title: Characterization and treatment of cidofovir-resistant vaccinia (WR strain) virus infections in cell culture and in mice.
abstract: The wild-type (WT) vaccinia (WR strain) virus is highly virulent to mice by intranasal inoculation, yet death can be prevented by cidofovir treatment. A cidofovir-resistant (CDV-R) mutant of the virus was developed by 15 Vero cell culture passages in order to determine cross-resistance to other inhibitors, growth characteristics, virulence in infected mice, and suitability of the animal model for studying antiviral therapies. Comparisons were made to the original WT virus and to a WT virus passaged 15 times in culture (WTp15 virus). Cidofovir inhibited WT, WTp15, and CDV-R viruses by 50% at 61, 56 and 790 microM, respectively, in plaque reduction assays, with similar inhibition seen in virus yield studies. Cross-resistance occurred with compounds related to cidofovir, but not with unrelated nucleosides. The resistant virus produced 300-fold fewer infectious particles (PFU) than WT and WTp15 viruses in mouse C1271 cells, yet replicated similarly in Vero (monkey) cells. The CDV-R virus was completely attenuated for virulence at 10(7) PFU per mouse in normal BALB/c mice and in severe combined immunodeficient (SCID) mice. The WTp15 virus was 100-fold less virulent than WT virus in BALB/c mice. Thus, the lack of virulence of the resistant virus in the animal model is explained partly by its reduced ability to replicate in mouse cells and by attenuation occurring as a result of extensive cell culturing (inferred from what occurred with the WTp15 virus). Lung and snout virus titre reduction parameters were used to assess antiviral activity of compounds in BALB/c mice infected intranasally with the CDV-R virus. Cidofovir, HDP-cidofovir and arabinofuranosyladenine treatments reduced lung virus titres <fourfold, and snout virus titres > or = eight-fold. The animal model appears to have limited utility in drug efficacy testing.
authors: Institute for Antiviral Research, Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, UT, USA. dsmee@cc.usu.edu
authors: Donald F
authors: DF
authors: Smee
authors: Miles K
authors: MK
authors: Wandersee
authors: Kevin W
authors: KW
authors: Bailey
authors: Karl Y
authors: KY
authors: Hostetler
authors: Antonin
authors: A
authors: Holy
authors: Robert W
authors: RW
authors: Sidwell
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D000077404:Cidofovir; D003596:Cytosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004195:Disease Models, Animal; D004351:Drug Resistance / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D009154:Mutation; D063065:Organophosphonates / Q000494:pharmacology*; D014615:Vaccinia / Q000821:virology; D014616:Vaccinia virus / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity; D014779:Virus Replication
chemical_list: D063065:Organophosphonates; D003596:Cytosine; D000077404:Cidofovir