Evolution and pathogenesis of Usutu virus, an emerging arbovirus

项目摘要 西尼罗河病毒（WNV）和西尼罗河病毒（USUV）是密切相关的蚊媒病毒， 人类的神经侵袭性疾病西尼罗河病毒于1999年从非洲和欧洲进入美国，现在它是 美国大陆最常见的蚊媒疾病;然而，没有疫苗或治疗剂， available. USUV正在欧洲兴起，在那里，它至少三次从非洲引进， 候鸟和人类疾病病例正在增加。导致黄病毒增加的病毒因素 发病机制包括自然发生的病毒基因突变和来自共 循环异源黄病毒。我们发现非洲和欧洲的USUV菌株不同， 在野生型小鼠模型中产生的疾病水平显著降低，病毒血症的差异高达 100-USUV菌株之间的折叠。我们还发现，人WNV恢复期血清部分交叉- 在体外中和USUV。该项目的长期目标是了解病毒进化的影响， 黄病毒出现和疾病的抗体交叉反应性。本研究的目的是确定 USUV的基因突变决定了发病机制的差异，并确定WNV是否交叉， 反应性抗体改变USUV疾病。假设病毒在羽化过程中获得突变 增加USUV致病性和异源WNV抗体降低USUV致病性。两 具体的目标将解决这一假设：1）确定USUV疾病的病毒遗传决定因素;和2） 确定西尼罗河病毒抗体对USUV疾病的影响。在第一个目标中，我们建立了一个反向遗传学系统， 最近开发的新技术将用于鉴定改变小鼠病毒血症和疾病的USUV突变。在 第二个目的是评估从人WNV恢复期血清中纯化的IgG对USUV病的作用 in vivo.这里提出的研究是创新的，因为它调查了 使用新型反向遗传学由一种新兴的、被忽视的病毒的当代毒株引起的发病机制 系统在成功完成拟议的研究后，这项工作的预期贡献将是 确定影响USUV发病机制和USUV疾病宿主免疫相关性的病毒因子。 预计这一贡献将是重要的，因为它将导致开发治疗方法的能力， 疫苗，以减少黄病毒的传播和疾病。

Project Summary West Nile virus (WNV) and Usutu virus (USUV) are closely-related mosquito-borne viruses that cause neuroinvasive disease in humans. WNV emerged from African and Europe into the U.S. in 1999, and it is now the most common mosquito-borne disease in the continental U.S.; however, no vaccines or therapeutics are available. USUV is emerging in Europe, where it has been introduced at least three times from Africa by migratory birds, and human disease cases are increasing. The viral factors that lead to increases in flavivirus pathogenesis include naturally-occurring viral genetic mutations and cross-reactive antibodies from co- circulating heterologous flaviviruses. We have found that African and European strains of USUV differ drastically in the level of disease generated in a wild-type mouse model, with differences in viremia of up to 100-fold between USUV strains. We have also found that human WNV convalescent sera partially cross- neutralizes USUV in vitro. The long-term goal of this project is to understand the effect of viral evolution and antibody cross-reactivity on flavivirus emergence and disease. The objectives of this study are to identify the genetic mutations in USUV that dictate differences in pathogenesis and to determine whether WNV cross- reactive antibodies alter USUV disease. The hypothesis is that viral mutations acquired during emergence increase USUV pathogenesis and that heterologous WNV antibodies decrease USUV pathogenesis. Two specific aims will address this hypothesis: 1) Identify viral genetic determinants of USUV disease; and 2) Determine the impact of WNV antibodies on USUV disease. In the first aim, a reverse genetics system that we recently developed will be used to identify mutations in USUV that alter viremia and disease in mice. In the second aim, the effect of IgG purified from human WNV convalescent sera on USUV disease will be evaluated in vivo. The research proposed here is innovative because it investigates significant differences in pathogenesis caused by contemporary strains of an emerging, neglected virus using a novel reverse genetics system. Upon successful completion of the proposed research, the anticipated contribution of this work will be the identification of viral factors that affect USUV pathogenesis and host immune correlates of USUV disease. This contribution is expected to be significant because it will lead to the ability to develop therapeutics and vaccines to reduce flavivirus transmission and disease.