D1.03 - Identification of a Thaumatin-Like Protein as a Shared Allergen in Kiwi and Persimmon: Molecular Analysis in a Case of Anaphylaxis

Sensitization to multiple fruits can complicate the identification of the culprit allergen in anaphylaxis. Kiwi and persimmon share plant defence proteins with allergenic potential, although their clinical relevance is not fully understood. We report a case of anaphylaxis after ingestion of a mixed fruit juice, evaluated through molecular allergenic profiling.

A 50-year-old man experienced biphasic anaphylaxis after drinking kiwi, orange and persimmon juice, in the presence of cofactors (NSAIDs, possible post-exercise state). Prick-by-prick testing, serological assessment including ALEX², protein extraction from kiwi and persimmon under validated protocols, SDS-PAGE, IgE–Western blot under reducing and non-reducing conditions, and inhibition Western blot were performed. The IgE-reactive band shared by both fruits was submitted for LC-MS/MS proteomic identification.

Prick-by-prick testing was positive to kiwi (skin and pulp) and persimmon (pulp). IgE–Western blot demonstrated a shared ~18 kDa band in both fruits under non-reducing conditions. PR-10 and profilin were ruled out based on prior negative testing and incompatible molecular weight. Kiwi additionally displayed a 75–50 kDa IgE-reactive smear, suggesting the presence of partially reduction-resistant proteins. Inhibition Western blot showed complete inhibition between kiwi and persimmon extracts, confirming functional cross-reactivity. LC-MS/MS analysis identified the shared band as a Thaumatin-Like Protein (TLP), specifically Act d 2 in kiwi. Although TLPs typically have a theoretical mass around 24 kDa, experimental migration at <20 kDa has been previously documented.

The patient exhibits IgE-mediated sensitization to both kiwi and persimmon, driven by a shared Thaumatin-Like Protein, with confirmed cross-reactive epitopes. Molecular identification of TLP reconciles clinical history, cutaneous testing and serological findings, supporting kiwi as the primary sensitizer. This case highlights the diagnostic value of proteomic analysis in complex anaphylaxis involving mixed fruit exposures.