Characterization of Brucella ovis surface antigens

A rough antigen (SRA) extracted from Brucella ovis in hot saline by Myers procedure, showed three precipitation lines when tested in immunodiffusion against sera from experimentally infected rams. The components responsible for the lines could be isolated by ultracentrifugation or gel filtration which gave 3 fractions, named PI, PII and PIII. The lipopolysaccharide (LPS) appeared in the pellet (SRA-pp) after ultracentrifugation as judged by the presence of lipids, sugar composition, 2 keto-2deoxyoctulosonic acid (KDO), and its characteristic immunoelectrophoretic and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns. SRA-pp contained the antigen responsible for one of the immunoprecipitation lines of SRA and the supernatant (SRA-sn) contained only antigens responsible for the other two. Gel filtration of SRA-pp showed the presence of PI, while SRA-sn gave PII with high protein content and PIII with high carbohydrate content. Immunological activity in gel diffusion (GD) of the Fraction PII and PIII was specific for sera of B. ovis infected rams. Sera from rams experimentally infected with smooth strains (Brucella abortus and melitensis), were not able to react with these antigens.