Incidence of BK virus infections in allogeneic hematopoietic stem cell transplant recipients

BK virus (BKV) is a non-enveloped virus with icosahedral capsid containing circular double-stranded DNA genome. Hemorrhagic cystitis associated with BK virus is a common complication in patients undergoing hematopoietic stem cell transplantation (HSCT). The aim of this study is to investigate the incidence of BKV infections by real-time polymerase chain reaction in pediatric patients after allogeneic hematopoietic stem cell transplantation. In between November 2018 and November 2019, a total of 51 patients between the ages of 11 months and 17 years were included in the study. BKV Bosphore® v1 quantification kit (Geneworks Anatolia, Turkey) was used for detection of BKV DNA in urine and blood samples. Among total of 51 patients, the incidence of BKV infection was found to be 86.3% (44/51). Allogeneic HSCT was performed in 40 patients and autologous HSCT in 11 patients. BK viruria and / or viremia were detected in 85% (34) of 40 patients who underwent allogeneic HSCT and 90% (10) in the autologous group. In 18 (35%; 18/51) of the patients, 14 of them allogeneic and 4 of them autologous, urine BK DNA viral load was above 107 copies/ml and preemptive treatment was started. While the incidence of BKV-associated hemorrhagic cystitis was 15% (6/40) in the allogeneic group, hemorrhagic cystitis was not observed in the autologous group. High-level BK viruria (>107copies/ml) was found in 41% (9) of 22 patients which were BKV positive before transplantation, while in 27.5% (8) of 29 patients which were BKV negative before transplantation, thus BKV positivity before transplantation was considered as a risk factor for high-level BK viruria. While 50% (3) of 6 patients who developed acute GVHD had high viral load in urine, 32.3% (11) of 34 patients who did not develop acute GVHD had high BK viruria with a lower rate, and the presence of acute GVHD seems to be also a risk factor. Hemorrhagic cystitis was prevented in 12 (66.6%) of 18 patients who received preemptive treatment, while hemorrhagic cystitis developed in 6 (33.3%). The viral load in the urine was found to be 107-9 copies/ml within 2 weeks before the development of hemorrhagic cystitis and it has been identified as a prognostic indicator. In conclusion, early diagnosis of viral infections by monitoring BKV viral load in HSCT patients will be effective in preventing the progression of the disease by providing timely initiation of preemptive treatment.