Preparation and characterization of monoclonal antibody against abalone allergen tropomyosin

Muscle protein tropomyosin is a major and common allergen of mollusks. In order to develop immunoassays based on monoclonal antibody (MAb) for allergen characterization, a MAb against Japanese abalone (Haliotis discus) was prepared and characterized in the present study. In comparison with the IgE reactivities of sera from crustacean allergic individuals, the selected MAb AE9F9 showed specific reaction to the abalone allergenic tropomyosin. The MAb AE9F9 reacted to the crustaceans including lobster, crab, and shrimp, but not to the mollusks other than abalone. It was surprising that the MAb AE9F9 was also reactive to the vertebrate chicken tropomyosin and smooth muscle tropomyosin of chicken gizzard. Comparison of amino acid sequences of tropomyosins among abalone, other mollusks, crustaceans, and chicken showed that two regions (90-105 and 147-165) have a high identity among abalone, crustaceans, and chicken, but are polymorphic among mollusks. In the two regions, substitutions at residues 99-Leu, 149-Lys, and 160-Arg of abalone tropomyosin are observed only in mollusks, suggesting that these residues might be important for determining the abalone tropomyosin structure recognized by the AE9F9 antibody. Because of the distinct binding site, the MAb AE9F9 might be useful for abalone allergen detection and epitope mapping of allergen tropomyosin.