Effects of Boiling on the IgE‐Binding Properties of Tropomyosin of Shrimp (Litopenaeus vannamei )

Abstract

The thermal stability and IgE binding of raw and boiled shrimp extracts and the tropomyosins (TM) have not been reported. In this study, we compare the stability of raw and boiled shrimp TM of Litopenaeus vannamei and evaluate how boiling may alter the allergenicity of L. vannamei. Extracts were prepared from raw and boiled shrimp and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional electrophoresis. The IgE-binding of the extracts was determined by western-blot and competitive inhibition enzyme-linked immunosorbent assay (iELISA). The TM was then purified from raw and boiled shrimp, the secondary structures analyzed by circular dichroism (CD) spectroscopy, and the IgE binding compared by slot blot analysis. The soluble protein content decreased and the higher molecular weight proteins increased in the extracts from boiled versus raw shrimp. Similar IgE binding characteristics were seen by extracts when using western blot analysis. Although iELISA results showed that extracts from raw shrimp bound higher IgE than extracts from boiled shrimp, dot-blot assay demonstrates higher IgE binding to purified TM from boiled shrimp than raw shrimp. The purified TM had a typical alpha-helical secondary structure and the stability of boiled TM was lower than that of raw TM. Extracts from boiled shrimp produce lower IgE binding than extracts from raw shrimp, which suggest that boiling can be used as a tool in attempting to reduce shrimp allergenicity. However, the purified TM from boiled shrimp, which shows enhanced IgE binding over that of raw shrimp, may be a more effective antigen in diagnosing shrimp allergy through immunoassay.

Update on the Diagnosis and Treatment of Shellfish Allergy

“…The authors concluded that the use of boiled extracts seems to be more effective in diagnosing shellfish allergy. In an additional study, the thermal stability and IgE binding of raw and boiled shellfish extracts and tropomyosin were evaluated [27]. The soluble protein content as determined by ELISA and immunoblotting decreased, and the higher molecular weight proteins increased in the extracts from boiled versus raw shrimp.…”

Structural and Immunological Characterization of Recombinant Pan b 1, a Major Allergen of Northern Shrimp, <b><i>Pandalus borealis</i></b>

“…Natural Pan b 1 was extracted from boiled shrimps, but this was not associated with reduced IgE binding to tropomyosin in previous studies [21,35]. The reason for the differences in IgE binding in immunoblots therefore remains elusive.…”

Thermal and Nonthermal Methods for Food Allergen Control

“…A food sample that has Shrimp: whole shrimp decreased [70]; tropomyosin alone increased [14,70] Fish: parvalbumin unchanged (90°C) [4] or decreased (retorting) [8] Milk: casein unchanged [38]; whey decreased [65]; b-lactalbumin decreased [116] Egg: ovomucoid and ovalbumin unchanged [7,49] reduced IgE activity may indicate a modification or removal of food allergen(s). Allergen reactivity is most commonly determined by in vitro and in vivo testing.…”

“…Liu et al [70] found that IgE binding to boiled shrimp samples was decreased compared to the raw samples, as illustrated with dot blot and ELISA. However, tropomyosin elicited a greater immune response following boiling treatment confirmed by further in vitro analyses.…”