The role of TRPM8 in susceptibility to highly pathogenic avian influenza A/H5N1

在过去的十年中，一种动物甲型流感病毒跨越了物种障碍，并在五次情况下导致了相当数量的人类病例。高致病性禽流感A(H5N1)导致非常罕见的人与人之间的有限传播，但尚未适应人类。2003年，另一种禽流感病毒(H7N7)在荷兰造成了大量人类感染，大多是轻微的，也显示了一些有限的人与人之间传播的能力，但通过广泛扑杀家禽成功地得到了控制。2009年出现的猪H1N1流感病毒成功适应了人类，引发了一场大流行，现在已经确定为人类流感病毒。另一种猪源病毒(H3N2v)自2011年以来在美国偶尔从猪传播给人，但一直未能成功切换宿主并在人类种群中确立。持续的甲型H7N9禽流感疫情于2013年2月在中国首次发现，截至撰写本报告时，已造成130多例人感染病例，并显示出一些适应人类的证据。当动物流感病毒跨越物种屏障感染人类时，出现的一个核心问题是病毒适应人类并导致大流行的可能性。尽管进行了大量研究，但动物流感病毒稳定适应人类所必须克服的障碍仍然没有完全被了解。评估H5N1和其他动物流感病毒对公共卫生的威胁，需要更充分地了解目前是什么限制了动物流感病毒感染人类和在人与人之间传播的能力。与人类适应相关的流感病毒的特征已经得到了详细的研究。然而，对人类-宿主特征的研究要少得多。大约三分之一的人类H5N1病例发生在聚集性，截至2009年3月报告的54个H5N1聚集性病例中，有50个完全由血缘亲属组成。我们和其他作者得出结论，这种家族聚集性和H5N1流行病学的其他方面表明宿主遗传因素可能起到了作用。为了验证我们的假设，即宿主遗传因素可能在限制H5N1易感性方面发挥重要作用，我们进行了一项研究，以寻找可能与感染H5N1病毒风险增加相关的人类遗传因素。我们研究了65名H5N1感染者(病例)和2910名未感染H5N1的人(对照组)，发现一种特定基因(TRPM8)的变异在病例中比对照组更常见。我们继续在实验室和小鼠的细胞中研究该基因对H5N1感染的影响。我们发现，该基因确实影响了H5N1病毒在细胞内的复制能力，并导致小鼠患病。这项新研究的目的是进一步确定和表征TRPM8基因在H5N1感染易感性中的作用。我们将通过(1)收集样本并分析印度尼西亚人H5N1病例的遗传密码来测试遗传变异是否也存在于这组独立的样本中，(2)在病例和对照中对整个TRPM8基因进行完全测序，以准确地确定哪些遗传变异可能是原因，(3)探索不同的流感病毒如何与TRPM8基因产生的蛋白质结合，以及(4)进一步评估TRMP8在小鼠H5N1感染中的作用。这项研究很重要，因为这项研究结果将提供关于动物流感病毒成功感染人类所需的适应的新信息，并可能为预防或治疗流感感染的药物提供新的靶点。

In the last decade an animal influenza A virus has crossed the species barrier and caused an appreciable number of human cases on five occasions. Highly pathogenic avian influenza A(H5N1) has resulted in very rare episodes of limited person-to-person transmission but has not adapted to humans. Another avian influenza virus (H7N7) caused a large number of, mostly mild, human infections in the Netherlands in 2003 and also demonstrated some ability for limited person-to-person transmission, but was successfully controlled by extensive culling of poultry flocks. The swine H1N1 influenza virus that emerged in 2009 successfully adapted to humans, caused a pandemic, and is now firmly established as a human influenza virus. Another swine-origin virus (H3N2v) has been transmitted occasionally from pigs to humans in the U.S. since 2011 but has not managed to switch hosts and become established in the human population. The ongoing avian influenza A(H7N9) outbreak that was first detected in China in February 2013 has caused more than 130 human cases at the time of writing, and shows some evidence of adaptation to humans. A central question that arises when an animal influenza virus crosses the species barrier and infects humans is the probability that the virus will adapt to humans and cause a pandemic. Despite much research, the barriers that must be overcome for animal influenza viruses to stably adapt to humans are still not fully understood. Assessing the public health threat of H5N1 and other animal influenza viruses requires a fuller understanding of what currently constrains the ability of animal influenza viruses to infect humans and to transmit between humans. The characteristics of influenza viruses that are associated with adaptation to humans have been studied in detail. However, the human-host characteristics are much less well studied. Around one third of all human H5N1 cases have occurred in clusters, and 50 of the 54 H5N1 clusters reported as of March 2009 were comprised entirely of blood relatives. We and other authors have concluded that this familial clustering and other aspects of the epidemiology of H5N1 suggest a role for host genetic factors.To test our hypothesis that host genetic factors may play an important role in restricting susceptibility to H5N1, we conducted a study to look for human genetic factors that might be associated with an increased risk of getting H5N1 infection. We studied 65 people with H5N1 infection (cases) and 2,910 people without H5N1 infection (controls) and found a variant in one particular gene (TRPM8) that was more common in cases compared to controls. We went on to study the effect of this gene on H5N1 infection in cells in the laboratory and in mice. We found that this gene did indeed affect the ability of the H5N1 virus to replicate in cells and to cause disease in mice. The aim of this new research is to futher determine and characterize the role of the TRPM8 gene in susceptibility to infection with H5N1. We will do this by (1) gathering samples and analysing the genetic code from human H5N1 cases in Indonesia to test if the genetic variant is also present this independent set of samples, (2) fully sequencing the whole TRPM8 gene in cases and controls to identify precisely which genetic variations may be responsible, (3) exploring how different influenza viruses bind to the protein produced by the TRPM8 gene, and (4) further assessing the role of TRMP8 in H5N1 infection in mice.This research is important since the results will provide new information on the adaptations necessary for animal influenza viruses to succesfully infect humans and may also provide a new target for drugs to prevent or treat influenza infections.