幽门螺杆菌临床菌株尿素酶B亚单位原核表达系统的构建及其重组蛋白免疫性的鉴定

目的：克隆幽门螺杆菌（Hp）ureB基因并构建其原核表达系统。方法：采用高保真PCR从幽门螺杆菌临床分离菌株Y06中扩增ureB基因，T-A克隆后测定核苷酸序列，构建pET32a的ureB表达载体，在E.coli BL21DE3宿主菌中用不同浓度的IPTG诱导表达，采用Hp全菌抗体的Western blot和兔抗融合蛋白血清的免疫扩散试验鉴定其免疫性。结果：所克隆的ureB基因与报道的相应核苷酸序列同源性为96.88％-97.82％，氨基酸序列同源性高达99.65％-99.82％。pET32a-ureB-BL21DE3系统的UreB融合蛋白表达量高达细菌总蛋白的40％左右。UreB融合蛋白能与Hp全菌抗体发生结合反应，免疫家兔能获得高效价抗体。结论：本研究成功地构建了Hp ureB高效表达系统，所表达的UreB融合蛋白有良好的免疫原性和免疫反应性，可作为Hp瘤苗的抗原。

Construction of prokaryotic expression system of ureB gene from a clinical isolate of Helicobacter pylori and identification of immunogenicity of the fusion protein

Objective: To clone Helicobacter pylori ureB gene, to construct prokaryotic expression system of the gene and to identify immunogenicity of the fusion protein. Methods: The ureB gene from a clinical isolate Y06 of H.pylori was amplified by high fidelity PCR. The nucleotide sequence of the target DNA amplification fragment was sequenced after T-A cloning. The expression vector pET32a with inserted ureB gene was constructed. ureB fusion protein was expressed in E.coli strain BL21DE3 induced by IPTG at different dosages. Western blot using antibody against whole cell of H.pylori as well as immunodiffusion assay using antiserum of rabbit against the fusion protein was applied to determine immunogenicity of the fusion protein. Results: In comparison with the reported corresponding sequences, the homology of nucleotide sequence of the cloned ureB gene was from 96.88%~97.82%, while the homology of its putative amino acid sequence was as high as 99.65%~99.82%. The expression output of UreB protein in pET32a-ureB-BL21DE3 system was approximately 40% of the total bacterial proteins. UreB protein was able to combine with antibody against whole cell of H.pylori and induce rabbit to produce high titer antibody after the animal was immunized with the protein. Conclusion: An expression system with high efficiency of H.pylori ureB gene has been established successfully. The expressed UreB protein with satisfactory immunogenicity and immunoreactivity can be used as antigen in H.pylori vaccine.