Germination of Bacillus anthracis Spores in Macrophages

描述（由申请人提供）：炭疽是由吸入、摄入或通过切割或磨损吸收炭疽芽孢杆菌孢子引起的。在炭疽芽胞杆菌发病的一个重要步骤是代谢休眠孢子转化为营养的，产生毒素的细菌。过去的研究主要集中在炭疽毒素杀死巨噬细胞的机制上。最近的研究已经开始探索负责炭疽芽孢萌发及其随后在巨噬细胞中存活的因素。孢子被巨噬细胞吞噬，在那里它们发芽并开始合成毒素。随后巨噬细胞的释放导致营养细菌在血液中的增殖和大量毒素的产生。巨噬细胞内的孢子萌发是感染过程中一个关键但尚未被充分理解的步骤。目前尚不清楚哪个液泡室或孢子特性对发芽至关重要。我们的工作假设是，萌发需要一个特定的内体/吞噬体隔室，该隔室具有适当的物理和营养因子，可被病原分离物的吞噬孢子识别，并且萌发需要特定的受体和/或特定的孢子表面特性。为了验证这一假设，我们提出了两种方法：1)最初引导或限制孢子进入不同的吞噬体室，然后在不同的步骤阻止液泡重排，以研究对孢子摄取和萌发的影响。2)选择巨噬细胞特异性的、缺乏萌发的孢子，从而鉴定细胞内萌发所必需的孢子成分。我们的研究结果将定义炭疽芽胞杆菌萌发所需的液泡的隔室，巨噬细胞特异性萌发缺陷炭疽芽胞杆菌突变体将有助于阐明巨噬细胞萌发所必需的孢子成分。这些结果将促进我们对体内孢子萌发和这一过程所必需的炭疽芽孢孢子特性的理解。本研究结果可为开发有效抑制炭疽芽孢杆菌在巨噬细胞内萌发的药物提供参考。

DESCRIPTION (provided by applicant): Anthrax is caused by the inhalation, ingestion or uptake through a cut or abrasion of spores of Bacillus anthracis. An essential step in B. anthracis pathogenesis is the transformation of metabolically dormant spores into vegetative, toxin-producing bacteria. Past research has primarily focused on the mechanism of macrophage killing by anthrax toxins. Recent studies have begun to explore factors that are responsible for the germination of B. anthracis spores and their subsequent survival in the macrophages. The spores are engulfed by macrophages where they germinate and commence the synthesis of toxins. Subsequent release from macrophages leads to proliferation in the blood of vegetative bacteria and extensive toxin production. Spore germination within the macrophage is a critical but not well-understood step in the infection process. It is not currently known which vacuolar compartment or spore properties are essential for germination. Our working hypothesis is that germination requires a specific endosomal/phagosomal compartment with appropriate physical and nutritional factors recognized by engulfed spores from pathogenic isolates and that germination requires specific receptors and/or specific spore surface properties. In order to test this hypothesis, we propose two approaches: 1) initially direct or limit spores to different phagosomal compartments and then block vacuole rearrangement at distinct steps in order to examine the effects on spore uptake and germination. 2) Select for macrophage-specific, germination deficient spores and thus identify spore components essential for intracellular germination. Results from our study will define the compartment of the vacuoles required for B. anthracis germination, and the macrophage-specific germination-deficient B.anthracis mutants should help to elucidate spore components essential for germination in macrophages. These results will advance our understanding of in vivo spore germination and the properties of B. anthracis spores necessary for this process. This information could be helpful for developing pharmaceutical agents useful for preventing the germination of B. anthracis spores inside macrophages.