应用核糖体展示技术高效筛选人源抗IgE单链抗体

本研究从哮喘患者外周血分离淋巴细胞、提取总mRNA,采用RT-PCR技术分别构建重链可变区VH(variable region of heavy chain)和轻链可变区VL(variable region of light chain)cDNA库,然后通过连接肽(Gly4Ser)3和特定引物将VH和VL cDNA基因组装成人源单链抗体(scFv)核糖体展示模板基因库。应用兔网织红细胞核糖体展示技术,单引物原位反转录技术,经3轮展示富集并回收针对人源IgE蛋白(免疫球蛋白E)的目的单链抗体基因;回收的抗体基因经双酶切后与pET22b(+)载体连接,转化至E.coli Rosseta(DE3)宿主细胞,应用菌落PCR结合Dot blotting技术快速鉴定阳性克隆,抗原ELISA法进一步鉴定阳性克隆。VH和VL基因库得到正确的构建,长度分别为400和710 bp,库容为1013。核糖体展示模板构建正确,长度为1 100 bp。该基因库经过3轮针对IgE蛋白的核糖体展示,目的基因得到了有效富集和回收。经过高效克隆、表达和鉴定,确定1株针对人IgE蛋白显示最强亲和力的阳性克隆菌pET-IgE-6。经测序和序列分析证实该单链抗体为人源抗体,序列未见国内外报道。结果表明,采用患者外周血构建人源抗体基因库,结合核糖体展示技术,可以成功获得高亲和力的人源单链抗体分子。该技术路线为快速获得具有药用价值的人源抗体提供了参考。

Ribosome display screening of a novel human anti-IgE scFv fragment

Total mRNA was extracted from lymphocytes separated from the peripheral blood of allergic patients,and then variable region of heavy chain(VH) and variable region of light chain(VL) cDNA library were constructed by RT-PCR.Human scFv templates for rabbit reticulocyte lysate ribosome display were assembled by primers and linker peptide(Gly4Ser)3.mRNA bound in antibody-ribosome-mRNA complexes was recovered using in-situ single primer RT-PCR,and three rounds of anti-IgE scFv DNA were enriched.The target DNA fragments were double enzyme digested and ligated into plasmid pET22b(+),followed by transformation in E.coli Rosseta(DE3).Positive clones were screened using clone PCR,Dot blotting and antigen ELISA.The correct lengths of VH(400 bp) and VL(710 bp) PCR products were obtained.The expected 1 100 bp ribosome display templates were also observed in agarose gel electrophoresis.After three rounds of ribosome display target sequences were effectively enriched,leading to a library of 1013 members.Antibodies with the highest ELISA value for IgE were generated in the strain pET-IgE-6.A human anti-IgE scFv library was successfully constructed as described herein.Ribosome display using single primer in-situ RT-PCR as the recovery procedure effectively enriched target sequences.Anti-IgE scFv with high affinity and specificity were identified.The prepared human anti-IgE scFv fragment might be self-developed to a lead drug for treating asthma.Our study provides an alternative method for rapid discovery of human antibodies of therapeutic importance.