Mechanism of viral RNP recognition by the envelope glycoprotein and its role in RNA segment packaging in Rift Valley Fever phlebovirus

裂谷热白喉病毒(RVFV)是一种本亚病毒，属于NIAID A类病原体名单和疾控中心潜在生物恐怖主义因素名单。RVFV引起一种在撒哈拉以南非洲流行的疾病，并可能以蚊媒传播的爆炸性流行病出现，导致成群的羊和牛死亡，造成巨大的经济损失。在人类中，RVFV感染可能会导致出血热、脑炎和视网膜血管炎。许多不同的蚊子，包括几种原产于北美的蚊子，都是RVFV传播的合格媒介。RVFV引入北美可能会在普通人群中引起恐慌，对牲畜的影响可能会对经济产生毁灭性的影响。缺乏用于人类或家畜的许可疫苗或抗RVFV试剂令人极为关切。RVFV基因组包括编码L蛋白的L RNA，编码Gn和GC两种主要包膜糖蛋白的MRNA，以及编码N和Nss的S RNA。NSS是有效抑制宿主抗病毒反应的主要毒力因子。S RNA采用双义策略进行基因表达；NSS是从反基因组意义上的S RNA转录而来的，而N蛋白是从基因组意义上的S RNA转录而来的。病毒复制和传播的重要步骤之一是将病毒基因组包装成病毒颗粒，然而，病毒RNA包装在RVFV和其他布尼亚病毒中的机制在很大程度上是未知的。深入了解病毒RNA基因组包装成RVFV颗粒的潜在规则和机制，对于理解病毒复制、病毒进化和病毒致病机制具有重要意义。这一知识对于开发能够抑制传染性病毒产生的抗病毒药物或开发活疫苗株也是至关重要的。我们认为，Gn与病毒RNA片段的直接相互作用是影响病毒RNA包装成RVFV颗粒的主要因素。本应用将通过表征Gn与抗基因组S RNA的直接相互作用，阐明将抗基因组S RNA高效包装到病毒颗粒中的机制和生物学意义，鉴定病毒RNA中的Gn结合部位，并检测抗基因组S RNA包装对轮状病毒复制的重要性。从拟议的研究中获得的数据将阐明驱动RVFV和其他布尼亚病毒中病毒RNA包装的基本机制，总体目标是为新型抗病毒药物和疫苗的设计提供信息。

Rift Valley fever Phlebovirus (RVFV), a bunyavirus, belongs to the NIAID Category A list of pathogens and the CDC list of potential bioterrorism agents. RVFV causes a disease that is endemic in sub-Saharan Africa and can emerge in explosive, mosquito-borne epidemics that decimate herds of sheep and cattle, resulting in enormous economic losses. In humans, RVFV infection may cause hemorrhagic fever, encephalitis, and retinal vasculitis. Many different mosquitoes, including several species native to North America, are competent vectors for RVFV transmission. The introduction of RVFV into North America would likely cause panic in the general population, and the effects on livestock could have a devastating economic impact. The lack of availability of licensed vaccines or anti-RVFV reagents for use in humans or domestic animals is of great concern. RVFV carries a tripartite, single-stranded, negative-sense RNA genome, including L RNA encoding L protein, M RNA encoding two major envelope glycoproteins, Gn and Gc, and S RNA encoding N and NSs. NSs is the major virulence factor that efficiently suppresses host antiviral responses. The S RNA uses an ambi-sense strategy for gene expression; NSs is translated from the mRNA that is transcribed from the antigenomic-sense S RNA, whereas N protein is produced from the mRNA that is transcribed from the genomic-sense S RNA. One of the essential steps in virus replication and dissemination is the packaging of viral genome into virus particles, however, the mechanisms of viral RNA packaging in RVFV and other bunyaviruses are largely unknown. Insight into the underlying rules and mechanisms that govern the packaging of viral RNA genome into RVFV particles is valuable for understanding the regulation of virus replication, virus evolution, and the pathogenesis of the virus. This knowledge is also critical for the development of antiviral drugs that can inhibit infectious virus production or for the development of a live- attenuated vaccine strain. We propose that a direct interaction of Gn with the viral RNA segments is the primary factor that influences the packaging efficiencies of viral RNAs into RVFV particles. The present application will clarify the mechanism and biological significance of efficient packaging of antigenomic S RNA into virus particles by characterizing the direct interaction of Gn with antigenomic S RNA, identify the Gn- binding sites in viral RNAs, and examine the importance of antigenomic S RNA packaging for RVFV replication. The data obtained from the proposed studies will clarify the fundamental mechanisms that drive viral RNA packaging in RVFV and other bunyaviruses, with the overall goal of informing the design of novel antivirals and vaccines.