Kentarou Yoshii
Hokkaido University
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Featured researches published by Kentarou Yoshii.
Vaccine | 2001
Daisuke Hayasaka; Akiko Goto; Kentarou Yoshii; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima
To evaluate the efficacy of the European TBE vaccine in east-Siberian and far-eastern regions of Russia, we examined the immune responses of the vaccine against recent TBE virus Siberian (Irkutsk) and far-eastern (Khabarovsk and Vladivostok) isolates. The sera of vaccinated humans showed efficient neutralizing antibody titers (> or =20) against Siberian and far-eastern strains. To evaluate the efficacy of the vaccine in vivo, mice were vaccinated and challenged with lethal doses of the viruses. All vaccinated mice survived each virus challenge. These results suggest that the European vaccine can prevent the TBE virus infection in east-Siberian and far-eastern regions of Russia.
Vaccine | 2003
Akiko Goto; Daisuke Hayasaka; Kentarou Yoshii; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima
We derived the baby hamster kidney (BHK)-21 cell culture-adapted, tick-borne encephalitis (TBE) virus mutant. To reveal the pathogenicity of the TBE virus, we compared the pathogenicity of the mutant (Oshima Cl-1) and parental (Oshima 5-10) virus in mouse model. The neurovirulence of mutant in mice was identical to that of parent. However, the level of neuroinvasiveness was higher for parent than for mutant. The degrees of viremia and virus titers in the spleen were lower in mice that were inoculated subcutaneously (s.c.) with mutant than in mice that received parent. Unlike parent, mutant was rarely detected in the brains of s.c. inoculated mice. Genetic analysis revealed that mutant had single amino acid substitutions in each of the E and NS5 proteins compared with parent. Furthermore, while mutant infection of BHK-21 cells was inhibited by glycosaminoglycans (GAGs), this was not the case for parent. In summary, the BHK-21-cell-adapted mutant virus showed reduced neuroinvasiveness in mice due to low-level induction of viremia. The attenuation process involved a single amino acid change in the E protein, which may have resulted in the rapid clearance of the virus due to its high affinity for negatively charged molecules in vivo.
Archives of Virology | 2004
Daisuke Hayasaka; Kentarou Yoshii; Tomotaka Ueki; Takuya Iwasaki; Ikuo Takashima
SummaryWe constructed three sub-genomic replicons of Tick-borne encephalitis virus (TBEV) (Oshima REP, Oshima REP-GFP and Oshima REP-Neo) by deleting genes coding for structural proteins without or with insertion of green fluorescent protein (GFP) or Neo genes, respectively. BHK cells transfected with Oshima REP expressed the viral non-structural antigens in immunofluorescent and western blot analyses. GFP and viral antigens were co-expressed in the transfected cells with Oshima REP-GFP. G418-resistant cells harboring Oshima REP-Neo consistently expressed the antigens without showing any apparent CPE. These replicons constructed in this study will be useful in studies on the replication, assembly and packaging of TBEV, and to develop vaccines and gene-delivering systems.
Journal of Virological Methods | 2003
Kentarou Yoshii; Daisuke Hayasaka; Akiko Goto; Mayumi Obara; Koichi Araki; Kumiko Yoshimatsu; Jiro Arikawa; Leonoid Ivanov; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima
A recombinant plasmid that expresses the tick-borne encephalitis (TBE) virus premembrane (prM) and envelope (E) proteins in mammalian cells was constructed. Recombinant proteins retained antigenic and conformational structures similar to those of native virus proteins, and transfected cells released virus-like particles (VLPs), which were 1.13-1.14 g/ml in density and 20-30 nm in diameter, into the culture medium. Recombinant E proteins were used for the development of an enzyme-linked immunosorbent assay (ELISA) to detect TBE virus-specific IgM and IgG antibodies in serum. The results of this ELISA correlated well with the results of commercial ELISA, when tested with 95 serum samples from clinically TBE-suspected patients. In addition, ELISA using recombinant antigens showed no cross-reactivity against serum from Japanese encephalitis (JE) patients, despite the cross-reactivity shown by commercial ELISA systems. These observations indicated that this newly developed ELISA system could distinguish tick-borne encephalitis from Japanese encephalitis infection, and that it constitutes a useful and safe alternative to conventional ELISA systems.
Journal of General Virology | 2004
Daisuke Hayasaka; Tamara S. Gritsun; Kentarou Yoshii; Tomotaka Ueki; Akiko Goto; Tetsuya Mizutani; Hiroaki Kariwa; Takuya Iwasaki; Ernest A. Gould; Ikuo Takashima
Vaccine | 2005
Akiko Goto; Kentarou Yoshii; Mayumi Obara; Tomotaka Ueki; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima
Journal of General Virology | 2004
Kentarou Yoshii; Akihiro Konno; Akiko Goto; Junko Nio; Mayumi Obara; Tomotaka Ueki; Daisuke Hayasaka; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima
Vaccine | 2005
Kentarou Yoshii; Daisuke Hayasaka; Akiko Goto; Kazue Kawakami; Hiroaki Kariwa; Ikuo Takashima
Japanese Journal of Veterinary Research | 2002
Akiko Goto; Daisuke Hayasaka; Kentarou Yoshii; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima
Uirusu | 2005
Ikuo Takashima; Daisuke Hayasaka; Akiko Goto; Kentarou Yoshii; Hiroaki Kariwa