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

Abstract

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.

Keywords: Anaphylaxis; alpha-gal; basophil; food allergy; mammalian meat.

FIG 1

Representative urticaria appearing in patient FC-09 at 257 minutes after eating 150 g of pork sausage. The right flank is shown.

FIG 2

Basophil cell-surface expression of CD63 during mammalian meat challenge of patient FC-09 with IgE to alpha-gal (A) and control subjects (B and C). Whole blood was collected at baseline and hourly during a mammalian meat challenge, as described in the Methods section. CD63 expression peaked at hour 4 (63.1%) in the subject (Fig 2, A) and at hour 4 (24.5%) in a control subject (Fig 2, B). The control subject in Fig 2, C, did not show evidence of basophil activation.

FIG 3

Basophil CD63 expression at hourly time points in individual patients with positive results for IgE antibody (A) and control subjects (B) over the course of a mammalian meat challenge. P = .025 for mean maximal activation of patients (33.4 ± 6.4) versus control subjects (14.7 ± 4.6).

FIG E1

Gating strategy for the basophil activation assay. Basophils were identified by means of flow cytometry as HLA-DR^–lineage 1^– and then CD41^–CD123⁺ cells. Basophil activation was assessed based on expression of CD63 and reported as a percentage of CD63⁺ cells, with baseline set to 1%. APC, Allophycocyanin; FITC, fluorescein isothiocyanate.

FIG E2

Representative FACS contour plots from patient FC-02 using whole blood basophils stimulated in vitro for 30 minutes with medium (A), 50 μg of beef thyroglobulin (B), 5 μg of cetuximab (C), 5 μg of anti-IgE (D), and 10 μmol/L fMLP (E).

FIG E3

Representative FACS contour plots from patient FC-02 with IgE to alpha-gal using whole blood basophils stimulated in vitro for 4 hours with medium (A), 50 μg of beef thyroglobulin (B), 5 μg of cetuximab (C), 5 μg of anti-IgE (D), and 10 μmol/L fMLP (E).

FIG E4

Patient with IgE to alpha-gal (FC-08) demonstrating baseline forearms and palms (A) compared with distinct palmar erythema (B) that appeared at 4 hours and 38 minutes after eating 150 g of pork sausage.

FIG E5

A, Basophil cell-surface expression of CD63 during mammalian meat challenge of patient FC-08 shown in Fig E4. No sample was obtained at 6 hours because of clinical care of the subject. B and C, Additional photos of hives from patient FC-08.

FIG E5

A, Basophil cell-surface expression of CD63 during mammalian meat challenge of patient FC-08 shown in Fig E4. No sample was obtained at 6 hours because of clinical care of the subject. B and C, Additional photos of hives from patient FC-08.

FIG E6

Basophil cell-surface expression of CD63 (A) and supporting photos (B and C) during mammalian meat challenge of patient FC-03.

FIG E6

Basophil cell-surface expression of CD63 (A) and supporting photos (B and C) during mammalian meat challenge of patient FC-03.

FIG E7

A, Basophil cell-surface expression of CD63 during mammalian meat challenge of patient FC-06. B, Patient FC-06 before eating mammalian meat. C, Patient FC-06 at 6 hours and 45 minutes after consuming 150 g of mammalian meat.

FIG E7

A, Basophil cell-surface expression of CD63 during mammalian meat challenge of patient FC-06. B, Patient FC-06 before eating mammalian meat. C, Patient FC-06 at 6 hours and 45 minutes after consuming 150 g of mammalian meat.