title: Asp159 is a critical core amino acid of an IgE-binding and cross-reactive epitope of a dust mite allergen Der f 7.
abstract: Der f 7 and Der p 7 are important house dust mite allergens with known structure and suggested biological function recently. However, their IgE-binding determinants remain unknown. The purpose of this study is to identify the IgE-reactive epitopes of Der f 7 and the determinants of IgE-mediated cross-reactivity between Der f 7 and Der p 7. IgE-reactive determinants were identified by immunodot blot inhibition using synthetic overlapping peptides, allergen mutants, and a Der f 7 structural model. Our results showed that synthetic peptides with sequence (156)SILDP(160) on Der f 7 bind IgE in two of the 30 asthmatic serum samples tested. Recombinant Der f 7 I157A, L158A, or D159A mutants have reduced IgE-binding activity. Inhibition experiments confirmed Asp159 as a critical core residue for IgE-binding. Among Der p 7, Der f 7 and Der f 7 mutants with single substitution between residues 156 and 160, only the D159A mutant cannot inhibit significantly IgE-binding against Der p 7. Therefore, Asp159 contributes to IgE-mediated cross-reactivity between Der f 7 and Der p 7. The structural model constructed for Der f 7 suggests that the IgE-binding epitope forms a loop-like structure on the surface of the molecule. In conclusion, Asp 159 is a critical core residue of an IgE-binding and IgE-mediated cross-reactive epitope (156)SILDP(160) of Der f 7. Results obtained from this study provide more information on molecular and structural features related to allergenicity, underlying basis of IgE cross-reactivity between allergens, and in designing safer immunotherapy.
authors.affiliation: Department of Medical Research and Education, Taipei Veterans General Hospital, Shih-Pai, Taipei 11217, Taiwan.
authors.forename: H
authors.initials: H
authors.lastname: Chou
authors.forename: M F
authors.initials: MF
authors.lastname: Tam
authors.forename: S-S
authors.initials: SS
authors.lastname: Lee
authors.forename: R-B
authors.initials: RB
authors.lastname: Tang
authors.forename: T-H
authors.initials: TH
authors.lastname: Lin
authors.forename: H-Y
authors.initials: HY
authors.lastname: Tai
authors.forename: Y-S
authors.initials: YS
authors.lastname: Chen
authors.forename: H-D
authors.initials: HD
authors.lastname: Shen
mesh_terms: D039741:Antigens, Dermatophagoides / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D060829:Arthropod Proteins; D001224:Aspartic Acid / Q000737:chemistry* / Q000276:immunology; D001483:Base Sequence; D003429:Cross Reactions / Q000276:immunology; D018604:Epitope Mapping; D018985:Epitopes, B-Lymphocyte / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D006801:Humans; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000276:immunology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011487:Protein Conformation
chemical_list: D039741:Antigens, Dermatophagoides; D060829:Arthropod Proteins; C451161:Dermatophagoides farinae antigen f 7; C451244:Dermatophagoides pteronyssinus antigen p 7; D018985:Epitopes, B-Lymphocyte; D001224:Aspartic Acid; D007073:Immunoglobulin E