Structural and immunochemical studies of two cross-reactive Proteus mirabilis O-antigens, O6 and O23, containing β1→3-linked 2-acetamido-2-deoxy-D-glucopyranose residues

A marked serological cross-reactivity was observed by ELISA and a precipitation test between anti-Proteus mirabilis O23 serum and the lipopolysaccharide as well as the O-specific polysaccharide from the Proteus mirabilis strain belonging to serogroup O6. The structures of the O-specific polysaccharides were elucidated using chemical and NMR spectroscopic analyses, and the only column component, 2-acetamido-2-deoxy-beta-D-glucopyranose (beta-D-GlcNAc), was revealed, which was suggested to be responsible for the crossreactivity observed. Both anti-O23 and anti-O6 sera were shown to react with 1, 3-linked beta-D-GlcNAc-containing O-antigen from Salmonella enterica ssp. arizonae O59 also. The lack of reactivity of Smith-degraded P. mirabilis O6 O-specific polysaccharide with homologous antiserum indicated the crucial role of alpha-D-glucuronic acid in specific antibody binding.