Non-invasive monitoring of cell-mediated rejection and bkv-associated urothelial cancer in kidney transplant recipients

Background Kidney transplantation is the treatment of choice for end-stage kidney disease, however in order to avoid rejection kidney transplant recipients (KTRs) are undergoing a lifelong immunosuppression increasing the risk of infection and cancer. While humoral immunity can be easily monitored through anti-HLA alloantibodies, non-invasive biomarkers to study the cellular immunity are lacking before and after transplant. Donor specific (d-sp) ELISPot and Panel-reactive T (PRT) cell before transplantation have been developed to detect alloreactive memory T cells, however no studies ever investigated the combination of these two techniques for estimating the risk of acute T-cell mediated rejection (TCMR). After transplantation, urinary CXCL9 can help diagnosing TCMR, however the current ELISA technique requires 24 hour for processing therefore is not feasible for clinical decision-making. Moreover, the response of CXCL9 to rejection treatment has not been investigated yet. Finally, recent studies suggested a potential role of BKV in the oncogenesis of urothelial cancer and in the context of BKV infection, conventional urinary cytology specificity for detecting neoplastic cells is jeopardized by the presence of atypical infected urothelium. Methods We performed a retrospective multicentric study on 168 KTRs to assess the role of pre-transplant d-sp ELISPot and PRT assays in predicting the risk of biopsy-proven acute rejection (BPAR), de novo donor-specific antibodies (DSA), and eGFR decline over a 48-month follow-up period. We further validated a new rapid Bio-Layer Interferometry (BLI)-based assay to measure urinary CXCL9 in <1 hour. The performance of this assay was retrospectively compared to the standard ELISA technique in 86 KTRs with various diagnoses. To assess utility in detecting adequacy of therapy we serially measured serum creatinine and urinary CXCL9 in 6 subjects after treatment for TCMR and correlated the results with histological and clinical response to rejection treatment. Finally, we conducted a retrospective single-center study on 147 KTRs to explore the association between BKV infection and urothelial cancer (UC) and the role of specific immunohistological stains on urinary cytology for the diagnosis of UC in the context of BKV infection. Results d-sp ELISPOT was independently associated with TCMR (adjusted OR: 4.20 [95%CI: 1.06 to 21.73; P=0.041]). Median PRT and PRT+IL15 were independently associated with higher eGFR decline at 48month post-transplantation. BLI accurately and reproducibly detected urinary CXCL9 in <1h for a non-invasive diagnosis of TCMR in KTRs. In samples obtained after treatment for TCMR, BLI CXCL9 measurements detected biopsy-proven intragraft infiltrates despite treatment-induced reduction in serum creatinine. Finally, patients with diagnosis of UC were more likely to have a BKV persistent infection with increased viral replication (higher plasmatic detection) Conclusions Pre-transplant T-cell immune-monitoring using d-sp ELISPOT and PRT assays identifies kidney transplant candidates at high risk of TCMR and worse kidney allograft progression. BLI-based urinary CXCL9 detection has potential as a point-of-care, noninvasive biomarker to diagnose and guide therapy for TCMR in kidney transplant recipients. BKV infection is associated with increased risk of UC. In the context of BKV infection, special immunohistochemical stains for p16 can increase the sensitivity and specificity of urinary cytology for the diagnosis of UC.