Solid phase peptide synthesis and TLR-5 activity analysis of pertide fragments from the Salmonella muenchen flagellin protein

Drug design strategies begin by determining the simplest ligand necessary to activate a receptor of interest. The Toll-Like Receptor-5 (TLR-5) is an attractive target for pharmaceutical modulation because it initiates an innate immune response. A TLR-5 agonist or antagonist could help remedy a variety of disorders. Flagellin, the primary component of bacterial flagella, is the only known TLR-5 ligand. Three short regions within this protein are suggested to activate TLR-5: Peptide-N1, LQRVRELAVQ; Peptide-N2, LAVQSANGTNSQSD; and Peptide-C1, QNRFNSAITNLGNT. Here, we report the synthesis of these peptides and their activity against TLR-5 expressing HEK-293 cells. Our goal was to resolve the minimal region of flagellin necessary to bind and/or activate TLR-5. Results showed significant agonist activity (P<0.01) with peptide N2-b (LAVQSANGTN), and peptide N2-f (LAVQSANGTNSQ). Peptide N2-c (ANGTN) and N2-d (LAVQS) showed significant (P<0.05) antagonistic properties for TLR-5. These peptides could make interesting lead compounds to modify for optimal TLR-5 activity.