Differential effect of murine alpha/beta interferon transgenes on antagonization of herpes simplex virus type 1 replication

Alpha/beta interferons (IFN-alpha/beta) are potent, endogenous antiviral cytokines that suppress the replication of RNA and DNA viruses, including herpes simplex virus type 1 (HSV-1). The present study compared the efficacies of IFN-alpha/beta transgenes, including IFN-alpha1, -alpha4, -alpha5, -alpha6, -alpha9, and -beta, against HSV-1 infection. L929 cells transfected with the IFN-alpha/beta transgenes produced similar levels of IFN, as measured by bioassay and enzyme-linked immunosorbent assay. In addition, transfected cells were less susceptible to HSV-1 infection than were cells transfected with a plasmid vector control. The murine IFN-beta plasmid construct exhibited the greatest reduction, while the murine IFN-alpha5 transgene showed a modest inhibitory effect in viral titers recovered from the supernatants of transfected, infected L929 cultures. Consistent with this observation, the IFN-beta transgene antagonized viral transcript levels, including infected cell protein 27, thymidine kinase, and glycoprotein B, to a greater extent than did the IFN-alpha transgenes at 6 to 10 h postinfection as determined by real-time PCR. Cells transfected with the IFN-alpha4, IFN-alpha9, or IFN-beta transgenes showed the greatest reduction in viral protein expression relative to the other transfected cells, which was associated with increased STAT1 expression. The absence of the IFN-responsive protein kinase R (PKR) gene completely abrogated the antiviral induction by all IFN-alpha/beta against HSV-1. In the absence of RNase L, viral yields were increased 10-fold, but the antiviral effect of IFN was either unaffected or enhanced. These results suggest that the predominant IFN-mediated, antiviral pathway during HSV-1 infection taken by IFN-alpha/beta in L929 cells utilizes PKR.