The Roles of Conserved outer-membrane proteins in SFG rickettsia pathogenesis

保守外膜蛋白在 SFG 立克次体发病机制中的作用

• 批准号: 7779402
• 负责人: Juan J Martinez
• 金额: $ 37.55万
• 依托单位: UNIVERSITY OF CHICAGO
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-02 至 2014-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7779402
• 关键词: Address; Adherence; Adhesions; Aerosols; Antibiotic Therapy; Arthropod Vectors; Bacteria; Bacterial Adhesins; Binding; Bioterrorism; Bite; Blood Vessels; Boutonneuse Fever; Brain; Cell Culture Techniques; Cell Line; Cells; Complex; Coupled; Development; Disease; Elements; Endothelial Cells; Endothelium; Escherichia coli; Family; Fever; Future; G22P1 gene; Gene Family; Generations; Genes; Genome; Goals; Gram-Negative Bacteria; Human; IL8 gene; Immune Sera; Immune response; Immunity; In Vitro; Infection; Infection Control; Inflammation; Inflammatory; Interleukin-6; Interstitial Pneumonia; Invaded; Knockout Mice; Latex Bead; Ligands; Lung; Mammalian Cell; Mediating; Membrane Proteins; Modeling; Molecular; Morbidity - disease rate; Mus; Open Reading Frames; Pathogenesis; Play; Process; Proteins; Pulmonary Edema; Receptor Cell; Recombinants; Recruitment Activity; Research; Rickettsia; Rickettsia Infections; Rickettsia conorii; Role; Signal Pathway; Site; Skin; Spottings; Surface Antigens; Therapeutic Studies; Ticks; United States; Virulence Factors; antimicrobial; congenic; cytokine; human tissue; in vivo; interest; member; mortality; novel; pathogen; programs; public health relevance; receptor; research study; transmission process; uptake

DESCRIPTION (provided by applicant): Rickettsia conorii, a member of the spotted fever group (SFG) rickettsia is an obligate intracellular tick borne pathogen and is the causative agent of Mediterranean spotted fever. Aerosol transmission of rickettsia can occur and therefore, represents a bioterrorist threat for the United States. The pathogenesis of R. conorii upon transmission into the host depends on the pathogen's ability to bind to and invade target host cells. Annotation of several sequenced rickettsial genomes has identified a large family of genes termed surface cell antigens (sca) that resemble autotransporter proteins and virulence factors in Gram-negative bacteria. While many genes in this family are degenerate or split, at least 4 genes, sca0 (rompA), sca1, sca2, and sca5 (rompB) are present as complete open reading frames in R. conorii and many other SFG rickettsia. Previous results have demonstrated that Sca0 (rOmpA) and Sca5 (rOmpB) are important for the adhesion to and subsequent invasion of non-phagocytic mammalian cells and in the generation of protective humoral immune responses. However, very little is known about the function of other outermembrane proteins in SFG rickettsia pathogenesis. We have identified the first rickettsial protein-host cell receptor pair (rOmpB-Ku70) that plays an important role in the establishment of a successful infection within target human cells. Interestingly, our results have also suggested that while rOmpB-Ku70 interactions are important during the invasion process, other conserved SFG rickettsia proteins, namely rOmpA, Sca1 and Sca2, likely play important roles during pathogenesis. The experiments outlined in this proposal will address the following research interests: i. The contributions of rOmpB and Ku70 to colonization will be analyzed by using recombinant E. coli, purified proteins and protein coupled latex beads. The induction of host signaling pathways involved in the uptake process will also be analyzed using a cell culture model. ii. We will determine the contribution of rOmpB and Ku70 to the initiation and progression of SFG rickettsial disease in a murine model of infection using wild-type and Ku70 knockout mice. iii. We will also determine the roles of conserved surface antigens, namely rOmpA, Sca1 and Sca2 in mediating invasion of non-phagocytic mammalian cells. The roles of these proteins in generating protective humoral immune responses will be examined in a murine model of infection. In addition, we will identify novel ligands that interact with these conserved surface proteins in the hopes of identifying new receptors that play roles in the pathogenesis of SFG rickettsia. PUBLIC HEALTH RELEVANCE: Rickettsia conorii, the causative agent of Mediterranean spotted fever, is transmitted by tick bite inoculation into the skin of the human host. Damage to target endothelial cells especially in the lungs and brain can result in the most severe manifestations of disease including pulmonary edema and interstitial pneumonia. Although infections are controlled by broad-spectrum antibiotic therapies, untreated or misdiagnosed Mediterranean spotted fever can results in severe morbidity and mortality. With the threat of the potential use of Rickettsiae and other bacteria as agents for biological terrorism, understanding the complex interplay between the pathogen and host cells is vital for the future development of novel anti-microbials and therapies.

描述（由申请人提供）：康氏立克次体，斑疹热群（SFG）的成员。立克次体是一种专性细胞内蜱传病原体，并且是地中海斑疹热的病原体。立克次体可以通过气溶胶传播，因此对美国构成生物恐怖威胁。康氏罗氏菌传播到宿主后的发病机制取决于病原体结合和侵入靶宿主细胞的能力。对几个立克次体基因组测序的注释已经鉴定出一个被称为表面细胞抗原（sca）的基因大家族，它们类似于革兰氏阴性细菌中的自转运蛋白和毒力因子。虽然该家族中的许多基因是简并或分裂的，但至少有 4 个基因 sca0 (rompA)、sca1、sca2 和 sca5 (rompB) 在 R. conorii 和许多其他 SFG 立克次体中作为完整的开放阅读框存在。先前的结果表明，Sca0 (rOmpA) 和 Sca5 (rOmpB) 对于非吞噬哺乳动物细胞的粘附和随后的侵袭以及保护性体液免疫反应的产生非常重要。然而，对于其他外膜蛋白在 SFG 立克次体发病机制中的功能知之甚少。我们已经鉴定出第一个立克次体蛋白-宿主细胞受体对 (rOmpB-Ku70)，它在人类目标细胞内成功感染的过程中发挥着重要作用。有趣的是，我们的结果还表明，虽然 rOmpB-Ku70 相互作用在入侵过程中很重要，但其他保守的 SFG 立克次体蛋白，即 rOmpA、Sca1 和 Sca2，可能在发病机制中发挥重要作用。本提案中概述的实验将解决以下研究兴趣：将使用重组大肠杆菌、纯化蛋白和蛋白偶联乳胶珠来分析 rOmpB 和 Ku70 对定植的贡献。还将使用细胞培养模型来分析参与摄取过程的宿主信号通路的诱导。二.我们将使用野生型和 Ku70 敲除小鼠，在感染小鼠模型中确定 rOmpB 和 Ku70 对 SFG 立克次体病的发生和进展的贡献。三.我们还将确定保守表面抗原，即 rOmpA、Sca1 和 Sca2 在介导非吞噬哺乳动物细胞侵袭中的作用。这些蛋白质在产生保护性体液免疫反应中的作用将在小鼠感染模型中进行检查。此外，我们将鉴定与这些保守表面蛋白相互作用的新配体，希望鉴定在 SFG 立克次体发病机制中发挥作用的新受体。公共卫生相关性：康氏立克次体是地中海斑疹热的病原体，通过蜱虫叮咬接种到人类宿主的皮肤中传播。对靶内皮细胞（尤其是肺和脑）的损伤可导致最严重的疾病表现，包括肺水肿和间质性肺炎。尽管感染可以通过广谱抗生素疗法控制，但未经治疗或误诊的地中海斑疹热可能导致严重的发病率和死亡率。由于立克次体和其他细菌可能被用作生物恐怖主义的媒介，了解病原体和宿主细胞之间复杂的相互作用对于未来开发新型抗微生物药物和疗法至关重要。