D1.279 - Vit v 5: A Chitinase Implicated in Grape-Induced Anaphylaxis
Case report
Introduction
Severe grape allergy has been mainly related to sensitization to lipid transfer protein (LTP), but other allergens such as profilins, thaumatins and endochitinases have been described.
Materials and Methods
We report the case of an 18-year-old woman with a history of rhino-conjunctivitis, allergic asthma due to pollen sensitization, cold urticaria, and urticaria induced by cefuroxime. In 2024, four hours after consuming rice with chicken and red grapes, during physical exercise, she developed anaphylactic symptoms, including dyspnea, ocular pruritus, angioedema and generalized urticaria, dizziness, and blurred vision. She was treated with intramuscular epinephrine and bronchodilators. Afterward, she tolerated rice and chicken but avoided grapes and other fruits, except bananas. A subsequent reaction occurred after consuming gazpacho with grape vinegar, leading to facial and glottic angioedema, managed at home with antihistamines and corticosteroids.
Diagnostic workup included skin testing with native food extracts, oral food challenges (OFC), serum-specific IgE measurements, and SDS-PAGE and Western blot analyses to evaluate protein profiles and IgE reactivity.
Results
Skin prick tests were positive for grape pulp (6x5mm) but negative for peach (peel/pulp), profilin and LTP-enriched peach extract. OFC with peach was negative. Total IgE was 671 kU/L. Negative levels of IgE for grape, Pru p 3 (LTP), Tri a 14 (LTP), Tri a 19 omega-5 gliadin, and Anisakis were detected. Basal serum tryptase was 3.25 µg/L.
Western blot revealed IgE binding to a protein slightly over 25 kDa in red grape extracts, absent in white grape extracts. This protein corresponds to Vit v 5, a chitinase with a molecular weight of approximately 28.5 kDa. SDS-PAGE indicated a higher abundance of this protein in red grapes compared to white grapes, explaining the differential IgE recognition (Figure 1).
Conclusions
This case highlights Vit v 5 as a potential allergen in grape-induced anaphylaxis. Vit v 5 was detected in red but not in white grapes, which may contribute to their increased allergenicity.
There may be less represented food allergenic proteins in some commercial extracts, however, understanding the allergenic profile is essential for accurate diagnosis and dietary recommendations, especially when reactions involve cofactors such as exercise.
