A mutation in the RNA polymerase of poliovirus type 1 contributes to attenuation in mice.
The attenuated Sabin strain of poliovirus type 1 (PV-1) differs from the neurovirulent PV-1 Mahoney strain by 55 nucleotide mutations. Only one of these mutations (A-480-->G, in the 5' noncoding (5' NC) region of the genome, is well characterized, and it confers a strong attenuating effect. We attempted to identify genetic attenuation determinants in the 3'-terminal part of the Sabin 1 genome including the 3D polymerase (3Dpol) gene and the 3' NC region. Previous studies suggested that some of the 11 mutations in this region of the Sabin 1 genome, and in particular a mutation in the polymerase gene (U-6203-->C, Tyr-73-->His), are involved to some extent in the attenuation of PV-1. We analyzed the attenuating effect in the mouse model by using the mouse-adapted PV-1/PV-2 chimeric strain v510 (a Mahoney strain carrying nine amino acids of the VP1 capsid protein from the Lansing strain of PV-2). Mutagenesis of locus 6203 was performed on the original v510 (U-6203-->C) and also on a hybrid v510/Sabin 1 (C-6203-->U) carrying the downstream 1,840 nucleotides of the Sabin 1 genome including the 3Dpol and 3' NC regions. Statistical analysis of disease incidence and time to disease onset in numerous mice inoculated with these strains strongly suggested that nucleotide C-6203 is involved in the attenuation of the Sabin 1 strain. Results also suggested that, among the mutations located in the 3Dpol and 3' NC regions, nucleotide C-6203 may be the principal or the only one to be involved in attenuation in this mouse model. We also found that the effect of C-6203 was weaker than that of nucleotide G-480; the two nucleotides acted independently and may have a cumulative effect on attenuation. The U-6203-->C substitution also appeared to contribute to the thermosensitivity of the Sabin 1 strain.
Unité de Virologie Médicale, Institut Pasteur, Paris, France.
M
M
Tardy-Panit
B
B
Blondel
A
A
Martin
F
F
Tekaia
F
F
Horaud
F
F
Delpeyroux
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004261:DNA Replication; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011051:Poliomyelitis / Q000382:microbiology / Q000503:physiopathology*; D017955:Poliovirus / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity*; D011401:Promoter Regions, Genetic; D013045:Species Specificity; D014162:Transfection; D014709:Vero Cells; D014774:Virulence / Q000235:genetics*
D004279:DNA, Viral; D009838:Oligodeoxyribonucleotides; D012321:DNA-Directed RNA Polymerases