Complement Activation on Neisseria meningitidis

脑膜炎奈瑟菌的补体激活

• 批准号: 8210933
• 负责人: SANJAY RAM
• 金额: $ 36.64万
• 依托单位: UNIV OF MASSACHUSETTS MED SCH WORCESTER
• 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 2015-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8210933
• 关键词: Address; Affect; Animal Model; Antibiotics; Antibodies; Antibody Specificity; Antigens; Bacteria; Binding; Binding Proteins; Blood; Blood Circulation; Cerebrospinal Fluid; Child; Classical Complement Pathway; Clinical; Complement; Complement 4b; Complement Activation; Complement Factor B; Complement Factor H; Complement Membrane Attack Complex; Complex; Defense Mechanisms; Deposition; Development; Disease; Encapsulated; Epidemiology; Equilibrium; Fc domain; Feedback; Funding; Genome; Goals; Gold; Grant; Health; Host Defense; Human; Hybrids; IgG1; Immune; Immunization; Immunoglobulin G; Immunoglobulin M; Inactivated Vaccines; Infection; Invaded; Knowledge; Lead; Ligands; Lipoproteins; Mediating; Membrane; Membrane Proteins; Meningococcal Infections; Meningococcal meningitis; Microbe; Modeling; Molecular; Morbidity - disease rate; Mucous Membrane; Nasopharynx; Neisseria; Neisseria meningitidis; Organism; Oryctolagus cuniculus; Outcome; Pathogenesis; Pathway interactions; Persons; Polysaccharides; Properdin; Protein Binding; Proteins; Recurrence; Regulation; Resistance; Role; Sepsis; Serum; Site; Specificity; Surface; System; Vaccination; Vaccines; Virulence; arm; bactericide; base; blocking factor; capsule; complement deficiency; complement pathway; complement system; design; disorder prevention; improved; inhibitor/antagonist; insight; killings; lipooligosaccharide; mortality; novel; pathogen; phosphoethanolamine; polyanion; public health relevance; vaccine candidate; vaccine development; vaccine efficacy; vaccine evaluation; young adult

DESCRIPTION (provided by applicant): Complement (C) is a key arm of innate immune defenses against invasive meningococcal infections. Neisseria meningitidis (Nm) have evolved several sophisticated mechanisms to evade host C. A balance between the hosts' efforts to activate C on the bacterium and the microbe's C evasion strategies dictates whether the organism is cleared from the mucosa, remains an asymptomatic colonizer in the nasopharynx, or proceeds to cause invasive disease. In the previous funding period we characterized interactions between Nm and C4b, a component of the classical pathway (CP). Almost all Nm isolates recovered from the blood or cerebrospinal fluid are encapsulated and capsule is important for resistance to C. The molecular basis for capsule-mediated C resistance remains undefined. In Aim 1 will define the role of capsular polysaccharide (CPS) in regulating C. First, in Aim 1a, we will elucidate the reason for differences in the level of CP activation mediated by anti-CPS and anti-outer membrane Abs. On a molar basis, mAbs directed against CPS fix less C4b than mAbs against membrane structures, suggesting that efficient C4b binding may require activation of C4 proximate to the meningococcal molecules that serve as C4b acceptors such as LOS and opacity protein. Chimeric mAbs containing human IgG1 Fc and directed against either CPS or the Nm vaccine candidate, factor H-binding protein (fHbp) will be used to symmetrically compare the C-activating functions of these mAbs. The positive feedback loop of the alternative pathway (AP) is also important for bacterial killing by vaccine Abs. Our preliminary studies indicate that the group A, C, W-135 and Y (but not B) CPSs block activation of human C3 by purified human factors B and D. In Aim 1b we will define the molecular basis of AP inhibition by examining the interaction of CPS with purified AP components. These studies may identify a common mechanism of action for polyanions that block AP activation. AP regulation by CPS is human-specific; assembly of the rabbit AP (not regulated by CPS) will be examined in Aim 1c to provide a better understanding of the human-specificity of AP regulation by CPS. Surface proteins also contribute to C resistance; fHbp binds to the AP inhibitor, factor H (fH) and inhibits C activation. In Aim 2, we will we will exploit our knowledge of fH- fHbp interactions and use chimeric molecules to block fH binding to Nm and manipulate the C cascade to precisely define the roles of the CP and AP in killing Nm. We will also attempt to 'boost' the bactericidal function of an otherwise nonbactericidal anti-fHbp mAb (JAR 4). Such knowledge could lead to optimization of vaccine strategies. Finally, in Aim 3 we will define novel C evasion strategies in strains that express low levels of fHbp. Preliminary evidence indicates that low fHbp expressing/low fH binding Nm regulate C at the level of C5b-9 formation or insertion and we will characterize the molecular basis for C resistance at this level. These studies will help define novel mechanisms of C evasion by Nm; information that will advance understanding of meningococcal pathogenesis and improve ongoing efforts to develop effective protein-based vaccines. PUBLIC HEALTH RELEVANCE: Meningococcal meningitis and sepsis is a major health problem worldwide. It mainly affects children and young adults and is a significant cause of morbidity and mortality. Although a good vaccine exists against several meningococcal serogroups, there is no effective vaccine against serogroup B disease. The emergence of disease caused by strains that lack a capsule following vaccination campaigns using capsular polysaccharide-based vaccines is of concern. Complement forms an important arm of host defenses against the meningococcus. The studies proposed in this application will help us better understand how this pathogen escapes killing by complement and will ultimately aid in the development of better vaccines against meningococcal meningitis.

描述（由申请人提供）：补体（C）是针对侵袭性脑膜炎球菌感染的先天免疫防御的关键武器。脑膜炎奈瑟菌 (Nm) 已进化出多种复杂的机制来逃避宿主 C。宿主激活细菌上的 C 的努力与微生物的 C 逃避策略之间的平衡决定了该生物体是否从粘膜中清除，仍然是鼻咽中的无症状定植者，还是继续引起侵袭性疾病。在之前的资助期间，我们描述了 Nm 和 C4b 之间的相互作用，C4b 是经典途径 (CP) 的一个组成部分。几乎所有从血液或脑脊液中回收的 Nm 分离株均被包裹，并且荚膜对于 C 的耐药性很重要。胶囊介导的 C 耐药性的分子基础仍不清楚。在目标 1 中，我们将定义荚膜多糖 (CPS) 在调节 C 中的作用。首先，在目标 1a 中，我们将阐明抗 CPS 和抗外膜抗体介导的 CP 激活水平差异的原因。在摩尔基础上，针对CPS的mAb比针对膜结构的mAb固定更少的C4b，这表明有效的C4b结合可能需要激活脑膜炎球菌分子附近的C4，这些分子充当C4b受体，例如LOS和不透明蛋白。含有人 IgG1 Fc 并针对 CPS 或 Nm 候选疫苗 H 因子结合蛋白 (fHbp) 的嵌合 mAb 将用于对称比较这些 mAb 的 C 激活功能。旁路途径 (AP) 的正反馈回路对于疫苗抗体杀死细菌也很重要。我们的初步研究表明，A、C、W-135 和 Y 组（但不是 B）CPS 可以阻断纯化的人因子 B 和 D 对人 C3 的激活。在目标 1b 中，我们将通过检查 CPS 与纯化的 AP 成分的相互作用来定义 AP 抑制的分子基础。这些研究可能确定了聚阴离子阻断 AP 激活的共同作用机制。 CPS 对 AP 的调节是针对人类的；兔 AP（不受 CPS 调节）的组装将在目标 1c 中进行检查，以更好地了解 CPS 对 AP 调节的人类特异性。表面蛋白也有助于 C 抗性； fHbp 与 AP 抑制剂 H 因子 (fH) 结合并抑制 C 激活。在目标 2 中，我们将利用我们对 fH-fHbp 相互作用的知识，并使用嵌合分子来阻断 fH 与 Nm 的结合，并操纵 C 级联来精确定义 CP 和 AP 在杀死 Nm 中的作用。我们还将尝试“增强”非杀菌性抗 fHbp mAb (JAR 4) 的杀菌功能。这些知识可能会导致疫苗策略的优化。最后，在目标 3 中，我们将在表达低水平 fHbp 的菌株中定义新的 C 逃避策略。初步证据表明，低 fHbp 表达/低 fH 结合 Nm 在 C5b-9 形成或插入水平上调节 C，我们将在该水平上表征 C 抗性的分子基础。这些研究将有助于定义 Nm 逃避 C 的新机制；这些信息将增进对脑膜炎球菌发病机制的了解，并改进目前开发有效的蛋白质疫苗的努力。 公共卫生相关性：脑膜炎球菌性脑膜炎和败血症是全世界的一个主要健康问题。它主要影响儿童和年轻人，是发病和死亡的重要原因。尽管存在针对多种脑膜炎球菌血清群的良好疫苗，但尚无针对 B 血清群疾病的有效疫苗。在使用荚膜多糖疫苗进行疫苗接种后，由缺乏荚膜的菌株引起的疾病的出现令人担忧。补体形成宿主防御脑膜炎球菌的重要武器。本申请中提出的研究将帮助我们更好地了解这种病原体如何逃脱补体的杀伤，并最终有助于开发更好的针对脑膜炎球菌性脑膜炎的疫苗。