Why Are Steroids Ineffective at Suppressing RSV Bronchiolitis

描述(申请人提供)：我们最近发现呼吸道合胞病毒(RSV)的非结构蛋白2的表达是人类呼吸道上皮RSV感染的特征。利用表达RSV NS2的重组副流感病毒(PIV)以及相关的人和仓鼠呼吸道柱状上皮模型，我们发现RSV NS2对PIV感染细胞的命运有显着的影响，导致病毒感染的上皮细胞显着地脱落到气道腔内，并出现高炎症表型。在仓鼠的远端气道，脱落细胞聚集在狭窄的管腔内，导致急性远端气道阻塞，并伴有炎症细胞的夸大募集。这些组织学结果与呼吸道合胞病毒毛细支气管炎婴儿的呼吸道组织学结果非常相似，提示PIV介导的呼吸道合胞病毒NS2在金黄地鼠细支气管处的表达是研究毛细支气管炎早期发病事件的一种新的动物模型。我们渴望使用这个模型来测试降低RSV毛细支气管炎严重程度的治疗方法，并设想减轻RSV NS2表达的后果的策略可能会为RSV毛细支气管炎的婴儿提供治疗益处。我们将首次使用这个模型来探索一个重要的临床问题：为什么类固醇不能抑制RSV诱导的炎症，而有效地抑制PIV诱导的炎症？利用相关的柱状气道上皮模型，我们在体外和体内测试RSV NS2的表达是否使PIV诱导的炎症对类固醇产生抵抗。我们还测试了一种 新型非类固醇抗炎调节剂，合成三萜类，以抑制RSV NS2表达的后果，因为这些药物已显示出作为抗炎药的巨大前景，但没有类固醇的副作用，目前正处于非呼吸系统适应症的人类临床试验中。我们的想法是RSV NS2诱导的炎症，虽然对类固醇具有抵抗力，但可能会被三萜类化合物抑制。最后，要充分利用 小鼠遗传模型和相关试剂我们设计了表达RSV NS2的小鼠呼吸道病毒，并测试了这些新型嵌合病毒感染小鼠呼吸道是否导致远端呼吸道阻塞和气道炎症加重，从而为未来的机制研究提供了一个有用的动物模型。呼吸道合胞病毒毛细支气管炎是导致婴儿住院的最大单一原因。在这里，我们建立了动物模型，在该动物模型中，RSV NS2在远端呼吸道的表达概括了婴儿RSV毛细支气管炎的特征。这些研究将为开发和测试缓解人类呼吸道合胞病毒毛细支气管炎的发病和严重程度的疗法提供一个新的平台。

DESCRIPTION (provided by applicant): We have recently discovered expression of the Non-Structural protein 2 of Respiratory Syncytial Virus (RSV) is responsible for hallmark characteristics of RSV infection of human airway epithelium. Using recombinant Parainfluenza Virus (PIV) expressing RSV NS2 and relevant models of human and hamster columnar airway epithelium we show RSV NS2 has a dramatic effect on the fate of PIV-infected cells resulting in a striking shedding of virus-infected epithelial cells into the airway lumen and a hyper-inflammatory phenotype. In hamster distal airways, shedding cells accumulate in the narrow lumens causing acute distal airway obstruction accompanied by exaggerated recruitment of inflammatory cells. These histologic findings are remarkably similar to those found in airways of human infants with RSV bronchiolitis and suggest PIV- mediated RSV NS2 expression in hamster bronchioles represent a novel animal model for investigating early initiating events of bronchiolitis. We are eager to use this model to test therapeutic approaches for reducing the severity of RSV bronchiolitis and envision strategies that lessen the consequences of RSV NS2 expression may provide therapeutic benefit to infants with RSV bronchiolitis. Our first use of this model will be to explore a significant clinical question; why steroids fail to suppress RSV-induced inflammation while effectively suppressing inflammation induced by PIV? Using relevant models of columnar airway epithelium we test whether RSV NS2 expression renders PIV-induced inflammation resistant to steroids in vitro and in vivo. We also test the efficacy of a novel class of non-steroidal anti- inflammatory modulators, the synthetic triterpenoids, to suppress consequences of RSV NS2 expression as these drugs have shown great promise as anti-inflammatory agents but without the adverse effects of steroids and are currently in human clinical trials for non-respiratory indications. Our notion is RSV NS2-induced inflammation, while resistant to steroids, may be suppressed by triterpenoids. Finally, to capitalize on the wealth of mouse genetic models and related reagents we engineer mouse respiratory viruses to express RSV NS2 and test whether infection of mouse airways with these novel chimeric viruses results in distal airway obstruction and exaggerated airway inflammation; thus, providing a useful animal model for future mechanistic studies. RSV bronchiolitis is the single largest cause of hospitalization of infants. Here, we develop animal models in which RSV NS2 expression in distal airways recapitulates hallmark characteristics of RSV bronchiolitis in infants. These studies will provide a novel platform for developing and testing therapeutics for relieving the onset and severity of RSV bronchiolitis in humans.