Effect of thermal processing on IgE cross-recognition of insect proteins in Italian patients allergic to house dust mite, shrimp and mealworm.

INTRODUCTION. Edible insects are considered a promising and sustainable alternative protein source for humans, able to meet the increasing world's nutritional needs. The possible diffusion of insect farming and commercialization in Europe, has prompted the scientific community to investigate the allergenicity risk associated to insect consumption (1,2). Considering that edible insects are generally consumed after thermal processing, it is crucial to assess how processing may modify the protein structure, thus altering the protein cross-reactivity. In this study, we present one of the first investigations on insect cross-allergenicity, in three groups of Italian patients with a convincing history of house dust mite and shrimp allergy and with primary respiratory and food sensitization to mealworm. METHODS. We investigated by immunoblotting, the effect of boiling (5 min at 100 °C) and frying (3 min at 180 °C in sunflower oil) on the IgE-binding capacities towards both soluble and insoluble proteins fractions from five edible insects (mealworm, buffalo worm, silkworm, cricket and grasshopper). The immune-reactive proteins were identified by LC-MS/MS. RESULTS. Our data suggest that, depending on the nature of the reactive protein, the cross-reactivity resulted to be affected in different ways according to the different types of processing. In general, thermal processing influences the protein solubility, resulting in a protein shift from water-soluble to water-insoluble fractions, a shift that is more marked after frying than after boiling. Among the immune-reactive proteins, tropomyosin shows to have an important role as a cross-allergen for house dust mite and shrimp allergic patients and to be heat-stable in both fried and boiled samples. Actually, tropomyosin is considered a pan-allergen in crustaceans, mollusks, mites and insects, due to the high similarity of its amino acid sequences among species (3,4). The larval cuticle protein seems to play a major role in the cross-reactivity of patients primarily sensitized to mealworm. CONCLUSION. On the basis of our results, the effects of processing appeared to be protein-, species- and treatment-specific. Therefore, for patients allergic to house dust mite, shrimp and mealworm the consumption of insects, even after thermal processing, requires some caution.