Virulence mechanisms of group A streptococcal toxins

A组链球菌毒素的毒力机制

• 批准号: 8900538
• 负责人: MICHAEL R WESSELS
• 金额: $ 43.96万
• 依托单位: BOSTON CHILDREN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8900538
• 关键词: Absenteeism; Accounting; Acute; Animal Model; Antibiotics; Autoimmune Process; Bacteremia; Bacteria; Binding; Biological; Biological Models; Cells; Cellular biology; Cessation of life; Child; Cholesterol; Chronic; Clinical; Cytolysins; Cytosol; Development; Disease; Eating; Epithelial Cells; Epithelium; Equus caballus; Family; Funding; Gene Expression; Goals; Gram-Positive Bacteria; Health; Heart Diseases; Host Defense; Human; Indium; Induction of Apoptosis; Infection; Infectious Skin Diseases; Investigation; Life; Mediating; Membrane; Messenger RNA; Molecular; Morbidity - disease rate; NAD+ Nucleosidase; Necrotizing fasciitis; Organism; Oropharyngeal; Pathogenesis; Penicillins; Phagocytes; Pharyngeal structure; Pharyngitis; Play; Predisposition; Prevention; Process; Production; Property; Proteins; Public Health; Recurrence; Relapse; Research; Resistance; Rheumatic Fever; Rheumatic Heart Disease; Role; Schools; Signal Transduction; Site; Streptococcal Infections; Streptococcus pyogenes; Syndrome; System; Testing; Toxic Shock Syndrome; Toxin; Treatment Failure; United States; Vaccines; Virulence; Work; anthrax toxin; antimicrobial peptide LL-37; base; cell type; cytotoxicity; extracellular; insight; keratinocyte; killings; macrophage; member; novel; novel strategies; pathogen; perforin; prevent; protein protein interaction; research study; streptolysin O; therapy development; trafficking; vaccine development; vector

DESCRIPTION (provided by applicant): Group A Streptococcus (S. pyogenes or GAS) is responsible for millions of cases of pharyngitis and skin infections each year in the United States with attendant morbidity and absenteeism from school and work. The organism also causes approximately 10,000 cases annually of invasive infections in the U.S., including bacteremia, necrotizing fasciitis, and streptococcal toxic shock. Globally, GAS infections and complications of the postinfectious syndrome of acute rheumatic fever account for an estimated 500,000 deaths per year. No vaccine is yet available, and treatment failures, relapses, and recurrences of infection remain common. With rare exceptions, clinical isolates of GAS produce the pore-forming hemolytic toxin streptolysin O (SLO). SLO is a member of the cholesterol-dependent cytolysins, a family of secreted proteins produced by many Gram- positive bacteria that share the property of binding to cholesterol-containing membranes where they oligomerize and insert to form large pores. Experimental infection studies have demonstrated a modest contribution of SLO to GAS virulence; however, animal models are not necessarily sensitive to factors that influence colonization in the human host. Colonization of the human oropharynx is central to GAS infection, and our recent results implicate SLO in this process through its ability to enhance GAS intracellular survival in oropharyngeal keratinocytes. SLO-mediated pore-formation and the capacity of SLO to deliver the co-toxin NAD-glycohydrolase to the cytosol of infected cells result in prolonged GAS survival. If these toxins are critical contributors to GAS adaptation for survival in the human host, they are important potential targets for pharmacologic intervention and vaccine development. Accordingly, Aim 1 of the project is to investigate how SLO and NADase promote resistance to killing by oropharyngeal epithelial cells as a potential mechanism for GAS persistence in the pharynx. We will determine how NADase increases expression or stability of SLO at both the transcriptional level and through protein-protein interactions. We will use anthrax toxin-based delivery of NADase as a novel means to dissociate the cellular effects of NADase from those of SLO, which is normally required for NADase translocation into host cells. This model system will permit direct study of how NADase subverts endosomal and autophagic maturation and promotes GAS survival in infected keratinocytes. Aim 2 will pursue the association of NADase production with the emergence of invasive GAS disease over the past 3 decades. If NADase-producing GAS can survive in macrophages, these cells may serve as a Trojan horse to initiate or extend invasive infection. To investigate this hypothesis, we will determine whether SLO and NADase mediate GAS resistance to killing by human macrophages, how NADase is delivered to these cells, and how SLO and NADase modify intracellular trafficking of GAS in macrophages. Understanding how SLO and NADase enhance GAS colonization of the human host and promote invasive infection will inform novel strategies to treat and prevent GAS infection.

描述（由申请人提供）：A组链球菌（S.化脓性链球菌或GAS）是美国每年数百万咽炎和皮肤感染病例的原因，伴随着发病率和缺课和工作。在美国，这种微生物每年还导致大约10,000例侵入性感染，包括菌血症、坏死性筋膜炎和链球菌中毒性休克。在全球范围内，GAS感染和急性风湿热感染后综合征的并发症估计每年造成50万人死亡。目前还没有疫苗可用，治疗失败，复发和感染复发仍然很常见。除了极少数例外，临床分离的GAS产生成孔溶血毒素链球菌溶血素O（SLO）。SLO是胆固醇依赖性溶细胞素的成员，所述溶细胞素是由许多革兰氏阳性细菌产生的分泌蛋白家族，其具有结合含胆固醇的膜的性质，在所述膜中它们寡聚化并插入以形成大孔。实验感染研究已经证明SLO对GAS毒力的贡献不大;然而，动物模型不一定对影响人类宿主中定植的因素敏感。人口咽部的定殖是GAS感染的核心，我们最近的研究结果表明SLO通过其增强口咽部角质形成细胞中GAS细胞内存活的能力参与了这一过程。SLO介导的孔形成和SLO将辅毒素NAD-糖水解酶递送至感染细胞的胞质溶胶的能力导致GAS存活延长。如果这些毒素是GAS适应人类宿主生存的关键因素，那么它们是药理学干预和疫苗开发的重要潜在靶点。因此，该项目的目的1是研究SLO和NADase如何促进对口咽上皮细胞杀伤的抗性，作为咽部GAS持续存在的潜在机制。我们将确定NADase如何在转录水平和通过蛋白质-蛋白质相互作用增加SLO的表达或稳定性。我们将使用基于炭疽毒素的NADase递送作为将NADase的细胞效应与SLO的细胞效应分离的新手段，SLO通常是NADase易位到宿主细胞中所需的。该模型系统将允许直接研究NAD酶如何破坏内体和自噬成熟并促进感染的角质形成细胞中的GAS存活。目标2将追踪过去30年来NADase产生与侵袭性GAS疾病出现之间的关系。如果产生NAD酶的GAS可以在巨噬细胞中存活，这些细胞可能作为特洛伊木马启动或延长侵入性感染。为了研究这一假设，我们将确定SLO和NADase是否介导GAS对人巨噬细胞杀伤的抗性，NADase如何被递送到这些细胞，以及SLO和NADase如何修饰巨噬细胞中GAS的细胞内运输。了解SLO和NADase如何增强GAS在人类宿主中的定植并促进侵袭性感染，将为治疗和预防GAS感染提供新的策略。