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Dive into the research topics where Kentarou Yoshii is active.

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Featured researches published by Kentarou Yoshii.


Vaccine | 2001

Evaluation of European tick-borne encephalitis virus vaccine against recent Siberian and far-eastern subtype strains.

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

A BHK-21 cell culture-adapted tick-borne encephalitis virus mutant is attenuated for neuroinvasiveness

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

Sub-genomic replicons of Tick-borne encephalitis virus

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

Enzyme-linked immunosorbent assay using recombinant antigens expressed in mammalian cells for serodiagnosis of tick-borne encephalitis.

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

Amino acid changes responsible for attenuation of virus neurovirulence in an infectious cDNA clone of the Oshima strain of Tick-borne encephalitis virus

Daisuke Hayasaka; Tamara S. Gritsun; Kentarou Yoshii; Tomotaka Ueki; Akiko Goto; Tetsuya Mizutani; Hiroaki Kariwa; Takuya Iwasaki; Ernest A. Gould; Ikuo Takashima


Vaccine | 2005

Role of the N-linked glycans of the prM and E envelope proteins in tick-borne encephalitis virus particle secretion.

Akiko Goto; Kentarou Yoshii; Mayumi Obara; Tomotaka Ueki; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima


Journal of General Virology | 2004

Single point mutation in tick-borne encephalitis virus prM protein induces a reduction of virus particle secretion

Kentarou Yoshii; Akihiro Konno; Akiko Goto; Junko Nio; Mayumi Obara; Tomotaka Ueki; Daisuke Hayasaka; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima


Vaccine | 2005

Packaging the replicon RNA of the Far-Eastern subtype of tick-borne encephalitis virus into single-round infectious particles: development of a heterologous gene delivery system.

Kentarou Yoshii; Daisuke Hayasaka; Akiko Goto; Kazue Kawakami; Hiroaki Kariwa; Ikuo Takashima


Japanese Journal of Veterinary Research | 2002

Genetic and biological comparision of tick-borne encephalitis viruses from Hokkaido and Far-Eastern Russia

Akiko Goto; Daisuke Hayasaka; Kentarou Yoshii; Tetsuya Mizutani; Hiroaki Kariwa; Ikuo Takashima


Uirusu | 2005

[Phylogenetic analysis and pathogenicity of tick-borne encephalitis virus from Japan and far-east Russia].

Ikuo Takashima; Daisuke Hayasaka; Akiko Goto; Kentarou Yoshii; Hiroaki Kariwa

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Tetsuya Mizutani

Tokyo University of Agriculture and Technology

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