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2013年2月H7N9禽流感病毒在中国大陆人群中出现，到7月的第一个星期，世界卫生组织已记录到133个病例，其中包括43个死亡病例。迄今为止大部分病例都被发现与活禽市场有关。在本期Nature上，两个小组报告了H7N9的受体结合性质。这两个小组都发现，该病毒已获得了结合人“-2,3-linked唾液酸受体”的能力，但却保留了与禽“2,3-linked受体”相结合的偏好，后者是一个可能限制其朝向在人类之间高效传播进一步演化的因子。Steven Gamblin及其同事还解决了H7血凝素在与受体类似物所形成的复合物中的晶体结构，揭示了“人受体结合性质”有可能怎样出现的详细情况。Yuelong Shu及其同事研究了肺组织中的病毒感染模式。在人类气管和肺移植物中，该病毒感染下呼吸道中的上皮细胞和肺泡中的II-型肺细胞，与气管相比能更好地在下呼吸道中复制，这可能是它迄今不能在人与人之间进行高效传播的一个因素。他们还报告了在一些患者中所发现的“高细胞因子血症”(它是一种“细胞因子风暴”，对疾病的严重程度会有贡献)，与在一些H5N1感染中所见的这种血症具有可比性。(生物谷 Bioon.com)
生物谷推荐的英文摘要
Nature doi:10.1038/nature12372
Receptor binding by an H7N9 influenza virus from humans
Xiaoli Xiong, Stephen R. Martin, Lesley F. Haire, Stephen A. Wharton, Rodney S. Daniels, Michael S. Bennett, John W. McCauley, Patrick J. Collins, Philip A. Walker, John J. Skehel & Steven J. Gamblin
Of the 132 people known to have been infected with H7N9 influenza viruses in China, 37 died, and many were severely ill1. Infection seems to have involved contact with infected poultry2, 3. We have examined the receptor-binding properties of this H7N9 virus and compared them with those of an avian H7N3 virus. We find that the human H7 virus has significantly higher affinity for α-2,6-linked sialic acid analogues (‘human receptor’) than avian H7 while retaining the strong binding to α-2,3-linked sialic acid analogues (‘avian receptor’) characteristic of avian viruses. The human H7 virus does not, therefore, have the preference for human versus avian receptors characteristic of pandemic viruses. X-ray crystallography of the receptor-binding protein, haemagglutinin (HA), in complex with receptor analogues indicates that both human and avian receptors adopt different conformations when bound to human H7 HA than they do when bound to avian H7 HA. Human receptor bound to human H7 HA exits the binding site in a different direction to that seen in complexes formed by HAs from pandemic viruses4, 5 and from an aerosol-transmissible H5 mutant6. The human-receptor-binding properties of human H7 probably arise from the introduction of two bulky hydrophobic residues by the substitutions Gln226Leu and Gly186Val. The former is shared with the 1957 H2 and 1968 H3 pandemic viruses and with the aerosol-transmissible H5 mutant. We conclude that the human H7 virus has acquired some of the receptor-binding characteristics that are typical of pandemic viruses, but its retained preference for avian receptor may restrict its further evolution towards a virus that could transmit efficiently between humans, perhaps by binding to avian-receptor-rich mucins in the human respiratory tract7 rather than to cellular receptors.
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