Abstract
Most fish-allergic patients have anti-β-parvalbumin (β-PV) immunoglobulin E (IgE), which cross-reacts among fish species with variable clinical effects. Although the β-PV load is considered a determinant for allergenicity, fish species express distinct β-PV isoforms with unknown pathogenic contributions. To identify the role various parameters play in allergenicity, we have taken Gadus morhua and Scomber japonicus models, determined their β-PV isoform composition and analyzed the interaction of the IgE from fish-allergic patient sera with these different conformations. We found that each fish species contains a major and a minor isoform, with the total PV content four times higher in Gadus morhua than in Scomber japonicus. The isoforms showing the best IgE recognition displayed protease-sensitive globular folds, and if forming amyloids, they were not immunoreactive. Of the isoforms displaying stable globular folds, one was not recognized by IgE under any of the conditions, and the other formed highly immunoreactive amyloids. The results showed that Gadus morhua muscles are equipped with an isoform combination and content that ensures the IgE recognition of all PV folds, whereas the allergenic load of Scomber japonicus is under the control of proteolysis. We conclude that the consideration of isoform properties and content may improve the explanation of fish species allergenicity differences.
Highlights
Most fish-allergic patients have anti-β-parvalbumin (β-PV) immunoglobulin E (IgE), which cross-reacts among fish species with variable clinical effects
To simultaneously evaluate the role that content and β-PV isoforms play in the PV allergenic potency of fish species, we chose Gadus morhua and Scomber japonicus models given their difference in allergen load and the availability of two protein sequences and analyzed the interaction of the IgE of fish-allergic patient sera with the denatured, globular and fibrillary folded states of the β-PVs
For the muscles of fish species such as Gadus morhua and Scomber japonicus, which were taken as models of high and intermediate β-PV content, sequence banks provide two major sets of isoforms with pairwise sequence identities that are above 70%
Summary
Most fish-allergic patients have anti-β-parvalbumin (β-PV) immunoglobulin E (IgE), which cross-reacts among fish species with variable clinical effects. Consumed fish are restricted to a few orders, including Clupeiformes (herring, sardine, and anchovy), Cypriniformes (carp), Gadiformes (cod, pollock, and hake), Perciformes (perch, snapper, tuna, mackerel, and tilapia), Pleuronectiformes (sole and whiff), and Salmoniformes (salmon, trout, and whitefish)[33,34] Fish species from these orders differ in the total content of β-PV, the pattern of the expressed isoform and the tolerance in allergic patients[11,12,35,36,37,38,39]. To simultaneously evaluate the role that content and β-PV isoforms play in the PV allergenic potency of fish species, we chose Gadus morhua and Scomber japonicus models given their difference in allergen load and the availability of two protein sequences and analyzed the interaction of the IgE of fish-allergic patient sera with the denatured, globular and fibrillary folded states of the β-PVs. The results obtained provide novel variables that can be included in predictions of clinically relevant cross-reactivity from diagnostic tests
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