Dynamics of BKPyV reactivation and risk of hemorrhagic cystitis after allogeneic hematopoietic stem cell transplantation

OBJECTIVES: Aim of this retrospective study was to analyze the dynamics of BKPyV reactivation in allogeneic hematopoietic stem cell transplant recipients in order to identify patients with higher risk to develop BKPyV-associated hemorrhagic cystitis (BKPyV-associated HC). METHODS: The study included 58 allo-HSCT recipients from the University Hospital of Cologne detected BKPyV positive by real-time PCR between 2009 and 2015. For correlative analysis, the first detected BKPyV-DNA load in urine and in plasma as well as the onset and severity of HC following the first day of conditioning regimen was considered. Phylogenetic analysis of BKPyV isolates was performed. RESULTS: In 25 of 58 patients, BKPyV-DNA was detected in urine only (group U), whereas 33 patients developed additional viremia (group P). A chronologic sequence viruria-viremia-HC was identified. Viral load of >106 copies/mL at first viruria and evidence of viremia after 45 days from the start of conditioning represented risk factors for the onset of HC. Molecular characterization revealed a non-stereotypic distribution of viral subtypes across groups U and P. CONCLUSIONS: Monitoring of BKPyV-DNA by real-time PCR after initiation of conditioning, regularly performed in clinical practice, can be a crucial tool for the early identification of patients with higher risk of BKPyV-associated HC.