New allergen involved in a case of allergy to Solea solea, common sole

Epitope mapping of Atlantic salmon major allergen by peptide microarray immunoassay

BACKGROUND

IgE epitope mapping of allergens reveals important information about antigen elicitors involved in allergic reactions. The peptide-based microarray immunoassay offers an advantage of scale and parallel design over previous methods of epitope mapping. It has been used to map epitopes of some food allergens but has never been used with fish allergens.

OBJECTIVE

We sought to develop a peptide microarray immunoassay to map allergenic fish epitopes of two isoforms of Atlantic salmon (Salmo salar) parvalbumin, Sal s 1 beta 1 and Sal s 1 beta 2.

METHODS

Sera from 16 fish-allergic patients with specific IgE to salmon parvalbumin were used. Twelve healthy volunteers were used as negative controls. A library of overlapping peptides was synthesized commercially, representing the primary sequence of Sal s 1 beta 1 and Sal s 1 beta 2. Peptides were used to analyze allergen-specific IgE antibodies by immunolabeling with patient sera.

RESULTS

Three antigenic regions, not previously described, were identified in Sal s 1 beta 1. Two of them correlated with those previously reported in Gad c 1, parvalbumin from Baltic cod (Gadus callarias). No allergenic regions were found in Sal s 1 beta 2. This could be explained by crucial amino acid substitutions between isoforms.

CONCLUSIONS

We have identified three antigenic regions in Sal s 1 beta 1 using a peptide microarray immunoassay. These three sequential epitopes formed a unique antigenic determinant in the three-dimensional model of the protein. In addition, we proved that isoforms from the same protein might have a different allergenic behavior.

Identification of sole parvalbumin as a major allergen: study of cross-reactivity between parvalbumins in a Spanish fish-allergic population

BACKGROUND

Fish allergy is becoming an important health problem in Spain, a country with the third highest level of fish consumption after Japan and Portugal. The most common fish allergens are parvalbumins. In our area, the most widely consumed fish species are lean, such as whiff (Lepidorhombus whiffiagonis) and sole (Solea solea). Adverse reactions to fish are usually related to these species, a fact that is largely unknown to allergists in other countries.

OBJECTIVE

The aim of this study was to identify and purify the major allergen implicated in allergic response to sole and evaluate the IgE cross-reactivity of purified parvalbumins from whiff and sole, which are phylogenetically close, and more distant species (i.e. cod and salmon).

METHODS

Eighteen Spanish fish-allergic patients with a positive history of type I allergy to fish were recruited from the clinic. Total protein extracts and purified parvalbumins from whiff and sole were tested for their IgE-binding properties by combining two-dimensional Western blotting and mass spectrometry. The extent of cross-reactivity between these parvalbumins along with cod and salmon parvalbumins was investigated by IgE ELISA inhibition assay.

RESULTS

An IgE-binding spot of approximately 14 kDa was identified as parvalbumin and confirmed as a major allergen in sole extract, which is recognized by almost 70% of the patients. Whiff parvalbumin was recognized by 83.4% of the patients. High cross-reactivity was determined for all purified parvalbumins by IgE inhibition assay.

CONCLUSIONS AND CLINICAL RELEVANCE

Sole and whiff parvalbumin were confirmed as major allergens. The parvalbumins of sole, whiff, cod and salmon were highly cross-reactive, thus suggesting a high amino acid sequence identity between them.