B. anthracis: passive immunization with anticapsular mAb

描述(申请人提供)：炭疽杆菌被一个由聚-D-谷氨酸(？DPGA)。那个？DPGA胶囊是一个有吸引力的免疫保护目标，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点。事实上，双重目标战略有相当大的协同潜力。然而，以炭疽杆菌胶囊为目标进行主动或被动免疫将需要了解衣壳抗体如何介导保护，并确定体内保护相关因素。这种信息对于选择的制剂尤其重要，因为它几乎没有自然发生的疾病，可以用来评估主动或被动免疫效果。6株与？DPGA是在当前赠款期间生成和研究的。大多数是IgG3亚类。五个是保护性的；一个不是。Ig G亚类开关家族(Ig G3-&Gt；Ig G1-&Gt；Ig G2b-&Gt；Ig G2a)是由两株保护性单抗合成的。尽管有相同的可变区，但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)抗体在结构上重塑囊膜外缘的能力。这种相互竞争的更新的总体目标是在分子水平上理解为什么是一个？DPGA单抗具有保护性，而另一种？DPGA单抗不能起到保护作用。总的假设是，抗体的免疫球蛋白亚类依赖的保护能力依赖于1)单抗以亲和力依赖的方式重塑被膜边缘的能力，2)每个亚类的固有生物学活性，以及3)效应细胞通过激活或抑制Fc受体对信号的反应。这一假设将在五个具体目标中进行检验，这些目标将考察作为影响保护的独立变量的免疫球蛋白亚类和亲和力的作用。特异性目标1将确定影响单抗亲和力的免疫球蛋白重链结构域。具体目标2将评估免疫球蛋白亚类和亲和力在保护中的作用。特异靶3将评估不同免疫球蛋白亚类单抗之间的协同作用。目标4将研究FCR信号在保护中的作用。最后，目标5将利用目标1-4中产生的信息来优化小鼠和兔肺炭疽病的预防和治疗参数。公共卫生相关性：该项目将确定针对炭疽芽孢杆菌外层的抗体的保护机制。这些信息将对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.