Allergy to fish collagen: Thermostability of collagen and IgE reactivity of patients' sera with extracts of 11 species of bony and cartilaginous fish.

BACKGROUND: Parvalbumin was identified as a major fish allergen, and has been well investigated. Collagen was identified as a second allergen; however, its allergenic properties remain uncharacterized. Although fish is an important staple in coastal countries, its thermostability is unknown. Therefore, we aimed to determine the thermostability of fish collagen as an allergen. METHODS: Meat of seven bony and four cartilaginous fishes was heated at various temperatures and times, and extracts were analyzed using SDS-PAGE, IgE-ELISA, and SPTs. RESULTS: Collagen was dissolved from heated meat of Pacific mackerel into a crude extract. Collagen in the extracts was degraded at a high heating load-140 °C (10 min) or 100 °C (320 min). However, ELISA revealed the IgE reactivities of patients' sera with the extracts were unchanged even after heating the samples. Patients strongly reacted to extract proteins of other bony fish, which were detected by patients' IgE even after heating at 100 °C (320 min). In contrast, reactivities of the extracts of cartilaginous fish were lower than those of bony fish. SPTs in one patient revealed that all bony and cartilaginous fish extracts prepared from heated meat elicited allergic reactions. CONCLUSIONS: The IgE reactivity of patients' sera to fish collagen in extracts was retained even when fish meat was treated by a high heating load. As for the fish collagen, the IgE reactivities to cartilaginous fish were lower than that to bony fish. Reducing IgE reactivity to fish meat using heat is difficult, and other modalities will be required to produce hypoallergenic fish meat.

[A case of an allergic reaction due to Anisakis simplex after the ingestion of salted fish guts made of Sagittated calamari: allergen analysis with recombinant and purified Anisakis simplex allergens].

A 75-year-old man ingested salted fish guts made of Sagittated calamari which he caught in the daytime, with alcohol and then dozed. Five hours later, he woke up due to itching over his entire body and noticed generalized urticaria and a swollen tongue, which was too large for him to close his mouth. Serum total IgE was 456 IU/ml and ImmunoCAP was positive for anisakis, but negative for squid, shrimp, and ascaris. A skin prick test (SPT) was positive for anisakis extract (10 mg/ml) and house dust mites, but negative for squid and shrimp. He was diagnosed with IgE-mediated allergy due to Anisakis simplex after the ingestion of salted fish guts made of Sagittated calamari, which had been parasitized by Anisakis simplex. Furthermore, we performed SPT with six extracts of purified or recombinant allergens (Ani s 1, 3, 4, 5, 6, and 8) to identify the causative allergens in this case. Only Ani s 3 (tropomyosin) was positive, indicating that Ani s 3 was the causative allergen in this case. Third stage larvae of the nematode Anisakis simplex often parasitize not only marine fish but also invertebrates, including squid. It is necessary to consider Anisakis simplex allergy for urticarial reactions that develop after the ingestion of squid.