Kato J, Hasegawa K, Torii N, Yamauchi K, Hayashi N
Department of Medicine, Institute of Gastroenterology, Tokyo Women's Medical College, Japan.
Hepatology. 1996 Mar;23(3):389-95. doi: 10.1053/jhep.1996.v23.pm0008617416.
To identify the mechanisms of viral persistence in patients with chronic hepatitis B after the acquisition of anti-hepatitis B surface antigen antibodies (antiHBs), we serially analyzed the nucleotide sequence of the envelope region in a cohort of infected patients. Four patients with histological diagnoses of chronic hepatitis B who had at least 5 years of observance by our hospital staff were studied. All but one showed normalization of serum alanine aminotransferase (ALT) concentration after clearance of the hepatitis B surface of antigen (HBsAg) and the appearance of anti-HBs. Hepatitis B virus (HBV) DNA was still detectable by polymerase chain reaction (PCR) amplification assay in serum specimens from two patients, even in the presence of circulating anti-HBs. The envelope gene was amplified by PCR in serum samples obtained both before and after seroconversion, and direct cycle sequencing of the PCR products was performed. A mutation resulting in a premature stop codon was found in the pre-S1 region of one patient just prior to clearance of HBsAg. Two years later, the stop codon was converted to a leucine codon and three mutations developed in the "a" loop. In the other patient, 16 amino acids had been deleted between amino acids 8 and 23 in the pre-S2 region before clearance of HBsAg. After the appearance of circulating anti-HBs, the pre-S2 gene reverted to the wild type but three additional mutations appeared inside the "a" loop. These results suggest that HBV mutates when HBsAg is cleared, which may contribute to viral persistence due to an evasion of the host immune surveillance.
为了确定慢性乙型肝炎患者在获得抗乙型肝炎表面抗原抗体（抗-HBs）后病毒持续存在的机制，我们对一组受感染患者的包膜区核苷酸序列进行了连续分析。研究了4例经我院工作人员至少观察5年的慢性乙型肝炎组织学诊断患者。除1例患者外，所有患者在乙型肝炎表面抗原（HBsAg）清除和抗-HBs出现后血清丙氨酸氨基转移酶（ALT）浓度均恢复正常。即使在存在循环抗-HBs的情况下，通过聚合酶链反应（PCR）扩增检测仍可在2例患者的血清标本中检测到乙型肝炎病毒（HBV）DNA。在血清学转换前后获得的血清样本中通过PCR扩增包膜基因，并对PCR产物进行直接循环测序。在1例患者的HBsAg清除前，其前S1区发现一个导致提前终止密码子的突变。两年后，终止密码子转变为亮氨酸密码子，并且在“a”环中出现了3个突变。在另1例患者中，在HBsAg清除前，前S2区第8至23位氨基酸之间缺失了16个氨基酸。循环抗-HBs出现后，前S2基因恢复为野生型，但在“a”环内又出现了3个额外的突变。这些结果表明，HBsAg清除时HBV发生突变，这可能由于逃避宿主免疫监视而导致病毒持续存在。
