乙型肝炎病毒表面抗原突变体稳定表达细胞系的建立和抗原性鉴定

目的 探讨乙型肝炎(乙肝)病毒(HBV)表面抗原(HBsAg)阴性HBV感染的分子机制。方法 在对46例HBsAg阴性但血清HBVDNA阳性感染者的S基因序列进行分析的基础上，构建了6株新的HBsAg变异株(4株联合点突变株，2株插入变异株)的EBO-plpp真核表达载体，并转染了COS7细胞，建立了这6株HBsAg变异株的稳定表达细胞系。分别用酶联免疫法(ELISA)和放射免疫法(RIA)对细胞表达的HBsAg抗原性进行检测。结果 除1例插入变异株可检测到较弱的阳性外，其余5株均检测不到HBsAg的存在。结论 新发现的HBsAg联合点突变和氨基酸插入变异，均对HBsAg的抗原性有负面的影响，是造成HBsAg阴性HBV感染的直接原因。

Establishment of stable expression cell lines for HBsAg variants and analysis of antigenicity

Objective To study the mechanism of hepatitis B virus infected patients who is negative for HBsAg. Methods DNA sequences of 46 patients were analyzed. In these patients,HBsAg was negative but HBV DNA was positive and six new HBsAg variants were identified. Four of the six variants were combined point mutants and two were insertion variants.These S genes were subcloned into eukaryotic expression vector EBO-plpp,and the recombinant eukaryotic expression plasmids were transfected into COS7 cells. Cell lines expressing mutant-type HBsAg were obtained. The supernatants were detected by ELISA and RIA. Results Only the two-aminoacid-insertion variants could be detected and the others failed to react with poloyclonal and monoclonal antibodies against HBsAg. Conclusion The results indicated that the point mutations and insertions may result in a conformational change of the S gene,which affect HBsAg antigenicity,suggesting a posible relationship between the variants and the negative conversion of HBsAg of the patients.