VIRUS-LIKE PARTICLES OF BOVINE PAPILLOMAVIRUS TYPE-4 IN PROPHYLACTIC AND THERAPEUTIC IMMUNIZATION

Virus-like particles were produced in insect cells containing either t he L1 and L2 capsid proteins of bovine papillomavirus type 4 (BPV-4) o r only the L1 protein. Both preparations of VLPs proved to be extremel y effective prophylactic vaccines. Thirteen of 15 calves immunised wit h either L1-L2 VLPs or L1-VLPs were refractory to experimental challen ge with high doses of BPV-4 and did not develop papillomas, while 9 of 10 control animals developed multiple oral papillomas. VLPs were not efficient as therapeutic vaccine in calves with established papillomas , although VLP-vaccinated animals appeared to undergo tumour regressio n more rapidly than nonvaccinated control animals. Antibody responses in VLP-vaccinated calves were associated with prevention of disease bu t not with regression of papillomas. Thus prophylactic VLP vaccination is effective in preventing disease in this model of mucosal papilloma virus infection. VLPs and native virus share at least some conformatio nal epitopes, as shown by the cross-reactivity of their antibodies. (C ) 1996 Academic Press, Inc.