GAS Switch from Colonizing Bacterium to Invasive Pathogen

GAS 从定植细菌转变为侵袭性病原体

• 批准号: 9232048
• 负责人: Victor Nizet
• 金额: $ 36.4万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2020-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9232048
• 关键词: Active Immunization; Adherence; Adopted; Alpha Cell; Animals; Antibodies; Antibody titer measurement; Antigens; Attention; Attenuated; Autophagocytosis; Bacteria; Biogenesis; Biological Assay; Blood Circulation; Carbohydrates; Cations; Cell Communication; Cell Wall; Complement; Conjugate Vaccines; Coupled; Developing Countries; Development; Disease; Disease model; Epithelial; Epithelial Cells; Epitopes; Funding; Genes; Genetic; Grant; Host Defense; Human; Immune; Immune Evasion; Immune Sera; Immunologics; In Vitro; Individual; Infection; Infectious Skin Diseases; Inflammatory; Inflammatory Response; Innate Immune System; Integration Host Factors; Investigation; Knockout Mice; Knowledge; Life; Lymphoid Tissue; Mediating; Microbial Biofilms; Modeling; Molecular; Molecular Genetics; Morbidity - disease rate; Mus; Natural Immunity; Necrotizing fasciitis; Nose; Outcome; Passive Immunization; Pathogenesis; Peptides; Phagocytes; Phagocytosis; Play; Prevention strategy; Proteins; Regimen; Regulation; Research; Resistance; Rheumatic Fever; Rheumatic Heart Disease; Role; Safety; Septicemia; Serotyping; Serum; Side; Skin; Source; Streptococcal Infections; Streptococcus pyogenes; Structure; System; Systemic infection; Time; Tissue Model; Toxic Shock Syndrome; Vaccination; Vaccine Antigen; Vaccines; Vertebral column; Virulence; Virulence Factors; Virulent; Vitronectin; Work; antimicrobial peptide; base; cross reactivity; human disease; human tissue; immune clearance; immune resistance; in vivo; in vivo Model; insight; killings; leukocyte activation; macrophage; mortality; mouse model; mutant; neutrophil; novel; novel therapeutics; pathogen; pressure; programs; public health relevance; response; success; tissue culture

 DESCRIPTION (provided by applicant): Group A Streptococcus (GAS) is a preeminent pathogen causing a wide spectrum of human diseases. The propensity of particular GAS strains to produce systemic infection defines its capacity to resist host innate immune clearance mechanisms. A clone of the GAS M1T1 serotype spread globally over the last 40 years as the leading cause of invasive infections. Our lab adopted a multifaceted approach to understanding GAS and host factors explaining diverse outcomes of this host-pathogen interaction, using invasive M1T1 GAS clone as a primary model. Our approach coupled precise, targeted of candidate virulence factor genes with in vitro, ex vivo and in vivo models of disease pathogenesis, including WT and knockout mouse lines. We hypothesized that the outcome of GAS infection is dictated by the action and regulation of these GAS virulence factors in response to selective pressures exerted by host innate immunity. In the first funding period, we examined more than two dozen individual virulence factors of the GAS M1T1 clone and their extra- and intracellular interaction with host neutrophils and macrophages, epithelial and endothelial barriers, and soluble immune effectors including antimicrobial peptides, complement proteins and antibodies. For this first renewal application, a key (originally unanticipated) discovery of the past year serves as the central focus for new investigation: our identification of the long-sought-after molecular genetic basis of the hallmark, species-defining, Lancefield group A cell wall carbohydrate antigen (GAC). Our genetic knowledge allowed us to generate the first, precise isogenic GAS M1T1 mutant lacking the Lancefield epitope, a GlcNAc side chain that extends from the polyrhamnose backbone of the antigen. Previously thought only to play a structural role in cell wall biogenesis, we demonstrated that the GlcNAc side-chain contributes to GAS disease pathogenesis by promoting GAS resistance to cationic defense peptides, serum and neutrophil killing, and a mutant lacking the GlcNAC side chain was markedly attenuated for virulence in vivo. The GlcNAc side-chain of GAC has been implicated in the immunopathogenesis of rheumatic heart disease, and we now have a genetic strategy for its elimination. Here we pursue a comprehensive analysis of the GAC GlcNAc side-chain in colonization and systemic virulence of GAS from different disease-associated serotypes, informed by the enhanced mechanistic understanding provided by studies of the original funding period. We will examine the role of the GAC GlcNAc side chain in GAS epithelial cell adherence and invasion, biofilm formation, intracellular survival, interaction with the autophagy system, resistance to macrophage killing, and modulation of leukocyte activation. In vivo, we will assess its role in GAS colonization, necrotizing skin infection and septicemia. Efficacy and safety of GlcNAc- deficient GAC as a universal vaccine antigen will be examined upon conjugation with three different proteins using an active immunization regimen in three different mouse models of GAS disease, with attention to antibody titers, promotion of opsono-phagocytosis and elimination of human tissue cross-reactivity.

 描述（由申请人提供）：A 族链球菌 (GAS) 是一种引起多种人类疾病的重要病原体。特定 GAS 菌株产生全身感染的倾向决定了其抵抗宿主先天免疫清除机制的能力。 GAS M1T1 血清型在过去 40 年中作为侵袭性感染的主要原因在全球范围内传播，我们的实验室采用了多方面的方法来了解 GAS 和宿主因素，解释了这种情况的不同结果。宿主-病原体相互作用，使用侵入性 M1T1 GAS 克隆作为主要模型，将候选毒力因子基因的精确靶向与体外、离体和体内疾病发病机制模型（包括 WT 和敲除小鼠系）结合起来。 GAS 感染的结果取决于这些 GAS 毒力因子对宿主先天免疫施加的选择性压力的反应和调节。在第一个资助期间，我们检查了二十多个单独的毒力因子。 GAS M1T1 克隆及其与宿主中性粒细胞和巨噬细胞、上皮和内皮屏障以及可溶性免疫效应物（包括抗菌肽、补体蛋白和抗体）的细胞外和细胞内相互作用。过去的一年是新调查的焦点：我们确定了 长久以来寻求的标志性物种定义性兰斯菲尔德 A 组细胞壁碳水化合物抗原 (GAC) 的分子遗传学基础我们的遗传知识使我们能够生成第一个精确的等基因 GAS M1T1 突变体，该突变体缺乏兰斯菲尔德表位（一种 GlcNAc）。从抗原的多鼠李糖骨架延伸的侧链以前被认为仅在细胞壁生物发生中发挥结构作用，我们证明 GlcNAc 侧链有助于 GAS 疾病。 GAC 的 GlcNAc 侧链与风湿性心脏病的免疫发病机制有关。我们现在有一个消除它的遗传策略，在这里我们对 GAS 的定植和系统毒力中的 GAC GlcNAc 侧链进行全面分析。我们将研究 GAC GlcNAc 侧链在 GAS 上皮细胞粘附和侵袭、生物膜形成、细胞内存活、与细胞相互作用中的作用。在体内，我们将评估其在 GAS 定植、坏死性皮肤感染和败血症中的作用。缺乏 GlcNAc 的 GAC 作为通用疫苗抗原的安全性将在三种不同的 GAS 疾病小鼠模型中使用主动免疫方案与三种不同的蛋白质缀合后进行检查，重点关注滴度、调理吞噬作用的促进和人体组织的消除交叉反应。