Monitoring of molecular profiling of regulatory T cell biomarkers by using non- invasive strategies to predict outcome in renal transplantation

Abstract

Background. T-cell mediated acute rejection (aTCMR) is still an issue in kidney transplantation for it is associated with chronic rejection, graft loss, and overall worse outcomes. For these reasons, a standard non-invasive molecular tool to detect is desirable to offer a simpler monitoring of kidney transplant recipients (KTRs). The purpose of our study was to examine, in peripheral blood before and after transplantation, the expression patterns of regulatory T cell (Treg)-related genes: the forkhead box P3 (FOXP3) and the two CTLA-4 isoforms (full-length and soluble) to predict aTCMR onset, de novo donor-specific antibodies (DSA) development and renal dysfunction one year after transplantation. Methods. We profiled by using a relative quantification analysis (qRT-PCR 2-∆∆CT) the circulating mRNA levels of these biomarkers in peripheral blood of 89 KTRs within the first post-transplant year (at baseline and 15, 60, 365 days after transplantation and when possible at acute rejection) and compared the results with 24 healthy controls. Results. The three mRNA levels drastically reduced 15 days after transplantation and gradually recovered at one year in comparison with baseline, with very low levels by the time of aTCMR for FOXP3 (RQ=0.445, IQR=0.086-1.264, p=0.040). Healthy controls exhibited higher FOXP3 levels than patients at baseline (median RQ: 2.132, IQR=1.664-2.895 vs. p=0.005). Noteworthy, solCTLA-4 displayed a dual profile: on the one hand, at multivariate analysis solCTLA-4 transcripts at 15 days were associated with an increased risk of aTCMR over time (HR=3.905, 95%CI: 0.958-15.916, p=0.050), and graft dysfunction at one year (AOR=3.683, 95%CI=1.165-12.079, p=0.027); on the other hand, pre-transplant levels showed a protective association with de novo DSAs development (HR=0.189, 95%CI=0.078-0.459, p<0.001). Conclusions. Peripheral blood mRNA levels of Treg-associated molecules might help shape immunosuppression, tailor monitoring and achieve a better long-term clinical course of kidney transplantation in the wake of “precision medicine”. While the potential of these molecules as a therapeutic target needs further investigation, we found out preliminary evidence that solCTLA-4 can qualify as a candidate non-invasive biomarker of cellular and humoral alloreactivity in clinical transplantation.