Interferon inhibits dengue virus infection by preventing translation of viral RNA through a PKR-independent mechanism

Previously, we demonstrated that pretreatment of cells with interferon (IFN ) alpha + gamma or beta + gamma inhibited dengue virus (DV) replication. In this study, experiments were per-formed to better define the mechanism by which IFN blocks the accumulation of dengue virus (DV) RNA. Pretreatment of human hepatoma cells with IFN beta + gamma did not significantly alter vir us attachment, viral entry, or nucleocapsid penetration into the cytoplasm. The inhibitory effect of IFN was retained even when naked DV RNA was trans fected directly into cells, confirming that steps associated with viral ent ry were not the primary target of IFN action. Biosynthetic labeling experim ents revealed that IFN abolished the translation of Infectious viral RNA th at occurred prior to RNA replication. Subcellular fractionation experiments demonstrated that IFN did not significantly alter the ability of viral RNA to attach to ribosomes. The antiviral effect of IFN appeared independent o f the IFN-Induced, double-stranded RNA-activated protein kinase (PKR) and R Nase L, as genetically deficient PKR- RNase L- cells that were infected by DV retained sensitivity to Inhibition by IFN.. We conclude that IFN prevent s DV infection by inhibiting translation of the Infectious viral RNA throug h a novel, PKR-independent mechanism. (C) 2001 Academic Press.