ACTA VETERINARIA ET ZOOTECHNICA SINICA ›› 2016, Vol. 47 ›› Issue (6): 1280-1286.doi: 10.11843/j.issn.0366-6964.2016.06.026

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Expression of the Nucleocapsid Protein of Schmallenberg Virus Using the Bac-to-Bac® Baculovirus Expression System and Preparation of Monoclonal Antibodies against This Protein

ZHANG Yong-ning#,SONG Shan-shan#,WU Shao-qiang,LIN Xiang-mei*   

  1. (Institute of Animal Quarantine,Chinese Academy of Inspection and Quarantine,Beijing 100029,China)
  • Received:2015-08-19 Online:2016-06-23 Published:2016-06-23

Abstract:

The objective of this study was to express and purify the nucleocapsid (N) protein of Schmallenberg virus (SBV) with the native conformation,and to prepare its monoclonal antibodies (McAbs).To this end,the SBV-N gene with an inserted coding sequence for an N-terminal hexahistidine (6×His) tag was cloned into the pFastBacTM 1 vector.The resulting recombinant donor plasmid,pFastBac-His-SBV-N,was then transformed into DH10Bac E.coli competent cells.After selection with the blue/white screen,the recombinant bacmid,rBacmid-His-SBV-N,was transfected into Sf9 insect cells to generate recombinant baculoviruses that express the His-SBV-N fusion protein.After amplifying the recombinant baculoviral stocks on Sf9 cells,His-SBV-N fusion protein was purified using nickel nitrilotriacetic acid (Ni-NTA) agarose.The purified protein was then used to immunize BALB/c mice to prepare SBV-N-specific McAbs,and an indirect double-antibody binding ELISA was applied to detect whether the generated McAbs recognize different antigenic sites.The screened McAbs that recognize different antigenic sites were labeled with horseradish peroxidase (HRP) using the sodium periodate oxdization method.Finally,four McAbs (2A11,2E1,4H11 and 6E12) recognizing different antigenic sites were successfully obtained and labeled with HRP.The results of isotype identification demonstrated that 2A11 belongs to IgG1,and 2E1,4H11 and 6E12 belong to IgG2b.Indirect immunofluorescence assays revealed that all of the four McAbs reacted with the BHK-21 cell line stably expressing the SBV-N protein (BHK-21-EGFP-SBV-N).Western blot analyses further showed that the four HRP-conjugated McAbs reacted positively with the His-SBV-N fusion protein.Taken together,the successful preparation of His-SBV-N fusion protein and its McAbs provide valuable biological materials that can be used in the serological diagnosis of Schmallenberg disease.

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