Surface Proteins of Bacillus anthracis

描述(申请人提供)：炭疽杆菌是炭疽病的病原体，炭疽病是一种人畜共患病，通过在受感染宿主中萌发的孢子传播。由此产生的炭疽杆菌繁殖体入侵并在所有宿主器官中复制，引发致命的感染后果，随后产生孢子进行传播。聚-D-3-谷氨酸(PDGA)胶囊的形成代表了炭疽杆菌的一个关键毒力策略。此外，炭疽杆菌还阐述了一种蛋白质表层(S)，它由24种S蛋白质组成，这是这种微生物毒力所必需的。S层蛋白的功能包括细菌与宿主组织的黏附，清除血红素铁，以及控制炭疽杆菌的链长以逃避吞噬清除。S层的组装是由一台专门的SEC机器通过细菌质膜上的前体运输来启动的。S层蛋白随后通过其S层同源结构域与丙酮化/乙酰化的次生细胞壁多糖(SCWP)联系在一起，SCWP是一种与肽聚糖相连的碳水化合物。S-层蛋白可能对胶囊的组装起到作用。在炭疽杆菌中，线性的PDGA链连接到肽聚糖上，并穿过S层。引起炭疽样呼吸道疾病的蜡状芽孢杆菌G9241阐述了一种透明质酸胶囊；其遗传决定因素在炭疽杆菌中是保守的。我们建议利用炭疽致病的分子遗传学方法和动物模型来鉴定炭疽杆菌S层毒力的关键因子，以评价它们在炭疽致病中的分子贡献，并探索它们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被膜的化学成分，S层蛋白运输和胶囊合成的显微分析，与SCWP结合的SLH结构域的结构生物学，炭疽杆菌宿主受体的特性，以及开发结合胶囊-S层蛋白疫苗来保护实验动物免受炭疽热致死攻击。

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.