NEUTRALIZATION OF BOVINE PAPILLOMAVIRUS BY ANTIBODIES TO L1 AND L2 CAPSID PROTEINS

We have generated four mouse monoclonal antibodies (MAbs) to bovine pa pillomavirus virions that bound type-specific, adjacent, and conformat ionally dependent epitopes on the L1 major capsid protein. All four MA bs were neutralizing at ratios of 1 MAb molecule per 5 to 25 L1 molecu les, but only three effectively blocked binding of the virus to the ce ll surface. Therefore, antibodies can prevent papillomavirus infection by at least two mechanisms: inhibition of cell surface receptor bindi ng and a subsequent step in the infectious pathway. The neutralizing e pitopes of the bovine papillomavirus L2 minor capsid protein were mapp ed to the N-terminal half of L2 by blocking the neutralizing activity of full-length L2 antiserum with bacterially expressed peptides of L2. In addition, rabbit antiserum raised against amino acids 45 to 173 of L2 had a neutralizing titer of 1,000, confirming that at least part o f the N terminus of L2 is exposed on the virion surface.