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Structural determination and immunochemical characterization of the type V group B Streptococcus capsular
M R Wessels1, J L DiFabio, V J Benedì
1Channing Laboratory, Brigham and Women's Hospital, Boston, Massachusetts 02115.
The Journal of Biological Chemistry
|April 15, 1991
Summary
Researchers determined the structure of type V capsular polysaccharide from group B Streptococcus. This unique structure is antigenically distinct from other types, suggesting a complex epitope involving all sugar residues.
Area of Science:
- Microbiology
- Carbohydrate Chemistry
- Immunology
Background:
- Group B Streptococcus (GBS) is a leading cause of neonatal infections.
- GBS possesses various capsular polysaccharide (CPS) types, influencing its virulence and immune evasion.
- Understanding CPS structure is crucial for vaccine development and diagnostics.
Purpose of the Study:
- To isolate and purify the type V capsular polysaccharide of GBS.
- To elucidate the repeating unit structure of the type V CPS.
- To investigate the antigenic properties and epitope complexity of type V CPS.
Main Methods:
- Isolation and purification of type V GBS CPS.
- Methylation analysis of the polysaccharide.
- 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy.
- Analysis of degraded polysaccharide fragments.
- Immunological cross-reactivity assays.
Main Results:
- The type V CPS was isolated and purified.
- The repeating unit structure was determined, comprising D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, and sialic acid in a 3:2:1:1 molar ratio.
- Type V CPS showed no immunological cross-reactivity with other GBS types (Ia, Ib, II, III, IV).
- Antibody binding studies indicated a complex epitope involving most sugar residues.
Conclusions:
- The precise repeating unit structure of type V GBS CPS was established.
- Type V GBS CPS is antigenically distinct from other known types.
- The native epitope of type V CPS is complex, requiring multiple sugar residues for antibody recognition.