Abstract
BK polyomavirus (BKPyV) reactivates in 20-40% after kidney transplantation and causes BK virus-associated nephropathy (BKVN) in 1-10% cases with potential detrimental effect on allograft survival. Four genotypes of BKPyV have been recognized so far according to variations of viral protein 1 (VP1), however their biological implication is not fully understood.