结核病DNA疫苗pVAX1/ESAT-6的构建、鉴定及免疫效应评价

Construction, identification and immunoreactivity of Mycobacterium tuberculosis DNA vaccine pVAX1/ESAT-6 plasmid

目的构建结核病DNA疫苗pVAX1/ESAT-6并探讨其诱导的免疫效应。方法将扩增自结核杆菌基因组的ESAT-6基因装入pVAX1载体构建pVAX1/ESAT-6重组质粒;经酶切、测序鉴定后,利用阳离子聚合物介导将重组质粒pVAX1/ESAT-6转染Hela细胞,分别以RT-PCR法检测ESAT-6 mRNA的表达、间接免疫荧光法检测ESAT-6蛋白表达。重组质粒经体内电转染免疫小鼠后,采用ELISA法测定小鼠血清中IFN-γ及抗ESAT-6特异性抗体IgG的水平;流式细胞术检测小鼠淋巴细胞增殖水平;ELISPOT检测产生IFN-γ的淋巴细胞频数。结果构建的重组质粒pVAX1/ESAT-6经双酶切于3000 bp和300 bp处各见1条带,测序结果显示插入序列与ESAT-6基因序列无差异。重组质粒转染Hela细胞后,RT-PCR产物经琼脂糖凝胶电泳于约300 bp处见目的条带,间接免疫荧光检测显示特异性绿色荧光。重组质粒免疫小鼠后,血清中抗ESAT-6特异性抗体IgG水平较对照组(空质粒组和生理盐水对照组)明显升高;血清中IFN-γ水平、小鼠脾淋巴细胞增殖水平及产生IFN-γ的淋巴细胞数明显均高于对照组(空质粒组和生理盐水对照组)。结论成功构建了结核病DNA疫苗pVAX1/ESAT-6,该疫苗可有效诱导小鼠产生特异性细胞免疫和体液免疫效应。

Objective To construct a Mycobacterium tuberculosis DNA vaccine pVAX1/ESAT- 6 plasmid and investigate its immunoreactivity. Methods The ESAT-6 gene fragment amplified from Mycobacterium tuberculosis genome was inserted into pVAX1 vector to construct the recombinant plasmid pVAX1/ESAT-6, which was identified by restriction enzyme digestion and sequencing. The recombinant plasmid was transformed into Hela cells using Sofast Transfection reagent, and the cellular expressions of ESAT- 6 mRNA and protein were analyzed by RT- PCR and immunofluorescence assay, respectively. The recombinant plasmid pVAX1/ESAT-6 was also transfected into mouse by electronic pulse method, and the mouse serum IFN-γ level and anti- ESAT- 6 IgG antibody level were detected by ELISA, mouse lymphocyte proliferation assessed with flow cytometry, and IFN- γ- secreting lymphocytes counted using ELISPOT. Results Double restriction- enzyme digestion and sequencing showed that the inserted fragment in the recombinant plasmid pVAX1/ESAT-6 was identical to ESAT-6 gene with an inframe insertion. RT- PCR yielded the target band as expected on agarose gel, and immunofluorescence assay of the transfected cells showed specific green fluorescence signals. The mice transfected with the recombinant plasmid showed significantly elevated serum level of anti-ESAT-6 IgG antibody and increased serum IFN-γ level, spleen cell proliferation, and number of IFN-γ-secreting lymphocytes. Conclusion The Mycobacterium tuberculosis DNA vaccine pVAX1/ESAT-6 plasmid we constructed can induce high levels of cellular and humoral immunoreactivity in mice.