Roscovitine, a Cyclin-Dependent Kinase Inhibitor, Prevents Replication of Varicella-Zoster Virus

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Abstract
Understanding the interactions between varicella-zoster virus (VZV) and host cells can be addressed by using small molecule inhibitors of cellular enzymes. Roscovitine (Rosco) is a purine derivative that inhibits cyclin-dependent kinase 1 (cdk1), cdk2, cdk5, cdk7, and cdk9, which are key regulators of the cell cycle and transcription. Herpesviruses are known to interact with cell cycle proteins; thus, the antiviral effects of Rosco on VZV growth were evaluated. In a plaque reduction assay, 25 μM Rosco prevented VZV replication, and the antiviral effect was reversible for at least up to 24 h posttreatment. Rosco also reduced expression of the major transactivator, IE62, over 48 h. Confocal microscopy studies indicated that Rosco caused the immediate-early proteins ORF4 and IE62 to abnormally localize in infected cells and prevented cell-cell spread of VZV over 48 h. Rosco was found to inhibit VZV DNA synthesis as measured by real-time PCR, and this technique was used to estimate the 50% effective concentration (EC 50 ) of 14 μM. This value was close to the EC 50 estimate of 12 μM determined from plaque reduction assays. At 25 μM, Rosco was not cytotoxic over 48 h in a neutral red uptake assay, and proliferation was slowed as the cells accumulated in a G 2 -like state. These results demonstrate the importance of cdk's in VZV replication and suggest that cdk inhibitors could serve as useful VZV antivirals.

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