Food allergen families common to different arthropods (mites, insects, crustaceans), mollusks and nematods: Cross-reactivity and potential cross-allergenicity

Abstract

Allergies to animal foods essentially result from the consumption of shellfish, including crustaceans and mollusks, and even edible insects traditionally eaten in different countries around the world. In all of these countries, the statistical data collected during the last decade point out the consumption of shellfish products as a likely cause of the most severe allergic reactions associated to animal-based foods. The allergens responsible for the shellfish allergies mainly consist of pan-allergens belonging to a limited number of protein families, widely distributed in mites, crustaceans, insects, mollusks and nematods. Major allergens are represented by muscle proteins (tropomyosin, troponin C, myosin, sarcoplasmic calcium-binding protein) and enzymes (α-amylase, arginine kinase, glutathione S-transferase, serine protease, triosephosphate isomerase), associated to other functional (hemocyanin, hexamerin) and structural (tubulin) proteins. Most of these pan-allergens exhibit quite well conserved amino acid sequences and readily superposable three-dimensional structures. Although they remain closely phylogenetically-related, they fall into distinct groups more or less distantly related within the phylogenetic trees, depending of the proteins. In this respect, insect tropomyosins fall into two separate groups closely related to mite and crustacean tropomyosin groups, respectively, whereas the mollusk tropomyosin group deviates from all other tropomyosin groups. Alpha-amylase and arginine kinase groups of insects and crustaceans remain closely related but are much more distant from the corresponding groups of mite, mollusk and nematod enzymes. Overall, allergens from insects and crustaceans feel closer whereas mollusks allergens clearly differ from all the other allergen groups. According to these phylogenetic relationships, the IgE-binding cross-reactivities frequently reported between these allergens of different origin could trigger some unexpected crossed allergic reactions in susceptible individuals. In this respect, the consumption of edible insects by shellfish allergic patients should be avoided.