Mechanisms of measles virus CNS adaptation

 描述（由申请方提供）：麻疹病毒（MV）是发展中国家儿童死亡的主要原因，尽管减毒活疫苗可用于超过40%的儿童， 年严重免疫功能低下的人特别容易患MV。MV在世界各地引起周期性爆发;在美国，我们正处于全国范围的疫情爆发之中虽然自然感染MV可增强持久免疫力，但接种疫苗的人的保护作用减弱。MV感染的最严重表现，包括脑炎，发生在细胞免疫受损的人中。MV在多达一半的常规病例中影响中枢神经系统（CNS）;有足够的细胞免疫力，感染被根除，但个体 细胞免疫力受损的人处于不利地位。即使是疫苗株也可能导致这些人致命的脑炎。 在南非最近的MV爆发中，有几人死于MV CNS感染。我们分析了来自这些患者的病毒，发现MV融合机制-受体结合蛋白（H）+融合蛋白（F）-发生了特异性宿主内进化。“CNS适应”病毒的F中的突变允许其促进融合，而较少依赖于H与两种已知MV细胞受体的相互作用;该F独立于H或受体被激活。我们假设，在缺乏有效的细胞免疫，MV变异轴承融合机制，使有效的传播在中枢神经系统进行积极的选择。我们建议确定MV在宿主中侵入CNS的分子决定因素，并确定这些“CNS适应”病毒是否可以在个体之间传播。在目标1中，我们将鉴定野生型（wt）MV和CNS适应病毒的H/F融合机制之间的遗传和功能差异，以将临床模式与特定融合特性相关联。在目标2中，我们将确定CNS分离株中的H/F改变是否允许通过正常感染途径传播至完整或免疫抑制宿主。需要采取预防麻疹感染的战略，以保护免疫力不足或没有免疫力的人，他们不能接种疫苗。我们建议预防MV感染免疫受损的个体必须在早期阶段停止感染，以避免致命的后果。目的3将在体外、离体和体内评价抗MV感染的融合抑制肽。将在棉鼠中测试MV的特异性抗病毒疗法对wt MV和“CNS适应”临床分离病毒的效力。该计划的长期目标是开发一种安全高效的鼻内融合蛋白（F）抑制剂，用于暴发期间的预防 situations.美国目前的MV疫情凸显了这项工作的紧迫性。 该项目将导致对MV适应CNS嗜性的机制和风险的充分理解，并导致稳定，易于运输的鼻内抗病毒药物，以保护MV爆发期间的风险人群。

 DESCRIPTION (provided by applicant): Measles virus (MV) is a leading cause of child mortality in developing countries despite the availability of a live attenuated vaccine for over 40 years. Severely immune-compromised people are particularly at risk for MV. MV causes periodic outbreaks all over the world; in the U.S., we are in the midst of a nation-wide outbreak. While natural infection with MV elicits long-lasting immunity, protection wanes in vaccinated persons. The most serious manifestations of MV infection, including encephalitis, occur in people with impaired cellular immunity. MV affects the central nervous system (CNS) in up to half of routine cases; with adequate cellular immunity the infection is eradicated, but individuals with impaired cellular immunity are at a disadvantage. Even the vaccine strain can lead to fatal encephalitis in such persons. In a recent MV outbreak in South Africa several people died of MV CNS infection. We analyzed the viruses from these patients and found that specific intra-host evolution of the MV fusion machinery -- receptor binding protein (H) + fusion protein (F) -- had occurred. A mutation in F of the "CNS-adapted" viruses allows it to promote fusion with less dependence on interaction of H with the two known MV cellular receptors; this F is activated independently of H or receptor. We hypothesize that in the absence of effective cellular immunity, MV variants bearing fusion machinery that enabled efficient spread in the CNS underwent positive selection. We propose to identify the molecular determinants of CNS invasion by MV in the host, and determine whether these "CNS-adapted" viruses can spread between individuals. In aim 1 we will identify the genetic and functional differences between the H/F fusion machinery of wild-type (wt) MV and the CNS-adapted viruses, to correlate clinical pattern with specific fusion properties. In aim 2 we will determine whether the H/F alterations in the CNS isolates permit transmission to intact or immune-suppressed hosts via normal routes of infection. Strategies to prevent measles infection are needed to protect people with inadequate or no immunity who cannot be vaccinated. We propose that prevention of MV infection immune-compromised individuals must halt infection at an early stage to avoid fatal consequences. Aim 3 will evaluate fusion inhibitor peptides against MV infection in vitro, ex vivo, and in vivo. A specific antiviral therapy for MV will be tested in cotton rats for its efficacy against wt MV and he "CNS-adapted" clinical isolate viruses. The long-term objective of this plan is to develop a safe and highly effective intranasal fusion protein (F) inhibitor as prophylaxis for use during outbreak situations. The current MV outbreak in the US highlights the urgency of this work. The project will lead to a full understanding of the mechanism and risks of MV adaptation to CNS tropism, and to a stable, easily transported intranasal antiviral to protect people at risk during MV outbreaks.