Mechanism of selective inhibition of varicella zoster virus replication by 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil.

To investigate the mechanism of action of 1-beta-D-arabinofuranosyl-(E)-5-(2-bromovinyl)uracil (BV-araU) on varicella zoster virus (VZV) replication, we examined the metabolism of the drug in VZV-infected cells using 14C-labeled BV-araU. [14C]BV-araU was taken up by the cells infected with thymidine kinase-positive (TK+)VZV, but not so much by TK- VZV-infected or mock infected cells. Most of the radioactivity in TK+ VZV-infected cells that were incubated with [14C]BV-araU was recovered from their acid-soluble fraction, and little from their acid-insoluble fraction. By high performance liquid chromatographic assay of the acid-soluble fraction, it was proved that BV-araU was metabolized to its 5'-monophosphate, diphosphate, and triphosphate only in TK+ VZV-infected cells. The radioactivity was not detected in VZV nucleocapsids or in VZV DNA and cellular DNA isolated from TK+ VZV-infected cells, even if BV-araU was added at a 1000 times higher concentration than the 50% inhibitory dose for VZV replication in vitro. Furthermore, it was enzymatically proved that [14C]BV-araU was selectively and effectively phosphorylated to BV-araU monophosphate by VZV TK and that affinity of BV-araU triphosphate for VZV DNA polymerase was the quite strong. From these results, it can be concluded that marked inhibition of VZV replication by BV-araU is due to selective phosphorylation of BV-araU in the TK+ VZV-infected cells and strong inhibition of VZV DNA synthesis by BV-araU triphosphate, without detectable incorporation into VZV DNA.