Anti-Salmonella lipopolysaccharide monoclonal antibodies: characterization of Salmonella BO-, CO-, DO-, and EO-specific clones and their diagnostic usefulness

Abstract

To facilitate the identification and serotyping of Salmonella species, we established a wide variety of murine monoclonal antibodies (MAbs) that were reactive with the lipopolysaccharides (LPSs) of Salmonella serogroups B to E. An effective approach for generating LPS-reactive hybridomas was used; this required immunization of mice with LPS-coated bacteria. To screen for diagnostically useful MAbs, the MAbs were tested by enzyme-linked immunosorbent assay against a set of purified LPSs from smooth and rough Salmonella strains. At least four major groups of antibody specificities were identified: Salmonella (i) BO specific, (ii) CO specific, (iii) DO specific, and (iv) EO specific. For a more detailed epitope analysis, a panel of eight different serogroup-specific MAbs which were shown to bind the O-antigenic polysaccharide chains, yielding characteristic ladder patterns in Western blots (immunoblots) against the LPS of Salmonella serogroups B to E, were selected. The availability of various chemically defined LPS structures and Salmonella O-antigen glycoconjugates permitted the definition of O-antigenic polysaccharide epitopes recognized by each MAb that serologically corresponded to factors O3, O4, O5, O6, O7, O8, O9, and O10 on the basis of the Kauffmann-White scheme for Salmonella classification. The diagnostic accuracy of these immunochemically defined O-specific MAbs for Salmonella serotyping was demonstrated by correct identification of all 167 salmonellae (including 72 serotypes from serogroups B to E) among the 294 bacterial strains in a slide agglutination test. No false-positive reactions were detected.