Muscle Protein That Prompts Allergic Reactions to Invertebrates May Also Cause Allergic Reactions to Fish

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Tropomyosin, a well-known invertebrate pan-allergen, is a novel major allergen in fish, according to research originally slated for presentation at the 2020 AAAAI Annual Meeting.

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“This data demonstrates that patients who are allergic to fish could be responding to different proteins than we originally thought." - Thimo Ruethers, MSc

The muscle protein tropomyosin, a known pan-allergen in invertebrates such as shrimp and crab, also causes high Immunoglobulin E (IgE) reactions in vertebrate fish, according to research that was scheduled to be presented for the first time at the 2020 American Academy of Allergy, Asthma & Immunology (AAAAI) Annual Meeting before its cancellation due to the situation with coronavirus disease 2019 (COVID-19).

IgE are antibodies that are produced when the immune system overreacts to an allergen. To determine both the amount of IgE and the IgE cross-reactivity, the protein extracts of 66 fish species were analyzed for their allergen content. This was done using SDS-PAGE, immunoblotting, and advanced mass spectrometric analyses. Additionally, the serum IgE reactivity in 80 children and 12 adults with fish allergies was compared to 12 common fish such as cod, tuna, and salmon.

Researchers found the amount of tropomyosin was at least 10-fold higher in heated fish protein extracts than in raw ones, and a prominent tropomyosin band was found in 89% of the heated extracts. The IgE reactivity levels of tropomyosin was second only to parvalbumin, a calcium-binding protein which at this time is the only recognized major fish allergen.

The level of IgE reactivity varied between different species of fish. Catfish, for example, expressed 39% reactivity to parvalbumin and 34% to tropomyosin in pediatric patients, while cod parvalbumin was reported at 26% and cod tropomyosin at just 9%. Notably, over 50% of patients with IgE-binding to catfish tropomyosin showed no reaction to parvalbumin.

“This data demonstrates that patients who are allergic to fish could be responding to different proteins than we originally thought, and that what protein they experience a reaction to can vary greatly depending on the species of fish,” said first author Thimo Ruethers, MSc. “More work must be done to examine the clinical relevance and cross-reactivity between vertebrates and invertebrates when it comes to tropomyosin.”

Visit aaaai.org to learn more about food allergies. This research was published in an online supplement to The Journal of Allergy and Clinical Immunology.

The American Academy of Allergy, Asthma & Immunology (AAAAI) represents allergists, asthma specialists, clinical immunologists, allied health professionals and others with a special interest in the research and treatment of allergic and immunologic diseases. Established in 1943, the AAAAI has over 7,000 members in the United States, Canada and 72 other countries. The AAAAI’s Find an Allergist/Immunologist service is a trusted resource to help you find a specialist close to home.

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