Abstract
BACKGROUND: Thaumatin-like proteins (TLPs) are conserved plant pathogenesis-related proteins with IgE-binding capacity, but their clinical relevance remains poorly defined. Unlike well-characterized panallergens, TLPs are underrepresented in diagnostic panels, and their role in food allergy is largely unexplored. OBJECTIVE: To assess the prevalence, quantitative IgE levels, co-sensitization patterns, and clinical significance of IgE reactivity to two TLPs-Act d 2 (kiwi) and Mal d 2 (apple)-in a large Italian allergic cohort. METHODS: We conducted a cross-sectional study of 7176 consecutive patients referred to Italian tertiary allergy centers. Specific IgE to TLPs and other plant allergens was measured using ALEX(2). Clinical outcomes were evaluated, and associations with IgE levels and co-sensitizations were examined using multivariate models. ROC analyses were applied to evaluate the discriminatory ability of Act d 2 IgE for clinical severity. RESULTS: TLP sensitization occurred in 137 patients (1.9%), predominantly to Act d 2. Isolated TLP sensitization was rare (n = 20) and associated with low IgE levels (mean 0.61 ± 0.98 kUA/L) and minimal symptoms. Co-sensitized patients (n = 117) had higher and more variable IgE levels (mean 1.41 ± 3.49 kUA/L) and experienced more clinically relevant reactions, including oral allergy syndrome and food-dependent exercise-induced anaphylaxis. ROC analyses indicated limited discriminatory power of Act d 2 IgE for predicting reaction severity (AUC 0.51-0.61). Multivariate adjustment confirmed no independent association between TLP-specific IgE and moderate or severe symptoms. CONCLUSIONS: TLP sensitization is uncommon and generally clinically silent when isolated. Co-sensitization with other panallergens appears to drive allergic manifestations. Quantitative TLP-specific IgE alone provides limited predictive value, emphasizing the importance of integrating molecular diagnostics with clinical phenotyping in precision allergy management.