RESUMO
O antigen is the major component of lipopolysaccharide LPS. The chemical structure of the O antigen determines the LPS serospecificity of the bacteria, and the diversity of O antigen is the basis for serotyping Burkholderia pseudomallei. In this study, structural elucidation of type B O antigen obtained from a clinical B. pseudomallei strain was conducted, and the effects of different types of LPS on macrophage differentiation were investigated. The O antigen was found to be composed of repeating units of [â4)-α-L-Rhap(1 â 4)-α-L-Rhap(1â2)-α-L-Rhap(1 â 2)-α-L-Rhap(1 â 3)-α-L-Rhap(1 â 3)-α-L-Rhap(1 â 4)-α-L-Rhap(1 â 6)-α-D-Galp(1â]n, where some of the â4)-α-L-Rhap(1 â units were substituted at O-3 by ß-D-Xylp(1 â residues, and minor â3)-α-L-Rhap(1 â units were substituted at O-2 by ß-D-Xylp(1 â residues. Meahwhile, the â6)-α-D-Galp(1 â units were substituted at O-3 by α-D-Galp(1 â residues. Furthermore, both type A and type B O antigens of B. pseudomallei could polarize macrophages toward the M1 phenotype, but the core oligosaccharides had no such activity. Therefore, we deduced that this polarization relies on the O antigen of LPS and might be related to the ability of B. pseudomallei to survive and replicate within macrophages. Thus, the characterization of different types of O antigen structural motifs is essential for further clarifying the persistence/survival mechanisms and inflammatory potential of B. pseudomallei.