DEWITTE-ORR, S.J.*; BOLS, N.C.; University of Waterloo, Waterloo, Ontario; University of Waterloo, Waterloo, Ontario: Expression of Antiviral Genes in Different Rainbow Trout Cell Lines
Six antiviral genes whose expression is regulated by type 1 interferon were investigated by RT-PCR in several rainbow trout cell lines after exposure to polyinosinic:cytidylic acid (poly IC). Poly IC is a synthetic double-stranded RNA known to induce type 1 interferon production and antiviral mechanisms. The cell lines considered in this study were the monocyte/macrophage cell line, RTS11 and epithelial cell lines from the gill, RTgill-W1, liver, RTL-W1, and early embryo, RTEE. The genes were Mx1, Mx2, and Mx3, IRF-1, vig-1 and vig-2. The Mx proteins are guanosine triphosphate (GTP)-binding proteins with intrinsic GTPase activity that are involved in the first line of defense against viral infections. IRF-1 is a nuclear factor that is involved in the activation of interferon-induced gene expression. The specific antiviral activity of vig-1 and vig-2 proteins is yet to be defined. The presence of IRF-1, vig-1 and vig-2 mRNA was detected in both control and poly IC (50 µg/ml) treated cultures for all cell lines tested. Mx1 mRNA was only detected in cultures treated with poly IC for 24 h. This was true for all four cell lines tested. For RTS11 and RTEE, Mx2 and Mx3 mRNA was not detected in control cultures but was induced after poly IC treatment. However, RTL-W1 and RTgill-W1 expressed Mx2 and Mx3 mRNA transcripts with or without poly IC exposure. Thus, Mx1 was the only mRNA transcript that was upregulated in all cell lines in response to poly IC. These results suggest that Mx1 appears to be the most specific marker of antiviral activity at the transcription level of the six genes tested. We are currently investigating the effects of temperature on changes in antiviral gene transcription in response to poly IC.
