Abstract：
The nonstructural protein 1 (NS1) of influenza A viruses is an important virulence factor that controls host cell immune responses. In human cells, NS1 proteins inhibit the induction of type I interferon by several mechanisms, including potentially, by preventing the activation of the retinoic acid-inducible gene I (RIG-I) receptor by the ubiquitin ligase tripartite motif-containing protein 25 (TRIM25). It is unclear whether the inhibition of human TRIM25 is a universal function of all influenza A NS1 proteins or is strain dependent. It is also unclear if NS1 proteins similarly target the TRIM25 of mallard ducks, a natural reservoir host of avian influenza viruses with a long coevolutionary history and unique disease dynamics. To answer these questions, we compared the ability of five different NS1 proteins to interact with human and duck TRIM25 using coimmunoprecipitation and microscopy and assessed the consequence of this on RIG-I ubiquitination and signaling in both species. We show that NS1 proteins from low-pathogenic and highly pathogenic avian influenza viruses potently inhibit RIG-I ubiquitination and reduce interferon promoter activity and interferon-beta protein secretion in transfected human cells, while the NS1 of the mouse-adapted PR8 strain does not. However, all the NS1 proteins, when cloned into recombinant viruses, suppress interferon in infected alveolar cells. In contrast, avian NS1 proteins do not suppress duck RIG-I ubiquitination and interferon promoter activity, despite interacting with duck TRIM25. IMPORTANCE Influenza A viruses are a major cause of human and animal disease. Periodically, avian influenza viruses from wild waterfowl, such as ducks, pass through intermediate agricultural hosts and emerge into the human population as zoonotic diseases with high mortality rates and epidemic potential. Because of their coevolution with influenza A viruses, ducks are uniquely resistant to influenza disease compared to other birds, animals, and humans. Here, we investigate a mechanism of influenza A virus interference in an important antiviral signaling pathway that is orthologous in humans and ducks. We show that NS1 proteins from four avian influenza strains can block the coactivation and signaling of the human RIG-I antiviral receptor, while none block the coactivation and signaling of duck RIG-I. Understanding host-pathogen dynamics in the natural reservoir will contribute to our understanding of viral disease mechanisms, viral evolution, and the pressures that drive it, which benefits global surveillance and outbreak prevention.
摘要：
甲型流感病毒的非结构蛋白1（NS1）是控制宿主细胞免疫反应的重要毒力因子。在人类细胞中，NS1蛋白通过几种机制抑制I型干扰素的诱导，包括潜在的，通过防止泛素连接酶三联基序蛋白25（TRIM25）激活视黄酸诱导基因I（RIG-I）受体。目前尚不清楚抑制人TRIM25是所有甲型流感NS1蛋白的普遍功能还是毒株依赖性的。目前还不清楚NS1蛋白是否同样靶向野鸭的TRIM25，禽流感病毒的天然宿主，具有悠久的共同进化历史和独特的疾病动态。为了回答这些问题,我们使用共免疫沉淀和显微镜比较了五种不同的NS1蛋白与人和鸭TRIM25相互作用的能力，并评估了这对两种物种的RIG-I泛素化和信号传导的影响。我们表明，来自低致病性和高致病性禽流感病毒的NS1蛋白有效抑制RIG-I泛素化，并降低转染人细胞中干扰素启动子活性和干扰素β蛋白分泌，而小鼠适应的PR8品系的NS1则没有。然而,所有的NS1蛋白，当克隆到重组病毒中时，抑制感染的肺泡细胞中的干扰素。相比之下,禽类NS1蛋白不抑制鸭RIG-I泛素化和干扰素启动子活性，尽管与鸭子TRIM25互动。重要性甲型流感病毒是人类和动物疾病的主要原因。定期,来自野生水禽的禽流感病毒，比如鸭子,通过中间农业宿主，并作为高死亡率和流行潜力的人畜共患疾病出现在人群中。由于它们与甲型流感病毒的共同进化，与其他鸟类相比，鸭子对流感疾病具有独特的抵抗力，动物,和人类。这里,我们研究了甲型流感病毒干扰人类和鸭子直系同源的重要抗病毒信号通路的机制。我们表明，来自四种禽流感毒株的NS1蛋白可以阻断人RIG-I抗病毒受体的共激活和信号传导，而没有人阻断鸭RIG-I的共激活和信号传导。了解自然水库中的宿主-病原体动态将有助于我们对病毒性疾病机制的理解。病毒进化,以及驱动它的压力，这有利于全球监测和疫情预防。
