Alternaria alternata allergens: Markers of exposure, phylogeny and risk of fungi-induced respiratory allergy

Analysis of culturable airborne fungi in outdoor environments in Tianjin, China

Background

Fungal spores dispersed in the atmosphere may become cause of different pathological conditions and allergies for human beings. A number of studies have been performed to analyze the diversity of airborne fungi in different environments worldwide, and in particular in many urban areas in China. We investigated, for the first time, the diversity, concentration and distribution of airborne fungi in Tianjin city. We sampled 8 outdoor environments, using open plate method, during a whole winter season. Isolated fungi were identified by morphological and molecular analysis. Environmental factors which could influence the airborne fungi concentration (temperature, humidity, wind speed, and air pressure) were monitored and analyzed. The effect of different urban site functions (busy areas with high traffic flow and commercial activities vs. green areas) on airborne fungal diversity was also analyzed.

Results

A total of 560 fungal strains, belonging to 110 species and 49 genera of Ascomycota (80 %), Basidiomycota (18 %), and Mucoromycota (2 %) were isolated in this study. The dominant fungal genus was Alternaria (22 %), followed by Cladosporium (18.4 %), Naganishia (14.1 %), Fusarium (5.9 %), Phoma (4.11 %), and Didymella (4.8 %). A fungal concentration ranging from 0 to 3224.13 CFU m^− 3 was recorded during the whole study. Permutational multivariate analysis showed that the month was the most influential factor for airborne fungal community structure, probably because it can be regarded as a proxy of environmental variables, followed by wind speed. The two analyzed environments (busy vs. green) had no detectable effect on the air fungal community, which could be related to the relatively small size of parks in Tianjin and/or to the study season.

Conclusions

Our study shed light on the highly diverse community of airborne fungi characterizing the outdoor environments of Tianjin, and clarified the role that different environmental factors played in shaping the analyzed fungal community. The dominant presence of fungi with potential hazardous effect on human health, such as Alternaria, Cladosporium and Naganishia, deserves further attention. Our results may represent a valuable source of information for air quality monitoring, microbial pollution control, and airborne diseases prevention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02205-2.

The airborne mycobiome and associations with mycotoxins and inflammatory markers in the Norwegian grain industry

Grain dust exposure is associated with respiratory symptoms among grain industry workers. However, the fungal assemblage that contribute to airborne grain dust has been poorly studied. We characterized the airborne fungal diversity at industrial grain- and animal feed mills, and identified differences in diversity, taxonomic compositions and community structural patterns between seasons and climatic zones. The fungal communities displayed strong variation between seasons and climatic zones, with 46% and 21% of OTUs shared between different seasons and climatic zones, respectively. The highest species richness was observed in the humid continental climate of the southeastern Norway, followed by the continental subarctic climate of the eastern inland with dryer, short summers and snowy winters, and the central coastal Norway with short growth season and lower temperature. The richness did not vary between seasons. The fungal diversity correlated with some specific mycotoxins in settled dust and with fibrinogen in the blood of exposed workers, but not with the personal exposure measurements of dust, glucans or spore counts. The study contributes to a better understanding of fungal exposures in the grain and animal feed industry. The differences in diversity suggest that the potential health effects of fungal inhalation may also be different.

Gut mycobiota alterations in patients with COVID-19 and H1N1 infections and their associations with clinical features

The relationship between gut microbes and COVID-19 or H1N1 infections is not fully understood. Here, we compared the gut mycobiota of 67 COVID-19 patients, 35 H1N1-infected patients and 48 healthy controls (HCs) using internal transcribed spacer (ITS) 3-ITS4 sequencing and analysed their associations with clinical features and the bacterial microbiota. Compared to HCs, the fungal burden was higher. Fungal mycobiota dysbiosis in both COVID-19 and H1N1-infected patients was mainly characterized by the depletion of fungi such as Aspergillus and Penicillium, but several fungi, including Candida glabrata, were enriched in H1N1-infected patients. The gut mycobiota profiles in COVID-19 patients with mild and severe symptoms were similar. Hospitalization had no apparent additional effects. In COVID-19 patients, Mucoromycota was positively correlated with Fusicatenibacter, Aspergillus niger was positively correlated with diarrhoea, and Penicillium citrinum was negatively correlated with C-reactive protein (CRP). In H1N1-infected patients, Aspergillus penicilloides was positively correlated with Lachnospiraceae members, Aspergillus was positively correlated with CRP, and Mucoromycota was negatively correlated with procalcitonin. Therefore, gut mycobiota dysbiosis occurs in both COVID-19 patients and H1N1-infected patients and does not improve until the patients are discharged and no longer require medical attention.

Lv et al. associate the gut mycobiota with clinical features and the bacterial microbiota by comparing COVID-19 patients to those infected with H1N1 and healthy controls. They find that gut mycobiota dysbiosis occurs in both COVID-19 patients and those infected with H1N1 and that it does not improve until patients no longer require medical attention, providing insights into a better healthcare guideline.

Characterization of fungal aerosol in a landfill and an incineration plants in Guangzhou, Southern China: The link to potential impacts

To understand the characteristics and potential impacts of fungal aerosols in waste disposal treatments, we performed observations at a landfill and an incineration plants in Guangzhou, Southern China. Size-segregated airborne fungal concentrations were measured based on culture-dependent method, and fungal compositions in PM_2.5 were obtained using high-throughput sequencing method. Concentrations of airborne fungi varied from 376 to 9318 CFU/m³ in the landfill plant and from 53 to 8491 CFU/m³ in the incineration plant, respectively. The temporal and spatial variations of fungal aerosols indicate that waste disposal operation, garbage transport, air mixing, and meteorological factors can significantly influence the variations of airborne fungi in the outdoor environment in both plants. Among the meteorological factors, light/moderate rain could significantly increase the airborne fungal concentrations while heavy rain could decrease the concentrations due to wet scavenge. We observed that culturable fungal aerosols predominantly resided in the size range of 2.1-3.3 μm. Different fungal community structures in PM_2.5 were found between the landfill and the incineration plants, suggesting the influence of different waste sorts and treatment procedures. We further identified the pathogenic/allergenic fungal taxa (e.g., Alternaria, Epicoccum sp. and Stachybotrys sp.) in the two plants, implying the potential human health risks with long-term exposure for on-site workers and surrounding residents. The fungal genera producing microbial volatile organic compounds (MVOCs, e.g., Cladosporium, Fusarium sp., Penicillium sp. and Candida) were found in both plants. These MVOCs generation related fungal genera could contribute to the odor in the plants and, more importantly, affect the downwind area after aerosolization and transportation.

Atopic Dermatitis and Sensitisation to Molecular Components of Alternaria, Cladosporium, Penicillium, Aspergillus, and Malassezia-Results of Allergy Explorer ALEX 2

Progress in laboratory diagnostics of IgE-mediated allergies is being made through the use of component-resolved diagnosis. The aim of our study is to analyze the sensitization profile to allergen reagents in patients suffering from atopic dermatitis with the use of the ALEX 2–Allergy Explorer and especially to show the sensitization to molecular components of molds and yeast. The complete dermatological and allergological examination including the examination of the sensitization to allergen reagents with Allergy Explorer ALEX 2 testing was performed. The relation between the sensitization to molecular components of molds and yeast and the severity of atopic dermatitis, and the occurrence of bronchial asthma and allergic rhinitis was evaluated. Altogether, 100 atopic dermatitis patients were examined—48 men and 52 women, with an average age of 40.9 years. The sensitization to Mala s 6, Mala s 11, Sac c, Asp f 6, Cla h and Cla h 8 correlates to the severity of atopic dermatitis. The sensitization to Sac c, Alt a 6, Cla h, Cla h 8 was observed significantly more frequently in patients suffering from bronchial asthma to Mala s 6 in patients suffering from allergic rhinitis. In patients with severe form of atopic dermatitis (AD), a very high level of specific IgE was recorded to Mala s 11 (in 36%) and to Asp f 6 (in 12%).

Enhancement in serum (1-3)-β-D-glucan level by cutaneous alternariosis: A case report and literature review

Contamination with the fungus Alternaria spp. is often considered to have originated from laboratory sources, which occasionally causes infection in immunocompromised patients, termed as phaeohyphomycosis. Here, we have reported a case of cutaneous alternariosis caused by Alternaria alternata. This diagnosis was based on microscopic examination and mycological culturing of patient's vesicular lesions, with the use of 5 molecular markers (namely, ITS, ATPase, Actin, rpb2, and tef1) for strain identification. We noted that Alternaria infection caused an increase in the serum level of (1-3)-β-D-glucan (BG) in the patients. To the best of our knowledge, no such finding has been reported in previously in the literature.

Sensitization to Molecular Components in 104 Atopic Dermatitis Patients in Relation to Subgroups of Patients Suffering from Bronchial Asthma and Allergic Rhinitis

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease. The progression from AD to bronchial asthma (AB) and allergic rhinitis (AR) is called atopic march. The aim of this study was to evaluate the difference in the sensitization to molecular components in patients suffering from AD in relation to subgroups of patients with AR and AB.

MATERIAL AND METHODS

The complete dermatological and allergological examinations were performed. Specific IgE antibodies against 112 molecular components were measured with the multiplex ImmnoCAP ISAC test.

RESULTS

Altogether 104 atopic dermatitis patients (50 men, 54 women) at the average age 40.1 years were examined. The sensitization to molecular components was confirmed in 93.3% of patients. The sensitization to components of mites, grasses, trees, animals, moulds, and shrimps was significantly more frequent in patients with severe form of AD and the sensitization to components of grasses, trees, and moulds was significantly higher in subgroup of patients with AB. In subgroup of patients suffering from AR the higher occurrence of pollen-derived and pollen-food derived PR-10 proteins, grasses, mites, and animals was observed also.

CONCLUSIONS

We have confirmed the significant differences in the sensitization to molecular components in patients suffering from severe form of AD, and in subgroups of patients suffering from AB and AR. These molecular components may play the important role in the consecutive development of different allergy pathologies called atopic march.

Microbial communities and gene contributions in smokeless tobacco products

Smokeless tobacco products (STP) contain bacteria, mold, and fungi due to exposure from surrounding environments and tobacco processing. This has been a cause for concern since the presence of microorganisms has been linked to the formation of highly carcinogenic tobacco-specific nitrosamines. These communities have also been reported to produce toxins and other pro-inflammatory molecules that can cause mouth lesions and elicit inflammatory responses in STP users. Moreover, microbial species in these products could transfer to the mouth and gastrointestinal tract, potentially altering the established respective microbiotas of the consumer. Here, we present the first metagenomic analysis of select smokeless tobacco products, specifically US domestic moist and dry snuff. Bacterial, eukaryotic, and viral species were found in all tobacco products where 68% of the total species was comprised of Bacteria with 3 dominant phyla but also included 32% Eukarya and 1% share abundance for Archaea and Viruses. Furthermore, 693,318 genes were found to be present and included nitrate and nitrite reduction and transport enzymes, antibiotic resistance genes associated with resistance to vancomycin, β-lactamases, their derivatives, and other antibiotics, as well as genes encoding multi-drug transporters and efflux pumps. Additional analyses showed the presence of endo- and exotoxin genes in addition to other molecules associated with inflammatory responses. Our results present a novel aspect of the smokeless tobacco microbiome and provide a better understanding of these products' microbiology. KEY POINTS: • The findings presented will help understand microbial contributions to overall STP chemistries. • Gene function categorization reveals harmful constituents outside canonical forms. • Pathway genes for TSNA precursor activity may occur at early stages of production. • Bacteria in STPs carry antibiotic resistance genes and gene transfer mechanisms.

Preliminary Studies on Fungal Contamination of Two Rupestrian Churches from Matera (Southern Italy)

The Sassi, a UNESCO World Heritage Site and its rupestrian churches, are richly decorated and visited by thousands of visitors every year. It is important to preserve this heritage which shows signs of deterioration due to abiotic and/or biotic factors. Aiming to carry out in the future an environmental-friendly restoration, a screening of the fungi present on walls and frescoes of two rupestrian churches “Santa Lucia alle Malve” and “La Madonna dei derelitti” located, respectively, in the “Sasso Caveoso” and in the “Sasso Barisano” was performed. Isolation and characterization of fungal species from investigated sites was carried out. Total genomic DNA (gDNA) was extracted from pure fungal cultures and subsequently utilized in PCRs using primers that amplify a portion of the ribosomal DNA (ITS5/ITS4) or the β-tubulin gene (Bt2a/Bt2b). The amplicons were directly sequenced. Obtained nucleotide sequences were compared to those present in the GenBank (NCBI) showing a very high similarity (99–100%) with the following species: Parengyodontium album, Alternaria alternata, Cladosporium cladosporioides, Lecanicillium psalliotae, Meyerozyma guilliermondii and Botryotrichum atrogriseum. All sequences from this study were deposited in the EMBL database. Detailed knowledge about fungi isolated from stone is indispensable not only to counter/reduce the structural and aesthetic damage but also to protect the health of both guardians and visitors who may develop different pathologies due to the spores diffused in the environment.

Occurrence of various pathogenic and opportunistic fungi in skin diseases of domestic animals: a retrospective study

Background

Fungal infection of animals or humans are common all over the world. Some of microorganisms like fungi, exist on the skin and can be transmitted onto other individuals, other animal species or even humans and cause skin infections. Moreover, they can be the causative agents of severe generalized infections especially in immunocompromised individuals. The study aimed to evaluate the most frequent etiological agents of skin diseases and to compare the prevalence of animal fungal infections in Poland, and to discuss the possibility of transmission to humans in Poland.

Results

The obtained results are culture based. The fungi most frequently isolated from group of animals with skin lesions were Malassezia pachydermatis (29.14%), and Candida yeasts (27.07%), and dermatophytes (23.5%), including Microsporum canis as majority of them (59.25%), and Trichophyton genus (40.7%), most of them T. mentagrophytes, while Malassezia pachydermatis represented (80%) of isolates in animals with otitis externa. In over 19% of positive fungal cultures obtained from external ear canals Candida yeasts, mainly C. albicans, were identified.

Conclusions

Dermatomycoses in companion animals are caused by both, mycelial fungi and yeasts. Most frequently isolated were Malassezia pachydermatis and Candida spp. Dermatophytes (Trichophyton, Microsporum), were also cultured, but the total number of these isolates seems to decrease. We have not found Cryptococcus neoformans in tested clinical samples.

Fungal Pathogens Affecting the Production and Quality of Medical Cannabis in Israel

The use of and research on medical cannabis (MC) is becoming more common, yet there are still many challenges regarding plant diseases of this crop. For example, there is a lack of formal and professional knowledge regarding fungi that infect MC plants, and practical and effective methods for managing the casual agents of disease are limited. The purpose of this study was to identify foliar, stem, and soilborne pathogens affecting MC under commercial cultivation in Israel. The predominant major foliage pathogens were identified as Alternaria alternata and Botrytis cinerea, while the common stem and soilborne pathogens were identified as Fusarium oxysporum and F. solani. Other important fungi that were isolated from foliage were those producing various mycotoxins that can directly harm patients, such as Aspergillus spp. and Penicillium spp. The sampling and characterization of potential pathogenic fungi were conducted from infected MC plant parts that exhibited various disease symptoms. Koch postulates were conducted by inoculating healthy MC tissues and intact plants with fungi isolated from infected commercially cultivated symptomatic plants. In this study, we report on the major and most common plant pathogens of MC found in Israel, and determine the seasonal outbreak of each fungus.

Structural Similarity with Cholesterol Reveals Crucial Insights into Mechanisms Sustaining the Immunomodulatory Activity of the Mycotoxin Alternariol

The proliferation of molds in domestic environments can lead to uncontrolled continuous exposure to mycotoxins. Even if not immediately symptomatic, this may result in chronic effects, such as, for instance, immunosuppression or allergenic promotion. Alternariol (AOH) is one of the most abundant mycotoxins produced by Alternaria alternata fungi, proliferating among others in fridges, as well as in humid walls. AOH was previously reported to have immunomodulatory potential. However, molecular mechanisms sustaining this effect remained elusive. In differentiated THP-1 macrophages, AOH hardly altered the secretion of pro-inflammatory mediators when co-incubated with lipopolysaccharide (LPS), opening up the possibility that the immunosuppressive potential of the toxin could be related to an alteration of a downstream pro-inflammatory signaling cascade. Intriguingly, the mycotoxin affected the membrane fluidity in macrophages and it synergistically reacted with the cholesterol binding agent MβCD. In silico modelling revealed the potential of the mycotoxin to intercalate in cholesterol-rich membrane domains, like caveolae, and immunofluorescence showed the modified interplay of caveolin-1 with Toll-like Receptor (TLR) 4. In conclusion, we identified the structural similarity with cholesterol as one of the key determinants of the immunomodulatory potential of AOH.

The Pathogenesis of Fungal-Related Diseases and Allergies in the African Population: The State of the Evidence and Knowledge Gaps

The prevalence of allergic diseases in the African continent has received limited attention with the allergic diseases due to fungal allergens being among the least studied. This lead to the opinion being that the prevalence of allergic disease is low in Africa. Recent reports from different African countries indicate that this is not the case as allergic conditions are common and some; particularly those due to fungal allergens are increasing in prevalence. Thus, there is need to understand both the aetiology and pathogenies of these diseases, particularly the neglected fungal allergic diseases. This review addresses currently available knowledge of fungal-induced allergy, disease pathogenesis comparing findings from human versus experimental mouse studies of fungal allergy. The review discusses the potential role of the gut mycobiome and the extent to which this is relevant to fungal allergy, diagnosis and human health.

Mycotoxin Altertoxin II Induces Lipid Peroxidation Connecting Mitochondrial Stress Response to NF-κB Inhibition in THP-1 Macrophages

Prolonged exposure to mycotoxins, even in subtoxic concentrations, might contribute to modulate pro- or anti-inflammatory cascades and ultimately have long-term consequences on our health. In line, there is an increasing need to describe and comprehend the potential immunomodulatory effects of toxins that can be produced from fungi proliferating even in a domestic environment like, for instance, Alternaria alternata. Taking this as a starting point, we investigated the effects of one of the most potent genotoxic compounds produced by this fungi type, namely altertoxin II (ATXII) on THP-1 macrophages. In noncytotoxic concentrations (0.1-1 μM), ATXII inhibited the activation of the transcription factor NF-κB, and this event was accompanied by significant mitochondrial superoxide production (1 μM ATXII). Both responses seemed dependent on membrane structure and morphology since they were modulated by the coincubation with the cholesterol complexing agent methyl-β-cyclodextrin (MβCD, 10-50 μM). Moreover, toxicity of ATXII was enhanced by cholesterol load (cholesterol-MβCD). The mycotoxin induced also lipid peroxidation (1-10 μM, ATXII) possibly streaming down at the mitochondrial level and suppressing NF-κB activation in THP-1 macrophages.

Gene profiling and expression of major allergen Alt a 1 in Alternaria alternata and related members of the Pleosporaceae family

BACKGROUND

Members of the Pleosporaceae family are known as important sources of airborne allergens which are responsible for asthma and allergic diseases.

AIMS

The purpose of this study was to investigate the gene profiling and expression pattern of Alt a 1 in Alternaria alternata and other members of the Pleosporaceae family including Stemphylium botryosum, Ulocladium chartarum, Curvularia lunata, Cladosporium cladosporioides, and Epicoccum nigrum.

METHODS

Alternaria alternata and related genera were cultured on Czapek-Dox broth medium at 25°C for 21 days. The presence of Alt a 1 was assessed in fungal culture filtrates by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and then confirmed by immunoblot analysis. Real-time PCR was carried out for quantitation of the Alt a 1 gene encoding corresponding protein at the transcriptional level using cDNA prepared from fungal RNA.

RESULTS

SDS-PAGE showed protein bands ranging from 14 to 100kDa. A 14kDa band corresponding to Alt a 1 was present in A. alternata, S. botryosum and U. chartarum. The gene expression of Alt a 1 was reported in A. alternata and some other related genera. The C_t mean value recorded for A. alternata strains ranged from 24.70 to 27.84 while it was in the range 23.62-32.09 for other related taxa. No apparent transcription or expression was revealed in C. cladosporioides.

CONCLUSIONS

The presence and efficient expression of Alt a 1 gene in A. alternata and other related taxa indicate that Alt a 1 protein is a major component of the secretory machinery of Pleosporaceae family members, and it may play a crucial role in its allergenicity.

Interaction of Alt a 1 with SLC22A17 in the airway mucosa

BACKGROUND

Despite all the efforts made up to now, the reasons that facilitate a protein becoming an allergen have not been elucidated yet. Alt a 1 protein is the major fungal allergen responsible for chronic asthma, but little is known about its immunological activity. Our main purpose was to investigate the ligand-dependent interactions of Alt a 1 in the human airway epithelium.

METHODS

Alt a 1 with and without its ligand (holo- and apo- forms) was incubated with the pulmonary epithelial monolayer model, Calu-3 cells. Allergen transport and cytokine production were measured. Pull-down and immunofluorescence assays were employed to identify the receptor of Alt a 1 using the epithelial cell model and mouse tissues. Receptor-allergen-ligand interactions were analyzed by computational modeling.

RESULTS

The holo-form could activate human monocytes, PBMCs, and polarized airway epithelial (Calu-3) cell lines. The allergen was also transported through the monolayer, without any alteration of the epithelial integrity (TEER). Alt a 1 also induced the production of proinflammatory IL8 and specific epithelial cytokines (IL33 and IL25) by Calu-3 cells. The interaction between epithelial cells and holo-Alt a 1 was found to be mediated by the SLC22A17 receptor, and its recognition of Alt a 1 was explained in structural terms.

CONCLUSIONS

Our findings identified the Alt a 1 ligand as a central player in the interaction of the allergen with airway mucosa, shedding light into its potential role in the immunological response, while unveiling its potential as a new target for therapy intervention.

Effect Of Dual sEH/COX-2 Inhibition on Allergen-Induced Airway Inflammation

Arachidonic acid metabolites resulting from the cyclooxygenase (COX), lipoxygenase, and cytochrome P450 oxidase enzymatic pathways play pro- and anti-inflammatory roles in allergic airway inflammation (AAI) and asthma. Expression of COX-2 and soluble epoxide hydrolase (sEH) are elevated in allergic airways and their enzymatic products (e.g., prostaglandins and diols of epoxyeicosatrienoic acids, respectively) have been shown to participate in the pathogenesis of AAI. Here, we evaluated the outcome of inhibiting the COX-2 and sEH enzymatic pathways with a novel dual inhibitor, PTUPB, in A. alternata-induced AAI. Allergen-challenged mice were administered with 10 or 30 mg/kg of PTUPB, celecoxib (selective COX-2 inhibitor), t-TUCB (selective sEH inhibitor) or vehicle daily by gavage and evaluated for various features of AAI. PTUPB and t-TUCB at 30 mg/kg, but not celecoxib, inhibited eosinophilic infiltration and significantly increased levels of anti-inflammatory EETs in the lung tissue of allergen-challenged mice. t-TUCB significantly inhibited allergen-induced IL-4 and IL-13, while a less pronounced reduction was noted with PTUPB and celecoxib. Additionally, t-TUCB markedly inhibited eotaxin-2, an eosinophil-specific chemokine, which was only marginally reduced by PTUPB and remained elevated in celecoxib-treated mice. PTUPB or t-TUCB administration reversed allergen-induced reduction in levels of various lipid mediators in the lungs, with only a minimal effect noted with celecoxib. Despite the anti-inflammatory effects, PTUPB or t-TUCB did not reduce allergen-induced airway hyperresponsiveness (AHR). However, development of structural changes in the allergic airways, such as mucus hypersecretion and smooth muscle hypertrophy, was significantly inhibited by both inhibitors. Celecoxib, on the other hand, inhibited only airway smooth muscle hypertrophy, but not mucus hypersecretion. In conclusion, dual inhibition of COX-2 and sEH offers no additional advantage relative to sEH inhibition alone in attenuating various features associated with A. alternata-induced AAI, while COX-2 inhibition exerts only moderate or no effect on several of these features. Dual sEH/COX-2 inhibition may be useful in treating conditions where eosinophilic inflammation co-exists with pain-associated inflammation.

Genome Sequence Resource for Stemphylium vesicarium, Causing Brown Spot Disease of Pear

Stemphylium vesicarium is the causal agent of several plant diseases as well brown spot of pear (BSP), which is one of the most economically important fungal diseases in European pear-production areas. In addition to the relevance of the economic impact, conidia spread widely from plant material infected by the pathogen can trigger respiratory allergy. Here, we report the first genome of a S. vesicarium strain, 173-1a13FI1M3, isolated from pear and sensitive to the mostly used fungicide classes currently authorized in Europe against BSP. The availability of this draft genome could represent a first important step in understanding the physiology and the infection mechanism of the pathogen. Furthermore, this contribution could be fundamental in order to design more effective and sustainable strategies to control the disease.

Molecular identification and genetic variation of Alternaria species isolated from tomatoes using ITS1 sequencing and inter simple sequence repeat methods

Background and Purpose:

Alternaria is one of the most abundant fungi that exists in numerous places around the world. This saprophytic fungus causes diseases in plants and accounts for the spoilage of cereals in warehouses. The aim of this study was to identify Alternaria isolates based on their morphological characteristics and internal transcribed spacer ribosomal RNA (ITS rRNA) sequencing method. To this end, genetic diversity in the isolates was also examined using inter simple sequence repeat (ISSR) markers.

Materials and Methods:

To conduct this research, a total of 60 tomato samples with black spots were collected from supermarkets in Khorramabad City, Iran, in the winter of 2017. The specimens were cultured on a potato dextrose agar medium. After the purification of the fungus by the single-spore method, the identification of the species was carried out using morphological characteristics and ITS rRNA sequencing by polymerase chain reaction. The genetic diversity of the identified species with four primers was evaluated using the ISSR marker.

Results:

Based on the sequencing of the ITS1 region, all the isolates were identified as A. alternata. Cluster diagrams for the ISSR marker were classified into six distinct groups. The mean polymorphism information content was obtained as 0.35, indicating the effectiveness of the primers in the separation of the isolates.

Conclusion:

The sequencing of ITS1 led to the identification of Alternaria species that are morphologically similar. The production of various mycotoxins by A. Alternata species leads to the contamination of livestock and human food. Regarding this, the investigation of the genetic diversity of A. alternata species using the ISSR marker would facilitate the identification of suitable and effective strategies for controlling the fungal and mycotoxin contamination of human nutrition.

Similar immune mechanisms control experimental airway eosinophilia elicited by different allergens and treatment protocols

Background

Mouse models have been extremely valuable in identifying the fundamental mechanisms of airway inflammation that underlie human allergic asthma. Several models are commonly used, employing different methods and routes of sensitisation, and allergens of varying clinical relevance. Although all models elicit similar hallmarks of allergic airway inflammation, including airway eosinophilia, goblet cell hyperplasia and cellular infiltration in lung, it is not established whether they do so by involving the same mechanisms.

Results

We compared the impact of inactivation of various innate or adaptive immune genes, as well as sex, in different models of allergic airway inflammation in mice of C57BL/6 background. Chicken ovalbumin (OVA) and house dust mite (HDM) were used as allergens in settings of single or multiple intranasal (i.n.) challenges, after sensitisation in adjuvant or in adjuvant-free conditions. Eosinophil numbers in the broncho-alveolar lavage and lung histopathology were assessed in each model. We found that Major Histocompatibility Complex Class II (MHCII) deficiency and lack of conventional CD4+ T cells had the most profound effect, essentially ablating airway eosinophilia and goblet cell hyperplasia in all models. In contrast, Thymic stromal lymphopoietin receptor (TSLPR) deficiency greatly reduced eosinophilia but had a variable effect on goblet cells. CD1d deficiency and lack of Natural Killer T (NKT) cells moderately impaired inflammation in OVA models but not HDM, whereas sex affected the response to HDM but not OVA. Lastly, defective Toll-like receptor (TLR)4 expression had only a relatively modest overall impact on inflammation.

Conclusion

All the models studied were comparably dependent on adaptive CD4+ T cell responses and TSLP. In contrast, sex, NKT cells and TLR4 appeared to play subtler and more variable roles that were dependent on the type of allergen and mode of immunization and challenge. These results are consistent with clinical data suggesting a key role of CD4+ T cells and TSLP in patients with allergic asthma.

Electronic supplementary material

The online version of this article (10.1186/s12865-019-0295-y) contains supplementary material, which is available to authorized users.

Temporal variability in the allergenicity of airborne Alternaria spores

The concentration of fungal spores in the air is traditionally considered as a proxy of allergen exposure. However, in vitro experiments have shown that the allergenicity of Alternaria spores varies depending on ecophysiological and developmental factors. Despite the potential clinical significance of these findings, it has never been verified in outdoor environments. This study, therefore, aims to investigate variability in the amount of the major allergen (Alt a 1) released from Alternaria spores in outdoor air. During the 3-year monitoring study (2014-2016), the median seasonal allergenicity of Alternaria spores exceeded 8.6 × 10-3 pg Alt a 1/spore. The most allergenic spores were collected during the driest and the most polluted season (with respect to seasonal concentrations of ozone, sulphur dioxide, and particulate matter). Within the season, daily spore allergenicity ranged from 2.4 to 34.7 × 10-3 pg Alt a 1/spore (5th-95th percentile). No repeatable effects of weather and pollution on short-term variations in Alternaria spore allergenicity were found. However, during the episodes when high-potency spores were recorded, the air masses arrived from eastern directions. Contrary, the spores with the lowest allergenicity were related to western winds. This suggests that factors such as source area (habitat types) and species diversity could be responsible for the varying exposure to Alternaria allergens. Our findings show that high and low-potency spores are recorded in the air; therefore, the airborne concentrations of fungal spores alone may not be sufficient to provide allergy sufferers and healthcare professionals with information about allergen exposure.

Double-blind, randomized, placebo-controlled trial of allergen-specific immunotherapy with the major allergen Alt a 1

BACKGROUND

There have been few studies conducted on the efficacy and safety of specific immunotherapy with allergen extracts of fungi compared with other allergen extracts, and there are no data on the major allergen Alt a 1 of the fungus Alternaria alternata.

OBJECTIVES

We sought to evaluate the efficacy and safety of subcutaneous immunotherapy with 2 different doses of Alt a 1 in patients with rhinoconjunctivitis caused by sensitization to A alternata.

METHOD

We performed a multicenter, randomized, double-blind, placebo-controlled trial with Alt a 1 administered subcutaneously in patients with allergic rhinoconjunctivitis with or without controlled asthma aged 12 to 65 years. Three groups were included: the placebo group and active groups receiving 0.2 or 0.37 μg of Alt a 1 per dose. The main end point was the combined symptom and medication score. Secondary end points were cutaneous reactivity and serum IgE and IgG₄ levels to Alt a 1. Recorded adverse reactions were graded according to World Allergy Organization criteria.

RESULTS

There were significant reductions in the combined symptom and medication score for the 0.37-μg dose of Alt a 1 compared with placebo at 12 months of treatment. Reduced cutaneous reactivity and IgE levels, together with increased IgG₄ levels, were demonstrated for the 2 active groups versus the placebo group. A similar safety profile was found for both active groups compared with the placebo group. No serious adverse drug reactions were reported.

CONCLUSION

Immunotherapy with Alt a 1 was efficacious and safe, reducing the symptoms and medication consumption associated with rhinoconjunctivitis after only 1 year of treatment. The clinical benefits were associated with reduced skin reactivity and specific IgE levels and increased IgG₄ levels.

Establishment and characterization of a multi-purpose large animal exposure chamber for investigating health effects

Air pollution poses a significant threat to the environment and human health. Most in vivo health studies conducted regarding air pollutants, including particulate matter (PM) and gas phase pollutants, have been either through traditional medical intranasal treatment or using a tiny chamber, which limit animal activities. In this study, we designed and tested a large, whole-body, multiple animal exposure chamber with uniform dispersion and exposure stability for animal studies. The chamber simultaneously controls particle size distribution and PM mass concentration. Two different methods were used to generate aerosol suspension through either soluble material (Alternaria extract), liquid particle suspension (nanosilica solution), or dry powder (silica powder). We demonstrate that the chamber system provides well controlled and characterized whole animal exposures, where dosage is by inhalation of particulate matter.

Mold burden in house dust and its relationship with asthma control

OBJECTIVE

Some evidences indicate that exposure to molds or their products can be relevant for the loss of asthma control. Thus, we measured the mold burden present inside houses of subjects with asthma, and evaluated its relationship with asthma control.

METHODS

Markers of asthma control in adult patients residing in Mexico City were evaluated through questionnaires and spirometry. Dust was collected from the patients' houses and its fungal content was determined by mold specific quantitative PCR (MSQPCR) for 36 fungal species.

RESULTS

Forty-two patients with asthma (12 males, 30 females) with a mean age of 45 years (18-76 years) were included in the study. The level of asthma control measured through the Asthma Control Test ranged from 9 to 25 (mean 20.9). The FEV₁/FVC ratio fluctuated from 38 to 106 %predicted (mean, 87.4 %predicted). Associations between mold burden and asthma control differed between males and females. Thus, concentrations of some molds, particularly Aspergillus fumigatus, Aureobasidium pullulans, Stachybotrys chartarum, Alternaria alternata, Cladosporium cladosporioides 2, Cladosporium herbarum, and Epicoccum nigrum, were negatively associated with parameters of asthma control in male subjects, but not in female patients.

CONCLUSION

Our results showed that potential indoor exposure to some molds is associated with less asthma control in male subjects.

Alternaria-induced barrier dysfunction of nasal epithelial cells: role of serine protease and reactive oxygen species

BACKGROUND

Upper airway barrier dysfunction has been associated with chronic rhinosinusitis and allergic rhinitis. Alternaria is commonly found in nasal secretion and plays a role in the pathogenesis of airway diseases. The aim of this study was to investigate the effects of Alternaria on the junctional complex of nasal epithelial cells.

METHODS

Air-liquid interface nasal epithelial cultures from the inferior turbinate of septal surgery patients were stimulated with Alternaria alternate. Production of intracellular reactive oxygen species (ROS) and transepithelial resistance (TER) was measured. The expression of tight junction (TJ) and adherens junction (AJ) molecules was determined using real-time reverse transcriptase-polymerase chain reaction, Western blot analysis, and confocal microscopy. Protease activity in Alternaria was determined using protease inhibitors and heat inactivation.

RESULTS

Alternaria enhanced the production of ROS and reduced the TER. Alternaria decreased the messenger RNA and protein expression of TJs (zonula occludens-1, occludin, and claudin-1), but did not influence the AJ molecule. When Alternaria was pretreated with serine protease inhibitor and heat inactivation, ROS, TER, and TJ molecule expression returned to their nonstimulated levels.

CONCLUSION

Serine protease in Alternaria altered nasal epithelial barrier function. Intracellular ROS induced by Alternaria may influence the barrier function of nasal epithelial cells and enhance the inflammatory process of nasal mucosa.

Protease-activated receptor-2 signaling through β-arrestin-2 mediates Alternaria alkaline serine protease-induced airway inflammation

Alternaria alternata is a fungal allergen associated with severe asthma and asthma exacerbations. Similarly to other asthma-associated allergens, Alternaria secretes a serine-like trypsin protease(s) that is thought to act through the G protein-coupled receptor protease-activated receptor-2 (PAR2) to induce asthma symptoms. However, specific mechanisms underlying Alternaria-induced PAR2 activation and signaling remain ill-defined. We sought to determine whether Alternaria-induced PAR2 signaling contributed to asthma symptoms via a PAR2/β-arrestin signaling axis, identify the protease activity responsible for PAR2 signaling, and determine whether protease activity was sufficient for Alternaria-induced asthma symptoms in animal models. We initially used in vitro models to demonstrate Alternaria-induced PAR2/β-arrestin-2 signaling. Alternaria filtrates were then used to sensitize and challenge wild-type, PAR2-/- and β-arrestin-2-/- mice in vivo. Intranasal administration of Alternaria filtrate resulted in a protease-dependent increase of airway inflammation and mucin production in wild-type but not PAR2-/- or β-arrestin-2-/- mice. Protease was isolated from Alternaria preparations, and select in vitro and in vivo experiments were repeated to evaluate sufficiency of the isolated Alternaria protease to induce asthma phenotype. Administration of a single isolated serine protease from Alternaria, Alternaria alkaline serine protease (AASP), was sufficient to fully activate PAR2 signaling and induce β-arrestin-2-/--dependent eosinophil and lymphocyte recruitment in vivo. In conclusion, Alternaria filtrates induce airway inflammation and mucus hyperplasia largely via AASP using the PAR2/β-arrestin signaling axis. Thus, β-arrestin-biased PAR2 antagonists represent novel therapeutic targets for treating aeroallergen-induced asthma.

Alternaria alternata challenge at the nasal mucosa results in eosinophilic inflammation and increased susceptibility to influenza virus infection

BACKGROUND

Eosinophils in the nasal mucosa are an elemental feature of allergic rhinitis.

OBJECTIVE

Our objective was to explore eosinophilic inflammation and its impact on respiratory virus infection at the nasal mucosa.

METHODS

Inflammation in the nasal mucosae of mice was evaluated in response to repetitive stimulation with strict intranasal volumes of a filtrate of Alternaria alternata. Mice were then challenged with influenza virus.

RESULTS

Repetitive stimulation with A. alternata resulted in eosinophil recruitment to the nasal passages in association with elevated levels of IL-5, IL-13 and eotaxin-1; eosinophil recruitment was diminished in eotaxin-1-/- mice, and abolished in Rag1-/- mice. A. alternata also resulted in elevated levels of nasal wash IgA in both wild-type and eosinophil-deficient ∆dblGATA mice. Interestingly, A. alternata-treated mice responded to an influenza virus infection with profound weight loss and mortality compared to mice that received diluent alone (0% vs 100% survival, ***P < .001); the lethal response was blunted when A. alternata was heat-inactivated. Minimal differences in virus titre were detected, and eosinophils present in the nasal passages at the time of virus inoculation provided no protection against the lethal sequelae. Interestingly, nasal wash fluids from mice treated with A. alternata included more neutrophils and higher levels of pro-inflammatory mediators in response to virus challenge, among these, IL-6, a biomarker for disease severity in human influenza.

CONCLUSIONS AND CLINICAL RELEVANCE

Repetitive administration of A. alternata resulted in inflammation of the nasal mucosae and unanticipated morbidity and mortality in response to subsequent challenge with influenza virus. Interestingly, and in contrast to findings in the lower airways, eosinophils recruited to the nasal passages provided no protection against lethal infection. As increased susceptibility to influenza virus among individuals with rhinitis has been the subject of several clinical reports, this model may be used for further exploration of these observations.

Secreted protein extract analyses present the plant pathogen Alternaria alternata as a suitable industrial enzyme toolbox

Lignocellulosic plant biomass is the most abundant carbon source in the planet, which makes it a potential substrate for biorefinery. It consists of polysaccharides and other molecules with applications in pharmaceutical, food and feed, cosmetics, paper and textile industries. The exploitation of these resources requires the hydrolysis of the plant cell wall, which is a complex process. Aiming to discover novel fungal natural isolates with lignocellulolytic capacities, a screening for feruloyl esterase activity was performed in samples taken from different metal surfaces. An extracellular enzyme extract from the most promising candidate, the natural isolate Alternaria alternata PDA1, was analyzed. The feruloyl esterase activity of the enzyme extract was characterized, determining the pH and temperature optima (pH 5.0 and 55-60 °C, respectively), thermal stability and kinetic parameters, among others. Proteomic analyses derived from two-dimensional gels allowed the identification and classification of 97 protein spots from the extracellular proteome. Most of the identified proteins belonged to the carbohydrates metabolism group, particularly plant cell wall degradation. Enzymatic activities of the identified proteins (β-glucosidase, cellobiohydrolase, endoglucanase, β-xylosidase and xylanase) of the extract were also measured. These findings confirm A. alternata PDA1 as a promising lignocellulolytic enzyme producer.

SIGNIFICANCE

Although plant biomass is an abundant material that can be potentially utilized by several industries, the effective hydrolysis of the recalcitrant plant cell wall is not a straightforward process. As this hydrolysis occurs in nature relying almost solely on microbial enzymatic systems, it is reasonable to infer that further studies on lignocellulolytic enzymes will discover new sustainable industrial solutions. The results included in this paper provide a promising fungal candidate for biotechnological processes to obtain added value from plant byproducts and analogous substrates. Moreover, the proteomic analysis of the secretome of a natural isolate of Alternaria sp. grown in the presence of one of the most used vegetal substrates on the biofuels industry (sugar beet pulp) sheds light on the extracellular enzymatic machinery of this fungal plant pathogen, and can be potentially applied to developing new industrial enzymatic tools. This work is, to our knowledge, the first to analyze in depth the secreted enzyme extract of the plant pathogen Alternaria when grown on a lignocellulosic substrate, identifying its proteins by means of MALDI-TOF/TOF mass spectrometry and characterizing its feruloyl esterase, cellulase and xylanolytic activities.

Eosinophil persistence in vivo and sustained viability ex vivo in response to respiratory challenge with fungal allergens

BACKGROUND

Eosinophils are immunomodulatory leucocytes that contribute to the pathogenesis of Th2-driven asthma and allergic lung diseases.

OBJECTIVE

Our goal was to identify unique properties of eosinophils recruited to the lungs and airways of mice in response to challenge with asthma-associated fungal allergens.

METHODS

Mice were challenged intranasally on days 0, 3 and 6 with a filtrate of Alternaria alternata. Recruited eosinophils were enumerated in bronchoalveolar lavage fluid. Eosinophils were also isolated from lungs of mice sensitized and challenged with Aspergillus fumigatus and evaluated ex vivo in tissue culture.

RESULTS

Eosinophils persist in the airways for several weeks in response to brief provocation with A. alternata in wild-type, Gm-csf- and eotaxin-1-gene-deleted mice, while eosinophils are recruited but do not persist in the absence of IL-13. Eosinophils isolated from the lungs A. alternata-challenged mice are cytokine-enriched compared to those from IL5tg mice, including 800-fold higher levels of eotaxin-1. Furthermore, eosinophils from the lungs and spleen of fungal allergen-challenged wild-type mice are capable of prolonged survival ex vivo, in contrast to eosinophils from both untreated and fungal allergen-challenged IL5tg mice, which undergo rapid demise in the absence of exogenous cytokine support. TNF-α (but not IL5, IL-3, eotaxin-1 or GM-CSF) was detected in supernatants of ex vivo eosinophil cultures from the lungs of fungal allergen-challenged wild-type mice. However, neither TNF-α gene deletion nor anti-TNF-α neutralizing antibodies had any impact sustained eosinophil survival ex vivo.

CONCLUSION AND CLINICAL RELEVANCE

Eosinophils are phenotypically and functionally heterogeneous. As shown here, eosinophils from fungal allergen-challenged wild-type mice maintain a distinct cytokine profile, and, unlike eosinophils isolated from IL5tg mice, they survive ex vivo in the absence of exogenous pro-survival cytokine support. As treatments for asthma currently in development focus on limiting eosinophil viability via strategic cytokine blockade, the molecular mechanisms underlying differential survival merit further investigation.

Alternaria alternata (Fr.) Keissl with mutation G143A in the Cyt b gene is the source of a difficult-to-control allergen

The saprotrophic fungus Alternaria alternata is widespread in the agro-environment and produces more than ten allergenic proteins, mostly protein Alt a 1. The frequency of the Alt a 1 gene was analyzed in a group of A. alternata isolates from winter wheat kernels obtained in Poland, and the effectiveness of various fungicides targeting the pathogen was evaluated. The Alt a 1 gene was identified in four of the seven tested isolates. A. alternata colonized 35.67% kernels on average, but its frequency increased in stored grain where the presence of epiphytes was noted on 23.09 to 51.38% kernels, and endophytes-in 26.21 to 42.01% of kernels. The efficacy of field-applied fungicides did not exceed 50%, despite the fact that A. alternata is highly sensitive to propiconazole, fenpropimorph, and tebuconazole under in vitro conditions. The analyzed isolates were characterized by limited sensitivity to azoxystrobin (EC₅₀ ranged from 0.505 to 1.350 μg cm^-3) due to a mutation at codon 143 of the CYT b gene, responsible for resistance to quinone outside inhibitor fungicides, which was noted in all isolates. The spread of A. alternata can be effectively controlled with suitable fungicides and by monitoring the prevalence of pathogenic isolates in the environment.

Continuous Inhalation Exposure to Fungal Allergen Particulates Induces Lung Inflammation While Reducing Innate Immune Molecule Expression in the Brainstem

Continuous exposure to aerosolized fine (particle size ≤2.5 µm) and ultrafine (particle size ≤0.1 µm) particulates can trigger innate inflammatory responses in the lung and brain depending on particle composition. Most studies of manmade toxicants use inhalation exposure routes, whereas most studies of allergens use soluble solutions administered via intranasal or injection routes. Here, we tested whether continuous inhalation exposure to aerosolized Alternaria alternata particulates (a common fungal allergen associated with asthma) would induce innate inflammatory responses in the lung and brain. By designing a new environmental chamber able to control particle size distribution and mass concentration, we continuously exposed adult mice to aerosolized ultrafine Alternaria particulates for 96 hr. Despite induction of innate immune responses in the lung, induction of innate immune responses in whole brain samples was not detected by quantitative polymerase chain reaction or flow cytometry. However, exposure did trigger decreases in Arginase 1, inducible nitric oxide synthase, and tumor necrosis factor alpha mRNA in the brainstem samples containing the central nervous system respiratory circuit (the dorsal respiratory group, ventral respiratory group, and the pre-Bötzinger and Bötzinger complexes). In addition, a significant decrease in the percentage of Toll-like receptor 2-expressing brainstem microglia was detected by flow cytometry. Histologic analysis revealed a significant decrease in Iba1 but not glial fibrillary acidic protein immunoreactivity in both the brainstem and the hippocampus. Together these data indicate that inhalation exposure to a natural fungal allergen under conditions sufficient to induce lung inflammation surprisingly causes reductions in baseline expression of select innate immune molecules (similar to that observed during endotoxin tolerance) in the region of the central nervous system controlling respiration.

Preclinical safety and immunological efficacy of Alternaria alternata polymerized extracts

Introduction

Alternaria alternata is a widespread fungi whose allergy is a risk factor for asthma development. The use of a polymerized allergen extract (allergoid) may be safer than native extract based treatments while maintaining efficacy. The objective of this study was to characterize biochemically and immunochemically a new Alternaria alternata allergoid.

Methods

Characterization of native and allergoid extracts was performed by determination of protein content, protein and allergenic profile, biological potency, identification of Alternaria allergens, and Alt a 1 quantification. Safety was evaluated in toxicological assays (Ames test, limit test, and fish embryo acute toxicity test in zebrafish, and maximum tolerated dose and Dose‐range finding study in rats). Efficacy was evaluated as the capacity to induce IgG antibodies that block IgE‐binding to the allergen and cytokine induction (IFN‐γ, IL‐4, IL‐6, IL‐10, and TNF‐α) in PBMC from atopic donors.

Results

Protein and antigenic profiles showed significant modification of the depigmented allergoid with respect to the native extract, inducing a lower IgE binding capacity. Alt a 1, Alt a 3, Alt a 6, and Alt a 8 allergen sequences were identified in the polymer. No toxicological nor genotoxicity effects were observed. The polymer induced IgG antibodies that blocked human IgE binding epitopes, and it induced higher IL‐10 levels and similar levels of the other cytokines than native extract in PBMC.

Conclusions

This new A. alternata allergoid could be an effective immunotherapy treatment leading to cytokine stimulation and inducing synthesis of IgG antibodies able to block IgE binding to the allergen. In addition, no toxicological effect was observed, and it may be safer than native extract due to its lower IgE binding capacity and cytokine induction that suggest tolerance induction via T cell shift to Treg (IL‐10).

Granulometry, microbial composition and biological activity of dusts collected in French dairy farms

BACKGROUND

Dairy working increases the prevalence of lower airway respiratory diseases, especially COPD and asthma. Epidemiological studies have reported that chronic inhalation of organic dusts released during specific daily tasks could represent a major risk factor for development of these pathologies in dairy workers. Knowledge on size, nature and biological activity of such organic dusts remain however limited.

OBJECTIVE

To compare size distribution, microbial composition and cellular effects of dusts liberated by the spreading of straw bedding in five French dairy farms located in Brittany.

RESULTS

Mechanized distribution of straw bedding generated a cloud of inhalable dusts in the five dairy farms' barns. Thoracic particles having a 3-7.5µm size constituted 58.9-68.3% of these dusts. Analyses of thoracic dusts by next generation sequencing showed that the microbial dust composition differed between the five French farms, although Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria represent more than 97.5% of the bacterial phyla detected in each sample. Several bacteria genera comprising of human pathogenic species, such as Pseudomonas, Staphylococcus, Thermoactinomyces or Saccharopolyspora were identified. Cladosporium and Alternaria fungal genera, which are potent environmental determinants of respiratory symptoms, were detected in dusts collected in the five farms and their levels reached 15.5-51.1% and 9-24.7% of assignable fungal sequences in each sample, respectively. Finally, all dust samples significantly and strongly increased the expression of the pro-inflammatory TNF-α, IL-1β, IL-6 and IL-8 cytokines at both mRNA and protein levels in human monocyte-derived macrophages. Their effects were dose-dependent and detectable from 1µg/ml. The intensity of the macrophage responses however differed according to the samples.

CONCLUSIONS

Our results strengthen the hypothesis that organic dusts released during the distribution of straw bedding are mainly constituted of thoracic particles which are small enough to deposit on lower bronchial epithelium of dairy farmers and induce inflammation.

The major Alternaria alternata allergen, Alt a 1: A reliable and specific marker of fungal contamination in citrus fruits

The ubiquitously present spores of Alternaria alternata can spoil a wide variety of foodstuffs, including a variety of fruits belonging to the Citrus genus. The major allergenic protein of A. alternata, Alt a 1, is a species-specific molecular marker that has been strongly associated with allergenicity and phytopathogenicity of this fungal species. This study aimed to evaluate the potential of the detection of Alt a 1 as a reliable indicator of A. alternata contamination in citrus fruits. To accomplish this aim, sixty oranges were artificially infected with a spore suspension of A. alternata. Internal fruit material was collected at different incubation times (one, two and three weeks after the fungal inoculation) and used for both total RNA extraction and protein extraction. Alt a 1 detection was then performed by polymerase chain reaction (PCR) amplification using Alt a 1 specific primers and by enzyme-linked immunosorbent assay (ELISA). The experimental model presented in this work was effective to simulate the typical Alternaria black rot phenotype and its progression. Although both PCR and ELISA techniques have been successfully carried out for detecting Alt a 1 allergen in A. alternata infected oranges, the PCR method was found to be more sensitive than ELISA. Nevertheless, ELISA results were highly valuable to demonstrate that considerable amounts of Alt a 1 are produced during A. alternata fruit infection process, corroborating the recently proposed hypothesis that this protein plays a role in the pathogenicity and virulence of Alternaria species. Such evidence suggests that the detection of Alt a 1 by PCR-based assay may be used as a specific indicator of the presence of pathogenic and allergenic fungal species, A. alternata, in fruits. This knowledge can be employed to control the fungal infection and mitigate agricultural losses as well as human exposure to A. alternata allergens and toxins.

Airway epithelial anion secretion and barrier function following exposure to fungal aeroallergens: role of oxidative stress

Aeroallergens produced by Alternaria alternata can elicit life-threatening exacerbations of asthma in patients sensitized to this fungus. In this study, the effect of Alternaria on ion transport mechanisms underlying mucociliary clearance and airway epithelial barrier function was investigated in human airway epithelial cells. Apical exposure to Alternaria induced an increase in anion secretion that was inhibited by blockers of CFTR and Ca²⁺-activated Cl^- channels. Stimulation of anion secretion was dependent on Ca²⁺ uptake from the apical solution. Alternaria exposure also produced an increase in reactive oxygen species (ROS) that was blocked by pretreatment with the oxidant scavenger glutathione (GSH). GSH and the NADPH oxidase inhibitor/complex 1 electron transport inhibitor diphenylene iodonium chloride (DPI) blocked ATP release and the increase in intracellular [Ca²⁺] evoked by AlternariaAlternaria also decreased transepithelial resistance, and a portion of this effect was dependent on the increase in ROS. However, the Alternaria-induced increase in unidirectional dextran (molecular mass = 4,000 Da) flux across the epithelium could not be accounted for by increased oxidative stress. These results support the conclusion that oxidative stress induced by Alternaria was responsible for regulating Ca²⁺-dependent anion secretion and tight junction electrical resistance that would be expected to affect mucociliary clearance.

Desensitization of idiopathic pulmonary fibrosis fibroblasts to Alternaria alternata extract-mediated necrotic cell death

Alternaria alternata is an allergenic fungus and known to cause an upper respiratory tract infection and asthma in humans with compromised immunity. Although A. alternata's effect on airway epithelial cells has previously been examined, the potential role of A. alternata on lung fibroblast viability is not understood. Since lung fibroblasts derived from patients with idiopathic pulmonary fibrosis (IPF) display a distinct phenotype that is resistant to stress and cell death inducing conditions, the investigation of the role of Alternaria on pathological IPF fibroblasts provides a better understanding of the fibrotic process induced by an allergenic fungus. Therefore, we examined cell viability of control and IPF fibroblasts (n = 8 each) in response to A. alternata extract. Control fibroblast cell death was increased while IPF fibroblasts were resistant when exposed to 50-100 μg/mL of A. alternata extract. However, there was no significant difference in kinetics or magnitude of Ca²⁺ responses from control lung and IPF fibroblasts. In contrast, unlike control fibroblasts, intracellular reactive oxygen species (ROS) levels remained low when IPF cells were treated with A. alternata extracts as a function of time. Caspase 3/7 and TUNEL assay revealed that enhanced cell death caused by A. alternata extract was likely due to necrosis, and 7-AAD assay and the use of sodium pyruvate for ATP generation further supported our findings that IPF fibroblasts become resistant to A. alternata extract-induced necrotic cell death. Our results suggest that exposure to A. alternata potentially worsens the fibrotic process by promoting normal lung fibroblast cell death in patients with IPF.

Transcriptome Analysis Reveals the Genetic Basis of the Resveratrol Biosynthesis Pathway in an Endophytic Fungus (Alternaria sp. MG1) Isolated from Vitis vinifera

Alternaria sp. MG1, an endophytic fungus previously isolated from Merlot grape, produces resveratrol from glucose, showing similar metabolic flux to the phenylpropanoid biosynthesis pathway, currently found solely in plants. In order to identify the resveratrol biosynthesis pathway in this strain at the gene level, de novo transcriptome sequencing was conducted using Illumina paired-end sequencing. A total of 22,954,434 high-quality reads were assembled into contigs and 18,570 unigenes were identified. Among these unigenes, 14,153 were annotated in the NCBI non-redundant protein database and 5341 were annotated in the Swiss-Prot database. After KEGG mapping, 2701 unigenes were mapped onto 115 pathways. Eighty-four unigenes were annotated in major pathways from glucose to resveratrol, coding 20 enzymes for glycolysis, 10 for phenylalanine biosynthesis, 4 for phenylpropanoid biosynthesis, and 4 for stilbenoid biosynthesis. Chalcone synthase was identified for resveratrol biosynthesis in this strain, due to the absence of stilbene synthase. All the identified enzymes indicated a reasonable biosynthesis pathway from glucose to resveratrol via glycolysis, phenylalanine biosynthesis, phenylpropanoid biosynthesis, and stilbenoid pathways. These results provide essential evidence for the occurrence of resveratrol biosynthesis in Alternaria sp. MG1 at the gene level, facilitating further elucidation of the molecular mechanisms involved in this strain's secondary metabolism.