禽流感是禽鸟中由A型流感病毒菌株引起的一种传染病。该病在全球范围发生。尽管认为所有的禽鸟均易感禽流感病毒，但是很多野生鸟类带有这些病毒却没有明显的受害迹象。

其它鸟类，包括家禽，当感染禽流感病毒时发生疾病。在家禽中，病毒产生两种显然不同的疾病类型 — 一种为常见和轻型，另一种少见但死亡率很高。1878年首次在意大利发现的高致病性禽流感的特点是突然发生严重疾病、迅速蔓延，死亡率可在48小时内达到100%。已知流感病毒的所有16 HA (白细胞凝集素)和9 NA (神经氨酸苷酶)均能感染野生水鸟，从而为在野生鸟类中持续不断地循环传播的流感病毒提供了广泛的储主。在野生鸟类中，常规检测几乎总是能发现一些流感病毒。这种病毒大多数是无害的。

在最新一期PNAS，科学家发现了一种蛋白，他们认为这种蛋白可以为鸭提供对流感感染的天然抵抗力。他们提出这种蛋白有可能转移到鸡的细胞中，从而产生类似的免疫应答。鸭和其他野生水禽是全部已知A型流感病毒（几次人类禽流感大流行的元凶）的天然宿主 。野生鸟类感染A型流感的时候通常并不生病，尽管鸡和其他驯化的禽类可能死亡。

Katherine Magor及其同事检查了RIG-I病毒探测器的作用。RIG-I是一种病原体受体，此前被证明能够探测流感病并引发身体的抗病毒免疫应答。这组科学家证明了尽管鸭拥有完整和起作用的RIG-I受体，在A型流感病毒感染的时候激活，相比之下，鸡缺乏这种RNA解旋酶。这组作者报告说，把鸭的RIG-I转入鸡胚可以让鸡细胞探测流感病毒感染并引发抗病毒应答。这组作者说，发现这种天然抗基因有可能让科学家培育出流感抵抗力增加的转基因鸡。

原文出处：

PNAS doi: 10.1073/pnas.1001755107

Association of RIG-I with innate immunity of ducks to influenza
Megan R. W. Barbera, Jerry R. Aldridge Jr.b, Robert G. Websterb,1, and Katharine E. Magora,1

Ducks and wild waterfowl perpetuate all strains of influenza viruses in nature. In their natural host, influenza viruses typically cause asymptomatic infection and little pathology. Ducks are often resistant to influenza viruses capable of killing chickens. Here, we show that the influenza virus sensor, RIG-I, is present in ducks and plays a role in clearing an influenza infection. We show evidence suggesting that RIG-I may be absent in chickens, providing a plausible explanation for their increased susceptibility to influenza viruses compared with ducks. RIG-I detects RNA ligands derived from uncapped viral transcripts and initiates the IFN response. In this study, we show that the chicken embryonic fibroblast cell line, DF-1, cannot respond to a RIG-I ligand. However, transfection of duck RIG-I into DF-1 cells rescues the detection of ligand and induces IFN-β promoter activity. Additionally, DF-1 cells expressing duck RIG-I have an augmented IFN response resulting in decreased influenza replication after challenge with either low or highly pathogenic avian influenza virus. Implicating RIG-I in the antiviral response to an infection in vivo, we found that RIG-I expression is induced 200 fold, early in an innate immune response in ducks challenged with the H5N1 virus A/Vietnam/1203/04. Finding this natural disease resistance gene in ducks opens the possibility of increasing influenza resistance through creation of a transgenic chicken.