Selection of Listeria monocytogenes InlA-Binding Peptides Using Phage Display—Novel Compounds for Diagnostic Applications?

Listeria monocytogenes is a pathogenic, gram-positive bacterium causing foodborne infections and listeriosis, an infection responsible for serious medical conditions, especially for pregnant women, newborns, or people with a weak immune system. Even after antibiotic treatment, 30% of clinical infections result in death. L. monocytogenes is able to enter and multiply in mammalian cells. Invasion into epithelial cells in the human intestine is mediated by the interaction of the bacterial surface protein internalin A (InlA) with the host cell receptor E-cadherin (E-cad). We have used phage display to select InlA-specific peptides consisting of 12 amino acids using a randomized, recombinant peptide library. We could demonstrate that the selected peptides bound to recombinant InlA protein as well as to L. monocytogenes cells. In vitro, some of the peptides inhibited the interaction between recombinant InlA and human E-cad. As far as we know, this is the first publication on the development of InlA-specific peptide ligands. In the future, our peptides might be used for the development of innovative diagnostic tools or even therapeutic approaches.