Impact of BK Polyomavirus Plasma Viral Load in Kidney Transplant Outcomes

BK polyomavirus infection (BKVi) is an important cause of kidney transplant (KT) loss, but there is scarce evidence on the impact of BK plasma viral load on graft function and long-term KT survival.

A retrospective cohort study including all KT recipients with BKVi (BK viremia identified in ≥3 consecutive samples by polymerase chain reaction) in our center from January 2010 to December 2020 was performed. A case-control study (1:2) was performed. We grouped the cases according to their highest peak viral load: low-level viremia (<10,000 copies/mL) and high-level viremia (≥10,000 copies/mL). To identify risk factors for BKVi, a logistic regression analysis was achieved, and a multivariable Cox regression was used to describe risk factors for graft loss.

A total of 849 KTs were performed, and 67 presented BKVi (low-level viremia, n = 35 and high-level viremia, n = 26). In logistic regression analysis male sex (odds ratio [OR], 4.226; 95% CI, 1.660-10.758, P = .002), age (OR, 1.047; 95% CI, 1.008-1.088; P = .018), and retransplant (OR, 4.162; 95% CI, 1.018-17.015; P = .047) were predictors of BKVi. Acute rejection was more frequent in the BKVi group (18% vs 4.9%, P = .004), and graft survival was lower in patients with BKVi and high-level viremia (P = .027). In Cox regression analysis, BKVi (hazard ratio, 3.657; 95% CI, 1.146-11.670; P = .029) and specific BKV (BK polyomavirus) high-level viremia (hazard ratio, 1.988; 95% CI, 1.012-3.907; P = .046) were predictors of shorter graft survival.

BKV high-level viremia was associated with BKV nephropathy and poorer graft survival. Additionally, acute rejection is more frequent after BKVi. It is necessary to develop strategies safe and effective for these patients.