The Immunobiology of Factor VIII

摘要/摘要(项目2) 抗第VIII因子(FVIII)同种抗体(抑制物)可在血友病A患者中发展，限制 为这些患者提供治疗选择，并可能增加发病率和死亡率。与大多数免疫原不同 遇到宿主时，FVIII没有已知的激活宿主免疫的典型先天免疫配体。 尽管如此，近30%的患者在接触FVIII后会出现抑制剂。无法阻止抑制物 FVIII的形成在很大程度上源于对FVIII的关键特征缺乏根本的了解 负责接合并激活宿主免疫力。我们的长期目标是定义FVIII的主要特征 在随后的FVIII暴露之后启动并随后增强抑制剂的形成，以便减少或 防止抑制物的发展。我们的中心假设是FVIII上的关键多糖信号有助于初始宿主 对FVIII的识别和应答，随后形成抗FVIII的特异性抗体，进而影响 随后暴露于FVIII的免疫学结果。我们的假设是基于我们最近的 发现不同的FVIII产物不仅具有独特的多糖信号和不同的诱导能力 抑制剂，但不同的抗FVIII抗体对宿主免疫细胞的影响也不同 互动。因此，FVIII多糖和早期抗FVIII抗体可能代表着关键的早期调节因子 决定了FVIII暴露的最终免疫结果。因为独特的多糖结构可以不同地接合 不同的先天免疫受体，这些结果强烈表明个体FVIII糖型可能不同 影响寄主识别和抑制剂开发。此外，不同的抗FVIII抗体能够 不同的抗原提呈细胞对FVIII摄取的影响强烈表明 早期抗FVIII抗体的特异性可能影响随后暴露于FVIII的免疫学后果。 最后，由于某些FVIII产品上存在的非人类葡聚糖表位可以通过自然发生的 抗α半乳糖抗体、抗α半乳糖抗体(由不同的微生物群刺激)同样可以结合FVIII和影响 抑制剂形成的可能性。我们将使用生化分析和活体内的互补方法 通过测试以下特定目标来确定负责抑制剂形成的FVIII的关键特征的研究： 目的1：确定FVIII多糖在抑制物形成中的作用。目的2：确定抗FVIII抗体在FVIII上的作用 免疫复合体的形成和抑制物的开发。目标3：确定微生物区系对抗α半乳糖的影响 抗体的产生和随后的抑制物的形成。我们相信，这些目标的成功实现 不仅具有确定FVIII调节抑制剂形成的关键特征的能力，而且还可以 建立一个重要的框架，以开发旨在开发独特的FVIII产品的Rational方法 免疫原性降低。

Summary/Abstract (Project 2) Anti-factor VIII (fVIII) alloantibodies (inhibitors), which can develop in patients with hemophilia A, limit the therapeutic options for these patients, and can increase morbidity and mortality. Unlike most immunogens encountered by a host, fVIII possesses no canonical innate immune ligands known to activate host immunity. Despite this, nearly 30% of patients develop inhibitors following fVIII exposure. The inability to prevent inhibitor formation largely stems from a fundamental lack of understanding regarding key features of fVIII that are responsible for engaging and then activating host immunity. Our long-term goal is to define key features of fVIII that initiate and then enhance inhibitor formation following subsequent fVIII exposures, in order to reduce or prevent inhibitor development. Our central hypothesis is that key glycan signatures on fVIII facilitate initial host recognition and response to fVIII, followed by the formation of anti-fVIII specific antibodies that in turn impact the immunological outcome of subsequent fVIII exposures. Our hypothesis is formulated based on our recent discovery that different fVIII products not only possess unique glycan signatures and distinct abilities to induce inhibitors, but also that fVIII engagement by distinct anti-fVIII antibodies differentially impacts host immune cell interactions. Thus, fVIII glycans and early anti-fVIII antibodies may represent key early regulators that dictate the ultimate immune outcome of fVIII exposure. As unique glycan structures can differentially engage distinct innate immune receptors, these results strongly suggest that individual fVIII glycoforms may differentially impact host recognition and inhibitor development. Furthermore, the ability of distinct anti-fVIII antibodies to differentially impact fVIII uptake by antigen presenting cells strongly suggests that the nature and epitope specificity of early anti-fVIII antibodies likely shape the immunological consequence of subsequent fVIII exposure. Finally, as non-human glycan epitopes present on certain fVIII products can be recognized by naturally occurring anti-αGal antibodies, anti-αGal antibodies (stimulated by distinct microflora) may likewise bind fVIII and impact the likelihood of inhibitor formation. We will use a complementary approach of biochemical analyses and in vivo studies to define key features of fVIII responsible for inhibitor formation by testing the following specific aims: Aim 1: Define the role of fVIII glycans on inhibitor formation. Aim 2: Define the role of anti-fVIII antibodies on fVIII immune complex formation and inhibitor development. Aim 3: Define the impact of microbiota on anti-αGal antibody development and subsequent inhibitor formation. We believe that successful completion of these aims not only possesses the capacity to define key features of fVIII that regulate inhibitor formation, but may also establish an important framework to develop rational approaches designed to develop unique fVIII products with reduced immunogenicity.