Browsing by Author "Kiziltepe, Tanyel"

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    Covalent Heterobivalent Inhibitor Design for Inhibition of IgE-Dependent Penicillin Allergy in a Murine Model
    (Science Publications, 2019-05-17) Deak, Peter E.; Kim, Baksun; Koh, Byunghee; Qayum, Amina Abdul; Kiziltepe, Tanyel; Kaplan, Mark H.; Bilgicer, Basar; Pediatrics, School of Medicine
    Drug allergies occur when hapten-like drug metabolites conjugated to serum proteins, through their interactions with specific immunoglobulin E (IgE), trigger allergic reactions that can be life-threatening. A molecule termed covalent heterobivalent inhibitor (cHBI) was designed to specifically target drug-hapten specific IgE to prevent it from binding drug-haptenated serum proteins. cHBI binds the two independent sites on a drug-hapten specific antibody and covalently conjugates only to the specific IgE, permanently inhibiting it. The cHBI design was evaluated via ELISA to measure cHBI-IgE binding, degranulation assays of rat basophil leukemia (RBL) cells for in vitro efficacy, and mouse models of ear swelling and systemic anaphylaxis responses for in vivo efficacy. The cHBI design was evaluated using two seperate models: one specific to inhibit penicillin G reactive IgE, and another to inhibit IgE specific to a model compound, dansyl. We show that cHBI conjugated specifically to its target antibody and inhibited degranulation in cellular degranulation assays using RBL cells. Furthermore, cHBIs demonstrated in vivo inhibition of allergic responses in both murine models. We establish the cHBI design to be a versatile platform for inhibiting hapten/IgE interactions, which can potentially be applied to inhibit IgE mediated allergic reactions to any drug/small molecule allergy.
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    Designer covalent heterobivalent inhibitors prevent IgE-dependent responses to peanut allergen
    (National Academy of Sciences, 2019-04-30) Deak, Peter E.; Kim, Baksun; Qayum, Amina Abdul; Shin, Jaeho; Vitalpur, Girish; Kloepfer, Kirsten M.; Turner, Matthew J.; Smith, Neal; Shreffler, Wayne G.; Kiziltepe, Tanyel; Kaplan, Mark H.; Bilgicer, Basar; Pediatrics, School of Medicine
    Allergies are a result of allergen proteins cross-linking allergen-specific IgE (sIgE) on the surface of mast cells and basophils. The diversity and complexity of allergen epitopes, and high-affinity of the sIgE-allergen interaction have impaired the development of allergen-specific inhibitors of allergic responses. This study presents a design of food allergen-specific sIgE inhibitors named covalent heterobivalent inhibitors (cHBIs) that selectively form covalent bonds to only sIgEs, thereby permanently inhibiting them. Using screening reagents termed nanoallergens, we identified two immunodominant epitopes in peanuts that were common in a population of 16 allergic patients. Two cHBIs designed to inhibit only these two epitopes completely abrogated the allergic response in 14 of the 16 patients in an in vitro assay and inhibited basophil activation in an allergic patient ex vivo analysis. The efficacy of the cHBI design has valuable clinical implications for many allergen-specific responses and more broadly for any antibody-based disease.
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    Inhibition of weak-affinity epitope-IgE interactions prevents mast cell degranulation
    (Nature Publishing Group, 2013-12) Handlogten, Michael W; Kiziltepe, Tanyel; Serezani, Ana P; Kaplan, Mark H; Bilgicer, Basar; Department of Pediatrics, IU School of Medicine
    Development of specific inhibitors of allergy has had limited success, in part, owing to a lack of experimental models that reflect the complexity of allergen-IgE interactions. We designed a heterotetravalent allergen (HtTA) system, which reflects epitope heterogeneity, polyclonal response and number of immunodominant epitopes observed in natural allergens, thereby providing a physiologically relevant experimental model to study mast cell degranulation. The HtTA design revealed the importance of weak-affinity epitopes in allergy, particularly when presented with high-affinity epitopes. The effect of selective inhibition of weak-affinity epitope-IgE interactions was investigated with heterobivalent inhibitors (HBIs) designed to simultaneously target the antigen- and nucleotide-binding sites on the IgE Fab. HBI demonstrated enhanced avidity for the target IgE and was a potent inhibitor of degranulation in vitro and in vivo. These results demonstrate that partial inhibition of allergen-IgE interactions was sufficient to prevent mast cell degranulation, thus establishing the therapeutic potential of the HBI design.
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    Synthetic Allergen Design Reveals The Significance of Moderate Affinity Epitopes in Mast Cell Degranulation
    (ACS, 2012) Handlogten, Michael W.; Kiziltepe, Tanyel; Alves, Nathan J.; Bilgicer, Basar
    This study describes the design of a well-defined homotetravalent synthetic allergen (HTA) system to investigate the effect of hapten–IgE interactions on mast cell degranulation. A library of DNP variants with varying affinities for IgEDNP was generated (Kd from 8.1 nM to 9.2 μM), and 8 HTAs spanning this range were synthesized via conjugation of each DNP variant to the tetravalent scaffold. HTAs with hapten Kd < 235 nM stimulated degranulation following a bell-shaped dose response curve with maximum response occurring near the hapten Kd. HTAs with hapten Kd ≥ 235 nM failed to stimulate degranulation. To mimic physiological conditions, the percent of allergen specific IgE on cell surface was varied, and maximum degranulation occurred at 25% IgEDNP. These results demonstrated that moderate hapten–IgE affinities are sufficient to trigger mast cell degranulation. Moreover, this study established the HTA design as a well-defined, controllable, and physiologically relevant experimental system to elucidate the mast cell degranulation mechanism.