Activation of the NLRP3 inflammasome by IAV virulence protein PB1-F2 contributes to severe pathophysiology and disease.
Activation of the NLRP3 inflammasome by IAV virulence protein PB1-F2 contributes to severe pathophysiology and disease.
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DOI：
10.1371/journal.ppat.1003392
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发表时间：
2013
期刊：
影响因子：
6.7
通讯作者：
Mansell A
中科院分区：
文献类型：
--
作者：
McAuley JL;Tate MD;MacKenzie-Kludas CJ;Pinar A;Zeng W;Stutz A;Latz E;Brown LE;Mansell A
宿主识别感染的能力对于病毒清除至关重要，并且通常始于炎症的诱导。致病性甲型流感病毒（IAV）的PB 1-F2有助于感染的病理生理学，尽管其机制尚不清楚。NLRP 3-炎性体与IAV的发病机制有关，但IAV毒力蛋白是否可以成为该复合物的激活剂尚不清楚。我们研究了PB 1-F2介导的NLRP 3-炎性体的激活是否是导致对IAV感染的明显炎症反应的机制。我们发现PB 1-F2通过激活NLRP 3-炎性体诱导致热原细胞因子IL-1β的分泌，从而导致致病性IAV引发的炎症。与野生型病毒感染相比，用反向工程PB 1-F2缺陷型IAV感染的小鼠导致IL-1β分泌和气道细胞募集减少。此外，与暴露于源自季节性IAV的肽的小鼠相比，暴露于源自致病性IAV的PB 1-F2肽的小鼠具有增强的IL-1β分泌。特别是涉及NLRP 3-炎性体复合物，我们表明源自致病性IAV诱导的IL-1β分泌的PB 1-F2在人PBMC中是半胱天冬酶-1依赖性的，在小鼠中是NLRP 3依赖性的。重要的是，我们证明PB 1-F2被纳入吞噬溶酶体室，酸化后，诱导ASC斑点形成。我们还表明，高分子量聚集的PB 1-F2，而不是可溶性PB 1-F2，诱导IL-1β分泌。此外，暴露于PB 1-F2肽或感染表达PB 1-F2的IAV的NLRP 3缺陷小鼠无法有效诱导在野生型小鼠中观察到的强烈炎症反应。除了病毒孔形成毒素、离子通道蛋白和RNA之外，我们证明NLRP 3-炎性体激活的诱导物可能包括无序的病毒蛋白，如PB 1-F2所示，其充当宿主病原体“危险”信号。阐明免疫刺激PB 1-F2介导的NLRP 3-炎性体激活是我们理解归因于对IAV感染的旺盛炎症反应的疾病病因学的重要一步。流感病毒是一种高度传染性的呼吸道病原体，可引起大流行，导致全世界数百万人死亡。以前，我们证明致病性流感产生的PB 1-F2蛋白诱导对感染的压倒性炎症反应，从而增强疾病。PB 1-F2引起这种明显炎症的方式尚不清楚。近年来，流感病毒被证实参与激活炎性小体，其在感染的炎症反应中起关键作用。然而，病毒产生的毒力因子如PB 1-F2是否能在炎性小体的激活中发挥作用尚不清楚。在这里，我们研究了PB 1-F2是否可以在炎性小体的激活中发挥作用。使用检测炎性细胞因子IL-1β作为炎性小体复合物活化的标志物，我们明确显示来自致病菌株的PB 1-F2在人类和小鼠中快速诱导炎性小体的活化。使用来自缺乏炎性体复合物组分的小鼠的巨噬细胞，显示炎症的诱导是半胱天冬酶-1和NLRP 3依赖性的。在NLRP 3缺陷型小鼠中消除了由PB 1-F2诱导的炎症。据我们所知，这是第一个描述的机制PB 1-F2介导的炎性复合物激活。我们的工作提供了进一步了解PB 1-F2在流感感染期间增强炎症的贡献。
The ability for a host to recognize infection is critical for virus clearance and often begins with induction of inflammation. The PB1-F2 of pathogenic influenza A viruses (IAV) contributes to the pathophysiology of infection, although the mechanism for this is unclear. The NLRP3-inflammasome has been implicated in IAV pathogenesis, but whether IAV virulence proteins can be activators of the complex is unknown. We investigated whether PB1-F2-mediated activation of the NLRP3-inflammasome is a mechanism contributing to overt inflammatory responses to IAV infection. We show PB1-F2 induces secretion of pyrogenic cytokine IL-1β by activating the NLRP3-inflammasome, contributing to inflammation triggered by pathogenic IAV. Compared to infection with wild-type virus, mice infected with reverse engineered PB1-F2-deficient IAV resulted in decreased IL-1β secretion and cellular recruitment to the airways. Moreover, mice exposed to PB1-F2 peptide derived from pathogenic IAV had enhanced IL-1β secretion compared to mice exposed to peptide derived from seasonal IAV. Implicating the NLRP3-inflammasome complex specifically, we show PB1-F2 derived from pathogenic IAV induced IL-1β secretion was Caspase-1-dependent in human PBMCs and NLRP3-dependent in mice. Importantly, we demonstrate PB1-F2 is incorporated into the phagolysosomal compartment, and upon acidification, induces ASC speck formation. We also show that high molecular weight aggregated PB1-F2, rather than soluble PB1-F2, induces IL-1β secretion. Furthermore, NLRP3-deficient mice exposed to PB1-F2 peptide or infected with PB1-F2 expressing IAV were unable to efficiently induce the robust inflammatory response as observed in wild-type mice. In addition to viral pore forming toxins, ion channel proteins and RNA, we demonstrate inducers of NLRP3-inflammasome activation may include disordered viral proteins, as exemplified by PB1-F2, acting as host pathogen ‘danger’ signals. Elucidating immunostimulatory PB1-F2 mediation of NLRP3-inflammasome activation is a major step forward in our understanding of the aetiology of disease attributable to exuberant inflammatory responses to IAV infection. Influenza virus is a highly contagious respiratory pathogen that can cause pandemics, resulting in the deaths of millions worldwide. Previously we demonstrated that PB1-F2 protein produced by pathogenic influenza induces overwhelming inflammatory responses to infection, which enhances disease. The way in which PB1-F2 causes this overt inflammation is unclear. Recently, influenza virus was shown to be involved in activating the inflammasome, which plays a pivotal role during inflammatory responses to infection. However, whether virulence factors such as PB1-F2 produced by the virus can play a role in activation of the inflammasome is unknown. Here, we investigated whether PB1-F2 could have a role in activation of the inflammasome. Using detection of the inflammatory cytokine IL-1β as a marker for inflammasome complex activation, we definitively show PB1-F2 from a pathogenic strain rapidly induces activation of the inflammasome in humans and mice. Using macrophages from mice lacking components of the inflammasome complex, induction of inflammation was shown to be Caspase-1 and NLRP3-dependent. Inflammation induced by PB1-F2 was abrogated in NLRP3-deficient mice. To our knowledge, this is the first description of the mechanism of PB1-F2-mediated inflammasome complex activation. Our work provides further understanding of the contribution of PB1-F2 to enhancing inflammation during influenza infections.
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