[Immunogenicity of the surface polysaccharide of serotype A meningococci possessing different physico-chemical properties].

The influence of changes in the physico-chemical parameters of serogroup A meningococcal polysaccharide on its immunogenicity for mice was studied by means of passive local hemolysis in gel and the passive hemagglutination test. The polysaccharide was depolymerized by heating at 100 degrees C for 5, 30 and 120 minutes; during this process the progressing decrease of the molecular weight and the content of O-acetyl groups in the preparation could be observed. Mice showed high sensitivity to changes in the above-mentioned physico-chemical parameters, which was manifested by a sharp drop in the intensity of the immune response of the animals to the heated samples of the antigen. The role of the parameters under study, i. e. the molecular weight of the antigen and the presence of O-acetyl groups, in the manifestations of the immunogenicity of polysaccharide A is discussed.