Three open reading frames (ORF) can be found in the genome of HBoV, similar to BPV and MVC. One ORF encodes a non-structural protein (NS1) and a second one at least two capsid proteins (VP1 and VP2). The third ORF encodes a non-structural protein (NP1). The function of HBoV NS1 is unknown. In MVC and minute virus of mice, NS1 is a multifunctional protein, essential for viral DNA replication [11, 12] . Furthermore, a role in apoptosis, cell cycle arrest, and transactivation of cellular genes has been described for parvovirus B19 NS1 [13, 14, 15, 16] . NP1 is absent in other parvoviruses and, like for NS1, the function of HBoV NP1 is unknown. In MVC, NP1 plays an essential role in DNA replication [11] . Cross-complementation tests with NP1 of MVC, BPV, and HBoV showed that they all could increase DNA replication in NP1 knockout mutants, suggesting they all have analog functions [11] .