用于时间分辨荧光免疫分析的结核分枝杆菌培养滤液蛋白10参照品的制备

Preparation and characterization of reference samples of Mycobacterium tuberculosis culture filtrate protein-10 for time-resolved fluoroimmunoassay

目的通过基因工程技术制备结核分枝杆菌培养滤液蛋白10(CFP10)、链亲和素(SA)/CFP10融合蛋白(包括SA-CFP10、CFP10-SA),筛选灵敏度最高、稳定性最好者作为时间分辨荧光免疫分析法检测(TRFIA)的参考标准品。方法以结核分枝杆菌H37Rv标准株基因组为模板,扩增CFP10基因,将其克隆到pET24b、pET24b-SA、pET21a-SA三种载体中,转化到大肠杆菌Rosetta中进行表达,表达产物经镍离子亲和层析(Ni-NTA)柱纯化,透析法复性。三种重组蛋白用双抗体夹心法TRFIA从灵敏度、稳定性两方面进行评价。结果成功构建了pET24b-CFP10、pET24b-SA-CFP10和pET21a-CFP10-SA三种表达载体,重组蛋白CFP10主要为可溶形式表达,融合蛋白CFP10-SA、SA-CFP10均以包涵体形式存在,Ni-NTA柱纯化后透析复性,纯度均可达90%以上。三种重组蛋白经双抗体夹心TRFIA,CFP10-SA灵敏度最高(0.02μg/L),稳定性最好。结论得到了灵敏度高、稳定性好的TRFIA检测CFP10的参照品CFP10-SA融合蛋白,为研制该结核分支杆菌时间分辨荧光诊断试剂盒,并应用于临床打下了基础。

Objective To prepare reference samples of Mycobacterium tuberculosis culture filtrate protein-10 （CFP-10） and CFP10-streptavidin fusion proteins （CFP10/SA） for time-resolved fluoroimmunoassay （TRFIA）. Methods The CFP10 gene was amplified by PCR from Mycobacterium tuberculosis strain H37Rv and cloned into pET24b, pET24b-streptavidin （SA） or pET21a-SA expression vectors. The recombinant proteins CFP10, CFP10-SA and SA-CFP10 were expressed in Rosetta cells, purified via nickel affinity chromatography and refolded by dialysis. The sensitivity and stability of the resultant proteins as reference samples were evaluated by double-antibody sandwich TRFIA. Results CFP10-SA and SA-CFP10 fusion proteins were expressed as inclusion bodies, whereas CFP10 was expressed in a soluble form. The resultant purity of the 3 recombinant proteins all exceeded 95%. TRFIA results showed that CFP-SA fusion protein possessed the best sensitivity （0.02 μg/L） and stability. Conclusion The reference samples of CFP10 for TRFIA detection have been successfully prepared and can be used in the development of a diagnostic kit for Mycobacterium tuberculosis