Bacterial meningitis is a severe disease that is fatal to one-third of patients. The major cause of meningitis in neonates is Escherichia coli (E. coli) K1. This bacterium synthesizes an outer membrane protein A (OmpA) that is responsible for the adhesion to (and invasion of) endothelial cells. Thus, the OmpA protein represents a potential target for developing diagnostic and therapeutic agents for meningitis. In this study, we expressed recombinant OmpA proteins with various molecular weights in E. coli. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was performed to check the molecular size of OmpA's full length (FL) and truncated proteins. OmpA-FL protein was purified for immunizing chickens to produce immunoglobulin yolk (IgY) antibodies. We applied phage display technology to construct antibody libraries (OmpA-FL scFv-S 1.1 × 107 and OmpA-FL scFv-L 5.01 × 106) to select specific anti-OmpA-FL scFv antibodies; these were characterized by their binding ability to recombinant or endogenous OmpA using ELISA, immunofluorescent staining, and confirmed with immunoblotting. We found 12 monoclonal antibodies that react to OmpA fragments; seven scFvs recognize fragments spanning amino acid (aa) residues 1-346, aa 1-287, aa 1-167, and aa 60-192, while five scFvs recognize fragments spanning aa 1-346 and aa 1-287 only. Two fragments (aa 246-346 and aa 287-346) were not recognized with any of the 12 scFvs. Together, the data suggest three antigenic epitopes (60 aa-160 aa, 161 aa-167 aa, 193 aa-245 aa) recognized by monoclonal antibodies. These scFv antibodies show strong reactivity against OmpA proteins. We believe that antibodies show promising diagnostic agents for E. coli K1 meningitis.

Original languageEnglish
Pages (from-to)5285-5299
Number of pages15
JournalApplied Microbiology and Biotechnology
Issue number13
Early online dateApr 26 2019
Publication statusPublished - Jul 4 2019


  • Antigenic epitopes
  • Bacterial meningitis
  • Escherichia coli strain K1
  • Outer membrane protein A (OmpA)
  • Phage display technology
  • Single-chain variable fragment (scFv) antibody
  • Immunization
  • Bacterial Outer Membrane Proteins/genetics
  • Enzyme-Linked Immunosorbent Assay
  • Epitopes/immunology
  • Recombinant Proteins/immunology
  • Immunoglobulins/immunology
  • Escherichia coli/genetics
  • Chickens/immunology
  • Animals
  • Antibodies, Monoclonal/immunology
  • Escherichia coli Infections/diagnosis
  • Single-Chain Antibodies/genetics
  • Cell Surface Display Techniques
  • Female
  • Meningitis/diagnosis

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Biotechnology


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