乙型肝炎病毒表面抗原一级结构多态性的初步研究

The study on polymorphism of hepatitis B virus surface antigen preliminary structure in patients with chronic HBV infection

目的 研究慢性乙型肝炎患者体内乙型肝炎病毒 (HBV)表面抗原一级结构的多态性。方法 设计特异性引物 ,自 7例慢性乙型肝炎患者血清中扩增S基因全长或全基因组片段 ,TA克隆法克隆到T载体中 ,随机选择克隆测序。结果 共 2 0个克隆被测序。 2 0个克隆全S蛋白的总一致率仅为 3 2 .0 % ,13株全长为 40 1氨基酸残基的克隆氨基酸一致率为 82 .5 %。患者血清中发现2株克隆编码截短型表面抗原中蛋白 ,在前S1或前S2的免疫决定区或可能的肝细胞结合部位均发现缺失突变。结论 慢性乙肝患者体内存有HBV准种群 ,病毒编码的截短型表面抗原中蛋白可为HBV诱导原发性肝癌提供一种途径 ,应加强对HBsAg一级结构多态性的研究。

Aim To study the amino acid sequence polymorphism of hepatitis B virus (HBV) surface antigen in the patients with chronic HBV infection.Methods Specific primers were designed and synthesized according to the published HBV DNA sequence.The full S region and the full length of HBV genomic DNA were amplified by polymerase chain reaction (PCR) technique from the serum of 7 patients with chronic HBV infection.The PCR products were ligated into pGEM Teasy vectors,and the cloned DNA fragments were sequenced.The whole S amino acid sequences from recombinant plasmids had been compared.Results 20 clones of target regions were sequenced.Truncated carboxytermini of middle HBsAg (MHBs t) coding sequences were found in quasispecies groups.Deletions in immunodominant epitope or potential hepatocyte binding site in preS1 or preS2 peptides were observed.The totally consistency of the amino acid sequences of these 20 clones is only 32.0%. The consistency of the 13 clones with 401 aa is 82.5%.Conclusion There is HBV quasispecies population in the patients with chronic HBV infection.MHBs t encoded by HBV truncated form of DNA may provide a alternative pathway of hepatocarcinogenesis. The polymorphism of HBsAg preliminary structure should be thoroughly studied.