title: Random phage-epitope library based identification of a peptide antagonist of Mac-1 β2 integrin ligand binding.
abstract: The leukocyte β2 integrin Mac-1 (CD11b/CD18) plays a pivotal role in inflammation and host defense. To develop peptide antagonists selectively inhibiting the function of Mac-1, we used a random constrained 6-mer (cys-6aa-cys) peptide library to map the structural features of CD11b, by determining the epitope of neutralizing monoclonal antibody mAb 44a (anti-CD11b). We have used a stringent phage display strategy, which resulted in the identification of one disulfide C-RLKEKH-C constrained peptide by direct biopanning of library on decreasing amounts of purified mAb 44a. The selected peptide mimics a discontinuous epitope, a peculiar shape on the CD11b-I-domain surface. Competitive ELISA experiments with different Mac-1 ligands showed that C-RLKEKH-C is able to bind to fibrinogen, iC3b, and C1q. Furthermore, the monomeric circular peptide C-RLKEKH-C, was effective in blocking the interaction between (125)I-fibrinogen and Mac-1 (IC(50)=3.35±0.1×10(-6)M), and inhibited the adhesion of human neutrophils to fibrinogen and iC3b. These data provide information about the relative location of amino acids on the I-domain surface using mAb 44a imprint of the CD11b protein. The derived mimotope may help in the design of future anti-inflammatory therapeutic agents that can act as specific therapeutic agents targeting PMNs mediated inflammation.
authors.affiliation: Laboratoire d'Immunopathologie Vaccinologie et Génétique Moléculaire, Institut Pasteur de Tunis, Tunisia. mehdi.houimel@pasteur.rns.tn
authors.forename: Mehdi
authors.initials: M
authors.lastname: Houimel
authors.forename: Luca
authors.initials: L
authors.lastname: Mazzucchelli
mesh_terms: D000893:Anti-Inflammatory Agents / Q000737:chemistry / Q000494:pharmacology; D000911:Antibodies, Monoclonal; D001665:Binding Sites; D039481:CD11b Antigen / Q000235:genetics* / Q000378:metabolism; D018821:CD18 Antigens / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002448:Cell Adhesion; D003179:Complement C3b / Q000378:metabolism; D018604:Epitope Mapping / Q000379:methods*; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D016177:Macrophage-1 Antigen / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D019151:Peptide Library; D010455:Peptides / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000037:antagonists & inhibitors; D011485:Protein Binding; D039341:Receptors, Fibrinogen / Q000037:antagonists & inhibitors*
chemical_list: D000893:Anti-Inflammatory Agents; D000911:Antibodies, Monoclonal; D039481:CD11b Antigen; D018821:CD18 Antigens; D016177:Macrophage-1 Antigen; D019151:Peptide Library; D010455:Peptides; D010456:Peptides, Cyclic; D039341:Receptors, Fibrinogen; D003179:Complement C3b; D005340:Fibrinogen