Antibodies against PsrP, a novel Streptococcus pneumoniae adhesin, block adhesion and protect mice against pneumococcal challenge
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Published on: February 23, 2014
Lloyd Rose1, Pooja Shivshankar, Ernesto Hinojosa
1Department of Microbiology and Immunology, the University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Abstract:
Pneumococcal serine-rich repeat protein (PsrP) is a putative adhesin encoded in the Streptococcus pneumoniae pathogenicity island psrP-secY2A2. Challenge of mice with serotype 4, strain TIGR4, and the isogenic mutants T4DeltapsrP and T4DeltapsrP-secY2A2 determined that PsrP was required for bacterial persistence in the lungs but not for colonization in the nasopharynx or replication in the bloodstream during sepsis. In vitro experiments corroborated this anatomical site-specific role; psrP mutants failed to bind to A549 and LA-4 lung cells, yet adhered normally to human nasopharyngeal epithelial cells and to cells from human and rodent capillary endothelial cell lines. We determined that the amino terminus of PsrP mediated adhesion. Microspheres coated with recombinant PsrP(SRR1-BR) (rPsrP(SRR1-BR)) adhered to A549 cells, and moreover, preincubation of cells with rPsrP(SRR1-BR) inhibited TIGR4 adhesion in vitro. Antibodies against rPsrP(SRR1-BR) also neutralized PsrP function; antiserum against rPsrP(SRR1-BR) blocked TIGR4 adhesion in vitro and, following passive immunization, it protected mice against challenge. We conclude that PsrP is an adhesin required for bacterial persistence in the lungs and that rPsrP(SRR1-BR) is a protective antigen.
Insights
Pneumococcal serine-rich repeat protein (PsrP) is crucial for Streptococcus pneumoniae persistence in mouse lungs. Recombinant PsrP and antibodies against it show potential as protective antigens against pneumococcal infections.
Area of Science:
- Microbiology
- Immunology
- Pathogen-host interactions
Background:
- Streptococcus pneumoniae is a major cause of bacterial pneumonia.
- Pneumococcal serine-rich repeat protein (PsrP) is a surface protein implicated in bacterial adhesion.
Purpose of the Study:
- To investigate the role of PsrP in Streptococcus pneumoniae pathogenesis.
- To determine the specific function and anatomical site-specificity of PsrP during infection.
Main Methods:
- In vivo mouse models of infection (lung challenge, nasopharyngeal colonization, sepsis).
- In vitro adhesion assays using various human and rodent cell lines (lung epithelial, nasopharyngeal epithelial, endothelial cells).
- Characterization of PsrP's adhesive domains and evaluation of antibodies against recombinant PsrP.
Main Results:
- PsrP is essential for bacterial persistence in the lungs but not for nasopharyngeal colonization or bloodstream replication.
- PsrP mediates adhesion to lung epithelial cells, with the N-terminus being critical for this interaction.
- Recombinant PsrP (rPsrP(SRR1-BR)) binds to lung cells and inhibits bacterial adhesion, while antibodies against it neutralize PsrP function and protect mice.
Conclusions:
- PsrP functions as a lung-specific adhesin required for Streptococcus pneumoniae persistence.
- Recombinant PsrP(SRR1-BR) represents a potential protective antigen for vaccine development against pneumococcal lung infections.
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