Incidence and outcomes of BK virus allograft nephropathy among ABO- and HLA-incompatible kidney transplant recipients.

BACKGROUND AND OBJECTIVES ABO-incompatible kidney transplant recipients may have a higher incidence of BK virus allograft nephropathy (BKVAN) compared with ABO-compatible recipients. It is unclear whether HLA-incompatible recipients share this risk or whether this phenomenon is unique to ABO-incompatible recipients. DESIGN, SETTING, PARTICIPATION, MEASUREMENTS: This study analyzed adult incompatible kidney transplant recipients from 1998 to 2010 (62 ABO-incompatible and 221 HLA-incompatible) and identified patients in whom BKVAN was diagnosed by biopsy (per protocol or for cause). This was a retrospective analysis of a prospectively maintained database that compared BKVAN incidence and outcomes between ABO- and HLA-incompatible recipients, respectively. BKVAN link to rejection and graft accommodation phenotype were also explored. The Johns Hopkins Institutional Review Board approved this study. RESULTS Risk for BKVAN was greater among ABO-incompatible than HLA-incompatible patients (17.7% versus 5.9%; P=0.008). Of BKVAN cases, 42% were subclinical, diagnosed by protocol biopsy. ABO-incompatibility and age were independent predictors for BKVAN on logistic regression. C4d deposition without histologic features of glomerulitis and capillaritis (graft accommodation-like phenotype) on 1-year biopsies of ABO-incompatible patients with and without BKVAN was 40% and 75.8%, respectively (P=0.04). Death-censored graft survival (91%) and serum creatinine level among surviving kidneys (1.8 mg/dl) were identical in ABO- and HLA-incompatible patients with BKVAN (median, 1399 and 1017 days after transplantation, respectively). CONCLUSIONS ABO-incompatible kidney recipients are at greater risk for BKVAN than HLA-incompatible kidney recipients. ABO-incompatible recipients not showing the typical graft accommodation-like phenotype may be at heightened risk for BKVAN, but this observation requires replication among other groups.