Purification, characterization and immunological properties of the serotype-specific capsular polysaccharide of Pasteurella haemolytica (serotype A1) organisms

The serotype-specific capsular polysaccharide from two strains of Pasteurella haemolytica serotype A1 organisms was purified and characterized by chemical analysis and NMR spectroscopy. The polymer has the structure----3)-O-(2-acetamido-2-deoxy-4-O-acetyl-beta-D-mannopyranos yluronic acid)-(1----4)-O-(2-acetamido-2-deoxy-beta-D-mannopyranose)-(1----. The polysaccharide was immunogenic (able to evoke production of antibodies) for sheep but not for rabbits. Immuno electron-microscopy studies using the Protein A-gold technique showed the polysaccharide to be peripherally located on the bacterial surface. Reduction, oxidation and de-O-acetylation of the polymer did not appear to alter its immunological precipitability with specific antiserum, but all three treatments destroyed its ability to adhere to sheep erythrocytes at neutral pH. De-N-acetylation of the polymer destroyed both immunological precipitability and erythrocyte adherence.