Reconstruction of fish allergenicity from the content and structural traits of the component β-parvalbumin isoforms

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.

Proteomics-Based Methodologies for the Detection and Quantification of Seafood Allergens

“…Moreover, the complete sequence of four β-PRVB isoforms (PRVB1 (P86431), PRVB1.1, PRVB2 (P86432), and PRVB2.1 variants) from farmed rainbow trout ( Oncorhynchus mykiss ) were achieved using matrix-assisted laser desorption (MALDI)MS and MS/MS analysis [ 53 ]. Such an isoform diversity impacts the stabilization of β-PRVBs as amyloids under gastric-like conditions, and consequently, their resistance to proteases and IgE binding intensity [ 54 , 55 , 56 ].…”

“…It must be recalled that extracts are usually prepared from raw fish muscles, limiting the presence of collagen that is more abundant in skin and the effects of processing. Furthermore, fish species muscles vary in the number and relative amount of the expressed β-PRVBs, each of which differs in stability and IgE interaction, introducing variables such as isoallergen composition, temperature treatments, and protease content, which is not yet controlled [ 56 ]. Indeed, about 30% of the individuals of a patient cohort having cross-reactive anti-β-PRVB IgEs showed oral tolerance to at least one of the fish species tested [ 94 ].…”