Conformational and linear B-cell epitopes of Asp f 2, a major allergen of Aspergillus fumigatus, bind differently to immunoglobulin E antibody in thesera of allergic bronchopulmonary aspergillosis patients

Asp f 2 is a major Aspergilus fumigatus allergen involved in allergic bronc hopulmonary aspergillosis. Knowledge of the B-cell epitopes may contribute to the understanding of immunoregulation and immunodiagnosis, To elucidate the immunoglobulin E (IgE) binding epitopes in the linear sequence of Asp f 2, we synthesized decamer peptides spanning the whole molecule of Asp f 2 on derivatized cellulose membranes and evaluated IgE binding in ABPA patien t and control sera. Peptides three to five amino acids long were synthesize d based on amino acid sequences within the IgE binding regions and evaluate d for the specificity of epitope antibody interactions. Nine IgE binding re gions were recognized in this protein of 268 amino acid residues. Of the ni ne epitopes, seven (ATQRRQI, RKYFG, HWR, YTTRR, DHFAD, ALEAYA, and THEGGQ) are present in the hydrophilic regions of Asp f 2, Immunologic evaluation o f the three recombinant fragments, Asp f 2A encompassing the N-terminal epi tope region, Asp f 2B without N- and C terminal regions of the protein, and Asp f 2C representing C-terminal epitopes, revealed that either the N- or C-terminal region of the protein is essential for the correct folding and c onformation for IgE antibody binding.