Advertisement

Allergy to pumpkin and cross-reactivity to other Cucurbitaceae fruits

      Keywords

      Abbreviations:

      EAACI: (European Academy of Allergology and Clinical Immunology)
      Fruits belonging to the Cucurbitaceae family
      • Anderson LB
      • Dreyfuss EM
      • Logan J
      • Johnstone DE
      • Glaser J.
      Melon and banana sensitivity coincident with ragweed pollinosis.
      have been reported to be one of the most important allergy-causing fruits in the United States. To the best of our knowledge, although pumpkin is a member of the above family and allergy to roasted pumpkinseed has been described, we have not found any indexed report concerning allergy to this fruit. The aim of our study was to describe the clinical and immunologic findings in this first reported case of allergy to pumpkin.

      Case report

      The patient was a 28-year-old woman with a history of rhinoconjunctivitis and asthma who was allergic to pollens and cat dander. She was referred to our clinic after development of several episodes of itching of the mouth, angioedema of the lips and face, generalized itching, and mild dyspnea within 15 minutes after eating pumpkin soup or thin vermicelli (sweet made from the fibrous part of the pumpkin). The patient required treatment with inhaled bronchodilator, antihistamines, and methylprednisolone in the emergency unit. She had not consumed any other food, beverages, or drugs coinciding with these episodes.

       In vivo tests

      Skin prick tests to an aeroallergen commercial battery (pollens, mites, fungi, and cat and dog dander) according to European Academy of Allergology and Clinical Immunology (EAACI) guidelines were positive to cat dander and most of the tested pollens (grasses, trees, and weeds).
      The skin prick-by-prick test responses with fresh fruits were positive to pumpkin (10 × 9 pseudopoda) and also to other Cucurbitaceae fruits: cucumber (5 × 4 mm), zucchini (4 × 3 mm), muskmelon (7 × 6 mm), and watermelon (7 × 3 mm).
      The open oral challenge test response to fresh pumpkin, according to the previously described method,
      • Cuesta-Herranz J
      • Lázaro M
      • Martínez A
      • Figueredo E
      • Palacios R
      • de Las Heras M
      • et al.
      Pollen allergy In peach allergic patients: sensitization and cross-reactivity to taxonomically non-related pollens.
      was positive, and it was also positive for cucumber, muskmelon, and watermelon.

       In vitro assays

      The pulp of several Cucurbitaceae fruits was processed according to the method previously described.
      • Cuesta-Herranz J
      • Lázaro M
      • Martínez A
      • Figueredo E
      • Palacios R
      • de Las Heras M
      • et al.
      Pollen allergy In peach allergic patients: sensitization and cross-reactivity to taxonomically non-related pollens.
      The initial protein content of the extracts was enriched by a method based on ion-exchange chromatography.
      • Martínez A
      • Fernández-Rivas M
      • Martínez J
      • Palacios R
      Improvement of fruit allergenic extracts for immunoblotting experiments.
      The protein concentration of all fruit allergenic extracts was adjusted to 1 mg/mL.
      SDS-PAGE and immunoblotting were carried out according to the methods previously described by Laemmli
      • Laemmli UK.
      Cleavage of structural proteins during the assembly of the head of bacteriophage T4.
      and Towbin et al.
      • Towbin H
      • Staenhelin Y
      • Gordon J.
      Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications.
      Polyacrylamide concentrations of 15% and 5% were used for separating and staking gels, respectively. IgE-binding bands were evaluated by means of immunoblot analysis, and the results are shown in Fig 1.
      Figure thumbnail gr1
      Fig. 1Immunoblot analysis of the binding of IgE antibodies with pumpkin (lanes 1) , cucumber (lanes 2) , marrow (lanes 3) , watermelon (lanes 4) , and melon (lanes 5) . A, IgE immunoblot without preincubation of patient's serum. B, IgE immunoblot after preincubation of patient's serum with pumpkin.
      Eight of the 15 bands identified in the pumpkin extracts by SDS-PAGE at a range of 8 to 109 kd were demonstrated to bind IgE. Interestingly, immunoblotting to other Cucurbitaceae extracts showed several IgE-binding bands shared between pumpkin and muskmelon (38.9 and 79.4 kd), watermelon (8.9, 13.8, and 67.6 kd), cucumber (8.9 and 13.8 kd), and zucchini (8.9 kd) extracts.
      Preadsorption of the serum with pumpkin extract (2 mg/mL) showed that pumpkin was capable of completely inhibiting all IgE-binding bands in cucumber and zucchini extracts. The pumpkin extract was also capable of producing a total inhibition of all bands in melon and watermelon, except the 41.6, 60, and 38.9 kd bands, which were partially inhibited.

      Discussion

      Pumpkin (Cucurbita pepo) is a robust annual plant that creeps on the ground. The fruits are large, variously shaped, and brown, with golden yellow flesh. Pumpkins are known throughout the world, and they are consumed in a variety of ways as a fresh or cooked vegetable, as well as being stored canned or frozen.
      We have reported a patient who experienced systemic reactions after eating cooked pumpkin. The diagnosis was based on a positive case history, positive skin test response and detection of specific IgE, and confirmed by an open oral challenge test to pumpkin.
      The results of in vivo and in vitro tests strongly suggest that these reactions were due to an IgE-mediated hypersensitivity mechanism to pumpkin allergens.
      Specific IgE-binding bands to other Cucurbitaceae extracts at the same molecular weight as pumpkin extract were revealed in the immunoblotting. Preadsorption of the sera with pumpkin extract demonstrated that these shared bands in Cucurbitaceae fruits were IgE-binding bands cross-reacting to pumpkin. This cross-reactivity was accompanied by clinical symptoms as supported by the open oral challenge.
      In conclusion, the most important facts to be emphasized in this case are that this is the first case reported in the literature of allergy to pumpkin on the basis of allergy symptoms, positive skin test responses, and challenge test to pumpkin. An IgE-mediated mechanism was strongly suggested, and cross-reactivity to other Cucurbitaceae fruits was demonstrated both in vivo and in vitro.

      References

        • Anderson LB
        • Dreyfuss EM
        • Logan J
        • Johnstone DE
        • Glaser J.
        Melon and banana sensitivity coincident with ragweed pollinosis.
        J Allergy Clin Immunol. 1970; 45: 310-319
        • Cuesta-Herranz J
        • Lázaro M
        • Martínez A
        • Figueredo E
        • Palacios R
        • de Las Heras M
        • et al.
        Pollen allergy In peach allergic patients: sensitization and cross-reactivity to taxonomically non-related pollens.
        J Allergy Clin Immunol. 1999; 104: 688-694
        • Martínez A
        • Fernández-Rivas M
        • Martínez J
        • Palacios R
        Improvement of fruit allergenic extracts for immunoblotting experiments.
        Allergy. 1997; 52: 155-161
        • Laemmli UK.
        Cleavage of structural proteins during the assembly of the head of bacteriophage T4.
        Nature. 1970; 277: 680-685
        • Towbin H
        • Staenhelin Y
        • Gordon J.
        Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications.
        Proc Natl Acad Sci U S A. 1979; 76: 4350-4354