Cloning, Isolation, and IgE-Binding Properties of Helix aspersa (Brown Garden Snail) Tropomyosin

Abstract

Background: Gastropod consumption is quite frequent in the Mediterranean countries and cross-reactivities with crustaceans have been described, but the mechanism of this allergenic cross-reactivity has not been studied in detail. This study aimed to produce recombinant Helix aspersa (brown garden snail) tropomyosin and investigate its implication for cross-reactivity among invertebrates. Methods: A tropomyosin-specific cDNA encoding H. aspersa tropomyosin was synthetized, and recombinant allergen was overexpressed in Escherichia coli as nonfusion protein. IgE-binding reactivity was studied by immunoblotting and immunoblot inhibition experiments with sera from snail-allergic patients. Results: Cloned brown garden snail tropomyosin shares high homology with other edible mollusk tropomyosins (84–69% identity) as well as with those from arthropods (65–62%), and less homology with vertebrate ones (56% identity). Tropomyosin reacted with 18% of the sera from patients with snail allergy. Inhibition experiments, using natural and recombinant tropomyosins, showed different degrees of cross-reactivity between invertebrate tropomyosins. Sera from snail-allergic subjects recognized tropomyosins in both mollusks and crustacean extracts. Conclusions: Tropomyosin represents a minor allergen in snail extracts, but it is clearly involved in invertebrate cross-reactivity.