一种新的HBeAg阴性慢性乙型肝炎病毒变异机制

A novel mechanism of hepatitis B virus mutation in hepatitis B e antigen negative chronic hepatitis B infection

目的检测HBV核心启动子区（CP）基因变异方式。方法自HBV慢性感染患者血清中提取HBVDNA，扩增CP区域序列，克隆入pMD19T载体，选择阳性克隆进行DNA测序，与已知HBV基因相应序列比较患者体内HBV基因变异位点以及变异形式。结果自21例患者中共挑选74个克隆测序，54个克隆中病毒基因序列CP区发生大段缺失突变，长度达234个核苷酸，另有1个克隆发生245个核苷酸缺失突变。缺失突变区域包括CP区、HBeAg起始密码子和直接重复序列（DR）I区，命名为CP缺失突变，发生CP缺失突变的病毒株同时存在A1585T替换突变，这两个部位的突变具有联动特征。结论观察到一种导致HBeAg阴性慢性乙型肝炎的新方式，即CP、HBeAg起始密码子缺失突变，并提出一种简明的CP缺失检测方式。

Objective To investigate mutation patterns in core promoter （CP） region of hepatitis B virus （HBV）. Methods HBV DNA was extracted from sera of patients with chronic HBV infection. The CP sequence was amplified by polyrnerase chain reaction （PCR） and cloned into pMD19 T vector. The positive clones were then sequenced. The sequences were compared with known HBV genome in GenBank to identify the mutation sites and patterns of patients with chronic HBV infection. Results There were 74 clones from 21 patients with chronic HBV infection which were sequenced. The sequence corrtparisons showed that there was a 234-nucleotide deletion in CP region of HBV genome in 54 clones and a 245 nucleotide deletion in one clone. These deletion regions included CP, HBeAg initiation eodon and direct repeat sequence （DR） I regions, which named CP deletion （CPD）. A1585T replacement mutation was also found in HBV strain with CPD, which indicated that there was linkage between these two mutations. Conclusions A novel mechanism of HBeAg negative chronic hepatitis B is observed, which includes deletions of CP and HBeAg initiation codon. Meanwhile, a simple and useful PCR method is developed to detect CPD.