Purification, characterization and immunological properties of the serotype-specific capsular polysaccharide of Pasteurella haemolytica serotype A7 organisms

The serotype-specific capsular polysaccharide from two strains of Pasteurella haemolytica serotype A7 organisms was purified and characterized by chemical analysis and by 1H and 13C NMR spectroscopy using one- and two-dimensional methods. The polymer has the repeating unit----3)-beta-2-acetamido-2-deoxygalactopyranose-(1----3)-alpha- 2-acetamido- 2-deoxy-6-O-acetyl-glucopyranose-(1-phosphate----. It was immunogenic (capable of eliciting antibodies) for sheep. Chemical removal of O-acetyl groups destroyed both the ability of the polymer to adhere to sheep erythrocytes at neutral pH and the ability to form immune precipitates with specific antisera. Studies using the protein A-gold technique in the electron microscope showed the polysaccharide to be peripherally localized on the bacterial surface.