Effect of bovine papillomavirus E2 protein-specific monoclonal antibodies on papillomavirus DNA replication

The bovine papillomavirus type 1 (BPV-1) E2 protein is the master regulator of papillomavirus replication and transcription. We have raised a panel of monoclonal antibodies (MAbs) against the BPV 1 E2 protein and used them to probe the structure and function of the protein. Five MAbs reacted with li near epitopes, and four MAbs recognized conformation-dependent epitopes whi ch mapped within the C-terminal DNA-binding and dimerization domain. MAb 1E 2 was able to recognize the replication- and transactivation defective but not the competent conformation of the transactivation domain of the E2 prot ein. MAb 5H4 prevented efficiently the formation of E2-DNA as well as E2-de pendent E1-E2-origin complexes and also dissociated preformed complexes in a concentration dependent manner. Cotransfection of several MAbs with the B PV-1 minimal origin plasmid pUCAlu into CHO3.15 cells resulted in a dose de pendent inhibition of replication. Inhibition of replication by MAb 5H4 and the Fab' fragment of 5H4 correlated with their ability to dissociate the E 2 protein from the DNA. MAb 3F12 and MAbs 1H10 and 1E4, directed against th e hinge region, were also capable of inhibiting BPV-1 origin replication in CHO4.15 cells. However, the Fab' fragments of 1H10 and 3F12 had no effect in the transient replication assay. These data suggest that MAbs directed a gainst the hinge region sterically hinder the inter- or intramolecular inte ractions required for the replication activity of the E2 protein.