Deletions in the hypervariable domain of the nsP3 gene attenuate Semliki Forest virus virulence.
Major virulence determinants of Semliki Forest virus (SFV) lie within the non-structural genes that form the replicase complex proteins. Gene exchange between virulent and avirulent viruses has shown that the nsP3 gene, which has essential 5' conserved domains and a non-essential hypervariable 3' domain, is one of the virulence determinants. This protein plays a role in subgenomic 26S and negative-strand RNA synthesis and is thought to function with nsP1 to anchor replication complexes to cell membrane structures. Studies to date have focused on analysing the effect of mutational changes spread over the whole gene on virulence of the virus. The virulent SFV4 virus, derived from an infectious clone, was utilized to analyse the effect on virulence of large deletions in the hypervariable domain of nsP3. Two viruses with different in-frame deletions that spanned this domain showed reduced rates of RNA synthesis and multiplication in cell culture. In adult BALB/c mice, these viruses were avirulent after intramuscular and intraperitoneal inoculation, and brains sampled from infected mice showed minimal or no evidence of pathology. These deleted viruses had greatly reduced virulence when administered by the intranasal route and brains from infected mice showed lesions that were much less severe than those seen in SFV4 infection. Mice surviving infection with the deleted viruses resisted challenge with the virulent L10 strain, indicating induction of protective immunity. This work establishes that deletions in the nsP3 hypervariable domain attenuate virulence after peripheral inoculation and also reduce virulence after intranasal inoculation.
Galbraith
Sareen E
SE
University College Dublin School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.|Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
Sheahan
Brian J
BJ
University College Dublin School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
Atkins
Gregory J
GJ
Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
D018354:Alphavirus Infections / Q000473:pathology* / Q000821:virology; D000595:Amino Acid Sequence; D000818:Animals; D041702:BALB 3T3 Cells; D001483:Base Sequence; D002460:Cell Line; D006224:Cricetinae; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D012672:Semliki forest virus / Q000235:genetics / Q000472:pathogenicity*; D017384:Sequence Deletion; D013047:Specific Pathogen-Free Organisms; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000235:genetics*; D014774:Virulence
C414175:Nsp3 protein, semliki forest virus; D016601:RNA-Binding Proteins; D017361:Viral Nonstructural Proteins