase L of these viruses were sequenced and analyzed. Sequence analysis revealed that both isolates are genetically very similar (identical amino acid sequences for P, M, NV, and L and >99.7 and 99.8% amino acid sequence identity for N and G, respectively). Phylogenetic analysis indicated that both of these viruses belong to the Genotype IVa group, suggesting that they originated from a common ancestral virus. The low pathogenicity VHSV strain may potentially evolve to become a more pathogenic strain through only a few nucleotide substitutions. Further functional analyses of mutations in VHSV genes are necessary to identify factors that determine VHSV pathogenicity in flounder.
authors.affiliation: Aquatic Life Disease Control Division, National Fisheries Research and Development Institute, Busan 619-705, South Korea.
authors.forename: Mi Young
authors.initials: MY
authors.lastname: Cho
authors.forename: Unn Hwa
authors.initials: UH
authors.lastname: Lee
authors.forename: Chang Hoon
authors.initials: CH
authors.lastname: Moon
authors.forename: Jong Deuk
authors.initials: JD
authors.lastname: Bang
authors.forename: Bo Young
authors.initials: BY
authors.lastname: Jee
authors.forename: Seung Ju
authors.initials: SJ
authors.lastname: Cha
authors.forename: Jin Woo
authors.initials: JW
authors.lastname: Kim
authors.forename: Myoung Ae
authors.initials: MA
authors.lastname: Park
authors.forename: Jeong Wan
authors.initials: JW
authors.lastname: Do
authors.forename: Jeong Woo
authors.initials: JW
authors.lastname: Park
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D018076:DNA, Complementary; D005393:Fish Diseases / Q000401:mortality / Q000821:virology*; D005432:Flounder; D031941:Hemorrhagic Septicemia, Viral / Q000401:mortality / Q000821:virology*; D029141:Novirhabdovirus / Q000235:genetics* / Q000472:pathogenicity; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D012367:RNA, Viral / Q000235:genetics; D013997:Time Factors; D014774:Virulence
chemical_list: D018076:DNA, Complementary; D012367:RNA, Viral