Molecular basis meningococcal group A capsular immunity

A 群脑膜炎球菌荚膜免疫的分子基础

• 批准号: 7066603
• 负责人: Dan M. Granoff
• 金额: $ 50.7万
• 依托单位: CHILDREN'S HOSPITAL & RES CTR AT OAKLAND
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7066603
• 关键词: African; Neisseria meningitidis; Neisseria meningitidis vaccine; antibacterial antibody; antigen antibody reaction; bacterial antigens; bacterial capsules; bacterial meningitis; bacterial polysaccharides; bacterial proteins; bacterial toxins; bactericidal immunity; clinical research; expression cloning; gene expression; genetic library; human subject; immunoglobulin G; immunoglobulin M; mass spectrometry; microorganism immunology; two dimensional gel electrophoresis; vaccine evaluation

DESCRIPTION (provided by applicant): Group A meningococci cause massive epidemics of meningitis and sepsis in sub-Saharan Africa. Compared to other bacterial polysaccharides (PS), group A has a number of unusual properties including being highly immunogenic in infants, and priming for booster antibody responses. Also, depending on the age of the person, or antigenic stimulus (natural exposure to group A or cross-reacting organisms, or conjugated vs. unconjugated PS vaccination), the PS can elicit bactericidal or non-bactericidal group A anticapsular antibodies. The role of non-bactericidal group A anticapsular antibodies in protection against group A disease is unknown, and the molecular basis for differences in antibody functional activity are poorly understood. Our hypothesis is that differences in antibody avidity and/or fine antigenic specificity, dictated by the structure of the antibody paratope, underlie these disparities in antibody functional activity. In this proposal we will characterize naturally acquired and vaccine-induced group A anticapsular antibodies from persons of different ages living in North America or sub-Saharan Africa, two areas of the world with vastly different risks of exposure to group A meningococci. Passive antibody protective activity will be measured in an animal model of group A bacteremia that will be developed. To define the V region genes utilized by the human antibody response to group A PS, and to determine the extent of hypermutation, we will perform combinatorial repertoire cloning and expression library analyses of group A PS-specific Fab fragments. This approach will be complemented by limited amino acid sequencing of VH and VL regions of clonally purified anticapsular antibodies and determination of V region genes by mass fingerprint analysis by MALDI-TOF mass spectroscopy of H and L chains separated by 2D gels. Together, these studies will elucidate the molecular basis by which human antibodies recognize group A PS, and will identify the mechanisms underlying the age- and vaccine-related disparities in antibody protective activity. The results may lead to establishment of more reliable surrogates of protective immunity for assessment of the efficacy of new group A conjugate vaccines being developed for elimination of epidemic meningococcal disease in sub-Saharan Africa. Our proposed studies also will increase our knowledge of human antibody recognition of bacterial PS antigens in general, and explain why some anticapsular antibodies confer protection against encapsulated bacteria, while others do not.

描述（由申请人提供）：A脑膜炎球菌在撒哈拉以南非洲引起脑膜炎和败血症的大规模流行病。与其他细菌多糖（PS）相比，A组具有多种异常特性，包括在婴儿中具有高度免疫原性，以及用于增强抗体反应的启动。同样，根据人的年龄或抗原刺激（自然暴露于A组或交叉反应生物，或共轭与未结合的PS疫苗接种），PS可以引起杀菌或非杀伤性的A抗囊抗体。非细菌抗体A抗体抗体在防御A组疾病中的作用尚不清楚，并且对抗体功能活性差异的分子基础知之甚少。我们的假设是，抗体亲和力和/或精细抗原特异性的差异取决于抗体角膜膜的结构，这是抗体功能活性的这些差异的基础。在此提案中，我们将表征来自北美不同年龄段的人或撒哈拉以南非洲的人的自然获得和疫苗诱导的A组抗体抗体，这是世界上两个地区，暴露于A组脑膜炎的风险截然不同。被动抗体保护活性将在将开发的A组动物模型中测量。为了定义人类抗体对A组PS的抗体响应所使用的V区域，并确定过度折磨的程度，我们将执行A组PS特异性FAB片段的组合曲目克隆和表达库分析。这种方法将通过克隆纯化的抗囊抗体的VH和VL区域的有限氨基酸测序以及通过MALDI-TOF质谱H和L链的质谱分析的质量指纹分析来确定V区域基因的H和L链，该链的H和L链被2D凝胶分离。总之，这些研究将阐明人类抗体识别A组PS的分子基础，并将确定抗体保护活性中与年龄和疫苗相关差异的机制。结果可能会导致建立更可靠的保护性免疫替代物，以评估新组A共轭疫苗的功效，以消除撒哈拉以南非洲的流行性脑膜炎球菌病。我们提出的研究还将增加我们对人类抗体对细菌PS抗原的识别的了解，并解释为什么某些抗囊抗体允许对包裹的细菌提供保护，而其他抗体则没有。