Genotypic and Phenotypic Analysis of West Nile virus, Yucatan Peninsula of Mexico

描述（由申请人提供）：西尼罗河病毒（WNV）在西半球的首次爆发发生在1999年的纽约，从那时起，该病毒迅速蔓延到美国和加拿大，在那里它导致了显著的人类发病率和死亡率。相比之下，墨西哥尤卡坦半岛（YP）没有人感染西尼罗河病毒，也没有任何关于该地区马或鸟类普遍感染西尼罗河病毒相关疾病的报告，尽管有西尼罗河病毒活动的证据。事实上，我们和我们在梅里达尤卡坦自治大学（DAY）的墨西哥同事在YP的马，鸟类和其他脊椎动物中检测到了WNV抗体。然而，与这一建议最相关的是在科苏梅尔岛进行的血清学调查的结果;在144匹马中的75匹（52%）中检测到西尼罗河病毒抗体，但没有一匹马有疾病迹象，也没有一匹马有类似西尼罗河病毒的疾病史。因此，这项提案的基本假设是，YP中占主导地位的WNV变体在基因型和表型上与美国占主导地位的WNV变体不同。在这项资助中，我们和我们在UAY的同事将获得YP中的WNV分离株，并定义其基因型和细胞培养表型。在具体目标1中，将在YP中先前已确定血清反应阳性脊椎动物的地点诱捕蚊子。将通过RT-PCR和病毒分离对蚊子进行西尼罗河病毒检测。这些研究将确定西尼罗河病毒在YP的可能载体，从而为未来的载体能力和宿主喂养行为的研究奠定基础。在具体目标2中，将通过部分核苷酸测序和系统发育分析来检查WNV分离株。将对优势WNV变体进行完全测序。在具体目标3中，将比较来自YP和美国的显性WNV变体的细胞培养表型（即复制动力学和产量、空斑形态和温度敏感性）。这些研究将为今后在脊椎动物宿主体内的发病机制研究奠定基础。相关性：在这个提议中，YP中显性WNV变体的基因型和细胞培养表型将被表征，并且将鉴定该区域中可能的WNV载体。这些信息将有助于确定为什么YP中没有WNV流行，并将确定与WNV疾病相关的风险因素。

DESCRIPTION (provided by applicant): The initial outbreak of West Nile virus (WNV) in the Western Hemisphere occurred in New York in 1999, and since then the virus has rapidly spread across the United States and Canada, where it has been responsible for significant human morbidity and mortality. In contrast, there have been no human cases of WNV in the Yucatan Peninsula (YP) of Mexico, nor have there been any reports of widespread WNV associated illness in horses or birds in this region, despite evidence of WNV activity. Indeed, we and our Mexican colleagues at the Universidad Autonoma de Yucatan (DAY) in Merida detected antibodies to WNV in horses, birds and other vertebrate animals in the YP. Most pertinent to this proposal, however, are the findings from a serosurvey conducted on Cozumel Island; antibodies to WNV were detected in 75 of 144 (52%) horses, but none of the horses had signs of illness and none had a history of WNV-like illness. Thus, the underlying hypothesis in this proposal is that the dominant WNV variants in the YP are genotypically and phenotypically distinct from the dominant WNV variants in the U.S. In this grant, we and our colleagues at the UAY will obtain WNV isolates in the YP, and define their genotypes and cell culture phenotypes. In specific aim 1, mosquitoes will be trapped at sites in the YP where seropositive vertebrates have previously been identified. Mosquitoes will be assayed for WNV by RT-PCR and virus isolation. These studies will identify likely vectors of WNV in the YP, thereby providing the groundwork for future vector competence and host-feeding behavior studies. In specific aim 2, WNV isolates will be examined by partial nucleotide sequencing and phylogenetic analysis. Dominant WNV variants will be completely sequenced. In specific aim 3, the cell culture phenotypes (i.e. replication kinetics and yields, plaque morphologies and temperature sensitivities) of dominant WNV variants from the YP and U.S. will be compared. These studies will provide the groundwork for future in vivo pathogenesis studies in vertebrate hosts. RELEVANCE: In this proposal, the genotypes and cell culture phenotypes of dominant WNV variants in the YP will be characterized, and likely vectors of WNV in this region will be identified. This information will help determine why there has not been an epidemic of WNV in the YP, and will identify risk factors associated with WNV disease.