Inflammatory Dendritic Cells in Influenza Virus Infection

描述(申请人提供)：流感病毒引起严重的呼吸道感染，导致全球范围内的发病率和死亡率。病毒复制仅限于呼吸道上皮层，恢复依赖于产生有效的细胞免疫反应。树突状细胞(DC)是一种免疫系统哨兵，位于上皮下的网络中，使它们非常适合与入侵的病原体相互作用。当DC吞噬微生物并使用遗传编码的病原体识别受体识别微生物结构时，DC就会激活。激活后，DC进入外周淋巴组织，在那里它们刺激特定的T细胞。在流感病毒感染中，激活的T细胞返回肺部并杀死受感染的目标细胞，从而导致病毒清除和宿主恢复。在我们的小鼠研究中，携带病毒抗原的DC在感染流感病毒48小时后开始到达引流淋巴结(LN)，并在感染小鼠的肺部观察到编码炎症介质的基因上调。鉴于高病毒滴度(24小时25微升肺裂解物中有105个)和常驻DC非常接近上皮细胞，获得性免疫的这种延迟似乎过了头。流感病毒的NS1蛋白阻止受感染细胞释放天然效应物，如I型干扰素。我们已经证明，它还可以在体外阻断DC的激活，抑制细胞因子、趋化因子和其他炎症介质的释放。在受感染的动物中，NS1的抑制可能允许病毒在不触发免疫干预的情况下复制。然而，从感染后48小时开始，单个核细胞迅速涌入肺部，大大增加了这个器官中的细胞数量。这些细胞中有相当大一部分是单核细胞，可同时产生DC和常驻巨噬细胞。我们假设，当病毒滴度达到非常高的水平时，免疫诱导剂和炎症介质从肺部的细胞群中释放出来，并触发细胞内流。此外，我们推测，新到达的单核细胞主要负责携带病毒抗原到引流的淋巴结和激活病毒特异性T细胞。哪些介质负责单个核细胞向感染肺的募集，以及浸润性细胞在产生获得性免疫中扮演什么角色，是我们在这一应用中试图回答的主要问题。

Description (provided by applicant): Influenza virus causes severe respiratory infections leading to morbidity and mortality worldwide. Virus replication is limited to the epithelial layers of the respiratory tract and recovery is dependent upon the generation of an effective cellular immune response. Dendritic cells (DC) are immune system sentinels found in a network below the epithelium making them ideally suited to interact with invading pathogens. DC activation occurs when they engulf microbes and identify microbial structures using genetically coded pathogen recognition receptors. Following activation the DCs traffic to peripheral lymphoid tissue where they stimulate specific T cells. In influenza virus infection, the activated T cells return to the lungs and kill infected target cells leading to viral clearance and host recovery. In our mouse studies DCs bearing viral antigens began to arrive in draining lymph nodes (LN) 48 hours after infection (PI) with influenza virus and a concomitant upregulation of genes that code for inflammatory mediators was observed in the lungs of infected mice. This delay in adaptive immunity seems excessive in light of the high viral titers (105 in 25 ul lung lysates at 24 hours) and the close proximity of resident DCs to epithelial cells. The NS1 protein of influenza virus prevents the release of innate effectors such as type I interferon from infected cells. We have shown that it also blocks activation of DCs in vitro inhibiting the release of cytokines, chemokines and other inflammatory mediators. In infected animals, the inhibition by NS1 may allow virus to replicate without triggering immune intervention. However, beginning 48 hours after infection there is a rapid influx of mononuclear cells to the lungs that greatly increases the cell numbers in this organ. A significant proportion of these cells are monocytes known to give rise to both DCs and resident macrophages. We hypothesize that immune attractants and inflammatory mediators are released from a cell population in the lungs when virus titers reach very high levels and trigger the cellular influx. Furthermore, we speculate that the newly arriving monocytes are primarily responsible for carrying viral antigens to the draining lymph nodes and activating virus specific T cells. Which mediators are responsible for the recruitment of mononuclear cells to the infected lungs and what role the infiltrating cells play in the generation of adaptive immunity are the primary questions we will attempt to answer in this application.