To rapidly select potent anti-VSTM1-v2 scFv (single-chain antibody fragment) by construction and screening of a humanized scFv library in which a murine VH-CDR3 library was grafted onto a human scFv framework. A murine VH-CDR3 library was amplified from anti-VSTM1-v2 murine cDNA and grafted on human scFv (VH3-VK1) framework. Anti-VSTM1-v2 scFv templates were selected and enriched through ribosome display, TA-cloned into expression vector, and transformed into BL21 (DE3) for soluble expression of target scFv. A total of 1000 clones were randomly picked. Positive ones were first identified using colony PCR, indirect ELISA, Western blotting and then verified with sequencing and dose response ELISA. At last an anti-VSTM1-v2 humanized scFv with good binding affinity (EC50 = 21.35 nmol x L(-1)) was selected from the humanized library of 10(12) members generated in this study. This scFv antibody might have potential applications. This study provides a new approach for rapid screening of humanized antibodies.

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 1,000 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 10(13) 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.