Surface polysaccharide of Moraxella non-liquefaciens identical to Neisseria meningitidis group B capsular polysaccharide. A chemical and immunological investigation.

In whole cell preparations of 27 nonmucoid strains of Moraxella nonliquefaciens neuraminic acid was detected by gas chromatography (GC) in 16 (59%) of the strains. Seven neuraminic-acid-containing strains were tested for agglutination with diagnostic group-specific meningococcal antisera produced in rabbits, and all were positive with group B serum. Counter-immunoelectrophoresis of bacterial suspensions of the three strains with the strongest reaction with such anti-group B serum gave distinct precipitation lines. When tested by double immunodiffusion in agarose with monoclonal antibody to meningococcal group B polysaccharide, suspension of a strain of M nonliquefaciens gave identity reaction with a strain of Neisseria meningitidis, and reacted even more strongly than the latter. Phenol extracts of M nonliquefaciens strains generally contained higher amounts of neuraminic acid than N meningitidis group B strains. Neuraminic-acid-containing polysaccharides of M nonliquefaciens strains sedimented more slowly by ultra-centrifugation than the group-specific B polysaccharide of N meningitidis strains. They also reacted more strongly with a monoclonal anti-group B antiserum than did N meningitidis group B capsular polysaccharide in an antibody binding inhibition test (solid phase radioimmunoassay). Immunological reactivity of the polysaccharides of both species was lost if extraction was performed with unbuffered phenol at 68 degrees C, instead of with neutral phenol at 4 degrees C. The results show that several strains of M nonliquefaciens, often inhabiting the human nose, have high levels of a surface polysaccharide chemically and immunologically closely similar to N meningitidis group B capsular polysaccharide. The cross-reactivity may have immunological implications for meningococcal disease.