title: Stability and efficacy of the 3'-UTR A4G-G5A variant of viral hemorrhagic septicemia virus (VHSV) as a live attenuated immersion VHSV vaccine in olive flounder (Paralichthys olivaceus).
abstract: Viral hemorrhagic septicemia virus (VHSV) is the causative agent of viral hemorrhagic septicemia in fish, a disease that affects a number of teleost fish species including olive flounder (Paralichthys olivaceus). In this study, we assessed the safety and efficacy of two recombinant attenuated VHSV strains, termed A4G-G5A and ΔNV, with the purpose to select the most suitable vaccine strain. The virus strains were passaged in two commercially available cell lines, EPC and RTG-2, and the strains were also tested for residual virulence in zebrafish (Danio rerio). The A4G-G5A strain showed an attenuated growth profile in both the EPC and RTG-2 cell lines compared to wild-type (WT) VHSV (JF-09, genotype IVa), whereas the growth profile of ΔNV was comparable to the WT strains in RTG-2 cells in contrast to EPC cells. Moreover, ΔNV had higher residual virulence compared to A4G-G5A and was highly pathogenic to zebrafish. The A4G-G5A strain was chosen as vaccine candidate and tested for efficacy in in vivo fish studies in the target species, olive flounder, using an immersion vaccine scheme. Groups of fish were immunized with 10(2.5), 10(3.5), 10(4.5), and 10(5.5) TCID50/ml of A4G-G5A giving 5-13.3 cumulative percent mortality (CPM) post immunization. Immunization was followed by a challenge experiment using VHSV-WT. The relative percent survival (RPS) in immunized groups ranged from 81.6% to 100%, correlating with vaccination dose. This study demonstrates that while strain A4G-G5A has retained some residual virulence it confers high level of protection in immunized olive flounder.
authors.affiliation: Norwegian University of Life Sciences, P.O. Box 8146 Dep, N-0033 Oslo, Norway.
authors.forename: Sung-Hyun
authors.initials: SH
authors.lastname: Kim
authors.affiliation: BluGen Korea, 106-14, Songjeongjungang-ro 5 beon-gil, Busan, Republic of Korea.
authors.forename: Meesun
authors.initials: M
authors.lastname: Kim
authors.affiliation: BluGen Korea, 106-14, Songjeongjungang-ro 5 beon-gil, Busan, Republic of Korea.
authors.forename: Go-Eun
authors.initials: GE
authors.lastname: Choi
authors.affiliation: Fish Breeding Center, NIFS, Busan, Republic of Korea.
authors.forename: Jeong Ho
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Biotechnology Research Division, NIFS, Busan, Republic of Korea.
authors.forename: Jung-Ha
authors.initials: JH
authors.lastname: Kang
authors.affiliation: Norwegian University of Life Sciences, P.O. Box 8146 Dep, N-0033 Oslo, Norway.
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Evensen
authors.affiliation: BluGen Korea, 106-14, Songjeongjungang-ro 5 beon-gil, Busan, Republic of Korea. Electronic address: woojailee@blugen-sol.com.
authors.forename: Woo-Jai
authors.initials: WJ
authors.lastname: Lee
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D002460:Cell Line; D005393:Fish Diseases / Q000517:prevention & control* / Q000821:virology; D005432:Flounder; D031941:Hemorrhagic Septicemia, Viral / Q000517:prevention & control*; D009500:Neutralization Tests; D029141:Novirhabdovirus / Q000235:genetics / Q000472:pathogenicity; D014613:Vaccines, Attenuated / Q000276:immunology; D014765:Viral Vaccines / Q000276:immunology*; D014774:Virulence; D015027:Zebrafish
chemical_list: D020413:3' Untranslated Regions; D057134:Antibodies, Neutralizing; D014613:Vaccines, Attenuated; D014765:Viral Vaccines
keywords: Attenuated vaccine; Olive flounder; VHSV