title: Cell line dependency for antiviral activity and in vivo efficacy of N-methanocarbathymidine against orthopoxvirus infections in mice.
abstract: A novel carbocyclic thymidine analog, N-methanocarbathymidine [(N)-MCT], was evaluated for inhibition of orthopoxvirus infections. Efficacy in vitro was assessed by plaque reduction assays against wild-type and cidofovir-resistant strains of cowpox and vaccinia viruses in nine different cell lines. Minimal differences were seen in antiviral activity against wild-type and cidofovir-resistant viruses. (N)-MCT's efficacy was affected by the cell line used for assay, with 50% poxvirus-inhibitory concentrations in cells as follows: mouse=0.6-2.2 microM, rabbit=52-90 microM, monkey=87 to >1000 microM, and human=39-220 microM. Limited studies performed with carbocyclic thymidine indicated a similar cell line dependency for antiviral activity. (N)-MCT did not inhibit actively dividing uninfected cells at 1000 microM. The potency of (N)-MCT against an S-variant thymidine kinase-deficient vaccinia virus was similar to that seen against S-variant and wild-type viruses in mouse, monkey, and human cells, implicating a cellular enzyme in the phosphorylation of the compound. Mice were intranasally infected with cowpox and vaccinia viruses followed 24h later by intraperitoneal treatment with (N)-MCT (twice a day for 7 days) or cidofovir (once a day for 2 days). (N)-MCT treatment at 100 and 30 mg/kg/day resulted in 90 and 20% survival from cowpox virus infection, respectively, compared to 0% survival in the placebo group. Statistically significant reductions in lung virus titers on day 5 occurred in 10, 30, and 100mg/kg/day treated mice. These same doses were also active against a lethal vaccinia virus (WR strain) challenge, and protection was seen down to 10mg/kg/day against a lethal vaccinia virus (IHD strain) infection. Cidofovir (100mg/kg/day) protected animals from death in all three infections.
authors.affiliation: Institute for Antiviral Research, Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, UT 84322-5600, USA. dsmee@cc.usu.edu
authors.forename: Donald F
authors.initials: DF
authors.lastname: Smee
authors.forename: Miles K
authors.initials: MK
authors.lastname: Wandersee
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Bailey
authors.forename: Min-Hui
authors.initials: MH
authors.lastname: Wong
authors.forename: Chung K
authors.initials: CK
authors.lastname: Chu
authors.forename: Srinivas
authors.initials: S
authors.lastname: Gadthula
authors.forename: Robert W
authors.initials: RW
authors.lastname: Sidwell
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002460:Cell Line; D015605:Cowpox / Q000188:drug therapy* / Q000821:virology; D015608:Cowpox virus / Q000187:drug effects / Q000254:growth & development; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D011817:Rabbits; D012141:Respiratory Tract Infections / Q000188:drug therapy* / Q000821:virology; D013936:Thymidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D014615:Vaccinia / Q000188:drug therapy* / Q000821:virology; D014616:Vaccinia virus / Q000187:drug effects / Q000254:growth & development
chemical_list: D000998:Antiviral Agents; C469995:(north)-methanocarbathymidine; D013936:Thymidine