title: Amino acid changes responsible for attenuation of virus neurovirulence in an infectious cDNA clone of the Oshima strain of tick-borne encephalitis virus.
abstract: A stable full-length infectious cDNA clone of the Oshima strain of Tick-borne encephalitis virus (Far-Eastern subtype) was developed by a long high-fidelity RT-PCR and one-step cloning procedure. The infectious clone (O-IC) had four amino acid substitutions and produced smaller plaques when compared with the parent Oshima 5-10 strain. Using site-directed mutagenesis, the substitutions were reverted to restore the parent virus sequence (O-IC-pt). Although genetically identical, parent virus Oshima 5-10 and virus recovered from O-IC-pt demonstrated some biological differences that are possibly explained by the presence of quasispecies with differing virulence characteristics within the original virus population. These observations may have implications for vaccines based on modified infectious clones. It was also demonstrated that the amino acid substitution E-S(40)-->P at position 40 in the envelope (E) glycoprotein was responsible for plaque size reduction, reduced infectious virus yields in cell culture and reduced mouse neurovirulence. Additionally, two amino acid substitutions in the non-structural (NS)5 protein (virus RNA-dependent RNA polymerase) NS5-V(378)-->A and NS5-R(674)-->K also contributed to attenuation of virulence in mice, but did not demonstrate a noticeable biological effect in baby hamster kidney cell culture. Comparative neurovirulence tests revealed how the accumulation of individual mutations (E-S(40)-->P, NS5-V(378)-->A and NS5-R(674)-->K) can result in the attenuation of a virus.
authors.affiliation: Department of Pathology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.|Laboratory of Public Health, Department of Environmental Veterinary Science, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hayasaka
authors.affiliation: Centre for Ecology and Hydrology, Oxford, UK.
authors.forename: Tamara S
authors.initials: TS
authors.lastname: Gritsun
authors.affiliation: Laboratory of Public Health, Department of Environmental Veterinary Science, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Kentarou
authors.initials: K
authors.lastname: Yoshii
authors.affiliation: Laboratory of Public Health, Department of Environmental Veterinary Science, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Tomotaka
authors.initials: T
authors.lastname: Ueki
authors.affiliation: Laboratory of Public Health, Department of Environmental Veterinary Science, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Goto
authors.affiliation: Laboratory of Public Health, Department of Environmental Veterinary Science, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizutani
authors.affiliation: Laboratory of Public Health, Department of Environmental Veterinary Science, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kariwa
authors.affiliation: Department of Pathology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Iwasaki
authors.affiliation: Centre for Ecology and Hydrology, Oxford, UK.
authors.forename: Ernest A
authors.initials: EA
authors.lastname: Gould
authors.affiliation: Laboratory of Public Health, Department of Environmental Veterinary Science, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Takashima
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics; D004669:Encephalitis Viruses, Tick-Borne / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014774:Virulence / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D004279:DNA, Viral