Structural analysis of the lipopolysaccharide oligosaccharide epitopes expressed by Haemophilus influenzae strain RM.118-26

The structure of the lipopolysaccharide of Haemophilus influenzae mutant st rain, RM.118-26, was investigated. Electrospray ionization-mass spectrometr y on intact lipopolysaccharide, O-deacylated lipopolysaccharide and core ol igosaccharides obtained from lipopolysaccharide after mild acid hydrolysis provided information on the composition and relative abundance of the glyco forms. Oligosaccharide samples were studied in detail using high-field NMR techniques. The structure of the major glycoform containing phosphocholine is identical to the Hex2 glycoform described for H. influenzae RM.118-28 [R isberg, A., Schweda, E.K.H. & Jansson, P.-E. (1997) Eur. J. Biochem. 243, 7 01-707]. A second major glycoform, containing three hexose residues (Hex3), in which a lactose unit, beta-D-Galp-(1-->4)-beta-D-Glcp, is attached at t he O-2 position of the terminal heptose of the inner core element, L-alpha- D-Hepp-(1-->2)-L-alpha-D-Hepp-(1-->3)-[beta-D-Glcp-(1-->4)-]-L-alpha-D-Hepp -(1-->5)-alpha-Kdo, carries no phosphocholine. Instead this lipopolysacchar ide glycoform is partly (40%) substituted by an O-acetyl group linked to th e 6-position of the glucose residue in the lactose unit and has the followi ng structure: [GRAPHICS]