A murine monoclonal antibody that recognizes a genus-specific epitope in the Salmonella lipopolysaccharide outer core

A murine monoclonal antibody 105 made from spleen cells of a mouse immunized with a mixture of common Salmonella serotypes reacted specifically with salmonellae from the most frequently encountered O serogroups of A (O:2) to E (O:3), and with strains from the less common O serogroups that represent the subspecies I, II, IIIb, IV, V and VI. Specificity for Salmonella was demonstrated by the lack of reactivity of monoclonal antibody 105 with any of the 30 other different species of Gram-positive and Gram-negative bacteria tested including 16 species in the family of Enterobacteriaceae. Studies to elucidate its binding epitope have shown that it reacts with the three distal sugar residues joined through specific anomeric linkages as present only in the Salmonella lipopolysaccharide outer core, which explains its specificity for the Salmonella. The failure of monoclonal antibody 105 to react with a subspecies IIIa Salmonella suggested a different outer core structure in this strain of Salmonella and also that monoclonal antibodies to the outer core of Salmonella lipopolysaccharide should be useful in the molecular analysis of their diversity.