D1.02 - Sensitization to Sesame Proteins Despite Negative Conventional Testing

Sesame seeds are one of the main causes of food-induced anaphylaxis, often in relation to storage proteins or oleosins. However, conventional diagnostic tools may fail to detect sensitisation, especially when allergenic components are underrepresented in extracts. Therefore, molecular profiling may be essential to reveal clinically relevant allergens in cases of discordant skin tests and specific IgE.

A 62-year-old man who experienced recurrent severe anaphylaxis following the ingestion of sesame oil and delayed urticaria following accidental exposure to sesame seeds underwent a diagnostic evaluation. Skin prick tests with a commercial sesame extract produced a negative result, and the patient's serum specific IgE to sesame was low (0.3 kU/L). His total IgE was 313 kU/L, and his tryptase level was normal (4.44 μg/L). Protein extracts from sesame seeds were separated into hydrosoluble and liposoluble fractions. SDS-PAGE and IgE-Western blotting were performed under both reducing and non-reducing conditions to characterise the protein and IgE-binding patterns.

Despite a clear clinical history of severe reactions, skin prick tests and serum IgE were negative. Western blotting revealed multiple IgE-reactive bands in both fractions: hydrosoluble extracts showed bands at ~40–45kDa, which are compatible with globulins. Additional subunit-sized bands (20–35kDa) were observed under reducing conditions. The liposoluble fraction displayed a distinct 17kDa IgE-binding band, which is consistent with oleosins. These IgE-binding patterns aligned with the patient’s clinical reactions to sesame oil and seeds.

This case demonstrates clinically relevant sensitisation to both globulins and oleosins in sesame, despite negative skin tests and low specific IgE levels. This highlights the limited representation of hydrophobic allergens in routine extracts and emphasises the importance of Western blot analysis as precise tools for identifying allergenic proteins in complex matrices, such as sesame oil and seeds.