Age-dependent differences in the immune response to human metapneumovirus

摘要 人类偏肺病毒(HMPV)是幼儿下呼吸道感染的主要原因， 免疫功能受损的人和老年人，导致高发病率和死亡率。很少有研究发现 调查了为什么HMPV在老年人中更严重。这项建议旨在填补这一知识空白， HMPV的致病机制。我的初步数据发现，感染HMPV的老年小鼠表现出延迟病毒感染 清除，增加肺部炎症，增加CD8+HMPV-四聚体+细胞共表达 抑制标记PD-1、TIM-3和LAG-3。我推测老年人中严重的HMPV感染是 由CD8+T细胞反应受损引起。在目标1中，我将调查导致经济衰退的内在原因 用小鼠10倍基因组学研究HMPV感染老年宿主CD8+T细胞损伤 肺直接体外移植和同基因移植。10倍多组学将阐明与年龄相关的表观遗传学变化 在CD8+T细胞中，同基因移植会将年轻的CD8+T细胞转移到老化的宿主中，反之亦然 确定CD8+T细胞是否是导致对HMPV免疫反应受损的主要免疫细胞(即 体重减轻、临床严重程度、病毒清除延迟)。在目标2中，我将调查外在原因 CD8+T细胞损伤，即肺泡巨噬细胞(AM)损伤。我会用21色的多光谱流 细胞计数仪板计数老年宿主中的M1和M2巨噬细胞群。体外共培养和 AM和CD8+T细胞的转井分析将确定AM是否直接损害CD8+T细胞。选择性耗竭 AM在老年小鼠中的作用和年轻巨噬细胞的过继转移将决定AM如何在 老年宿主的免疫反应受损。10倍多重组学也将在这个目标上进行研究 AM中与年龄相关的表观遗传学变化可能有助于它们异常的M2积累，我有 在我的初步数据中也观察到了。 这项建议旨在了解老年宿主对HMPV反应的机制差异， 这将有助于解释为什么老年人的HMPV感染更严重。这些研究有可能 转化为临床环境，有助于更好地管理和治疗HMPV感染，如 作为免疫调节剂。识别老龄宿主中的分子靶点将指导安全和 为所有高危人群接种有效的HMPV疫苗。 此外，这项提议有巨大的培训机会，有助于实现我的职业目标 成为免疫学和传染病领域的临床科学家和独立首席研究员。

ABSTRACT Human metapneumovirus (HMPV) is a leading cause of lower respiratory infections in young children, immunocompromised persons, and the elderly, resulting in high morbidity and mortality. Few studies have investigated why HMPV is more severe in the elderly. This proposal aims to fill this knowledge gap about HMPV pathogenesis. My preliminary data discovered that aged mice infected with HMPV exhibit delayed viral clearance, increased lung inflammation, and increased CD8+ HMPV-tetramer+ cells co-expressing the inhibitory markers PD-1, TIM-3, and LAG-3. I hypothesize that severe HMPV infection in the elderly is caused by impairment of the CD8+ T cell response. In Aim 1, I will investigate the intrinsic causes of the CD8+ T cell impairment observed in the aged host infected with HMPV using 10X Multiomics studies on murine lung directly ex vivo and syngeneic transplants. 10X Multiomics will elucidate age-related epigenetic changes in CD8+ T cells while syngeneic transplants will transfer young CD8+ T cells into an aged host and vice versa to determine if CD8+ T cells are the primary immune cells causing the impaired immune response to HMPV (i.e. increased weight loss, clinical severity, delayed viral clearance). In Aim 2, I will investigate extrinsic causes of the CD8+ T cell impairment, namely by alveolar macrophages (AMs). I will use a 21-color multispectral flow cytometry panel to enumerate M1 and M2 macrophage populations in the aged host. In vitro co-culture and transwell assays of AMs and CD8+ T cells will determine if AMs directly impair CD8+ T cells. Selective depletion of AMs in aged mice and adoptive transfer of young macrophages will determine how AMs contribute to the impaired immune response in the aged host. 10X Multiomics will also be performed in this aim to investigate the age-related epigenetic changes in AMs that may contribute to their aberrant M2 accumulation, which I have also observed in my preliminary data. This proposal aims to understand the mechanistic differences in the aged host response to HMPV, which will help elucidate why HMPV infection in the elderly is more severe. These studies have the potential to translate into the clinical setting and contribute to better management and treatment for HMPV infection, such as immunomodulation. Identifying molecular targets in the aged host will guide development of a safe and effective vaccine against HMPV for all at-risk populations. In addition, this proposal has tremendous training opportunities, contributing towards my career goals of becoming a clinician scientist and independent principal investigator in immunology and infectious disease.