Kinetics of Red Blood Cell Clearance in Chronically Transfused Children with Sickle Cell Disease

项目摘要 镰状细胞病(SCD)由于红细胞(RBC)镰状和 溶血。中风是SCD最具破坏性的后遗症之一。慢性输血疗法(CTT)减少 中风风险通过(1)向循环供应正常的非镰刀状红细胞，从而降低 循环中的内源性镰状红细胞，以及(2)维持较高的血红蛋白(Hb)，从而抑制 新镰状红细胞的红细胞生成。虽然CTT在预防中风方面的有效性是公认的，但几乎 尽管有CTT，45%的儿童仍有静止性或显性中风。CTT在预防中风方面的失败 这些事件可能与循环镰状红细胞和红细胞生成减少不足有关。金额的多少 循环中的镰状红细胞与输血红细胞和内源性镰状红细胞的存活动力学有关。在……里面 对SCD患者的CTT进行了大规模的纵向分析，我们发现供者红细胞的存活率在以下方面存在很大差异 输血，清除更快与患者的免疫特征(历史红细胞同种异体免疫)有关 和脾存在)和供者红细胞葡萄糖-6-磷酸脱氢酶(G6PD)缺乏。为了更好地 了解患者和供者因素在输血红细胞存活和清除中的作用，我们建议 一项在SCD患者慢性输血发作期间进行的机械性临床试验，其中一小部分等量的 每个输血单位都被标记了与红细胞表面蛋白结合的生物素，以安全地识别和测量 供者红细胞在体内的存活。目标1将检查接受者免疫系统的关系(过去 同种异体免疫、脾体积和网状内皮系统功能标志物)在输血后 生物素标记供体红细胞的存活。目的2将研究供者红细胞G6PD水平和 供体红细胞代谢组学与体内存活及供体红细胞衰老标志物的变化。 这些目标的完成将增加我们对红细胞存活率变化机制的理解 在CTT期间，确定导致红细胞存活率下降的供者和受者的危险因素。归根结底，这种知识 将通知CTT管理层，以提高SCD中中风的预防。申请人余博士是一名 儿科血液学家和SCD的新兴临床研究人员，拥有临床研究硕士学位 以及SCD中以患者为中心的先导性和前瞻性研究的经验。易博士已经确认 一支出色的指导团队，在红细胞存活研究和生物素化方面具有专业知识，捐赠者红细胞 代谢组学和SCD的临床研究。应聘者在这份K23申请中的短期职业目标 1)发展输血医学的正式专业知识；2)扩大进行前瞻性研究的专业知识， 儿童SCD和输血医学的介入临床研究；3)学习使用和解释 生物素化红细胞输注以研究体内输血存活。候选人的长期职业目标 是通过一种个性化的儿童输血方法来改进输血和细胞治疗 和成人SCD，并改善输血和其他SCD治疗的临床结果，同时 减少毒性和不良事件。

Project Summary Sickle cell disease (SCD) carries significant morbidity as a result of red blood cell (RBC) sickling and hemolysis. Stroke is one of the most devastating sequelae of SCD. Chronic transfusion therapy (CTT) reduces stroke risk by (1) supplying normal, non-sickle RBC to circulation, thereby reducing the percentage of endogenous sickle RBC in circulation, and (2) maintaining a higher hemoglobin (Hb), thereby suppressing erythropoiesis of new sickle RBC. While the efficacy of CTT in stroke prophylaxis is well-established, nearly 45% of children continue to have silent or overt strokes despite CTT. The failure of CTT to prevent stroke events may be related to inadequate reduction of circulating sickle RBC and erythropoiesis. The amount of circulating sickle-RBC is related to the survival kinetics of both transfused RBC and endogenous sickle RBC. In a large, longitudinal analysis of CTT in SCD, we found wide variation in the survival of donor RBC following transfusion, with faster clearance associated with patient immune features (historical RBC alloimmunization and spleen presence) and with donor RBC glucose-6-phosphate-dehydrogenase (G6PD) deficiency. To better understand the roles of patient and donor factors in the survival and clearance of transfused RBC, we propose a mechanistic, clinical trial during chronic transfusion episodes in patients with SCD, in which a small aliquot of each transfused unit is labeled with biotin conjugated to RBC surface proteins, to safely identify and measure the in vivo survival of donor RBC. Aim 1 will examine the relationships of the recipient’s immune system (past alloimmunization, splenic volume, and markers of reticuloendothelial system function) on the post-transfusion survival of biotin-labeled donor RBC. Aim 2 will examine the relationships of donor RBC G6PD levels and donor RBC metabolomics with the in vivo survival and changes in donor RBC senescence markers. Completion of these aims will increase our understanding of mechanisms for the variability in RBC survival during CTT, identifying donor and recipient risk factors for decreased RBC survival. Ultimately this knowledge will inform the management of CTT to improve the prevention of strokes in SCD. The applicant, Dr. Yee, is a pediatric hematologist and an emerging clinical researcher in SCD, with a master’s degree in clinical research and experience with pilot and prospective studies of patient-oriented research in SCD. Dr. Yee has identified an exceptional mentorship team with expertise in RBC survival studies and biotinylation, donor RBC metabolomics, and clinical research in SCD. The candidate's short-term career goals for this K23 application are to 1) Develop formal expertise in transfusion medicine; 2) Expand expertise in conducting prospective, interventional clinical research in pediatric SCD and transfusion medicine; 3) Learn the use and interpretation of biotinylation of RBC transfusion to study transfusion survival in vivo. The candidate's long-term career goals are to improve transfusion and cellular therapies with a personalized approach to blood transfusion in children and adults with SCD and to improve the clinical outcomes of transfusion and other SCD therapies while decreasing toxicity and adverse events.