Immunochemistry of capsular type polysaccharide and virulence properties of type VI Streptococcus agalactiae (group B streptococci)

Abstract

The immunochemistry of capsular type polysaccharide and virulence characteristics of group B streptococci (GBS), type VI, were studied. By high-pressure anion-exchange chromatography and pulsed amperometric detection, as well as by 13C nuclear magnetic resonance analysis, both extracellular and cell-bound polysaccharides were found to contain glucose, galactose, and N-acetylneuraminic acid in the molar ratio of 2:2:1, respectively. At variance with all other GBS serotypes described to date (Ia, Ib, II, III, IV, and V), no N-acetylglucosamine was present, whatever the source of the material (secreted or cell bound; reference or clinical isolate). Sialic acid was probably involved in the immunodeterminant structure of this new serotype since cleavage of this sugar from the polysaccharide gave rise to an antigen which reacted very weakly with type VI antiserum and to a precipitation line in immunodiffusion with no identity with the native type VI polysaccharide. By using type VI antiserum and the protein A-gold technique, a large capsule was observed in the type VI GBS reference strain by electron microscopy. All type VI strains examined were lethal for CD-1 mice, the 50% lethal dose after intraperitoneal challenge ranging from 1.0 (+/- 0.9, standard deviation) x 10(5) to 2.5 (+/- 1.5, standard deviation) x 10(5) CFU per mouse. A rabbit antiserum against capsular type polysaccharide exhibited both protective activity for mice injected intraperitoneally with type VI reference strain or with clinical isolates and opsonic activity in a phagocytosis assay.

Characterization of cpsF and its product CMP‐N‐acetylneuraminic acid synthetase, a group B streptococcal enzyme that can function in K1 capsular polysaccharide biosynthesis in Escherichia coli

“…GBS isolates associated with human infection are surrounded by one of several serologically distinct capsular polysaccharides. The GBS capsular polysaccharides differ in structure, but all are composed of branched oligosaccharide repeating units, and N-acetylneuraminic acid (Neu5Ac or sialic acid) always occurs at the end of the polysaccharide side chains (DiFabio et al, 1989;Jennings et al, 1983a,b;von Hunolstein et al, 1993;Wessels et al, 1987;. Neu5Ac has been shown to be critical to the virulence function of the type III GBS capsule .…”

Activation of Murine Peritoneal Macrophages by Streptococcus pneumoniae Type II Capsular Polysaccharide: Involvement of CD14‐Dependent Pathway

“…S. pneumoniae type 2 was obtained from American Type Culture Collection (Rockville, MA, USA) and cultured in BHI broth until the optical density reached 0.6. Polysaccharide antigen was prepared by the method of von Hunolstein et al [25]. Phenol was added to a ®nal concentration of 0.1%.…”

Soluble antigens from group B streptococci induce cytokine production in human blood cultures

“…Streptococcal products. Group B and type Ia and III polysaccharides were extracted from strains 090R, 090, and NCTC 11080, respectively, and purified by gel filtration and anion-exchange chromatography (22). LTA was extracted with phenol-water from supernatants of penicillin-supplemented strain 090 cultures and purified by gel filtration chromatography (13,23).…”

“…Polysaccharides and LTA preparations contained less than 1% protein (as determined by a protein assay; Bio-Rad Laboratories, Milan, Italy) or nucleic acids (as determined by measurement of the absorbance at 260 nm). Moreover, these preparations were analyzed by high-performance anion-exchange chromatography coupled with a pulsed amperometric detector (Dionex, Sunnyvale, Calif.) (11,22) and were considered of sufficient purity on the basis of the following observations. The weight of group B and type Ia and III polysaccharides was entirely accounted for by the component monosaccharides (88% Ϯ 5%) and relative humidity (12% Ϯ 3%).…”