Identification of the major allergen of Malassezia globosa relevant for atopic dermatitis

Abstract Background Malassezia globosa constitutes a part of the normal flora of human skin, but may induce IgE production in atopic dermatitis (AD). However, information on M. globosa allergens is scant. Objective To identify the major M. globosa allergens by using proteomic analysis. Methods Immunoglobulin E (IgE) immunoblotting and cross-inhibition tests for M. globosa allergens were performed using sera from AD patients and control subjects. These allergens were identified and characterized using the proteomics approach involving a combination of two-dimensional (2D) electrophoresis, mass spectrometry, and bioinformatics tools. We cloned the cDNA of this allergen using sequences obtained by 5′- and 3′-rapid amplification of cDNA ends polymerase chain reaction. Results The sera of the AD patients had IgE-reactive 40–45-kDa protein components. By 2D immunoblotting, we detected a 42-kDa protein spot with an isoelectric point (p I ) of 4.8; the protein was highly reactive to IgE and was designated MGp42. Full-length MGp42 cDNA contained a 1908-bp open reading frame encoding 635 amino acid residues (calculated molecular mass, 69.7 kDa; p I , 6.02). The N-terminal MGp42 sequence started from the 250th residue (Asp-250) of the deduced amino acid sequence and consisted of 386 amino acid residues; these results are consistent with those of 2D immunoblotting. MGp42 showed sequence similarity to members of the heat shock protein 70 (hsp70) family. Immunoblot inhibition tests revealed no IgE cross-reactivity between MGp42 and human HSP70. Conclusions MGp42 may be a cleavage product of intact HSP70. This novel M. globosa allergen could be useful for the diagnosis of AD.