Epitope masking reagents in transfusion medicine

描述(申请人提供)：需要长期输血的患者可能会产生如此多不同的RBC抗原同种异体抗体，以至于即使在全国范围内进行搜索，也无法识别出交叉匹配的RBC单位。当这种情况发生时，患者被迫放弃红细胞输注的治疗，在某些情况下，还可以挽救生命。因此，长期输血的患者，如那些患有镰状细胞病和其他慢性贫血的患者，由于针对多种血型抗原的同种免疫而遭受发病率和死亡率。目前，没有任何治疗干预措施可以绕过多重同种异体抗体的情况，并允许输注交叉配型不合的血液。然而，抗RBC抗体可以被修饰以保持其抗原结合活性，但失去溶血所需的活性，例如固定补体或与吞噬细胞上的Fc受体结合的能力。我们推测，这些修饰的抗体将掩盖有害的表位，从而阻止完整的免疫球蛋白对红细胞的溶血。因此，我们建议通过设计这种抗体来开发一种新的治疗方法，我们称之为表位掩蔽试剂(EMRS)。我们的中心假设是，EMRS的使用将通过掩盖导致溶血的抗体识别的表位来允许输注交叉配型不合的红细胞。为了使这种方法有一个详细的机制发展，我们创建了一个新的小鼠模型来研究交叉配型不合输血。利用该模型，我们可以1)获得供受体单一抗原差异的RBC，2)针对供体RBC上的血型抗原免疫小鼠，3)通过静脉途径输注包装好的、去白细胞的供体RBC，4)检测体内与输注RBC结合的抗体，5)监测输注RBC的溶血和循环寿命。我们建议使用这种交叉配型不合的输血模型作为平台来开发和测试EMRS的疗效。需要多次输血的患者会接触到许多献血者。因此，最终可能很难为他们找到相容的血液。在这种情况下，如果他们输入不相容的血液，他们就有发生输血反应的风险，但如果他们不输血，他们也会有风险。我们建议开发新的治疗方法，允许在这种情况下为患者输血不相容。

DESCRIPTION (provided by applicant): Patients whose illness requires chronic transfusions can develop so many different alloantibodies to RBC antigens that no crossmatch-compatible RBC units can be identified despite nationwide searches. When this occurs, patients are forced to forgo the therapeutic, and, in some cases, lifesaving benefits of RBC transfusion. Thus, chronically transfused patients, such as those with sickle cell disease and other chronic anemias, suffer morbidity and mortality from alloimmunization against multiple blood group antigens. Currently, no therapeutic interventions can circumvent the situation of multiple alloantibodies and allow for transfusion of crossmatch-incompatible blood. However, anti-RBC antibodies can be modified to maintain their antigen binding activity but lose activities required for hemolysis, such as the ability to fix complement or bind to Fc Receptors on phagocytes. We hypothesize that these modified antibodies will mask the offending epitopes, thereby blocking RBC hemolysis by intact IgG. Thus, we propose to develop a novel therapeutic approach by engineering such antibodies, which we refer to as epitope masking reagents (EMRs). Our central hypothesis is that the use of EMRs will allow transfusion of crossmatch- incompatible RBC by masking epitopes recognized by antibodies responsible for hemolysis. To allow for a detailed mechanistic development of this approach, we created a novel murine model for studying crossmatch-incompatible transfusions. Using this model, we can 1) obtain RBC with a single antigenic difference between donor and recipient mice, 2) immunize mice to the blood group antigen on the donor RBC, 3) transfuse packed, leukoreduced, donor RBC by an intravenous route, 4) detect in vivo antibody binding to transfused RBC, and 5) monitor hemolysis and circulatory lifespan of transfused RBC. We propose to use this model of crossmatch-incompatible transfusion as a platform to develop and test the efficacy of EMRs. Patients requiring many blood transfusions are exposed to many blood donors. Therefore, it may eventually become difficult to find compatible blood for them. In this case, they are at risk for a transfusion reaction if they are transfused with incompatible blood, but are also at risk if they are not transfused. We propose to develop novel therapies that would allow transfusions of incompatible blood to patients in this setting.