Yan Liu

Zhejiang University, Hangzhou, Zhejiang Sheng, China

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Publications (5)10.17 Total impact

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    Article: Expression and immunogenicity analysis of two iron-regulated outer membrane proteins of Vibrio parahaemolyticus.
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    ABSTRACT: Genes of two iron-regulated outer membrane proteins of Vibrio parahaemolyticus zj2003, a pathogenic strain isolated from large yellow croaker (Pseudosciaena crocea), psuA and pvuA, were cloned and expressed as N-terminal His(6)-tagged proteins in Escherichia coli BL(21)(DE(3)). The recombinant fusion proteins were purified with nickel chelate affinity chromatography. To analyze the immunogenicity of the proteins, groups of large yellow croaker were immunized with the purified recombinant psuA, pvuA or both, by intraperitoneal injection. Antibody response was assessed by enzyme-linked immunosorbent assay. Titers to the recombinant proteins increased from log(2) 3.25 to log(2) 9.80, 4-8 weeks following immunization. The relative percent survival of the groups vaccinated with psuA, pvuA, or a combination of the two, reached 50%, 62.5% and 75%, respectively. Western blot analysis was carried out with the serum from unvaccinated survival fish after infection. Both recombinant proteins were detected, indicating that these two proteins of V. parahaemolyticus zj2003 were immunogenic and could produce synergistic effects during in vivo infection, and they might be considered as important components for developing an aquaculture vaccine against this pathogen.
    Acta Biochimica et Biophysica Sinica 11/2007; 39(10):763-9. · 1.38 Impact Factor
  • Article: Cloning, expression and immunogenicty analysis of five outer membrane proteins of Vibrio parahaemolyticus zj2003.
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    ABSTRACT: Genes of five outer membrane proteins of Vibrio parahaemolyticus zj2003, including OmpW, OmpV, OmpK, OmpU and TolC, were cloned and expressed as N-terminal His(6)-tagged proteins in Escherichia coli. The recombinant fusion proteins were purified with nickel chelate affinity chromatography. To analyze the immunogenicity of these proteins, large yellow croaker (Pseudosciaena crocea) were immunized by intraperitoneal injection. Antibody response was assessed by method of enzyme-linked immunosorbent assay. Titres to all five recombinant proteins increased during 4 to 8 weeks post immunization, within the range of log 2 values of 5.75 to 10.8. Recorded relative survival percent (RPS) of the vaccinated groups varied from 80% to 90%, while 10 fish in control group all died. Western blot tests were undertaken with the serum of survival fish after experimental infection. Except for recombinant TolC, the other four recombinant proteins were recognized by the serum. It is indicated that four outer membrane proteins of V. parahaemolyticus zj2003, including OmpW, OmpV, OmpU and OmpK, are immunogenic during in vivo infection, which would be of some significance in developing efficient vaccine in aquaculture. This is the first report of successful vaccination against V. parahaemolyticus with purified recombinant outer membrane proteins.
    Fish &amp Shellfish Immunology 10/2007; 23(3):567-75. · 3.32 Impact Factor
  • Article: Analysis of tissue-specific region in sericin 1 gene promoter of Bombyx mori.
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    ABSTRACT: The gene encoding sericin 1 (Ser1) of silkworm (Bombyx mori) is specifically expressed in the middle silk gland cells. To identify element involved in this transcription-dependent spatial restriction, truncation of the 5' terminal from the sericin 1 (Ser1) promoter is studied in vivo. A 209bp DNA sequence upstream of the transcriptional start site (-586 to -378) is found to be responsible for promoting tissue-specific transcription. Analysis of this 209bp region by overlapping deletion studies showed that a 25bp region (-500 to -476) suppresses the ectopic expression of the Ser1 promoter. An unknown factor abundant in fat body nuclear extracts is shown to bind to this 25bp fragment. These results suggest that this 25bp region and the unknown factor are necessary for determining the tissue-specificity of the Ser1 promoter.
    Biochemical and Biophysical Research Communications 04/2006; 342(1):273-9. · 2.48 Impact Factor
  • Article: [Cloning, expression and preparation of polyclonal antibody for IBDV non-structure protein gene].
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    ABSTRACT: Infectious bursal disease virus (IBDV) VP5 gene was amplified and cloned into an N-terminal GST-Tag fusion expression vector, pGEX-4T-2, which was controlled by T7 promoter. The sequencing result showed that the VP5 gene was composed of 438 base pairs, and coded 145 amino acids. High VP5 product was expressed in E. coli BL21 induced by IPTG, and the GST-VP5 fusion protein existed in inclusion. High titer anti-VP5 serum was also prepared in New Zealand rabbit immunized with purified fusion protein inclusion. These results gave a basis for further research for VP5 function in IBDV replication and pathogenicity, which also paved the way for developing VP5 gene deleted IBDV live vaccine.
    ACTA MICROBIOLOGICA SINICA 11/2005; 45(5):763-6.
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    Article: Preparation of ChIL-2 and IBDV VP2 fusion protein by baculovirus expression system.
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    ABSTRACT: This study aims to produce an effective subunit vaccine against infectious bursal disease virus (IBDV). The genes of chicken interleukin-2 (ChIL-2) and IBDV viral protein 2 (VP2) were amplified and fused by splice overlap extension-polymerase chain reaction (SOE-PCR). The fusion gene was digested by EcoR I/Kpn I and inserted into pBacPAK8 vector, resulting in recombinant transfer plasmid pBacPakVP2-IL2. The recombinant plasmid was transfected into Sf-9 cells accompanied with hybrid nuclear polyhedrosis virus (HyNPV) genome DNA and lipofectin. Plaque-purification indicated that we had got the recombinant Hy-VP2-IL2. Fusion protein VP2-IL2 was expressed effectively both in insect cells and bombyx mori. The expression of fusion protein was confirmed by ELISA, SDS-PAGE and Western blotting assay, respectively. This efficient system allows us to meet the need for inexpensive vaccines required by the poultry industry.
    Cellular & molecular immunology 07/2005; 2(3):231-5. · 2.99 Impact Factor