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Identification of a Monoclonal Antibody Against Pneumococcal Pilus 1 Ancillary Protein Impairing Bacterial Adhesion
Fulvia Amerighi1, Maria Valeri2, Danilo Donnarumma1
1GSK Vaccines, Siena.
Abstract:
The adhesion of Streptococcus pneumoniae is a key step during colonization of human respiratory tract mucosae. Here we demonstrate that pneumococcal type I pilus significantly increases the adhesiveness of poorly adhering highly capsulated strains in vitro. Interestingly, preincubation of bacteria with antibodies against the major pilus backbone subunit (RrgB) or the adhesin component (RrgA) impaired pneumococcal association to human epithelial cells. Screening for anti-RrgA monoclonal antibodies specifically affecting the adhesive capacity of S. pneumoniae led to the identification of the monoclonal 11B9/61 antibody, which greatly reduced pilus-dependent cell contact. Proteomic-based epitope mapping of 11B9/61 monoclonal antibody revealed a well-exposed epitope on the D2 domain of RrgA as the target of this functional antibody. The data presented here confirm the importance of pilus I for S. pneumoniae pathogenesis and the potential use of antipilus antibodies to prevent bacterial colonization.
Insights
Pneumococcal type I pilus enhances Streptococcus pneumoniae adhesion to respiratory cells. Antibodies targeting pilus components like RrgA can block this attachment, suggesting a strategy to prevent bacterial colonization.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Streptococcus pneumoniae colonization of the respiratory tract is crucial for pathogenesis.
- Bacterial adhesion to host cells is a critical initial step in colonization.
- The role of type I pilus in the adhesion of S. pneumoniae requires further elucidation.
Purpose of the Study:
- To investigate the role of pneumococcal type I pilus in the adhesion of Streptococcus pneumoniae to human respiratory epithelial cells.
- To identify and characterize antibodies that can inhibit pneumococcal adhesion mediated by type I pilus.
- To explore the potential of anti-pilus antibodies as a therapeutic strategy against S. pneumoniae colonization.
Main Methods:
- In vitro adhesion assays using human epithelial cells and S. pneumoniae strains with and without type I pilus.
- Preincubation of bacteria with antibodies against pilus subunits (RrgB, RrgA) or specific monoclonal antibodies.
- Screening of monoclonal antibodies for their ability to inhibit pilus-dependent bacterial adhesion.
- Proteomic-based epitope mapping to identify the target of a functional anti-RrgA antibody.
Main Results:
- Pneumococcal type I pilus significantly enhances the adhesion of highly encapsulated S. pneumoniae strains in vitro.
- Antibodies targeting the major pilus backbone subunit (RrgB) or the adhesin (RrgA) impaired bacterial association with epithelial cells.
- Monoclonal antibody 11B9/61, targeting RrgA, effectively reduced pilus-dependent bacterial cell contact.
- Epitope mapping revealed that 11B9/61 targets a well-exposed epitope on the D2 domain of RrgA.
Conclusions:
- Type I pilus is a significant factor in the pathogenesis of Streptococcus pneumoniae by promoting bacterial adhesion.
- Targeting pneumococcal type I pilus components with specific antibodies can inhibit bacterial colonization of host cells.
- Anti-pilus antibodies, particularly those targeting RrgA, represent a promising avenue for developing novel strategies to prevent S. pneumoniae infections.
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