Fish allergens at a glance: variable allergenicity of parvalbumins, the major fish allergens

Abstract

Fish is a common trigger of severe, food-allergic reactions. Only a limited number of proteins induce specific IgE-mediated immune reactions. The major fish allergens are the parvalbumins. They are members of the calcium-binding EF-hand protein family characterized by a conserved protein structure. They represent highly cross-reactive allergens for patients with specific IgE to conserved epitopes. These patients might experience clinical reactions with various fish species. On the other hand, some individuals have IgE antibodies directed against unique, species-specific parvalbumin epitopes, and these patients show clinical symptoms only with certain fish species. Furthermore, different parvalbumin isoforms and isoallergens are present in the same fish and might display variable allergenicity. This was shown for salmon homologs, where only a single parvalbumin (beta-1) isoform was identified as allergen in specific patients. In addition to the parvalbumins, several other fish proteins, enolases, aldolases, and fish gelatin, seem to be important allergens. New clinical and molecular insights advanced the knowledge and understanding of fish allergy in the last years. These findings were useful for the advancement of the IgE-based diagnosis and also for the management of fish allergies consisting of advice and treatment of fish-allergic patients.

Keywords: allergenicity; fish allergy; fish gelatin; food allergy; isoallergens; isoforms; monosensitivity; parvalbumin.

Figure 1

Comparison of salmon (X97824, X97825), trout (FN544258, FN544259), and carp (P02618; 4cpv) parvalbumins. (A) Both salmonid beta-1 parvalbumins sequences differ from their homologs in the N-terminal third of the protein which is not involved in calcium binding. The allergenic peptide is specifically recognized by IgE from a patient monosensitized to salmonid fishes. Gray, identical residues; red, variable residues. (B) Both Ribbon and surface models show that the allergenic peptide is localized on the surface of salmon and trout beta-1 parvalbumins. Blue, calcium-binding regions; red, IgE epitope.