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Yale Researchers Link Anti-Parasite Substance to Asthma Responses

Posted on: Saturday, 12 June 2004, 06:00 CDT

WASHINGTON - Yale University researchers have discovered a surprising possible target for asthma therapy - a parasite-fighting molecule long thought to be an evolutionary leftover.

Blocking this substance, called chitinase, in mice bred to have asthma attacks cut the disease-causing lung inflammation, the researchers report in today's edition of the journal Science.

Then, examinations of 16 people's lung tissue showed asthmatics harbored high levels of chitinase while the healthy appeared to have none, Yale pulmonary specialist Jack Elias and colleagues report.

Chitinase breaks down a compound in the tough outer shells of certain insects and parasites, making it key to parasite protection for certain simple organisms. Scientists had long thought humans no longer had a need to produce the molecule - until they recently discovered some human chitinases and began struggling to discover what they do.

The asthma finding supports previous research showing "many similarities between parasite [immune] responses and asthma responses," Elias said. "It also suggests if you can control those responses, you will be able to control asthma."

Yale licensed patents to the discovery to MedImmune Inc., a biotechnology company, to try to develop a chitinase-blocking drug.

The researchers discovered the asthma link almost by accident. They had assumed that crystals in the lungs of asthma-prone mice were identical to crystals found in the sputum of human patients - but testing turned up chitinase instead.

The research may bolster the "hygiene hypothesis," which says one reason asthma is rising is that young children no longer come into contact with as many of the germs that arm a maturing immune system against certain allergic conditions.

"These exposures have changed with time," noted Dr. Gail Weinmann, an airway biologist at the National Institutes of Health, which, with the American Lung Association, funded Elias' research. The finding suggests "this protein that protects against those parasites also contributes to a shift in our immune development."

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