Specific nucleotides at the 3′-terminal promoter of viral hemorrhagic septicemia virus are important for virulence in vitro and in vivo

• Published in: Virology (New York, N.Y.) Vol. 476; pp. 226 - 232
• Main Authors: Kim, Sung-Hyun, Guo, Tz-Chun, Vakharia, Vikram N, Evensen, Øystein
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-02-2015
• Subjects: 3' Untranslated Regions; 3′-UTR; Animals; Base Sequence; Danio rerio; Female; Fish Diseases - virology; Gene Expression Regulation, Viral; In vitro; In vivo; Infectious Disease; Male; Molecular Sequence Data; Novirhabdovirus; Novirhabdovirus - genetics; Novirhabdovirus - metabolism; Novirhabdovirus - pathogenicity; Promoter function; Promoter Regions, Genetic; Rhabdoviridae Infections - veterinary; Rhabdoviridae Infections - virology; VHSV; Viral hemorrhagic septicemia virus; Virulence; Zebrafish; Promoter function; In vivo; Virulence; 3′-UTR; Novirhabdovirus; VHSV; In vitro
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/j.virol.2014.12.003

Abstract Viral hemorrhagic septicemia virus (VHSV), a member of the Novirhabdovirus genus, contains an 11-nucleotide conserved sequence at the terminal 3′- and 5′-untranslated regions (UTRs) that are complementary. To study the importance of nucleotides in the 3′-UTR of VHSV for replication of novirhabdoviruses, we performed site-directed mutagenesis of selected residues at the 3′-terminus and generated mutant viruses using a reverse genetics approach. Assessment of growth kinetics and in vitro real-time cytopathogenicity studies showed that the order of two nucleotides (A4G5) of the 3′-terminus of VHSV directly affects growth kinetics in vitro. The mutant A4G-G5A virus has reduced total positive-strand RNA synthesis efficiency (51% of wild-type) at 48 h post-transfection and 70 h delay in causing complete cytopathic effect in susceptible fish cells, as compared to the WT-VHSV. Furthermore, when the A4G-G5A virus was used to challenge zebrafish, it exhibited reduced pathogenicity (54% lower end-point mortality) compared to the WT-VHSV. From these studies, we infer that specific residues in the 3′-UTR of VHSV have a promoter function and are essential to modulate the virulence in cells and pathogenicity in fish.