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Sircar G, Bhowmik M, Sarkar RK, Najafi N, Dasgupta A, Focke-Tejkl M, Flicker S, Mittermann I, Valenta R, Bhattacharya K, Gupta Bhattacharya S. Molecular characterization of a fungal cyclophilin allergen Rhi o 2 and elucidation of antigenic determinants responsible for IgE-cross-reactivity. J Biol Chem 2019; 295:2736-2748. [PMID: 31882546 DOI: 10.1074/jbc.ra119.011659] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/16/2019] [Indexed: 01/12/2023] Open
Abstract
Cyclophilins are structurally conserved pan-allergens showing extensive cross-reactivity. So far, no precise information on cross-reactive IgE-epitopes of cyclophilins is available. Here, an 18-kDa IgE-reactive cyclophilin (Rhi o 2) was purified from Rhizopus oryzae, an indoor mold causing allergic sensitization. Based on LC-MS/MS-derived sequences of natural Rhi o 2, the full-length cDNA was cloned, and expressed as recombinant (r) allergen. Purified rRhi o 2 displayed IgE-reactivity and basophil degranulation with sera from all cyclophilin-positive patients. The melting curve of properly folded rRhi o 2 showed partial refolding after heat denaturation. The allergen displayed monomeric functional peptidyl-prolyl cis-trans isomerase (PPIase) activity. In IgE-inhibition assays, rRhi o 2 exhibited extensive cross-reactivity with various other cyclophilins reported as allergens from diverse sources including its homologous human autoantigen. By generating a series of deletion mutants, a conserved 69-residue (Asn81-Asn149) fragment at C terminus of Rhi o 2 was identified as crucial for IgE-recognition and cross-reactivity. Grafting of the Asn81-Asn149 fragment within the primary structure of yeast cyclophilin CPR1 by replacing its homologous sequence resulted in a hybrid molecule with structural folds similar to Rhi o 2. The IgE-reactivity and allergenic activity of the hybrid cyclophilin were greater than that of CPR1. Therefore, the Asn81-Asn149 fragment can be considered as the site of IgE recognition of Rhi o 2. Hence, Rhi o 2 serves as a candidate antigen for the molecular diagnosis of mold allergy, and determination of a major cross-reactive IgE-epitope has clinical potential for the design of next-generation immunotherapeutics against cyclophilin-induced allergies.
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Affiliation(s)
- Gaurab Sircar
- Department of Botany, Visva-Bharati, Santiniketan 731235, India; Division of Plant Biology (Main campus), Bose Institute, 93/1 Acharya Prafulla Chandra Rd., Kolkata 700009, India.
| | - Moumita Bhowmik
- Division of Plant Biology (Main campus), Bose Institute, 93/1 Acharya Prafulla Chandra Rd., Kolkata 700009, India
| | | | - Nazanin Najafi
- Division of Immunopathology, Department of Pathophysiology and Allergy Research, Medical University of Vienna, Center for Pathophysiology, Infectiology and Immunology, Währinger Gürtel 18-20, A-1090 Vienna, Austria
| | - Angira Dasgupta
- Department of Chest Medicine, B. R. Singh Hospital and Center for Medical Education and Research, Kolkata 700014, India
| | - Margarete Focke-Tejkl
- Division of Immunopathology, Department of Pathophysiology and Allergy Research, Medical University of Vienna, Center for Pathophysiology, Infectiology and Immunology, Währinger Gürtel 18-20, A-1090 Vienna, Austria
| | - Sabine Flicker
- Division of Immunopathology, Department of Pathophysiology and Allergy Research, Medical University of Vienna, Center for Pathophysiology, Infectiology and Immunology, Währinger Gürtel 18-20, A-1090 Vienna, Austria
| | - Irene Mittermann
- Division of Immunopathology, Department of Pathophysiology and Allergy Research, Medical University of Vienna, Center for Pathophysiology, Infectiology and Immunology, Währinger Gürtel 18-20, A-1090 Vienna, Austria
| | - Rudolf Valenta
- Division of Immunopathology, Department of Pathophysiology and Allergy Research, Medical University of Vienna, Center for Pathophysiology, Infectiology and Immunology, Währinger Gürtel 18-20, A-1090 Vienna, Austria; NRC Institute of Immunology FMBA of Russia, 115478 Moscow, Russia; Department of Clinical Immunology and Allergy, Sechenov First Moscow State Medical University, 119146 Moscow, Russian Federation
| | | | - Swati Gupta Bhattacharya
- Division of Plant Biology (Main campus), Bose Institute, 93/1 Acharya Prafulla Chandra Rd., Kolkata 700009, India.
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