Morphogenesis of hepatitis B and hepatitis D virus particles: Strategies, mechanisms and host factors

人类乙型肝炎病毒（HBV）是一种包膜副逆转录病毒，可引起急性和慢性肝脏炎症。持续的乙肝病毒感染往往导致致命的肝功能衰竭，在全球范围内是最常见的传染病之一。同时感染丁型肝炎病毒（HDV）， HBV的卫星病毒，通常会增强肝脏的发病机制。目前批准的治疗方法是有限的，而且在大多数情况下无法治愈。由于它们有限的编码能力，这两种病毒都严重依赖宿主细胞，并发展出不同的策略来利用细胞功能。我们对HBV颗粒形态发生及其与宿主因子协调的研究表明，病毒颗粒（VPs）通过利用细胞自噬复合物、Rab gtpase、泛素接头、泛素连接酶和多泡内体网络（ESCRT）的特异性蛋白在细胞膜上发芽。除了VPs外，受感染的肝细胞还分泌大量非传染性亚病毒包膜颗粒（SVPs），也称为HBsAg。svp被认为耗尽了免疫反应，从而促进了病毒的持久性和发病机制。在这项更新提案中，我们将把我们的研究扩展到HDV，并将重点放在HBV包膜上，该包膜由两种病原体共享并形成svp的支架。作为一个整体目标，我们将探索指导SVP/病毒包膜生物发生的机制和宿主因素。特别是，基于我们的准备工作，我们将破译细胞外壳蛋白复合物II （COPII）囊泡出芽机制在HBV和HDV生物学中的作用。COPII复合体与Rab1 GTPase和TANGO1家族蛋白一起，在引导分泌系统内的货物运输中起着重要作用。基于蛋白质组学的研究揭示了HBV包膜与COPII的货物适配器亚基之间的相互作用。通过使用细胞培养系统结合细胞生物学方法，我们将研究HBV和HDV是否以及如何参与COPII出芽和运输机制以获益。通过探索病毒包膜- copii相互作用的分子机制，我们期待能找到有助于设计针对病毒-宿主串扰的治疗方法的证据。细胞穿透干扰肽将被开发和批准，因为它们具有抑制病毒颗粒释放的潜力，理想地影响HBV和HDV的SVP和VP的表达。此外，我们实验室新建立的HDV复制系统使我们能够研究这种特性不佳的病原体对辅助宿主因子的需求。

The human hepatitis B virus (HBV) is an enveloped pararetrovirus that causes acute and chronic liver inflammation. Persistent HBV infections often result in fatal liver failure and globally rank among the most common infectious diseases. Concomitant infections with the hepatitis D virus (HDV), a satellite of HBV, usually enhance liver pathogenesis. Currently approved therapies are limited and in most cases non-curative. Due to their limited coding capacities, both viruses are heavily dependent on the host cell and have developed diverse strategies to exploit cellular functions. Our investigations on HBV particle morphogenesis and its coordination by host factors reveal that viral particles (VPs) bud at intracellular membranes by the exploitation of cellular autophagy complexes, Rab GTPases, ubiquitin adaptors, ubiquitin ligases and specific proteins of the multivesicular endosome network (ESCRT). Besides VPs, infected hepatocytes also secrete in huge amounts non-infectious, subviral envelope particles (SVPs), also known as HBsAg. SVPs are thought to exhaust immune responses thereby contributing to viral persistence and pathogenesis. In this renewal proposal, we will extend our research to HDV and focus on the HBV envelope that is shared by both pathogens and forms the scaffold of SVPs. As an integral aim, we will explore mechanisms and host factors guiding SVP/viral envelope biogenesis. In particular, based on our preparatory works, we will decipher the role of the cellular coat protein complex II (COPII) vesicle budding machinery in HBV and HDV biology. The COPII complex, in conjunction with the Rab1 GTPase and TANGO1 family proteins, is instrumental in guiding cargo trafficking within the secretory system. Proteomics-based studies revealed an interplay between the HBV envelope and a cargo adaptor subunit of COPII. By using cell culture systems combined with cell biological methods, we will investigate if and how HBV and HDV may engage the COPII budding and trafficking machinery for benefit. By probing molecular insights into the virus envelope-COPII interaction, we are expecting evidence which will help to design therapeutic approaches targeting the virus-host crosstalk. Cell penetrating interfering peptides will be developed and approved for their potential to inhibit virus particle release, ideally affecting SVP and VP egress of both, HBV and HDV. Moreover, the newly setup of an HDV replication system in our lab enables to study auxiliary host factor requirements of this poorly characterized pathogen.