Identification of genetic determinants that condition flaviviral host specificity

 描述(申请人提供)：大多数黄病毒在脊椎动物宿主和食血节肢动物之间水平传播；因此，这些病毒暴露在不同生物系统施加的适合性限制下，排除了对这两种宿主的特定适应。相比之下，最近描述的其他黄病毒，如库蚊黄病毒(CxFV)，没有已知的脊椎动物宿主，被认为是昆虫特有的。其他病毒，如莫多克病毒(MODV)，是脊椎动物特有的。后两组中的病毒具有宿主特异性适应的潜力，而不需要在每个宿主中保持折衷的适合度水平，以便最大化其整体适合度。这些病毒不同宿主范围和传播周期的进化过程和潜在遗传基础尚未得到解决；然而，双宿主(脊椎动物-蚊子)和单一宿主(蚊子特有和脊椎动物特有)黄病毒的存在使这一系统成为解决其中一些进化限制和由此产生的调节宿主特异性的遗传决定因素的最佳系统。因此，这项应用的总体目标是确定限制双宿主和单宿主黄病毒不同寄主范围、传播性和取向的遗传因素。为实现这一目标制定了三个具体目标。在具体目标1中，将通过评估西尼罗河病毒和CxFV之间产生的嵌合病毒的体外和体内脊椎动物和蚊子感染表型来确定调节双宿主和昆虫特异性黄病毒不同宿主范围的遗传元件。在具体目标2中，将通过表征病毒嵌合体的体外和体内复制表型来进一步确定调节黄病毒宿主范围的遗传决定因素。 在双宿主和脊椎动物特有的黄病毒(分别为西尼罗河病毒和MODV)之间创建。在具体目标3中，将调查最近发现的两种核糖体移码蛋白--一种由所有已知的昆虫特异性黄病毒唯一编码，另一种由西尼罗病毒和所有其他日本脑炎血清组病毒编码--以确定它们在黄病毒宿主适应中的意义。

 DESCRIPTION (provided by applicant): Most flaviviruses are transmitted horizontally between vertebrate hosts and hematophagous arthropods; thus, these viruses are exposed to fitness constraints imposed by disparate biological systems that preclude specific adaptation to either host. In contrast, other recently described flaviviruses, such as Culex flavivirus (CxFV), have no known vertebrate host and are considered to be insect-specific. Others, such as Modoc virus (MODV), are vertebrate-specific. Viruses in the latter two groups have the potential for host-specific adaptation independent of the need to maintain a compromised fitness level in each host in order to maximize their overall fitness. The evolutionary processes and underlying genetic basis for the differential host ranges and transmission cycles of these viruses have yet to be addressed; however, the presence of both dual-host (vertebrate-mosquito) and single-host (mosquito-specific and vertebrate-specific) flaviviruses makes this an optimal system for addressing some of these evolutionary constraints and the resulting genetic determinants that modulate host specificity. Thus, the overall goal of this application is to identify the genetic elements that have conditioned the differential host-ranges, transmissibility's and tropisms of dual-host and single-host Flaviviruses. Three specific aims have been designed to achieve this goal. In specific aim 1, the genetic elements that modulate the differential host ranges of dual-host and insect-specific flaviviruses will be identified by assessing the in vitro and in vivo vertebrate and mosquito infection phenotypes of chimeric viruses created between WNV and CxFV. In specific aim 2, the genetic determinants that modulate flavivirus host range will be further defined by characterizing the in vitro and in vivo replication phenotypes of viral chimeras created between a dual-host and vertebrate- specific flavivirus (WNV and MODV, respectively). In specific aim 3, two recently discovered ribosomal frameshift proteins - one uniquely encoded by all known insect-specific flaviviruses and the other by WNV and all other Japanese encephalitis serogroup viruses - will be investigated in order to determine their significance in flavivirus host adaptation.