Identification of shared and unique immunoglobulin E epitopes of the highly conserved tropomyosins in Blomia tropicalis and Dermatophagoides pteronyssinus

• Published in: Clinical and experimental allergy Vol. 32; no. 8; pp. 1203 - 1210
• Main Authors: Yi, F. C., Cheong, N., Shek, P. C. L., Wang, D. Y., Chua, K. Y., Lee, B. W.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science, Ltd 01.08.2002; Blackwell; Wiley Subscription Services, Inc
• Subjects: Adolescent; Adult; Aged; allergen; Allergens - genetics; Allergens - immunology; Allergic diseases; Animals; Biological and medical sciences; Blomia tropicalis; Child; Child, Preschool; Cross Reactions; Dermatophagoides pteronyssinus; Dermatophagoides pteronyssinus - immunology; DNA Probes; Dust; Epitopes - analysis; Epitopes - genetics; Gene Library; General aspects; Humans; Hypersensitivity - immunology; IgE epitope; Immunoglobulin E - blood; Immunoglobulin E - immunology; Immunopathology; Medical sciences; Mice; Middle Aged; Mites - immunology; Sequence Analysis, DNA; Singapore; Skin Tests; tropomyosin; Tropomyosin - immunology; Singapore; Human; Immunopathology; Allergy; Prick test; Antigenic determinant; Tropomyosin; IgE; Acaridida; Dermatophagoides pteronyssinus; Polymerase chain reaction; Acariformes; Arachnida; Acari; Arthropoda; Cross reaction; Pyroglyphidae; Molecular biology; Invertebrata; ELISA assay; Allergen; Skin test
• ISSN: 0954-7894; 1365-2222
• DOI: 10.1046/j.1365-2745.2002.01449.x

Summary Background Tropomyosin belongs to a class of highly conserved proteins in invertebrates and vertebrates. The invertebrate tropomyosins are allergenic in man with high IgE cross‐reactivity and have been therefore referred to as pan‐allergens. Objectives This study aimed to clone and identify the IgE epitopes of tropomyosin from Blomia tropicalis (Blo t 10) mite. Cross‐reactivity between the IgE epitopes of Blo t 10 and Der p 10 was also evaluated. Methods Blo t 10 was isolated using mouse anti‐Der p 10 antibodies. Allergenicity of the cloned Blo t 10 was confirmed by skin prick test (SPT) and enzyme‐linked immunosorbent assay (ELISA). Dose‐dependent inhibition assay was performed to determine the degree of IgE cross‐reactivity between Blo t 10 and Der p 10. Overlapping polymerase chain reaction‐derived cDNA were generated and expressed as glutathione‐S‐transferase (GST) recombinant proteins in Escherichia coli and used to identify shared and unique IgE epitopes of Blo t 10 and Der p 10. Results The cloned Blo t 10 shared up to 96% amino acid identity to tropomyosin of other mites. SPT and ELISA IgE‐immunoassay showed recombinant Blo t 10 sensitization rates of between 20% and 29% in atopic subjects. Results of SPT and dose‐dependent inhibition assays showed that some allergic individuals had unique IgE epitopes for Blo t 10. IgE epitope mapping of Blo t 10 revealed that the epitopes were mainly located at N‐ and C‐termini of the molecule. The results of ELISA inhibition assays of overlapping recombinant fragments indicated that the unique IgE epitopes of Blo t 10 were located at the C‐terminal. Conclusion Although Blo t 10 and Der p 10 are highly conserved (shared 95% amino acids identity) and significantly cross‐reactive, unique IgE epitopes do exist. The results suggest the potential deficiency of using only one of these highly conserved allergens as diagnostic or therapeutic reagents.