Pneumolysin, Innate and Acquired Immunity to Pneumococci

肺炎链球菌仍然是世界范围内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性热反应的主要原因，一种是硫醇激活的分泌性毒素肺炎溶血素，另一种是细胞壁的肽聚糖成分。在体外研究中，这两种分子都被证明可以引起上皮细胞和神经细胞的炎症变化，以及激活非活跃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这样的假设，即肺炎溶血素通过跨膜受体Toll样受体4(TLR4)与肽聚糖(TLR2配体)和/或整个肺炎球菌协同激活免疫系统的固有手臂。此外，我们有一些初步数据表明，肺炎溶血素激活天然免疫反应也可以极大地增强对肺炎球菌的获得性免疫。该项目的科学目标分为两个阶段。在第一阶段，PI将单独以及与肽聚糖或整个肺炎球菌联合研究肺炎溶血素依赖TLR的信号通路。将进行研究，以检验肺炎毒素直接与TLR4结合的假设。这一阶段还将包括密集的教学部分，以补充实验室的工作。在第二阶段，PI将研究这一途径在疾病和肺炎球菌获得性免疫调节中的作用。该项目的这一阶段将检验TLR4介导的由肺炎溶血素激活的细胞在肺炎球菌疾病的病理生理学中发挥重要作用的假设。携带肺炎溶血素基因突变、TLR4信号传递能力减弱或丧失的肺炎球菌，将在体外(在巨噬细胞中)和体内(在小鼠的定植和疾病模型中)进行研究。TLR4介导的对肺炎溶血素的反应在获得性免疫发展中的可能作用将在该提案的最终目标中进行研究。在肺炎球菌免疫反应的先天和后天免疫反应之间建立联系可能有助于更好地理解获得肺炎球菌免疫的机制。

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.