Identification and biochemical characterisation of Asp t 36, a new fungal allergen from Aspergillus terreus.

Abstract

Aspergillus terreus is an allergenic fungus in addition to causing infections in both humans and plants. However, the allergens in this fungus are still unknown, limiting the development of diagnostic and therapeutic strategies. We used a proteomic approach to search for allergens, identifying sixteen allergens based on two-dimensional immunoblotting with A. terreus susceptible patient sera. We further characterized triosephosphate isomerase (Asp t 36), one of the dominant immunoglobulin E (IgE)-reactive proteins. The gene was cloned and expressed inE. coli Phylogenetic analysis showed Asp t 36 to be highly conserved with close similarity to the triosephosphate isomerase protein sequence fromDermatophagoides farinae, an allergenic dust mite. We identified fourimmuno-dominant epitopesusing synthetic peptides, andmapped them on a homology-based model of the tertiary structure of Asp t 36. Among these, two were found to create a continuous surface patch on the 3D structure, rendering it an IgE binding hotspot. Biophysical analysis indicated that Asp t 36 shows similar secondary structure content and temperature sensitivity with other reported triosephosphate isomerase allergens. In vivo studies using a murine model displayed that the recombinant Asp t 36 was able to stimulate airway inflammation, as demonstrated by an influx of eosinophils, goblet cell hyperplasia, elevated serum immunoglobulins and induction of Th2 cytokines. Collectively, our results reveal the immunogenic property of Asp t 36, a major allergenfrom A. terreus, and define a new fungal allergen more broadly. This allergen could serve as a potent candidate for investigating component resolved diagnosis and immunotherapy.