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Yolk protein extracts were prepared from four kinds of salmonid fish roes, and the proteins that reacted with IgE were screened by immunoblotting using sera from 20 patients allergic to chum salmon roe. IgE cross-reactivities among the salmonid yolk proteins were also investigated by competitive ELISA. The results were as follows: (1) The major protein components in salmonid roes were lipovitellin and beta'-component, which are subfragments of vitellogenin. (2) Most sera from the patients showed IgE reactivity to beta'-component in all yolk protein extracts, and some of them also reacted to lipovitellin heavy chain or its light chain. (3) Salmonid beta'-component showed high similarity (>90%) in the N-terminal amino acid sequence. (4) All of the salmonid yolk protein extracts inhibited the IgE reaction between patient sera and the chum salmon beta'-component. These findings indicate that the beta'-component in salmonid roe is a common major allergen with strong IgE cross-reactivity.

The β′-component, a major allergen found in fish roe, is synthesized in the liver of female fish as part of the precursor of the egg yolk protein vitellogenin (Vg). Vg is distributed through the bloodstream and contributes to ovary development. In the present study, β′-component, present in Vg fragments, was detected in the muscles and internal organs of mature female salmon, with concentrations exceeding the recommended labeling level under Japan's food allergy labeling system. Additionally, total protein extracted from tissues of female salmon reacted with immunoglobulin E antibody against the salmon roe β′-component. No β′-component was detected in the tissues of mature male fish in the absence of sex hormone stimulation from females nor in immature salmon without sexual differentiation, but excess stimulation of the female sex hormone induced Vg synthesis containing the β′-component in the male fish. These findings suggest that taking into account fish sex, maturity, and sexual isolation of mature male fish could improve the safety of salmon meat for individuals with salmon roe allergy. [ABSTRACT FROM AUTHOR]

The major allergenic protein in grey mullet roe was immunologically characterized using rabbit IgG against the β′-component, which is a vitellogenin fragment and the major allergen in chum salmon roe, and the IgE cross-reactivity between salmon and mullet roe was examined using chum salmon roe-allergic patients' sera. Grey mullet β′-component was identified in the yolk protein and consisted of 16 and 30 kDa proteins that showed marked reaction with the anti-β′-component IgG and shared N-terminal amino acid sequence similarity with vitellogenin. The grey mullet β′-component consisted of six different isoforms generated from vitellogenin A and vitellogenin B, and they inhibited the IgE-binding reaction between chum salmon β′-component and a chum salmon roe-allergic patient's serum. Thus, grey mullet roe may be an allergenic seafood capable of introducing IgE cross-reactivity to chum salmon roe through the β′-component. [ABSTRACT FROM AUTHOR]

Molecular characterization of a major allergen from salmon roeSalmon roe has a high allergic potency and often causes anaphylaxis in Japan. The major allergic protein of salmon roe is β′-component, which is a 35kDa vitellogenin fragment consisting of two subunits. To elucidate structural information and immunological characteristics, β′-component and the subunit components were purified from chum salmon (Onchorhincus keta) roe and vitellogenin-encoding mRNA was used to prepare β′-component subunit-encoding cDNA. This was PCR-amplified, cloned and sequenced and the deduced amino acid sequence compared with partial sequences of β′-component obtained by peptide mapping. The recombinant β′-component subunit was produced by bacterial expression in Escherichia coli and its IgE-binding ability was measured by ELISA using the sera of a patient allergic to salmon roe. This was then compared with that of the native β′-component with and without carboxymethylation. Following successful cloning of the cDNA encoding the β′-component subunit, 170 amino acid residues were deduced and matched with the amino acid sequences of 121 and 88 residues in the 16kDa and 18kDa subunits, respectively. The sequences of both β′-component subunits were almost identical, and the predicted secondary structure of the β′-component showed a high content of β-pleated sheets and no α-helices. There was no difference in IgE-binding ability between the native and recombinant β′-component subunits at the same protein concentration, regardless of carboxymethylation. In conclusion, β′-component is a homodimer protein composed of two isoform subunits having the same level of IgE-binding ability and, therefore, allergenic identity. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Terasi, Indonesian fermented shrimp paste, was prepared on a laboratory scale. • Tropomyosin, shrimp major allergen, was degraded during Terasi manufacturing. • Allergenicity of processed shrimp would be diminished during the Terasi production. • The allergen degradation has no impact on the Terasi quality. • Terasi becomes a low allergenic seafood by producing under appropriate conditions. Terasi is a fermented shrimp paste in Indonesia. We examined the effect of the Terasi manufacturing process on the abundance of the allergen tropomyosin (TM) and its IgG/IgE-binding ability. Terasi was produced from three shrimps, Akiami (Acetes japonicus), Okiami (Euphausia pacifica), and Isazaami (Neomysis awatchensis). Protein degradation and TM IgE-binding activity were examined by immunoblotting using anti-TM rabbit IgG and competitive enzyme-linked immunosorbent assays using shrimp-allergic patients' sera. The processing caused TM degradation, and the IgG-specific response in Akiami meat disappeared at the second fermentation step but remained in both Okiami and Isazaami Terasi. In contrast, TM IgE-binding in all meats decreased gradually during manufacturing and nearly completely disappeared in Akiami Terasi. Conclusively, Terasi production is an effective manufacturing process to reduce the IgE-binding ability of TM, and Terasi can be recognized as a low allergenic seafood when produced under an appropriate manufacturing condition. [ABSTRACT FROM AUTHOR]

Highlights • Salmon roe allergen (β′-c) orally administered to mice was detected by ELISA. • β′-c passed through the digestive tract without marked degradation. • β′-c was absorbed in the small intestine and circulated in blood stream. • The absorbed β′-c migrated through cytoplasm of the intestinal epithelial cells. Abstract The major allergen of chum salmon (Oncorhynchus keta) roe is the β′-component (Onc k 5, β′-c), which is a yolk protein and a fragment of vitellogenin. When yolk content containing β′-c was orally administered to mice, β′-c passed through the gastrointestinal tract and was excreted in feces without marked degradation. The direct administration of β′-c to ligated jejunal and ileal loops showed that β′-c was absorbed through the small intestine and transferred into the blood. Immunohistochemical staining showed that orally administered β′-c was distributed from the apical side to the basal side of intestinal epithelial cells, suggesting that endocytosis may be involved in the intestinal absorption of β′-c. In conclusion, β′-c is absorbed along a large portion of the small intestine and circulates in the blood stream without significant digestion. The resistance of β′-c to gastrointestinal digestion seems to contribute to its strong allergenicity. [ABSTRACT FROM AUTHOR]