Mechanisms of Immunogenicity of Factor VIII

因子 VIII 的免疫原性机制

• 批准号: 8265980
• 负责人: Shannon L. Meeks
• 金额: $ 12.83万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-15 至 2015-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8265980
• 关键词: A Mouse; A-factor (Streptomyces); Address; Adoptive Transfer; Affect; Agonist; Antibodies; Antibody Formation; Antigen-Presenting Cells; Antigens; Area; B-domain-deleted factor VIII; Biological; Biological Models; Blood coagulation; Bypass; CD4 Positive T Lymphocytes; Carrier Proteins; Coagulation Process; Complication; Conflict (Psychology); Development; Economic Burden; Event; Exposure to; Factor VIII; Frequencies; Future; Generations; Genes; Grant; Hemophilia A; Hemorrhage; Human; Imagery; Immune response; Immune system; Immunity; Immunization; Immunologics; Inflammation; Infusion procedures; Intravenous; Intravenous infusion procedures; Lead; Life; Limb structure; Lipopolysaccharides; Lymphatic; Mentorship; Modeling; Morbidity - disease rate; Mus; Mutation; Operative Surgical Procedures; Ovalbumin; Patients; Phenotype; Physiological; Poly I-C; Population; Proteins; Quality of life; Reagent; Receptor Activation; Regulation; Regulatory T-Lymphocyte; Research; Research Personnel; Risk; Rodent; Role; Signal Transduction; Site; Specificity; Structure; T cell response; T-Cell Activation; T-Lymphocyte Epitopes; Technology; Testing; Therapeutic; Thrombin; Time; Time Factors; Toll-like receptors; Training; Transgenic Mice; Treatment Cost; alternative treatment; antibody inhibitor; cytokine; design; human F8 protein; immune self tolerance; immunogenic; immunogenicity; in vivo; inhibitor/antagonist; insight; intravenous injection; memory CD4 T lymphocyte; non-genetic; novel; programs; public health relevance; recombinant antihemophilic factor VIII; research study; response; tool; trafficking; von Willebrand Factor

DESCRIPTION (provided by applicant): Inhibitory antibodies to factor VIII (fVIII) develop in approximately 30% of patients with severe hemophilia A in response to infusions of fVIII. Inhibitor development is associated with a lower quality of life and an increased economic burden and is currently is considered the most significant complication of the management of hemophilia A. Additionally, factor VIII inhibitors can occur in nonhemophiliacs, i.e. acquired hemophilia A, in which there can be life and limb- threatening complications. Patients with severe hemophilia A have no circulating fVIII protein and thus normal recognition of fVIII as "self" does not develop. Accordingly, the therapeutic replacement fVIII protein is seen as "foreign" by the immune system. Given that fVIII is an immunologically foreign protein, it may not seem surprising that an antibody response to fVIII would occur. However, in both rodents and humans, intravenous injection of soluble proteins usually fails to induce immunity and often induces a tolerogenic state. For this reason, the substantial immunogenicity of fVIII is unexpected. The central question of this grant is why, and by what mechanism, does fVIII induce an immune response. There are 3 Specific Aims in this proposal. In Aim 1, the role of the physiological site of fVIII presentation to the immune system, i.e. a site of inflammation where a clot is forming and where fVIII is released from its large carrier protein von Willebrand factor, will be characterized by comparing the immunogenicity of fVIII with an inactive form of fVIII in a murine hemophilia A immunogenicity model. In Aim 2, a novel fVIII molecule (HOVA) will be constructed that has a well characterized T cell epitope of ovalbumin inserted into the B domain. A wide array of immunologic reagents specific for this T cell epitope, including tetramer reagents and TCR transgenic mice, are available to investigate the mechanism of CD4+ T cell response to intravenous infusion of HOVA. There is evidence that early exposure to fVIII at the time of a "danger signal" such as surgery or a major bleed increases the risk of antibody development. In Aim 3 the role of toll like receptor activation on fVIII immunity will be addressed by comparing the CD4+ T cell response to intravenous infusion of HOVA as well as the ultimate antibody production in the presence and absence of toll like receptor agonists. The results of these experiments will allow for a deeper understanding of the substantial immunogenicity of fVIII and might provide insights for future design of novel fVIII molecules with decreased immunogenicity. This research plan along with the formal coursework and structured mentorship laid out in this proposal should provide the candidate with the training necessary to establish her as an independent investigator. PUBLIC HEALTH RELEVANCE: Patients with hemophilia A have a deficiency in the blood coagulation protein factor VIII. Some patients with hemophilia A develop antibodies to factor VIII that worsens their bleeding problems and makes therapy difficult and expensive. In this project, we will develop a better understanding of the immune response to the factor VIII protein, which may lead to better treatment alternatives.

描述（由申请人提供）：大约 30% 的严重 A 型血友病患者在输注 fVIII 后会产生针对因子 VIII (fVIII) 的抑制性抗体。抑制剂的产生与生活质量降低和经济负担增加有关，目前被认为是甲型血友病治疗中最显着的并发症。此外，因子 VIII 抑制剂可能出现在非血友病患者中，即获得性甲型血友病，其中可能会出现危及生命和肢体的并发症。患有严重 A 型血友病的患者没有循环中的 fVIII 蛋白，因此不会形成对 fVIII 作为“自身”的正常识别。因此，治疗性替代fVIII蛋白被免疫系统视为“外来的”。鉴于 fVIII 是一种免疫学外来蛋白，因此出现针对 fVIII 的抗体反应似乎并不奇怪。然而，在啮齿动物和人类中，静脉注射可溶性蛋白质通常不能诱导免疫，并且常常诱导耐受状态。因此，fVIII 的显着免疫原性是出乎意料的。这项资助的核心问题是 fVIII 为什么以及通过什么机制诱导免疫反应。该提案有 3 个具体目标。在目标 1 中，将通过在小鼠血友病 A 免疫原性模型中比较 fVIII 与非活性形式的 fVIII 的免疫原性来表征 fVIII 呈递给免疫系统的生理位点（即形成凝块以及 fVIII 从其大载体蛋白冯维勒布兰德因子中释放的炎症位点）的作用。在目标 2 中，将构建一种新型 fVIII 分子 (HOVA)，其具有插入 B 结构域的卵清蛋白的明确特征 T 细胞表位。一系列针对该 T 细胞表位的特异性免疫试剂，包括四聚体试剂和 TCR 转基因小鼠，可用于研究 CD4+ T 细胞对静脉输注 HOVA 的反应机制。有证据表明，在手术或大出血等“危险信号”出现时过早接触 fVIII 会增加产生抗体的风险。在目标 3 中，将通过比较 CD4+ T 细胞对静脉输注 HOVA 的反应以及存在和不存在 Toll 样受体激动剂时最终抗体的产生来探讨 Toll 样受体激活对 fVIII 免疫的作用。这些实验的结果将有助于更深入地了解 fVIII 的实质性免疫原性，并可能为未来设计免疫原性降低的新型 fVIII 分子提供见解。该研究计划以及本提案中规定的正式课程和结构化指导应该为候选人提供必要的培训，使她成为一名独立调查员。 公众健康相关性：甲型血友病患者缺乏凝血蛋白因子 VIII。一些 A 型血友病患者会产生针对 VIII 因子的抗体，这会使他们的出血问题恶化，并使治疗变得困难且昂贵。在这个项目中，我们将更好地了解对因子 VIII 蛋白的免疫反应，这可能会带来更好的治疗替代方案。