B. anthracis: passive immunization with anticapsular mAb

描述（由申请人提供）：炭疽芽孢杆菌被一种由聚？- d -谷氨酸？DPGA)。的吗?DPGA胶囊是一种有吸引力的免疫保护靶标，因为它对毒力至关重要，并且除了目前靶向的保护性抗原外，还为疫苗开发提供了第二个靶标。事实上，在双重目标战略中有相当大的协同潜力。然而，针对炭疽芽胞杆菌胶囊进行主动或被动免疫将需要了解胶囊抗体如何介导保护和体内保护相关物质的鉴定。对于一种很少自然发生疾病的选定制剂，这种信息尤其重要，可以用来评价主动或被动免疫的效力。6种单克隆抗体（mab）与？DPGA是在当前拨款期间产生和研究的。大多数是IgG3亚型。其中五个是保护性的；一个没有。IgG亚类开关家族（IgG3 -> IgG1 -> IgG2b -> IgG2a）由两种保护性单抗生成。尽管具有相同的可变区域，IgG1、IgG2b和IgG2a变体未能起到保护作用。所有保护性单抗的共同特征是i) IgG3亚类，ii)高内在亲和力，以及iii)抗体在结构上重塑荚膜外缘的能力。这种竞争性更新的总体目标是在分子水平上理解为什么是一种？DPGA单抗具有保护作用，另一个？DPGA mAb不能保护。总体假设是，抗体的IgG亚类依赖性保护能力取决于i)单抗以亲和力依赖的方式重塑荚膜边缘的能力，ii)每个亚类的固有生物活性，以及iii)效应细胞通过激活或抑制Fc受体对信号传导的反应。这一假设将在五个具体目标中进行检验，这些目标将检验IgG亚类和亲和力作为影响保护的独立变量的作用。特异性Aim 1将鉴定影响单抗亲和力的IgG重链结构域。特异性目的2将评估IgG亚类和亲和力在保护中的作用。特异性Aim 3将评估不同IgG亚类单克隆抗体之间的协同作用。目的4将研究FcR信号在保护中的作用。最后，Aim 5将利用Aims 1-4中产生的信息来优化预防和治疗小鼠和家兔肺炭疽的参数。公共卫生相关性：本项目将确定针对炭疽芽孢杆菌外壳的抗体的保护机制。这一信息对于制定新一代炭疽疫苗或设计用于治疗人类炭疽的基因工程抗体的决策至关重要。

DESCRIPTION (provided by applicant): Bacillus anthracis is surrounded by an antiphagocytic capsule that is composed of poly-?-D-glutamic acid (? DPGA). The ? DPGA capsule is an attractive target for immunoprotection because it is essential for virulence and offers a second target for vaccine development in addition to the currently targeted protective antigen. Indeed, there is considerable potential for synergy in a dual target strategy. However, targeting the B. anthracis capsule for active or passive immunization will require an understanding of how capsular antibodies mediate protection and an identification of in vivo correlates of protection. Such information is particularly important with a select agent for which there is little naturally occurring disease that would allow for evaluation of active or passive immunization efficacy. Six monoclonal antibodies (mAbs) reactive with ? DPGA were generated and studied during the current grant period. Most were of the IgG3 subclass. Five were protective; one was not. IgG subclass switch families (IgG3 -> IgG1 -> IgG2b -> IgG2a) were generated from two of the protective mAbs. Despite having identical variable regions, the IgG1, IgG2b and IgG2a variants failed to protect. Features common to all protective mAbs were i) the IgG3 subclass, ii) high intrinsic affinity, and iii) and the ability of the antibody to structurally remodel the capsular outer edge. The overall goal of this competing renewal is to understand, at a molecular level, why one ? DPGA mAb is protective and another ? DPGA mAb fails to protect. The overall hypothesis is that the IgG subclass- dependent ability of an antibody to protect is dependent on i) the ability of the mAb to remodel the capsular edge in an affinity-dependent manner, ii) the inherent biological activities of each subclass, and iii) the response of effector cells to signaling via activation or inhibitory Fc receptors. This hypothesis will be examined in five Specific Aims that will examine the roles of IgG subclass and affinity as independent variables that influence protection. Specific Aim 1 will identify the IgG heavy chain domains that influence mAb affinity. Specific Aim 2 will assess the roles of IgG subclass and affinity in protection. Specific Aim 3 will evaluate synergy between mAbs of different IgG subclasses. Aim 4 will examine the role of FcR signaling in protection. Finally, Aim 5 will utilize information generated in Aims 1-4 to optimize parameters for prevention and treatment of murine and rabbit pulmonary anthrax. PUBLIC HEALTH RELEVANCE: This project will determine the mechanism for protection by antibodies directed toward the outer coat of Bacillus anthracis. This information will be critical to decisions made in formulation of a new-generation anthrax vaccine or the design of genetically engineered antibodies to treat anthrax in humans.