Exposure to fungi, particularly in water damaged indoor environments

March 1, 2008

published in 06

Allergy and Clinical Immunology Branch, Health Effects Laboratory

Division,

National Institute for Occupational Safety and Health, Centers for

Disease

Control and Prevention, town, West Virginia, USA.

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.

PMID: 17050446 [PubMed - in process]

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