Complement Activation on Neisseria meningitidis

脑膜炎奈瑟菌的补体激活

• 批准号: 6731387
• 负责人: SANJAY RAM
• 金额: $ 32.2万
• 依托单位: BOSTON MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6731387
• 关键词: Neisseria meningitidis; bactericidal immunity; cell line; classical complement pathway; clinical research; complement pathway regulation; ethanolamines; flow cytometry; fluorescence microscopy; genetic strain; human subject; immunofluorescence technique; lipopolysaccharides; monosaccharides; phlebotomy; phosphates; protein isoforms

DESCRIPTION (provided by applicant): Serogroup B Neisseria meningitidis infections are a major cause of morbidity and mortality worldwide. Complement (C) is important in combating neisserial infections. Individuals with C deficiency are predisposed to neisserial infections. Antibodies (Abs) that induce bactericidal killing protect against invasive disease. We have identified lipooligosaccharide (LOS) as a major C4b target when other than specific anti-capsular Abs are used for opsonization. Phosphoethanolamine (PEA) on heptose 2 (Hep2) of LOS is an important acceptor for C4 (based on our data that C4b binds LOS via amide bonds). In specific Aim 1 we will study the relative roles of PEA residues in the 3- and 6-position of Hep2 in accepting C4b, by comparing C4b binding to LOS on strains that differ only in the location of PEA (either the 3- or 6-position) on Hep2. We have determined that Hep1 chain substitutions influence the nature of the linkage (ester or amide) formed between C4b and LOS. We will extend these findings and study the effect of Hep2 hexose substitutions (the IgtG gene product) on C4b binding to LOS. In Specific Aim 2, we will examine the ability of the isoforms of C4 in human serum to bind to LOS in the context of whole bacteria. Two isoforms of C4 with differing biological activities, called C4A and C4B, exist in human serum. While C4B is ~3 times more hemolytically active, C4A engages its target via exclusively amide linkages and binds complement receptor 1 (CR1) more efficiently. The ability of bacteria opsonized with serum selectively deficient in C4A and C4B to bind to CR1 will be studied in a chinese hamster ovary (CHO) cell line transfected with a mutant CR1 molecule that contains only the C4b binding site. Finally, in specific Aim 3, we will examine whether bacterial targets for C4b binding are altered by mAbs against a repertoire of bacterial antigens, in an effort to understand why certain antigenic targets (such as class 4 protein) are not good bactericidal targets despite being recognized by C-fixing Abs. We will also determine the relative efficiency with which two mAbs that deposit C4b on to different targets elicit C-mediated killing, in an attempt to define the requirements for a vaccine candidate to elicit the most efficient bactericidal (or opsonic) response.

描述（由申请人提供）： B 群脑膜炎奈瑟菌感染是全世界发病和死亡的主要原因。补体 (C) 对于对抗奈瑟氏菌感染很重要。缺乏 C 的个体容易感染奈瑟氏菌。诱导杀菌的抗体 (Abs) 可防止侵袭性疾病。当使用特定抗荚膜抗体以外的药物进行调理作用时，我们已确定脂寡糖 (LOS) 是主要的 C4b 靶标。 LOS 的庚糖 2​​ (Hep2) 上的磷酸乙醇胺 (PEA) 是 C4 的重要受体（根据我们的数据，C4b 通过酰胺键结合 LOS）。在具体目标 1 中，我们将通过比较仅 PEA 位置不同的菌株（无论是 3 位还是 6 位）上 C4b 与 LOS 的结合，研究 Hep2 3 位和 6 位 PEA 残基在接受 C4b 方面的相对作用。 -位置）在 Hep2 上。我们已经确定 Hep1 链取代会影响 C4b 和 LOS 之间形成的键（酯或酰胺）的性质。我们将扩展这些发现并研究 Hep2 己糖替代（IgG 基因产物）对 C4b 与 LOS 结合的影响。在具体目标 2 中，我们将检查人血清中 C4 异构体在整个细菌中与 LOS 结合的能力。人血清中存在两种具有不同生物活性的 C4 异构体，称为 C4A 和 C4B。虽然 C4B 的溶血活性高出约 3 倍，但 C4A 仅通过酰胺键结合其靶标，并更有效地结合补体受体 1 (CR1)。将在用仅含有 C4b 结合位点的突变型 CR1 分子转染的中国仓鼠卵巢 (CHO) 细胞系中研究用选择性缺乏 C4A 和 C4B 的血清调理的细菌与 CR1 结合的能力。最后，在具体目标 3 中，我们将检查针对细菌抗原库的单克隆抗体是否会改变 C4b 结合的细菌靶点，以努力了解为什么某些抗原靶点（例如 4 类蛋白）尽管被认为是良好的杀菌靶点，但并不是良好的杀菌靶点。由 C 固定 Abs 识别。我们还将确定将 C4b 沉积到不同靶标上的两种 mAb 引发 C 介导的杀伤的相对效率，试图确定候选疫苗引发最有效的杀菌（或调理）反应的要求。