Novel Therapeutic Target(s) for Pathogenic Rickettsia Species

 描述（由申请方提供）：由蜱传播的立克次体引起的落基山斑疹热（RMSF）是一种在美洲流行的严重传染病。R. conorii，地中海斑点热的病原体，与R.立克次氏体也可引起与显著发病率和死亡率相关的使人衰弱的感染。致病性立克次体优先靶向中小血管的微血管内皮，导致血管炎症和渗透性受损，统称为“立克次体血管炎”。立克次体作为专性胞内病原体，有效粘附和侵入宿主细胞，然后快速逃逸到营养丰富的细胞质小生境中，对于立克次体的生长、复制和传播至关重要。通过互补方法的组合，我们最近发现成纤维细胞生长因子受体1（FGFR 1）作为立克次体利用的受体之一，以获得进入宿主内皮细胞。来自我们正在进行的工作的进一步证据清楚地表明，FGFR 1的抑制降低了体外细胞内感染和体内肺立克次体负荷的水平。从机制上讲，两种宿主特异性microRNA（miR 424和miR 503）的负调控导致FGFR 1的表达增强，以促进宿主细胞与入侵立克次体之间的相互作用。本申请的总体目标是利用致病性立克次氏体与靶宿主细胞的这种关键的“初始”相互作用，其阻断防止进入和接近有利于其生长和复制的胞质内环境，用于开发新的治疗策略和鉴定用于早期诊断的潜在的新生物标志物。因此，我们建议研究宿主miR介导的FGF 2/FGFR 1表达调节在SF立克次体体外侵袭人类和小鼠微血管内皮中的作用和机制[目的1]。具体来说，我们将确定miR 424/miR 503模拟物和antagomir以及FGFR 1特异性抑制剂对FGF 2/FGFR 1表达和立克次体侵袭的影响，并阐明FGFR 1介导的侵入机制。接下来，我们将在已建立的小鼠模型中描述FGF 2/FGFR 1相互作用在RMSF发生和进展中的作用，并探索FGFR 1抑制剂和miR 424/503模拟物作为新型治疗药物以及循环miR作为疾病早期生物标志物的潜力[目的2]。实现这些目标的多学科方法不仅涉及生理学相关的人类和小鼠细胞培养系统，建立密切再现人类疾病的感染小鼠模型，以及细胞和分子转录组学的前沿应用，而且还将受益于小鼠中FGFR 1的内皮特异性破坏和立克次体学研究各方面的强大机构专业知识。这项提议与NIH的使命高度相关，因为它旨在发现新的靶点，以开发新的治疗方法，并确定新的工具，用于诊断困扰地球仪人类的严重和潜在致命的立克次体病。

 DESCRIPTION (provided by applicant): Rocky Mountain spotted fever (RMSF) due to tick-transmitted Rickettsia rickettsii is a serious infectious disease prevalent in the Americas. R. conorii, the etiologic agent of Mediterranean spotted fever phylogenetically related to R. rickettsii, can also cause debilitating human infections associated with significant morbidity and mortality. Pathogenic rickettsiae preferentially target microvascular endothelium of small- and medium-sized vessels resulting in vascular inflammation and compromised permeability, collectively termed as `rickettsial vasculitis'. As obligate intracellular pathogens, efficient adhesion and invasion into host cells followed by quick escape into nutrient-rich cytoplasmic niche is critical for rickettsial growth, replication, and dissemination. Through a combination of complementary approaches, we have recently discovered Fibroblast Growth Factor Receptor 1 (FGFR1) as one of the receptors utilized by rickettsiae to gain entry into host endothelial cells. Further evidence from our ongoing work clearly suggests that inhibition of FGFR1 diminishes the levels of intracellular infection in vitro and pulmonary rickettsial burden in vivo. Mechanistically, negative regulation of two host-specific microRNAs (miR424 and miR503) results in augmented expression of FGFR1 to facilitate interactions between the host cell and invading rickettsiae. The overall objective of this application is to exploit this critical `initia' interaction of pathogenic rickettsiae with the target host cells, the blocking of which prevents entry and access to intracytoplasmic environment conducive to their growth and replication, for the development of new therapeutic strategies and identification of potentially novel biomarkers for early diagnosis. Accordingly, we propose to investigate the contributions of and mechanisms underlying host miR-mediated regulation of FGF2/FGFR1 expression in the invasion of human and mouse microvascular endothelium by SF rickettsiae in vitro [Aim 1] . Specifically, we will determine the effects of miR424/miR503 mimics and antagomirs as well as FGFR1-specific inhibitors on FGF2/FGFR1 expression and rickettsial invasion and elucidate the mechanisms underlying FGFR1-mediated entry. We will next delineate the contributions of FGF2/FGFR1 interactions in the initiation and progression of RMSF in established mouse models and explore the potential for FGFR1 inhibitors and miR424/503 mimics as novel therapeutics and circulating miRs as early biomarkers of disease [Aim 2] . The multi-disciplinary approaches to accomplish these aims will not only involve physiologically relevant human and murine cell culture systems, established mouse models of infection closely recapitulating human disease, and cutting-edge applications of cellular and molecular transcriptomics, but will also benefit from endothelial-specific disruption of FGFR1 in mice and strong institutional expertise in all aspects of Rickettsiology research. This proposal is highly relevant to the mission of the NIH, as it aims to uncover novel targets to develop new therapeutics and identify new tools for the diagnosis of severe and potentially fatal rickettsioses afflicting human-kind across the globe.