α-Gal present on glycolipids and glycoproteins contributes to delayed response in meat-allergic patients, irrespective of the carrier molecule
Background: The α-Gal syndrome (AGS) is associated with the presence of IgE directed to the carbohydrate galactose-α-1,3-galactose (α-Gal) and is characterized by a delayed allergic reaction, occuring 2-6 hours after ingestion of mammalian meat. Based on their slow digestion and processing kinetics, α-Gal-carrying glycolipids have been proposed as the main trigger of the delayed reaction.
Objective: To analyse and compare the in vitro allergenicity of α-Gal-carrying glycoproteins and glycolipids from natural food sources.
Methods : Proteins and lipids were extracted from pork kidney (PK), beef and chicken. Glycolipids were purified from rabbit erythrocytes. The presence of α-Gal and IgE-binding of AGS patient sera (n=41) was assessed by thin layer chromatography, direct and inhibition ELISA. The in vitro allergenicity of glycoproteins and glycolipids from different meat extracts was determined by basophil activation test.
Results: α-Gal was detected on glycolipids of PK and beef. Patient IgE-antibodies recognized α-Gal bound to glycoproteins and glycolipids, although binding to glycoproteins was more potent. Rabbit glycolipids were able to strongly activate patient basophils, whereas lipid extracts from PK and beef were also found to trigger basophil activation, but at a lower capacity when compared to the respective protein extracts. Simulated gastric digestion assays of PK showed a high stability of α-Gal-carrying proteins in PK.
Conclusion: Both α-Gal-carrying glycoproteins and glycolipids are able to strongly activate patient basophils. In PK and beef, α-Gal epitopes seem to be less abundant on glycolipids than on glycoproteins, suggesting a major role of glycoproteins in delayed anaphylaxis upon consumption of these food sources.