Insertional inactivation of the large subunit of ribonucleotide reductase encoded by vaccinia virus is associated with reduced virulence in vivo.
To assess whether a fully functional VV ribonucleotide reductase enzyme is required during both in vitro and in vivo replication of VV, three mutant viruses were constructed by marker transfer techniques: M1 lambda, an M1 insertion mutant; TK-, an insertion mutant of the VV thymidine kinase (tk) gene; and M1 lambda/TK-, a double mutant. Extracts of cells infected with the M1 lambda or M1 lambda/TK- mutant viruses were assayed for ribonucleotide reductase activity and it was found that insertional inactivation of the M1 gene abolished the induction of viral enzyme activity in VV-infected cells. Each of the three mutant viruses replicated to levels comparable to the wild-type (WT) virus in BSC40 (monkey), growing A549 (human lung carcinoma) cells, and serum-starved A549 cells, indicating that a functional M1 gene was not required for viral replication in tissue culture. In contrast, in vivo studies indicate that the loss of viral ribonucleotide reductase activity leads to a mild attenuation of VV. By the intracranial route of inoculation, approximately 10-fold more of the M1 lambda recombinant than the WT virus was required to produce the average lethal dose for 50% of the population of injected mice.
Child
S J
SJ
Department of Microbiology, Oregon State University, Corvallis 97331.
Palumbo
G J
GJ
Buller
R M
RM
Hruby
D E
DE
D000818:Animals; D004251:DNA Transposable Elements; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D012264:Ribonucleotide Reductases / Q000032:analysis / Q000235:genetics*; D013937:Thymidine Kinase / Q000235:genetics; D014616:Vaccinia virus / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D014774:Virulence; D014779:Virus Replication
D004251:DNA Transposable Elements; D012264:Ribonucleotide Reductases; D013937:Thymidine Kinase