【摘要】 目的构建全人源化食管癌噬菌体单链抗体库,从中筛选Eca-109细胞特异性单链抗体。方法取食管癌病人癌肿周围淋巴结作为B细胞的来源,提取总RNA,用RT-PCR的方法获得抗体可变区基因cDNA文库。首先分别网格筛选确定扩增VH和VL基因片段的引物对,以cDNA为模板扩增VH和VL基因片段,再以它们为模板分别扩增VH-linker与VL-linker,用SOE-PCR技术将后者组装成scFv,再引入酶切位点SfiI和NotI。将scFv基因克隆入噬菌粒载体pCANTAB-5E后电转入EcoliTG1,经抗体表达的辅助噬菌体M13KO7超感染,构建单链抗体库。PCR鉴定阳性重组菌EcoliTG1中scFv的插入率,1.5%琼脂糖凝胶电泳鉴定SfiI和NotI双酶切质粒的结果。从该抗体库中筛选特异性识别Eca109细胞的单链抗体,将阳性克隆菌转化EcoliHB2151进行可溶性表达。抗体亲和层析纯化后经SDS-PAGE、West-ern blot鉴定,通过ELISA法、免疫组化法、免疫细胞化学鉴定其与人食管癌细胞的结合的特异性。结果食管癌周围淋巴结总RNA的提取琼脂糖电泳结果中可见清晰的28S、18S条带;VH基因的大小约为450bp,VL基因为350bp,组装后的scFv基因约为850bp。用pUC18标准质粒测定转化效率达到108cfu.μg-1。scFv的阳性插入率为91.7%(22/24)。在筛选过程中,食管癌噬菌体单链抗体得到富集,收获率逐轮得到提高,第4轮为第1轮的141倍;SDS-PAGE与Western blot结果显示抗体分子量为30ku左右,在Ecoli HB2151中实现了单链抗体的可溶性表达。免疫组织化学结果提示可溶性抗体仅食管癌组织着色,而肝癌、胃癌组织不染色。免疫细胞化学结果表明此可溶性抗体可使食管癌细胞Eca109染色。细胞ELISA测定结果显示可溶性抗体具有较高的特异性,能与Eca109细胞结合,而不与胃癌BGC-823和NHEEC结合。结论从食管癌病人癌肿周围淋巴结成功地构建人源食管癌噬菌体单链抗体库,并从中筛选到食管癌特异性抗体。更多还原

【Abstract】 Aim To construct human phage single-chain antibody library associated with esophageal cancer and to screen the specific scFv against Eca109 cells from the liberary. Methods Metastatic periesophageal lymph nodes of esophageal cancer patients were used as the B cells source, the total RNA of these B cells was extracted and prepared as the template of RT-PCR. First, we screened graticulely two pairs of primers of the heavy and light regions separately, then the V_H and V_L fragments were first amplified from the cDNA by the polymerase chain reaction (PCR). Second, the V_H-linker and V_L-linker were amplified from the V_H and V_L fragments. Last, the V_H-linker and V_L-linker were assembled into scFv gene fragments by SOE-PCR,and then Sfi I and Not I restriction site were inlet in it. ScFv gene was cloned into the pCANTAB-5E phagemid. Phagemids were introduced into E.coli TG1 by electrotransformation, followed by rescue of antibody-expressing phage using M13K07 helper-phage superinfection. Recombinant scFv phage library was constracted and PCR was used to identify the insert ratio of scFv antibodies library. Results of SfiI/Not I double digestion reaction positive insert clone were identified by 1.5% agarose gel electrophoresis. The phage library was panned with NHEEC and Eca109 cancer cells in suspension for four rounds. Strongly positive recombinant phage clones were used to infect E.coli HB2151. Expression of soluble scFv was induced by IPTG. Soluble scFv from periplasm were purified by affinity chromatography and identified by SDS-PAGE and Western blot. Cell ELISA , immunohistochemical staining and immunocytochemical staining were used to identify the activity of the soluble scFv. Results The result of agarose gel electrophoresis showed that total RNA of these B cells had two bands of 28 S and 18 S. The size of V_H fragment is about 450 bp,V_L fragment is about 350 bp and scFv is about 850 bp. The competence is 108 cfu·μg-1 pUC18 DNA. Randomly digestive reac-tion showed that the positive insert ratio was 91.7% (22/24). After four rounds of panning, the fourth phage yield is 141 times as much as that of the first one. SDS-PAGE and Western blot showed that the MW of the soluble scFv was about 30 ku and the brand of 30 ku was stained. Immunohistochemical staining showed strong stainning of the tissue of esophageal cancer, but not the liver and gastric cancer tissue. Immunocytochemical staining showed significant staining of the esophageal cancer line Eca109. The result of cell ELISA assay revealed that soluble scFv had highly specific and could combined with Eca109 cells, but not with BGC-823 and NHEEC. Conclusion A human scFv phage display library associated with esophageal cancer has been constructed successfully and the specific scFv antibody against Eca109 has been identified from the liberary.更多还原