Evasion of host immunity by the M protein

M蛋白逃避宿主免疫

基本信息

批准号：
10763296
负责人：
PARTHO GHOSH
金额：
$ 4.57万
依托单位：
UNIVERSITY OF CALIFORNIA, SAN DIEGO
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-01 至 2025-06-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10763296
关键词：
3-Dimensional Acute Amino Acid Sequence Amino Acids Antibodies Antigenic Variation Antigens Attenuated Autoimmune Bacteria Binding Binding Proteins Blood Cell Wall Collaborations Complement 3b Complement Factor H Complex Consensus Crystallography Deposition Development Disease Fibrinogen Goals Hand Human Immune Immune system Immunity Infection Inflammatory Knowledge Life Microbiology Morbidity - disease rate Nature Opsonin Pattern Phagocytes Prevention strategy Productivity Property Proteins Public Health Publishing Reporting Research Personnel Resistance Role Sea Streptococcus pyogenes Surface Testing Therapeutic Vaccine Design Vaccines Variant Virulence Virulence Factors Work X-Ray Crystallography complement 4b-binding protein design mortality multiple myeloma M Protein neutralizing antibody novel novel therapeutics pathogenic bacteria protein complex recruit success uptake

项目摘要

Group A Streptococcus (GAS, S. pyogenes) remains a major public health threat. This widespread Gram- positive bacterial pathogen causes acute invasive diseases and gives rise to severe autoimmune sequelae, and is responsible for morbidity and mortality on a global scale. An essential virulence factor of GAS, the antigenically variable M protein, enables the bacterium to evade opsonophagocytic killing by the immune system. The M protein confers this indispensable function of phagocyte resistance by recruiting specific soluble human proteins to the GAS surface that block the deposition of the major opsonin C3b as well as antigen- specific opsonic antibodies — namely, C4b-binding protein (C4BP), factor H (FH), and fibrinogen (Fg). In some GAS strains, an M-like protein serves this function. More than 220 M types are known, and while most M protein types bind C4BP, FH, or Fg, or a combination of these, no consensus binding motif is evident in M and M-like proteins for any of these human proteins, except most recently for C4BP due to our breakthrough. This is because the exposed portion of the M protein that recruits these anti-opsonic human proteins is sequence variable. While inhibition of these interactions has been shown to render GAS sensitive to immune killing, the lack of consensus binding motifs has hindered the therapeutic goal of targeting these interactions. Our recent breakthrough, reported in Buffalo et al., offers a solution to this problem. In effect, we found that hidden within the variable region of many M proteins is a three-dimensional (3D) pattern that is conserved for binding C4BP. This 3D C4BP-binding pattern in the M protein is dispersed (or hidden) within a sea of variable amino acids, which makes the 3D pattern nearly impossible to identify by primary sequence alone. However with structural knowledge in hand as a guiding template, the 3D pattern becomes easily recognizable within the primary sequence of many M types. We hypothesize that just as with C4BP, hidden within the variable regions of M and M-like proteins are 3D patterns that are conserved for binding FH and Fg. We propose to test this emerging theme of conservation hidden within variability by unveiling potentially conserved FH- and Fg-binding 3D patterns in M and M-like proteins. We also propose to complete our work on C4BP, as the 3D pattern we discovered and published in Buffalo et al. explains only about a half of the set of M proteins implicated in C4BP binding. We propose to carry this out through X-ray crystallography. We have an extensive record of success with crystallographic studies of the M protein, and have obtained initial co-crystals of M proteins bound to C4BP, FH, and Fg. In each case, we will take advantage of the highly detailed level of information provided by our structural studies to determine the precise functional contributions of each of these interactions to virulence through our long-standing collaboration with co-Investigator Victor Nizet (UCSD). The results from our studies will provide essential guidance in designing anti-virulence strategies, and may have applications in the development of a broadly neutralizing GAS vaccine.

A 组链球菌（GAS、化脓性链球菌）仍然是主要的公共卫生威胁。阳性细菌病原体引起急性侵袭性疾病并引起严重的自身免疫后遗症，是 GAS 的一个重要毒力因子，导致全球范围内的发病率和死亡率。抗原性可变的 M 蛋白，使细菌能够逃避免疫调节吞噬细胞的杀伤 M 蛋白通过招募特定的可溶性物质赋予吞噬细胞抵抗这一不可或缺的功能。人类蛋白质到 GAS 表面，阻止主要调理素 C3b 以及抗原的沉积特异性调理性抗体，即 C4b 结合蛋白 (C4BP)、H 因子 (FH) 和纤维蛋白原 (Fg)。在一些 GAS 菌株中，已知有超过 220 个 M 类型的 M 样蛋白，而大多数 M 类型。蛋白质类型结合 C4BP、FH 或 Fg 或这些的组合，M 和中没有明显的共有结合基序任何这些人类蛋白质的 M 样蛋白质，除了最近由于我们的突破而出现的 C4BP。是因为招募这些抗调理人类蛋白的 M 蛋白的暴露部分是虽然抑制这些相互作用已被证明会使 GAS 对免疫敏感。杀伤，缺乏一致的结合基序阻碍了针对这些的治疗目标 Buffalo 等人报道的我们最近的突破实际上为这个问题提供了解决方案。发现许多 M 蛋白的可变区中隐藏着一个三维 (3D) 模式， M 蛋白中的这种 3D C4BP 结合模式是分散的（或隐藏的）。在可变氨基酸的海洋中，这使得 3D 模式几乎不可能通过初级识别然而，有了现有的结构知识作为指导模板，3D 图案就变成了。就像 C4BP 一样，我们在许多 M 类型的初级序列中很容易识别。隐藏在 M 和 M 样蛋白的可变区内的是保守的 3D 模式结合 FH 和 Fg，我们建议通过以下方式测试隐藏在可变性中的保护这一新兴主题。我们还建议揭示 M 和 M 样蛋白中潜在保守的 FH 和 Fg 结合 3D 模式。完成我们在 C4BP 上的工作，作为我们在 Buffalo 等人中发现并发布的 3D 模式。大约一半的 M 蛋白与 C4BP 结合有关，我们建议通过 X 射线来实现这一点。我们在 M 蛋白的晶体学研究方面拥有广泛的成功记录，并且已获得与 C4BP、FH 和 Fg 结合的 M 蛋白的初始共晶体。利用我们的结构研究提供的高度详细的信息来确定精确的通过我们的长期合作，这些相互作用对毒力的功能贡献联合研究员 Victor Nizet（加州大学圣地亚哥分校）的研究结果将为设计提供重要指导。抗毒力策略，并可能应用于开发广泛中和的 GAS 疫苗。