抗血小板糖蛋白Ⅱb/Ⅲa Fab抗体的原核表达及其生物活性

目的：研制抗血小板膜糖蛋白Ⅱb／Ⅲa Fab抗体。方法：通过问接免疫荧光试验和血小板聚集抑制试验，选取鼠源抗血小板糖蛋白Ⅱb／Ⅲa单克隆抗体(mAb P140)。从分泌该mAb的杂交瘤细胞株(P140)中，克隆到抗体轻链基因和重链Fd段基因，构建原核表达重组质粒p3MH／P140x-Fd，并在XLI-Blu菌株中进行表达。采用钴亲和层析法对P140 Fab抗体进行纯化，用SDS-PAGE、ELISA和Western blot等方法，对P140 Fab抗体进行检测，并通过血小板聚集抑制试验，观察P140 Fab抗体的抗栓活性。结果：SDS-PAGE和Western blot表明，纯化的P140Fab抗体的相对分子质量(Mr)约为47000。ELISA的结果显示，P140 Fab抗体可与人血小板特异性结合。在体外ADP诱导的血小板聚集试验中，P140 Fab抗体对血小板聚集的抑制作用成剂量依赖性，IC50的平均值为16．85mg/L。结论：成功地研制出具有抗栓活性的抗血小板膜糖蛋白Ⅱb／Ⅲa的Fab抗体。

Expression of antibody Fab against platelet Ⅱb/Ⅲa in E.coli and characterization of its biological activity

AIM: To develop a Fab antibody against platelet GPIIb/IIIa. METHODS: A mouse anti-human GPIIb/IIIa monoclonal antibody (mAb) P140 was selected by the indirect immunofluorescence assay (IFA) and platelet aggregation inhibition test. The Fd and light chain genes were cloned from the hybridoma cells secreting the mAb P140. The genes of P140 Fab were inserted into plasmid p3MH to construct recombinant expression plasmid p3MH/P140kappa-Fd. After digestion with the restriction enzyme, the recombinant plasmid was transformed into E.coli XLI-Blue. The expressed product was purified by TALON metal affinity resin. Purified P140 Fab was characterized by SDS-PAGE, ELISA, Western blot and platelet aggregation inhibition test. RESULTS: SDS-PAGE analysis showed that relative molecular mass (M(r)) of P140 Fab was 47x10(3). The results of ELISA, Western blot and platelet aggragation inhibition test indicated that P140 Fab could specifically bind to platelet and inhibit platelet aggragation in dose-dependent manner. The mean value of IC(50) was 16.85 mg/L. CONCLUSION: A soluble anti-platelet GPIIb/IIIa antibody P140 Fab was prepared successfully, which lays the foundation for further clinical application.