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

Abstract 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.