ALLERGENICITY FROM AIRBORNE FUNGAL FRAGMENTS
By Various Authors
Exposure to fungi,
especially in water damaged indoor environments, has been thought to aggravate a number of adverse health effects ranging
from symptoms such as fatigue, cognitive difficulties or memory loss to ore definable diseases such as asthma, hyper-sensitivity
pneumonitis and allergy.
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 n 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>1µm, 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.
Woolcock Institute of Medical
Research, Sydney, NSW, Australia
Centers for Disease Control and Prevention, Morgantown, West Virginia, USA