Vacuolar Serine Protease Is a Major Allergen of Fusarium proliferatum and an IgE-Cross Reactive Pan-Fungal Allergen

Airborne indoor allergen serine proteases and their contribution to sensitisation and activation of innate immunity in allergic airway disease

Common airborne allergens (pollen, animal dander and those from fungi and insects) are the main triggers of type I allergic disorder in the respiratory system and are associated with allergic rhinitis, allergic asthma, as well as immunoglobulin E (IgE)-mediated allergic bronchopulmonary aspergillosis. These allergens promote IgE crosslinking, vasodilation, infiltration of inflammatory cells, mucosal barrier dysfunction, extracellular matrix deposition and smooth muscle spasm, which collectively cause remodelling of the airways. Fungus and insect (house dust mite and cockroaches) indoor allergens are particularly rich in proteases. Indeed, more than 40 different types of aeroallergen proteases, which have both IgE-neutralising and tissue-destructive activities, have been documented in the Allergen Nomenclature database. Of all the inhaled protease allergens, 85% are classed as serine protease activities and include trypsin-like, chymotrypsin-like and collagenolytic serine proteases. In this article, we review and compare the allergenicity and proteolytic effect of allergen serine proteases as listed in the Allergen Nomenclature and MEROPS databases and highlight their contribution to allergic sensitisation, disruption of the epithelial barrier and activation of innate immunity in allergic airways disease. The utility of small-molecule inhibitors of allergen serine proteases as a potential treatment strategy for allergic airways disease will also be discussed.

An evolutionary view of the Fusarium core genome

Fusarium, a member of the Ascomycota fungi, encompasses several pathogenic species significant to plants and animals. Some phytopathogenic species have received special attention due to their negative economic impact on the agricultural industry around the world. Traditionally, identification and taxonomic analysis of Fusarium have relied on morphological and phenotypic features, including the fungal host, leading to taxonomic conflicts that have been solved using molecular systematic technologies. In this work, we applied a phylogenomic approach that allowed us to resolve the evolutionary history of the species complexes of the genus and present evidence that supports the F. ventricosum species complex as the most basal lineage of the genus. Additionally, we present evidence that proposes modifications to the previous hypothesis of the evolutionary history of the F. staphyleae, F. newnesense, F. nisikadoi, F. oxysporum, and F. fujikuroi species complexes. Evolutionary analysis showed that the genome GC content tends to be lower in more modern lineages, in both, the whole-genome and core-genome coding DNA sequences. In contrast, genome size gain and losses are present during the evolution of the genus. Interestingly, core genome duplication events positively correlate with genome size. Evolutionary and genome conservation analysis supports the F3 hypothesis of Fusarium as a more compact and conserved group in terms of genome conservation. By contrast, outside of the F3 hypothesis, the most basal clades only share 8.8% of its genomic sequences with the F3 clade.

Safety evaluation of Fy Protein™ (Nutritional Fungi Protein), a macroingredient for human consumption

Fy Protein™ (Nutritional Fungi Protein) is a macro-ingredient produced from the fermentation of the fungal microorganism Fusarium strain flavolapis, isolated from springs in Yellowstone National Park. Fy Protein contains all of the essential amino acids plus fiber, fat, carbohydrates, vitamins, and minerals and is developed as an alternative to animal-based protein foods such as meat and dairy. Fy Protein's nutritional, digestibility, genotoxicity, allergenicity, toxicity, secondary metabolites, and pathogenicity were evaluated. Fy Protein did not show mutagenic or genotoxic potential in in vitro tests. In an allergenicity review, Fy Protein was found to be of low allergenic potential. In a 90-day sub chronic dietary study in rats, administration of Fy Protein did not produce any significant toxicologic manifestations, and the no observed effect level (NOAEL) was the highest-level fed of 150,000 ppm (15% in the diet). Regulated secondary metabolites from fungi (termed mycotoxins) were non-detectable and below regulated levels using quantitative analytical techniques. A literature review was completed to identify the potential human pathogenicity of Fusarium sp., showing that Fusarium rarely infects humans, with infections seldom developing even in immunocompromised individuals. The results of these studies confirm that Fy Protein from fermented F. str. flavolapis has low toxicological, genotoxic, pathogenic, and allergenic potential under the conditions tested and anticipated use.

Biochemical Characteristics and Allergenic Activity of Common Fungus Allergens

Fungi form a large kingdom with more than 1.5 million species. Fungal spores are universal atmospheric components and are generally recognized as important causes of allergic disorders, including allergic rhinitis, allergic rhinosinusitis, asthma, and allergic bronchopulmonary aspergillosis. The 4 genera which have the closest connection with allergic disorder are Cladosporium, Alternaria, Aspergillus and Penicillium. The cDNA sequences of many fungi allergens and the amino acids involved in their immunoglobulin E binding and T-cell activation have already been elucidated. Until now, 111 allergens from 29 fungal genera have been approved by the International Allergen Nomenclature Sub-committee. This review mainly focuses on the biochemical characteristics and allergenic activity of important allergens from common environmental fungi.

High prevalence of IgE sensitization against house dust mites in pregnant women

There is an increase in prevalence and financial burden of childhood atopic disorders in recent years. Understanding allergic conditions of pregnant women is important for developing strategies for prevention and management of allergy-related diseases. However, little is currently known about the atopic conditions in pregnant women.The sera from 46 pregnant women were analyzed for allergen-specific IgE antibodies using the Optigen assay and SDS-PAGE immunoblot analysis.Results from the Optigen assay showed that 20 (43%) of the 46 serum samples analyzed demonstrated IgE reactivity against mite p (Dermatophagoides pteronyssinus) (95%), mite f (D farinae) (95%), house dust (60%), cat (25%), shrimp (20%), crab (15%), cockroach (10%), dog (5%), latex (5%), willow black (5%), and timothy grass (5%). Nineteen of the 20 Optigen-positive sera demonstrated IgE reactivity against both the house dust mites D pteronyssinus and D farina, with 10 of them having a high IgE CLA class value of 4. IgE reactivity to the house dust mite D pteronyssinus was confirmed in SDS-PAGE-immunoblots, which correlated well with the intensity of IgE-binding to the 15-kDa D pteronyssinus component and to the purified recombinant Der p 2 major house dust mite allergen.A high prevalence of IgE sensitization against house dust mites during pregnancy is noted, which is worthy of clinical attention. Children of IgE-sensitized mothers should be closely monitored for development of allergenic disorders.

Immunoglobulin E-Mediated Autoimmunity

The study of autoimmunity mediated by immunoglobulin E (IgE) autoantibodies, which may be termed autoallergy, is in its infancy. It is now recognized that systemic lupus erythematosus, bullous pemphigoid (BP), and chronic urticaria, both spontaneous and inducible, are most likely to be mediated, at least in part, by IgE autoantibodies. The situation in other conditions, such as autoimmune uveitis, rheumatoid arthritis, hyperthyroid Graves’ disease, autoimmune pancreatitis, and even asthma, is far less clear but evidence for autoallergy is accumulating. To be certain of an autoallergic mechanism, it is necessary to identify both IgE autoantibodies and their targets as has been done with the transmembrane protein BP180 and the intracellular protein BP230 in BP and IL-24 in chronic spontaneous urticaria. Also, IgE-targeted therapies, such as anti-IgE, must have been shown to be of benefit to patients as has been done with both of these conditions. This comprehensive review of the literature on IgE-mediated autoallergy focuses on three related questions. What do we know about the prevalence of IgE autoantibodies and their targets in different diseases? What do we know about the relevance of IgE autoantibodies in different diseases? What do we know about the cellular and molecular effects of IgE autoantibodies? In addition to providing answers to these questions, based on a broad review of the literature, we outline the current gaps of knowledge in our understanding of IgE autoantibodies and describe approaches to address them.

Dectin-1-Mediated Pathway Contributes to Fusarium proliferatum-Induced CXCL-8 Release from Human Respiratory Epithelial Cells

Fusarium species are causative agents of human respiratory disorders and are distributed widely in our environment. Little is known of their interaction with human respiratory epithelial cells, which may contribute to allergic airway responses. In this study, we report on the release of C–X–C motif chemokine ligand 8 (CXCL-8) from human bronchial epithelial BEAS-2B cells upon stimulation with Fusarium proliferatum extracts. F. proliferatum-induced cytokine release from BEAS-2B cells was determined by cytokine array and CXCL-8 enzyme-linked immunosorbent assay (ELISA) kits. Blocking antibodies and signaling pathway inhibitors were employed to delineate cell surface receptors and signaling pathways participating in CXCL-8 release. F. proliferatum extracts induced the release of CXCL-8 in a time-dependent manner. The dectin-1 receptor ligands, curdlan and laminarin, reduced CXCL-8 release. Cells pre-treated with anti-Dectin-1 antibodies (2 µg/mL) decreased CXCL-8 release by 24%. Furthermore, F. proliferatum-stimulated CXCL-8 release was reduced by 32%, 53%–81%, 40% and 26% after BEAS-2B cells were pretreated with activation inhibitors of spleen tyrosine kinase (Syk)—piceatannol—, mitogen-activated protein kinases (MAPKs)—PD98059, U0126, SB202190, SP600125—, phosphatidylinositol-3-kinase (PI3K)—LY294002—and nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB)—BAY117082—, respectively. These results suggest that Dectin-1-mediated activation of the Syk, MAPKs, PI3K and NF-κB signaling pathways contributes to F. proliferatum-stimulated CXCL-8 release from BEAS-2B cells and provides an important basis for developing novel therapeutic strategies in clinical allergy.