A Chicken Model to Study Hepatitis E Virus Pathogenesis

戊型肝炎病毒（HEV）是戊型肝炎的病原体，是发展中国家的一个重要公共卫生问题。戊型肝炎在美国也很流行，据报道感染的孕妇死亡率高达20%。由于缺乏实用的动物模型和体外细胞培养系统，人们对HEV的复制和发病机制了解甚少，目前还没有针对HEV的疫苗。这一建议是基于我们最近在2000年从鸡身上发现的一种新型禽HEV和1997年从猪身上发现的一种新型猪HEV。禽HEV和猪HEV在抗原性和遗传上都与人HEV相关。我们已经证明猪戊型肝炎病毒感染非人类灵长类动物，美国人戊型肝炎病毒株感染猪，并且猪处理人员有人畜共患戊型肝炎病毒感染的风险。禽戊型肝炎在鸡中引起一种类似于人戊型肝炎的肝炎疾病。该建议的中心假设是戊型肝炎是一种人畜共患病，并且像猪一样，鸡也是戊型肝炎的动物宿主，并且鸡是戊型肝炎的有用动物模型系统。该项目的长期目标是通过使用鸡的HEV感染作为动物模型系统，以及通过禽-猪、禽-人和猪-人的HEV嵌合体来确定对这些过程具有重要功能的基因，来定义和理解HEV复制和发病机制。在本研究中，我们的目标是：1)在同源模型（禽HEV感染鸡）中系统地表征HEV的复制过程和发病机制；2)确定感染鸡的HEV复制的起始位点和肝外位点；3)构建禽HEV的感染性cDNA克隆，为今后利用HEV嵌合体研究HEV基因的结构和功能关系提供基础；4)评估禽HEV人畜共患感染的潜在风险。这将通过使用标准技术来完成，包括原位杂交，PCR，克隆和测序，基因表达，以及血清学和病理学方法。拟议的研究将显著促进我们对HEV复制机制、发病机制和自然历史的理解。所获得的信息将对开发HEV研究的小动物模型和制定预防和控制这一重要疾病的战略非常有用。

DESCRIPTION (provided by applicant): Hepatitis E virus (HEV), the causative agent of hepatitis E, is an important public health problem in developing countries. HEV is also endemic in the U.S. The mortality rate is reportedly up to 20% in infected pregnant women. Due to the lack of a practical animal model and an in vitro cell culture system, the replication and pathogenesis of HEV is poorly understood and a vaccine for HEV is still not available. This proposal is based on our recent discoveries of a novel avian HEV from chickens in 2000 and a novel swine HEV from pigs in 1997. Both avian HEV and swine HEV are antigenically and genetically related to human HEV. We have shown that swine HEV infects non-human primates and a U.S. human strain of HEV infects pigs, and that pig handlers are at risk of zoonotic HEV infection. Avian HEV causes a hepatitis disease in chickens that is similar to human hepatitis E. The central hypotheses of this proposal are that hepatitis E is a zoonosis and that, like pigs, chickens are also animal reservoirs for HEV, and that chickens are a useful animal model system for HEV. The long-term objectives of the project are to define and understand the mechanism of HEV replication and pathogenesis by using HEV infection in chickens as an animal model system and by using avian-swine, avian-human and swine-human HEV chimeras to identify genes that are functionally important for these processes. In this proposal, we aim to: 1) systematically characterize the course of HEV replication and pathogenesis in a homologous model (avian HEV infection in chickens), 2) to identify the initial and extrahepatic sites of HEV replication in infected chickens, 3) to construct an infectious cDNA clone of avian HEV for future study of the structural and functional relationship of HEV genes by using HEV chimeras, and 4) to evaluate the potential risk of zoonotic infection by avian HEV. This will be accomplished by using standard techniques including in situ hybridization, PCR, cloning and sequencing, gene expression, and serological and pathological methods. The proposed studies will significantly advance our understanding of the mechanisms of HEV replication, pathogenesis and natural history. The information gained will be very useful for developing small animal models for HEV research and for devising strategies to prevent and control this important disease.