*Purpose: To study the prevalence of BK viremia (BKV) and BK Virus Nephropathy (BKVN) utilizing plasma BK quantitative Polymerase Chain Reaction (qPCR) and report outcomes of treatment with reduction of immunosuppression and intravenous immunoglobulin (IVIG).

*Methods: A retrospective cross-sectional study of pediatric kidney transplants from January 2013 to January 2020. Excluded were age> 21 years at transplant and primary nonfunctioning allograft. Surveillance was conducted using plasma BK qPCR at 1,3,6,9,12,18,24 months and then annually. BKV was defined as ≥ 250 copies/ml, and BKV resolution as <250 copies/ml on consecutive blood draws at least two weeks apart. Persistent BKV was defined as ≥ 250 copies/ml at last follow up. Presumed BKVN was defined as persistent BKV ≥10,000 copies/ml despite immunosuppression reduction and elevated creatinine; confirmed BKVN if SV-40 stain was positive on biopsy. Chi-square, One-Way ANOVA, and Box-plot analysis was performed using SPSS 21.0.

*Results: Inclusion criteria was met by 56 children. Demographics: mean age at transplant was 11.8±5.6 years; 68% male; 55% African-American; 75% deceased-donor; 91% primary transplant. Mean follow up was 42.5±22.5 months. All patients received thymoglobulin induction and tacrolimus-prednisone-mycophenolate mofetil (MMF) maintenance regimen. Twenty (35.7%) of 56 had BKV, two (3.5%) presumed BKVN and two (3.5%) confirmed BKVN. A comparison of BKV vs. Non BKV group revealed that mean age at transplant, gender, race, primary diagnosis, type of donor, re-transplantation status, HLA matching, cold ischemia time, thymoglobulin dosing, duration of stent, acute rejection and mean duration of follow up were not statistically significant. Mean post-transplant time (months) to initial detection (5.5±4.5), peak (8.5±5), and resolution (15±7) of BKV was noted. Reduction in immunosuppression was the first line of therapy in 100% patients. At initial detection of BKV, tacrolimus trough level was reduced to target range in 8(40%) and below target range in 1(5%). For those within tacrolimus target range, 5 (25%) had < 50% reduction and 7(35%) had ≥50% reduction in MMF dose. Four patients with presumed/confirmed BKVN also received 6 doses of IVIG each. 14/20 (70%) had BKV resolution. Mean eGFR (ml/min/1.73m²) at the last follow up in BKV vs. Non-BKV group was 68.7±22 vs. 63.1±22.3; p=0.7, with 100% graft survival in both groups.

*Conclusions: Screening for BKV using qPCR, stepwise reduction in immunosuppression and use of IVIG resulted in resolution of BKV and preservation of renal allograft function.

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