A vaccine that includes a common food-borne pathogen reversed severe allergies to peanut, milk, and wheat in dogs, suggesting a possible treatment for the millions of people who suffer from food allergies.

Peanut and tree nut allergies affect approximately 3 million Americans and cause the most severe food-induced allergic reactions, including life-threatening anaphylaxis. There are no good treatments for these and other food allergies, and avoidance of the allergen is often the only way to prevent an allergic reaction in a sensitized patient.

The food-borne pathogen, Listeria monocytogenes, is a potent activator of T cells that has previously been shown to reduce the production of the IgE antibodies associated with allergic reactions and reverse allergen-induced airway hyperreactivity in mice. In the 12 November 2004 online edition of Allergy (doi: 10.1111/l.1398-9995.2004. 00711.x), a group led by Oscar L. Frick, Professor Emeritus of Pediatrics-Allergy-Immunology at the University of California, San Francisco, reports promising results in a study of dogs with severe food allergies.

The research team used nine dogs—four with peanut allergies and five with milk and wheat allergies. They inoculated the dogs with the pertinent antigen(s) and heat-killed L. monocytogenes (HKL). Following vaccination, the dogs underwent oral challenge with the offending foods, and the researchers monitored them closely for allergic symptoms, including vomiting, lethargy, and diarrhea. Even 10 weeks after vaccination, all of the dogs were able to tolerate significantly more of the trigger food with minor or no symptoms; indeed, one of the peanut-allergic dogs was able to eat a dose of ground peanut 100 times what would have caused a reaction before vaccination.

As the authors write in Allergy, “...these studies suggest that HKL as an adjuvant might be very effective as curative immunotherapy for allergic diseases, including allergic asthma and food allergy in humans.”