Ribosome display screening of a novel human anti-IgE scFv fragment

Total mRNA was extracted from lymphocytes separated from the peripheral blood of allergic patients, and then variable region of heavy chain (VH) and variable region of light chain (VL) cDNA library were constructed by RT-PCR.  Human scFv templates for rabbit reticulocyte lysate ribosome display were assembled by primers and linker peptide (Gly₄Ser)₃.  mRNA bound in antibody-ribosome-mRNA complexes was recovered using in-situ single primer RT-PCR, and three rounds of anti-IgE scFv DNA were enriched.  The target DNA fragments were double enzyme digested and ligated into plasmid pET22b (+), followed by transformation in E. coli Rosseta (DE3).  Positive clones were screened using clone PCR, Dot blotting and antigen ELISA.  The correct lengths of VH (400 bp) and VL (710 bp) PCR products were obtained.  The expected 1 100 bp ribosome display templates were also observed in agarose gel electrophoresis.  After three rounds of ribosome display target sequences were effectively enriched, leading to a library of 10¹³ members.  Antibodies with the highest ELISA value for IgE were generated in the strain pET-IgE-6.  A human anti-IgE scFv library was successfully constructed as described herein.  Ribosome display using single primer in-situ RT-PCR as the recovery procedure effectively enriched target sequences.  Anti-IgE scFv with high affinity and specificity were identified.  The prepared human anti-IgE scFv fragment might be self-developed to a lead drug for treating asthma.  Our study provides an alternative method for rapid discovery of human antibodies of therapeutic importance.