title: Screening for peptides targeted to IL-7Rα for molecular imaging of rheumatoid arthritis synovium.
abstract: Interleukin-7 receptor alpha (IL-7Rα) represents a biomarker with potential applications in rheumatoid arthritis (RA) diagnosis and therapy. We have therefore searched by phage display potential IL-7Rα specific peptides with the primary goal being to develop in vivo molecular imaging tools.
  
  
  
  IL-7Rα-targeted peptides were searched within a disulfide-constrained combinatorial phage displayed library of random linear heptapeptides. The apparent dissociation constant (Kd) and half maximal inhibition constant (IC50) were estimated for phage clones and synthesized peptides by ELISA. We used 5-Aza-2'-deoxycytidine (ADC)-stimulated Jurkat cells and human synovial tissue from patients with RA for in vitro characterization of peptides. For molecular imaging studies performed by magnetic resonance imaging (MRI), experimental arthritis was induced in DBA/1 male mice by immunization with an emulsion of complete Freund's adjuvant and type II collagen from chicken sternal cartilage.
  
  
  
  After several steps of phage display and peptide screening, two IL-7Rα-specific heptapeptides (P258 and P725) were selected from the initial library, based on their affinity for the target (extracellular domain of IL-7Rα, which contains a fibronectin type III repeat-like sequence). P258 (a linear peptide obtained by removing the Cys-constraint) had the lowest affinity for fibronectin itself and was therefore proposed for molecular imaging. After grafting to ultra-small superparamagnetic particles of iron oxide (USPIO), P258 produced a strong negative contrast on MRI in mice with collagen-induced arthritis (CIA), even at 2 hours post injection. The co-localization of USPIO-P258 with IL-7Rα-expressing cells in the synovial tissue from CIA mice and its ability to discriminate the level of IL-7R expression and the disease severity confirmed its efficacy as an in vivo IL-7Rα imaging agent. Interestingly, the cyclic peptide (P725), which was less adequate for molecular imaging because of higher affinity for fibronectin, had a strong ability to compete with IL-7 for the IL-7Rα binding sites, making it a potential candidate for blocking applications. Accordingly, P725 prevented the signal transducer and activator of transcription 5 (STAT5) activation induced by IL-7 in ADC-stimulated Jurkat cells.
  
  
  
  The two peptides identified in this work demonstrate that IL-7Rα targeting in RA presents potential applications for in vivo molecular imaging and putative blocking purposes.
authors.affiliation: Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons, Avenue Maistriau 19, Mendeleev Building, Mons, B-7000, Belgium. Carmen.Burtea@umons.ac.be.
authors.forename: Carmen
authors.initials: C
authors.lastname: Burtea
authors.affiliation: Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons, Avenue Maistriau 19, Mendeleev Building, Mons, B-7000, Belgium.|Center for Microscopy and Molecular Imaging, 8, rue Adrienne Bolland, Gosselies, 6041, Belgium.
authors.forename: Sophie
authors.initials: S
authors.lastname: Laurent
authors.affiliation: Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons, Avenue Maistriau 19, Mendeleev Building, Mons, B-7000, Belgium.
authors.forename: Tuba
authors.initials: T
authors.lastname: Sanli
authors.affiliation: Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons, Avenue Maistriau 19, Mendeleev Building, Mons, B-7000, Belgium.
authors.forename: Deborah
authors.initials: D
authors.lastname: Fanfone
authors.affiliation: Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons, Avenue Maistriau 19, Mendeleev Building, Mons, B-7000, Belgium.
authors.forename: Aude
authors.initials: A
authors.lastname: Devalckeneer
authors.affiliation: Department of Pathology, Erasme Hospital, Université Libre de Bruxelles, Route de Lennik 808, Brussels, 1070, Belgium.|DIAPath, Center for Microscopy and Molecular Imaging, 8, rue Adrienne Bolland, Gosselies, 6041, Belgium.|Present address: Molecular Pathology Laboratory, ONCODNA - The Cancer Theranostic Company, 25 Av. Georges Lemaître, Gosselies, 6041, Belgium.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Sauvage
authors.affiliation: Eurogentec S.A., Liège Science Park, Rue du Bois Saint-Jean 5, Seraing, B-4102, Belgium.|Present address: ASIT Biotech s.a, 3 Rue des Chasseurs Ardennais, Angleur, 4031, Belgium.
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Beckers
authors.affiliation: Department of Pathology, Erasme Hospital, Université Libre de Bruxelles, Route de Lennik 808, Brussels, 1070, Belgium.|DIAPath, Center for Microscopy and Molecular Imaging, 8, rue Adrienne Bolland, Gosselies, 6041, Belgium.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Rorive
authors.affiliation: Department of Pathology, Erasme Hospital, Université Libre de Bruxelles, Route de Lennik 808, Brussels, 1070, Belgium.|DIAPath, Center for Microscopy and Molecular Imaging, 8, rue Adrienne Bolland, Gosselies, 6041, Belgium.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Salmon
authors.affiliation: Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons, Avenue Maistriau 19, Mendeleev Building, Mons, B-7000, Belgium.|Center for Microscopy and Molecular Imaging, 8, rue Adrienne Bolland, Gosselies, 6041, Belgium.
authors.forename: Luce
authors.initials: L
authors.lastname: Vander Elst
authors.affiliation: Pôle de pathologies rhumatismales inflammatoires et systémiques, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Avenue Mounier 53, Brussels, 1200, Belgium.
authors.forename: Bernard R
authors.initials: BR
authors.lastname: Lauwerys
authors.affiliation: Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Laboratory, University of Mons, Avenue Maistriau 19, Mendeleev Building, Mons, B-7000, Belgium.|Center for Microscopy and Molecular Imaging, 8, rue Adrienne Bolland, Gosselies, 6041, Belgium.
authors.forename: Robert N
authors.initials: RN
authors.lastname: Muller
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000000981:diagnostic imaging / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging* / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis; D003911:Dextrans; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D057054:Molecular Imaging / Q000379:methods*; D010456:Peptides, Cyclic; D020395:Receptors, Interleukin-7 / Q000032:analysis*; D013583:Synovial Membrane / Q000000981:diagnostic imaging* / Q000378:metabolism
chemical_list: D015415:Biomarkers; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010456:Peptides, Cyclic; D020395:Receptors, Interleukin-7; C097921:ferumoxtran-10; C415350:interleukin-7 receptor, alpha chain
keywords: IL-7 receptor; MRI; Molecular imaging; Peptides; Phage display; Rheumatoid arthritis; Ultra-small superparamagnetic particles of iron oxide