The major allergen of Alternaria alternata (Alt a 1) is expressed in other members of the Pleosporaceae family

Abstract

There is general consensus regarding the scarce cross-reactivity existing between Alternaria alternata and other allergenic moulds such as Aspergillus fumigatus, Penicillium notatum or Cladosporium herbarum. However, A. alternata has been shown to have a very significant level of allergenic cross-reactivity with other fungi belonging to the Pleosporaceae family. To date, no biological identity or homologies with other proteins have been described for Alt a 1, and it remains unclear whether the major allergen Alt a 1 contributes to the cross-reactivity shown for these moulds. Specific quantification of Alt a 1 in culture filtrates of Stemphylium botryosum, Ulocladium botrytis, Curvularia lunata, Alternaria tenuissima, C. herbarum, Penicillium chrysogenum and Asp. fumigatus, and immunoblotting using culture filtrate extracts from the above-mentioned moulds and rabbit serum anti-recombinant Alt a 1 have shown significant amounts of Alt a 1 in culture filtrates as well as antigenic components ranging from 14 to 20 kDa that strongly react with the specific serum for all taxonomically related species (Pleosporaceae family). No reactions were revealed in culture filtrates of Cladosporium, Penicillium and Aspergillus. These results restrict the cross-reactivity phenomenon due to Alt a 1 to the scope of the taxonomical term of family.

Sensitization to fungal allergens: Resolved and unresolved issues

“…61 Alt a 1 has been reported to cross-react with homologous fungal proteins from members of the Pleosporaceae family such as Stemphylium, Ulocladium, and Curvularia. 1,59,62 In contrast, allergenic proteins other than Alt a 1 exhibit a high sequence similarity with homologous proteins from taxonomically unrelated fungi. Thus, the diagnostic and clinical relevance of allergenic proteins other than Alt a 1 with respect to Alternaria allergy is unclear.…”

IgE sensitization to fungi mirrors fungal phylogenetic systematics

“…A alternata expresses the clinically important allergen Alt a 1, whose homologs have been identified as allergens in primarily other Alternaria species, 2 although recent immunoblotting results indicate a certain degree of IgE-cross reactivity within the Pleosporales order. 31 Thus, the lower similarity to other Pleosporales species could reflect that several of the individuals are sensitized to A alternata mainly through Alt a 1 and are thereby less likely to show positive IgE tests toward other fungal species. Furthermore, the correlation coefficient between Candida and Saccharomyces is not outstandingly high (compared with other values of Table I), and a plausible cause is that among the individuals with only 1 positive test, 50% are sensitized to Candida (data not shown).…”

The Spectrum of Fungal Allergy

“…Recently, several fungal species were tested for Alt a 1 homologues using a rabbit-anti-rAlt a 1 serum [141]. The authors could show that cross-reactive proteins were detectable in Stemphylium botryosum , Ulocladium botrytis , Curvularia lunata and Alternaria tenuissima , but not in C. herbarum , P. chrysogenum and A. fumigatus .…”