A chicken model to study hepatitis E virus pathogenesis

描述（由申请人提供）：戊型肝炎是一种重要的公共卫生疾病，感染戊型肝炎的孕妇死亡率高达28%。最近，慢性HEV感染已成为世界范围内免疫功能低下个体（如器官移植受者和艾滋病毒、淋巴瘤和白血病患者）的一个新兴和重要的临床问题，具有相当高的发病率和死亡率。大约58-92%的HEV感染器官移植受者发展为慢性HEV感染，但导致进展为慢性的机制尚不清楚。本项目的长期目标是建立慢性戊型肝炎动物模型，研究其免疫发病机制和干预策略。在目的1中，我们假设免疫抑制条件下猪的HEV感染将模仿免疫功能低下个体的慢性HEV感染过程，这将使我们能够描述导致进展为慢性的预测性免疫因素。猪将被免疫抑制以模拟器官移植受者的免疫抑制情况，然后实验性地感染戊肝病毒。还将分析和比较HEV感染和肝炎的免疫学、病理学、生化、病毒学和临床参数，以确定进展为慢性的广泛预测因素。在目标2中，我们假设t细胞反应的损伤，特别是CD4+和CD8+ t细胞反应，是免疫功能低下个体进展为慢性的原因。我们将确定鸡体内特定CD4+或CD8+ T细胞亚群的消耗是否会导致感染禽戊型肝炎的鸡的慢性感染和严重肝炎。将CD4或CD8 T细胞缺失的鸡用实验方法感染禽戊型肝炎，并对其病理、生化、病毒学、免疫学和临床参数进行评估。将CD4+或CD8+ T细胞过继转移到免疫细胞缺失的鸡体内。在aim 3中，我们假设体液免疫反应是一把双刃剑，因为它在控制HEV感染方面很重要，但它也涉及免疫介导的肝脏损伤。将B细胞缺失鸡以及免疫球蛋白（Ig）重链纯合子敲除（-/-）仔猪和野生型窝仔（+/+）实验感染HEV，评估和比较肝炎的肝脏病变、免疫、生化和病毒学参数。Ig重链（-/-）敲除仔猪也将被动转移到HEV特异性抗血清中，然后进行HEV攻击。通过完成本项目，我们预计将建立一种独特的慢性戊型肝炎动物模型，确定导致慢性感染的预测免疫因子，绘制响应HEV感染的T细胞表位，描绘HEV免疫发病机制和慢性感染机制。研究结果将对制定有效的HEV预防和治疗策略具有重要意义。

DESCRIPTION (provided by applicant): Hepatitis E is an important public health disease with a high mortality rate of up to 28% in infected pregnant women. Recently, chronic HEV infection has become an emerging and significant clinical problem worldwide in immunocompromised individuals such as organ transplant recipients and patients with HIV, lymphoma and leukemia with considerable morbidity and mortality. Approximately 58-92% of the HEV-infected organ transplant recipients developed chronic HEV infection but the mechanism leading to the progression into chronicity remains unknown. The long-term goal of this project is to develop an animal model for chronic hepatitis E to study the mechanisms of HEV immunopathogenesis and intervention strategies. In aim 1, we hypothesize that HEV infection in pigs under immunosuppressive conditions will mimic the course of chronic HEV infection in immunocompromised individuals, which will enable us to delineate the predictive immunological factors leading to the progression into chronicity. Pigs will be immunosuppressed to mimic the immunosuppressive conditions in organ transplant recipients and then experimentally infected with HEV. The immunological, pathological, biochemical, virological and clinical parameters of HEV infection and hepatitis will also be analyzed and compared to identify the broad predictive factors for progression into chronicity. In aim 2, we hypothesize that impairment of T-cell responses, particularly CD4+ and CD8+ T-cell responses, is responsible for the progression into chronicity in immunocompromised individuals. We will determine if depletion of specific CD4+ or CD8+ T cell subsets in chickens will lead to chronic infection and severe hepatitis in chickens infected with avian HEV. Chickens depleted of either CD4 or CD8 T cells will be experimentally infected with avian HEV, and assessed for pathological, biochemical, virological, immunological and clinical parameters of hepatitis. Adoptive transfer CD4+ or CD8+ T cells into immune cell-depleted chickens will also be performed. In aim 3, we hypothesize that the humoral immune response is a double-edged sword in that it is important in control of HEV infection but it also involves in immune-mediated hepatic damages. B cell- depleted chickens as well as immunoglobulin (Ig) heavy chain homozygous knockout (-/-) piglets and wild-type littermate (+/+) will be experimentally infected with HEV, hepatic lesions, immunological, biochemical and virological parameters of hepatitis will be assessed and compared. The Ig heavy chain(-/-) knockout piglets will also be passively transferred with a HEV-specific antiserum followed by HEV challenge. By completing this project, we anticipate that a unique animal model for chronic hepatitis E will be established, and that the predictive immunological factors leading to chronic infection will be identified, the T cell epitopes responding to HEV infection mapped, and the mechanisms of HEV immunopathogenesis and chronic infection delineated. The results will be important for devising effective prevention and treatment strategies against HEV.