Delayed clinical and ex vivo response to mammalian meat in patients with IgE to galactose-alpha-1,3-galactose

Background: In 2009, we reported a novel form of delayed anaphylaxis to red meat related to serum IgE antibodies to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal). Although patients were remarkably consistent in their description of a 3-to 6-hour delay between eating mammalian meat and the appearance of symptoms, this delay has not been demonstrated under observed studies. Objectives: We sought to formally document the time course of clinical symptoms after the ingestion of mammalian meat in subjects with IgE to alpha-gal and to monitor ex vivo for the appearance of markers of an allergic reaction. Methods: Open food challenges were performed with mammalian meat in 12 subjects with a history of severe urticarial reactions 3 to 6 hours after eating beef, pork, or lamb, as well as in 13 control subjects. Blood samples were taken hourly during each challenge. Results: Ten of 12 subjects with IgE to alpha-gal had clinical evidence of a reaction during the food challenge (vs none of the control subjects, P <. 001). The reactions occurred 3 to 7 hours after the initial ingestion of mammalian meat and ranged from urticaria to anaphylaxis. Tryptase levels were positive in 3 challenges. Basophil activation, as measured by increased expression of CD63, correlated with the appearance of clinical symptoms. Conclusion: The results presented provide clear evidence of an IgE-mediated food allergy that occurs several hours after ingestion of the inciting allergen. Moreover, here we report that in vivo basophil activation during a food challenge occurs in the same time frame as clinical symptoms and likely reflects the appearance of the antigen in the bloodstream.