Structural and immunological studies of the Haemophilus influenzae type d capsular polysaccharide

Employing a combination of chemical and spectroscopic techniques, the structure of the Haemophilus influenzae type d capsular polysaccharide was found to be →4)-β-d-GlcNAc-(1→3)-β-d-ManNAcA-(1→. l-Alanine, l-serine, and l-threonine, in the molar ratios of ～1.0:1.0:0.3, were linked to C-6 of the d-mannosyluronic residue as amides; the (serine + alanine + threonine) to ManNAcA ratio was ～0.95:1.0. Removal of the amino acids by mild hydrolysis with sodium hydroxide resulted in a material that was cross-reactive with the native, type d polymer. The base-treated, type d polysaccharide was not observed to cross-react with either the H. influenzae type e or Escherichia coli K7 capsular polysaccharide, both of which are structurally similar to type d.