Structural analysis of the lipopolysaccharide from nontypeable Haemophilus influenzae strain 1003

Abstract

Structural analysis of the lipopolysaccharide (LPS) of nontypeable Haemophilus influenzae strain 1003 has been achieved by the application of high-field NMR techniques, ESI-MS, capillary electrophoresis coupled to ESI-MS, composition and linkage analyses on O-deacylated LPS and core oligosaccharide material. It was found that the LPS contains the common structural element of H. influenzae, L-α-D-Hepp-(1 → 2)-[PEtn → 6]-L-α-D-Hepp-(1 → 3)-[β-D-Glcp-(1 → 4)]-L-α-D-Hepp-(1 → 5)-[PP Etn → 4]-α-Kdop-(2 → 6)-Lipid A, in which the β-D-Glcp residue is substituted by phosphocholine at O-6 and an acetyl group at O-4. A second acetyl group is located at O-3 of the distal heptose residue (HepIII). HepIII is chain elongated at O-2 by either a β-D-Glcp residue (major), lactose or sialyllactose (minor, i.e. α-Neu5Ac-(2 → 3)-β-D-Galp-(1 → 4)-β-D-Glcp), where a third minor acetylation site was identified at the glucose residue. Disialylated species were also detected. In addition, a minor substitution of ester-linked glycine at HepIII and Kdo was observed.