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

• 批准号: 8616334
• 负责人: Juan J Martinez
• 金额: $ 18.5万
• 依托单位: LOUISIANA STATE UNIV A&M COL BATON ROUGE
• 依托单位国家: 美国
• 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/8616334
• 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

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）：立克次氏体属的革兰氏阴性β-变形菌是小型（0.3-0.5 x 0.8-1.0μm）、专性细胞内生物体。它们分为两大类：斑疹热组（SFG）和斑疹伤寒组（TG），可以通过抗原性和基于细胞内肌动蛋白的运动来区分。该属成员导致严重的人类疾病，包括康氏立克次体和立氏立克次体在内的多个物种已被美国国家过敏和传染病研究所 (NIAID) 列为 B 类和 C 类优先病原体，并被美国疾病控制和预防中心 (CDC) 列为精选病原体 (立克次体)，因为它们有可能用作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，一种模型 SFG 立克次体物种，即地中海斑疹热 (MSF) 的病原体康氏立克次体 (R. conorii)，能够逃避人和鼠血清中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。我们已经鉴定出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的存活。我们已经证明 R. conorii 与人因子 H (fH)（替代补体途径的液相调节剂）相互作用，并且 rOmpB 与人 fH 共免疫沉淀，证明其作为真正的 fH 结合蛋白 (fHbp) 的能力。我们还证明，当在缺乏 fH 的人血清中孵育时，康氏立克次体的存活率会受到损害，这表明立克次体与血清成分的特异性相互作用对于存活至关重要。 rOmpB 和 RC1281 的同源物存在于所有致病性立克次体中，表明主动扰乱血液中补体介导的杀伤作用的能力是此类病原体的新毒力属性。本提案中概述的实验将解决以下研究兴趣： 我。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，并将确定逃避补体介导杀伤的潜在机制。 二.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。