Zijiang Zhao

Tokyo Metropolitan Institute, Edo, Tōkyō, Japan

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Publications (8)80.4 Total impact

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    ABSTRACT: Because appropriate cell-culture systems or small-animal models have been lacking, the early steps in the HCV life cycle have been difficult to study. A cell culture system was developed recently that allows production of infectious HCV. In this study, infectious HCV particles produced in cultured cells were used. To clarify the role of CD81 in HCV attachment and entry, the effect of anti-CD81 antibody was examined. The antibody blocked HCV virion entry but not particle attachment. Only the fraction bound to a heparin affinity column and eluted with 0.3 M NaCl productively infected Huh7 cells, indicating that infectious HCV particles bind to heparin. Both heparin treatment of the virus particles and heparinase treatment of the Huh7 cells reduced virus-cell binding without substantially inhibiting HCV infectivity. Finally, to confirm the role of both heparin sulfate proteoglycan (HSPG) and CD81 in HCV entry, the effects of heparinase I and anti-CD81 antibody were analyzed. No productive RNA replication was detected in the Huh7 cells in the presence of both heparinase I and anti-CD81 antibody. In conclusion, these data suggested that both HSPG and CD81 are important for HCV entry. HSPG may play a role in the initial cell surface binding of infectious HCV particles and CD81 is conceivably correlated with HCV entry after viral attachment.
    Journal of Medical Virology 07/2007; 79(6):714-23. · 2.22 Impact Factor
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    ABSTRACT: A stable plasmid DNA, pMWJEAT, was constructed by using full-length Japanese encephalitis virus (JEV) cDNA isolated from the wild-type strain JEV AT31. Recombinant JEV was obtained by synthetic RNA transfection into Vero cells and designated rAT virus. JEV rAT exhibited similar large-plaque morphology and antigenicity to the parental AT31 strain. Mutant clone pMWJEAT-E138K, containing a single Glu-to-Lys mutation at aa 138 of the envelope (E) protein, was also constructed to analyse the mechanisms of viral attenuation arising from this mutation. Recombinant JEV rAT-E138K was also recovered and displayed a smaller-plaque morphology and lower neurovirulence and neuroinvasiveness than either AT31 virus or rAT virus. JEV rAT-E138K exhibited greater plaque formation than rAT virus in virus-cell interactions under acidic conditions. Heparin or heparinase III treatment inhibited binding to Vero cells more efficiently for JEV rAT-E138K than for rAT virus. Inhibition of virus-cell interactions by using wheatgerm agglutinin was more effective for JEV rAT than for rAT-E138K on Vero cells. About 20 % of macropinoendocytosis of JEV rAT for Vero cells was inhibited by cytochalasin D treatment, but no such inhibition occurred for rAT-E138K virus. Furthermore, JEV rAT was predominantly secreted from infected cells, whereas rAT-E138K was more likely to be retained in infected cells. This study demonstrates clearly that a single Glu-to-Lys mutation at aa 138 of the envelope protein affects multiple steps of the viral life cycle. These multiple changes may induce substantial attenuation of JEV.
    Journal of General Virology 09/2005; 86(Pt 8):2209-20. · 3.53 Impact Factor
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    ABSTRACT: Hepatitis C virus (HCV) infection causes chronic liver diseases and is a global public health problem. Detailed analyses of HCV have been hampered by the lack of viral culture systems. Subgenomic replicons of the JFH1 genotype 2a strain cloned from an individual with fulminant hepatitis replicate efficiently in cell culture. Here we show that the JFH1 genome replicates efficiently and supports secretion of viral particles after transfection into a human hepatoma cell line (Huh7). Particles have a density of about 1.15-1.17 g/ml and a spherical morphology with an average diameter of about 55 nm. Secreted virus is infectious for Huh7 cells and infectivity can be neutralized by CD81-specific antibodies and by immunoglobulins from chronically infected individuals. The cell culture-generated HCV is infectious for chimpanzee. This system provides a powerful tool for studying the viral life cycle and developing antiviral strategies.
    Nature Medicine 08/2005; 11(7):791-6. · 28.05 Impact Factor
  • Nature Medicine 08/2005; · 28.05 Impact Factor
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    ABSTRACT: Japanese encephalitis virus (JEV) core protein was detected in both the nucleoli and cytoplasm of mammalian and insect cell lines infected with JEV or transfected with the expression plasmid of the core protein. Mutation analysis revealed that Gly(42) and Pro(43) in the core protein are essential for the nuclear and nucleolar localization. A mutant M4243 virus in which both Gly(42) and Pro(43) were replaced by Ala was recovered by plasmid-based reverse genetics. In C6/36 mosquito cells, the M4243 virus exhibited RNA replication and protein synthesis comparable to wild-type JEV, whereas propagation in Vero cells was impaired. The mutant core protein was detected in the cytoplasm but not in the nucleus of either C6/36 or Vero cell lines infected with the M4243 virus. The impaired propagation of M4243 in mammalian cells was recovered by the expression of wild-type core protein in trans but not by that of the mutant core protein. Although M4243 mutant virus exhibited a high level of neurovirulence comparable to wild-type JEV in spite of the approximately 100-fold-lower viral propagation after intracerebral inoculation to 3-week-old mice of strain Jcl:ICR, no virus was recovered from the brain after intraperitoneal inoculation of the mutant. These results indicate that nuclear localization of JEV core protein plays crucial roles not only in the replication in mammalian cells in vitro but also in the pathogenesis of encephalitis induced by JEV in vivo.
    Journal of Virology 04/2005; 79(6):3448-58. · 4.65 Impact Factor
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    ABSTRACT: The hepatitis C virus (HCV) genotype 2a subgenomic replicon can replicate in two human non-hepatocyte-derived cell lines, HeLa and 293, with in vitro-transcribed replicon RNA. Sequencing analysis revealed that mutations in HCV-derived regions were not essential for replication in these cells, as some clones displayed no mutations.
    Journal of Virology 02/2005; 79(1):592-6. · 4.65 Impact Factor
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    ABSTRACT: A hepatitis C virus genotype 2a subgenomic replicon, JFH-1 replicon, was previously established using the consensus sequence of clone JFH-1 from a patient with fulminant hepatitis and, in a previous report, was indicated to replicate efficiently in Huh7. Here the replication of JFH-1 replicon was tested in HepG2, a human hepatocyte-derived cell line, and in IMY-N9, a cell line developed by fusing human hepatocytes and HepG2 cells. Following transfection with in vitro transcribed replicon RNA and selection by cultivation with G418, colonies formed in both cell lines although at efficiencies substantially lower than those of Huh7. The H2476L mutation identified in the Huh7 replicon in our previous study increased the colony formation efficiencies of the JFH-1 replicon in HepG2 and IMY-N9 cells. Higher amounts of replicon RNA were detected in IMY-N9 clones than in HepG2 clones by real time detection reverse transcription-PCR, and replicon RNA replication and viral protein expression were confirmed by Northern and Western blotting in isolated clones. Sequencing of replicon RNAs revealed that mutations found in hepatitis C virus-derived regions were not identical and that two of nine HepG2 clones and three of nine IMY-N9 clones had no or one synonymous mutation. This system with the JFH-1 replicon and three cell lines is useful not only for estimating the cellular factors affecting viral activity but also for clarifying the common gene response of the host.
    Journal of Biological Chemistry 06/2004; 279(21):22371-6. · 4.60 Impact Factor
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    Zijiang Zhao, Takaji Wakita, Kotaro Yasui
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    ABSTRACT: We established a simple and effective method for DNA immunization against Japanese encephalitis virus (JEV) infection with plasmids encoding the viral PrM and E proteins and colloidal gold. Inoculation of plasmids mixed with colloidal gold induced the production of specific anti-JEV antibodies and a protective response against JEV challenge in BALB/c mice. When we compared the efficacy of different inoculation routes, the intravenous and intradermal inoculation routes were found to elicit stronger and more sustained neutralizing immune responses than intramuscular or intraperitoneal injection. After being inoculated twice, mice were found to resist challenge with 100,000 times the 50% lethal dose (LD(50)) of JEV (Beijing-1 strain) even when immunized with a relatively small dose of 0.5 micro g of plasmid DNA. Protective passive immunity was also observed in SCID mice following transfer of splenocytes or serum from plasmid DNA- and colloidal gold-immunized BALB/c mice. The SCID mice resisted challenge with 100 times the LD(50) of JEV. Analysis of histological sections detected expression of proteins encoded by plasmid DNA in the tissues of intravenously, intradermally, and intramuscularly inoculated mice 3 days after inoculation. DNA immunization with colloidal gold elicited encoded protein expression in splenocytes and might enhance immune responses in intravenously inoculated mice. This approach could be exploited to develop a novel DNA vaccine.
    Journal of Virology 05/2003; 77(7):4248-60. · 4.65 Impact Factor

Publication Stats

2k Citations
80.40 Total Impact Points


  • 2003–2007
    • Tokyo Metropolitan Institute
      Edo, Tōkyō, Japan
  • 2005
    • Nagasaki University
      • Department of Virology
      Nagasaki, Nagasaki, Japan