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Sunday, April 24, 2011

Cat allergy vaccine

Up to 10% of the population is allergic to cats. Mark Larché, the Canada Research Chair in Allergy & Immune Tolerance, and his colleagues have been working to help those people. In doing so, they not only created a cat allergy vaccine, but they are pioneering work on vaccines against other common allergens.

Allergic reactions result when patients’ immune systems attack innocuous substances, such as pollen or animal dander. Instead of ignoring such substances, the body produces a particular type of antibody called immunoglobulin E (IgE), which in turn leads to the release of the histamines and other chemicals that cause allergic symptoms.

Traditionally, there are two ways to treat cat allergies: avoiding cats, and getting allergen specific immunotherapy, a.k.a. allergy shots. Although the exact mechanism of how allergy shots work is not completely understood, it appears that repeated exposure to the allergens both desensitizes the immune system and increases the amount of a different type of antibody (IgG) which can outcompete IgE. Allergy shots can be highly effective, but they are also time consuming, expensive and uncomfortable. Most people must get shots as often as twice a week at first, and continue to get shots for several years.

Larché and his team chose a different approach. Rather than injecting patients with increasing doses of whole allergen, the researchers injected volunteers with synthetic peptides created from a cat protein that is known to be responsible for the majority of allergic symptoms. The peptide vaccine activated T-cells, and unlike allergen immunotherapy, did not stimulate the release of histamines. Nonetheless, the treatment resulted in insensitivity to cat allergen skin tests.

The required dosage to achieve effectiveness has yet to be worked out. Allergy sufferers will probably need multiple doses of the peptide vaccine to be symptom-free and it’s not clear how long the treatment will continue to work. On the plus side, peptide immunotherapy does not appear to cause the side affects associated with traditional immunotherapy (soreness and swelling at the injection site, or systemic reactions in severe cases). Whether the technique is also time and/or cost effective is yet to be determined.

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