Mechanism for spread of a quasi-enveloped hepatotropic virus

摘要 戊型肝炎病毒(HEV)是一种通过肠道传播的病毒，它以裸露的病毒粒子形式存在于粪便中 或在血液中循环的准包膜病毒粒子。HEV的准包膜促进非细胞溶解 从受感染的细胞中释放病毒。然而，病毒包膜蛋白的缺乏引发了机制的问题。 对于HEV的传播和抗体在自然感染中的作用。HEV每年感染约2000万人，并导致 严重的发病率和死亡率。免疫受损个体持续感染HEV可导致快速 肝纤维化的进展。目前还没有FDA批准的诊断和HEV特异性治疗。我们的 长期目标是解开这种不同寻常的包膜在病毒生命周期中的功能作用(S) 发病机制，目的是确定治疗干预的新靶点。这样做的总体目标是 项目是了解准包膜在HEV传播中的作用以及它是如何影响抗体介导的 中和。已知病毒ORF3蛋白在HEV包膜中起关键作用。我们的初步数据 提示ORF3通过棕榈酰化来调节病毒粒子的释放。另外，我们发现， 有证据表明，中和抗体可以阻止HEV在已经确定感染的细胞中传播。我们的 中心假设是需要ORF3介导的准包膜才能将HEV释放到血液中 进入胆汁(然后排入粪便)，准包膜的HEV颗粒通过一种 新的进入机制，容易被抗体进入后中和。我们将检验这一假设 在极化肝细胞培养和人肝嵌合小鼠中。目标1将定义棕榈酰化的作用 ORF3在细胞定位和病毒释放中的功能。目标2将定义蜂窝要求和 ORF3在HEV传播中的作用目标2还将确定抗体在阻止HEV传播中的作用和机制。 拟议研究的预期结果是对准经济增长的传播机制的新见解。 包膜病毒，并可能对其他非包膜病毒，如甲型肝炎、脊髓灰质炎病毒和 肠道病毒在其生命周期的某些阶段也会变成准包膜。这项工作将填补我们在 了解准包膜过程及其如何影响病毒传播、发病机制和 豁免权。

Summary Hepatitis E virus (HEV), an enterically transmitted virus, exists either as naked virions that are shed in the feces or quasi-enveloped virions that circulate in the blood. The quasi-envelopment of HEV facilitates noncytolytic release of virus from infected cells. However, the lack of viral envelope proteins raises question about mechanism for HEV spread and the role of antibodies in natural infection. HEV infects ~20 million people annually and causes significant morbidity and mortality. Persistent HEV infection in immunocompromised individuals can lead to rapid progression of liver fibrosis. Currently there are no FDA-approved diagnostics and HEV-specific therapies. Our long-term goal is to unravel the functional role(s) of this unusual envelopment in the virus life cycle and pathogenesis for the purpose of identifying novel targets for therapeutic intervention. The overall objective of this project is to understand the role of the quasi-envelopment in HEV spread and how it affects antibody-mediated neutralization. The viral ORF3 protein is known to play a key role in HEV envelopment. Our preliminary data suggest that ORF3 is subjected to regulation by palmitoylation to mediate virion release. In addition, we found evidence that neutralizing antibodies block HEV spread in cells that have already established infection. Our central hypothesis is that ORF3-mediated quasi-envelopment is required for HEV release into the bloodstream and into the bile (then shed into feces), and quasi-enveloped HEV particles mediate spread with the liver via a novel entry mechanism that is susceptible to post-entry neutralization by antibodies. We will test this hypothesis in polarized hepatocyte cell culture and in human liver chimeric mice. Aim 1 will define the role of palmitoylation of ORF3 in its cellular localization and function in virus release. Aim 2 will define the cellular requirements and role of ORF3 in HEV spread. Aim 2 will also define the role and mechanism of antibodies in blocking HEV spread. The expected outcomes of the proposed research are novel insights into the spread mechanism for a quasi- enveloped virus, and may have implications for other non-enveloped viruses such as hepatitis A, poliovirus, and enteroviruses that also become quasi-enveloped at certain stages of their life cycle. This work will fill gaps in our understanding of the quasi-envelopment processes and how it influences virus spread, pathogenesis and immunity.