Isolation and characterization of cidofovir resistant vaccinia viruses.
BACKGROUND
The emergence of drug resistant viruses, together with the possibility of increased virulence, is an important concern in the development of new antiviral compounds. Cidofovir (CDV) is a phosphonate nucleotide that is approved for use against cytomegalovirus retinitis and for the emergency treatment of smallpox or complications following vaccination. One mode of action for CDV has been demonstrated to be the inhibition of the viral DNA polymerase.


RESULTS
We have isolated several CDV resistant (CDVR) vaccinia viruses through a one step process, two of which have unique single mutations within the DNA polymerase. An additional resistant virus isolate provides evidence of a second site mutation within the genome involved in CDV resistance. The CDVR viruses were 3-7 fold more resistant to the drug than the parental viruses. The virulence of the CDVR viruses was tested in mice inoculated intranasally and all were found to be attenuated.


CONCLUSIONS
Resistance to CDV in vaccinia virus can be conferred individually by at least two different mutations within the DNA polymerase gene. Additional genes may be involved. This one step approach for isolating resistant viruses without serial passage and in the presence of low doses of drug minimizes unintended secondary mutations and is applicable to other potential antiviral agents.
Becker
Marie N
MN
University of Florida, Gainesville, FL, USA. mnbecker@ufl.edu
Obraztsova
Maria
M
Kern
Earl R
ER
Quenelle
Debra C
DC
Keith
Kathy A
KA
Prichard
Mark N
MN
Luo
Ming
M
Moyer
Richard W
RW
D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology; D002460:Cell Line; D002522:Chlorocebus aethiops; D000077404:Cidofovir; D003596:Cytosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D024882:Drug Resistance, Viral; D005260:Female; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D009154:Mutation; D063065:Organophosphonates / Q000494:pharmacology*; D014615:Vaccinia / Q000401:mortality / Q000821:virology; D014616:Vaccinia virus / Q000187:drug effects* / Q000302:isolation & purification* / Q000472:pathogenicity / Q000502:physiology; D014709:Vero Cells; D010948:Viral Plaque Assay; D014774:Virulence
D000998:Antiviral Agents; D063065:Organophosphonates; D003596:Cytosine; D004259:DNA-Directed DNA Polymerase; D000077404:Cidofovir