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将抗癌胚抗原（ＣＥＡ）单克隆抗体的重链可变区与人的恒定区（Ｃγ３） 连接， 制备抗癌胚抗原嵌合重链用于放免治疗及其他导向治疗， 可减少人抗鼠抗体反应（ＨＡＭＡ） 。为纯化及核素标记抗体， 将嵌合重链基因与核心链霉亲和素基因融合。融合基因在大肠杆菌得到高效表达， 表达量占菌体总蛋白的２４ ％ 。ＳＤＳＰＡＧＥ 和蛋白质印迹图谱显示表达产物分子量为７０ ｋＤ， 与其基因编码蛋白质的理论推算值相符。以ＨＲＰ标记的生物素作为抗体进行蛋白质印迹， 在７０ ｋＤ 处可见表达条带， 表明融合蛋白能特异性地与生物素结合， 使嵌合重链经生物素柱进行廉价纯化成为可能。表达产物在胞内主要以不溶性的包含体存在， 经变性和复性处理后， ＲＩＡ 表明表达产物具有结合其特异性抗原ＣＥＡ的能力。
Anti-carcinoembryonic antigen (CEA) monoclonal antibody heavy chain variable region and human constant region (Cγ3) connected to prepare anti-CEA chimeric heavy chain for radiotherapy and other targeted therapy can reduce human anti-mouse Antibody response (HAMA). To purify and nuclide-labeled antibodies, the chimeric heavy chain gene is fused to the core streptavidin gene. The fusion gene was highly expressed in E. coli, and the expression amount accounted for 24% of the total bacterial protein. SDS-PAGE and Western blot showed that the molecular weight of the expressed product was 70 kD, which was consistent with the theoretical deduced value of the gene encoding protein. Western blotting with HRP-labeled biotin as an antibody showed expression bands at 70 kD, indicating that the fusion protein specifically binds to biotin, making it possible to inexpensively purify the chimeric heavy chain via a biotin column. The expression product exists in the intracellular mainly as an insoluble inclusion body. After denaturation and refolding, the RIA indicates that the expressed product has the ability of binding to its specific antigen CEA.