Fruit allergies: Beware of the seed allergens!

Abstract

Anaphylactic reactions associated with the consumption of a number of fruits have been identified so far. Stone fruits belonging to the Rosaceae family have been particularly investigated in this respect, due to the occurrence of lipid transfer protein major allergens LTP, in both the pulp and the skin of the fruits. Other offending allergens like the PR-5 thaumatin-like proteins TLP, profilins and a variety of enzymes (β1,3 glucanase, chitinase) also occur in many fruits. However, stone fruits consist of another source of major allergens located in the fruit kernel, namely the cupin and 2S albumin allergens. Cupin allergens consist of three categories of seed storage proteins: germins (<7S protein), vicilins (7S globulins) and legumins (11S globulins). All of these allergens exhibit the canonical protomeric structure made of a single (germin) or two cupin motifs (vicilin, legumin) associated to two α-helical arms. In both proteins, three identical protomeric structures become non-covalently associated by their α-helical arms to form a flattened triangle-shaped homotrimer. Germins (90kDa) and vicilins (150kDa) consist of a single homotrimer whereas legumins result from the non-covalent stacking of two homotrimers to form a huge hexameric structure of 300kDa. Here, we present a catalogue of the cupin allergens distributed in the commonly consumed stone fruits. All of these cupin allergens behave as major allergens that are susceptible to trigger severe anaphylactic responses following their inadvertently consumption by previously sensitized consumers. In fact, it is noteworthy that kernels of a variety of stone fruits including apple, grape, physalis, tomato etc., are often consumed together with the pulp of the fruits. Faced with a fruit allergy, allergologists have to bear in mind the possible involvement of seed and kernel allergens in the fruit allergenic response. In this respect, both the measurement of cupin-specific IgE and the possible occurrence of allergic manifestations cross-linked to the consumption of other cupin-containing foods, should be useful to assess the severity of the fruit allergy, and to decide on the most appropriate management and treatment for this allergy.