Background: Better understanding of pneumococcal pathogenesis may identify new therapeutic approaches. We have previously identified cell wall proteins with known enzymatic activity (PtsA, GtS, NOX, and FBA). Currently we have found that these proteins moonlight as adhesins in the cell wall. Their putative target molecules were identified and peptides derived from the target molecules were tested for their ability to interfere in bacterial adhesion in vitro and prevent disease development in vivo.
Methods: The ability of the protein to interfere in bacterial adhesion to A549 cells and the reduced adhesion of null mutant bacteria adhesion to A549 cells was tested. To identify putative target molecules a phage display library was screened with the recombinant proteins. The residence of the putative target molecules homologous to the insert peptide in the protein binding phages was confirmed by immunostaining. Peptides derived from putative target molecules were tested for their ability to inhibit bacterial adhesion in vitro and prevent disease development in infected mice.
Results: The recombinant proteins inhibited bacterial adhesion and the viable null mutant bacteria demonstrated reduced adhesion in vitro and virulence in vivo. Target molecules derived peptides were capable of inhibiting bacterial adhesion to lung derived cells in vitro and reduce colonization and mortality in infected mice in vivo.
Conclusion: Some of the proteins residing in the pneumococcal cell wall were found to moonlight as adhesins. Identification of their target molecules enabled the synthesis of peptides capable of interfering in bacterial adhesion and reduce disease development in vivo.
