title: Antiviral activity of arabinosylthymine in herpesviral replication: mechanism of action in vivo and in vitro.
abstract: 1-beta-d-Arabinofuranosylthymine (ara-T), a metabolite of the sponge Tethya crypta, has shown selective activity against herpes simplex virus (HSV) replication (G. A. Gentry and J. F. Aswell, Virology 65:294-296, 1975). Analysis of HSV-infected and uninfected cell lysates by CsCl isopycnic centrifugation showed that ara-T blocked the incorporation of [(3)H]hypoxanthine into viral deoxyribonucleic acid and, to a large extent, into host deoxyribonucleic acid of infected (but not uninfected) cells. Additional experiments with [gamma-(32)P]adenosine 5'-triphosphate as a radiophosphate donor demonstrated that ara-T is phosphorylated by extracts of HSV-infected BHK cells and not by those of uninfected cells. At an ara-T concentration that almost completely inhibited the growth of LM cells, which had been transformed to a pyrimidine deoxyribonucleoside kinase(+) (dPyK(+)) phenotype by ultraviolet-inactivated HSV-1, the growth of uninfected LM cells was not affected. These results indicate that the viral dPyK is responsible for the selective antiviral activity of ara-T. This conclusion was further supported by experiments that showed that the replication of a variety of dPyK(-) mutants of HSV-1 and HSV-2 were not affected by ara-T and that ara-T inhibited the phosphorylation of deoxycytidine and deoxythymidine by HSV-1 dPyK, but not by host deoxycytidine and deoxythymidine kinases, respectively. Ara-T also selectively inhibited the replication of equine herpesvirus type 1 (EHV-1) in vitro and was effective against EHV-1 infection in vivo in hamsters. Further, EHV-1 was inhibited by ara-T and by bromodeoxyuridine in LM cells lacking a cytosol thymidine kinase, suggesting that EHV-1 induces a dPyK. Finally, spectrophotometric assay for thymine suggested that ara-T is not a substrate for nucleoside phosphorylase of hamster liver, and a microbiological assay indicated that substantial amounts of ara-T were excreted in the urine of uninfected hamsters that had received a single injection of 5 mg of ara-T, the amount given in each injection in the in vivo experiments with EHV-1.
mesh_terms: D000818:Animals; D000998:Antiviral Agents; D001089:Arabinose / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D006224:Cricetinae; D004247:DNA / Q000096:biosynthesis; D004279:DNA, Viral / Q000096:biosynthesis; D006564:Herpesviridae / Q000187:drug effects* / Q000378:metabolism; D006566:Herpesviridae Infections / Q000503:physiopathology; D004861:Herpesvirus 1, Equid / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D010770:Phosphotransferases / Q000378:metabolism; D018139:Simplexvirus / Q000187:drug effects; D013936:Thymidine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D013937:Thymidine Kinase / Q000378:metabolism; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D000998:Antiviral Agents; D004279:DNA, Viral; D004247:DNA; D001089:Arabinose; D010770:Phosphotransferases; D013937:Thymidine Kinase; D013936:Thymidine