Paramyosin of the disc abalone Haliotis discus discus: Identification as a new allergen and cross-reactivity with tropomyosin

Tropomyosin, a 35–38 kDa myofibrillar protein, represents a major allergen in molluscs, as well as in crustaceans. Besides tropomyosin, a 100 kDa allergen was newly detected in the disc abalone Haliotis discus discus. The 100 kDa allergen was purified from the muscle of the disc abalone by salting-out and hydroxyapatite HPLC and identified as paramyosin based on the determined amino acid sequences of the peptide fragments produced by lysylendopeptidase digestion. Based on analysis by fluorescence ELISA, as many as 16 of the 18 patient sera tested, reacted to the disc abalone tropomyosin. The same patient sera also reacted to the disc abalone paramyosin, although rather less potently than to tropomyosin, suggesting that paramyosin is a major allergen. Immunoblotting data showed that IgE-reactive paramyosin is distributed in some species of molluscs other than the disc abalone. Interestingly, cross-reactivity between paramyosin and tropomyosin was demonstrated by inhibition immunoblotting and inhibition ELISA.