A dominant antigenic epitope on SARS-CoV spike protein identified by an avian single-chain variable fragment (scFv)-expressing phage

Yu Ching Lee, Sy Jye Christine Leu, Han Chang Hung, Hsueh Hsia Wu, I. Jen Huang, Wen Shyang Hsieh, Wen Ta Chiu, Ming Song Hsieh, Tsui Fen Cheng, Yi Yuan Yang

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Severe acute respiratory syndrome (SARS) is a newly emergent human disease, which requires rapid diagnosis and effective therapy. Among antibody sources, immunoglobulin Y (IgY) is the major antibody found in chicken eggs and can be used as an alternative to mammalian antibodies normally used in research and immunotherapy. In this study, phage-expressing chicken monoclonal scFv antibody was chosen and characterized with phage display antibody technology. Truncated fragments of SARS-CoV spike protein were cloned in pET-21 vector and expressed in BL-21 Escherichia coli (E. coli) cells. After purification, the purity of these recombinant spike proteins was examined on SDS-PAGE and their identity verified with Western blot analysis using anti-his antibodies and sera from convalescent stage SARS-CoV-infected patients. Using these bacteria-derived proteins to immunize chickens, it was found that polyclonal IgY antibodies in the egg yolk and sera were highly reactive to the immunogens, as shown by Western blot and immunocytochemical staining analysis. A phage displaying scFv library was also established from spleen B cells of immunized chicken with 5 × 10 7 clones. After four panning cycles, the eluted phage titer showed a 10-fold increase. In sequence analysis with chicken germline gene, five phage clones reacted, with large dissimilarities of between 31 and 62%, in the complementarity-determining regions, one dominant phage 4S1 had strong binding to fragment Se-e, located between amino acid residues 456-650 of the spike protein and this particular phage had significantly strong binding to SARS-CoV-infected Vero E6 cells. Based on the results, we conclude that generating specific scFv-expressing phage binders with the phage display system can be successfully achieved and that this knowledge can be applied in clinical or academic research.

Original languageEnglish
Pages (from-to)75-85
Number of pages11
JournalVeterinary Immunology and Immunopathology
Volume117
Issue number1-2
DOIs
Publication statusPublished - May 15 2007

Keywords

  • IgY
  • SARS-CoV
  • scFv-expressing phage binder
  • Spike protein

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Immunology
  • veterinary(all)

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