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利用末端重叠ＰＣＲ法和定点突变技术，获得了去除Ｎ－连接多糖结构的乙肝表面抗原Ｓ突变基因，将乙肝表面抗原Ｓ－蛋白中结合Ｎ－连多糖结构序列Ａｓｎ－Ｘ－Ｔｈｒ中的第１４８苏氨酸的密码子ＡＣＴ，改变为编码甘氨酸的密码子ＧＧＴ。构建了该突变基因的表达载体并在ＣＨＯ细胞中表达，筛选到两株表达水平较高的细胞系。对其中的一株细胞系Ｃ４１的表达产物做了初步纯化和鉴定。纯化样品经ＳＤＳ－ＰＡＧＥ电泳分析，只含有２３ｋＤ一条蛋白带，而对照原基因ＣＨＯ细胞的表达产物则含有２３ｋＤ、２７ｋＤ和３０ｋＤ三条蛋白带，证实经人工修饰后其哺乳动物细胞表达产物不再含有糖基，纯化样品在电镜下可清楚地显示２２ｎｍ的球形颗粒。单克隆抗体反应谱分析发现，ＣＨＯ细胞表达的无糖ＨＢｓＡｇ与含糖ＨＢｓＡｇ的抗原表位存在明显差别。
By using terminal overlapping PCR and site-directed mutagenesis, the mutant gene of hepatitis B surface antigen S with N-linked polysaccharide structure was obtained, and the sequence of hepatitis B surface antigen S-protein binding to the 148th Asn-X-Thr The codon ACT of threonine is changed to codon GGT which codes for glycine. The expression vector of the mutant gene was constructed and expressed in CHO cells. Two cell lines with higher expression levels were selected. One of the cell lines C41 expression products were initially purified and identified. The purified sample was analyzed by SDS-PAGE and contained only one protein band of 23 kD while the control product of CHO cells contained three bands of 23 kD, 27 kD and 30 kD, demonstrating that the mammalian cell expressed product no longer contained Sugar-based, purified samples clearly show spherical particles of 22 nm under electron microscopy. Monoclonal antibody response spectrum analysis found that there is a significant difference between the expression of sugar-free HBsAg in CHO cells and the epitope of sugary HBsAg.