Cat allergies may be tamed by adding an asthma therapy to allergy shots

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Adding lab-made antibodies to allergy shots may better groom the immune system against cat allergies than standard shots alone. The combination therapy also reduced allergy symptoms for a year after stopping treatment, a new study finds

Allergy shots, also called immunotherapy, have been used for more than a century to reduce the itchy, watery eyes, sneezing, runny nose, congestion and other symptoms of allergies. The shots contain tiny amounts of the things people are allergic to, called allergens. People get shots weekly to monthly for three to five years and gradually build up tolerance to the allergen.

Despite their long use, scientists don’t know exactly how allergy shots work, says Lisa Wheatley, an allergist at the National Institute of Allergy and Infectious Diseases. Some people are essentially cured of their allergies, while others may need shots indefinitely. “We knew that if you were on immunotherapy for cat [allergies] … you will be better after that year, but you will not retain that benefit.”

The study was done to see if researchers could improve allergy therapy by reducing the amount of time shots were needed while still giving patients long-lasting relief.  The team also hoped to better understand how immunotherapy works, she says.

When allergies strike, some immune cells produce alarm chemicals that trigger inflammation and other symptoms. “If we could dampen the signaling that says ‘danger,’ we could maybe improve immunotherapy,” Wheatley says.

She and colleagues used a monoclonal antibody called tezepelumab to block one of those alarm chemicals, known as thymic stromal lymphopoietin, or TSLP. The antibody has been used as an asthma treatment, so researchers already knew it is generally safe.

Researchers gave 121 cat allergy sufferers either standard allergy shots alone, tezepelumab alone, a combination of the two or a placebo. On its own, tezepelumab was no better than just a placebo, the researchers found.

After a year of treatment, people who got the combo had reduced allergy symptoms to cat dander squirted up their noses compared with people who got standard shots, researchers report October 9 in the Journal of Allergy and Clinical Immunology.

And levels of allergy-triggering antibodies called IgE fell and kept falling even a year after treatment stopped in people who got the combination. In people on standard shots, IgE levels started to claw their way back to baseline once treatment stopped, Wheatley says.

One reason the therapy may work is that it alters inflammation-triggering gene activity in some immune cells, the team found. Immune cells called mast cells made less tryptase — one of the major chemicals released in an allergic reaction — in people who got the combination therapy, an analysis of nasal swabs showed.

While the results are encouraging, it’s not clear that tezepelumab would work as well for other allergies, says Edward Zoratti, an allergist and immunologist at Henry Ford Hospital in Detroit who was not involved in the study. “Did they just get lucky and choose the right allergen?”

Cat allergies develop against a single sticky protein called Fel d1 that is in cats’ saliva and in flakes of dead skin cells, or dander (SN: 2/13/20). Cockroach allergies, in contrast, can be produced by a variety of proteins.

Another possible drawback is that monoclonal antibodies are expensive, Zoratti says.

Much more research is needed before this or any other therapy is added to allergy shots in a doctor’s office, he says, but the study is important for understanding how allergy therapies work. “It’s one step in a long chain that will probably lead us to a really useful therapy in the future.”

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