Hu Robert W, Korutla Laxminarayana, Reddy Sanjana, Harmon Joey, Zielinski Patrick D, Bueker Alex, Molina Maria, Romano Connie, Margulies Ken, McLean Rhondalyn, Lal Priti, Vallabhajosyula Prashanth
Department of Surgery, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA.
Division of Cardiology, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA.
Transplant Direct. 2020 Oct 19;6(11):e615. doi: 10.1097/TXD.0000000000001057. eCollection 2020 Nov.
Endomyocardial biopsy remains the gold standard for distinguishing types of immunologic injury-acute versus antibody-mediated rejection (AMR). Exosomes are tissue-specific extracellular microvesicles released by many cell types, including transplanted heart. Circulating transplant heart exosomes express donor-specific human leukocyte antigen (HLA) I molecules. As AMR is mediated by antibodies to donor HLAs, we proposed that complement deposition that occurs with AMR at tissue level would also occur on circulating donor heart exosomes.
Plasma exosomes in 4 patients were isolated by column chromatography and ultracentrifugation. Donor heart exosomes were purified using anti-donor HLA I antibody beads and complement C4d protein expression was assessed in this subset as marker for AMR.
Three patients had no rejection episodes. Circulating donor heart exosomes showed troponin protein and mRNA expression at all follow-up time points. One patient developed AMR on day 14 endomyocardial biopsy that was treated with rituximab, IVIG/plasmapheresis. Time-specific detection of C4d protein was seen in donor heart exosome subset in this patient, which resolved with treatment. C4d was not seen in other 3 patients' donor exosomes.
Anti-donor HLA I specificity enables characterization of circulating donor heart exosomes in the clinical setting. Further characterization may open the window to noninvasively diagnose rejection type, such as AMR.
心内膜心肌活检仍然是区分免疫损伤类型——急性与抗体介导性排斥反应（AMR）的金标准。外泌体是由包括移植心脏在内的多种细胞类型释放的组织特异性细胞外微囊泡。循环中的移植心脏外泌体表达供体特异性人类白细胞抗原（HLA）I类分子。由于AMR是由针对供体HLA的抗体介导的，我们推测在组织水平上与AMR相关的补体沉积也会发生在循环中的供体心脏外泌体上。
通过柱色谱法和超速离心法分离4例患者血浆中的外泌体。使用抗供体HLA I抗体磁珠纯化供体心脏外泌体，并评估该亚组中补体C4d蛋白的表达，作为AMR的标志物。
3例患者无排斥反应发作。在所有随访时间点，循环中的供体心脏外泌体均显示肌钙蛋白蛋白和mRNA表达。1例患者在第14天心内膜心肌活检时发生AMR，接受了利妥昔单抗、静脉注射免疫球蛋白/血浆置换治疗。在该患者的供体心脏外泌体亚组中检测到了时间特异性的C4d蛋白，治疗后消失。其他3例患者的供体外泌体中未检测到C4d。
抗供体HLA I特异性能够在临床环境中对循环中的供体心脏外泌体进行表征。进一步的表征可能为无创诊断排斥反应类型（如AMR）打开窗口。
