Phylogenetic analysis and pathogenicity of tick-borne encephalitis virus from Japan and far-east Russia |
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Authors: | Takashima Ikuo Hayasaka Daisuke Goto Akiko Yoshii Kentarou Kariwa Hiroaki |
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Institution: | Laboratory of Public Health, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan. |
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Abstract: | Phylogenetic analysis of tick-borne encephalitis (TBE) virus revealed that Hokkaido strain of TBE virus evolved several hundreds years ago in far-east Russia. TBE virus strains in Irkutsk area were identified as Siberian subtype of TBE virus. BHK-cell adapted mutant of TBE virus showed lower neuro-invasive virulence in mice than parent virus. The mutant carried one amino acid substitution in envelope protein which resulted in increase of positive charge of the protein. The mutant-infected mice showed lower virus titers in bloods and spleens than the parent-infected mice. Infectious c-DNA clone of TBE virus Hokkaido strain was successfully generated and was applied to examine the neurovirulence in mice. One amino acid change in envelope protein and 2 amino acid changes in Ns5 protein showed a synergistic effect on reduced neurovirulence in mice. |
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