The effects of somatic HLA class I allele mutations on antigen presentation in acquired aplastic anemia

体细胞 HLA I 类等位基因突变对获得性再生障碍性贫血抗原呈递的影响

• 批准号: 10545024
• 负责人: Daria Babushok
• 金额: $ 8.13万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-01-01 至 2024-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10545024
• 关键词: Address; Affect; Alleles; Amino Acid Substitution; Amino Acids; Antigen Presentation; Aplastic Anemia; Autoantigens; Autoimmune; Autoimmunity; Award; Binding; Bone Marrow; Bone marrow failure; Cell Line; Cell surface; Cells; Cellular Assay; Characteristics; Complex; Data; Development; Disease; Endoplasmic Reticulum; Foundations; Future; HLA Antigens; Hematological Disease; Hematopoiesis; Hematopoietic; Hematopoietic stem cells; Histocompatibility Antigens Class I; Immune; Immunologics; Immunoprecipitation; Individual; Induced Mutation; Life; Loss of Heterozygosity; Mediating; Missense Mutation; Molecular; Mutate; Mutation; Outcome; Pathogenesis; Pathway interactions; Patient-Focused Outcomes; Patients; Peptides; Property; Proteins; Proteomics; Recurrence; Role; Somatic Mutation; Surface; Surface Antigens; T-Lymphocyte; Therapeutic immunosuppression; Work; antigen processing; autoimmune pathogenesis; candidate validation; cohort; cytopenia; effective therapy; mutant; peptide I; prevent; protein folding; protein structure; rational design; risk variant; tapasin; therapy design; therapy development

PROJECT SUMMARY The aim of this proposal is to explore the functional significance of somatic mutations in peptide-binding domains of Human Leukocyte Antigen (HLA) class I alleles in surviving hematopoietic cells of patients with acquired aplastic anemia (AA). AA is an autoimmune bone marrow aplasia that occurs in previously healthy individuals causing life-threatening cytopenias. Multiple lines of evidence, most notably the efficacy of T-cell directed immu- nosuppressive therapy in AA, implicate T lymphocytes in autoimmune destruction of hematopoietic stem and progenitor cells (HSPCs) in AA. Despite some progress, AA patients’ outcomes remain poor, and there is a critical need to develop more effective therapies for AA. The main barrier to progress has been the poor under- standing of specific mechanisms of autoimmunity in AA. Neither the antigenic target nor the causes of autoim- munity have been identified. Understanding the immune pathogenesis of AA is essential for developing therapies that can more effectively treat AA and prevent its complications. In previous studies of acquired mutations in AA, we identified recurrent mutations in HLA class I alleles in surviving hematopoietic cells of AA patients. The en- hanced survival of HLA class I-mutant cells underscored the critical role of HLA class I in mediating the autoim- mune recognition of HSPCs in AA. HLA alleles disrupted by somatic mutations are thought to be responsible for autoantigen presentation in the affected patients (function as “risk alleles”). Their somatic inactivation allows mutant HSPCs to evade the autoimmune attack. While 80% of the identified mutations led to the loss of mutant HLA alleles’ expression, 20% of mutations were predicted to form a functional HLA protein. Notably, eight muta- tions were amino acid changes located in the alpha (α)-1 and α-2 domains of the HLA peptide-binding pocket, which could be especially informative about residues critical for AA autoantigen binding. These data support our central hypothesis that autoimmune attack in AA is directed against AA autoantigen(s) presented by specific HLA class I alleles, and somatic HLA mutations can disrupt autoantigen presentation in AA by abrogating HLA risk allele expression or its autoantigen binding. To address our hypothesis, we will evaluate the functional con- sequences of mutations in peptide-binding domains of HLA alleles in AA patients in two integrated aims. Aim 1 will use cellular assays to determine the effects of HLA missense mutations on HLA processing and surface stability. Aim 2 will use proteomics to define the HLA class I immunopeptidome of cells expressing wild-type and mutant HLA alleles. Our results will define structural features of AA HLA risk alleles necessary for autoanti- gen binding, forming the foundation for future studies of candidate AA autoantigens. AA is a devastating disease, yet its underlying immunological mechanisms remain unknown. Our studies will fill this critical need, opening the door to future in-depth mechanistic studies and the future development of more effective, rationally-designed therapies for AA.

项目摘要 该建议的目的是探索肽结合域中体细胞突变的功能意义 人类白细胞抗原（HLA）I类等位基因存活的患者造血细胞 性贫血（AA）。 AA是一种自身免疫性骨髓性，发生在以前健康的个体中 引起威胁生命的细胞减少症。多种证据，最值得注意的是T细胞定向的效率 在AA中进行的抑制疗法，暗示T淋巴细胞在造血茎的自身免疫性破坏和 AA中的祖细胞（HSPC）。尽管有一些进展，但AA患者的结果仍然很差，并且有一个 为AA开发更有效的疗法的迫切需要。进步的主要障碍是较差 AA自身免疫的特定机制的站立。抗原靶标或自身的原因既不 已经确定了市政府。了解AA的免疫发病发生对于开发疗法至关重要 这可以更有效地治疗AA并防止其并发症。在先前关于AA中获得突变的研究中， 我们在AA患者的生存造血细胞中发现了HLA I类等位基因的复发突变。 en- HLA I类突变细胞的生存期强调了HLA I类在介导自动IM的关键作用 Mune在AA中对HSPC的认可。被认为是由躯体突变中断的HLA等位基因被认为是造成的 受影响的患者的自动抗原表现（充当“风险等位基因”）。他们的躯体失活允许 突变的HSPC逃避自身免疫攻击。而已确定的突变中有80％导致突变体的损失 HLA等位基因的表达，预计20％的突变形成了功能性HLA蛋白。值得注意的是，八个muta- Tions是位于HLA胡椒结合口袋的α（α）-1和α-2结构域中的氨基酸变化， 这对于AA自动抗原结合至关重要的残留物可能特别有用。这些数据支持我们 中心假设是，AA中的自身免疫性攻击针对特定的AA自动抗原（S） HLA I类等位基因和体细胞HLA突变可以通过废除HLA中的AA中破坏自动抗原呈现 风险等位基因表达或其自身抗原结合。为了解决我们的假设，我们将评估功能性概念 在两个综合目的中，AA患者中HLA等位基因的肽结合结构域突变序列。目标1 将使用细胞刺激来确定HLA错义突变对HLA处理和表面的影响 稳定。 AIM 2将使用蛋白质组学来定义表达野生型细胞的HLA I类免疫肽组 和突变的HLA等位基因。我们的结果将定义AA HLA风险等位基因的结构特征 Gen Binding，为候选AA自身抗原的未来研究构成基础。 AA是一种毁灭性疾病， 然而，其潜在的免疫机制仍然未知。我们的研究将满足这一关键需求，打开 通往未来的深入机械研究和更有效，合理设计的未来发展 AA的疗法。

项目成果

Severe aplastic anaemia after serial vaccinations for SARS-CoV-2, pneumococcus and seasonal influenza.

• DOI: 10.1002/jha2.443
• 发表时间: 2022-08
• 期刊: EJHaem
• 作者: Wang, Xiao;Laczko, Dorottya;Caponetti, Gabriel C;Rabatin, Susan;Babushok, Daria V
• 通讯作者: Babushok, Daria V