Immunochemical studies of oligosaccharides obtained from the lipopolysaccharide of Brucella ovis

Brucella ovis rough lipopolysaccharide (R-LPS) was studied with respect to its heterogeneity, chain length, sugar composition and immunological activity. R-LPS was mildly hydrolysed and oligosaccharides were recovered in the upper phase after partition with chloroform-methanol. Gel-filtration of the upper phase in a column of Bio-Gel P-2 yielded oligosaccharides of 2, 4, 6 and 7 monosaccharide units, 2-keto-deoxy-octulosonic acid (KDO), and monosaccharides. Strong acid hydrolysis followed by paper chromatography showed that the hexa- and heptasaccharides are both composed of glucose, KDO and an unidentified sugar while tetrasaccharide is composed of glucose, mannose and glucosamine. These three oligosaccharides were able to inhibit the LPS-antibody reaction in a solid phase radioimmunoassay, suggesting the oligosaccharides bear antigenic determinants of LPS.