title: Construction of non-covalent single-chain Fv dimers for hepatocellular carcinoma and their biological functions.
abstract: OBJECTIVE
  To create new diabodies with improved binding activity to antigen of the variable light - variable heavy (VH-VL) oriented single-chain Fv dimers genes (scFv).
  
  
  METHODS
  The linker between VH and VL genes was shortened to 3-5 amino acid residues and cloned into the vector pCANTAB5E. The recombinant plasmids were transformed into TG1 cells and sequenced. The positive transformed cells were infected by M13K07 helper phage to form human recombinant phage antibodies. Expressed products were identified by SDS-PAGE, Western blotting, size exclusion gel chromatography (SEC), ELISA and immunohistochemistry.
  
  
  RESULTS
  Three scFv (scFv-3, scFv-4, scFv-5) were constructed successfully with binding ability to hepatocellular carcinoma 3.5-6 fold greater than their parental scFv. The single-chain Fv dimer (scFv-5, termed BDM3) with the best binding ability was successfully expressed in Yeast pichlia, as shown by. SDS-PAGE and Western blotting. SEC results suggested the molecular weight of the expressed products was about 61 kDa. Expressed products showed significantly stronger binding to hepatocellular carcinoma cells than scFv, still having 50% binding activity even after 16 h incubation as 37°C. The purified dimers were bound specifically to the tumor antigen of HCC.
  
  
  CONCLUSIONS
  we have generated scFv dimers by shortening a series of linkers to 3-5 amino acid residues in VH-linker-VL orientation, resulting in highly stable and affinity-improved dimeric molecules. These will become an attractive targeting moiety in immunotherapeutic and diagnostic applications for HCC.
authors.affiliation: Cai-Qun Bie, Department of Gastroenterology, Shenzhen Shajing Affiliated Hospital of Guangzhou Medical University, Shenzhen 518104, Guangdong Province, China.
authors.forename: Cai-Qun
authors.initials: CQ
authors.lastname: Bie
authors.forename: Dong-Hua
authors.initials: DH
authors.lastname: Yang
authors.forename: Xu-Jing
authors.initials: XJ
authors.lastname: Liang
authors.forename: Shao-Hui
authors.initials: SH
authors.lastname: Tang