Persistence of non-integrated viral DNA in bovine cells transformed in vitro by bovine papillomavirus type 2

Papillomaviruses induce benign tumours (warts) in their natural hosts. Several bovine papillomaviruses (BPV 1–5) have been described1–5. BPV 2 represents the virus isolated from classical cutaneous fibropapillomas found on the neck and shoulders of cattle5. In heterologous hosts, including the hamster and horse, it induces fibrosarcomas, sarcomas and fibromas, none of which possess virus particles but all of which contain viral DNA6–8. Both BPV 2 and its DNA induce cellular transformation in vitro9–16, although the presence of viral DNA in such transformed bovine cells has so far not been reported. Here we demonstrate the presence and maintenance of BPV 2 DNA sequences in bovine cells transformed in vitro by BPV 2.