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Identification of the common antigenic determinant shared by Streptococcus pneumoniae serotypes 35A and 20 capsular
L M Beynon1, J C Richards, M B Perry
1Institute for Biological Sciences, National Research Council of Canada, Ottawa ON.
Abstract:
The specific polysaccharide antigen of Streptococcus pneumoniae serotype 35A was shown, by a combination of one- and two-dimensional NMR methods and chemical analyses, to be a high-molecular-mass polymer composed of D-galactose, D-glucose, mannitol, and phosphate (3:1:1:1). The pentasaccharide repeating unit is polymerized through phosphate diester linkages to give the structure, [formula in text] O-Acetyl substituents are present at positions 5 and 6 of the 3)-beta-D-Galf residue and at position 2 of the 6)-beta-D-Galf residue. The capsular polysaccharides of S. pneumoniae serotypes 20 and 35A both contain the disaccharide unit -->3)-beta-D-Galf-(1-->3)-beta-D-Glcp-(1--> which is the probable structural determinant responsible for the serological cross reactivity of the two polysaccharides.