Clinical and Immunological Characteristics for BK Polyomavirus- associated Nephropathy after Kidney Transplantation

Background: BK polyomavirus (BKPyV)-associated nephropathy (BKPyVAN) could cause allograft dysfunction among kidney transplant (KT) recipients. Intact BKPyV-specific immunity is correlated with viral containment, therefore clinical and immunological characteristics related to BKVAN after KT needs to be explored. Methods We prospectively investigated an association between clinical baseline characteristics, BK polyomavirus (BKPyV)-specific immunity, and BKPyV-associated nephropathy (BKPyVAN) in KT recipients. BKPyV-specific immunity, measured with intracellular cytokine assays, is reported as the percentage of IFN-γ-producing CD4+ T, CD8+ T, natural killer (NK), and NKT cells after large-T antigen and viral capsid protein 1 (VP1) stimulation. Results Among 100 KT patients, BKPyVAN occurred in 18% within one-year post-KT. There were 70 patients (70%) who received an induction immunosuppressive therapy. Diabetic nephropathy was significantly associated with BKPyVAN. Among 40 patients who were eligible for the immunological study. In a multivariate analysis, pre-KT %VP1-specific NK cells were independently associated with BKPyVAN (HR, 1.209; 95%CI, 1.055–1.386; P = 0.006). In those with BKPyVAN, the mean %NK (coefficient, 1.202; 95%CI, 0.033–2.371; P = 0.04), %VP1-specific NK (coefficient, 2.602; 95%CI, 1.083–4.121; P = 0.001), and %NKT (coefficient, 0.199; 95%CI, 0.051–0.348; P = 0.008) cells at 1-month post-KT were significantly higher than those pre-KT. Thus, increasing NK, VP1-specific NK, and NKT cell proportions were observed among KT recipients who developed BKPyVAN within the first year. Conclusion KT recipients with underlying diabetes and the presence of BKPyV-specific NK- and NKT-cell immunity could be at risk of BKPyVAN after KT. BKPyV-specific innate immune monitoring could potentially stratify those at risk of BKPyVAN among KT recipients. (Thai Clinical Trials Registry, TCTR20190404004)