Detection of aerosolized Alternaria alternata conidia, hyphae, and fragments by using a novel double-immunostaining technique

Particle size distribution of the major Alternaria alternata allergen, Alt a 1, derived from airborne spores and subspore fragments

Fungal fragments are abundant immunoreactive bioaerosols that may outnumber the concentrations of intact spores in the air. To investigate the importance of Alternaria fragments as sources of allergens compared to Alternaria spores, we determined the levels of Alternaria spores and Alt a 1 (the major allergen in Alternaria alternata spores) collected on filters within three fractions of particulate matter (PM) of different aerodynamic diameter: (1) PM_>10, (diameter>10 μm); (2) PM_2.5-10 (2.5-10μm); (3) PM_2.5 (0.12-2.5 μm). The airborne particles were collected using a three stage high-volume ChemVol cascade impactor during the Alternaria sporulation season in Poznań, Poland (30 d between 6 July and 22 September 2016). The quantification of Alt a 1 was performed using the enzyme-linked immunosorbent assay. High concentrations of Alt a 1 were recorded during warm and dry d characterized by high sunshine duration, lack of clouds and high dew point values. Atmospheric concentrations of Alternaria spores correlated significantly (r = 0.930, p < 0.001) with Alt a 1 levels. The highest Alt a 1 was recorded in PM_2.5-10 (66.8 % of total Alt a 1), while the lowest in PM_2.5 (<1.0 %). Significantly more Alt a 1 per spore (>30 %) was observed in PM_2.5-10 than in PM_>10. This Alt a 1 excess may be derived from sources other than spores, e.g. hyphal fragments. Overall, in outdoor air the major source of Alt a 1 are intact Alternaria spores, but the impact of other fungal fragments (hyphal parts, broken spores, conidiophores) cannot be neglected, as they may increase the total atmospheric Alt a 1 concentration.

Environmental Mapping of Paracoccidioides spp. in Brazil Reveals New Clues into Genetic Diversity, Biogeography and Wild Host Association

Background

Paracoccidioides brasiliensis and Paracoccidioides lutzii are the etiological agents of Paracoccidioidomycosis (PCM), and are easily isolated from human patients. However, due to human migration and a long latency period, clinical isolates do not reflect the spatial distribution of these pathogens. Molecular detection of P. brasiliensis and P. lutzii from soil, as well as their isolation from wild animals such as armadillos, are important for monitoring their environmental and geographical distribution. This study aimed to detect and, for the first time, evaluate the genetic diversity of P. brasiliensis and P. lutzii for Paracoccidioidomycosis in endemic and non-endemic areas of the environment, by using Nested PCR and in situ hybridization techniques.

Methods/Principal Findings

Aerosol (n = 16) and soil (n = 34) samples from armadillo burrows, as well as armadillos (n = 7) were collected in endemic and non-endemic areas of PCM in the Southeastern, Midwestern and Northern regions of Brazil. Both P. brasiliensis and P. lutzii were detected in soil (67.5%) and aerosols (81%) by PCR of Internal Transcribed Spacer (ITS) region (60%), and also by in situ hybridization (83%). Fungal isolation from armadillo tissues was not possible. Sequences from both species of P. brasiliensis and P. lutzii were detected in all regions. In addition, we identified genetic Paracoccidioides variants in soil and aerosol samples which have never been reported before in clinical or armadillo samples, suggesting greater genetic variability in the environment than in vertebrate hosts.

Conclusions/Significance

Data may reflect the actual occurrence of Paracoccidioides species in their saprobic habitat, despite their absence/non-detection in seven armadillos evaluated in regions with high prevalence of PCM infection by P. lutzii. These results may indicate a possible ecological difference between P. brasiliensis and P. lutzii concerning their wild hosts.

Paracoccidioides brasiliensis and Paracoccidioides lutzii are the fungal species responsible for one of the most important mycoses of Latin America, Paracoccidioidomycosis (PCM). These fungi can grow in soil from forests, deforested areas, sugarcane, coffee, and rice plantations, as well as pasturelands, and they are strongly associated to armadillo burrows, which can explain their frequent isolation from this mammal’s tissues. The environmental detection of these pathogens in endemic and non-endemic areas of PCM is important for mapping risk areas, as well as for understanding the infection ability and clinical manifestations of these fungi. These pieces of information are not provided by isolates obtained from human patients, because these fungi have a long latency period and the human host can migrate, leading to a misinterpretation of the actual geographic distribution of these pathogens. By using two different molecular methodologies (Nested PCR and in situ fluorescence), we detected both species of P. brasiliensis and P. lutzii in soil and in aerosol samples, even in areas where PCM is only associated to one of these two species. These data might indicate different habitat maintenance strategies between the species, which means that the infection ability may change according to the climatic and soil conditions. Despite contributing new information about the ecology of these important fungal pathogens, our molecular approach for the environmental detection of Paracoccidioides species may also be applied for their detection and differentiation in clinical samples, improving the diagnosis of this important systemic mycosis.

Impaired induction of allergic lung inflammation by Alternaria alternata mutant MAPK homologue Fus3

The fungal allergen Alternaria alternata is associated with development of asthma, though the mechanisms underlying the allergenicity of Alternaria are largely unknown. The aim of this study was to identify whether the MAP kinase homologue Fus3 of Alternaria contributed to allergic airway responses. Wild-type (WT) and Fus3 deficient Alternaria extracts were given intranasal to mice. Extracts from Fus3 deficient Alternaria that had a functional copy of Fus3 introduced were also administered (CpFus3). Mice were challenged once and levels of BAL eosinophils and innate cytokines IL-33, thymic stromal lymphopoeitin (TSLP), and IL-25 (IL-17E) were assessed. Alternaria extracts or protease-inhibited extract were administered with (OVA) during sensitization prior to ovalbumin only challenges to determine extract adjuvant activity. Levels of BAL inflammatory cells, Th2 cytokines, and OX40-expressing Th2 cells as well as airway infiltration and mucus production were measured. WT Alternaria induced innate airway eosinophilia within 3 days. Mice given Fus3 deficient Alternaria were significantly impaired in developing airway eosinophilia that was largely restored by CpFus3. Further, BAL IL-33, TSLP, and Eotaxin-1 levels were reduced after challenge with Fus3 mutant extract compared with WT and CpFus3 extracts. WT and CpFus3 extracts demonstrated strong adjuvant activity in vivo as levels of BAL eosinophils, Th2 cytokines, and OX40-expressing Th2 cells as well as peribronchial inflammation and mucus production were induced. In contrast, the adjuvant activity of Fus3 extract or protease-inhibited WT extract was largely impaired. Finally, protease activity and Alt a1 levels were reduced in Fus3 mutant extract. Thus, Fus3 contributes to the Th2-sensitizing properties of Alternaria.

Detection of Paracoccidioides spp. in environmental aerosol samples

Taking into account that paracoccidioidomycosis infection occurs by inhalation of the asexual conidia produced by Paracoccidioides spp. in its saprobic phase, this work presents the collection of aerosol samples as an option for environmental detection of this pathogen, by positioning a cyclonic air sampler at the entrance of armadillo burrows. Methods included direct culture, extinction technique culture and Nested PCR of the rRNA coding sequence, comprising the ITS1-5.8S-ITS2 region. In addition, we evaluated one armadillo (Dasypus novemcinctus) as a positive control for the studied area. Although the pathogen could not be isolated by the culturing strategies, the aerosol sampling associated with molecular detection through Nested PCR proved the best method for discovering Paracoccidioides spp. in the environment. Most of the ITS sequences obtained in this investigation proved to be highly similar with the homologous sequences of Paracoccidioides lutzii from the GenBank database, suggesting that this Paracoccidioides species may not be exclusive to mid-western Brazil as proposed so far.

Sensitization to airborne ascospores, basidiospores, and fungal fragments in allergic rhinitis and asthmatic subjects in San Juan, Puerto Rico

BACKGROUND

Fungal spores are the predominant biological particulate in the atmosphere of Puerto Rico, yet their potential as allergens has not been studied in subjects with respiratory allergies. The purpose of this study was to determine the level of sensitization of subjects with respiratory allergies to these particles.

METHODS

Serum samples were drawn from 33 subjects with asthma, allergic rhinitis, or nonallergic rhinitis and 2 controls with different skin prick test reactivity. An MK-3 sampler was used to collect air samples and the reactivity of the sera to fungal particles was detected with a halogen immunoassay.

RESULTS

All subjects reacted to at least 1 fungal particle. Thirty-one subjects reacted to ascospores, 29 to basidiospores, 19 to hyphae/fungal fragments, and 12 to mitospores. The median percentage of haloes in allergic rhinitis subjects was 4.82% while asthma or nonallergic rhinitis subjects had values of 1.09 and 0.39%, respectively. Subjects with skin prick tests positive to 3, 2, 1, or no extract had 5.24, 1.09, 1.61, and, 0.57% of haloed particles, respectively. If skin prick tests were positive to basidiomycetes, pollen, animals, or deuteromycetes, the percentages of haloes were 4.72, 4.15, 3.63, and 3.31%, respectively. Of all haloed particles, 46% were unidentified, 25% ascospores, 20% basidiospores, 7% hyphae/fungal fragments, and 2% mitospores. IgE levels and the number of positive skin prick test extracts correlated with the percentage of haloes.

CONCLUSION

In tropical environments, sensitization to airborne basidiomycetes, ascomycetes, and fungal fragments seems to be more prevalent than sensitization to mitospores in subjects with active allergies, suggesting a possible role in exacerbations of respiratory allergies.

Surveillance of Fungal Allergic Sensitization Using the Fluorescent Halogen Immunoassay

OBJECTIVE: Conidia derived from a small number of common fungal genera are widely accepted as the etiological agents responsible for fungal allergic sensitization. The contribution of fungal conidia, spores, airborne hyphae, and subcellular fragments from other uncharacterized fungal genera remains unclear. In this proof-of-concept study, we examined the composition of mycoaerosols that atopic women were exposed and sensitized to in their own indoor environment using the fluorescent halogen immunoassay (fHIA). PATIENTS AND METHODS: Mycoaerosols were collected onto mixed cellulose ester protein binding membranes (PBMs) for 30 minutes with volumetric air sampling pumps. The PBMs were laminated with an adhesive cover slip and indirectly immunostained with individual patient serum IgE using the fHIA. Samples were examined using confocal laser scanning microscopy and immunostained particles were expressed as a percentage of total particles. RESULTS: All air samples contained a broad spectrum of fungal spores, conidia, hyphae, and other fungal particulates. Airborne concentrations varied between individual study participant environments. Positively immunostained conidia belonging to moniliaceous amerospores, Cladosporium, Alternaria, and many unknown species were observed in the majority of air samples. Other fungal genera including Bipolaris, Curvularia, Pithomyces, and Stachybotrys, in addition to, ascospore genera and dematiaceous hyphal fragments released detectable allergen. Twelve percent of all fHIA haloes quantified in the analysis were directed towards fungal particles. No immunostaining was detected to conidia belonging to Epicoccum, Fusarium, and Spegazzinia species. CONCLUSION: In addition to characterized fungal aeroallergens, we observed a wider composition of fungi that bound human IgE. Field surveillance studies that utilize immunodiagnostic techniques such as the fHIA will provide further insight into the diversity of fungi that function as aeroallergen sources in individual study participant environments.

The Halogen assay--a new technique for measuring airborne allergen

The Halogen assay is a new technique for measuring airborne allergen. The assay is unique in that it is capable of analyzing allergens and particles together, combining the advantages of morphological approaches and immunoassay. The Halogen assay allows direct observation of the particles that carry the allergen as well as being capable of identifying all the allergen sources an individual is exposed and sensitized to. The assay is sensitive because the extracted allergen is bound to the membrane at a high local concentration within the minute area around each particle and so is easily detected by immunostaining. It is therefore easy to detect few pollen grains. The Halogen method supersedes other methods commonly used to identify allergens as it is capable of identifying airborne particles that are allergen sources.

Allergen avoidance

The systematic avoidance of indoor allergens by modification of houses, furnishings, or hygiene practices has long been advocated to reduce both the incidence of allergic diseases in at-risk infants and exacerbations or symptoms in those previously sensitized with such a disease. However, such advocacy is now under challenge, due to both a lack of evidence of clinical efficacy of avoidance measures and rapidly changing models of disease causation and pathology. This article reviews the current dilemmas in understanding the complexity of allergen sources, disease risks, nature of bioaerosol exposure, and the inadequacies of many available methods.

Airborne fungal fragments and allergenicity

Exposure to fungi, particularly in water damaged indoor environments, has been thought to exacerbate a number of adverse health effects, ranging from subjective symptoms such as fatigue, cognitive difficulties or memory loss to more definable diseases such as allergy, asthma and hypersensitivity pneumonitis. Understanding the role of fungal exposure in these environments has been limited by methodological difficulties in enumerating and identifying various fungal components in environmental samples. Consequently, data on personal exposure and sensitization to fungal allergens are mainly based on the assessment of a few select and easily identifiable species. The contribution of other airborne spores, hyphae and fungal fragments to exposure and allergic sensitization are poorly characterized. There is increased interest in the role of aerosolized fungal fragments following reports that the combination of hyphal fragments and spore counts improved the association with asthma severity. These fragments are particles derived from any intracellular or extracellular fungal structure and are categorized as either submicron particles or larger fungal fragments. In vitro studies have shown that submicron particles of several fungal species are aerosolized in much higher concentrations (300-500 times) than spores, and that respiratory deposition models suggest that such fragments of Stachybotrys chartarum may be deposited in 230-250 fold higher numbers than spores. The practical implications of these models are yet to be clarified for human exposure assessments and clinical disease. We have developed innovative immunodetection techniques to determine the extent to which larger fungal fragments, including hyphae and fractured conidia, function as aeroallergen sources. These techniques were based on the Halogen Immunoassay (HIA), an immunostaining technique that detects antigens associated with individual airborne particles >1 microm, with human serum immunoglobulin E (IgE). Our studies demonstrated that the numbers of total airborne hyphae were often significantly higher in concentration than conidia of individual allergenic genera. Approximately 25% of all hyphal fragments expressed detectable allergen and the resultant localization of IgE immunostaining was heterogeneous among the hyphae. Furthermore, conidia of ten genera that were previously uncharacterized could be identified as sources of allergens. These findings highlight the contribution of larger fungal fragments as aeroallergen sources and present a new paradigm of fungal exposure. Direct evidence of the associations between fungal fragments and building-related disease is lacking and in order to gain a better understanding, it will be necessary to develop diagnostic reagents and detection methods, particularly for submicron particles. Assays using monoclonal antibodies enable the measurement of individual antigens but interpretation can be confounded by cross-reactivity between fungal species. The recent development of species-specific monoclonal antibodies, used in combination with a fluorescent-confocal HIA technique should, for the first time, enable the speciation of morphologically indiscernible fungal fragments. The application of this novel method will help to characterize the contribution of fungal fragments to adverse health effects due to fungi and provide patient-specific exposure and sensitization profiles.

Halogen immunoassay, a new method for the detection of sensitization to fungal allergens; comparisons with conventional techniques

BACKGROUND

Accurate diagnosis of allergy to specific fungal species is confounded by the variability in allergens occurring with different diagnostic systems. We compared the halogen immunoassay (HIA), which uses allergens expressed by freshly germinated spores that are bound to protein binding membranes (PBM), with the commercial Pharmacia UniCap assay (CAP) and with skin prick tests (SPT).

METHODS

Serum from 60 subjects was used; 30 were SPT positive and sensitized to at least one of Alternaria alternata or Aspergillus fumigatus and the other 30 were SPT negative to these fungi but known to be sensitized to non-fungal allergens. All sera were analyzed by CAP against A. alternata, A. fumigatus, Cladosporium herbarum and Epicoccum purpurascens. For HIA, spores from reference cultures belonging to these four species were germinated on PBM, laminated and then probed with each serum. Two independent observers using an ordinal ranking system quantified the intensity and occurrence of the resultant immunoglobulin E (IgE) immunostained haloes around spores and this was statistically compared with the results of the two conventional immunodiagnostic techniques.

RESULTS

Germinated conidia of each species expressed detectable allergen in the HIA. The agreement between the ordinal rank scores assigned by the pair of observers was very good (k >or= 0.8) and only differed for A. fumigatus (k = 0.66) . Between 3% and 7% of SPT negative sera was identified by HIA to have specific IgE towards A. fumigatus and A. alternata. For all four species tested there were strong correlations between HIA and CAP (P < 0.0001). However the correlation of both HIA and CAP to SPT was weaker for A. alternata (r(s) = 0.44, P < 0.0153) and absent for A. fumigatus.

CONCLUSIONS

Overall, the HIA is a new immunodiagnostic technique for the detection of sensitization to fungal allergens that correlates significantly with CAP and to a lesser extent with SPT. This may be due to extract variability and system differences. The significance of this derives from the unique ability of the HIA to measure IgE antibodies to the undegraded allergens that are actively secreted by germinating conidia and hyphae. These are the natural agents of exposure to fungi, and as such, are most likely to be relevant to clinical disease.

The development of species-specific immunodiagnostics for Stachybotrys chartarum: the role of cross-reactivity

Mold contamination and exposure to fungi in indoor environments has been associated with various adverse health effects but little is known about the significance of individual fungal species in the initiation or exacerbation of such effects. Using Stachybotrys chartarum as a model fungus we sought to demonstrate that monoclonal antibodies (mAbs) can provide species-specific diagnostic reagents and also be used to investigate immunological cross-reactivity patterns among fungi. Mice were immunized with S. chartarum spore walls and monoclonal antibodies were screened against 60 fungal species and 24 different isolates of S. chartarum using an indirect ELISA. One species-specific mAb (IgG(1)) reacted only with spore preparations but not mycelium of S. chartarum or propagules of any other fungus. Five cross-reactive mAbs (IgM) documented extensive cross-reactivity among nine related Stachybotrys species and several non-related genera including several species of Cladosporium, Memnoniella, Myrothecium and Trichoderma. We also found that the ELISA reactivity for cross-reactive antigens and different isolates of S. chartarum differed considerably for normalized total amounts of mycelial antigen. We demonstrate that mAbs and immunoassays have the potential to detect S. chartarum species-specifically. The observed reactivity patterns with cross-reactive mAbs suggest that several fungi may share common antigens and that the majority of antigens are expressed by spores and mycelia. The observed cross-reactivity patterns need to be considered for accurate interpretations of environmental and serological analyses.