EVOLUTIONARY CONSEQUENCES OF DENGUE VIRUS EMERGENCE

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 登革病毒(黄病毒属)是节肢动物传播的病毒中对公众健康威胁最大的病毒，在两个不同的生命周期中传播。引起人类登革热的流行性登革热病毒在人类和周围型伊蚊之间循环。森林登革热病毒在非洲和亚洲的森林树冠上在森林伊蚊物种和非人类灵长类之间循环。地方性病毒和地方性病毒显示出很高的序列同源性，但地方性病毒不会在人类中引起疫情。我们最初的假设解释了这一明显的悖论，即一种“适应性屏障”阻止了登革热病毒的出现，或者更具体地说，登革热病毒在人类或斑纹伊蚊物种中的复制能力很差。然而，在与INBRE导师Scott Weaver(UTMB)和他的实验室成员的合作中，我们已经证明了不存在这样的适应障碍，因为DENV血清型2(DENV-2)的病毒株和地方性毒株(DENV-2)对于人类病毒复制的模型具有同等的传染性(Vasilakis等人)。2007年，Vaslakis等人。提交，Vasilakis等人。正在准备中)和Ae.埃及伊蚊，地方性登革热的主要媒介(Hanley等人。正在准备中)。 另一种解释是，与地方性登革热病毒株的竞争阻止了新冠病毒株的出现。因此，我们目前的研究集中在表征地方性和草原DENV毒株之间的竞争强度和对称性。这种竞争可能发生在宿主或媒介中，但更有可能发生在感染持续终身的媒介中。我们最近已经证明，当将DENV-2和DENV-4混合感染同时(共同感染)或以第一和第二血清型之间的指定间隔(重叠感染)引入培养的蚊子细胞时，每种血清型的复制都会减少，感染的总体生产力也会降低(Pepin等人)。在印刷中，Pepin和Hanley正在准备中)。此外，在重复感染处理中，对第二次感染的菌株的抑制作用最强。这些模式是竞争的标志。在这项拟议的研究中，将在蚊子体内测试DENV-2和DENV-4之间的竞争模式。随后，我们将使用相同的方法在体内测量一组演绎和地方性DENV-2分离株的竞争抑制。竞争性抑制将被测量为当一个特定的分离物与一个共同的DENV-4竞争对手共同感染时与它单独感染时所达到的滴度。我们将比较法式和地方性菌株的相对竞争抑制。如果与地方性DENV-4毒株相比，法氏菌对地方性DENV-4的竞争能力更差，这将支持竞争可能有助于将法氏菌排除在地方性流行循环之外的假说。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Dengue virus (genus Flavivirus) the most significant threat to public health among the arthropod-borne viruses, circulates in two distinct life cycles. Epidemic dengue viruses, which cause human dengue fever, cycle between humans and peridomestic Aedes mosquitoes. Sylvatic dengue viruses cycle in the forest canopies of Africa and Asia between sylvatic Aedes species and non-human primates. Endemic and sylvatic viruses show high sequence homology, but sylvatic viruses do not cause outbreaks in humans. Our initial hypothesis to explain this apparent paradox was that an "adaptive barrier" prevents the emergence of sylvatic dengue virus, or more specifically that sylvatic dengue virus replicates poorly in either humans or in peridomestic Aedes species. However, in collaboration with INBRE mentor Scott Weaver (UTMB) and members of his lab, we have demonstrated that no such adaptive barrier exists, because sylvatic and endemic strains of DENV serotype 2 (DENV-2) are equally infectious for models of virus replication in humans (Vasilakis et al. 2007, Vaslakis et al. submitted, Vasilakis et al. in preparation) and for Ae. aegypti, the primary vector of endemic dengue (Hanley et al. in preparation). An alternative explanation for the restriction of sylvatic dengue to the forest cycle is that competition with endemic strains of DENV prevents emergence of sylvatic strains. Thus, our current research focuses on characterizing the strength and symmetry of competition between endemic and sylvatic DENV strains. Such competition could occur in either the host or vector, but may be more likely in the vector where infection persists for life. We have recently demonstrated that when mixed infections of DENV-2 and DENV-4 are introduced to cultured mosquito cells concurrently (co-infection) or with a designated interval between the introduction of the first and second serotype (superinfection), the replication of each serotype is decreased, as is the overall productivity of the infection (Pepin et al. in press, Pepin and Hanley in preparation). Moreover suppression is strongest for strains that infect second in superinfection treatments. These patterns are the hallmarks of competition. In the proposed research, patterns of competition between DENV-2 and DENV-4 will be tested in mosquitoes in vivo. Subsequently, we will use the same methods to measure competitive suppression of a panel of sylvatic and endemic DENV-2 isolates in vivo. Competitive suppression will be measured as the titer achieved by a particular isolate when it is co-infected with a common DENV-4 competitor versus when it infects alone. The relative competitive suppression of sylvatic and endemic isolates will be compared. If sylvatic isolates are poorer competitors against endemic DENV-4 than other endemic isolates, this will support the hypothesis that competition may contribute to the exclusion of sylvatic DENV from the endemic cycle.