Unité de Virologie et Immunologie Moléculaires, UR 892 INRA, Jouy-en-Josas, France.
PLoS Pathog. 2011 Aug;7(8):e1002202. doi: 10.1371/journal.ppat.1002202. Epub 2011 Aug 25.
Airway inflammation plays a major role in the pathogenesis of influenza viruses and can lead to a fatal outcome. One of the challenging objectives in the field of influenza research is the identification of the molecular bases associated to the immunopathological disorders developed during infection. While its precise function in the virus cycle is still unclear, the viral protein PB1-F2 is proposed to exert a deleterious activity within the infected host. Using an engineered recombinant virus unable to express PB1-F2 and its wild-type homolog, we analyzed and compared the pathogenicity and host response developed by the two viruses in a mouse model. We confirmed that the deletion of PB1-F2 renders the virus less virulent. The global transcriptomic analyses of the infected lungs revealed a potent impact of PB1-F2 on the response developed by the host. Thus, after two days post-infection, PB1-F2 invalidation severely decreased the number of genes activated by the host. PB1-F2 expression induced an increase in the number and level of expression of activated genes linked to cell death, inflammatory response and neutrophil chemotaxis. When generating interactive gene networks specific to PB1-F2, we identified IFN-γ as a central regulator of PB1-F2-regulated genes. The enhanced cell death of airway-recruited leukocytes was evidenced using an apoptosis assay, confirming the pro-apoptotic properties of PB1-F2. Using a NF-kB luciferase adenoviral vector, we were able to quantify in vivo the implication of NF-kB in the inflammation mediated by the influenza virus infection; we found that PB1-F2 expression intensifies the NF-kB activity. Finally, we quantified the neutrophil recruitment within the airways, and showed that this type of leukocyte is more abundant during the infection of the wild-type virus. Collectively, these data demonstrate that PB1-F2 strongly influences the early host response during IAV infection and provides new insights into the mechanisms by which PB1-F2 mediates virulence.
呼吸道炎症在流感病毒的发病机制中起着重要作用，并可能导致致命后果。流感研究领域的一个具有挑战性的目标是确定与感染过程中发生的免疫病理紊乱相关的分子基础。虽然 PB1-F2 蛋白在病毒周期中的确切功能仍不清楚，但该病毒蛋白被认为在感染宿主中发挥有害作用。我们使用一种无法表达 PB1-F2 及其野生型同源物的工程重组病毒，在小鼠模型中分析和比较了这两种病毒的致病性和宿主反应。我们证实，PB1-F2 的缺失使病毒的毒力降低。受感染肺部的全转录组分析显示，PB1-F2 对宿主反应有很大影响。因此，感染后两天，PB1-F2 无效严重减少了宿主激活的基因数量。PB1-F2 的表达增加了与细胞死亡、炎症反应和中性粒细胞趋化性相关的激活基因的数量和表达水平。当生成特定于 PB1-F2 的交互基因网络时，我们确定 IFN-γ 是 PB1-F2 调控基因的中心调节剂。使用凋亡测定法证实了气道募集白细胞的细胞死亡增加，证实了 PB1-F2 的促凋亡特性。使用 NF-kB 荧光素酶腺病毒载体，我们能够定量测量 NF-kB 在流感病毒感染介导的炎症中的体内作用；我们发现 PB1-F2 的表达增强了 NF-kB 的活性。最后，我们定量测量了气道内中性粒细胞的募集，并表明在野生型病毒感染期间这种白细胞更为丰富。总之，这些数据表明，PB1-F2 强烈影响 IAV 感染期间宿主的早期反应，并为 PB1-F2 介导毒力的机制提供了新的见解。
