The antigenicity of tobacco mosaic virus

The antigenic properties of the tobacco mosaic virus (TMV) have been studie d extensively for more than 50 years. Distinct antigenic determinants calle d neotopes and cryptotopes have been identified at the surface of intact vi rions and dissociated coat protein subunits, respectively, indicating that the quaternary structure of the virus influences the antigenic properties. A correlation has been found to exist between the location of seven to ten residue-long continuous epitopes in the TMV coat protein and the degree of segmental mobility along the polypeptide chain. Immunoelectron microscopy, using antibodies specific for the bottom surface of the protein subunit, sh owed that these antibodies reacted with both ends of the stacked-disk aggre gates of viral protein. This finding indicates that the stacked disks are b ipolar and cannot be converted directly into helical viral rods as has been previously assumed. TMV epitopes have been mapped at the surface of coat p rotein subunits using biosensor technology. The ability of certain monoclon al antibodies to block the cotranslational disassembly of virions during th e infection process was found to be linked to the precise location of their complementary epitopes and not to their binding affinity Such blocking ant ibodies, which act by sterically preventing the interaction between virions and ribosomes may, when expressed in plants, be useful for controlling vir us infection.