Defining the Molecular Determinants of Encephalitic Alphavirus Viremia

项目总结 本研究旨在对甲型脑炎病毒感染过程中病毒血症的发展进行比较研究。 以及在特定的疾病发生之前，调节循环病毒清除的先天免疫机制 抗体反应。东部(EEEV)和委内瑞拉(VEEV)马脑炎病毒是蚊子- 由于能够传染给人和马而引起高度公共卫生关注的传播性人畜共患病 造成神经系统疾病和死亡，目前尚无具体的治疗方法。地方病 在美洲，它们的天然宿主是鸟类(EEEV)和啮齿动物种群(VEEV)。天然 这些和其他虫媒病毒的传播依赖于足够多的病毒血症的发展 脊椎动物寄主内的幅度和持续时间。虽然虫媒病毒能够复制(并导致 疾病)在几个脊椎动物物种中，并不是所有的宿主都支持传播回节肢动物媒介。然而， 决定虫媒病毒血症在扩增和“死胡同”宿主中的分子机制还不是很清楚。 我的初步发现与莫里森博士实验室之前的研究形成了有趣的对比 关于致关节炎甲型病毒的血管清除。特别是，我发现静脉接种EEEV 微粒从小鼠循环中清除，而VEEV-IAb微粒逃脱血管清除。我的 有关EEEV从循环中清除的初步数据支持吞噬细胞在控制中的中心作用 然而，与致关节炎的甲型病毒不同，甲型病毒血症的EEEV血管清除发生在 动力学较慢，且不依赖A类清道夫受体(SR)。我假设EEEV血管 清除是由肝脏KC上表达的非A类SR介导的，它识别表面暴露的碱性物质 病毒E2糖蛋白中的补丁和VEEV-IAb逃避清除类似地由 在E2中没有表面暴露的碱性残基。此外，我假设血管清除表型 EEEV和VEEV依赖于宿主物种，并与支持 在自然界中维持这些独立的病毒种群。我建议的研究将：(I)确定东道主和 EEEV被非A类SR清除的病毒分子机制，(Ii)评估EEEV的命运 血管清除后的颗粒，(Iii)鉴定VEEV病毒粒子的生化特性，以确定 小鼠血管清除，以及(Iv)阐明病毒血症在扩大性和“死胡同”中的定义机制 主持人。从这些研究中获得的知识可能有助于识别严重疾病的风险因素，并有助于 开发针对EEEV和VEEV的新疗法或疫苗。

PROJECT SUMMARY This proposal is a comparative study on the development of viremia during encephalitic alphavirus infection and the innate immune mechanisms that mediate clearance of circulating virus in the time before the specific antibody response. Eastern- (EEEV) and Venezuelan- (VEEV) equine encephalitis viruses are mosquito- transmitted zoonoses of high public health concern due to their ability to spill-over into human and equine populations, causing neurologic disease and mortality for which no specific treatments are available. Endemic to the Americas, their natural reservoirs are avian (EEEV) and rodent populations (VEEV). Natural transmission of these and other arboviruses is dependent on the development of a viremia of sufficient amplitude and duration within vertebrate hosts. And while arboviruses are capable of replicating (and causing disease) within several vertebrate species, not all hosts support transmission back to the arthropod vector. Yet, the molecular mechanisms that dictate arboviral viremia in amplifying and “dead-end” hosts are poorly defined. My preliminary findings have identified interesting contrasts from previous studies in Dr. Morrison's laboratory on the vascular clearance of arthritogenic alphaviruses. In particular, I found that intravenous-inoculated EEEV particles are cleared from murine circulation, while VEEV-IAB particles escape vascular clearance. My preliminary data on EEEV clearance from circulation supports a central role for phagocytic cells in the control of alphavirus viremia, however, in contrast to arthritogenic alphaviruses, EEEV vascular clearance occurs with slower kinetics and is independent of class A scavenger receptors (SR). I hypothesize EEEV vascular clearance is mediated by a non-class A SR expressed on liver KC which recognizes a surface-exposed basic patch in the viral E2 glycoprotein, and VEEV-IAB escape from clearance is similarly determined by the absence of a surface-exposed basic residue in E2. Moreover, I hypothesize vascular clearance phenotypes of EEEV and VEEV are host-species dependent and correlate with the distinct vertebrate hosts that support the maintenance of these independent viral populations in nature. My proposed studies will: (i) define the host and viral molecular mechanisms by which EEEV is cleared by a non-class A SR, (ii) assess the fate of EEEV particles following vascular clearance, (iii) identify biochemical properties of VEEV virions that determine murine vascular clearance, and (iv) elucidate mechanisms that define viremia in amplifying versus “dead-end” hosts. The knowledge gained from these studies may help identify risk factors for severe disease and aid the development of new treatments or vaccines against EEEV and VEEV.