LATE BREAKING II

E. Perucha¹, P. Sagoo², B. Sawitzki³, S. Tomiuk⁴, D.A. Stephens⁵, S. Brouard⁶, I. Rebollo-mesa², R. Hilton⁷, K. Bourcier⁸, M. Goldman⁹, K.J. Wood¹⁰, K. Newell⁸, A. Warrens¹¹, U. Janssen⁴, H. Volk¹², J. Soulillou⁶, R.I. Lechler¹³, M.P. Hernandez-fuentes^14
1Nephrology And Transplantation, Kings College London, London/UNITED KINGDOM, ², Kings College London, London/UNITED KINGDOM, ³, Institute for Medical Immunology, Berlin/GERMANY, ⁴, Miltenyi GmbH, Bergisch Gladbach/GERMANY, ⁵, McGill University, Montreal/CANADA, ⁶U643, INSERM, Nantes cedex 1/FRANCE, ⁷, NIHR Biomedical Research Centre at Guy’s and St Thomas’ Hospital and King’s College London, London/UNITED KINGDOM, ⁸, Immune Tolerance Network, San Francisco/UNITED STATES OF AMERICA, ⁹, Universite Libre Bruxelles, Charleroi/BELGIUM, ¹⁰Transplantation Research Immunology Group, Nuffield Department of Surgery, University of Oxford, Oxford/UNITED KINGDOM, ¹¹Department Of Immunology, Imperial College London, London/UNITED KINGDOM, ¹², Berlin-Brandenburg Center for Regenerative Therapies (BCRT), Berlin/GERMANY, ¹³, King’s College London, London/UNITED KINGDOM, ¹⁴Nephrology And Transplantation, King's College London, London/UNITED KINGDOM

Body: Introduction: Identifying biomarkers that define transplant recipients in whom immunological tolerance is established or is developing have the potential to allow an individually tailored approach to the immunosuppressive treatment management in kidney transplant recipients. For this purpose, we have identified operationally tolerant renal transplant patients. These patients have been screened for several in vitro biomarkers and bioassays and the results have been compared to patients groups treated with different degree of immunosuppression and transplant status as well as healthy controls. Those assays that resulted on a highly predictive “tolerant” signature were interrogated in an independent test set cohort of patients with similar characteristics. Methods: The patients cohort, recruited by the “Indices of Tolerant” (IoT) network, consisted of 11 operationally tolerant drug-free (Tol-DF) patients that were functionally stable despite remaining immunosuppression-free for more than 1 year; 11 stable patients on minimal immunosuppression (s-LP); 30 stable patients maintained with calcineurin inhibitors (s-CNI); 10 stable patients maintained on CNI-free immunosuppression regimen (s-nCNI); 9 patients with biopsy proven and immunological driven chronic rejection (CR). Finally a set of 19 age and sex matched healthy volunteers were recruited as a control group (HC). An independent cohort of kidney transplant, including 24 operationally tolerant recipients, recruited by the Immune Tolerance Network (ITN), and with similar characteristics to the IoT cohort, were tested as a test set. Peripheral Blood Mononuclear cells immunophenotype, donor-specific response ELISpot, whole blood RT-PCR, Luminex allo-Ab detection and whole blood micro array techniques were performed in both patients’ cohorts. Results: When Tol-DF patients were compared to the rest of the groups, we detected an expansion of peripheral blood B and NK lymphocytes. Also, the percentage of activated CD4+ T cells was diminished. Tol-DF group had undetectable levels of serum donor-specific antibodies. Additionally, Tol-DF patients showed a significant donor-specific hyporesponsiveness of CD4+ T cells when compared to other groups, and a high ratio of forkhead box P3 to α-1,2-mannosidase gene expression. Finally, microarray analysis revealed a bias toward differential expression of B cell–related genes and their associated molecular pathways in tolerant recipients. When microarray and biomarkers were combined in ROC curves, as specificity and sensitivity for the training set was 1. The same analysis over the test set resulted on a peak specificity of 0.903 and sensitivity of 0.903. Conclusion: By combining these indices of tolerance as a cross-platform biomarker signature, we were able to identify tolerant recipients in both the training set and the test set. This study provides an immunological profile of the tolerant state that, with further validation, should inform and shape drug-weaning protocols in renal transplant recipients.

Disclosure: All authors have declared no conflicts of interest.