Visualizing the resolution of innate immune responses during influenza infection

最近主要流行病的证据表明，病毒的直接细胞致病性和炎症介导的组织损伤都是增强宿主致死性的同等重要的因素。因此，针对严重呼吸道感染提出了遏制过度免疫损伤的治疗策略。虽然流感感染细胞的清除主要是由细胞毒性CD8 T细胞介导的，但现在公认的抗病毒宿主反应对天然免疫和获得性免疫间隔的依赖表明，利用天然免疫可能形成有效疫苗和新治疗方法的开发基础。白细胞从血液中早期募集到组织感染部位是先天免疫反应的一个标志。然而，目前尚不清楚炎性组织中的凋亡免疫细胞是如何在消退阶段被移除的--这一过程对于我们理解和操纵炎症性疾病是至关重要的。尽管最近关于吞噬清除凋亡细胞的研究取得了进展，但体内动态细胞清除过程的可视化一直是极具挑战性的。在这里，我们建议开发一种新的活体多光子显微镜(IV-MPM)系统，以解决关于流感感染期间天然免疫细胞的功能和命运以及它们在抗病毒免疫反应中的作用的关键知识空白。我们将(1)开发IV-MPM系统，以在解决上(气管)和下(肺)呼吸道流感感染期间原位显示中性粒细胞吞噬作用，以及(2)开发一种新的组织驻留吞噬细胞命运图分析，以研究中性粒细胞吞噬作用的免疫学后果。在小鼠流感感染模型中使用这些新方法，我们将能够识别流感感染期间先天免疫系统和获得性免疫系统之间的新交互作用。鉴于病毒感染过程中动态免疫调节特性的重要性，开发新的研究工具来阐明先天免疫和感染部位效应器T细胞相互作用之间的关系，对于破译生产性和非生产性适应性免疫反应的基础，以及提高我们开发依赖于这种细胞介导反应的新的通用疫苗的能力至关重要。

Evidence from recent major epidemics suggests that both direct viral cytopathicity and inflammation-mediated tissue damage are equally important factors that potentiate the host lethality. Thus, the therapeutic strategy to bridle excessive immune damage has been proposed for severe respiratory infections. While clearance of influenza-infected cells is primarily mediated by cytotoxic CD8+ T cells, the now well-established dependency of anti-viral host responses on both innate and adaptive immune compartments suggests that harnessing the innate immunity might form a basis for the development of effective vaccines and novel therapeutic approaches. Early recruitment of leukocytes from the blood to sites of tissue infection is a hallmark of innate immune responses. However, it is currently not known how apoptotic immune cells are removed within inflamed tissues during the resolution phase – a process fundamental to our understanding and manipulation of inflammatory diseases. Despite recent advances in studies concerning phagocytic removal of apoptotic cells, the visualization of the dynamic cell clearance process in vivo has been extremely challenging. Here we propose to develop a novel intravital multi-photon microscopy (IV-MPM) system to address critical knowledge gaps regarding the function and fate of innate immune cells during the influenza infection, and their roles in anti-viral immune responses. We will (1) develop the IV-MPM system to visualize in situ neutrophil efferocytosis during resolution of influenza infection in the upper (trachea) and lower (lung) airway, and (2) develop a novel tissue-resident phagocyte fate-mapping assay to study the immunological consequence of the neutrophil efferocytosis. With these new approaches in a mouse influenza infection model, we will be able to identify novel interactions between innate and adaptive immune systems during the influenza infection. Given the importance of dynamic immune modulatory properties during viral infections, the development of novel research tools to elucidate the relationship between innate immunity and effector T cell interactions at the site of infection is critical for deciphering the basis of productive and nonproductive adaptive immune responses and for advancing our capacity to develop new universal vaccines that rely on such cell mediated responses.