Role of viral fibroblast growth factor in pathogenesis

描述（由申请人提供）：病媒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，从昆虫病媒的中肠进入血腔中的其他器官。虽然不同的病原体可能设计了替代方法来到达其他组织，但所有病原体都面临着相同的障碍。我们建议表征昆虫病原体所使用的生长因子信号传导机制，该机制可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）是广泛存在于多细胞生物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，单个无分支的FGF调节气管细胞运动，决定其分支的模式。杆状病毒是一种含有大量DNA的病毒，与其他真核病毒相似，其编码的基因影响宿主的发育。大多数杆状病毒编码一个fgf同源物vfgf，具有与细胞同源物相似的生化特性，然而，vfgf在病毒感染过程中的作用尚不清楚。杆状病毒将感染传播到主要感染部位（中肠上皮细胞）以外的具体机制尚未详细定义，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性来全身传播感染。我们将在昆虫宿主中描述vfgf敲除杆状病毒的特征。具体而言，（1）vfgf敲除和vfgf过表达病毒的感染性和毒力将使用处于不同发育阶段的4种昆虫物种来确定;（2）我们将通过使用扫描共聚焦和透射电子显微镜检查vFGF对服务于中肠的气管细胞的运动性和形态学的影响来确定杆状病毒穿过中肠屏障的机制。我们希望我们的研究结果将有助于病原体-载体相互作用和发病机制的有价值的信息。许多以昆虫为媒介的病原体携带人类和动物疾病。病原体如何从昆虫中肠移动到其他组织使其传播的具体机制尚不清楚。拟议的研究将确定昆虫病原体通过其宿主传播的机制，开发研究其他昆虫病原体的工具，并从长远来看，导致控制人类病原体传播的新策略的发展。

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.