Identification and biochemical characterization 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 in E. coli. Phylogenetic analysis showed Asp t 36 to be highly conserved with close similarity to the triosephosphate isomerase protein sequence from Dermatophagoides farinae, an allergenic dust mite. We identified four immuno-dominant epitopes using synthetic peptides, and mapped 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 allergen from 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.

EAACIMolecular Allergology User's Guide 2.0

“…Mould Asp f 11 was ascertained as the major allergen (90% sensitization rates in Aspergillus sensitized subjects and Mala s 6 induced sensitization rates between 21 and 25% in patients with atopic dermatitis 841 {Twaroch, 2015 #1434}. The first fungal TIM was identified as allergen in Aspergillus terreus as Asp t 36 inducing allergic rhinitis and asthma in sensitized patients 843 . TIM is highly conserved and a common allergen of sea food and mite allergy.…”

Genomics of Shrimp Allergens and Beyond

“…TIM was found as a cross-reactivity allergen in other crustaceans such as crab (Scy p 8) [111], lobster (Arc s 8), and crayfish (Pro c 8) [89] (Table 3), as well as a food allergen in catfish (Pan h 8) [112]. Additionally, TIM has been reported as an airway allergen in wheat (Tri a 31) [113], mold (Asp t 36) [114], tree pollen extract (Pla a 7), and mite (Der f 25, Der p 25) [115], and as an injection or inhalation allergen in mosquito (Aed a 12). In addition to shrimp, FABP was first recognized as an allergen in storage mite Blomia tropicalis (Bronswijk, Cock and Oshima, 1973) (Blo t 13) in 1997 [116], followed by other mites (Aca s 13, Lep d 1, Tyr p 13, Der f 13, Der p 13) [117][118][119][120].…”

Newly defined allergens in the WHO/IUIS Allergen Nomenclature Database during 01/2019‐03/2021

“…Fungi are well‐known for containing a plethora of allergens 51 . Asp t 36 was reported as the first allergenic fungal TIM and was shown to be cross‐reactive with TIMs from the cockroach Blatella germanica and the mite Dermatophagoides farinae , Der f 25 12 . Given the high conservation of TIM sequences, one might expect to see further examples of cross‐reactivity between these fungal and arthropod allergens.…”

“…Asp t 36, a major allergen from the mold Aspergillus terreus , has been described for the first time. 12 Fifteen Aspergillus terreus allergic patients’ sera reacted with this allergen, defining its importance for characterizing mold allergy.…”

“… 55 plant allergens (1 contact, 38 respiratory, and 16 food allergens), 50 animal allergens (19 respiratory, 28 food, and 3 venom allergens), and 1 fungal allergen were identified. First allergens identified from a specific protein group: Oxygen‐evolving enhancer protein 2 from Indian hemp (Can s 4) 8 Filamin from mud crab (Scy p 9) 5 Collagens alpha from barramundi (Lat c 6) 9 and Atlantic salmon (Sal s 6) 10 Glucose‐6‐phosphate isomerase from striped catfish (Pan h 11) 10 Group 4 late embryogenesis abundant protein from chickpea (Cic a 1) 11 Allergen families expanded to additional species: Asp t 36, 12 first allergenic fungal triosephosphate isomerase (from Aspergillus terreus ) Rap v 2, 13 first allergenic paramyosin in molluscs (from Rapana venosa ) Sal s 4 10 and Pan h 4, 10 first allergenic tropomyosins in fish Sal s 7 10 and Pan h 7, 10 first allergenic creatine kinases in fish …”