Occupational asthma in a seafood restaurant worker: cross-reactivity of shrimp and scallops

Background: The case of a restaurant seafood handler with IgE-mediated occupational asthma and contact urticaria to both shrimp and scallops is presented. Independent hypersensitivity to both seafoods was demonstrated by skin testing, inhalation challenge, and immunoassays. Bronchial challenge with extracts of shrimp and scallops each produced an isolated early asthmatic response. Objective: To investigate cross-reactivity of shrimp (phylum Arthropoda) and scallops (phylum Mollusca). Methods: Shrimp and scallops extracts were prepared from raw seafood and seafood boiling water. Distillate was collected over boiling shrimp. Specific-IgE ELISA and immunoblot assays were accomplished for shrimp and scallops extracts inhibited by each other. Results: SDS-PAGE of shrimp boiling water and distillate showed similar protein patterns. SDS-PAGE and immunoblot demonstrated prominent protein allergens for shrimp boiling water at 21, 26, and 35 to 38 kD; for raw shrimp at 26 and 38 kD; for scallops boiling water at 20, 35 to 39 and 42 kD; and for raw scallops at 36 to 38 and 41 kD. Significant inhibition of the 35 to 39-kD band of each shrimp and scallops extract was demonstrated on immunoblot inhibition by seafood of the opposite phylum. IgE ELISA inhibition demonstrated 17% to 28% inhibition of shrimp by scallops and scallops by shrimp. Conclusions: Seafood allergens aerosolized during food preparation are a source of potential respiratory and contact allergens. Shrimp and scallops demonstrate significant cross-reactivity. These findings confirm that the primary cross-reactive allergen of shrimp (phylum Arthropoda) and scallops (phylum Mollusca) is the 35 to 39 kD heat-stable allergen, previously demonstrated to be muscle topomyosin in both phyla.