Role of viral fibroblast growth factor in pathogenesis

描述(申请人提供)：媒介生物学领域的一个长期存在的问题是，病原体如何绕过细胞和非细胞屏障以及宿主防御机制，从昆虫媒介的中肠进入血腔中的其他器官。尽管不同的病原体可能已经设计出了到达其他组织的替代方法，但所有的病原体都面临着相同的障碍。我们建议描述一种昆虫病原体使用的生长因子信号机制，该机制可以适用于疟疾寄生虫和媒介传播病毒等病原体。成纤维细胞生长因子(FGFs)是一个广泛存在于多细胞生物体中的多肽生长因子大家族，是细胞分化、细胞增殖和细胞运动的关键调节因子。在果蝇中，单一的成纤维细胞生长因子，无枝，调节气管细胞的运动，决定其分支的模式。杆状病毒是含有DNA的大型病毒，类似于其他真核病毒，编码影响宿主发育的基因。大多数杆状病毒编码成纤维细胞生长因子的同源物vfgf，具有与细胞同源物相似的生化特性，然而，vfgf在病毒感染中的作用尚不清楚。杆状病毒用于将感染传播到主要感染部位中肠上皮细胞之外的具体机制尚未详细确定，但气管细胞已被认为是病毒传播到中肠以外的管道。我们假设病毒利用vfgf刺激未感染的气管细胞的运动，从而系统地传播感染。我们将在昆虫宿主中鉴定一种vfgf敲除杆状病毒。具体地说，(1)将使用4种不同发育阶段的昆虫来确定vfgf基因敲除和vfgf过度表达病毒的感染力和毒力；以及(2)我们将通过扫描共聚焦和透射电子显微镜检测vFGF对服务于中肠的气管细胞的运动性和形态的影响，确定杆状病毒穿越中肠屏障的机制。我们期望我们的结果将有助于病原体-病媒相互作用和发病机制的有价值的信息。许多昆虫传播的病原体携带人类和动物疾病。病原体如何从昆虫中肠传播到使其传播的其他组织的具体机制尚不清楚。拟议中的研究将确定昆虫病原体通过其宿主的机制，开发研究其他昆虫病原体的工具，并从长远来看，导致开发控制人类病原体传播的新策略。

DESCRIPTION (provided by applicant): A long standing question in the field of vector biology is how pathogens gain access from the midgut of an insect vector to other organs in the hemocoel, bypassing cellular and non-cellular barriers as well as host defense mechanisms. Although different pathogens may have devised alternative methods to reach other tissues, all are faced with the same barriers. We propose to characterize a growth factor signaling mechanism used by an insect pathogen that can be applicable to pathogens such as malaria parasites and vector-borne viruses. Fibroblast growth factors (FGFs) are a large family of polypeptide growth factors widespread in multicellular organisms and are key regulators in cell differentiation, cell proliferation, and cell motility. In Drosophila, a single fgf, branchless, regulates tracheal cell motility, determining the pattern of its branches. Baculoviruses are large DNA-containing viruses that, similar to other eukaryotic viruses, encode genes that affect the development of their host. Most baculoviruses encode an fgf homolog, vfgf, with similar biochemical properties to the cellular homologs, however, the role of vfgf during virus infection is unknown. The specific mechanism used by baculoviruses to spread infection beyond the primary site of infection, midgut epithelial cells, has not been defined in detail, but tracheolar cells have been implicated as conduits for virus propagation beyond the midgut. We hypothesize that the virus utilizes vfgf to stimulate motility of uninfected tracheolar cells to spread infection systemically. We will characterize a vfgf-knockout baculovirus in insect hosts. Specifically, (1) the infectivity and virulence of vfgf- knockout and vfgf-overexpressing viruses will be determined using 4 insect species at different developmental stages; and (2) we will determine the mechanisms by which baculoviruses traverse the midgut barrier by examining the effect of vFGF on motility and morphology of tracheolar cells servicing the midgut using scanning confocal and transmission electron microscopy. We expect that our results will contribute valuable information to pathogen-vector interactions and pathogenesis. Many insect-vectored pathogens carry human and animal diseases. The specific mechanisms of how the pathogens travel from the insect midgut to the other tissues enabling their transmission are not known. The proposed studies will determine the mechanism used by an insect pathogen to move through its host, develop tools to study other insect pathogens, and in the long run, lead to the development of new strategies to control human pathogen transmission.