#3045 Understanding BK polyomavirus: surveillance and clearance in kidney transplant recipients

Abstract

Abstract Background and Aims BK virus allograft nephropathy (BKVN) can develop graft loss. The aim of this study was to describe BK viraemia and BKVN related factors, our experience in treatment and the impact in graft survival. Method We introduce a retrospective cohort of 78 kidney transplant recipients (KTRs) with BKV viraemia between January 2013 from January 2020 and with follow-up until December 31, 2022 in our center. Results Thirty-four (43%) were living donor KTRs, 30 (38.5%) DBD, 11 (14.1%) DCD III, and 2 (4.3%) DCD II. Twenty-seven (34.6%) of recipients were sensitized. Immunosuppressive induction was based on Anti-CD25 in 33 (42.3%), and antilymphocytes antibodies in 44 (56.4%). Basal treatment was TAC+MPA+PDN in 44 (56.4%) and TAC+iMTOR+PDN in 31 (39.7%). Median FK levels were 7.9 (ng/ml) in the first replication. Median BK load at first replication was 3636 [1030-97151]cp/ml. Median time to replication from transplant was 6 months, and from highest load 9 months. Immunosuppression adjustment after replication was switch to imTOR+FK 25 (32.1%), low FK 17 (21.8%), imTOR 4 (5.1%). Only surveillance was chosen in 27 (35.9%). Others therapies were Leflunomide 4 (5.1%), IVIG 6 (7.7%) or both 3 (3.8%). Photopheresis was used in 2 cases. Viraemia was cleared in 17/24 (70.8%) of the cases in which conversion to mTOR was performed as an immunosuppression adjustment strategy, versus 9 (56.3%) in which it was decided to lower FK and in 3 (75%) with low MMF. Ten cases in which surveillance was carried out became negative for viremia, possibly because they were patients with a lower replicative load. BKN occurred in 28/78 (36%) cases, interstitial fibrosis (ci>2) was found in 14/28 (48.27%). Graft rejection after BKN was developed in 11/28 (37.9%). Graft loss occurred in 26/78 (33.3%) of cohort and in 19 (65%)of patients with BKN, reaching a significant value. Viraemia clearance was reached in 41 (60.3%) in mean time of 10 months [4-27]. Mean time since BKVN until graft loss was 22.3 months [10.2-34.2]. Exitus occurred in 7/78 (9%) of replication cases and in 3/28 (10.7%)of BKN patients. Maximum BK load Exp β; [1-1], p 0.033, first replication load >10.000 (cp/ml) and deceased donor status (Exp β; 6,9 [2.43-19.57] and 2.98 [1.10-8.07] p 0.031, were related to BKVN in bivariate analysis. No significant differences were found between therapy in BKVN and graft loss, maybe due to low BKVN cases. Conclusion In our cohort, maximum BK load, first replication load >10,000 (cp/ml), and deceased donor status appear to be related to nephropathy. No significant differences were found between induction, basal or adjuvant therapy and graft loss. The current challenge is to stop replication before fibrosis, without increasing the risk of rejection.