Bos d 13, A Novel Heat-Stable Beef Allergen.

SCOPE: Red meat, a staple food of Western diets, can also induce IgE-mediated allergic reactions. Yet, apart from the heat-labile protein serum albumin and the carbohydrate α-Gal, the molecules causing allergic reactions to red meat remain unknown. METHODS AND RESULTS: IgE reactivity profiles of beef-sensitized individuals are analyzed by IgE-immunoblotting with protein extracts from raw and cooked beef. Two IgE-reactive proteins are identified by peptide mass fingerprinting as myosinlight chain 1 (MYL1) and myosin light chain 3 (MYL3) in cooked beef extract and are designated Bos d 13 isoallergens. MYL1 and MYL3 are produced recombinantly in Escherichia coli. ELISAs proved their IgE reactivity and circular dichroism analysis showed that they represent folded molecules with remarkable thermal stability. In vitro gastrointestinal digestion experiments showed the higher stability of rMYL1 as compared to rMYL3. Exposure of a monolayer of Caco-2 cells to rMYL1 indicated that the molecule is able to cross intestinal epithelial cells without disturbing the integrity of the tight junctions, suggesting the sensitizing capacity of MYL1. CONCLUSION: MYLs are identified as novel heat-stable bovine meat allergens.

Gal d 7-a major allergen in primary chicken meat allergy.

BACKGROUND: Poultry meat can induce severe allergic reactions. So far, the molecules causing poultry meat allergy are largely unknown. OBJECTIVE: Our aim was to identify and characterize poultry meat allergens. METHODS: Profiles of patients' IgE reactivity to chicken muscle were analyzed in immunoblots, and proteins recognized by the majority of patients were subjected to peptide mass fingerprinting. A 23-kDa IgE-reactive protein was identified as myosin light chain 1, designated Gallus domesticus 7 (Gal d 7). Recombinant Gal d 7 was produced in Escherichia coli. The protein's IgE reactivity was analyzed in ELISA experiments, and cross-reactivity with allergens of other poultry species was assessed in inhibition immunoblots. Fold and thermal stability were evaluated by circular dichroism analysis, and enzymatic stability was investigated using in vitro gastrointestinal digestion assays. RESULTS: Recombinant Gal d 7 represents a properly folded, predominantly α-helical protein and displays IgE-binding activity comparable to that of its natural counterpart. IgE reactivity analysis in 28 patients allergic to chicken meat revealed that Gal d 7 is a major allergen for patients primarily sensitized to chicken meat. Furthermore, Gal d 7-cross-reactive allergens were also detected in other poultry species, suggesting that recombinant Gal d 7 can be used as a diagnostic marker allergen for poultry meat allergy. The high thermal stability, refolding capacity, and resistance to gastrointestinal enzymes might explain why Gal d 7 can act as a potent sensitizing agent. CONCLUSION: Gal d 7 represents a novel major chicken meat allergen. Recombinant Gal d 7 could be used for diagnosis of genuine poultry meat sensitization.

Update on the bird-egg syndrome and genuine poultry meat allergy.

Allergy to poultry meat is rare and affects both children and adults. The prevalence of poultry meat allergy is unknown, but presumably is similar to that of red meat allergy. There is no close relationship between allergy to poultry meat and allergy to red meat. Poultry meat allergy may present as primary (genuine) food allergy or as secondary food allergy resulting from cross-reactivity. Secondary poultry meat allergy may arise in the context of bird-egg-syndrome, which is due to sensitization to serum albumins present in many tissues including muscle tissue and egg yolk (Gal d 5). Primary sensitization to serum albumin may happen via the respiratory tract through exposure to pet birds (mainly in adults) or within the context of egg allergy in early childhood. Due to the heat lability of serum albumins, reactions are often limited to the skin upon contact with raw meat. Symptoms from meat ingestion are rare and mostly mild, whereas systemic reactions are common after ingestion of raw or soft-boiled egg yolk. Primary poultry meat allergy is mainly seen in adolescents and young adults, though hypersensitivity may have started already at (pre)school age. Egg allergy is usually absent. Typical symptoms of primary poultry meat allergy include OAS (±dyspnea), gastrointestinal complaints, urticaria and angioedema. Severe anaphylaxis with cardiovascular symptoms is rare. Chicken and turkey meat are highly cross-reactive and responsible for most reactions, while duck and goose meat causes milder or no symptoms. Soups, sausages, and ham represent relevant allergen sources, too. Patients with poultry meat allergy unexpectedly often suffer from concomitant allergy to fish and possibly shrimp. Serum specific IgE against fish and shrimp is found in respectively 60 and 40 % of sera, suggestive of cross-reactive allergens in these foods. The allergens thus far recognized in genuine poultry meat are LMW proteins of 5-25 kDa. One of them has been identified as α-parvalbumin cross-reactive with homologous mammal α-parvalbumins but not with fish α-parvalbumins. Recently, myosin light chains, including 23 kDa MLC-1 (Gal d 7) and 15 kDa MLC-3, have been recognized as new major allergens in chicken meat. The high similarity of chicken MLCs with those from various fish species (∼65 %) might explain the clinical association of poultry meat allergy with fish allergy.