Molecular mechanisms of host restriction of arenaviruses and viral antagonism

全球问题：从自然动物宿主中溢出到人类的病毒引起的疾病很难预测。受多种环境、生物和生活方式因素的影响，新出现和重新出现的病毒感染在21世纪越来越频繁地发生，特别是在缺乏有效措施来预防和控制有可能发展成病毒大流行的流行病的情况下。拉沙热（LF）等沙粒病毒性出血热是西非和南美洲的地方病，被世界卫生组织（世卫组织）列为需要紧急研究和开发措施的疾病。人与人之间的传播是通过皮肤直接接触受感染的啮齿动物的粪便或尿液、摄入受污染的食物或通过呼吸道接触啮齿动物的排泄物，导致从轻微的流感样综合征到严重和高度致命的出血性疾病。最近在尼日利亚爆发拉沙病毒（LASV）的频率增加，强调这些病毒不应再被视为散发性流行病的原因。由于缺乏疫苗和有效治疗，这些疫情在尼日利亚和其他流行国家造成的巨大公共卫生和社会经济影响进一步加剧。背景资料：宿主保护过程（即细胞免疫）与病毒复制之间的相互作用是沙粒病毒感染期间疾病结局的关键决定因素;对入侵病原体的第一线防御机制的有效抑制是LASV感染的标志。宿主限制因子是对感染的内在抗病毒应答的蛋白质组分。这些蛋白质在关键步骤中起作用，以有效地抑制病毒进入、复制和离开宿主细胞。我首次证明了锌金属蛋白酶ZMPSTE 24对病毒进入的限制，以及ZMPSTE 24和另一种宿主限制因子家族-干扰素诱导的跨膜蛋白（IFITM）的新型协同抑制活性。病毒进入是病毒宿主范围、有效感染特定细胞类型的能力和疾病结果的关键决定因素，因此，靶向沙粒病毒生命周期的这一步骤可能对控制病毒感染产生重大影响。我的研究将解决现有的知识差距，阻碍更深入地了解沙粒病毒与人类宿主细胞的相互作用，以及迫切需要确定新的抗病毒治疗选择。我将定义抑制沙粒病毒进入的ZMPSTE 24和IFITM宿主因子的机制，揭示涉及这些宿主因子的沙粒病毒感染动力学的细节，并确定允许逃离这些宿主抑制压力的病毒生命周期适应。关键目标：1）确定ZMPSTE 24和IFITM对细胞感染屏障结构的物理作用，即支持ZMPSTE 24和IFITM机制的膜，2）解释沙粒病毒蛋白在克服ZMPSTE 24-IFITM活性中的作用，和3）揭示ZMPSTE 24的抗病毒机制如何塑造沙粒病毒生命周期，总之，这项研究将确定和验证沙粒病毒调节的过程，从而为长期开发特异性和有效的抗病毒药物提供关键信息。这项研究得到了强有力的初步数据的支持，并受益于我的专业知识以及与其他沙粒病毒专家和生物物理化学家的密切合作。我还与尼日利亚的传染病流行病学家合作，因此在未来，该提案将旨在通过在被确定为易受沙粒病毒爆发影响的地区的公众参与，加速和整合以社区为重点的方法，以预防未来的流行病。

The Global Issue: Disease emergence from viruses that spill-over to humans from their natural animal reservoir host is difficult to predict. Influenced by several environmental, biological and lifestyle factors, emerging and re-emerging viral infections are occurring with increasing frequency in the 21st century, particularly in the absence of effective measures to prevent and control epidemics that have the potential to develop into virus pandemics. Endemic to West Africa and South America, arenaviral haemorrhagic fevers, such as Lassa fever (LF), are on the priority list of the World Health Organisation (WHO) as diseases requiring urgent research and development measures. Human transmission occurs through direct skin contact with infected rodent faeces or urine, ingestion of contaminated food, or through respiratory exposure to rodent excreta, resulting in illnesses ranging from mild flu-like syndromes to severe and highly fatal haemorrhagic diseases. Recent increased frequency of outbreaks in Nigeria of Lassa virus (LASV) has emphasised that these viruses should no longer be treated as causes of sporadic epidemics. The immense public health and socio-economic impact of these outbreaks in Nigeria and other endemic countries is further exacerbated by the lack of vaccines and effective treatments. Background: The interplay between host protective processes, i.e. cellular immunity, and viral replication is a key determinant of disease outcome during arenavirus infection; with potent suppression of the first line of defence mechanisms against invading pathogens being a hallmark of LASV infection. Host restriction factors are protein components of the intrinsic anti-viral response to infection. These proteins act at crucial steps to potently inhibit viral entry, replication and exit from the host cell. I have for the first time demonstrated a restriction of virus entry by the zinc metalloprotease, ZMPSTE24 and a novel synergistic inhibitory activity by ZMPSTE24 and another host restriction factor family - the interferon-induced transmembrane proteins (IFITMs). Virus entry is a key determinant of viral host range, of the ability to productively infect particular cell types, and of disease outcome, hence, targeting this step of the arenavirus lifecycle could have significant impact on the control of viral infection.Overarching aim: My research will address the existing knowledge gaps that hamper a deeper understanding of arenavirus interactions with human host cells and the urgent need to identify novel anti-viral therapeutic options. I will define the mechanisms of the ZMPSTE24 and IFITM host factors that inhibit arenavirus entry, unravel details of arenavirus infection dynamics that involve these host factors and determine the virus life cycle adaptations that allow escape from these host inhibition pressures. Key Objectives: 1) Determine the physical effects that ZMPSTE24 and IFITMs have on the structure of the cell's barriers to infection, i.e. membranes, that underpin the mechanism of ZMPSTE24 and IFITMs, 2) Explain the role of arenavirus proteins in overcoming ZMPSTE24-IFITM activity, and 3) Reveal how the antiviral mechanisms of ZMPSTE24 shape the arenavirus life cycle, thus opening up potential avenues for targeted therapeutic strategies.Altogether, this study will identify and characterise the processes that are modulated by arenaviruses, thus providing key information for the development of specific and effective antivirals, in the longer term. This research is underpinned by strong preliminary data and benefits from my expertise and strong collaborations with other arenavirus experts and biophysical chemists. I also collaborate with infectious disease epidemiologists in Nigeria, hence in the future, this proposal will aim to accelerate and integrate community-focused approaches to prevent future epidemics through public engagement in regions identified as vulnerable to arenavirus outbreaks.