RNase-dependent inhibition of extracellular, but not intracellular, dsRNA-induced interferon synthesis by Erns of pestiviruses

Abstract

Recombinant pestivirus envelope glycoprotein Erns has been shown to interfere with dsRNA-induced interferon (IFN-α/β) synthesis. This study demonstrated that authentic, enzymically active Erns produced in mammalian cells prevented a dsRNA-induced IFN response when present in the supernatant of bovine cells. Strikingly, IFN synthesis of cells expressing Erns was eliminated after extracellular addition, but not transfection, of dsRNA. Importantly, the same applied to cells infected with bovine viral diarrhea virus (BVDV) expressing Erns but lacking the N-terminal protease Npro. Free Erns concentrations circulating in the blood of animals persistently infected with BVDV were determined to be approximately 50 ng ml−1, i.e. at a similar order of magnitude as that displaying an effect on dsRNA-induced IFN expression in vitro. Whilst Npro blocks interferon regulatory factor-3-dependent IFN induction in infected cells, Erns may prevent constant IFN induction in uninfected cells by dsRNA that could originate from pestivirus-infected cells. This probably contributes to the survival of persistently BVDV-infected animals and maintains viral persistence in the host population.