Real-life study assessing the clinical diagnosis of allergy and sensitization in atopic patients using the ISAC method(molecular allergology)

Abstract

RATIONALE: Systemic Seminal Plasma Hypersensitivity (SPH) is caused by specific IgE to human prostate specific antigen (hPSA). Presensitization to dog PSA (Can f 5) was reported to be associated with SPH in women sensitized to dog due to cross-reactivity. Conformational epitope mapping of hPSA is required to elucidate this cross-reactivity and to design hypoallergenic derivatives for desensitization. METHODS: Sequence-and structure-based bioinformatic analyses were performed to identify potential hPSA epitope(s). Sequences of hPSA and other known serine protease allergens were retrieved from the uniprot database. The hPSA structure was obtained from its monoclonal antibodybound form (2ZCH.pdb) to study its antigenic surface and to model the Can f 5 structure. Site-directed mutagenesis of top solvent-exposed residues was performed to assess their role in IgE binding. RESULTS: About 45% (5054.97 A 2) of hPSA surface is polar. Four areas, including a region Arg85-Ser99 (containing the mAb binding site) have been identified as potential epitopes. A close evolutionary relationship between hPSA and Can f 5 (57% sequence identity; 89% sequence similarity) was noted. The alpha-C backbone superimposition (global RMSD51.1 A) indicated an overall structural similarity, while conserved surfaceexposed patches indicated possible cross-reactivity between hPSA and Can f 5. Preliminary results of site-directed mutagenesis indicated the importance of specific surface exposed residues (e.g. R85) in IgE binding. CONCLUSIONS: Epitope residues are dispersed on hPSA surface. Conserved patches might be responsible for cross-reactivity between hPSA and Can f 5 in some patients. Peptide microarray-based epitope mapping and detailed characterization of mutant hPSA proteins are ongoing to confirm these findings.