D3.218 - When the sting is not the sensitizer: a vespid venom allergy case

Introduction 

Hymenoptera venom allergy is a potentially life-threatening condition. Venom immunotherapy is an effective and safe treatment and should be directed against the venom responsible for primary sensitization. Component-resolved diagnostics and inhibition assays help differentiate true sensitization from cross-reactivity and guide therapeutic decisions. 

Materials and Methods 

We report the case of a 36-year-old male patient who developed an episode of anaphylaxis following a wasp sting. Vespa crabro was identified as the culprit insect. Specific IgE to hymenoptera venoms and purified allergens was measured using ImmunoCAP® (Thermo Fisher Scientific). Total IgE was 464 IU/mL, and baseline serum tryptase was 3.39 µg/L. Specific IgE to whole venoms was positive for Vespula spp. (2.05 kU/L), Polistes spp. (4.04 kU/L), Polistes dominula (10.30 kU/L), Vespa crabro (1.23 kU/L), and Vespa velutina (0.53 kU/L). IgE to cross-reactive carbohydrate determinants (CCD; MUXF3 bromelain) was negative (0.03 kU/L). Component-resolved diagnostics showed specific IgE to Ves v 5 (3.13 kU/L) and Pol d 5 (6.76 kU/L), with negative Ves v 1 (0.06 kU/L). Specific IgG and IgG4 levels were as follows: IgG Polistes 4.30 mg/L, IgG Vespula 3.80 mg/L, IgG4 Vespula 0.26 mg/L, and IgG4 Polistes <0.15 mg/L. 

Results

Specific IgE levels to Polistes dominula were nearly fivefold higher than those to Vespula vulgaris and tenfold higher than those to Vespa crabro, suggesting Polistes dominula as the main source of primary sensitization. Inhibition assays were performed and showed no significant reciprocal inhibition between Polistes dominula and Vespula vulgaris venoms, indicating primary sensitization to both. In contrast, IgE reactivity to Vespa crabro venom was mainly inhibited by Polistes dominula venom, supporting cross-reactivity as the mechanism underlying the anaphylactic reaction. 

Conclusion 

The patient was diagnosed with vespid venom allergy due to primary sensitization to Polistes dominula and Vespula vulgaris, with anaphylaxis caused by Vespa crabro venom through cross-reactivity. Double venom immunotherapy with Polistes dominula and Vespula vulgaris venoms was initiated. This case highlights the importance of detailed diagnostic evaluation in hymenoptera venom allergy, as it may significantly influence therapeutic decisions.