Surface Proteins of Bacillus anthracis

描述（由申请人提供）：炭疽芽孢杆菌是炭疽的病原体，炭疽是一种人畜共患疾病，通过孢子在被感染的宿主中萌发传播。由此产生的营养形式的炭疽芽孢杆菌侵入并在所有宿主器官中复制，引发致命的感染结果，随后产生孢子传播。聚d -3-谷氨酸（PDGA）胶囊的形成是炭疽杆菌的一个关键毒力策略。此外，炭疽芽孢杆菌形成了一个由24个S层蛋白质组成的蛋白质表面(S)层，这是这种微生物的毒性所必需的。s层蛋白的功能包括杆菌附着于宿主组织，清除血红素铁，以及控制炭疽杆菌链长度以逃避吞噬清除。s层组装是通过专门的Sec机器通过细菌质膜的前体运输开始的。s层蛋白随后通过其s层同源性（SLH）结构域与丙酮酰化/乙酰化的次级细胞壁多糖（SCWP）结合，SCWP是一种与肽聚糖相连的碳水化合物。s层蛋白可能有助于胶囊的组装。在炭疽杆菌中，线性PDGA链与肽聚糖相连，并穿过s层。引起炭疽样呼吸道疾病的蜡样芽孢杆菌G9241形成透明质酸胶囊；其遗传决定因素在炭疽杆菌中是保守的。我们建议利用分子遗传学方法和炭疽发病机制的动物模型来鉴定炭疽芽孢杆菌的关键s层毒力因子，了解其在炭疽发病机制中的分子作用，并探索其在炭疽疫苗开发中的潜力。我们的实验计划包括研究炭疽杆菌包膜的化学成分，s层蛋白运输和胶囊合成的显微镜分析，SLH结构域与SCWP关联的结构生物学，炭疽杆菌宿主受体的表征以及开发结合胶囊- s层蛋白疫苗以保护实验动物免受致命炭疽的攻击。

DESCRIPTION (provided by applicant): Bacillus anthracis is the causative agent of anthrax, a zoonotic disease transmitted by spores that germinate in the infected host. The resulting vegetative forms of B. anthracis invade and replicate in all host organs, triggering a lethal outcome to infection and subsequently generating spores for dissemination. Formation of a poly-D-3-glutamic acid (PDGA) capsule represents a key virulence strategy of anthrax bacilli. Further, B. anthracis elaborates a protein surface (S)-layer that is composed of twenty-four S-layer proteins, which are required for this microbe's virulence. The functions of S-layer proteins include the adherence of bacilli to host tissues, the scavenging of heme-iron, and the control of B. anthracis chain length as an escape from phagocytic clearance. S-layer assembly is initiated via precursor transport across the bacterial plasma membrane by a specialized Sec machine. S-layer proteins subsequently associate via their S-layer homology (SLH) domains with pyruvylated / acetylated secondary cell wall polysaccharide (SCWP), a carbohydrate that is linked to peptidoglycan. S-layer proteins likely contribute to capsule assembly. In B. anthracis, linear PDGA strands are linked to peptidoglycan and threaded across the S-layer. Bacillus cereus G9241, which causes anthrax-like respiratory disease, elaborates a hyaluronic acid capsule; its genetic determinants are conserved in B. anthracis. We propose to use molecular genetic approaches and animal models of anthrax pathogenesis to identify key S-layer virulence factors of B. anthracis, to appreciate their molecular contribution to anthrax pathogenesis and to explore their potential for anthrax vaccine development. Our experimental plan entails studies on the chemical composition of the B. anthracis envelope, microscopic analysis of S-layer protein traffic and capsule synthesis, the structural biology of SLH domain association with SCWP, the characterization of the host receptor for B. anthracis and the development of conjugate capsule-S-layer protein vaccines to protect experimental animals against lethal anthrax challenge.