乙型肝炎病毒亚病毒颗粒对抗病毒治疗应答的影响及其机制的研究

A unique feature of hepatitis B virus (HBV) is that majority of the S protein, which is expressed at very high level, is secreted as the 22-nm subviral particles (SVP) lacking internal nucleocapsids. These circulating envelope proteins are detected serologically as HBsAg. The reason why HBV overproduces noninfectious SVPs, which exceed virions by a stunning 1,000 - 100,000 fold, has never been systemically tested. We hypothesize that this phenomenon may be related with pathogenesis of HBV infection. To investigate the clinical significance of SVPs in HBV infection and prediction of responding to antiviral therapy and the mechanisms, we will compare full-length HBV DNA sequence among patients with different outcomes or stages with the highest ratio of HBsAg/HBV DNA and those with the lowest ratio. And we will also test this among CHB patients with different antiviral response. This will establish whether HBV isolates from different antiviral response patients are more likely to harbor mutations in the envelope gene or core promoter that could influence S protein expression, HBsAg secretion, or HBsAg detection. For patients whose viremia is markedly suppressed by treatment, we will compare HBV cccDNA titer and sequence to establish whether those with a different HBsAg titer (suggestive of SVPs levels) have different ccc DNA levels in the liver and/or harbor mutations that could influence S protein expression, secretion, or detection. This is an important topic because reduction and eventual loss of HBsAg are markers for sustained virological response. Our researches will be helpful in exploring new strategies and targets regarding to antiviral therapy for chronic hepatitis B.

乙型肝炎病毒（HBV）复制周期中伴随成熟病毒同时产生大量亚病毒颗粒的现象是其特有的生命特征，但目前对其在病毒感染及致病机制的作用尚不清楚；而HBV高突变性造成的亚病毒颗粒表达或分泌减少可改变包括其在内的表面抗原（HBsAg）定量水平，并可能由此影响抗病毒治疗疗效监测和肝病进展。本课题拟利用分子生物学和生物信息学分析技术，研究HBV感染后不同临床阶段（转归）者(包括急性乙型肝炎、慢性HBV 携带、慢性乙型肝炎和肝硬化)、干扰素及核苷（酸）药物抗病毒治疗不同应答者的血清中亚病毒颗粒分泌量及其动态变化，以及对影响亚病毒颗粒表达和分泌的HBV 全长基因组和肝组织中HBV cccDNA基因突变进行分子特征分析（重点PreS1、PreS2、S和BCP区），体外细胞学实验分析相关突变对病毒蛋白功能的影响，探讨亚病毒颗粒在HBV感染和致病过程中的作用及其机制，为慢乙肝抗病毒治疗提供新思路、新靶点。

本项目在课题开展期间，围绕研究目标，从病毒学应答和HBeAg血清学应答两方面，分析抗病毒治疗过程中亚病毒颗粒基线水平和动态改变的特点与抗病毒治疗疗效应答的关系；并研究了HBV基因组变异对HBV亚病毒颗粒表达的影响及与慢乙肝干扰素治疗复发的关系；结合深度测序分析基线HBV准种特性对抗病毒治疗疗效的预测能力和聚乙二醇干扰素延长治疗e抗原阳性慢性乙型肝炎患者持续应答的预测指标，并都取得了系列研究成果，包括初步明确了血清HBV亚病毒颗粒水平与慢乙肝患者抗病毒治疗应答的关系，发现了亚病毒颗粒水平在基线和治疗4周时可极早期预测病毒学和血清学应答的预测价值；探讨了HBV基因组突变对HBV亚病毒颗粒表达的产生的影响及其这种突变对HBV cccDNA的影响机制，进而与慢乙肝干扰素治疗复发之间的关系；对HBV准种的深度测序研究为进一步深入分析亚病毒颗粒的编码区基因特征提供了新的研究手段。上述研究成果为明确亚病毒颗粒在HBV感染和致病过程中的作用及其机制，慢乙肝抗病毒治疗提供了新思路、新靶点。