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）镰状化而具有显著的发病率， 溶血中风是SCD最具破坏性的后遗症之一。慢性输血治疗（CTT）减少 中风的风险（1）提供正常的，非镰状红细胞循环，从而减少百分比 循环中的内源性镰状红细胞，和（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在预防卒中方面的有效性已经得到了很好的证实，但几乎 45%的儿童在接受CTT治疗后仍有隐性或显性中风。CTT预防中风的失败 事件可能与循环镰状红细胞和红细胞生成减少不足有关。的量 循环镰状红细胞与输注红细胞和内源性镰状红细胞的存活动力学有关。在 通过对SCD中CTT的一项大型纵向分析，我们发现， 输血，与患者免疫特征相关的更快清除（历史RBC同种免疫 和脾脏存在）和供体RBC葡萄糖-6-磷酸脱氢酶（G6PD）缺乏。更好地 为了了解患者和供体因素在输注红细胞的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制性临床试验， 每个输血单位都用与RBC表面蛋白结合的生物素标记，以安全地识别和测量 供体RBC的体内存活率。目标1将检查受体免疫系统的关系（过去 同种异体免疫、脾体积和网状内皮系统功能标志物） 生物素标记供体RBC的存活率。目的2将研究供体RBC G6PD水平与 供体RBC代谢组学与体内存活和供体RBC衰老标记物的变化。 这些目标的完成将增加我们对红细胞存活率变异机制的理解 在CTT期间，确定供者和受者RBC存活率降低的风险因素。最终，这些知识 将通知CTT的管理层，以改善SCD中卒中的预防。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 和经验的试点和前瞻性研究的患者为导向的研究在SCD。余博士已经确认 一个卓越的导师团队，在RBC存活研究和生物素化方面具有专业知识， 代谢组学和SCD的临床研究。K23申请人的短期职业目标 是1）发展输血医学的正式专业知识; 2）扩大进行前瞻性， 儿科SCD和输血医学的介入性临床研究; 3）学习使用和解释 红细胞输注的生物素化，以研究体内输血存活率。候选人的长期职业目标 是通过个性化的儿童输血方法来改善输血和细胞疗法 和成人SCD，并改善输血和其他SCD治疗的临床结局， 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.