骆驼纳米抗体随机突变噬菌体展示文库的构建与质量分析

Construction and quality analysis of phage display library for random mutagenesis of camel nanobody

目的构建人工突变的噬菌体展示文库并与天然噬菌体展示文库序列对比,进而对人工突变的噬菌体展示文库的质量进行科学评价,为纳米抗体的进一步改造提供鉴。方法对结合人卵泡刺激素受体(FSHR)的纳米抗体的抗原互补决定区3(CDR3)进行NNY定点饱和突变,合成VHH06-ΔCDR3随机突变DNA。将突变DNA序列连接到载体pMECS上,构建VHH06-ΔCDR3突变噬菌体展示文库。通过DNA测序和分析,比较该文库与FSHR免疫的VHH噬菌体展示文库的多样性和CDR3区的氨基酸分布。采用FSHR对文库进行6轮亲和筛选,测定筛选后克隆的富集程度。结果按照NNY突变原则,合成了长度为16个氨基酸的CDR3随机突变基因库。成功构建了库容量为7.36×10^8 cfu/ml的VHH06-CDR3随机突变噬菌体展示文库。多克隆与单克隆phage酶联免疫吸附实验结果显示,经过6轮筛选,输出噬菌体与FSHR的结合明显得到富集,但获得的克隆与FSHR没有明显结合。结论 VHH06-ΔCDR3随机突变噬菌体展示文库尽管具有序列多样性,但由于CDR3缺乏功能多样性,导致其在亲和筛选中不利于获得目标抗体。

Objective To construct phage display antibody library of artificial mutation to compare with the sequence of the natural phage display antibody library. To scientifically evaluate the quality of the artificial mutation of phage display library, and provide some references for the further transformation of the nanobody. Methods Using random mutation method, NNY fixed-point santuration mutation was performed on combine the follicle-stimulating hormone receptor(FSHR) of human nanobody. The mutant DNA sequence was connected to the vector pMECS to construct the phage display library of VHH06-CDR3 random mutation. By sequencing and analysis of DNA sequences, the diversity of the library and the amino acid distribution of CDR3 were compared between mutation library and the immune library of FSHR. The degree of enrichment of cloning was determined by six rounds of affinity screening. Results According to the NNY mutation rule ,the CDR3 regions with 16 amino acids by random mutations was synthesized and the VHH-CDR3 random mutant phage display library was constructed . The phage display library of VHH06-CDR3 random mutant size was 7.36×10^8 cfu/ml. Polyclonal and monoclonal phage ELISA showed that after six rounds of screening, the output phage and the combination of FSHR showed obvious enrichment, but there was no clone combined with FSHR. Conclusions Although the VHH06-CDR3 mutant phage display library has sequence diversity, it is not conducive to obtaining target antibodies in affinity screening due to the lack of functional diversity of CDR3.