IDENTIFICATION AND Il\1MUNOGENICITY OF POLYSACCHARIDE ANTIGENS OF PASTEURELLA MULTOCIDA STRAINS INVOLVED IN HAEMORRHAGIC SEPTICAEMIA Naj1nul

Polysaccharide antigens of Pasteurella multocida serotype B:2,5 were identified by immunodiffusion and immunoelectrophoresis. The immunodiffusion tests showed that the first line, near the well containing the whole polysaccharide extract (WPE) represent LPS because this precipitation line occurs by diffusion using antiserum raised against P. multocida serotypes 8:2,5 and E:2,5 but not with 8:3,4. The second precipitation line, near the well containing antiserum raised against P. multocitla serotype 8:2,5, represent the bacterial.capsule because this precipitation line also occurs by diffusion using preparation B (capsular antigen) or a whole cell extract of P. multocida serotype B:3,4. Immunoelectrophoresis was used to further characterize the polysaccharide antigens. The LPS remained near the antigen well, wherds the less hydrophobic and more acidic bacterial capsule moved further towards the anode. Immune responses against these antigens were measured in sera from a vaccinated buffalo. The analysis of the anti-polysaccharide response after removal of anti-LPS antibodies demonstnlted a very low response to capsular material, whereas a 5-times higher response was measured against LPS.