隐匿性乙型肝炎病毒感染患者S基因突变特点分析

Characteristics of S gene mutation in patients with occult HBV infection

目的分析1例血清HBV DNA长期阳性但HBsAg阴性的隐匿性乙型肝类病毒感染(OBI)患者HBV S基因突变特点,揭示S基因突变与OBI发生及肝脏疾病进展的关系。方法收集该患者不同时间点的4份血清样本,扩增HBV S基因并进行克隆测序,挑选代表性突变株病毒基因构建重组载体并进行表型分析。结果从该患者4份血清样本中检出多种S基因突变形式,包括前S1区大片段缺失、s126–127"RPCMNCTI"插入突变、sQ129N、s131–133 TSM→NST和经典的sG145R突变等,其中s131–133 TSM→NST在前后4份动态样本的检测病毒克隆中所占比例分别为0%、26%、59%和74%;前S1区大片段缺失在4份样本检测病毒克隆中始终存在,所占比例分别为26%、17%、15%和21%。表型分析发现,sQ129N和s131–133 TSM→NST可以降低抗体对HBsAg的亲和力,增加病毒分泌;与野生株相比,前S1区大片段(nt 3046–3177)缺失病毒株复制力下降了43.7%,表面抗原启动子Ⅱ(SPⅡ)活性下降了97.2%;sG145R可降低病毒的分泌能力。结论此例HBV感染患者的长期OBI临床表现是由于其感染有多种S基因突变病毒株引起,其中一些S基因突变可以影响病毒的表型特点,可能与肝脏疾病进展密切相关。

Objective To analyze characteristics of HBV S gene mutation in one patient with occult hepatitis B virus infection, who was positive for serum HBV DNA for long term, but negative for HBsAg in order to reveal the correlation between S gene mutation and development of OBI as well as the progression of the liver disease. Methods Four serum samples were collected at different time-points for the use of amplifying HBV S gene and performing cloning-sequencing. The representative S mutants were selected to construct recombinant vectors for phenotype analysis. Results Several S-gene mutational patterns were detected in the samples, including pre-S1 large fragment deletion, s126-127 ＂RPCMNCTI＂ insertion, sQ129N, s131-133 TSM--~NST, and classical sG14SR mutations. In sequential 4 samples, s131-133 TSM→NST mutation was detected in 0%, 26%, 59% and 74% of viral clones, respectively. The pre-S1 large fragment deletion was constantly found in the 4 serum samples, accounting for 26%, 17%, 15% and 21% of detected viral clones, respectively. Phenotypic analysis showed that sQ.129N and s131-133 TSM → NST mutations reduced the affinity of the antibody to HBsAg and increased the secretion of virus particles. Compared with the wild-type strainj the replication capacity and surface antigen promoter Ⅱ （SP Ⅱ ） activity of large fragment-deleted （nt 3046-3177 deletion） strain were decreased by 43.7% and 97.2%, respectively. In addition, sG14SR-induced impairment to secretion capacity of viral particles was verified. Conclusions Clinical presentations of long-term OBI of this HBV-infected patient could he caused by multiple S-gene mutants.Some S-gene mutations influence viral phenotypic characteristics, which might closely be related to the progression of liver disease.