A quantitative in vitro focus assay for bovine papilloma virus

A quantitative tissue culture assay for bovine papilloma virus (BPV) has been developed. Extracts of bovine papillomas which contained either BPV-1 or BPV-2 induced distinct foci in two mouse cell lines (NIH 3T3 and C127). Focus formation followed single-hit kinetics, suggesting that a single particle was required for focus induction. Preincubation of extracts with rabbit anti-BPV-1 serum neutralized their infectivity. The morphologically transformed cells contained BPV DNA sequences, grew in low serum and in soft agar, and were tumorigenic for nude mice.