Replication of influenza virus at the molecular level

这项拟议研究计划的基本目标是更深入地了解流感病毒的分子和细胞生物学，从而制定防治流感的新战略。流感病毒是人类疾病和死亡的主要原因，并且由于它们能够引起每年的流行病和偶尔的大流行病，它们对全球医疗保健系统造成了相当大的负担。最具破坏性的流感大流行，即1918年的“西班牙”流感，在全世界造成5 000多万人死亡。野鸟是甲型流感病毒的重要宿主，可能从中产生新的大流行毒株。目前，H5N1、H7N7和H9N2亚型被认为是最大的威胁，因为这些亚型在鸟类中普遍存在，可以直接感染人类。虽然这些病毒缺乏在人类之间传播的能力，但它们可能导致严重的疾病和死亡。令人担忧的是，这些病毒通过适应或与其他病毒亚型混合，可能获得在人类之间轻松传播的能力，并导致新的大流行。尽管有季节性流感疫苗和数量非常有限的抗病毒药物，但令人惊讶的是，我们对新出现的大流行性流感病毒毫无防备。制备一种与大流行病毒株相匹配的疫苗可能需要几个月的时间，而抗药性是一个日益严重的问题。因此，需要开发用于控制流感的新策略。拟议研究计划的重点是流感病毒的转录机制。流感病毒是由数种蛋白质组成的复合体，负责在宿主细胞内复制病毒的遗传信息。流感病毒的遗传信息储存在RNA片段中。这些需要复制成信使RNA（转录），翻译成病毒蛋白质，以及复制以产生新的基因组拷贝。然后，这些新的拷贝与病毒蛋白组装在一起，被整合到新的病毒颗粒中，这些病毒颗粒从宿主细胞中释放出来，启动新的病毒繁殖周期。有趣的是，感染鸟类的流感病毒的转录机制往往在人类细胞中工作不佳。当“禽流感”传染给人类时，这种机制通常会发生变化，以适应新的宿主。换句话说，流感病毒的转录机制可以决定病毒可以感染哪些宿主，也可以决定所引起疾病的严重程度和结果。虽然病毒的转录机制以宿主细胞特异性的方式执行必要的功能，没有这些功能病毒就无法生存，我们不了解这台机器在分子水平上是如何工作的，也不知道宿主细胞的物种（无论是鸟类还是人类）如何影响它的功能。因此，我们希望确定病毒转录机制用于转录和复制病毒基因组的分子机制，以及病毒转录机制和宿主细胞之间的分子相互作用。这项研究计划将有助于了解流感病毒的毒力、宿主范围限制和适应新宿主的分子基础。因此，它将有助于更好地了解具有大流行潜力的菌株的出现。重要的是，它将通过在病毒转录机制以及细胞蛋白中识别抗病毒药物的靶点来支持新的抗病毒策略的开发。它还可以促进新型流感疫苗的开发，提供针对各种流感病毒株的保护。在方案执行过程中出现的任何信息都将得到利用，可能会有工业伙伴的参与。

The fundamental aim of this proposed research programme is to develop a much deeper understanding of the molecular and cell biology of influenza viruses, allowing the development of novel strategies to combat influenza. Influenza viruses are a major contributor to disease and death in humans, and with their ability to cause yearly epidemics and occasional pandemics they represent a considerable burden to healthcare systems globally. The most devastating influenza pandemic, the 1918 "Spanish" flu, caused over 50 million deaths worldwide. Wild birds represent an important reservoir for influenza A viruses from which novel pandemic strains can emerge. Currently the H5N1, H7N7 and H9N2 subtypes are considered the biggest threats as these are prevalent in birds and can infect humans directly. Although these viruses lack the ability to transmit between humans, they can cause severe disease and death. The concern is that these viruses, through adaptation or by mixing with other virus subtypes, could gain the ability to easily transmit between humans and lead to a new pandemic. Although vaccines against seasonal influenza and a very limited number of antiviral drugs are available, we are surprisingly defenceless against emerging pandemic influenza viruses. To prepare a vaccine matching a pandemic strain could take several months and resistance to drugs is an increasing problem. Therefore novel strategies for the control of influenza need to be developed. The focus of the proposed research programme is the transcriptional machinery of influenza virus, a complex of several proteins which is responsible for copying the genetic information of the virus in a host cell. The genetic information of influenza virus is stored in segments of RNA. These need to be copied into messenger RNA (transcription) to be translated into viral proteins, as well as replicated to produce new copies of the genome. These new copies are then assembled with viral proteins to be incorporated into new virus particles that are released from the host cell to initiate new cycles of viral reproduction. Interestingly, transcriptional machineries of influenza viruses that infect birds tend to work poorly in human cells. When "bird flu" transmits to humans the machinery usually undergoes changes to become adapted to its new host. In other words, the transcriptional machinery of an influenza virus can determine which host the virus could infect, and can also determine the severity and the outcome of the disease caused.Although the viral transcriptional machinery performs essential functions in a host cell-specific manner without which the virus cannot survive, we do not understand how this machine works at the molecular level or how the host cell's species (whether bird or human) affects its function. We therefore wish to determine the molecular mechanisms used by the viral transcriptional machinery to transcribe and replicate the viral genome, and the molecular interactions between the viral transcriptional machinery and the host cell. This research programme will help to understand the molecular basis of virulence, host range restriction and adaptation of influenza viruses to new hosts. It will therefore allow a better understanding of the emergence of strains with pandemic potential. Importantly, it will underpin the development of novel antiviral strategies by indentifying targets for antiviral drugs in the viral transcriptional machinery as well as in cellular proteins. It could also facilitate the development of novel influenza vaccines, offering protection against a wide variety of influenza virus strains. Any emerging information during the course of the programme will be exploited, potentially with the involvement of industrial partners.