168 Tropomyosin is minor but distinct allergen in the patients with shrimp allergies

Abstract

Background: Crustacean groups such as shrimp is one of the most frequent causes of food allergic reaction in Japan as well as western countries. Cross-reactivity between crustaceans and other molluscs has been widely reported in shrimp-sensitive subjects. The purpose of study is to see an involvement of tropomyosin in the development of shrimp allergy in Japan. Methods: A total of 21 patients with shrimp allergy and 5 patients with atopic dermatitis (AD) who had no history of allergic reaction to shrimp but positive tropomyosin-specific IgE test were enrolled. Shrimp allergy patients were divided into three groups based on their symptoms: group I (oral allergy syndrome: OAS), group II (Urticaria), and group III (others). Tropomyosin-specific IgE was determined with CAP-fluorescent enzyme immunoassay and using IgE immunoblot. Involvement of carbohydrate in IgE-binding to allergens was examined by sodium periodate treatment. Results: Tropomyosin-specific IgE was detective in 4 (rate 50%) and positive in 3 (rate 37.5%) of the 8 patients in group I, detective in 3 (rate 30%) and positive in 1 (rate 10%) of the 10 patients in group II, and detective in 1 (rate 33.3%) and positive in 1 (rate 33.3%) in the 3 patients in group III. Upon IgE immunoblotting, serum IgE binding to purified tropomyosin was detected in the 5 patients with shrimp allergy; 3 patients in group I, 1 patient in group II, and 1 patient in group III, whereas no binding was seen in the 5 patients with AD. The IgE binding to 34-35 kDa bands was well compatible with the result of tropomyosin-specific IgE test. Periodate treatment indicated that the IgE-binding is not mediated by carbohydrate-moieties. Conclusion: Tropomyosin is minor but distinct allergen in the patients with shrimp allergy in Japan.