抗脐带间充质干细胞表面分子噬菌体ScFv抗体库的构建及初步鉴定

目的：利用噬菌体展示技术构建抗脐带间充质干细胞表面分子噬菌体ScFv抗体库。方法：收集P3代培养的UC-MSCs免疫BALB/c小鼠,提取其脾细胞总RNA,RT-PCR扩增全套VH和VL基因片段,将其先后克隆入噬菌粒pSEX81中,构建成完整的噬菌体ScFv抗体库。结果:构建的噬菌体ScFv抗体库的库容为2×107cfu,ScFv插入重组率为93％,BstN1酶切图谱呈不同多样性。ScFv抗体库经3轮初步筛选后插入重组率达100％,3个克隆出现了相同的酶切图谱,并且随着筛选次数的增加,输出/输入比明显提高,这说明抗体库得到了特异性富集。结论：成功地构建了抗脐带间充质干细胞表面分子噬菌体ScFv抗体库,这为将来筛选特异性抗体和进一步用于间充质干细胞表面特异性分子研究奠定了坚实的基础。

Construction and Identification of a Single Chain Fv Phage Display Library Against Human Umbilical Cord Mesenchymal Stem Cell

Objective :To construct and identify a ScFv phage display library against human umbilical cord mesenchymal stem cells.Methods: BALB/c mice were immunized with cultured UC-MSCs.After the third immunization,the total RNA was extracted from the spleen cells of the immunized BALB/c mice and purified by affinity chromatography with mRNA Purification Kit.The heavy-chain and light-chain variable region genes(VH and VL) were amplified by PCR using relevant primers.PCR products of VH and VL genes were cloned into the phagemid vector pSEX81 and electroporated into the XL1-Blue strain of E. coli.The ScFv phage display library against human umbilical cord mesenchymal stem cells was constructed and the capacity of library was measured.The library was panned by three cycles and screened with purified UC-MSCs.The percentage of clones containing a full-length scFv-encoding insert and their diversity was determined for unselected and selected libraries.Results: The amplified fragments of VH and VL genes by RT-PCR were about 399bp and 357bp,respectively. VH and VL genes were all successfully cloned into the phagemid vector pSEX81,which were confirmed by the amplication of 786bp full-length scFv fragments by PCR .The ScFv phage display library had a capacity of approximately 2×107 cfu. After three cycles of panning, PCR of plasmid DNA prepared from 15 individual phage clones showed that the recombination rate increased from 93％ to 100％. BstN1 fingerprinting of insert DNA showed that the diversity of clones decreased with increasing rounds of selection.After three rounds of selection, 3 clones showed an identical restriction enzyme pattern. There was a 330-fold enrichment of library phage after 2 rounds of selection and after 3 rounds, a further 8-fold enrichment of library phage was obtained. Conclusion: The ScFv phage display library against human umbilical cord mesenchymal stem cells was successfully constructed.It can be used for succeeding screening of specific antibody against human umbilical cord mesenchymal stem cells and further studying of the cell surface molecules of mesenchymal stem cells.