戊型肝炎病毒诊断抗原的克隆表达及抗原性初步鉴定

Cloning and expression and preliminary antigenicity identification for the diagnostic antigen of hepatitis E virus

目的 克隆、表达与纯化硫氧还原蛋白-戊型肝炎病毒（HEV）诊断抗原（命名为N5）,并对其抗原性和血清学检测效果初步评价。方法 根据GenBank上HEV-ORF2以及ORF3羧基端的基因序列,按照大肠埃希菌密码子偏好表进行密码子优化,全基因合成后插入M48原核表达载体中,在大肠埃希菌中表达融合硫氧还蛋白的融合蛋白N5。并利用亲和层析技术对融合蛋白进行纯化,用Western blot技术评价其抗原性,并利用实验室和临床检测确定的HEV感染阴、阳性血清评价其血清学检测效果。结果 成功构建表达N5诊断抗原的重组质粒;高水平表达并纯化获取纯度高、浓度大的可溶性诊断抗原;Western blot结果显示融合蛋白N5可与HEV IgM抗体阳性血清特异性结合,具有良好的抗原性;以融合蛋白N5作为捕获抗原,建立间接ELISA,对病原检测和临床诊断确诊的40份戊型肝炎病例血清和40份健康人血清进行检测,其灵敏度和特异度分别为95%（38/40）和90%（36/40）。结论 成功构建了可表达融合硫氧还蛋白的HEV诊断抗原的重组质粒,并获得表达量高、抗原性强的可溶性融合蛋白N5,可应用于HEV血清学诊断,且有良好的应用前景。

Objective To clone,express and purify thioredoxin （named as N5）,a specific diagnostic antigen of hepatitis E virus （HEV）, and to initially evaluate its antigenicity and serological test performance. Methods Based on the gene sequences of HEV-ORF2 and carboxyl terminal ORF3 on GenBank,the codon was optimized by the Escherichia coli codon preference,inserted it into prokaryotic expression vector M48 following total gene synthesization,and expressed in Escherichia coli fusion protein N5 recombined with Thioredoxin （TRX）. Fusion protein was purified in affinity chromatography,evaluating its antigenicity with Western blot technology,then evaluating its serological test performance using the negative and positive serum samples confirmed of HEV infection with laboratory and clinical tests. Results The recombinant plasmid expressing N5 diagnostic antigen was successfully established;high-level expression and purification to obtain soluble diagnostic antigens;Western blot results indicating fusion protein N5 can be bound specifically with the serum of HEV IgM antibody positive,showing satisfactory antigencity;using fusion protein N5 as the capture antigen to build indirect ELISA,testing 40 serum samples of HEV cases confirmed by pathogen detection and clinical diagnosis and 40 serum samples of healthy people,with the sensitivity and specificity of 95%（38/40） and 90%（36/40） respectively. Conclusion Recombinant plasmid expressing the HEV diagnostic antigen recombined with thioredoxin was successfully established,and soluble fusion protein N5 was obtained with high expression and strong antigenicity,promising in its future applications.