Analysis of phosphorylation pathways of antiherpesvirus nucleosides by varicella-zoster virus-specific enzymes

The inhibitory activities of acyclovir (ACV), 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl) uracil (BV-araU), ganciclovir (GCV), 9-(2-deoxy-2-hydroxJmethyl-beta-D-erythro-oxetanoxyl)guanine (OXT-G), and (+)-9-[(1R,2R,3S)-2,3-bis(hydroxymethyl)cyclobutyl] guanine (cOXT-G) on the replication of wild-type and thymidine kinase (TK)-negative strains of herpes simplex virus types 1 and 2 and varicella-zoster virus (VZV) and the wild-type strain of human cytomegalovirus were tested to clarify whether the phosphorylation of these compounds is catalyzed by viral TR or other enzymes, ACV and BV-araU had little effect on the replication of TK-negative virus strains, On the other hand, GCV, OXT-G, and cOXT-G inhibited the replication of TK-negative VZV at concentrations 10 times higher than those at which they inhibited wild-type VZV, indicating that a kinase other than TK phosphorylates GCV and OXT-G in VZV-infected cells, GCV phosphorylation activity was not detected in VZV-infected cell lysates; therefore, this activity was evaluated in COS I cells expressing viral TK and viral protein kinase (PK), The COS 1 cells expressing VZV TK were shown to be susceptible to all compounds tested. In contrast, VZV PK-expressing COS 1 cells were susceptible to only GCV, OXT-G, and cOXT-G. These results suggest that VZV PK phosphorylates some nucleoside analogs, for example, GCV, OXT-G, and cOXT-G, This phosphorylation pathway may be important in the anti-VZV activities of some nucleoside analogs.