Possible Involvement of Virus-Induced Protein Kinase in the Antiviral State Induced with Interferon-γ against Sindbis Virus

The kinetics of induction of the antiviral state against two RNA viruses, vesicular stomatitis virus (VSV) and Sindbis virus, by human interferons (IFNs)-alpha, -beta, and -gamma was measured and compared with that of 2',5'-oligoadenylate (2-5A) synthetase and protein kinase in cells treated with IFNs. Both enzymes were induced in similar time courses and the induction by IFN-gamma was slower than IFN-alpha or beta. The time course of the induction of antiviral state against VSV almost paralleled with that of the enzyme induction by each IFN species. In contrast, the induction of antiviral state against Sindbis virus with IFN-gamma was as fast as that induced with IFN-alpha or beta, in spite of the slower enzyme induction by IFN-gamma. The addition of actinomycin D at the time of virus challenge did not substantially affect the induction of the antiviral state against VSV, but markedly retarded the establishment of IFN-gamma-induced antiviral state against Sindbis virus. These results suggest that the antiviral machinery against VSV is induced solely by IFN during the pretreatment, but the one against Sindbis virus involves additional cellular component(s) induced shortly after virus infection, especially in the case of IFN-gamma. Sindbis virus, but not VSV, induced a cellular double-stranded (ds) RNA-dependent protein kinase at an early stage of virus replication. The kinase appeared to phosphorylate the same protein as IFN-induced kinase in the IFN-gamma-treated and Sindbis virus-infected cells, leading to an increased phosphorylation level. These results are consistent with the idea that the Sindbis virus-induced protein kinase may be involved in the IFN-gamma-induced antiviral state against Sindbis virus.