Control of protective immunity by innate pathways sensing bacterial viability

描述(由申请人提供)：长期以来，人们都知道减毒活疫苗可以诱导卓越的免疫保护和持久的免疫记忆，并且在大多数情况下是单剂接种。与死亡的疫苗相比，活疫苗诱导了不同的、更有力的免疫反应，触发了一种死亡微生物不必要的警报模式。但是，尽管活疫苗有效，但有几个因素导致它们不受欢迎。其中最主要的是对其安全性的担忧，以及在交付和保存方面的困难和增加的成本，特别是在发展中国家的贫困地区。了解活疫苗效力的分子基础将缓解这些担忧，并提供一种针对诱导最佳保护性免疫的相关途径的手段。我们在这里提出的工作将显著提高我们对减毒活疫苗优越疗效背后的基本免疫机制的理解。我们开始工作的假设是，先天性免疫细胞感知微生物传染性的最基本特征，微生物本身的生存能力，并激活一种为根除感染威胁而量身定做的免疫反应，重要的是，无论是否存在调节微生物毒力的专门因素。我们确定了标志性分子原核生物信使RNA，它提醒先天性免疫系统的专业吞噬细胞注意无菌组织中存在活微生物。我们确定了由细菌生存能力的识别所触发的离散的先天免疫反应。我们剖析了介导这些反应的先天免疫途径，并确定了协调这些反应的关键Toll样受体信号适配器的身份。我们的目标是确定细菌活性触发的警报模式如何影响随后的获得性免疫反应。随着对活性感受通路的识别和细菌mRNA的免疫刺激特性的掌握，我们将确定这些通路中的单个参与者在免疫反应进化中的作用。与以前使用佐剂和半抗原蛋白的研究不同，我们将专注于细菌感染背景下的抗原。我们将研究T细胞和B细胞免疫反应，首先从了解CD4T细胞反应的性质开始，因为它与T细胞依赖的抗体反应有关键联系。接下来，我们将剖析活细菌和死亡细菌表达的T细胞依赖和T细胞非依赖抗原的抗体反应。我们将定义感知细菌生存能力的途径的缺陷如何改变免疫反应，剥夺它对长期保护性免疫至关重要的因素。我们的研究很有可能揭示活疫苗诱导的卓越保护背后的机制，并创造新的佐剂和免疫策略，将活疫苗的有效性与死亡疫苗的安全性结合起来。

DESCRIPTION (provided by applicant): Live attenuated vaccines are long known to induce superior immune protection and lasting immune memory, and with single dose administration in most cases. When compared to their dead counterparts, live vaccines induce a distinct and far more vigorous immune response, triggering an alert mode not warranted for dead microorganisms. But despite the efficacy of live vaccines, several factors have contributed to their lack of popularity. Chief among these are concerns over their safety as well as difficulty and increased cost in their delivery and preservation especially to impoverished areas in developing countries. Understanding the molecular basis for the efficacy of live vaccines would alleviate these concerns, and provide a means to target the relevant pathways that induce optimal protective immunity. The work we propose here is poised to significantly enhance our understanding of the basic immune mechanisms behind the superior efficacy of live attenuated vaccines. We began our work with the hypothesis that innate immune cells sense the most fundamental characteristic of microbial infectivity, microbial viability itself, and activate an immune response tailored to eradicate the infectious threat, and importantly regardless of the presence of specialized factors that regulate microbial virulence. We identified the signature molecule, prokaryotic messenger RNA, which alerts professional phagocytic cells of the innate immune system to the presence of viable microbes in sterile tissues. We identified discrete innate immune responses triggered by the recognition of bacterial viability. We have dissected the innate immune pathways mediating these responses, and determined the identity of the critical Toll-like receptor signaling adaptor that orchestrates these responses. Our goal here is t identify how the alert mode triggered by bacterial viability impacts the subsequent adaptive immune response. With identity of the viability-sensing pathways and the immunostimulatory properties of the bacterial mRNA in hand, we will determine the role of individual players within these pathways in the evolution of the immune response. Unlike previous studies that have used adjuvants and haptenated proteins, we will focus on antigens presented within the context of a bacterial infection. We will investigate both the T cell and B cell immune response beginning first with understanding the nature of the CD4 T cell response because of its critical link to the T cell-dependent antibody response. We will next dissect the antibody response to both T cell-dependent and T cell-independent antigens expressed by both live and dead bacteria. We will define how deficiency in the pathways sensing bacterial viability alters the immune response, depriving it of the factors critical for long lasting protective immunity. Our studies have the high potential to reveal the mechanisms behind the superior protection induced by live vaccines, and to create new adjuvants and immunization strategies that combine the efficacy of live vaccines with the safety of dead vaccines.