Pathogenesis Of Viral Hepatitis

病毒性肝炎的发病机制

• 批准号: 6809352
• 负责人: Robert H. Purcell
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6809352
• 关键词: Callithricidae; Hepatovirus; Macaca mulatta; Pan; cellular immunity; cytotoxic T lymphocyte; enzyme linked immunosorbent assay; hepatitis B virus group; hepatitis C; hepatitis C virus; hepatitis virus; human tissue; humoral immunity; infectious hepatitis; interferon gamma; microarray technology; microorganism disease chemotherapy; molecular cloning; polymerase chain reaction; tissue /cell culture; transfection; vaccine development; virulence; virus cytopathogenic effect; virus genetics; virus infection mechanism; virus replication

We have studied the molecular basis for virulence in hepatitis A virus. Virulence (and attenuation) is controlled principally by two genes: VP1/2A and 2C. However, attenuating mutations are strongly selected against in vivo, resulting in the emergence of virulent variants. This has important implications for the development of a live attenuated hepatitis A vaccine. The genetic heterogeneity of hepatitis C virus is believed to play an important role in its pathogenicity. To examine this relationship, we have determined the genetic heterogeneity of HCV isolates that were recovered from patients who were infected following transfusion. The sequence of the hypervariable region and adjacent portions of envelope proteins 1 and 2 were determined for multiple clones obtained from patients who had fulminant hepatitis, from patients who convalesced following acute hepatitis and from patients who progressed to chronic hepatitis C. Distinctive patterns of dynamic change in the sequence of clones during the first several weeks of infection were observed. Patients with fulminant or resolving hepatitis had few changes in the sequences of clones, whereas there were many changes in the sequences of clones from patients who progressed to chronic hepatitis. Thus, the outcome of an HCV infection could be predicted in the first few weeks of the infection. Similar studies have been carried out in patients chronically infected with HCV and who were undergoing therapy with interferon. Patients could be separated into four groups, based upon their response to interferon therapy: a) long-term responders, b) those who relapsed following cessation of treatment, c) those who responded but had a break-through of viral replication while still on therapy and d) those who failed to respond (nonresponders). As with acutely infected HCV patients, distinctive patterns of dynamic change in the sequence and heterogeneity of HCV clones obtained early in therapy were predictive of outcome. Long-term responders demonstrated a marked decrease in heterogeneity of HCV, resulting in eradication of the virus. Relapsing patients also demonstrated a change in heterogeneity and a decrease in viral titer but a new dominant strain usually emerged following cessation of therapy. Nonresponders maintained the same dominant strain throughout therapy, suggesting that an interferon-resistant strain already existed before therapy. Patients who experienced a breakthrough during therapy had patterns that were similar to those of nonresponders, suggesting that this was a mixed group of patients. These findings may be useful in predicting the outcome of therapy with interferon early in the course of treatment. Hepatitis D virus (HDV) is a unique defective pathogen that causes severe acute and chronic hepatitis when it coninfects with hepatitis B virus (HBV). Patients chronically infected with HBV and HDV were treated with interferon and followed for up to 15 years. High doses (9 million units) resulted in long-term marked improvement in the patients, including reversal of cirrohsis and resolution of HBV and HDV infection in some patients even years after stopping therapy. More recently, we have extended these studies to an analysis of HCV sequences in infants and young children who were infected at birth. Although such perinatal transmissions are rare, they do offer an opportunity to study the interaction of the developing host immune response in an immunologically naive infant. Transmission of HCV from mother to infant often is characterized by virtually monoclonal viral infection initially, probably resulting from immunological selection by the mother's immune system. As the infant mounts its own immunological response, the genomic sequence becomes heterogeneous. Thus, the progression from monoclonal to polyclonal viral populations resembles that seen in chimpanzees experimentally infected with monoclonal HCV. Although considerable information has been gained from these longitudinal studies of patients, it is difficult to study the mechanisms of pathogenesis in such systems. Chimpanzees, which are the only animals other than man that are susceptible to infection with HCV provide an experimental model for studying the interactions of the host and the virus in the pathogenesis of hepatitis. Collaborative studies with Frank Chisari, Scripps Institute, have demonstrated that, both in hepatitis B virus infections and hepatitis C virus infections, the cellular immune response plays an important role in noncytolytic down-regulation of viral replication and cytolytic removal of residual infected cells. These two mechanisms are sequential and overlapping and the former appears to be mediated by interferon gamma and the latter by CD8+ CTLs and, perhaps, by interferon gamma through its proinflammatory activity. These studies have also revealed that type 1 interferon (interferon alpha/beta)-activated antiviral proteins are expressed in response to the viral infections, but that the viruses, especially HCV, are resistant to the antiviral activity of this innate immune response. Microarray studies of the host's immune responses to viral hepatitis and how the hepatitis viruses attempt to circumvent those responses are currently in progress. Among the human hepatitis viruses, only certain hepatitis E virus strains can replicate in nonprimate species of animals. We have studied the comparative pathogenesis of a swine-derived strain and a human-derived strain in swine as well as in nonhuman primates. These studies are important because of the potential for zoonotic spread of hepatitis E virus.

我们研究了肝炎A病毒毒力的分子基础。毒力（和衰减）主要由两个基因控制：VP1/2A和2C。然而，强烈选择衰减突变与体内的突变，从而导致有毒变体的出现。这对活体减毒肝炎A疫苗的发展具有重要意义。据信丙型肝炎病毒的遗传异质性在其致病性中起着重要作用。为了检查这种关系，我们确定了从输血后感染的患者中回收的HCV分离株的遗传异质性。确定了从患有暴发性肝炎的患者获得的多个克隆，从急性肝炎后恢复疗法的患者以及从第一次急性肝炎的患者中获得的多个患者，从患有暴发性肝炎的患者获得了多个克隆的序列和邻近的部分。暴发或解决肝炎的患者的克隆序列几乎没有变化，而从发展为慢性肝炎的患者的克隆序列序列发生了许多变化。因此，可以在感染的前几周预测HCV感染的结果。在长期感染HCV并接受干扰素治疗的患者中，已经进行了类似的研究。根据他们对干扰素治疗的反应，可以将患者分为四组：a）长期反应者，b）那些在停止治疗后复发的患者，c）那些反应但仍接受病毒复制的人，同时仍接受治疗，而d）那些未能反应的患者（无反应者）。与急性感染的HCV患者一样，在治疗早期获得的HCV克隆序列和异质性的动态变化的独特模式可以预测结果。长期响应者表明，HCV的异质性显着下降，导致该病毒的根除。复发患者还表现出异质性的变化和病毒滴度的减少，但在停止治疗后通常会出现新的显性菌株。在整个治疗过程中，无反应者保持相同的优势菌株，这表明在治疗前已经存在抗干扰素的菌株。在治疗期间经历突破的患者的模式与无反应者类似，这表明这是一群混合的患者。这些发现在治疗过程中早期预测干扰素治疗的结果可能很有用。丙型肝炎病毒（HDV）是一种独特的病原体，当与乙型肝炎病毒（HBV）结合时会导致严重的急性和慢性肝炎。长期感染了HBV和HDV的患者接受干扰素治疗，随后长达15年。高剂量（900万个单位）导致患者长期改善，包括在停止治疗后几年，某些患者的cirrohsis和HBV和HDV感染的分辨率。最近，我们将这些研究扩展到了出生时感染的婴儿和幼儿的HCV序列的分析。尽管这种围产期传播很少见，但它们确实提供了研究在免疫天真婴儿中发展宿主免疫反应的相互作用的机会。 HCV从母亲到婴儿的传播通常以实际上是单克隆病毒感染为特征，这可能是由于母亲的免疫系统的免疫学选择而引起的。随着婴儿的免疫反应，基因组序列变得异质。因此，从单克隆到多克隆病毒群体的进展类似于在黑猩猩中看到的单克隆HCV感染。尽管从患者的这些纵向研究中获得了大量信息，但很难研究这种系统中的发病机理。黑猩猩，这是易于感染HCV的人以外的唯一动物，为研究宿主的相互作用和病毒在肝炎的发病机理中提供了实验模型。斯克里普斯研究所（Scripps Institute）与弗兰克·奇萨里（Frank Chisari）的合作研究表明，在丙型肝炎病毒感染和丙型肝炎病毒感染中，细胞免疫反应在非溶解下调的病毒抑制和细胞溶解切除残留感染细胞中都起着重要作用。这两种机制是顺序的和重叠的，前者似乎是由干扰素伽玛和后者介导的，而后者是由CD8+ CTL介导的，也许是通过干扰素伽马通过其促炎活性介导的。这些研究还表明，1型干扰素（干扰素α/β）激活的抗病毒蛋白是对病毒感染的响应表达的，但是病毒，尤其是HCV，对这种先天免疫反应的抗病毒活性具有抗性。微阵列对宿主对病毒肝炎的免疫反应以及肝炎病毒试图规避这些反应的研究目前正在进行中。在人类肝炎病毒中，只有某些丙型肝炎病毒菌株才能在非良性动物中复制。我们研究了猪以及猪以及非人类灵长类动物中的猪衍生菌株和人类衍生的菌株的比较发病机理。这些研究很重要，因为可能会导致肝炎病毒的人畜共患病扩散。