Tuesday, March 10, 2009

Conformational and Linear B-Cell Epitopes of Asp f 2, a Major Allergen of Aspergillus fumigatus

Antibodies can be generated against most commonly linear epitopes and less frequently to discontinous/conformational epitopes. In this work the authors describe Asp f 2 a major Aspergillus fumigatus (AF) allergen involved in allergic bronchopulmonary aspergillosis (ABPA). It is important to know the corresponding B-cell epitopes in order to the understandi its immunoregulation and immunodiagnosis. In order to identify the IgE binding epitopes from the linear sequence of Asp f 2, a series of decamer peptides comprising the whole molecule of Asp f 2 were synthesized on a solid support (ie; derivatized cellulose membranes) and tested IgE binding in ABPA patient and control sera. Also short synthetic peptides (three to five amino acids long) were assembled based on amino acid residues within the IgE binding regions and tested for epitope-antibody interactions. A total of nine IgE binding regions were identifed within the 268 amino acid domain and the following epitopes ,ATQRRQI, RKYFG, HWR, YTTRR, DHFAD, ALEAYA, and THEGGQ were found in the hydrophilic domain of Asp f 2. Three recombinant fragments, Asp f 2A that includes the N-terminal epitope region, Asp f 2B with no N- and C-terminal regions of the protein, and Asp f 2C comprising C-terminal epitopes, showed that either the N- or C-terminal region of the protein is necessary for the proper folding and conformation for IgE to effect antibody binding.

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