Table of Contents

Whole Allergen

m16 Curvularia lunata

m16 Curvularia lunata Scientific Information

Type:

Whole Allergen

Display Name:

Curvularia lunata

Allergen code:

m16

Family:

Pleosporaceae

Species:

lunata

Route of Exposure:

Inhalation

Latin Name:

Curvularia lunata

Other Names:

Cochliobolus lunatus; head mold of grasses, rice and sorghum

WHO/ICD-11 code:

XN93N

(ICD-11 is currently under implementation by WHO and the ICD-11 codes displayed in the encyclopedia may not yet be available in all countries)

Summary

Curvularia lunata (Cochliobolus lunatus) is a ubiquitous mold of the Order Pleosporales, mostly found in plant materials and soil worldwide. It is a known plant and human pathogen. The particles causing allergic reactions are spores found in the environment.

Asthma, allergic rhinitis, allergic Bronchopulmonary Mycosis and allergic fungal sinusitis are the main clinical presentations of C. lunata allergy. This mold is also able to cause opportunistic disease. Cross reactivity with other molds, especially if taxonomically close, may occur.

Allergen

Nature

The Genus Curvularia is a group of common fungi showing a wide range of interactions with other life forms, including pathogenic interactions with plants and humans (1). Curvularia lunata is found ubiquitously in soil (2); it is the anamorph (asexual form) of the fungus Cochliobolus lunatus (teleomorph, the sexual form) (3). In culture, C. lunata presents with brown colonies, producing brown septate conidiophores. The conidia also brown, constituted by 3–4 cells, straight or pyriform in shape; they may have a large and curved center, and range in size from 7 to 21 μm (4).

C. lunata is an agent of disease in plants, such as tomatoes (5), rice (6), crowfoot grass (7), sorghum (4, 8), sugar cane and corn (1).

There is considerable overlap between peak fungal activity season and other allergens such as grass and weed pollens, often masking the pathology caused by fungal spores in multi-sensitized people (9). Curvularia spp. spores were the fourth most commonly detected during a study spanning a 2-year period (around 5 of the total spores), and showed a distinct seasonality with peaks between July and October (10)

Taxonomy

*Taxonomic tree of Curvularia* genus (11)**
Domain	Eukaryota
Kingdom	Fungi
Phylum	Ascomycota
Subphylum	Pezizomycotina
Class	Dothideomycetes
Order	Pleosporales
Family	Pleosporaceae
Genus	Curvularia

Tissue

Spores release detectable amounts of allergens both prior to and following germination (9, 10, 12). The conidia (spores) are able to bind IgE (13). C. lunata spores were isolated from 83% of residences, predominantly from air filters (14).

Epidemiology

Worldwide distribution

Allergic diseases associated with Curvularia lunata have been described in many countries, including across South East Asia (Malaysia and Singapore) (15), Japan (16), North America (14), Australia (8) and India (10).

Environmental Characteristics

Worldwide distribution

Curvularia spp. can be found worldwide (3, 6).

Route of Exposure

Main

Inhalation of spores (9, 10).

Detection

Main methods

Personal volumetric petri plate sampler (10).

Measures

The concentrations of Curvularia spp. spores ranged between 78-246 CFU/m³ (10)

Clinical Relevance

Allergic rhinitis

In a study of 9,923 patients with a history of asthma, allergic rhinitis (AR) or atopic dermatitis (AD), sensitization to C. lunata (determined by skin-prick tests) significantly increased the risk of both asthma and AR, but not AD. The study also showed that C. lunata hypersensitivity was correlated with higher frequency of wheezing episodes, probability of attending a clinic and exacerbation of asthma symptoms (15).

Other diseases

A 25-year old patient with a history of bronchial asthma presented with a productive cough lasting several months; C. lunata was diagnosed as the cause of the allergic bronchopulmonary mycosis (16). This infection has also been described in two patients from an Australian report (McAleer 1981).

Curvularia lunata was frequently isolated from patients diagnosed with allergic fungal sinusitis (AFS) (14).

C. lunata can also cause disease in immunocompromised patients (17) and was described as the cause of a fatal cerebral infection in a 21-year old immunocompetent patient with a history of asthma (2).

Diagnostics Sensitization

The presence of allergen-specific antibodies is usually determined by skin prick tests (SPTs) and serology for IgE (9, 10). In a study carried out in atopic subjects, the incidence of mold allergy was 44%, with C. lunata one of the most frequently identified mold agents (18). In another study of 150 patients, SPT reactions to C. lunata allergens in patients with respiratory allergies varied in positivity, with 34% of patients showing mild to moderately positive reactions, 10.7% showing moderately positive reactions and 2% showing highly positive skin reactions (10). 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 69.2% concordance for C. lunata antigens when comparing the skin-prick tests and the ELISA in vitro immunoassay (10).

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 (9).

Prevention strategies

Avoidance is difficult to achieve (9), due to the wide range of environments in which C. lunata can be found (3).

Molecular Aspects

Allergenic molecules

A study identified four epitopes of C. lunata alcohol dehydrogenase (ADH), all of which were recognized by serum of patients with hypersensitivity to C. lunata (19). In another study, a 12 kDa protein was identified as C. lunata cytochrome c; skin reactivity tests showed positive reactions to this protein in 60% of mold-sensitized patients (20).An Alternaria alternata antigen, Alt a 1, has been identified in culture filtrates of C. lunata (21).

Cross-reactivity

Cross-reactivity has been demonstrated to other molds. In a study carried out on 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 C. lunata, 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 (22). Cross-reactivity was also demonstrated in immunoblots with an Epicoccum purpurascens 33.5 kDa allergen, Epi p 1 (23). An Alternaria alternata antigen, Alt a 1, has been demonstrated to show reactivity to specific serum of all species of the Pleosporaceae family (21). C. lunata cytochrome c, a 12kDa protein, showed cross-reactivity with other fungal allergens (20).

Compiled By

Author: RubyDuke Communications

Reviewer: Dr. Christian Fischer

Last reviewed:January 2022

References

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