Fungal Allergen and Mold Allergy Diagnosis: 2nd Edition

Dear Colleagues,

Allergic diseases are a group of immunological conditions affecting 30% of the general population, and their rates are increasing dramatically. Asthma, rhinitis, and cutaneous and food disorders are the main groups included in allergic conditions. The main allergens causing type I allergies are contained in different sources, of which mites, pollens, epithelia, fungi and some foods are the most important.

Fungi are the fourth most common source of sensitization involved in respiratory allergy. Exposure to allergenic molds can cause IgE-mediated allergic rhinitis, asthma and atopic dermatitis, and it has been described that the sensitization to some fungi such as Aspergillus and/or Alternaria is related to the severity of an asthmatic arrest.

For a correct diagnosis of allergy, patient selection is crucial, and the basis for this is, first, an accurate clinical history, including imaging when appropriate, and in vivo and in vitro methods to define the etiological diagnosis. Provocation tests and skin tests have from the beginning been the main workhorses for the diagnosis of allergic diseases and offer quick and accurate results in the doctor´s office.

Complementary laboratory allergy methods are currently the main etiological diagnosis testing techniques to demonstrate the allergenic source or the allergenic components that are involved in IgE-mediated allergic disease. Enzyme immunoassays and basophil degranulation tests are the main methods used for this.

In recent decades, the development and application of the concept of molecular diagnostics to the field of allergy has been an important milestone in the development and modernization of IgE-mediated allergy diagnosis. Research into individualized allergens and their possible role in the development of allergies has been the basis for the application of this concept, which has now become undeniably established, especially in the diagnosis of food allergy.

Unlike other pneumoallergens, fungi can not only cause type I respiratory allergy but also other types of respiratory diseases, such as allergic bronchopulmonary mycoses, hypersensitivity pneumonitis and pulmonary mycosis. Fungal respiratory diseases present themselves as a heterogeneous group of conditions due to the diversity of existing fungal species, their ability to establish themselves on a wide range of substrates and their diversity of roles in human pathology. All of these conditions make this group of allergens a limited and difficult field of study, which means that both fungi and fungal allergy remain largely neglected in both basic research and clinical practice.

Out of more than 150,000 fungal species described to date (new DNA sequencing technologies estimate the number of fungal species to range from 3 to 13 million species), the existing data only refer to slightly less than a hundred genera that have been described as allergenic sources and to more than 200 individualized allergens belonging to 24 fungal genera. From them, just 120 individualized allergens belong to 31 fungal species and 16 genera. Some allergen proteins belonging to Alternaria alternata, Aspergillus fumigatus and Cladosporium herbarum are the most widely used for diagnostic proposals but, of course, are clearly insufficient.

Like in other disciplines, we are experiencing new data on the development of new biological tools, new molecules and combinations that may offer interesting alternatives for the diagnosis and treatment of specific subtypes of asthma and related diseases. Recent advances in diagnostic approaches, biomarker development and the use of “omics” technologies have greatly improved this field, demonstrating an increasing potential to detect new clinically relevant allergy parameters and risk factors, as well as to predict and monitor the therapeutic success in the future.

Allergen cross-reactivity and fungal phylogenetic advances will be relevant key factors in the development of fungal allergy.

In the same way, the exponential progress of new methodologies including microarrays, mass cytometry and spectrometry, basophil activation testing, cellular immunology, next-generation "omics" technologies, the development of automated systems and new software solutions to aid in the interpretation of allergy diagnostics is generating enormous enabling data sets that are key to expanding the knowledge required and leading the way for the future development of the diagnosis and treatment of fungal allergic diseases.

Prof. Dr. Jorge Martínez Quesada
Prof. Dr. Idoia Postigo
Guest Editors

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