Identification of candidate host proteins that interact with LipL32, the major outer membrane protein of pathogenic Leptospira, by random phage display peptide library.

Leptospirosis is a worldwide zoonotic disease caused by pathogenic Leptospira spp. Rodent species are the major reservoir hosts that can excrete leptospires in their urine leading to environmental contamination. After gaining entry into the host via skin breaks and mucosa, leptospires disseminate through the bloodstream to target organs causing a wide range of disease manifestations in susceptible mammalian hosts. The crucial step of infection requires host-pathogen interactions. LipL32, the major outer membrane protein (OMP) of pathogenic Leptospira, is conserved among pathogenic leptospires, immunogenic, and expressed in target organs during acute infection in animal models. Therefore, it may play a key role in host-microbe interactions. To identify host proteins that interact with LipL32, phage display technology was employed in our study. Recombinant LipL32 was used as a target molecule for biopanning with a random heptapeptide phage library to enrich for phages expressing peptides with high affinity to LipL32. After three rounds of panning, 44 plaques of eluted phages were subjected to pyrosequencing. Six different peptide sequences were identified and used to search for matching proteins in the database. Putative proteins with potential binding to LipL32 are proteins known to be expressed on the surface of target cells of pathogenic Leptospira such as chloride channel accessory 2, glycoprotein VI, scavenger receptor expressed by endothelial cell isoform I (SREC-I), coronin 2A, laminin alpha 5, collagen XX, and prostaglandin receptor EP1. However, interactions of LipL32 with these host proteins and their role in the pathogenesis of leptospirosis requires experimental confirmation.