Vol. 61, Issue 2, 249-254, February 2002

ACCELERATED COMMUNICATION
Specific Recognition of the Bicyclic Pyrimidine Nucleoside Analogs, a New Class of Highly Potent and Selective Inhibitors of Varicella-Zoster Virus (VZV), by the VZV-Encoded Thymidine Kinase

Rebecca Sienaert, Lieve Naesens, Andrea Brancale, Erik De Clercq, Christopher McGuigan, and Jan Balzarini

Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium (R.S., L.N., E.D.C., J.B.); and Welsh School of Pharmacy, Cardiff University, Cardiff, Wales, United Kingdom (A.B., C.M.G.)

Recently, an entirely new class of bicyclic nucleoside analogs (BCNAs) was found to display exquisite potency and selectivity as inhibitors of varicella-zoster virus (VZV) replication in cell culture. A striking difference in their ability to convert the BCNAs to their phosphorylated derivatives was observed between the VZV-encoded thymidine kinase (TK) and the very closely related herpes simplex virus type 1 (HSV-1) TK. Whereas VZV TK efficiently phosphorylated the BCNAs, HSV-1 TK was unable to do so. In addition, the thymidylate (dTMP) kinase activity of VZV TK further converted BCNA-5'-MP to BCNA-5'-DP. The BCNAs (or their phosphorylated derivatives) were not a substrate for cytosolic TK, mitochondrial TK, or cytosolic dTMP kinase. Human erythrocyte nucleoside diphosphate (NDP) kinase was unable to phosphorylate the BCNA 5'-diphosphates to BCNA 5'-triphosphates. Under the same experimental conditions, the anti-herpetic (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) derivative was efficiently converted to BVDU-MP and BVDU-DP by both VZV TK and HSV-1 TK and further, into BVDU-TP, by NDP kinase. Our observations may account for the unprecedented specificity of BCNAs as anti-VZV agents.