RNA-based immunity against flaviviruses in arthropods and mammalian cells

因为它们在细胞内复制，并且在很大程度上依赖宿主分子机制进行复制，所以病毒必须应对基于细胞对其基因组识别的多种防御机制。这导致了一场永无止境的军备竞赛，在这场竞赛中，病原体和宿主必须共同进化，分别避免和加强免疫反应的检测和清除。尽管如此，这种对宿主生物的严格依赖也使它们变得脆弱，特别是在感染的早期阶段，因为它们必须在它们感染的细胞中揭示它们的基因组。因此，对外来核酸的感知代表了整个进化过程中抗病毒防御的共同特征。过去三十年的研究表明，病毒核酸，特别是RNA，是一种重要的分子模式，可以被细胞质受体感知。代表危险信号的关键特征之一是长双链RNA，它是在RNA复制过程中产生的，或者是通过聚合转录产生的。因此，所有真核生物都进化出了一种基于dsRNA感知受体的先天免疫反应。在这个项目中，我们建议研究细胞对通过节肢动物传播给人类的病毒的反应，以鉴定和表征参与病毒核酸感知的复合物，更具体地关注dsRNA。我们将研究由蚊子或蜱传播的黄病毒科病毒。更确切地说，我们将重点关注寨卡病毒和蜱传脑炎病毒。这些病毒将在人类细胞和昆虫系统（如蚊子和蜱虫细胞）中进行研究。我们还将在整个生物体的水平上工作，通过使用遗传上可适应的果蝇模型，蚊子和蜱虫。由于虫媒病毒必须面对不同的防御机制，这取决于它们在特定时间感染的宿主，因此它们提供了一个独特的机会，可以精确地揭示在病毒传播周期的每个末端，与基于dsrna的先天免疫有关的因素。因此，本应用程序的目标是研究三种生物（人类，蚊子，蜱虫）中的病毒感染，通过(i)鉴定参与dsRNA识别和传感的蛋白质来了解抗病毒先天免疫系统；（ii）确定这些蛋白质中哪些具有抗病毒活性和（iii）剖析最有希望的因子的分子和细胞作用模式。我们的研究结果将为科学界提供人类或节肢动物细胞区分自我和非自我RNA的详细机制，并可能为设计新的治疗方法铺平道路。

Because they replicate inside cells and rely for the most part on the host molecular machineries for their replication, viruses have to deal with multiple defense mechanisms based on the recognition of their genome by the cell. This leads to a never-ending arms race in which the pathogen and its host have to co-evolve to respectively avoid and reinforce detection and clearance by the immune response. Nonetheless, this strict dependency on a host organism also makes them vulnerable, especially in the very early steps of the infection, since they have to unveil their genome in the cells they infect. For this reason, the sensing of foreign nucleic acids represents a common characteristic of the antiviral defense throughout evolution. Work over the past thirty years has revealed that viral nucleic acids, and in particular RNA, are important molecular patterns that can be sensed by cytosolic receptors. One of the key features representing a danger signal, is long double-stranded (ds) RNA, generated during RNA replication, or by convergent transcription. As a result, all eukaryotes have evolved an innate immune response based on dsRNA sensing receptors.In this project, we propose to study cellular responses to viruses transmitted to humans by arthropods to identify and characterize complexes involved in the sensing of viral nucleic acids, focusing more specifically on dsRNA. We will study viruses from the Flaviviridae family that are transmitted by mosquitoes or ticks. More precisely, we will focus on Zika virus (ZIKV) and tick-borne encephalitis virus (TBEV). These viruses will be studied both in human cells and in insect systems such as mosquito and tick cells. We will also work at the level of the whole organism by using the genetically amenable Drosophila model, mosquitoes and ticks. Because arboviruses have to face different defense mechanisms depending on the host they infect at a given time, they offer a unique opportunity to unravel precisely the factors involved in dsRNA-based innate immunity at each end of the viral propagation cycle. The goal of this application is therefore to study viral infections in three organisms (human, mosquito, tick) to understand the antiviral innate immune system by (i) identifying the proteins involved in dsRNA recognition and sensing; (ii) determining which of these proteins have pro- or anti-viral activities and (iii) dissecting the molecular and cellular mode of action of the most promising factors. Our results will provide the community with a detailed picture of the mechanisms used by the human or arthropod cell to discriminate between self and non-self RNA and might pave the way toward designing novel therapeutic approaches.