An epitope is defined as the site on an antigen at which an antibody binds. In the case of proteins the epitopes can be classified as continuous (or sequential) and discontinuous according to whether or not the amino acids recognized are close together in the primary sequence or are well-separated but brought together by the folding of the protein. The methods described have permitted the localization or "mapping" of continuous epitopes on meningococcal outer-membrane proteins (OMPs), which are recognized by both monoclonal and polyclonal antibodies (MAbs/PAbs).