BK polyomavirus genotypes and progression of BKV disease in renal transplant recipients

Background. BK virus (BKV) reactivation is a significant cause of BK Polyomavirus associated nephropathy (BKPyVN) resulting in acute graft rejection in 1-10% of post-renal transplant recipients. However, the association of BKV genotypes with development of BKPyVN is poorly understood. Here we aimed to determine the prevalence of BKV genotypes in post-renal transplant recipients, and its association with BKPyVN disease progression.

Method. Two methods were utilised to genotype BKV. A 800bp fragment of virus VP1 antigen region was amplified using nested (PCR) followed by sequencing. The genotypes were determined according to a previously developed algorithm based on analysing 100bp region of the VP1 gene. Furthermore, the logarithm results were validated with the constructed phylogenetic tree. The results were correlated with patient viral loads and development of BKPyVN.

Results. BK virus DNA was detected in 32 (69%) of 46 post-renal transplant recipients with BK viremia, while BKPyVN was only reported in two (4.3%)patients. 30 out of 32 samples were successfully genotyped (93.7%) with 23 (76.6%) belonging to the BKV Ib-2 subtype and seven (23.3%) belonging to the BKV Ib-1 subtype and with no cases representing genotype II, III and IV. All cases with confirmed BKPyVN matched to the BKV Ib-2 genotype. Additionally, no significance differences were observed between BKV genotypes in regards to viral loads, development of viremia, HLA mismatch, age or sex.

Conclusion. The results indicate no correlations between BKV genotypes and the development of BKPyVN. Furthermore,a high distribution of BKV genotype Ib-2 was found among BKV infected patients within this cohort.