PARVALBUMIN, A CROSS-REACTIVE FISH ALLERGEN, CONTAINS IGE-BINDING EPITOPES SENSITIVE TO PERIODATE TREATMENT AND CA2+ DEPLETION

Background: Type I allergy to fish is a severe health problem in count ries in which a large percentage of the population derive income from fishing. Objective: The aim of the study was to characterize crossreac tive IgE-binding components in six different fish species (cod, tuna, salmon, perch, carp, and eel). The effect of reducing extraction condi tions, periodate treatment, and depletion of Ca2+ on binding of IgE to the allergens was investigated. Methods: Extracts were prepared under nonreducing and reducing conditions, IgE-binding components were char acterized by IgE immunoblotting, and cross-reactive epitopes were stud ied by IgE-immunoblot inhibition experiments. To reveal calcium-sensit ive or carbohydrate-containing epitopes, nitrocellulose-blotted extrac ts were exposed to ethylene glycol bis(beta-aminoethyl ether) -N,N,N', N'-tetraacetic acid (EGTA) and periodate. Results: Sera from all patie nts allergic to fish (n = 30) displayed IgE reactivity to parvalbumin, a 12 kd protein present in fish extracts from six different species. Reducing extraction conditions had no effect on IgE binding to parvalb umins, whereas periodate treatment and depletion of protein-bound calc ium led to a substantial reduction of IgE binding. Parvalbumins from s ix different species contained cross-reactive IgE epitopes Conclusion: Parvalbumin represents a cross-reactive fish allergen. It contains Ig E epitopes that are sensitive to periodate treatment and Ca2+-depletio n.