Epitope shifting and Antibody Maturation during Rotavirus Infection

轮状病毒感染期间的表位转移和抗体成熟

• 批准号: 8318028
• 负责人: BENJAMIN W SPILLER
• 金额: $ 23.39万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-15 至 2015-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8318028
• 关键词: Address; Adult; Affinity; Antibodies; Antibody Binding Sites; Antibody Formation; Antigens; Attenuated; Binding; Biochemical; Burial; Centers for Disease Control and Prevention (U.S.); Child; Complex; Crystallography; DNA Sequence Rearrangement; Data; Development; Diarrhea; Disease; Dose; Egg White; Epitopes; Family; Frequencies; Generations; Genes; Haptens; Head; Hot Spot; Human; Hydrophobic Surfaces; Immune response; Immune system; Immunity; Immunodominant Epitopes; Immunoglobulin Somatic Hypermutation; Infant; Infection; Lead; Light; Location; Methods; Modeling; Molecular; Molecular Immunology; Monoclonal Antibodies; Muramidase; Mutate; Process; Property; Proteins; Publishing; Reporting; Rotavirus; Rotavirus Infections; Rotavirus Vaccines; Side; Site; Site-Directed Mutagenesis; Somatic Mutation; Structure; Subunit Vaccines; Surface; Surrogate Markers; Testing; Vaccination; Vaccines; Variant; Viral Proteins; Virion; Virus; Work; base; chimeric antibody; improved; interest; mutant; neutralizing antibody; pathogen; progenitor; response

DESCRIPTION (provided by applicant): We will explore and determine the molecular mechanism for epitope shift, a recently recognized feature of affinity maturation in which somatic hypermutation changes the epitope recognized by mature antibodies from that recognized by germline antibodies. Our published work indicates that affinity maturation leads to both affinity and epitope selection changes, both of which can be critical for developing neutralizing antibodies. To date, this has been unappreciated because previous studies of affinity maturation have focused on cases where maturation improves affinity to an essentially identical epitope. This is the case both for protein antigens and haptens, as exemplified by structural and biochemical studies using hen egg white lysozyme and small haptens. In these cases, affinity maturation improves binding to identical epitopes. The anti-lysozyme antibodies are particularly interesting in this light, because they use large (~1,800E2) interfaces with essentially identical interactions where enhanced affinity arises from increased burial of hydrophobic surface at the edge of the interaction surface. These changes are driven by subtle rearrangements of non-hotspot residues. While the edge of the interaction surface changes in the anti- lysozyme antibodies, these changes do not lead to changes in the epitope recognized. In our model, this is because hot-spot residues are germline encoded. Our proposed work will explore changes hypothesized to occur within the antibody combining site and establish the mechanism whereby these changes cause epitope shifting. We will focus anti-rotavirus VP6 antibodies that use the VH1-46 gene segment. VP6 is the immunodominant epitope and VH1-46 is the dominant heavy chain gene segment seen in the antibody response against rotavirus. In general, adults produce neutralizing antibodies to rotavirus, but infants do not. This is not due to germline gene usage, but rather it is to more somatic hypermutation in adults. Rotaviruses are the most important cause of severe diarrhea in infants and young children in both the developed world and the developing world. Attenuated virus vaccines have been introduced, however even when properly administered in a controlled setting, these vaccines appear to reduce infection by only ~61%. Additionally, they offer no protection against emerging strains, and require multiple (2 or 3) doses. Second generation vaccines with improved efficacy are sought, and subunit vaccines are an attractive choice. CDC estimates are that even with vaccination ~500,000 people still die annually from rotavirus infection. Effective development of subunit vaccines is aided by a comprehensive understanding of the mechanisms the human immune system employs to recognize antigens and neutralize pathogens. This application will provide molecular immunology paradigms that may influence the choice of antigens, the use of surrogate markers of protection, and the development of new rotavirus vaccines. We will explore and determine the molecular basis for epitope shift.

描述（由申请人提供）：我们将探索和确定表位转移的分子机制，表位转移是最近公认的亲和力成熟特征，其中体细胞超突变改变了成熟抗体识别的表位与种系抗体识别的表位。我们发表的工作表明，亲和力成熟会导致亲和力和表位选择的变化，这两者对于开发中和抗体都至关重要。迄今为止，这一点尚未得到重视，因为之前的亲和力成熟研究主要集中在成熟提高对基本相同表位的亲和力的情况。蛋白质抗原和半抗原都是如此，使用鸡蛋清溶菌酶和小半抗原进行的结构和生化研究就证明了这一点。在这些情况下，亲和力成熟可改善与相同表位的结合。从这个角度来看，抗溶菌酶抗体特别令人感兴趣，因为它们使用大的（~1,800E2）界面，具有基本相同的相互作用，其中增强的亲和力是由于相互作用表面边缘疏水性表面的埋藏增加而产生的。这些变化是由非热点残基的微妙重排驱动的。虽然抗溶菌酶抗体中相互作用表面的边缘发生变化，但这些变化不会导致所识别的表位发生变化。在我们的模型中，这是因为热点残基是种系编码的。我们提出的工作将探索假设发生在抗体结合位点内的变化，并建立这些变化导致表位转移的机制。我们将重点关注使用 VH1-46 基因片段的抗轮状病毒 VP6 抗体。 VP6 是免疫显性表位，VH1-46 是在针对轮状病毒的抗体反应中看到的显性重链基因片段。一般来说，成人会产生轮状病毒的中和抗体，但婴儿不会。这不是由于种系基因的使用，而是由于成人中更多的体细胞超突变。轮状病毒是发达国家和发展中国家婴幼儿严重腹泻的最重要原因。减毒病毒疫苗已经问世，但即使在受控环境下正确接种，这些疫苗似乎也只能减少约 61% 的感染。此外，它们无法针对新出现的菌株提供保护，并且需要多次（2 或 3 次）剂量。人们正在寻求功效改进的第二代疫苗，而亚单位疫苗是一个有吸引力的选择。 CDC 估计，即使接种疫苗，每年仍有约 50 万人死于轮状病毒感染。 对人类免疫系统识别抗原和中和病原体的机制的全面了解有助于亚单位疫苗的有效开发。该应用将提供分子免疫学范式，可能影响抗原的选择、保护替代标记的使用以及新型轮状病毒疫苗的开发。我们将探索并确定表位转移的分子基础。