D3.13 - Molecular characterization of food allergens in a case of suspected honey and mustard allergy

Food allergy diagnosis has evolved significantly with the incorporation of molecular diagnostic techniques, which allow precise identification of specific allergenic proteins and improve the differentiation between true sensitization and cross-reactivity. We report the case of a 69-year-old woman with dyslipidemia treated with rosuvastatin who experienced a suspected food-induced allergic reaction with honey, corn and mustard.

Skin prick and prick‑prick tests were performed with LTP, corn, and different honey types. Protein extracts from rosemary honey, wildflower honey, mustard and corn were obtained by homogenization in phosphate-buffered saline (1:5 w/v), followed by incubation at 4°C for 16 hours, centrifugation, sequential filtration and lyophilization. Total protein concentration was determined using the Bradford assay. Specific IgE titration was performed by ELISA using patient serum incubated with allergen-coated plates (10 µg/mL). Protein and allergenic profiles were analyzed by SDS-PAGE under reducing conditions and IgE Western blot. Protein bands were visualized with Coomassie staining, and IgE-reactive bands were detected by chemiluminescence.

Skin prick-prick tests were positive for honey, mustard, and corn, and skin prick test was negative for LTP. Specific IgE was positive for Mustard (0,72 kU/L) and negative for: corn and mugwort. Honey specific IgE wasn´t available.  SDS-PAGE analysis showed a predominant protein band between 50–75 kDa in honey extracts and a major band between 10–15 kDa in mustard extract. IgE Western blot revealed negative results for rosemary honey, wildflower honey, and corn extracts, while mustard extract showed a positive IgE-binding band at approximately 12 kDa, likely corresponding to the non-specific lipid transfer protein (nsLTP) Sin a 3 (12.3 kDa). Molecular findings were consistent with serum specific IgE analysis but didn´t fully correlate with skin test results. Importantly, it should be considered that the patient was receiving statin therapy (rosuvastatin); according to scientific literature, statins may exert immunomodulatory effects and could potentially influence IgE levels, thereby affecting serological detection and interpretation of molecular allergy tests.

Molecular analysis identified mustard nsLTP (Sin a 3) as the most probable allergen responsible for the reaction. Negative results for honey and corn in Western blot may be explained by the loss of conformational epitopes during protein denaturation. Statins have immunomodulatory and anti‑inflammatory effects, which may directly or indirectly influence the presence of IgE in the patient’s serum, thereby hindering its detection. This case highlights the added value of molecular diagnostic techniques in clarifying discrepancies between conventional diagnostic methods and improving allergen identification in complex food allergy cases.