Chemical and antigenic structure of the O-polysaccharide of the lipopolysaccharides from two Acinetobacter haemolyticus strains differing only in theanomeric configuration of one glycosyl residue in their O-antigens

In a previous study [Pantophlet, R., Brade, L., Dijkshoorn, L., and Brade, H. (1998) J. Clin. Microbiol. 36, 1245-1250] the O-polysaccharide of the li popolysaccharides (LPS) from Acinetobacter haemolyticus strains 57 and 61 e xhibited indistinguishable banding-patterns following Western blot and immu nostaining with homologous or heterologous rabbit antiserum. In this report , the molecular basis for the observed cross-reactivity was elucidated, by determining the chemical structure of the polysaccharides by compositional analysis and NMR spectroscopy. The structures are: -->3)-alpha-D-QuipNAc4Nacyl-(1-->4)-beta-D-ManpNAcA-(1-->4)-alpha-L-GulpNAc A-(1-->3 up arrow OAc for strain 57, and -->3)-beta-D-QuipNAc4Nacyl-(1-->4)-beta-D-ManpNAcA-(1-->4)-alpha-L-GulpNAcA -(1-->3 up arrow OAc for strain 61 [GulpNAcA, 2-acetamido-2-deoxy-gulopyranosyluronic acid; Manp NAcA, 2-acetamido-2-deoxy-mannopyranosyluronic acid; QuipN4N, 2,4-diamino-2 ,4,6-trideoxy-glucopyranose acyl (S)-3-hydroxybutyryl], thus, differing onl y in the anomeric configuration of the QuipN4N residue. The antigenic structures were determined by generating murine monoclonal an tibodies, which were characterized by Western blot using LPS as antigen, by ELISA using LPS and de-O-acylated LPS as solid-phase antigens, and by ELIS A inhibition studies using LPS, polysaccharide, and de-O-acylated LPS as in hibitors. Of the four antibodies selected, two were specific for the respec tive LPS moieties and two were cross-reactive. All antibodies were found to require the presence of the O-acetyl group for reactivity.