Characterization of the 41kDa allergen Asp v 13, a subtilisin-like serine protease from Aspergillus versicolor

First Insight into the Degradome of Aspergillus ochraceus: Novel Secreted Peptidases and Their Inhibitors

Aspergillus fungi constitute a pivotal element within ecosystems, serving as both contributors of biologically active compounds and harboring the potential to cause various diseases across living organisms. The organism's proteolytic enzyme complex, termed the degradome, acts as an intermediary in its dynamic interaction with the surrounding environment. Using techniques such as genome and transcriptome sequencing, alongside protein prediction methodologies, we identified putative extracellular peptidases within Aspergillus ochraceus VKM-F4104D. Following manual annotation procedures, a total of 11 aspartic, 2 cysteine, 2 glutamic, 21 serine, 1 threonine, and 21 metallopeptidases were attributed to the extracellular degradome of A. ochraceus VKM-F4104D. Among them are enzymes with promising applications in biotechnology, potential targets and agents for antifungal therapy, and microbial antagonism factors. Thus, additional functionalities of the extracellular degradome, extending beyond mere protein substrate digestion for nutritional purposes, were demonstrated.

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.

Fungal bioaerosols as an occupational hazard

PURPOSE OF REVIEW

Over the past 40 years, the circumstances where fungal bioaerosols are major issues have shifted because of changes in the industrial sector from mainly agriculture to operations, including composting, cannabis production and forestry in hot humid conditions. Changes in the design and operation of nonindustrial workplaces meant that mould and dampness became major issues that are just being reduced. This review attempts to frame that history offers a perspective on the current thinking on mechanisms and provide potentially useful sources of information for physicians and their patients.

RECENT FINDINGS

The major impact of fungal exposures is not only from their allergens but also from an array of Danger-Associated Molecular Pattern molecules, possibly the most important of which is the type of glucan found in moulds that grow in damp buildings, wood chips and crops, that is beta 1, 3 D glucan in triple helical form. Located in lung epithelia, the dectin receptor is exquisitely sensitive to this compound. Except in some agricultural workplaces, low molecular weight secondary metabolites often mischaracterized as mycotoxins play little, if any, role on population health.

SUMMARY

There has been a convergence in thinking between the allergy and industrial hygiene communities as well as government agencies on mould and occupational health. This has led to some useful strategies for better managing these issues as well as increasing consumer awareness.

Seasonal diversity of biodeteriogenic, pathogenic, and toxigenic constituents of airborne mycobiota in a sacral environment

The main purpose of this study was to isolate airborne fungi and assess seasonal variations in air contamination with their particulates by determining the levels of their propagules in the nave and exonarthex of a church. We also monitored indoor microclimate as a determining factor for fungal proliferation on wall paintings, spore release, and transmission through the air. The temperature and relative humidity of the nave favoured fungal growth. A total of 33 fungi were isolated, mainly of the phylum Ascomycota, and to the lesser extent of the phyla Zygomycota and Basidiomycota. The most common were the fungi of the genera Penicillium and Aspergillus (23.55 % and 20.58 %, respectively). Sørensen's quotient of similarity (0.37) suggests moderate species overlap and constant exchange of fungal propagules between the nave and exonarthex. The autumn had the highest diversity, with 17 documented taxa, followed by the summer and the winter. The spring had only eight taxa. Quantitative analysis of the airborne mycobiota in the nave (430±84.85 to 1880±106.07 CFU m-3) and exonarthex (715±59.62 to 2295±91.92 CFU m-3) showed very high contamination throughout the year, with values exceeding the maximum permissible concentrations by most standards. Many of the fungi determined in this study are known for their biodeteriogenic, toxigenic, and allergenic properties, and are a threat not only to occasional visitors and staff, but also to valuable works of art decorating nave walls.

Taxonomy of Allergenic Fungi

The Kingdom Fungi contains diverse eukaryotic organisms including yeasts, molds, mushrooms, bracket fungi, plant rusts, smuts, and puffballs. Fungi have a complex metabolism that differs from animals and plants. They secrete enzymes into their surroundings and absorb the breakdown products of enzyme action. Some of these enzymes are well-known allergens. The phylogenetic relationships among fungi were unclear until recently because classification was based on the sexual state morphology. Fungi lacking an obvious sexual stage were assigned to the artificial, now-obsolete category, "Deuteromycetes" or "Fungi Imperfecti." During the last 20 years, DNA sequencing has resolved 8 fungal phyla, 3 of which contain most genera associated with important aeroallergens: Zygomycota, Ascomycota, and Basidiomycota. Advances in fungal classification have required name changes for some familiar taxa. Because of regulatory constraints, many fungal allergen extracts retain obsolete names. A major benefit from this reorganization is that specific immunoglobulin E (IgE) levels in individuals sensitized to fungi appear to closely match fungal phylogenetic relationships. This close relationship between molecular fungal systematics and IgE sensitization provides an opportunity to systematically look at cross-reactivity and permits representatives from each taxon to serve as a proxy for IgE to the group.

A new immunoassay to quantify fungal antigens from the indoor mould Aspergillus versicolor

Aspergillus versicolor is among the most commonly found moulds in moisture-damaged buildings and can be associated with adverse health effects in humans. This paper reports the development, validation and application of an enzyme immunoassay to quantify A. versicolor antigens. A sandwich ELISA was developed using polyclonal antibodies that recognize a broad range of A. versicolor proteins present in fungal spores and in mycelia fragments. To validate the new method, A. versicolor antigens were quantified in samples collected from homes with visible mould growth, including dust from vacuumed walls and bulk samples of building materials. Antigen concentrations were compared to the results of a commercial ELISA based on monoclonal antibodies (AveX ELISA, Indoor Biotechnologies, Charlottesville, USA) and correlated with colony forming units (CFU) of A. versicolor. The A. versicolor ELISA was very sensitive with a lower detection limit of 120 pg ml(-1). The assay also showed some reactivity to other moulds with strongest reactions with other Aspergillus species (1-3% reactivity). The new assay detected A. versicolor antigens in a much higher percentage of dust samples (88% vs. 27%) and bulk samples (89% vs. 24%) than the AveX assay. A significant correlation (r = 0.67, and p < 0.0001) was found between antigen concentrations and CFU of A. versicolor. Based on its low detection limit and good correlation with the culture-based method, this new immunoassay seems to be a useful tool for the measurement of A. versicolor exposure levels and a reliable complement to the traditional monitoring techniques, such as mould cultivation or microscopy.

Sta c 3 epitopes and their application as biomarkers to detect specific IgE

Sta c 3 was determined to be one of the major allergens from Stachybotrys chartarum sensu lato. This is among the most common fungi on wet building materials. Various cognizant authorities have found that mold and dampness are associated with exacerbation of asthma and increased upper respiratory disease. The primary amino-acid sequence of this allergen was reported, however the IgE-binding epitopes were unknown. Using SPOT-synthesis techniques (SPOTs), one main linear epitope located between V91 and G105 was discovered by Western blot with atopic human sera. This was confirmed by inhibition ELISA assays with both synthesized epitopes and natural Sta c 3. Alanine scanning also revealed R100 and K101 are the critical amino acids for IgE binding. Using the binding-enhanced and alanine substituted epitopes as potential biomarkers, a reverse ELISA method was developed to detect the Sta c 3 sIgE in atopic human sera. This method employed streptavidin-biotinylated mutated epitopes as the capture matrix, probing the possibility of using small peptides for allergen/species specific IgE assays.

Quantification of the Aspergillus versicolor allergen in house dust

Aspergillus versicolor, a fungus commonly found on damp building materials, produces the allergen, Asp v 13. Here we report a sensitive Asp v 13 capture ELISA for A. versicolor spores and spore- and mycelial fragments in house dust samples. The method is based on a double polyclonal capture ELSIA. The detection limits for Asp v 13 antigen and A. versicolor spores without dust were 2.44 pg and 12 ng (ca. 110 spores). Detection limits for Asp v 13 and A. versicolor spores in sieved house dust samples were 1.0 ng and 7.8 μg per gram dry weight house dust, respectively. This detection limit is lower than for other house dust allergen immunoassays including for Stachybotrys chartarum, Aspergillus fumigatus, but much lower than that from Alternaria alternata.