Evasion of complement-mediated killing by pathogenic rickettsial species

致病性立克次体物种逃避补体介导的杀伤

基本信息

批准号：
8430190
负责人：
Juan J Martinez
金额：
$ 22.2万
依托单位：
LOUISIANA STATE UNIV A&M COL BATON ROUGE
依托单位国家：
美国
项目类别：
财政年份：
2013
资助国家：
美国
起止时间：
2013-02-15 至 2015-01-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8430190
关键词：
Actins Address Adhesions Alternative Complement Pathway Antibiotic Therapy Antibodies Antigens Arthropod Vectors Arthropods Bacteremia Bacteria Bacterial Adhesins Binding Binding Proteins Bioinformatics Bioterrorism Bite Blood Blood Circulation Blood Vessels Boutonneuse Fever Brain Categories Cells Centers for Disease Control and Prevention (U.S.)Complement Complement Factor H Complex Deposition Development Disease Disease Progression Endothelial Cells Endothelium Equilibrium Escherichia coli Family Fever Future Gene Family Genes Genome Goals Gram-Negative Bacteria Hematogenous Homologous Gene Human Human Factor H Immune system In Vitro Incubated Infection Infection Control Interstitial Pneumonia Invaded Investigation Liquid substance Lung Mammalian Cell Mammals Mediating Membrane Modeling Molecular Molecular Analysis Morbidity - disease rate Mus Mutagenesis National Institute of Allergy and Infectious Disease Open Reading Frames Organ Organism Pathogenesis Phase Plasma Proteins Proteobacteria Pulmonary Edema Research Resistance Rickettsia Rickettsia Infections Rickettsia conorii Rickettsia rickettsii Rocky Mountain Spotted Fever Role Serum Serum Proteins Skin Spottings Surface Antigens System Ticks Tissues Typhus Virulence Yersinia bacterial resistance bactericide base cell motility defined contribution disorder prevention human disease human tissue in vivo in vivo Model interest killings member mortality mutant neutralizing antibody novel pathogen programs public health relevance research study resistance factors tool transmission process

项目摘要

DESCRIPTION (provided by applicant): The Gram-negative ¿-proteobacteria of the genus Rickettsia are small (0.3-0.5 x 0.8-1.0 ?m), obligate intracellular organisms. They are categorized into two major groups, the Spotted Fever Group (SFG) and Typhus Group (TG), which can be distinguished by antigenicity and intracellular actin-based motility. Members of this genus are responsible for severe human diseases and several species including R. conorii and R. rickettsii, have been classified as Category B and C Priority Pathogens by the National Institute of Allergy and Infectious Diseases (NIAID) and as the Select Agents (R. rickettsii) by the Centers for Disease Control and Prevention (CDC) for their potential use as tools for biological terrorism. We have recently determined that in the absence of neutralizing antibodies, a model SFG rickettsial species, R. conorii the etiologic agent of Mediterranean spotted fever (MSF), is able to evade complement-mediated killing in human and murine serum. These results suggested that R. conorii and possibly other rickettsial species likely have evolved active mechanisms to evade the bactericidal effects of complement deposition as the pathogen disseminates in the bloodstream to target organs and tissues. We have identified two highly conserved rickettsial antigens, rOmpB/Sca5 and RC1281/Adr1, which are sufficient to mediate survival in ex-vivo human serum models of rickettsia bacteremia. We have demonstrated that R. conorii interact with human Factor H (fH), a fluid phase regulator of the alternative complement pathway and that rOmpB co-immunopreciptates with human fH, demonstrating its ability to serve as a bona fide fH binding protein (fHbp). We have also demonstrated that R. conorii survival is compromised when incubated in human serum depleted of fH suggesting that specific rickettsial interactions with serum components are critical to survival. Homologues to rOmpB and RC1281 exist in all pathogenic rickettsiae suggesting that the ability to actively perturb complement-mediated killing in the blood is a novel virulence attribute for this class of pathogens. The experiments outlined in this proposal will address the following research interests: i. The contribution of rickettsial fH binding proteins to serum resistance will be analyzed in vitr using surrogate expression systems in E. coli. We will initially determine the significance of rOmpB and RC1281 to serum resistance in vitro and will also determine the mechanisms underlying the evasion of complement-mediated killing. ii. The contribution of generated targeted insertion mutants in rompB/sca5 and rc1281 will be analyzed using in vitro and in vivo models of R. conorii and R. rickettsii infection.

描述（由申请人提供）：革兰氏阴性菌 ¿ -立克次氏体属的变形菌是小型（0.3-0.5 x 0.8-1.0 µm）的专性细胞内生物，它们分为两大类：斑点热菌群（SFG）和斑疹伤寒菌群（TG），可以区分。该属的成员通过抗原性和基于细胞内肌动蛋白的运动而导致严重的人类疾病，包括 R. conorii 和 R. conorii 在内的一些物种。立克次体已被国家过敏和传染病研究所 (NIAID) 分类为 B 类和 C 类优先病原体，并被疾病控制和预防中心 (CDC) 分类为精选病原体 (立克次体)，因为其潜在用途生物恐怖主义的工具。我们最近确定，在没有中和抗体的情况下，一种 SFG 立克次体模型，即地中海斑疹热 (MSF) 的病原体康氏立克次体 (R. conorii)，能够在人和小鼠血清中逃避补体介导的杀伤作用。这些结果表明：当病原体在血流中传播到目标器官和组织时，康氏立克次体和可能的其他立克次体物种可能已经进化出主动机制来逃避补体沉积的杀菌作用。鉴定了两种高度保守的立克次体抗原，rOmpB/Sca5 和 RC1281/Adr1，它们足以介导立克次体菌血症离体人血清模型中的存活。我们已经证明康氏立克次体与人因子 H (fH)（一种液体）相互作用。替代补体途径的相位调节剂，并且 rOmpB 与人 fH 共免疫沉淀，证明其作为真正的 fH 的能力我们还证明，当在缺乏 fH 的人血清中培养时，立克次体的存活率会受到影响，这表明立克次体与血清成分的相互作用对于所有致病性立克次体中存在的 rOmpB 和 RC1281 同源物至关重要。主动扰乱血液中补体介导的杀伤能力是此类病原体的一种新的毒力属性。本提案中概述的实验将解决以下研究兴趣： i. 将使用大肠杆菌中的替代表达系统在体外分析立克次体 fH 结合蛋白对血清抗性的贡献。我们将首先确定 rOmpB 和 RC1281 对体外血清抗性的重要性，并将确定逃避的机制。补体介导的杀伤。 ii.将使用R. conorii 和R. rickettsii 感染的体外和体内模型来分析rompB/sca5 和rc1281 中生成的靶向插入突变体的贡献。