The Use of a Monoclonal Antibody Specific for the N-terminal Region of Southern Bean Mosaic Virus as a Probe of Virus Structure

Summary The N-terminal cyanogen bromide peptide of the coat protein of the cowpea strain of southern bean mosaic virus (SBMV-C) was purified by high-pressure liquid chromatography and used as an immunogen in the production of monoclonal antibodies. One monoclonal antibody, designated 4D6, bound to both purified peptide and immobilized virus in a solid-phase ELISA. The reactivity of this monoclonal antibody with immobilized peptide could not be inhibited by native SBMV-C but was inhibited by low levels of EDTA-swollen virus in an antigen inhibition ELISA. The binding of 4D6 to the swollen conformation of the virus was not significantly diminished upon collapsing the swollen virus by pH adjustment or addition of calcium ions. Reactivity of the antibody was also observed with native virus particles which had been dialysed against weakly alkaline buffers. The binding of 4D6 was extremely sensitive to trypsin proteolysis of the virus coat protein, indicating that the antibody binding site was most likely located within the first 30 amino acid residues of the N-terminus. Monoclonal antibody 4D6 also cross-reacted weakly with red clover necrotic mosaic virus in both indirect ELISA and antigen inhibition ELISA.