Examining rainbow trout vig-3 expression patterns in vitro following treatment with type I IFN, poly IC or viral infection

Abstract

Interferon-stimulated genes (ISGs) are key mediators of antiviral immunity. Investigating ISGs can help create novel therapeutics to increase survival rates of farmed fish and aid in protection against pathogens. The current study investigated the induction of one such ISG, viral hemorrhagic septicemia (VHSV) – induced gene 3 (vig-3), also known as ISG15 in mammals and other fish species. Vig-3 is one of many rainbow trout ISGs whose expression patterns, induction, and role remain relatively unknown. In this study, vig-3 transcript expression was identified in a panel of tissues from healthy rainbow trout. Vig-3 transcripts were upregulated in response to recombinant type I interferon (IFN-I) treatment in rainbow trout gonadal cells (RTG-2). Vig-3 transcript and protein levels were upregulated overtime following treatment with a double-stranded (ds)RNA molecule, polyinosinic: polycytidylic acid (poly IC), and infection with two viruses, infectious pancreatic necrosis virus (IPNV) and viral hemorrhagic septicemia virus (VHSV) in two rainbow trout cell lines, RTG-2 and RTgill-W1. Vig-3 transcript expression kinetics positively corelated with viral replication kinetics. Western blot analysis demonstrated evidence of protein ISGylation, a unique feature of vig-3. Vig-3′s cellular localization was assessed using immunocytochemistry following viral infection. Vig-3 expression was cytoplasmic and increased in quantity over time, upon treatment with poly IC, or infection with IPNV or VHSV. These findings improve our understanding of the rainbow trout innate immune system and could aid in the production of fish antiviral therapeutics in the future.

Keywords

• Interferon stimulated gene
• Innate immunity
• Viral hemorrhagic septicemia virus (vhsv)- induced gene 3
• Dsrna
• Virus
• Infectious pancreatic necrosis virus (IPNV)