Open AccessStructure and serology of the native polysaccharide antigen of type Ia group B Streptococcus
Author(s) -
Harold J. Jennings,
Karl-Gunnar Rosell,
Dennis L. Kasper
Publication year - 1980
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.77.5.2931
Subject(s) - serology , microbiology and biotechnology , streptococcus , antigen , polysaccharide , group a , group (periodic table) , biology , serotype , virology , antibody , medicine , immunology , bacteria , chemistry , genetics , biochemistry , organic chemistry
The native polysaccharide antigen isolated from type Ia group BStreptococcus by using pH-controlled growth conditions and extraction procedures contains D-galactose, D-glucose, 2-acetamido-2-deoxy-D-glucose, and sialic acid in the molar ratio of 2:1:1:1. The structure of the native type Ia antigen has been elucidated; it can be represented by the following repeating unit in which all the side-chain β-D-galactopyranose units are masked by sialic acid residues: [Formula: see text] Removal of all the sialic acid groups yields the incomplete type Ia polysacharide antigen with exposed terminal β-D-galactopyranose residues. Antisera to type Ia organisms produced in rabbits according to the Lancefield procedures contain antibodies specific for both the native and incomplete antigens. Although sialic acid is not itself a determinant in the formation of antibodies to the native polysaccharide, it is an essential part of a larger determinant. In order to maintain the high degree of immunologic specificity of the native antigen, this determinant must be at least a trisaccharide unit, because the native polysaccharide as isolated has terminal disaccharide units [α-D-NeuAcp -(2→3)-β-D-Galp ] identical to those found in the human M and N blood group substances and fetuin. Formation of antibodies to the incomplete antigen is due to determinants terminating in β-D-galactopyranose residues. These determinants are probably generated by the removal of the masking sialic acid residues from the cell-associated native polysaccharide by degradative processes that occur in organisms grown without pH control.