Bioencapsulated Factor IX for Oral Tolerance in Hemophilia B

描述（由申请人提供）：血友病是由编码凝血因子VIII（血友病A）或因子IX（血友病B）的基因突变引起的x连锁出血疾病。目前的治疗方法是静脉输注血浆源凝血因子或重组凝血因子浓缩物。最近，基因治疗取得了实质性进展。治疗性凝血因子的抑制性抗体（“抑制剂”）的形成是治疗的严重并发症。通过目前的免疫耐受诱导方案消除抑制剂是昂贵的，并不总是有效的，并且对抗因子IX （f.x IX）的抗体不太成功。目前尚无防止抑制剂形成的预防性方案。由于抑制剂的形成依赖于T帮助，CD4+ T细胞代表了耐受诱导的另一种靶标。已知特定的抗原给药途径如粘膜（口服或鼻腔）可诱导调节性T细胞和T细胞耐受性。这一建议是基于这样的假设，即粘膜抗原给药或粘膜和全身抗原联合递送可以阻止抑制剂的形成。为了开发一种有效、经济、临床适用的口服耐受性方案，我们将在叶绿体中产生表达高水平人类F.IX （hF.IX）的转基因植物。Bio-encapsulated高频。IX将被喂给小鼠，以测试其对hF抗体形成的预防作用。反复静脉注射hF。第九蛋白质。因为这种方法是基于对hF特异性CD4+ T细胞的抗原呈递。ix衍生肽表位，口服给药hF的生物活性。不需要IX。将评估优化后的方案对具有较大fix基因缺失的B型血友病小鼠的耐受性诱导。一种已知经常形成hF抑制剂的小鼠。这些研究选择IX。我们假设调节性T细胞的最佳激活是在植物源性hF出现后。IX抗原将导致能够在不形成抑制剂的情况下为血友病B提供基于蛋白质或基因的治疗。该方案还将应用于由于先前的蛋白质治疗而存在抑制剂的动物，以研究消除抑制剂的能力。在未来的研究中，将进一步优化口服耐受性方案，使其适应于预防血友病A治疗中因子VIII抑制剂的使用。

DESCRIPTION (provided by applicant): Hemophilia is the X-linked bleeding disorder caused by mutations in the gene encoding blood coagulation factor VIII (hemophilia A) or factor IX (hemophilia B). Current treatment is based on intravenous infusion of plasma-derived or recombinant clotting factor concentrates. More recently, substantial progress toward gene therapy has been made. Formation of inhibitory antibodies ("inhibitors") to the therapeutic clotting factor represents a serious complication of treatment. Elimination of inhibitors by current immune tolerance induction protocols is expensive, not always effective, and less successful for antibodies against factor IX (F.IX). No prophylactic protocols to prevent inhibitor formation are available. Since inhibitor formation is dependent on T help, CD4+ T cells represent an alternative target for tolerance induction. Specific routes of antigen administration such as mucosal (oral or nasal) are known to induce regulatory T cells and T cell tolerance. This proposal is based on the hypothesis that mucosal antigen administration or a combination of mucosal and systemic antigen delivery can prevent inhibitor formation. In order to develop an effective, cost- efficient, and clinically applicable oral tolerance protocol, we will generate transgenic plants expressing high levels of human F.IX (hF.IX) in the chloroplast. Bio-encapsulated hF.IX will be fed to mice to test for prevention of antibody formation to hF.IX upon repeated intravenous injected of hF.IX protein. Because this approach is based on antigen presentation to CD4+ T cells specific for hF.IX-derived peptide epitopes, biological activity of orally delivered hF.IX is not required. An optimized protocol will be evaluated for tolerance induction in hemophilia B mice with a large F.IX gene deletion. A strain of mice known to frequently form inhibitors to hF.IX is chosen for these studies. We hypothesize that optimal activation of regulatory T cells following presentation of plant-derived hF.IX antigen will result in the ability to provide protein- or gene-based therapy for hemophilia B without inhibitor formation. The protocol will also be applied to animals with pre-existing inhibitors due to prior protein therapy in order to investigate the ability to eliminate inhibitors. In future studies, the oral tolerance protocol will be further optimized and adapted to prevention of inhibitors to factor VIII in treatment of hemophilia A.