B. anthracis: passive immunization with anticapsular mAb

性状（由申请方提供）：炭疽芽孢杆菌被由聚-？- D-谷氨酸（？DPGA）。什么？DPGA胶囊是一个有吸引力的免疫保护靶点，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点。事实上，双重目标战略具有相当大的协同潜力。然而，针对B.炭疽菌荚膜用于主动或被动免疫需要了解荚膜抗体如何介导保护和鉴定保护的体内相关物。这些信息对于很少有自然发生的疾病的选择剂特别重要，这将允许评估主动或被动免疫效力。六个单克隆抗体（mAb）反应？DPGA是在本赠款期内产生和研究的。大多数为IgG 3亚类。五个是保护性的，一个不是。从两种保护性mAb产生IgG亚类转换家族（IgG 3-> IgG 1-> IgG 2b-> IgG 2a）。尽管具有相同的可变区，但IgG 1、IgG 2b和IgG 2a变体未能保护。所有保护性mAb的共同特征是i）IgG 3亚类，ii）高固有亲和力，和iii）抗体在结构上重塑囊外边缘的能力。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个？DPGA mAb是保护性的，另一个？DPGA mAb未能保护。总体假设是，抗体的保护能力依赖于IgG亚类，取决于i）mAb以亲和力依赖性方式重塑包膜边缘的能力，ii）每个亚类的固有生物活性，以及iii）效应细胞对信号传导的反应通过激活或抑制性Fc受体。这一假设将在五个特定目的中进行检验，这些特定目的将检验IgG亚类和亲和力作为影响保护的自变量的作用。特异性目标1将鉴定影响mAb亲和力的IgG重链结构域。特异性目标2将评估IgG亚类和亲和力在保护中的作用。特异性目的3将评价不同IgG亚类的mAb之间的协同作用。目的4将研究FcR信号传导在保护中的作用。最后，目标5将利用目标1-4中产生的信息优化预防和治疗鼠和兔肺炭疽的参数。公共卫生相关性：该项目将确定针对炭疽杆菌外壳的抗体的保护机制。这些信息对于制定新一代炭疽疫苗或设计治疗人类炭疽病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.