Airborne fungal fragments and allergenicity

Abstract

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...

Primary biological aerosol particles in the atmosphere: a review

“…dead bacteria and fungi, tissue fragments such as cell walls or cytoplasmic material). Although not capable of directly infecting a host, non-viable PBAP classes are still extremely important because they can provoke deleterious health effects (Gorny et al, 2002;Green et al, 2006) and may still be relevant for cloud formation.…”

“…Although it is generally assumed that spores comprise the majority of airborne fungal material, this remains largely unsubstantiated and has important implications for interpretation of both, laboratory or field measurements. Hyphal fragments have been observed in ambient air in a number of studies (Gorny et al, 2002;Green et al, 2006). Sinha and Kramer (1971) suggested that airborne hyphae are most commonly unbranched conidiophores that can be 1Á100 mm in length but that are more commonly 5Á40 mm.…”

Fungal fragments in moldy houses: A field study in homes in New Orleans and Southern Ohio

“…Hyphal fragments have been shown to represent 6-56% of the total fungal particle counts in field samples based on microscopic sample analysis (Li and Kendrick, 1996;Foto et al, 2005;Green et al, 2005). This method is limited typically to particles >1 μm (Green et al, 2006). Recent laboratory-based studies (Górny et al, 2002 andCho et al, 2005) have reported that large quantities of submicrometer-sized fungal and actinomycete fragments (ranging from 30 nm to 1 μm) are released together with intact spores from contaminated surfaces.…”

Fungi in the respiratory tract of horses with recurrent airway obstruction

“…Interestingly, studies call attention to the fact that the inhaled hyphae fragments have a much greater allergen potential than airborne conidia, especially given their capacity to produce numerous diffusible allergens (Green et al, 2006). It should also be noted that these structures in humans remain only in the upper portions of the airways, found mostly in samples of nasal mucosa (Green et al, 2006). Here we studied samples from the tracheobronchial region, and one might speculate that the large airway diameter in horses may allow for the detection of hyphae fragments in the lower respiratory tract.…”