Structural characterization of the lipopolysaccharide O antigens of Burkholderia pseudomallei.

A serologically typical strain of Burkholderia pseudomallei (strain 304b) was found to produce two S-type lipopolysaccharides (LPS) differing in the chemical structures of their O-polysaccharide (O-PS) components. Structural analysis revealed that one O-antigenic polysaccharide (O-PS I) is an unbranched high-molecular-weight polymer of 1,3-linked 2-O-acetyl-6-deoxy-beta-D-manno-heptopyranose residues. The other LPS O antigen (O-PS II) is an unbranched polymer of repeating disaccharide units having the structure -3)-beta-D-glucopyranose-(1-3)-6-deoxy-alpha-L-talopyranose-(1- in which ca. 33% of the L-6dTalp residues bear 2-O-methyl and 4-O-acetyl substituents while the other L-6dTalp residues carry only 2-O-acetyl substituents. Analysis of a serologically atypical strain of B. pseudomallei (strain 824a) produced a single LPS O-PS which was chemically identical to the 6-deoxy-D-manno-hepan O-PS I. The production of two distinct LPS raises the interesting question of their relative immunogenicities and consequently their relative importance for diagnostic serology and for the possible development of conjugate vaccines.