Mechanisms of Immunity to Pneumococcal Colonization

描述（由申请人提供）：该资助的总体主题是了解被包裹的细胞外细菌肺炎链球菌（肺炎球菌）定植的获得性免疫机制，每年有超过80万人死于败血症和肺炎。历史上，对荚膜多糖的抗体传统上被认为是免疫的主要机制。然而，在初步实验中，我们发现在缺乏抗体的情况下，肺炎球菌的定植可以被阻止，并且通过杀死的肺炎球菌鼻内免疫保护抗体缺陷但T细胞缺陷的小鼠，或先天CD4+ T细胞缺陷或在挑战时这些细胞耗尽的小鼠。相比之下，先天缺乏CD8+ T细胞或CD8+ T细胞缺失的小鼠完全受到保护。从免疫小鼠中过继转移CD4+细胞可保护rag缺陷小鼠免受随后的肺炎球菌定植。ifn - γ缺陷小鼠受WCV保护；而IL-17A受体缺陷小鼠则没有。结合三种肺炎球菌蛋白进行鼻内免疫，可获得不依赖抗体的肺炎球菌定植免疫。因此，我们的数据表明，对肺炎球菌定植的免疫可以在没有抗体的情况下被诱导，并且需要在攻击时存在获得性的、抗原特异性的产生il - 17a的CD4+ T细胞。本研究的目的是验证一种假设，即在先天免疫反应的初始影响下，这些特异性IL-17A T细胞介导的反应在获得性肺炎球菌定植抗性中起关键作用。该项目的总体目标是研究细胞免疫应答保护机体免受肺炎球菌定植和/或疾病侵袭的机制，并确定toll样受体（TLRs）的参与是否决定了这些T细胞应答的发展。实验方法将包括T细胞过继转移实验、Th反应的极化、细胞因子和TLR缺陷小鼠的免疫接种，以及使用定义的肺炎球菌成分作为免疫原和TLR激动剂。我们的实验结果将确定一种以前未被认识到的保护细胞外包裹细菌的机制，并有助于开发新型肺炎球菌疫苗。

DESCRIPTION (provided by applicant): The overall theme of this grant is to understand mechanisms of acquired immunity to colonization by the encapsulated, extracellular bacterium Streptococcus pneumonias (pneumococcus), the cause of over 800,000 deaths from sepsis and pneumonia annually. Historically, antibody to the capsular polysaccharides has traditionally been viewed as the primary mechanism of immunity. In preliminary experiments, we found however that colonization with pneumococci could be prevented in the absence of antibody and that intranasal immunization by killed pneumococci protected antibody-deficient but not T-cell deficient mice, or mice that were congenitally deficient in CD4+ T cells or depleted of these cells at the time of challenge. In contrast, mice congenitally deficient in, or depleted of CD8+ T cells were fully protected. Adoptive transfer of CD4+ cells from immunized mice protected RAG-deficient mice from subsequent pneumococcal colonization. IFN-gamma deficient mice were protected by WCV; however, IL-17A receptor-deficient mice were not. Intranasal immunization with a combination of three pneumococcal proteins conferred antibody- independent immunity to pneumococcal colonization. Thus, our data suggest that immunity to pneumococcal colonization can be induced in the absence of antibody and requires the presence of acquired, antigen-specific IL-17A-producing CD4+ T cells at the time of challenge. The purpose of this proposal is to test the hypothesis that, under the initial influence of innate immune responses, these specific IL-17A T cell-mediated responses play a critical role in acquired resistance to pneumococcal colonization. The overall goals of this project are to study the mechanisms whereby cellular immune responses protect against pneumococcal colonization and/or disease and determine whether engagement of toll-like receptors (TLRs) determines the development of these T cell responses. Experimental approaches will include T cell adoptive transfer experiments, polarization of Th responses, immunization of cytokine- and TLR-deficient mice, and use of defined pneumococcal components as immunogens and TLR agonists. The results of our experiments will define a previously-unrecognized mechanism of protection against extracellular encapsulated bacteria and help in the development of novel vaccines against pneumococcus.