More Than One Way to Skin a Cat Allergy

John is a Science contributing correspondent.

By fusing a cat protein and human protein, researchers have successfully blocked cat allergies in laboratory mice. The new method could be applied to a host of allergens and may help people overcome their allergies in months rather than years.

Allergies are like false alarms in the immune system. Although a whiff of pollen poses no threat to health, it causes the immune systems of allergic people to kick into overdrive. The traditional treatment is to slowly introduce the foreign molecule in small doses, allowing the immune system to adapt and eventually recognize it. But this adaptation requires many years of injections and uncomfortable reactions. And the adaptation method is impossible for allergies in which even miniscule amounts of allergens can trigger deadly reactions.

To get around this problem, a team led by Andrew Saxon, an immunologist at the University of California, Los Angeles, hijacked one of the immune system's own molecules. The researchers took a portion of the human antibody protein IgG and fused it to the cat protein responsible for cat allergy. Normally, when the cat protein finds its way into the blood of an allergic person, antibodies called IgE grab it and bind to receptors on immune cells. That triggers the cells to pump out small molecules such as histamine that cause the inflammation, asthma, and other agonies of allergies. But when IgG binds to those cells, it blocks the alarm. Saxon hoped that cat-seeking IgE would bind to the hybrid protein and stick to the immune cells as usual. But because IgG comes along for the ride, it should prevent the allergic response.

So far, the hybrid protein seems to work like a charm. It produced no adverse reaction when injected into cat-allergic mice and protected them from an injected dose of pure cat protein, report the researchers online 27 March in Nature. Saxon says that because the hybrid molecule does not trigger allergies, it can be injected at much higher doses than traditional treatments, potentially curing allergies in months rather than years. And because other foreign molecules can be substituted for the cat protein, the method offers hope for people with currently untreatable allergies such as those to nuts and seafood.

"This is definitely promising," says Karl Skriner, an immunologist at the Charité University Hospital in Berlin, Germany, "but they still have to show that antibodies don't eventually build up against the hybrid molecule and make it ineffective," which has hampered similar attempts.

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Posted in Biology