Pneumolysin, Innate and Acquired Immunity to Pneumococci

肺炎链球菌仍然是全世界发病率和死亡率的主要原因。肺炎球菌的两种成分被认为是造成有害炎症热反应的主要原因，即硫醇激活的分泌毒素溶气酶和细胞壁的肽聚糖成分。在体外研究中，这两种分子都被证明能引起上皮细胞和神经细胞的炎症变化，并激活失活免疫系统的单核细胞和巨噬细胞。我们实验室的初步工作支持溶肺素通过跨膜受体toll样受体4 （TLR4）与肽聚糖（TLR2配体）和/或整个肺炎球菌协同作用激活免疫系统固有臂的假设。此外，我们有一些初步的数据表明，溶肺素激活先天免疫反应也可能大大增强对肺炎球菌的获得性免疫。本项目的科学目标分为两个阶段。在第一阶段，PI将研究溶肺素TLR依赖的信号通路，单独或与肽聚糖或整个肺炎球菌联合使用。将进行研究以验证溶血素直接与TLR4结合的假设。这一阶段还将包括一个密集的教学成分，以补充在实验室的工作。在第二阶段，该项目将研究该途径在调节疾病和获得性肺炎球菌免疫中的作用。这一阶段的项目将验证tlr4介导的溶肺素细胞活化在肺炎球菌疾病的病理生理中起重要作用的假设。携带溶肺素基因突变的肺炎球菌，其tlr4信号能力减弱或消失，将在体外（巨噬细胞）和体内（定植和疾病的小鼠模型）进行研究。tlr4介导的溶血素应答在获得性免疫发展中的可能作用将在提案的最终目的中进行研究。对肺炎球菌免疫反应的先天臂和获得臂之间的联系的建立可以更好地理解肺炎球菌获得性免疫的机制。

Streptococcus pneumoniae remains a major cause of morbidity and mortality worldwide. Two components of pneumococci are thought to be responsible for much of the deleterious inflammatory hot response, the thiol-activated secreted toxin pneumolysin and the peptidoglycan component of the ell wall. Both of these molecules have been shown to cause inflammatory changes in vitro studies in epithelial and neuronal cells, as well as activate monocytes and macrophages of the inactive immune system. Preliminary work in our laboratory supports the hypothesis that pneumolysin activates the innate arm of the immune system through a transmembrane receptor, Toll-like receptor 4 (TLR4), in synergy with peptidoglycan (a TLR2 ligand) and/or whole pneumococci. In addition, we have some preliminary data to suggest that the activation of the innate immune response by pneumolysin may greatly augment acquired immunity to pneumococcus as well. The scientific goals of this project are divided in two phases. In the first phase, the PI will study the TLR- dependent signaling pathway of pneumolysin, alone and in combination with peptidoglycan or whole pneumococci. Studies will be done to test the hypothesis that pneumolysin binds directly to TLR4. This phase will also include an intense didactic component, to complement the work in the laboratory. In the second phase, the PI will study the role of this pathway in the modulation of disease and acquired immunity to pneumococci. This phase of the project will test the hypothesis that TLR4-mediated cellular activation by pneumolysin plays an important role in the pathophysiology of pneumococcal disease. Pneumococci carrying mutations in the pneumolysin gene, with diminished or abrogated TLR4-signaling capability, will be studied both in vitro (in macrophages) and in vivo (in murine models of colonization and disease). The possible role of TLR4-mediated response to pneumolysin in the development of acquired immunity will be studied in the final aim of the proposal. The establishment of a link between the innate and the acquired arm of the immune response to pneumococcus may provide a better understanding of the mechanisms by which immunity to pneumococcus is acquired.