Host Determinants of Human Metapneumovirus and Pathogenesis

项目摘要 我们研究计划的长期目标是了解人类偏肺病毒的机制 （HMPV）的免疫和发病机制，并促进疫苗开发。HMPV是导致严重 下呼吸道感染（LRI）在世界各地的儿童和成人。目前还没有针对HMPV的许可疫苗。 HMPV和其他呼吸道病毒（如呼吸道合胞病毒（RSV））的反复感染 在生活中。因此，HMPV和RSV在老年人和患有HMPV的人中引起严重疾病。 基础疾病，如哮喘、免疫功能低下和慢性心肺疾病。有限 呼吸道病毒诱导CD8 + T细胞（TCD8）记忆可能是再感染的一个促成因素， 这对开发有效的疫苗构成了障碍。RSV、流感病毒和副流感病毒 已显示诱导具有受损的细胞溶解功能和IFN γ分泌的TCD8，但这种作用的机制 抑制作用未知。类似的抗原无反应性称为TCD8耗竭与慢性 病毒感染和癌症。耗尽的TCD8的关键介质是程序性细胞死亡-1（PD-1），其是一种负调控因子。 调节T细胞活化，参与维持外周耐受和预防自身免疫。PD-1 而包括LAG-3在内的其它抑制性受体是慢性感染和癌症的治疗靶点。一 在这些患者中公认的不良反应是呼吸道炎症，可能是由于过度活化的TCD8。 我们发现HMPV、流感病毒和其他呼吸道病毒诱导TCD8损伤， 通过PD-1途径。然而，我们的初步数据表明，其他抑制性受体，包括LAG-3， 参与维持肺TCD8损伤在后期的疲惫。我们假设 呼吸道病毒激活了一个协调的抑制通路网络，限制了急性TCD8 反应和免疫病理学，但也限制了有效的记忆TCD8诱导。这些抑制性 途径可能是限制肺部炎症的天然免疫调节反应，但也限制了 有效的主机响应和内存。阐明这些机制将增加对贫困的理解。 对呼吸道病毒的免疫记忆，并帮助指导疫苗的开发。具体目标1： 测试PD-L1对肺中不同细胞类型具有不同功能的假设。在目标2中，我们定义 其他抑制性受体通路对晚期TCD8损伤的作用。在具体目标3中，我们将测试 使用非复制病毒样颗粒可以绕过肺TCD8损伤编程假设 (VLP)具有局部抑制性受体阻断的疫苗。这项工作将阐明TCD8损伤的机制， 并确定TCD8免疫调节通路在疫苗接种记忆反应中的作用， 病毒性呼吸道感染这些发现将指导HMPV疫苗的开发，并确定HMPV的生物标志物。 有效的TCD8疫苗反应。这些实验的结果将适用于其他呼吸系统 病原体以及与呼吸系统并发症相关的抑制性受体阻断治疗。

PROJECT SUMMARY The long-term goal of our research program is to understand mechanisms of human metapneumovirus (HMPV) immunity and pathogenesis and facilitate vaccine development. HMPV is a leading cause of severe lower respiratory infection (LRI) in children and adults worldwide. There is no licensed vaccine against HMPV. Recurrent infections with HMPV and other respiratory viruses such as respiratory syncytial virus (RSV) occur throughout life. Consequently, HMPV and RSV cause severe illness in older adults and persons with underlying conditions such as asthma, immune compromise, and chronic cardiopulmonary disease. Limited induction of CD8+ T cell (TCD8) memory by respiratory viruses may be a contributing factor to reinfection and presents an obstacle to the development of effective vaccines. RSV, influenza, and parainfluenza viruses have been shown to induce TCD8 with impaired cytolytic function and IFNγ secretion, but the mechanism of this inhibition was unknown. Similar antigen unresponsiveness termed TCD8 exhaustion is associated with chronic viral infections and cancer. A key mediator of exhausted TCD8 is programmed cell death-1 (PD-1), a negative regulator of T cell activation implicated in maintaining peripheral tolerance and preventing autoimmunity. PD-1 and other inhibitory receptors including LAG-3 are therapeutic targets in chronic infections and cancer. A recognized adverse effect in these patients is respiratory inflammation, likely due to over-activated TCD8. We discovered that HMPV, influenza, and other respiratory viruses induce TCD8 impairment mediated initially by the PD-1 pathway. However, our preliminary data suggest that other inhibitory receptors, including LAG-3, are involved in maintaining lung TCD8 impairment in later stages of exhaustion. We hypothesize that respiratory viruses activate an orchestrated network of inhibitory pathways, which limit the acute TCD8 response and immunopathology, but also limit the induction of effective memory TCD8. These inhibitory pathways are likely natural immunoregulatory responses to limit lung inflammation, but which also limit effective host response and memory. Elucidating these mechanisms would increase understanding of poor immune memory against respiratory viruses and help guide vaccine development. In Specific Aim 1, we will test the hypothesis that PD-L1 has distinct functions on different cell types in the lung. In Aim 2, we will define the contribution of other inhibitory receptor pathways to late TCD8 impairment. In Specific Aim 3, we will test the hypothesis that lung TCD8 impairment programming can be bypassed using non-replicating virus-like particle (VLP) vaccines with local inhibitory receptor blockade. This work will elucidate mechanisms of TCD8 impairment and define the contribution of TCD8 immunoregulatory pathways in the memory response to vaccination and viral respiratory infections. The findings will guide HMPV vaccine development and identify biomarkers of effective TCD8 responses to vaccines. The results of these experiments will be applicable to other respiratory pathogens as well as relevant to respiratory complications of inhibitory receptor blockade therapy.