Cloning of two distinct cDNAs encoding parvalbumin, the major allergen of Atlantic salmon (Salmo salar)

Allergy to fish is common in Northern Europe. Variable reactions to different fish species are usually experienced among fish allergic patients. The allergens of cod fish and particularly the major allergen parvalbumin beta (Gadus callarias) have been extensively studied in Norway. In the present communication, the white muscle parvalbumin was similarly found to be a major allergen in Atlantic salmon (Salmo salar, Sal s1). A purified salmon parvalbumin was obtained by anion exchange chromatography, gel filtration chromatography (GFC) and high-performance liquid chromatography (HPLC) of the muscle extracts. The antigenicity and allergenicity of salmon parvalbumin were confirmed using various immunologic and electrophoretic techniques. The protein is representative for several isoallergens judged by the amino acid (AA) sequence variance at certain sites in the AA sequence of CNBr cleavage peptides. Using sera from patients with cod and salmon allergy Sal s1 was demonstrated to be the major allergen of Atlantic salmon, as judged by RAST- and ELISA-inhibitions and crossed radioimmunoelectrophoresis (CRIE) techniques. The protein was also demonstrated to be antigenic by the use of polyclonal cod and salmon antibodies in Ige ELISA and immunoelectrophoretic methods. Cloning of parvalbumin cDNA from Atlantic salmon was performed based on an alignment of parvalbumin AA sequences from other species. A probe was generated by PCR and used for screening a salmon muscle cDNA-library. Subcloning and sequencing of two hybridizing clones revealed transcripts from two different parvalbumin genes. The translated sequences of both clones belong to the beta-lineage of parvalbumins and include the entire coding region.