Identification of a peripheral blood transcriptional biomarker panel associated with operational renal allograft tolerance

Abstract

Long-term allograft survival generally requires lifelong immunosuppression (IS). Rarely, recipients display spontaneous ''operational tolerance'' with stable graft function in the absence of IS. The lack of biological markers of this phenomenon precludes identification of potentially tolerant patients in which IS could be tapered and hinders the development of new tolerance-inducing strategies. The objective of this study was to identify minimally invasive blood biomarkers for operational tolerance and use these biomarkers to determine the frequency of this state in immunosuppressed patients with stable graft function. Blood gene expression profiles from 75 renal-transplant patient cohorts (operational tolerance/acute and chronic rejection/stable graft function on IS) and 16 healthy individuals were analyzed. A subset of samples was used for microarray analysis where three-class comparison of the different groups of patients identified a ''tolerant footprint'' of 49 genes. These biomarkers were applied for prediction of operational tolerance by microarray and real-time PCR in independent test groups. Thirty-three of 49 genes correctly segregated tolerance and chronic rejection phenotypes with 99% and 86% specificity. The signature is shared with 1 of 12 and 5 of 10 stable patients on triple IS and low-dose steroid monotherapy, respectively. The gene signature suggests a pattern of reduced costimulatory signaling, immune quiescence, apoptosis, and memory T cell responses. This study identifies in the blood of kidney recipients a set of genes associated with operational tolerance that may have utility as a minimally invasive monitoring tool for guiding IS titration. Further validation of this tool for safe IS minimization in prospective clinical trials is warranted.kidney transplantation ͉ microarray ͉ tolerant ͉ genomics ͉ immunosuppression titration D espite continuous improvement in renal allograft survival over the last decade, the half-life of renal allografts has increased marginally because of accrual of chronic graft nephropathy from drug-related nephrotoxicity and chronic rejection (1, 2). Patients facing life-long immunosuppression (IS) have increased risk of infection and malignancy (3), whereas insufficient immunosuppressive drug exposure or interruption usually increases rejection risk (4). However, spontaneous and long-term graft acceptance is observed in a small number of patients after solid-organ transplantation (5, 6), years after total withdrawal of immunosuppressive drugs, confirming that a clinical operational state of tolerance to a mismatched graft, described as ''a state of quiescence of the transplanted organ, functioning without a destructive immune response'' (7), can indeed occur and exist in humans. However, the frequency of this observation in the kidney transplant population is unknown and, currently, we cannot identify patients primed to develop this immune adaptation or monitor for the stability of this status of ''operational tolerance.'' The operationally tolerant kidney transpla...

Fibrosis with Inflammation at One Year Predicts Transplant Functional Decline

“…Thus, in specific circumstances, the information provided by gene expression analyses may be used to enhance rather than replace that provided by graft pathology. Finally, in common with the work published by others in the field, 18,20,23,25,29,40,54,56 our TLDA and microarray analyses contribute to a growing publicly available databank of expression profiles from KTx recipients with diverse characteristics and provide a basis for ongoing mechanistic investigation of renal allograft injury and repair.…”

Biomarkers of Tolerance in Kidney Transplantation: Are We Predicting Tolerance or Response to Immunosuppressive Treatment?

“…A number of studies, including our own, have suggested gene expression signatures of tolerance in kidney transplantation 7, 8, 9, 11, 32 or have described differential expression of smaller gene sets 11, 33, 34. None had assessed the confounding effect of IS.…”

The Anti-Fibrotic Effect of Mycophenolic Acid–Induced Neutral Endopeptidase

“…22,[33][34][35] To investigate the possible biologic mechanisms underlying the clinical action of this immunosuppressive drug, we decided to apply an exploratory genomic analysis performed as an hypothesis-generating approach. The transcriptomic screening has been extensively used in transplantation to identify biomarkers for an early diagnosis of acute 36 and chronic rejection, 37 but presently, little is known about the change in the genomic profile induced by pharmacologic intervention in transplant recipients. Microarray analysis showed that 16 genes were modulated by the conversion from AZA to EC-MPS in the immunosuppressive regimen of our renal transplant population.…”