Immunological relationship between the capsular polysaccharides of Neisseria meningitidis serogroups Z and 29E.

The immunological relationship between serogroups 29E and Z of Neisseria meningitidis was investigated using bacterial agglutination, precipitin-in-gel, primary antigen binding and immune lysis assays. The two capsular polysaccharides were both cross immunogenic and cross reactive. Demonstration of the relationship using group Z antisera depended on which assay was used. It was most readily apparent in assays of immune lysis, less apparent when precipitins were sought in gel and inapparent when bacterial agglutination, the standard assay for determining serogroup, was employed. The cross reacting epitope was expressed 10-fold more within the group 29E polysaccharide than within the group Z polysaccharide. These findings imply that inclusion of either polysaccharide in a polyvalent meningococcal vaccine may obviate the need to include the other polysaccharide.