Interferon-induced transmembrane protein 1 (IFITM1) inhibits Varicella-Zoster Virus Replication

Hosts have evolved numerous mechanisms to prevent primary viral infections. Interferon signaling is an important host defense mechanism against primary infection. Interferon gamma (IFN-γ) is a potent cytokine produced following primary varicella-zoster virus (VZV) infection. Furthermore, VZV reactivation correlates with a decline in IFN-γ-producing immune cells. Our previous results showed that pretreatment with 20 ng/ml of IFN-γ completely inhibited VZV replication in lung fibroblast MRC-5 and retinal epithelial ARPE-19, suggesting that IFN-γ-stimulated protein(s) inhibit viral replication. Our microarray analysis revealed that a small subset of interferon-stimulated genes (ISGs) was upregulated by greater than 3.5-fold at 8 h post-treatment in both ARPE-19 and MRC-5 cells compared to those of melanoma MeWo cells. The depletion of IFITM1 and IRF1 by siRNA in IFN-γ-treated cells significantly increased (from 0 to ~1x103 pfu/105 cells) VZV yields. In contrast, the depletion of a nontargeting control (siNTC) did not increase virus yield. Ectopic expression of interferon-induced transmembrane protein 1 (IFITM1) reduced the level of IE62 protein as well as intracellular VZV yield in both ARPE-19 and MeWo cells, but did not reduce the expression level of IE62 mRNA, suggesting that IFITM1 expression reduces the expression level of IE62 by post-transcriptional regulation. IFITM1 also reduced the expression levels of VZV IE62, HSV-1 ICP4, and EHV-1 IEP in ARPE-19 cells Human retinal epithelial ARPE-19, human lung fibroblast MRC-5, and human melanoma MeWo cells were treated with 0 or 20 ng/ml of human IFN-γ (Cell Sciences, Canton, MA). The untreated and treated cells were harvested at 8 h post-treatment and used in DNA microarray analyses using the Affymetrix human Genome U133 Plus 2.0 array (Affymetrix, Santa Clara, CA).