Immature Infant Alveloar Macrophage Clearance of Cell Debris During RSV Infection

描述（由申请人提供）：我们实验室的长期目标是更好地了解影响急性和慢性肺部疾病结局的宿主免疫力的年龄差异，以便我们能够改进婴儿和老年人群的治疗和疫苗策略。我们目前的研究重点是呼吸道合胞病毒（RSV），这是一种在非常年老和非常年轻的人中引起严重疾病的感染，没有可用的疫苗和有效的治疗方法。我们已经开发了RSV感染的幼鼠模型，以提高我们对RSV感染的婴儿与成人宿主免疫应答的理解。已知细胞碎片的积累和气道阻塞是严重RSV疾病的结果，并且构成>90%的气道细胞的肺泡巨噬细胞（AM）负责清除细胞碎片。然而，关于不成熟的婴儿AM如何导致严重疾病或其免疫调节以减轻RSV病理的潜力知之甚少。拟议工作的目标是确定婴儿AM在感染期间延长RSV复制和损害凋亡细胞清除的程度，以及吸入IFNγ的免疫调节是否减轻了这些影响。我们已经证明，吸入IFNγ治疗增加AM活化，加速RSV清除，并减少BALB/c小鼠中的凋亡细胞和粘液的数量。我们假设婴儿AM有助于细胞凋亡碎片的积累，并由于不成熟的肺环境而延长RSV复制，吸入IFNγ可以减轻这种情况。为了验证我们的假设，我们将完成两个具体目标。第一个目的是确定吸入IFNγ增强新生小鼠中RSV、凋亡细胞（AC）和粘液清除并保护其免受RSV介导的气道高反应性（AHR）的机制。预期该目标的结果表明，AM耗竭的小鼠将具有AC清除所需的M1和M2 c AM功能降低、RSV清除延迟和气道阻力增加，并且IFNγ作用于AM以消除这些效应。具体目标2将定义在有或没有IFN预激的情况下调节人脐带血和成人血单核细胞衍生的巨噬细胞对载有RSV的A549细胞的胞浆细胞增多的信号。我们预期在RSV感染期间，IL-10/M-CSF极化的M2 c巨噬细胞，无论来源如何，将比TGF β极化的巨噬细胞更多地增加AC清除，但是在不存在T细胞募集的情况下，吸入IFNγ将减轻RSV介导的受损的巨噬细胞增多症。

DESCRIPTION (provided by applicant): The long-term goal of our laboratory is to better understand the age-based differences in host immunity that affect acute and chronic pulmonary disease outcomes so we can improve therapeutic and vaccine strategies for infant and elderly populations. Our current research focus is respiratory syncytial virus (RSV), an infection that causes severe disease in the very old and very young, has no available vaccine and no effective therapy. We have developed an infant mouse model of RSV infection to improve our understanding of infant versus adult host immune responses to RSV infection. It is known is that the accumulation of cellular debris and airway occlusion is a consequence of severe RSV disease and alveolar macrophages (AMs), which make up >90% of airway cells, are responsible for clearing cell debris. However, little is known about how immature infant AMs contribute to severe disease or their potential for immunomodulation to mitigate RSV pathology. The goal of the proposed work is to determine the extent to which infant AMs prolong RSV replication and impair removal of apoptotic cells during infection and if immune modulation with inhaled IFNγ mitigates these effects. We have shown that treatment with inhaled IFNγ increases AM activation, expedites RSV clearance, and reduces the number apoptotic cells and mucus in infant BALB/c mice. We hypothesize that infant AMs contribute to the accumulation of apoptotic cellular debris and prolong RSV replication due to an immature lung environment which can be mitigated with inhaled IFNγ. To test our hypothesis we will complete two Specific Aims. The first Aim is to determine the mechanisms by which inhaled IFNγ enhances the clearance of RSV, apoptotic cells (ACs), and mucus and protects against RSV-mediated airway hyperresponsiveness (AHR) in neonatal mice. Results of this aim are expected to show that mice with depleted AMs will have reduced M1 and M2c AM function which is required for clearance of ACs, delayed RSV clearance, and increased airway resistance and that IFNγ acts on AMs to resolve these effects. Specific Aim 2 will define the signals that regulate the efferocytosis of RSV-laden A549 cells by human cord and adult blood monocyte-derived macrophages with or without IFN¿ priming. We expect IL-10/M-CSF polarized M2c macrophages, regardless of source, will increase AC clearance more than TGFß-polarized macrophages during RSV infection, but in the absence of T-cell recruitment, inhaled IFNγ will mitigate RSV-mediated impaired efferocytosis.