Evolution and pathogenesis of Usutu virus, an emerging arbovirus

项目摘要 西尼罗河病毒(WNV)和Usutu病毒(USUV)是密切相关的蚊媒病毒，可导致 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，现在已经 美国大陆最常见的蚊媒疾病；然而，目前还没有疫苗或疗法 可用。USUV正在欧洲崛起，它至少三次从非洲引进，由 候鸟和人类疾病病例正在增加。导致黄病毒增多的病毒因素 致病机制包括自然发生的病毒基因突变和共同免疫的交叉反应抗体。 传播的异源黄病毒。我们发现非洲和欧洲的USUV品系不同 在野生型小鼠模型中产生的疾病水平急剧下降，病毒血症的差异高达 USUV菌株之间的100倍。我们还发现，人西尼罗河病毒恢复期血清部分交叉。 在体外中和USUV。这个项目的长期目标是了解病毒进化和 抗体在黄病毒出现和疾病上的交叉反应。这项研究的目标是确定 USUV中的基因突变决定了发病机制的差异，并确定西尼罗河病毒是否交叉 反应性抗体会改变USUV疾病。假设是在出现期间获得的病毒突变 增强了USUV的致病作用，而异种WNV抗体降低了USUV的致病作用。二 具体目标将解决这一假设：1)确定USUV疾病的病毒遗传决定因素；以及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 最近开发的将用于识别USUV中改变小鼠病毒血症和疾病的突变。在 第二个目的是评价从人WNV恢复期血清中提纯的Ig G对USUV疾病的治疗作用。 在活体内。这里提出的研究是创新的，因为它调查了 用一种新的反向遗传学研究一种新出现的被忽视病毒的当代毒株引起的致病机制 系统。在成功完成拟议的研究后，这项工作的预期贡献将是 影响USUV发病机制的病毒因素的确定及USUV病的宿主免疫相关性。 这一贡献预计将是重大的，因为它将导致开发治疗学和 减少黄病毒传播和疾病的疫苗。

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.