Hepatitis B virus e antigen expression

乙型肝炎病毒e抗原表达

基本信息

批准号：
6722792
负责人：
SHUPING TONG
金额：
$ 7.7万
依托单位：
RHODE ISLAND HOSPITAL
依托单位国家：
美国
项目类别：
财政年份：
2003
资助国家：
美国
起止时间：
2003-04-01 至 2006-03-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/6722792
关键词：
gene expression gene mutation genetic promoter element genetic strain hepatitis B antigens hepatitis B virus group host organism interaction tissue /cell culture virus genetics virus replication

项目摘要

DESCRIPTION (provided by applicant): Hepatitis B virus (HBV) infects nearly 1/10th of the world population and causes severe liver diseases including cancer. The e antigen (HBeAg) is a secreted soluble protein that promotes immune tolerance during perinatal infection and buffers immunity against HBcAg. The corresponding anti-HBe immune response plays a critical role in the clearance of HBV infection. Therefore, following seroconversion from HBeAg antigenemia to anti-HBe, HBV escape mutants with reduced or no HBeAg production often replace wild-type HBV genomes. The core promoter mutants have various nucleotide changes around positions 1750 -1770 of the HBV genome, and the most common mutations at 1762 and 1764 are known to reduce HBeAg expression at the transcriptional level. The precore mutants have nonsense or frameshift mutations in the HBeAg coding sequence and terminate HBeAg expression at the translational level. Considering the critical importance of HBeAg and anti-HBe in shaping the outcome of HBV infection, we wish to uncover novel regulatory mechanisms for HBeAg expression. In this regard, perinatally infected South African patients seroconvert from HBeAg to anti-HBe at a much accelerated pace than similarly infected Asian patients. Interestingly, the South African HBV variants often harbor two or three point mutations near the precore initiation codon. We plan to verify whether the mutations cause leaky scanning to reduce HbeAg translation. Second, HBeAg maturation requires double proteolytic cleavage events in the secretory pathway. The first cleavage occurs in endoplasmic reticulum to remove the N-terminal signal peptide of 19 residues. A Val to Phe missense mutation at residue 17 is frequently detected in HBV genomes isolated from seroconverted patients. Since an aromatic residue at the -3 position of cleavage site is forbidden, we will test whether this mutation impairs HBeAg cleavage and secretion. Third, we recently identified several naturally occurring core promoter mutants with wild-type level of HBeAg production. Based on the results of preliminary mapping experiments, we will determine whether the number and position of core promoter mutations influence the level of HBeAg expression, and whether missense mutations in the HBeAg coding sequence also regulate HBeAg level. This study promises to verify and identify novel mechanisms regulating HBeAg expression, which has a major impact on the outcome of HBV infection.

描述（由申请人提供）：乙型肝炎病毒（HBV）感染世界上近 1/10 的人口，并导致包括癌症在内的严重肝脏疾病。 e 抗原 (HBeAg) 是一种分泌的可溶性蛋白，可促进围产期感染期间的免疫耐受并缓冲针对 HBcAg 的免疫力。相应的抗HBe免疫反应在清除HBV感染中起着至关重要的作用。因此，在从 HBeAg 抗原血症到抗 HBe 血清转化后，HBeAg 产生减少或无 HBeAg 产生的 HBV 逃逸突变体通常会取代野生型 HBV 基因组。核心启动子突变体在 HBV 基因组的位置 1750 -1770 附近有各种核苷酸变化，已知最常见的 1762 和 1764 突变会在转录水平降低 HBeAg 表达。前核心突变体在 HBeAg 编码序列中具有无义或移码突变，并在翻译水平终止 HBeAg 表达。考虑到 HBeAg 和抗 HBe 在影响 HBV 感染结果中的至关重要性，我们希望揭示 HBeAg 表达的新调控机制。在这方面，围产期感染的南非患者从 HBeAg 血清转化为抗 HBe 的速度比类似感染的亚洲患者快得多。有趣的是，南非 HBV 变体通常在前核心起始密码子附近有两个或三个点突变。我们计划验证突变是否会导致漏扫描，从而减少 HbeAg 翻译。其次，HBeAg 成熟需要分泌途径中的双重蛋白水解裂解事件。第一次切割在内质网中发生，去除 19 个残基的 N 端信号肽。从血清转化患者中分离出的 HBV 基因组中经常检测到残基 17 处的 Val 至 Phe 错义突变。由于切割位点-3位的芳香族残基被禁止，我们将测试该突变是否会损害HBeAg的切割和分泌。第三，我们最近鉴定了几种天然存在的核心启动子突变体，具有野生型水平的 HBeAg 产生。根据初步定位实验的结果，我们将确定核心启动子突变的数量和位置是否影响HBeAg表达水平，以及HBeAg编码序列的错义突变是否也调节HBeAg水平。这项研究有望验证和确定调节 HBeAg 表达的新机制，这对 HBV 感染的结果具有重大影响。