Possible Allergenic Role of Tropomyosin in Patients with Adverse Reactions after Fish Intake

Abstract

In a recent case report, patient's anti-fish tropomyosin IgE was associated with gastrointestinal symptoms. We aimed to demonstrate on a wider scale that the panallergen tropomyosin should not be limited to invertebrate species and that clinically relevant reactions could be elicited by vertebrate tropomyosin. On the whole, 19 patients with adverse reactions after fish intake and showing negative skin tests with commercial fish extracts were included. Fish tropomyosin was recognized by 10/19 patients' IgE by immunoblotting. All patients with gastrointestinal complaints after fish intake (6/6) showed an IgE band matching with tropomyosin. Cod, albacore, and swordfish tropomyosins were recognized by most patients although 3/10 patients did not claim adverse reactions to these fish species. Immunoblotting with a battery of antigens from different fish species have a high yield of positivity at a band matching with tropomyosin molecular weight, even if they have not been claimed to be causative agents of symptoms. Tropomyosin is therefore a good candidate to be investigated as a clinically relevant fish allergen in patients who report adverse reactions after fish intake.

Effect of structural stability on endolysosomal degradation and T‐cell reactivity of major shrimp allergen tropomyosin

“…Tropomyosin is a highly conserved structural protein that has been the central focus of immunodiagnostic and therapeutic developments for shrimp allergy. Tropomyosin is the primary sensitizer in various crustacean and mollusk species, and a key player in our understanding of clinical cross‐reactivity in shrimp‐allergic patients on exposure to other invertebrate sources such as insects, 16,17 mites, 18 nematodes, 19 and more recently, even vertebrates such as fish 20,21 . However, it remains to be elucidated whether other invertebrate tropomyosins can also cross‐react on a T‐cell level.…”

Effect of structural stability on endolysosomal degradation and T-cell reactivity of major shrimp allergen tropomyosin

“…Tropomyosins have been key players in our understanding of clinical cross-reactivity in shrimp-allergic patients on exposure to other invertebrate sources such as insects 19,20 , mites 21 , nematodes 22 and more recently, even vertebrates such as fish. 23,24 Tropomyosin is the primary sensitizer in various crustacean species that leads to a strong Th2 response in humans and in small animal models 25 . However, it remains to be elucidated whether exposure to other invertebrate tropomyosins acts as a potent activator of shrimp-specific T cells and if shrimp tropomyosin (Pen m 1) shares identical cross-reactive T-cell epitopes with other allergenic tropomyosins due to its highly conserved sequence and heat-stable structure.…”

What Do We Know About Fish Allergy at the End of the Decade?

“…Subsequently, another group that used immunoblotting reported IgE-mediated immunoreactivity to tropomyosin from cod, yellow tuna, and swordfish in 10 of a cohort of 19 patients who presented with recurrent type I hypersensitivity following fish ingestion. It is particularly interesting to note that these patients had negative prick test results for commercial fish extracts [40]. The homology between invertebrate tropomyosin and fish tropomyosin is only 57%, which, theoretically, is not sufficient to lead to clinical cross-reactivity [39].…”

“…However, serum samples from patients with shellfish allergy do not recognize any of the tropomyosin samples from fish tested in vitro. One proposed hypothesis is that vertebrate tropomyosin is digested into smaller fragments than invertebrate tropomyosin and that these smaller fragments no longer form the 3-dimensional IgE epitopes that are found in invertebrate tropomyosin [40].…”