[Optimized expression of a single-chain Fv antibody against human asialoglycoprotein receptor and determination of its affinity constant].

Aim: To express and purify a single chain Fv antibody (scFv) C1 against human hepatic asialoglycoprotein receptor (ASGPR) and to determine affinity constant of the purified scFv C1.

Methods: The specific anti-ASGPR phage clone C1 was transfected into E. coli HB2151. The single colony was chosen to be inoculated into 2 x TY medium and shaken (250 r/min) overnight at 37 degrees C. After 1 in 100 dilution in 2 x TY medium and induced for secreted expression, scFv C1 was induced at different concentrations (0.25, 0.5 and 1.0 mmol/L IPTG) overnight at 37 degrees C, 25 degrees C and 20 degrees C, respectively. The supernatant was precipitated with saturated ammonium sulfate and its sediment was analyzed by SDS-PAGE. In addition, the sediment was resuspended in 30 mL PBS and dialyzed against PBS overnight at 4 degrees C. The expressed scFv C1 was purified by Ni(2+) chelating HiTrap HP column and the purity of the purified scFv C1 was identified by SDS-PAGE. Then affinity constant of scFv C1 was determined by noncompetitive enzyme immunoassay.

Results: After induced with 0.5 mmol/L IPTG overnight at 25 degrees C, the amount of expressed scFv C1 increased greatly and its relative molecular mass was about 28,000, and it existed in culture supernant in soluble form. The purity of scFv C1 by nickel-agarose column was above 95% and its yield was about 0.8 mg/L. The affinity constant of the purified scFv C1 was confirmed to be (2.31+/-0.36)x10(-7) mol/L.

Conclusion: The E. coli HB2151 infected with phage C1 clones may express soluble scFv C1 with low affinity, which has potential applications to gene therapy of hepatocellular carcinoma.