D1.05 - IgE-Mediated Rice Allergy: The Role of Immunoblotting in Allergen Identification

Introduction: Rice is considered a low-allergenic food, and rice allergy is rare. Nevertheless, IgE-mediated hypersensitivity reactions, including anaphylaxis, have been reported, particularly in adults.

Methods: A retrospective analysis of clinical data was conducted, including medical history, reaction characterisation, and therapeutic management. Prick test and sIgE were conducted for accurate diagnosis. Immunoblotting was also performed. Briefly, proteins were separated by 15% SDS–PAGE, transferred to PVDF membranes (5 µg per lane), and incubated with human undiluted serum. Immunoreactive bands were visualized using an HRP-conjugated mouse anti-human IgE antibody and chemiluminescent detection.

Results: A 61-year-old male patient was followed in the Allergy and Immunology department after experiencing an anaphylactic reaction 10 minutes after consuming tomato rice, characterized by dyspnoea and lingual, labial, and periorbital angioedema. Treatment included 0.5 mg intramuscular adrenaline, 200 mg intravenous hydrocortisone, and 2 mg intravenous clemastine. Subsequently, he experienced an episode of skin pruritus and glottic, lingual, and periorbital oedema approximately 10 minutes after eating rice pudding. The patient also reported reproducible episodes of generalized pruritus, approximately 20 minutes after rice ingestion, since childhood, with spontaneous resolution. At the age of 23, he began working in rice production, reporting palmar pruritus immediately after contact with the grains. Following an evaluation in the allergology consultation, a skin prick test was performed using rice extract, which yielded a positive result with a 6 mm papule. A prick-prick test with cooked rice also produced a positive result, with a 4 mm papule. Specific IgEs for rice and other cereals were negative. An immunoblot was performed, which identified a protein with a molecular weight of 126 kDa, corresponding to a protein not yet described, two proteins with a molecular weight of 52 kDa, presumably corresponding to Ory s NRA or Ory s GLP52, and a protein with a molecular weight of 29 kDa, probably corresponding to Ory s 1.0101 (Figure 1).

Discussion: This case demonstrates an IgE-mediated rice allergy, likely due to primary gastrointestinal sensitisation, possibly worsened by occupational exposure to pollen and rice grains.

Molecular diagnostics, particularly immunoblotting, were crucial for allergen characterisation when conventional tests were inconclusive.

The identification of the storage proteins Ory s NRA, Ory s GLP52, and the aeroallergen Ory s 1 explains both ingestion-related reactions and occupational symptoms, while the 126 kDa protein may represent a previously uncharacterised rice allergen.

Conclusion: Although rare, rice allergy should be considered in food-induced anaphylaxis, and immunoblotting may improve diagnostic accuracy in atypical cases.