Characterization of Burkholderia pseudomallei O antigens in different clinical strains

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 [-> 4)-alpha-L-Rhap(1 -> 4)-alpha-L-Rhap(1 -> 2)-alpha-L-Rhap(1 -> 2)-alpha-L-Rhap(1 -> 3)-alpha-L-Rhap(1 -> 3)-alpha-L-Rhap(1 -> 4)-alpha-L-Rhap(1 -> 6)-alpha-D-Galp(1 ->]n, where some of the -> 4)-alpha-L-Rhap(1 -> units were substituted at O-3 by beta-D-Xylp(1 -> residues, and minor -> 3)-alpha-L-Rhap(1 -> units were substituted at O-2 by beta-D-Xylp(1 -> residues. Meahwhile, the -> 6)-alpha-D-Galp(1 -> units were substituted at O-3 by alpha-D-Galp(1 -> 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.

Automated summary

This study investigated the structural elucidation of type B O antigen from a clinical B. pseudomallei strain and the effects of different types of LPS on macrophage differentiation. The O antigen was found to consist of repeating units with specific substitutions. Both type A and type B O antigens could polarize macrophages towards the M1 phenotype. Characterizing different types of O antigen structural motifs is essential for understanding the persistence/survival mechanisms and inflammatory potential of B. pseudomallei.