Characterization of Brucella polysaccharide B

Abstract

Polysaccharide B was extracted from Brucella melitensis 16M and from a rough strain of Brucella abortus 45/20 by autoclaving or trichloroacetic acid extraction of whole cells and by a new method involving mild leaching of cells. The material obtained by either of the established procedures was contaminated by O polysaccharide. The new leaching protocol eliminated this impurity and provided a pure glucan, which was regarded as polysaccharide B. This polysaccharide was found by high-performance liquid chromatography separations, chemical composition, methylation, and two-dimensional homo- and heteronuclear magnetic resonance experiments to be a family of nonreducing cyclic 1,2-linked polymers of beta-D-glucopyranosyl residues. The degree of polymerization varied between 17 and 24. Polysaccharide B was essentially identical to cyclic D-glucans produced by Rhizobia, Agrobacteria, and other bacterial species. Pure polysaccharide B did not precipitate with Brucella anti-A or anti-M serum and did not inhibit the serological reaction of Brucella A or M antigen with either bovine or murine monoclonal Brucella anti-A or anti-M serum. Previously described serological reactions of polysaccharide B preparations with Brucella anti-A and anti-M sera are related in this study to the presence in crude extracts of contaminants with the antigenic properties of Brucella lipopolysaccharide O polysaccharides.