截短形式弓形虫SAG1抗原在大肠杆菌中的可溶性高效表达、纯化及免疫反应性鉴定

目的 在大肠杆菌中以可溶性形式高效表达弓形虫SAG1基因的截短片段，并进行纯化及免疫反应性鉴定。方法 利用，VcoI、HindⅢ双酶切，从本室建立的pET-30a( )-SAG1重组质粒中获取SAG1基因的截短片段，并将目的片段连接到经同样双酶切的质粒pET32a中，构建表达重组质粒pET-32a( )-trSAG1。将重组质粒转入E．coli BL21中并进行诱导表达。表达蛋白经Ni—NTA agarose纯化后，Western—blotting分析其免疫反应性。结果 成功构建重组质粒pET-32a( )-trSAG1，通过IPTG诱导得到了以可溶性形式表达的重组SAG1蛋白，相对分子质量40000，Western—blotting结果显示纯化的重组蛋白具有良好的免疫反应性，ELISA试验表明重组SAG1蛋白能被弓形虫免疫兔血清及弓形虫感染人血清识别。结论 在大肠杆菌中以可溶性形式高效表达了弓形虫SAG1基因的截短片段，表达蛋白能被弓形虫免疫兔血清及弓形虫感染人血清识别，有望成为一种有价值的诊断抗原。

Efficient soluble expression, purification and identification of the truncated SAG1 gene of Toxoplasma gondii in Escherichia coli]

OBJECTIVE: To express truncated SAG1 gene in Escherichia coli to obtain purified recombinant SAG1, and identify the immunoreactivity of the product. METHODS: The plasmid pET-30a(+)-trSAG1 was constructed, which was cut by Nco I and HindIII to obtain truncated SAG1 gene and inserted into pET-32a(+) cut by the same two restriction enzymes. After identification by restriction enzymes, the plasmid pET-32a(+)-trSAG1 was transformed into E.coli BL21, and the soluble product induced by 0.1 mmol/L IPTG for 4 hour before purification with Ni-NTA agarose, followed by identification of the purified recombinant protein with SDS-PAGE, Western-blotting and ELISA. RESULTS: Recombinant pET-32a(+)-trSAG1 was successfully constructed and high level of truncated SAG1 expression achieved in E.coli. SDS-PAGE showed that the expressed protein was approximately 40,000 in size and expressed in a soluble form that could be easily purified by Ni-NTA agarose. Western-blotting demonstrated that the purified product could be specifically recognized by sera from rabbits immunized with native antigen of T.gondii, and could also be recognized, as shown by ELISA, by sera from human with T.gondii infection. CONCLUSIONS: The truncated SAG1 gene was successfully expressed in E.coli in a soluble form, and the recombinant protein may be of value in the diagnosis of toxoplasmosis.