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Bacteroides fragilis lipopolysaccharide and group B streptococcus serotype II glycocalyx have a common major
1Department of Medical Microbiology, University of Turku, Finland.
Abstract:
A monoclonal antibody (MAB) to the beta-1-6-linked digalactose structure in the lipopolysaccharide (LPS) of Bacteroides fragilis reacted with 47 of 416 group B Streptococcus (GBS) strains tested by an immunofluorescence technique (IF). The reactivity of MAB was, with a few exceptions, limited to type II GBS. Gas chromatography-mass spectrometry analysis demonstrated that an antigen purified by immunoaffinity chromatography using MAB from type II GBS contained galactose, glucose and fatty acids. This confirmed that MAB is directed to the digalactose (which in earlier studies was found to occur) in the capsular lipocarbohydrate specific to type II GBS. The positive strains yielded a strong, apple-green surface stain by means of the IF using MAB. Various immuno-electron microscopic (IEM) methods showed that the determinant was located in the glycocalyx layer of GBS at a distance of about 15 nm from the streptococcal cell wall. The structure harbouring the determinant was found to be very loosely attached to the bacteria. However the cross-reactive determinant seemed to maintain its immunoreactivity whether it was extracted by gentle washing with saline or with harsher treatments usually reserved for preparing streptococcal polysaccharide antigens. In conclusion, the study shows that the determinant is an integral part of the type-specific antigen of type II GBS and that MAB has a potential use as a serotyping reagent.
Insights
A new monoclonal antibody (MAB) specifically targets a unique digalactose structure in type II Group B Streptococcus (GBS). This antibody shows potential for accurately identifying and serotyping GBS strains.
Area of Science:
- Microbiology
- Immunology
- Bacteriology
Background:
- Group B Streptococcus (GBS) is a significant pathogen, particularly in neonates.
- Accurate serotyping of GBS is crucial for epidemiological studies and vaccine development.
- The capsular lipocarbohydrate (LPS) of GBS contains type-specific antigens.
Purpose of the Study:
- To develop and characterize a monoclonal antibody (MAB) targeting a specific structure in GBS.
- To investigate the reactivity of the MAB with different GBS strains.
- To determine the location and nature of the targeted antigen.
Main Methods:
- Immunofluorescence technique (IF) using a MAB against a beta-1-6-linked digalactose structure.
- Gas chromatography-mass spectrometry (GC-MS) for antigen analysis.
- Immuno-electron microscopy (IEM) for antigen localization.
Main Results:
- The MAB reacted with 47 out of 416 GBS strains, primarily type II GBS.
- GC-MS confirmed the antigen contained galactose, glucose, and fatty acids, identifying it as a digalactose structure.
- IEM localized the determinant to the GBS glycocalyx, approximately 15 nm from the cell wall.
Conclusions:
- The MAB recognizes an integral part of the type II GBS-specific antigen.
- The targeted digalactose structure is a key component of the type II GBS capsular lipocarbohydrate.
- This MAB has potential utility as a serotyping reagent for GBS identification.