New diagnostic for airborne allergens

A new technique that better identifies asthma and allergy triggers may soon provide some welcome relief to susceptible individuals.

At home and at work, people inhale airborne particles with each breath. The suspended particles and filaments -- most of uncertain origin and composition -- are a source of anonymous allergens that can provoke misery in hayfever and asthma sufferers -- but determining the identity of the particles that carry allergens has previously been impossible.

A stunning advance in personalised medicine, developed at the Woolcock Institute of Medical Research, located at the University of Sydney, could soon be providing answers.

The Woolcock Institute is a leader in research into respiratory disease and disorders. The Halogen immunoassay, developed by Dr Euan Tovey, head of the Woolcock's allergen research group, finally threatens to make obsolete one of the most archaic, hit-or-miss diagnostic tools in modern medicine -- the skin-prick test for allergy.

Tovey's PhD student Brett Green made the Editor's Choice of the US asthma research journal, Journal of Allergy and Clinical Immunology last month with his discovery that ordinary household air contains an unsuspected array of fungal fragments, consisting of spores and hyphal filaments. Both contain previously unrecognised allergens.

Green said the discovery challenges traditional thinking about airborne allergens -- not only are they more diverse than previously suspected, the small fragments are readily inhaled deep into the lungs, where they can trigger asthma attacks and hayfever.

He and his co-workers used the Halogen immunossay to monitor household air for 2.5 hours a day over a 21-day period.

The Halogen assay highlights different antigens in particles that have been captured from the air on a transparent adhesive sheet, then stains them with the help of antigen-specific immunoglobulin E (IgE) antibodies from the sera of allergy sufferers -- IgE antibodies mediate the immune response to environmental allergens.

The power of the Halogen immunoassay is that it permits real-time seasonal sampling of the spectrum of airborne allergens present in the home or office atmosphere -- including previously unrecognised allergens -- it also highlights the specific antigens to which the individual allergy sufferer is reacting, by creating a stained 'halo' around the antigen particle. Hence its name: 'Halogen' (halo-allergen) assay.

The skin-prick test, in contrast, exposes the patient to a battery of known allergens, which are applied to tiny scalpel nicks in the skin of the inner forearm.

Green said allergen sample kits produced overseas may be unrepresentative of the allergen spectrum in Australia -- or in a particular region of Australia. Moreover, the antigen preparations may have lost potency after years of use.

"The concordance between the skin-prick test and disease is very tenuous," he said.

Previously, only a handful of fungi were believed to contribute to the allergen load in household air. "What we found completely amazed us," he said.

"It wasn't just a handful, but a very large number of unidentified species and genera, expressing allergens.

"The airborne hyphae fragments also occur in higher numbers than any spore count for a single species, so they're obviously significant. They can go down to less than 3 microns in size, so they can get deep into the respiratory tract."

The Woolcock and the University spun out a company, Inhalix, to commercialise the Halogen assay several years ago, at the time of the biotech stockmarket collapse. It foundered, and the IP reverted to the University, which is now seeking an established company in the immunology field to partner its commercial development.

Tovey said they had also developed a device that was worn in the nostrils to directly sample the particulate content of the air a person is breathing at home or at work.