Immunobiology of Bacillus anthracis Spore-Host Interactions

描述(由申请人提供)：炭疽芽孢杆菌作为生物武器的使用取决于其孢子在环境中的扩散、进入人体、人类宿主细胞对孢子的摄取、宿主内孢子的萌发以及宿主对宿主内营养细胞阐述的毒素的反应的病理后果。人们对孢子进入宿主的机制知之甚少，包括呼吸道、消化道和皮肤中靶细胞类型的性质，以及它们随后与先天和获得性免疫反应的细胞和体液成分的最初接触。了解这些寄主-孢子相互作用和孢子萌发过程中对孢子的非常早期的免疫反应，可能有助于开发一种介入性疫苗或药物策略，在孢子萌发和寄主内营养形态生长之前采取行动，从而防止炭疽病的发展。我们已经确定了与炭疽杆菌孢子最初接触有关的小鼠细胞类型，现在将分析孢子进入和摄取后激活的信号通路。我们将定义宿主细胞受体和孢子配体参与孢子摄取和诱导影响细胞内孢子存活的细胞内激活途径。多个基因靶向的小鼠将被用来识别这些促进或阻止孢子杀死双吞噬细胞的途径。我们将在体内测试抗孢子抗体对孢子命运的影响。这些目标将通过结合使用体外细胞系和原代吞噬细胞的流式细胞仪分析和生化分析来实现。如果我们能用抗体诱导被动保护性免疫，我们将尝试引起类似的疫苗诱导的免疫反应，并测试这些反应在长期记忆反应中的效果，并确定如果孢子与不同孢子靶标的抗体发生调理，它们在细胞内的命运。通过识别这些抗体的孢子相关靶分子，我们将能够确定在感染点和营养细胞生长导致毒血症和败血症死亡之前快速灭活孢子的潜在机制。这种性质的治疗策略将是对目前以PA为基础的疫苗以及当前推荐的抗生素方案的主要补充，对于经过改造以产生额外毒素的多重耐药炭疽杆菌菌株而言。公共卫生相关性：炭疽芽孢杆菌孢子作为恐怖主义的媒介传播，对文职和军事人员来说仍然是一个重要问题。外孢子层是该生物体孢子阶段的最外层，是孢子与寄主细胞接触的第一个点。通过定义孢子表面的分子和宿主细胞上的受体，我们可能能够开发出干预策略来诱导免疫保护，或者开发药物来灭活或破坏孢子，从而防止细菌的发展、毒素的形成和死亡。

DESCRIPTION (provided by applicant): The use of Bacillus anthracis as a bioweapon depends on dispersal of its spores in the environment, entrance into the body, spore uptake by the human host cells, germination of the spores in the host and the pathological consequences of the host response to the toxins elaborated by the vegetative cells within the host. Very little is known of the mechanisms of spore entry into the host, including the nature of targeted cell types in the airways, digestive tract and skin, and their subsequent initial encounter with cellular and humoral elements of the innate and adaptive immune response. An understanding of these host-spore interactions and the very early immune responses to the spores as they initiate the germination process will likely permit the development of an interventional vaccine or drug strategy that would act prior to the germination of spores and outgrowth of the vegetative form within the host and thus prevent development of Anthrax. We have identified mouse cell types involved in initial B. anthracis spore contact and will now analyze signaling pathways activated after spore entry and ingestion. We will define host cell receptors and spore-ligands involved in spore uptake and induction of intracellular activation pathways that affect intracellular spore survival. Multiple gene- targeted mice will be used to identify these pathways which promote or block spore killing bi phagocytic cells. We will test the effects of anti-spore antibodies on the fate of spores in vivo. These goals will be achieved by a combination of flow cytometric analysis and biochemical analysis using in vitro cells lines and primary phagocytes. If we can induce passive protective immunity with antibodies, we will attempt to elicit similar vaccine-induced immune responses and test the effects of these in long-term memory responses and determine the intracellular fate of spores if they are opsonized with antibodies to different spore targets. By identifying the spore-associated target molecules of these antibodies, we will be able to identify potential mechanisms to rapidly inactivate spores prior to establishment of infectious loci and vegetative cell outgrowth resulting in death from toxemia and septicemia. Therapeutic strategies of this nature would be a major supplement to the current PA-based vaccines as well as to the current recommended antibiotic regimens and in the case of multi-resistant B. anthracis strains engineered to produce additional toxins. Public Health Relevance: Bacillus anthracis spore dispersal as an agent of terrorism remains as an important issue to both civilian and military personnel. The exosporium, being the outermost layer of the spore stage of this organism, is the first point of contact of spores with host cells. By defining the molecules on the surface of spores and the receptors on host cells we may be able to develop interventional strategies to induce immune protection or drugs that will inactivate or destroy spores thus preventing bacterial development, the elaboration of toxins, and death.