The role of ANTi-RVFV Immunity in GermliNe infection and bEhavior modulation in insects (ANTIGoNE)

虫媒病毒在脊椎动物宿主和节肢动物媒介之间传播。这些病毒中的许多在哺乳动物宿主中引起神经缺陷或流产。然而，昆虫中的感染表型没有很好地表征。昆虫对这些虫媒病毒的免疫反应是保持受感染昆虫足够健康的关键，以使宿主能够找到并产生后代，这是病毒传播的两个主要影响因素。昆虫的免疫系统主要依靠抗病毒RNA干扰来对抗各种不同的病毒病原体。该RNAi机制通过RNAse III酶Dicer-2（Dcr-2）识别和切割双链（ds）RNA而启动，然后通过RNA诱导沉默复合物（RISC）（包括Argonaute 2（Ago 2）蛋白）降解侵入的病毒基因组。此外，皮尔纳途径在生殖细胞中是活跃的，以保护基因组通过转座因子的移动而免受大规模破坏。在过去的几年中，还描述了源自虫媒病毒基因组的piRNA，提出了它们在昆虫免疫应答中的作用的问题。生殖系组织中的Pi和siRNA反应在虫媒病毒感染中特别令人感兴趣，因为这些病毒中的许多在蚊子种群内垂直传播。特别是布尼亚病毒目的病毒通过生殖系有效地传播给蚊子后代，而不影响蚊子后代的健康。相反，布尼亚病毒传播给哺乳动物的后代会导致胎儿发育严重异常，并经常导致流产。这就提出了一个问题：昆虫如何保持允许病毒复制和保护后代健康以允许跨卵传播的微妙平衡。此外，蚊子中的病原体感染可诱导行为变化;例如，感染了拉克罗斯病毒（布尼亚病毒科）的三列伊蚊（Aedes triseriatus）蚊子显示出比未感染的同胞更高的探测频率，并且神经元细胞上的寨卡病毒（黄病毒科）感染增加了埃及伊蚊（Aedes aegypti）中的神经元活动。这些意见提出了一个问题：虫媒病毒通过什么机制影响昆虫的神经元功能（通过感染直接损伤神经元或通过免疫途径激活间接损伤）。为了解决这两个问题，我们将使用裂谷热病毒的感染模型（布尼亚病毒科，RVFV）在模型昆虫黑腹果蝇中的感染，并测量病毒在不同组织中的生长，生殖系和神经组织的免疫反应以及通过不同的行为测定和触角电位图观察感染个体的行为。这些研究将有助于我们分析昆虫寄主寻求行为的适应性变化及其潜在的分子机制，以及抗病毒途径在生殖细胞感染中的作用。

Arboviruses are transmitted between vertebrate host and arthropod vectors. Many of these viruses cause neurological defects or abortions in mammalian hosts. However, infection phenotypes in insects are not well characterized. The insect immune response to these arthropod-borne (arbo) viruses is key to keep infected insects sufficiently healthy to enable host finding and production of offspring, two of the major influencing factors for virus transmission. The insects' immune system relies mainly on antiviral RNA interference to combat a larger variety of different viral pathogens. This RNAi mechanism is initiated by the recognition and cleavage of double-stranded (ds) RNA by the RNAseIII enzyme Dicer-2 (Dcr-2) which then leads to degradation of intruding viral genomes by the RNA-induced silencing complex (RISC) including the Argonaute 2 (Ago2) protein. Furthermore, piRNA pathways are active in the germline cells to protect genomes form massive disruption through movement of transposable elements. In the past years, also piRNAs originating from arbovirus genomes were described raising the question of their role in insect’s immune responses. Pi and siRNA responses in germline tissues are of special interest in arbovirus infection since many of those viruses are transmitted vertically within a mosquito population. Especially viruses of the order Bunyavirales are efficiently transmitted through the germline to mosquito offspring without affecting the health of mosquito offspring. In contrast, the transmission of bunyaviruses to the offspring of mammals leads to severe abnormality in fetus development and often results in abortion. This raises the question how insects keep the delicate balance of allowing viral replication and the protection of offspring health to allow transovarial transmission. Furthermore, pathogen infection in mosquitoes can induce behavioral changes; for example Aedes triseriatus mosquitoes infected with La Crosse virus (Bunyaviridae) show a higher probing frequency than uninfected siblings and Zika virus (Flaviviridae) infection on neuronal cells increases neuronal activity in Aedes aegypti. These observations raise the question: By which mechanisms do arboviruses affect neuron function in insects (direct damage to neurons by infection or indirect damage by immune pathway activation).To tackle both questions, we will use the infection models for Rift valley fever virus (Bunyaviridae, RVFV) in the model insect Drosophila melanogaster and measure virus growth in different tissues, immune reaction in germlines and neuronal tissues and behavior in infected individuals by a different behavioral assays and electroantennograms. The proposed studies will help us to analyze adaptive changes in insects host seeking behavior and the underlying molecular mechanisms as well as the role of antiviral pathways in infection of germline cells.