去唾液酸糖蛋白受体特异性单链抗体的优化表达及亲和常数的测定

目的:表达及纯化抗去唾液酸糖蛋白受体(ASG-PR)的单链抗体的可溶性,并测定其亲和常数。方法:用噬菌体C1克隆感染E.coliHB2151,挑取单个菌落接种于2×TY培养基中,于37℃震荡培养过夜。将培养物作1∶100稀释并转种后,用终浓度为0.25、0.5、1.0mmol/L的IPTG,分别在37℃、25℃和20℃下诱导表达过夜。取其培养上清,用饱和硫酸铵沉淀后,以120g/LSDS-PAGE分析。另外,将饱和硫酸铵沉淀物用30mLPBS重新溶解、透析除盐后,用Ni2 螯合柱进行纯化,再以120g/LSDS-PAGE鉴定纯化scFvC1的纯度。用非竞争酶免疫法测定scFv的亲和常数。结果:用0.5mmol/LIPTG在25℃诱导过夜,表达的scFvC1的量较多,其相对分子质量(Mr)约为28000,以可溶性的形式存在于培养基中。通过Ni2 亲和柱纯化后scFvC1的纯度在95%以上,产量约为0.8mg/L。scFv的亲和常数为(2.31±0.36)×10-7mol/L。结论:以筛选的C1噬菌体感染E.coliHB2151后可表达低亲和力的可溶性scFv,对肝癌的基因治疗具有潜在的应用价值。

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.