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Monoclonal antibodies that recognize a common pneumococcal protein with similarities to streptococcal group A surface
Abstract:
Monoclonal antibodies (MAbs) against clinical isolates of Streptococcus pneumoniae were produced in a search for common pneumococcal proteins. One of the fusions generated two MAbs, 174,B-8 (immunoglobulin G2a) and 177,D-8 (immunoglobulin G1), which by Western blotting (immunoblotting) stained with a main band of 40 kDa found in all isolates of S. pneumoniae examined. Cross-reactivity studies with streptococci other than pneumococci revealed very weak or moderate reactions with the MAbs. The 40-kDa protein was isolated by immunoaffinity chromatography and subsequent preparative Western blotting. N-terminal amino acid sequencing showed 90% amino acid sequence homology with a surface-located glyceraldehyde-3-phosphate dehydrogenase from Streptococcus pyogenes. This protein has also been reported to exhibit binding to mammalian proteins such as fibronectin, which may serve as host receptors. The epitopes for MAbs 174,B-8 and 177,D-8 reacting with the pneumococcal analog were not accessible to antibody binding in live bacteria but were exposed after heat killing. The MAbs showed negligible cross-reactions with S. pyogenes.
Insights
Researchers identified a common 40 kDa protein in Streptococcus pneumoniae using monoclonal antibodies (MAbs). This protein is similar to glyceraldehyde-3-phosphate dehydrogenase and its antibody-binding sites are exposed after heat treatment.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Streptococcus pneumoniae is a significant human pathogen.
- Identifying conserved proteins is crucial for developing diagnostics and therapeutics.
- Monoclonal antibodies (MAbs) are valuable tools for protein characterization.
Purpose of the Study:
- To identify common proteins in clinical isolates of Streptococcus pneumoniae.
- To characterize a novel 40 kDa protein recognized by MAbs.
- To investigate the potential role of this protein in pneumococcal pathogenesis.
Main Methods:
- Production of monoclonal antibodies against S. pneumoniae isolates.
- Western blotting (immunoblotting) to detect protein targets.
- Immunoaffinity chromatography for protein isolation.
- N-terminal amino acid sequencing for protein identification.
Main Results:
- Two MAbs (174,B-8 and 177,D-8) identified a conserved 40 kDa protein in all S. pneumoniae isolates.
- The 40 kDa protein showed 90% sequence homology to glyceraldehyde-3-phosphate dehydrogenase from Streptococcus pyogenes.
- Antibody epitopes were inaccessible on live bacteria but exposed after heat killing.
- Minimal cross-reactivity was observed with other streptococcal species.
Conclusions:
- A conserved 40 kDa protein, likely a glyceraldehyde-3-phosphate dehydrogenase analog, was identified in Streptococcus pneumoniae.
- This protein's surface epitopes are masked in live bacteria but become accessible upon heat treatment.
- The findings provide a basis for further investigation into the protein's role in pneumococcal infections and potential as a diagnostic or therapeutic target.