Type:
Whole Allergen
Whole Allergen
m14 Epicoccum purpurascens
m14 Epicoccum purpurascens Scientific Information
Display Name:
Epicoccum purpurascens
Route of Exposure:
Inhalation
Family:
Didymellaceae
Species:
purpurascens
Latin Name:
Epicoccum purpurascens
Other Names:
Epicoccum purpurascens
Summary
Epicoccum purpurascens (E. nigrum) is a ubiquitous mold of the Order Pleosporales, mostly found in plant materials and soil worldwide. It is mostly a saprophyte and shows a variety of phenotypes. The particles causing allergic reactions are airborne conidia (a type of spore).
Hypersensitivity pneumonitis (HP) and asthma are the main clinical presentations of E. purpurascens allergy. Cross reactivity with other molds, especially if taxonomically close, may occur.
Allergen
Nature
Epicoccum purpurascens (formerly known as E. nigrum) is a common anamorphic saprophytic (occasionally weakly pathogenic) mold colonizing the phylloplane, or leaf surface (1, 2). It is found worldwide in air and soil, showing a variety of phenotypes and morphological features (3)
E. purpurascens primarily grows on grasses and grains (4) and has also been isolated from pipe surfaces (5), a water stream, and various leaves, twigs and lichen (3). Epicoccum spp. are common saprophytes of bark(6). E. purpurascens (E. nigrum) has also been identified on the surface of withered grapes and involved in the contamination of fruit-drying rooms(7).
E. purpurascens is considered to be a ‘dry weather’ spore forming fungus (Denning 2014), with a defined peak recorded between March-April (8).
Spores of Epicoccum spp. were the fifth most common mold caught during a study spanning a two year period (8). E. purpurascens spores are easily released when wind hits the substrates onto which it grows, reaching peak concentrations on dry, windy afternoons (4). The spores may also be released passively by rain, as the drops directly strike fungus on leaf surfaces, or parts of the plants being shaken, allowing the spores to be released (2).
In culture, hyphae first appear as a loose aggregation, quickly developing into a more densely packed surface, with sporogenous cells growing from the hyphae surfaces. Conidia develop from the tip of each sporogenous cell as it enlarges, forming a single conidium initially, which then separates into multiple copies before being released. Mature conidia tend to be spherical and of variable size, up to 25 μm in diameter (1).
Metabolites of E. purpurascens (E. nigrum) have potential uses in biotechnology, for example as antifungal or antibiotic candidates (3)
Taxonomy
Taxonomic tree of Epicoccum genus (9) |
|
|---|---|
Domain |
Eukaryota |
Kingdom |
Fungi |
Phylum |
Ascomycota |
Subphylum |
Pezizomycotina |
Class |
Dothideomycetes |
Order |
Pleosporales |
Family |
Didymellaceae |
Genus |
Epicoccum |
Taxonomic tree of Epicoccum genus (9) |
|---|
Tissue
Conidia (asexual spores) are the tissue that causes allergic reactions (1).
Epidemiology
Worldwide distribution
Sensitization to Epicoccus purpurascens has been reported in 5–7% of people worldwide (10).
Risk factors
Being male was associated with poorer control of asthma symptoms in patients exposed to indoor molds, including E. purpurascens (11).
Environmental Characteristics
Worldwide distribution
E. nigrum has been isolated worldwide (3).
Route of Exposure
Main
Inhalation of conidia (1, 12).
Detection
Main methods
Personal volumetric petri plate sampler (8) or a single stage Andersen air sampler (13).
Clinical Relevance
E. purpurascens (Epicoccum nigrum) was identified as the cause of hypersensitivity pneumonitis (HP) in two children, following exposure to a moldy basement (14).
E. nigrum can colonize the nasal and sinus cavities and cause allergic fungal sinusitis (AFS) (13).
Asthma
Fungal sensitization exacerbates asthma (15); exposure to E. nigrum was associated with poorer control of asthma symptoms in male patients (11). Patients with life-threatening asthma needing admission to the intensive care unit or experiencing a respiratory arrest are significantly more likely to be sensitized to certain fungi, including E. purpurascens (15, 16).
Diagnostics Sensitization
The presence of allergen-specific antibodies is usually determined by skin prick tests (SPTs) and serology for IgE (8, 12, 15). SPT reactions to Epicoccum purpurascens allergens in patients with respiratory allergies varied in positivity, with 42% of patients showing mild to moderately positive reactions, 12% showing moderately positive reactions and 5.3% showing highly positive skin reactions (8). In the same study, the serum of SPT+ (positive) patients was tested by ELISA for the presence of IgE specific for the fungal antigens that caused the positive skin reactions. This showed 64.7% concordance for E. purpurascens antigens when comparing the skin-prick tests and the ELISA in vitro immunoassay (8).
Prevention and Therapy
Allergen immunotherapy
Immunotherapy is currently not recommended for patients allergic to molds, due to complexities of the allergens and patient co-allergies (12). However, a study carried out in mice showed that the enzymatic properties of the E. purpurascens allergenic antigen Epi p 1 (a serine protease) can elicit inflammation. The authors suggest that an enzymatically inactive Epi p 1 may be a candidate for immunotherapy (17).
Prevention strategies
Avoidance is difficult to achieve (12), due to the ubiquitous nature of E. purpurascens spores, especially in dry, windy periods (4, 8).
Molecular Aspects
Allergenic molecules
Using two-dimensional immunoblotting and mass spectrometry, a number of E. purpurascens antigens which react with IgE from allergic patients have been identified. The highest IgE reactivity was recorded for a 25 kDa protein; further analyses narrowed the pool of antigenic proteins from 147 (which all reacted to pooled sera) down to 6 important allergens (18). A major glycoprotein allergen was identified named Epi p 1; this 33.5 kDa allergen, a serine protease, was recognized by antibodies in the serum of all the patients allergic to E. purpurascens (10, 19).
Cross-reactivity
Cross-reactivity has been demonstrated to other molds. A 33.5 kDa E. purpurascens allergen named Epi p 1 was recognized by rabbit antibodies specific for 5 other molds, namely Aspergillus fumigatus, Alternaria alternata, Cladosporium herbatum, Fusarium solani and Curvularia lunata (10). In another study, the serum of 10 patients diagnosed with allergic fungal sinusitis (AFS) was used to determine whether IgE specific to other fungi (including E. purpurascens) were present. All of the AFS patients showed a degree of cross reactivity to 6 other fungi (20).
In a large study of 668 serum samples from patients which who had previously recorded at least one IgE positivity to fungal antigens, associations were observed between the patterns of IgE sensitization and fungal phylogenetic relationships. Using a panel of 17 fungal extracts including E. purpurascens, some samples were only positive to one fungal species, whereas many were multi-sensitized. The results suggest that the associations are likely due to antigen cross-reactivity between fungal species, not uncommon in more closely related species (21).
Compiled By
Author: RubyDuke Communications
Reviewer: Dr. Christian Fischer
Last reviewed:January 2022
References
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- Bisht V, Arora N, Singh BP, Pasha S, Gaur SN, Sridhara S. Epi p 1, an allergenic glycoprotein of Epicoccum purpurascens is a serine protease. FEMS Immunol Med Microbiol. 2004;42(2):205-11.
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