乙型肝炎表面抗原主要亲水区Ⅱ的抗原性

Antigenicity of major hydrophilic region II of hepatitis B virus surface antigen

目的研究HBsAg主要亲水区Ⅱ的4个氨基酸变异对HBsAg抗原性的影响。方法定点突变HBsAg主要亲水区Ⅱ的4个氨基酸对应的s基因（P120T、C121S、K122I和T123N），构建4个真核表达重组质粒。用重组质粒和表达G145RHBsAg质粒体外瞬时转染HepG2细胞。4种抗体和7种国产HBsAgELISA诊断试剂盒检测转染细胞上清液和细胞裂解液中变异HBsAg的免疫反应性，免疫荧光检测单克隆抗体与转染细胞内变异HBsAg的免疫反应性。结果成功构建了表达HBsAg主要亲水区Ⅱ的4个氨基酸变异的重组质粒，P120T、C121S、K122I和T123N变异HBsAg的免疫反应性比野生HBsAg低，T123N变异导致HBsAg存在分泌障碍。结论HBsAg主要亲水区Ⅱ的4个氨基酸对维持HBsAg的空间构象和抗原性具有重要作用。

Objective To study whether the substitutions at the major hydrophilic region Ⅱ （MHRH） of hepatitis B surface antigen （HBsAg） will impair the antigenicity of HBsAg. Methods Four recombinant plasmids expressing mutant HBsAg （mtHBsAg） P 1120T, C 121 S, K 122I and T123N were constructed. HepG2 cells were lransfected with the four plasmids and a plasmid expressing G145R HBsAg. The immunoreactivity of the cells expressing mtHBsAg with P1120T, C121S, K122I, T123N and GI45R were detected by immunofluorescence （IF） staining and ELISA with 4 antibodies and 7 HBsAg diagnostic kits respectively. Results mtHBsAg with PI20T was recognized by mAbl and mAb2. mtHBsAg with C121S and K122I was not recognized by any mAbs, mtHBsAg with T123N in lysates was recognized by mAb2, but not recognized in the supernatants. Conclusion Substitutions at amino acid positions 120-123 of HBsAg strongly impaired the antigenicity of HBsAg, a fact that was not appreciated previously.