Induction of Mx protein by interferon and double-stranded RNA in salmonid cells

Summary

Mr protein is one of several antiviral proteins that are induced by the type I interferons (IFN), IFN alpha and beta, in mammals. In this work induction of a 76 kDa Mr protein by double-stranded RNA (dsRNA) or type I IFN-like activity in Atlantic salmon macrophages, Atlantic salmon fibroblast cells (AS cells) and in Chinook salmon embryo cells (CHSE-214) is reported. Type I IFN-like activity was produced by the stimulation of Atlantic salmon macrophages with the synthetic dsRNA polyinosinic polycytidylic acid (poly I:C). A correlation appeared to exist between Mr protein expression and protection against infectious pancreatic necrosis virus (IPNV) induced by IFN in CHSE-214 cells. Several observations in the present work suggest that, as in mammals, the induction of Mr protein by dsRNA in fish cells primarily occurs via induction of type I IFN. First, type I IFN-like activity but not poly I:C, induced Mx protein expression in CHSE-214 cells. These cells apparently lack the ability to produce IFN in response to poly I:C. Second, the putative IFN induced maximal Mr protein expression 48 h earlier than poly I:C in AS cells. Third, the peak expression of Mr protein in macrophages induced by poly I:C occurred after 48 h whereas peak in IFN-like activity was observed by 24 h after addition of poly I:C. The present work supports the notion of using Mr protein as a molecular marker for the production of putative type I IFN in fish. (C) 2000 Academic Press.