A chicken model to study hepatitis E virus pathogenesis

描述(申请人提供)：戊型肝炎是一种重要的公共卫生疾病，在感染的孕妇中死亡率高达28%。近年来，在器官移植受者、HIV、淋巴瘤和白血病患者等免疫功能低下的人群中，慢性HEV感染已成为一个新出现的重大临床问题，具有相当高的发病率和死亡率。大约58-92%的HEV感染的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仍不清楚。本项目的长期目标是建立一种慢性戊型肝炎的动物模型，以研究HEV免疫发病机制和干预策略。在目标1中，我们假设在免疫抑制条件下猪的HEV感染将模拟免疫低下个体的慢性HEV感染过程，这将使我们能够描述导致进展为慢性化的预测性免疫学因素。猪将被免疫抑制，以模拟器官移植受者的免疫抑制状况，然后实验感染HEV。还将对HEV感染和肝炎的免疫学、病理学、生化、病毒学和临床参数进行分析和比较，以确定进展为慢性化的广泛预测因素。在目标2中，我们假设T细胞反应的损害，特别是CD4+和CD8+T细胞反应的损害，是免疫受损个体进展为慢性化的原因。我们将确定鸡体内特定的CD4+或CD8+T细胞亚群的耗尽是否会导致感染禽流感病毒的鸡的慢性感染和严重肝炎。去除了CD4或CD8 T细胞的鸡将被实验感染禽流感病毒，并对肝炎的病理、生化、病毒学、免疫学和临床参数进行评估。向免疫细胞耗尽的鸡过继转移CD4+或CD8+T细胞也将进行。在目标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损伤。实验感染去B细胞雏鸡、免疫球蛋白(Ig)重链纯合子(-/-)仔猪和野生型仔猪(+/+)，对肝炎的肝脏病变、免疫学、生化和病毒学指标进行评估和比较。免疫球蛋白重链(-/-)敲除的仔猪也将被被动地转移到HEV特异性抗血清中，然后再进行HEV攻击。通过这个项目的完成，我们预计将建立一个独特的慢性戊型肝炎动物模型，并将识别导致慢性感染的预测免疫学因素，绘制响应HEV感染的T细胞表位图，并阐明HEV免疫发病机制和慢性感染的机制。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.