The L1 and L2 proteins of BPV-2 have been produced in Escherichia coli as beta-galactosidase fusion proteins. The fusion proteins have been used to vaccinate calves both prophylactically and therapeutically. The L1 fusion protein prevented tumor formation when administered before challenge with BPV-2, while the L2 fusion protein was very effective in promoting tumor rejection, independently from whether it was administered before or after challenge. Animals vaccinated with L1, but not with L2, responded rapidly with production of serum neutralizing antibodies, showing that this peptide contains B-cell-specific epitopes. The massive infiltration of lymphocytes in the tumors of L2-vaccinated animals suggests that the peptide contains epitopes specific for T-cells. The two structural proteins of BPV-2 therefore interact with both efferent arms of the immune system, and this observation allows the choice between two different types of antiviral vaccination.