Sialic acid-containing polysaccharides of Neisseria meningitidis and Escherichia coli strain Bos-12: structure and immunology.

A polysaccharide antigenically related to that of group C Neisseria meningitidis was isolated from Escherichia coli strain Bos-12 (O48: K91:NM). Like the polysaccharides of groups B and CN. meningitidis, the Bos-12 antigen was shown to be a pure polymer of sialic acid. The 13C-nuclear magnetic resonance studies of the groups B and C polysaccharides indicated that the former consists of units of sialic acid joined in alpha-2 leads to 8 linkages, whereas the latter contains sialic acid residues linked by alpha-2 leads to 9 glycosidic bonds. Chemical and nuclear magnetic resonance studies of the polysaccharide of E. coli strain Bos-12 established that it is a heteropolymer containing both alpha-2 leads to 8 and alpha-2 leads to 9 linkages. Physical parameters including partial specific volume, reduced viscosity, diffusion and sedimentation coefficients, shape, weight-average molecular weight, and the Stokes radius of the polysaccharides of groups A, B, and C N. meningitidis have been determined. The results indicate that the polysaccharides are highly asymmetric and exist in solution as rigid rods; aggregates are formed by the association of these rods. The polysaccharides appear to have "restricted" length.