Identification of Epicoccum purpurascens allergens by two-dimensional immunoblotting and mass spectrometry.

Sensitization to allergens of Epicoccum purpurascens is reported from many places world over. Previously, the IgE binding proteins of Epicoccum were studied by one-dimensional immunoblotting (1-DE). However, the allergens recognized by 1-DE may be a mixture of proteins appearing at the same molecular weight. In the present study, IgE-binding components of E. purpurascens were detected using two-dimensional immunoblotting and mass spectrometry. Approximately 250 protein spots were identified by Coomassie staining in the range of 14-110kDa and pI 3.5-9.5. Of these, 147 showed specific IgE reactivity with pooled patients' sera whereas 16 protein components reacted with more than 50% of the individual patients' sera. The frequency of IgE reactivity was highest (87.5%) for a 25-kDa protein (pI-7.85). Matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis of 16 protein components led to identification of 6 important allergens as phospho-glycerate kinase (PGK), RNA-dependent RNA polymerase, pyrroline-5-carboxylate dehydrogenase, 40S ribosomal protein and two proteins of unknown functions. The major allergens identified may be assessed for cross reactivity with other fungi. In conclusion, 2-DE followed by immunoblotting allowed characterization of E purpurascens allergens. Six new allergens have been identified using this technique and mass spectrometry. The availability of such relevant allergens would help in component-based diagnosis and therapy of fungal allergy.