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BackgroundInterleukin-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.MethodsIL-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.ResultsAfter 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.ConclusionsThe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1133-8) contains supplementary material, which is available to authorized users.

This article presents research on the effect of microbial transglutaminase on the properties of Turkish drinking yoghurt Ayran. Transglutaminase (TGase) enzyme was added to Ayran milk at different production steps, after pasteurisation and together with starter culture addition, and two different incubation times (10 min and 1 h) were used. Three TGase-treated Ayran samples and control sample were analysed on 1st, 10th and 20th days of storage. TGase addition did not cause significant changes on chemical properties of Ayran (P > 0.05). However, physical properties of Ayran were improved by TGase throughout the storage period. Compared to the untreated control sample, pretreatment of milk with enzyme increased the viscosity dramatically (P < 0.05) and prevented serum separation. Scanning electron microscopic studies revealed that transglutaminase treatment of milk led to more regular distribution of proteins in Ayran gel and decreased gel permeability. TGase treatment did not show any unfavourable effect on the sensory properties of the final product.

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