Circulating Donor Heart Exosome Profiling Enables Noninvasive Detection of Antibody-mediated Rejection

Abstract

Background. 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. Methods. 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. Results. 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. Conclusions. 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.

Evaluation of Colon-Specific Plasma Nanovesicles as New Markers of Colorectal Cancer

“…The analysis of tissue-specific ENVs has been explored as a method for noninvasively monitoring the acute rejection of transplants [52,53]. To the best of our knowledge, this is the first study on the exploration of tissue-specific ENVs as a disease marker.…”

Molecular Diagnosis of Rejection in Heart Transplantation

“…Detection of antibodies directed against donor HLAs using exosomes may be a sensitive way of noninvasively evaluating AMR. 38 One particular miRNA of interest is mi-182, which is increased with T-cell expression, including in the setting of ACR, and is downregulated in the setting of calcineurin inhibitor use. 34 mi-182 has been found in the plasma of mice during ACR, making it of interest as a potential noninvasive marker of acute rejection.…”

Low-dose IL-2 prevents murine chronic cardiac allograft rejection: Role for IL-2-induced T regulatory cells and exosomes with PD-L1 and CD73

“…BALB/c to C57BL/6 HTx rejected the transplanted heart with a median (range) survival time of 9 (7-10) days. Mice that received costimulatory blockade after HTx developed chronic rejection with a median (range) survival of 42 (31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)…”

“…29,30 Circulating exosomes have been proposed as a novel, noninvasive biomarker of cardiac allograft rejection in both animal models and humans. [31][32][33] After organ transplantation, the passenger leukocytes and/or parenchymal cells in the allograft release vast amounts of small extracellular vesicles, including exosomes that can present host antigen-presenting cells resulting in alloreactivity 34 or tolerization. 35,36 Immunoregulatory molecules, PD-L1 and CD73, in exosomes have been shown to suppress T cell function and can induce T cell anergy leading to tolerance.…”