Molecular and immunologic characterization of a highly cross-reactive two EF-hand calcium-binding alder pollen allergen, Aln g 4: Structural basis for calcium-modulated IgE recognition

Brigitte Hayek, Luca Vangelista, Annalisa Pastore, Wolfgang R. Sperr, Peter Valent, Susanne Vrtala, Verena Niederberger, Anna Twardosz, Dietrich Kraft, Rudolf Valenta

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73 Citations (Scopus)

Abstract

Serum IgE was used to isolate a cDNA coding for a 9.4-kDa two EF-hand calcium-binding allergen, Aln g 4, from a λgt11 expression cDNA library constructed from alder (Alnus glutinosa) pollen. rAln g 4 was overexpressed in Escherichia coli and purified to homogeneity. It reacted with serum IgE from 18% of pollen-allergic patients (n=122); shared IgE epitopes with homologous allergens present in tree, grass, and weed pollens; and thus belongs to a family of highly cross-reactive pollen allergens. Exposure of two E. coli-expressed rAln g 4 fragments comprising amino acids 1-41 and 42- 85 to patients' IgE Abs, as well as to a rabbit antiserum raised against purified rAln g 4, indicated that most of the B cell epitopes reside in the N-terminal portion of the protein. IgE recognition of Aln g 4 was strongly modulated by the presence or absence of calcium. Circular dichroism analysis of rAln g 4 revealed that the protein consisted mostly of α helical secondary structure and possessed a remarkable thermal stability and refolding capacity, a property that was greatly reduced after calcium depletion. Circular dichroism analysis of the calcium-bound and apo form of rAln g 4 indicated that calcium-induced modulation of IgE binding could be due to changes in the protein conformation. Purified rAln g 4 elicited dose- dependent basophil histamine release and immediate type skin reactions in sensitized patients. It may hence be useful for allergy diagnosis and for specific immunotherapy.

Original languageEnglish
Pages (from-to)7031-7039
Number of pages9
JournalJournal of Immunology
Volume161
Issue number12
Publication statusPublished - Dec 15 1998

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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