Selection of LigA-binding peptides by bacterial display

Abstract

Leptospirosis is a severe disease of human and animals caused by pathogenic Leptospira spp. Previous findings reveal that the organisms express leptospiral immunoglobulin-like protein A (LigA) on their surfaces only in vivo, which is believed to serve as a virulence factor for host cell attachment and invasion. Recently, the LigA protein has become a potential target for laboratory investigation and vaccine development. In the present study, screening and selection of LigA-binding peptides have successfully been carried out with the aid of bacterial display system. After five rounds of bio-panning, peptide sequences of MSQRRAIPTGSI, ILSSPKLRADDL and VVKAGMMPVASL were found to exhibit high affinity to bind to immobilized LigA. No consensus sequence was observed among 12 isolated bacterial clones. The peptide MSQRRAIPTGSI demonstrated the highest binding activity to LigA with no cross-reactivity to the bacterial lipopolysaccharide. Emphasis can be taken that the LigA-binding peptides showed sequence similarity to those of the binder molecules such as ABC transporters, Leucine-rich repeats (LRR), and Zinc-finger protein. Interestingly, both the ABC transporters and the Leucine-rich repeats engage with several biological processes at the cell membranes. Moreover, it is well-established that the LRR plays imperative roles in protein-protein interaction, particularly between bacterial peptide and host receptors. Therefore, our findings lend support to the evidences that expression of the LigA on bacterial surfaces possessed binding capability to host proteins, receptors or extracellular matrices and mediated their attachment on the host cell membranes. Taken together, significant from this work not only gains insights into the plausible binding sites of LigA on the host cells but also opens up a high feasibility to utilize the LigA-binding peptides as diagnostic and therapeutic tools in the future. © EuroJournals Publishing, Inc. 2009.