Type:
Whole Allergen
Whole Allergen
m207 Aspergillus niger
m207 Aspergillus niger Scientific Information
Display Name:
Aspergillus niger
Route of Exposure:
Respiratory
Family:
Trichocomaceae
Species:
niger
Latin Name:
Aspergillus niger
Other Names:
Aspergillus niger
Summary
Aspergillus niger is a filamentous fungus and is ubiquitous in the environment, in both the soil and as airborne spores. It is an economically important pathogen of crops and causes allergic and infectious diseases in humans. A niger allergens are important in occupational allergic disease and the pathophysiology of respiratory allergic disease, where there is a significant health burden. Exposure to the allergen is by the inhalational route. Although several A. niger specific allergenic proteins have been proposed, they are presently poorly understood. Cross-reactivity with other species of the Aspergillus genus is thought to be commonplace.
Allergen
Nature
Aspergillus niger is a filamentous ascomycete fungus that belongs to the Aspergillus genus, species of which are an important cause of disease in humans and animals (1). Aspergillus spp. are also an important plant pathogen, with spoilage due to Aspergillus spp. resulting in significant economic losses (2). The pathogenicity or Aspergillus spp. is linked to inherent thermotolerance, which confers an ability to germinate in lung tissue (3). Aspergillus fumigatus is the most prevalent pathogenic species of the genus (4). However, A. niger is more commonplace in the environment than A. fumigatus (5). A. niger is morphologically distinguished from other species in the genus with black conidial heads and relatively large conidia (3–5 µm) (4).
In common with other species in the genus, A. niger has a worldwide distribution (6). However, there is a geographical variance in the prevalence of Aspergillus spp. (6). A study from India showed that A. niger was the most prevalent airborne Aspergillus fungus (26.4%). In contrast, in Madrid it was 11%(6). This geographical variation is thought to be due to climate, local ecology, and degree of urbanization and pollution (6). Finally, the same study found a seasonal pattern of A. niger colony counts (6).
A. niger products are used in various industries, from biofuel to baking and animal feed additives and seed treating plants (7).
Taxonomy
Taxonomic tree of Aspergillus niger (5) |
|
|---|---|
Domain |
Eukaryote |
Kingdom |
Fungi |
Phylum |
Ascomycota |
Subphylum |
Pezizomycotina |
Class |
Eurotiomycetes |
Family |
Trichocomaceae |
Genus |
Aspergillus |
Taxonomic tree of Aspergillus niger (5) |
|---|
Epidemiology
Worldwide distribution
The incidence of Aspergillus sensitization in patients with allergic respiratory disease has been reported between 15.3%– 38.0 % (8) and a risk factor for a more severe clinical disease course (9). It is estimated that up to 70% of patients with severe asthma are sensitized to fungi, compared with 10% of patients with milder disease and 5% of the general population (10). For patients with cystic fibrosis (CF), a meta-analysis reported a pooled prevalence of sensitization to Aspergillus spp of 39.1%. It should be noted that observed prevalence was higher with skin prick test than specific IgE assay (11). ABPA occurs in approximately 7-9% of CF patients and 1-2% asthmatic patients (12).
A study from India (8) found a high proportion of patients with asthma were sensitized to A. niger, with 68.7% having A. niger specific circulating IgE and 14.7% returning positive skin prick test (8). Another study from the UK reported A. niger had a prevalence of 8% of the total positive fungal culture from patients with non-cystic bronchiectasis (3).
With its widespread use in industry, A. niger allergens are also a well-described pathogenic cause of occupational asthma (OA) and hypersensitivity pneumonitis (13), with baker’s and animal feed producers most at affected (14). One study showed that 87.5% (n=7/8) bakers had IgE raised against an A. niger allergen, xylosidase (7).
Environmental Characteristics
Living environment
A. niger, is a soil-living organism (2) and is a causative factor in hypersensitivity pneumonitis due to occupational exposure of greenhouse workers and horticulturalists. A niger has been isolated from diverse horticultural substrates, including Rockwool, peat and coco fibre, as well as being airborne (13). The evidence for A. niger causing allergic respiratory disease is documented in a small series of case studies (13).
Route of Exposure
Main
The primary route of exposure to A. niger is allergen inhalation (15). Aspergillus spp. have small conidiospores (2–5 µm), which means they can reach the terminal airways. However, their presence in the upper respiratory tract can also provoke a hypersensitivity reaction (6).
Clinical Relevance
The spectrum of allergic diseases caused by Aspergillosis species includes asthma (with or without rhinitis), allergic rhinosinusitis and hypersensitivity pneumonitis (5). The significance of hypersensitivity to Aspergillus spp. in the pathogenesis of asthma is well described. Patients with asthma sensitized to Aspergillus spp. are more likely to have more severe clinical signs (9). Although type III and IV hypersensitivity is implicated in mold allergy, the main burden of the disease is the consequence of type I hypersensitivity (3).
Severe disease is associated with increased morbidity and early mortality (3). The eosinophilic endotype associated with Aspergillus hypersensitivity is primarily seen in adults as late-onset asthma but can also be secondary to existing airway disease, such as cystic fibrosis (3).
Allergic bronchopulmonary aspergillosis (ABPA) is diagnosed when a specific set of clinical parameters are fulfilled (9), fixed airways obstruction, bronchiectasis, and lung fibrosis (3). ABPA can cause irreversible lung damage, and so there is an imperative to obtain a diagnosis as soon as practicable (15). Patients with ABPA are commonly sensitized to the Aspergillus fumigatus allergens, Asp f 1 and 2, which are helpful for diagnosis (15).
Molecular Aspects
Table adapted from Allergen.org (16)
Allergen name |
Protein group (if known) |
Size (kDa) |
|---|---|---|
Asp n 3 |
Perioxisomal Protein |
- |
Asp n 4 |
- |
- |
Asp n 14 |
Beta - xylosidase |
105 |
Asp n 18 |
Vacualoar serine protease |
34 |
Asp n 25 |
3-phytase B |
66-100 (84 Green & Beezhold, 2012) |
Asp n 26 |
Acidic Ribosomal Protein 1 |
- |
Asp n 30 |
Catalase |
- |
Asp n glucoasminase |
Glucosaminase |
68 (Green & Beezhold, 2012) |
Asp n Hemicellulase |
Xylanase |
22.6 (Green & Beezhold, 2021) |
Asp n Pectinase |
Pectinase |
- |
Allergen name |
Protein group (if known) |
Size (kDa) |
|---|
Allergenic molecules
The molecular basis of many A. niger allergens is well described in their context of occupational allergens. Glucoamylase, a dough additive used in industrial baking and production of high glucose syrups, has been reported to cause sensitization and OA. Furthermore, phytase, which is used in the manufacture of animal feed, is the allergen Asp n 25, as designated by the IUIS Allergen nomenclature committee. Phytase is highly sensitizing, and direct handling should be avoided (7).
The molecular characterization of Aspergillus allergens involved in the pathogenesis of ABPA is less well defined, in part because of lack of reagents, with only the A. fumigatus allergens Asp f 1-4 and Asp f 6 commercially available for diagnostic testing. There remains at present little information about the role of A. niger allergens in the pathogenicity of ABPA (3). However, a serine protease (Asp n 18) has been proposed as a potential major allergen (1).
Cross-reactivity
There is evidence of significant cross-reactivity between allergens of different Aspergillus spp. (15) and it has been proposed that for many patients with ABPA who are positive for A fumigatus specific IgE, their clinical signs may be caused by another member of the Aspergillus genus Although co-sensitization to both Aspergillus species may have occurred simultaneously (17).
A study has shown that all patients positive to IgEs specific to A. niger, A. flavus or A. terreus also had A. fumigatus specific IgE. However, it is thought that A. niger is less cross-antigenic with A. fumigatus than A. flavus (15). It has also been shown that A. niger has no cross-reactivity with Alternaria alternata, a clinically significant cause of fungal hypersensitivity (18).
Compiled By
Author: RubyDuke Communications
Reviewer: Dr. Christian Fischer
Last reviewed: December 2022
References
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- Twaroch TE, Curin M, Sterflinger K, Focke-Tejkl M, Swoboda I, Valenta R. Specific Antibodies for the Detection of Alternaria Allergens and the Identification of Cross-Reactive Antigens in Other Fungi. Int Arch Allergy Immunol. 2016;170(4):269-78.
