Virulence Gene Expression by Bacillus anthracis

描述(由申请人提供)：炭疽杆菌是一种革兰氏阳性芽胞形成土壤细菌，属于蜡状芽孢杆菌组物种，其特点是能够在哺乳动物(包括人类)中引起致命的炭疽病。这种生物特有的已知毒力因子是炭疽毒素蛋白和多聚D-谷氨酸胶囊。众多研究人员的发现已经确定了炭疽毒素和胶囊的结构和功能。我们实验室的工作主要集中在毒素蛋白PagA、LEF和CyA结构基因表达的遗传基础上，以及最近的胶囊生物合成操纵子capBCAD。我们的毒力基因调控模型越来越复杂，包括许多反式作用调节器。最关键和影响最深远的调控因子是Atxa，它似乎是炭疽杆菌独有的基因，Atxa对所有三个毒素基因的表达都是必不可少的，并有助于控制胶囊操纵子。在这里提出的实验中，我们将通过测试我们目前的毒力调控模型来继续我们对毒力基因表达的研究。我们的总体方法将是确定在体外培养的炭疽杆菌中毒力基因调节器的功能，并测试在小鼠吸入炭疽病模型中的意义。我们还将评估新发现的已建立调节器靶标的生理作用。最后，我们将探索典型的青霉素敏感和不太常见的青霉素耐药炭疽杆菌菌株之间β-内酰胺酶基因表达差异的分子基础。炭疽芽孢杆菌是选择药剂名单上的主要细菌。2001年秋天，美国故意释放孢子，导致11例炭疽病确诊病例和5人死亡，这一事件戏剧性地表明了这种微生物作为生物武器时可能构成的公共健康威胁。正如最近的美国病例所表明的那样，吸入炭疽芽胞可导致人类的致命临床后果，只有及时的接触后干预才能限制疾病的程度。我们的总体目标是在吸入性炭疽的小鼠模型中识别和表征影响炭疽杆菌感染的炭疽杆菌决定因素。这些决定因素是治疗干预的潜在目标和/或新亚单位疫苗的可能成分。

DESCRIPTION (provided by applicant): Bacillus anthracis, a Gram-positive spore-forming soil bacterium and member of the Bacillus cereus group species, is distinguished by its ability to cause lethal anthrax disease in mammals, including humans. Well-established virulence factors unique to this organism are the anthrax toxin proteins and a poly-D-glutamic acid capsule. Findings of numerous investigators have established the structure and function of the anthrax toxins and capsule. Work in our laboratory has focused on the genetic basis for expression of the structural genes for the toxin proteins, pagA, lef, and cya, and more recently, the capsule biosynthesis operon, capBCAD. Our model for virulence gene regulation is of increasing complexity and includes numerous trans-acting regulators. The most critical and far-reaching regulator is atxA, a gene that appears to be unique to B. anthracis, atxA is essential for expression of all three toxin genes and contributes to control of the capsule operon. In experiments proposed here, we will continue our investigations of virulence gene expression by testing our current model for regulation of virulence. Our overall approach will be to determine the function of virulence gene regulators in B. anthracis cultured in vitro and to test for significance in a mouse inhalation model for anthrax. We will also assess the physiological roles of newly identified targets of established regulators. Finally, we will probe the molecular basis for differences in beta-lactamase gene expression between prototypical penicillin-susceptible and less common penicillin-resistant B. anthracis stains. Bacillus anthracis is the lead bacterium on the Select Agent List. The intentional release of spores in the fall of 2001 in the U.S. that resulted in eleven confirmed cases of anthrax and five deaths dramatically illustrated the public health threat this organism can pose when as a bioweapon. As the recent U.S. cases showed, inhalation of B. anthracis spores can result in a fatal clinical outcome in humans and only timely post-exposure intervention can limit the extent of the disease. Our overall objective is to identify and characterize B. anthracis determinants that impact B. anthracis infection in a mouse model for inhalation anthrax. Such determinants are potential targets for therapeutic intervention and/or possible components for new subunit vaccines.