title: Potent antiviral activity of north-methanocarbathymidine against Kaposi's sarcoma-associated herpesvirus.
abstract: Kaposi's sarcoma-associated herpesvirus (KSHV) infection is a prerequisite for the development of Kaposi's sarcoma (KS). Blocking lytic KSHV replication may hinder KS tumorigenesis. Here, we report potent in vitro anti-KSHV activity of 2'-exo-methanocarbathymidine [North-methanocarbathymidine (N-MCT)], a thymidine analog with a pseudosugar ring locked in the northern conformation, which has previously been shown to block the replication of herpes simplex virus types 1 and 2. N-MCT inhibited KSHV virion production in lytically induced KSHV-infected BCBL-1 cells with a substantially lower 50% inhibitory concentration (IC50) than those of cidofovir (CDV) and ganciclovir (GCV) (IC50, mean +/- standard deviation: 0.08 +/- 0.03, 0.42 +/- 0.07, and 0.96 +/- 0.49 microM for N-MCT, CDV, and GCV, respectively). The reduction in KSHV virion production was accompanied by a corresponding decrease in KSHV DNA levels in the N-MCT-treated BCBL-1 cells, indicating that the compound blocked lytic KSHV DNA replication. A time- and dose-dependent accumulation of N-MCT-triphosphate (TP) was demonstrated in lytically induced BCBL-1 cells, while uninfected cells showed virtually no accumulation. The levels of N-MCT-TP were significantly decreased in the presence of 5'-ethynylthymidine, a potent inhibitor of herpesvirus thymidine kinase, resulting in the abrogation of anti-KSHV activity of N-MCT. N-MCT-TP more effectively blocked in vitro DNA synthesis by KSHV DNA polymerase with an IC50 of 6.24 +/- 0.08 microM (mean +/- standard deviation) compared to CDV-diphosphate (14.70 +/-2.47 microM) or GCV-TP (24.59 +/- 5.60 microM). Taken together, N-MCT is a highly potent and target-specific anti-KSHV agent which inhibits lytic KSHV DNA synthesis through its triphosphate metabolite produced in KSHV-infected cells expressing a virally encoded thymidine kinase.
authors.affiliation: Laboratory of Antiviral Drug Mechanisms, SAIC-Frederick, Frederick, Maryland 21702, USA.
authors.forename: Weimin
authors.initials: W
authors.lastname: Zhu
authors.forename: Angela
authors.initials: A
authors.lastname: Burnette
authors.forename: Dorjbal
authors.initials: D
authors.lastname: Dorjsuren
authors.forename: Paula E
authors.initials: PE
authors.lastname: Roberts
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Huleihel
authors.forename: Robert H
authors.initials: RH
authors.lastname: Shoemaker
authors.forename: Victor E
authors.initials: VE
authors.lastname: Marquez
authors.forename: Riad
authors.initials: R
authors.lastname: Agbaria
authors.forename: Shizuko
authors.initials: S
authors.lastname: Sei
mesh_terms: D000998:Antiviral Agents / Q000378:metabolism / Q000494:pharmacology*; D019288:Herpesvirus 8, Human / Q000187:drug effects* / Q000254:growth & development; D006801:Humans; D020128:Inhibitory Concentration 50; D012514:Sarcoma, Kaposi / Q000188:drug therapy*; D013936:Thymidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D014407:Tumor Cells, Cultured
chemical_list: D000998:Antiviral Agents; C469995:(north)-methanocarbathymidine; D013936:Thymidine