Allergen immunotherapy with heat-killed Listeria monocytogenes alleviates peanut and food-induced anaphylaxis in dogs

Background: Heat-killed Listeria monocytogenes (HKL) potently stimulates interferon (IFN)-gamma production in CD4 T-lymphocytes, and when used as adjuvant for immunotherapy, reduces immunoglobulin (Ig)E production and reverses established allergen-induced airway hyperreactivity (AHR) in a murine model of asthma. We asked if such treatment could decrease established peanut-induced anaphylaxis or cow's milk-induced food allergy in highly food-allergic dogs. Methods: We therefore studied four 4-year-old atopic colony dogs extremely allergic to peanut (Group I), as well as five 7-year-old dogs very allergic to wheat, milk and other foods (Group II). All dogs experienced marked allergic symptoms, including vomiting and diarrhea on oral challenge with the relevant foods. The dogs were then vaccinated once subcutaneously with peanut or milk and wheat with HKL emulsified in incomplete Freund's adjuvant. Results: Following vaccination of the allergic dogs with HKL and allergen, oral challenges with peanut (Group I) or milk (Group II) elicited only minor or no symptoms. In addition, skin test end-point titrations showed marked reductions for >10 weeks after treatment, and levels of Ara h 1-specific IgE in serum of peanut sensitive dogs, as demonstrated by immunoblotting, were greatly reduced by treatment with HKL plus peanut allergen. Conclusions: Thus, HKL plus allergen treatment markedly improved established food allergic responses in dogs, suggesting that such an immunotherapy strategy in humans might greatly improve individuals with food allergy and anaphylaxis.