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

在过去十年中，一种动物甲型流感病毒跨越了物种障碍，在五个场合造成了相当数量的人类病例。高致病性禽流感A（H5 N1）导致非常罕见的有限人际传播，但尚未适应人类。2003年，另一种禽流感病毒（H7 N7）在荷兰造成了大量的人感染，其中大多数是轻度的，也显示出一定的有限人际传播能力，但通过广泛扑杀家禽群成功地控制了这种病毒。2009年出现的猪H1N1流感病毒成功地适应了人类，引起了大流行，现在已经确定为人类流感病毒。自2011年以来，另一种猪源性病毒（H3 N2 v）偶尔在美国从猪传播给人类，但尚未成功转换宿主并在人群中建立。2013年2月首次在中国发现的持续的甲型H7N9禽流感疫情在撰写本报告时已造成130多例人间病例，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，出现的一个中心问题是病毒适应人类并引起大流行的可能性。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了解。评估H5 N1和其他动物流感病毒对公共卫生的威胁需要更全面地了解目前是什么限制了动物流感病毒感染人类和在人类之间传播的能力。与适应人类有关的流感病毒的特征已被详细研究。然而，人-宿主特性的研究要少得多。在所有人类H5 N1病例中，约有三分之一发生在集群中，截至2009年3月报告的54个H5 N1集群中有50个完全由血亲组成。我们和其他作者的结论是，这种家族聚集性和H5 N1流行病学的其他方面表明宿主遗传因素的作用。为了验证我们的假设，即宿主遗传因素可能在限制对H5 N1的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H5 N1感染风险增加相关的人类遗传因素。我们研究了65名H5 N1感染者（病例）和2，910名未感染H5 N1的人（对照组），发现一种特定基因（TRPM 8）的变异在病例中比对照组更常见。我们接着在实验室细胞和小鼠中研究了这种基因对H5 N1感染的影响。我们发现，这个基因确实影响了H5 N1病毒在细胞中复制的能力，并在小鼠中引起疾病。这项新研究的目的是进一步确定和表征TRPM 8基因在H5 N1感染易感性中的作用。我们将通过以下方式做到这一点：（1）收集印度尼西亚人类H5 N1病例的样本并分析遗传密码，以测试遗传变异是否也存在于这一独立样本组中，（2）对病例和对照组中的整个TRPM 8基因进行全面测序，以准确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TRPM 8基因产生的蛋白质结合，（4）进一步评估TRMP 8在小鼠感染H5 N1中的作用，该研究结果将为动物流感病毒成功感染人类所需的适应性提供新的信息，也可能为预防或治疗流感感染的药物提供新的靶点，因此具有重要意义。

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.