Role of BK virus infection in end‐stage renal disease patients waiting for kidney transplantation – viral replication dynamics from pre‐ to post‐transplant

We report the prevalence of BK virus (BKV) infection before renal transplantation and the dynamics of BKV viremia from pre‐ to post‐transplantation. We assessed 60 kidney transplanted patients from a single cohort in Italy, treated with identical immunosuppressive therapy, for BK viremia at pre‐transplantation, 12 h, and three and six months post‐transplantation. Polymerase chain reaction showed that the prevalence of plasma BKV replication – considered a marker of infection – was 20% in pre‐transplant patients. All pre‐transplant‐positive patients remained positive post‐transplant, whereas the majority of pre‐transplant‐negative patients remained negative. Viremia dynamics classification revealed three clusters of patients: Cluster A++, pre‐transplant‐positive patients (20%) who tested positive at least once post‐transplant; Cluster B?+, pre‐transplant‐negative patients (28%) who tested positive at least once post‐transplant; and Cluster C– –, pre‐transplant‐negative patients (52%) who remained negative throughout. These clusters presented significant differences related to the prevalence of substantially positive patients with high plasma viral load (>10³ copies/mL) in cluster A, but not in donors’ or grafts’ characteristics. We suggest that pre‐transplant viral status should be considered as an additional risk factor for post‐transplant BKV replication. Therefore, pre‐transplant BKV infection screening in kidney transplant patients should be performed for improving planning of personalized immunosuppressant schemes and specific post‐transplant surveillance.