Manuel de las Heras

Identification of major allergens in watermelon.

Background: Watermelon is a worldwide consumed Cucurbitaceae fruit that can elicit allergic reactions. However, the major allergens of watermelon are not known. The aim of this study is to identify and characterize major allergens in watermelon. Methods: Twenty-three patients allergic to watermelon took part in the study. The diagnosis was based on a history of symptoms and positive skin prick-prick tests to watermelon, confirmed by positive open oral challenge testing to watermelon pulp. Allergenic components were detected by SDS-PAGE and immunoblotting. Molecular characterization of IgE-binding bands was performed by N-terminal amino acid sequencing and mass spectrometry. Allergens were purified combining several chromatographic steps. Results: Several IgE binding bands (8–120 kDa) were detected in watermelon extract. Three major allergens were identified as malate dehydrogenase (36 kDa), triose phosphate isomerase (28 kDa) and profilin (13 kDa). Purified allergens individually inhibited IgE binding to the whole watermelon extract. Conclusions: All in all these results indicate that malate dehydrogenase, triose phosphate isomerase and profilin are major allergens involved in watermelon allergy.

Successful desensitization of a fixed drug eruption caused by allopurinol

acquired sensitization and desensitization also differed between the human and the rabbit, with the rabbit requiring a shorter time to develop desensitization (14 weeks) than the human (21 weeks). This could represent a true difference. It could also have occurred because the human had less frequent mosquito bites than the rabbit and received a relatively low dose of mosquito salivary antigen (100 bites every 2 weeks in a 70 kg human vs 140 bites every week in a 2 kg rabbit). We demonstrate prospectively for the first time that regular, continuous, high-dose, natural allergen exposure eventually leads to desensitization (defined as complete loss of delayed and immediate responsiveness) and that both IgE and IgG are involved in the sensitization process. This model offers an excellent opportunity for further in-depth study of immediate and delayed hypersensitivity responses in humans. The immunologic mechanisms involved may be different in humans than in animals (at least in rabbits) in which IgG acts as a blocking antibody. We thank Dr. Reinhart Brust and Mr. Ben Yang Ding for their contributions to this work.

Clinical characteristics of melon (Cucumis melo) allergy.

Background Although melon is a frequent allergy-eliciting fruit, allergic reactions to melon have rarely been reported. Objective To evaluate and describe the clinical characteristics of melon allergy in melon-allergic patients. Materials and Methods We evaluated patients allergic to melon and a control group of patients allergic to pollen. The diagnosis of melon allergy was based on a convincing clinical history, positive skin test results (prick-by-prick test), and positive results on oral challenge tests to melon. Results A total of 161 patients were included in the study: 66 in the melon allergy group and 95 in the pollen control group. The melon allergy group included 35 female and 31 male patients with a mean age of 26.6 ± 2.7 years (range, 5-61 years). Although all patients had oral symptoms, 13 (19.7%) of the patients had extraoral symptoms and none experienced generalized urticaria or anaphylaxis. Excluding other Cucurbitaceae fruits, peach, fig, and kiwi most frequently elicited positive skin test results and symptoms. Up to 23% of melon-allergic patients had a concomitant latex sensitization. Melon allergy was especially linked to pollen allergy, since all the melon-allergic patients were also allergic to pollen. Some differential features with respect to the pollen allergy control group were a higher prevalence of asthma (odds ratio [OR], 2.13; P Ulmus (OR, 42.8) and Ambrosia (OR, 22.4). Conclusion The most important conditions linked to melon allergy are pollen allergy (100%), allergy to other nonrelated fruits, mainly peach (up to 62%), and latex sensitivity (up to 23%). Some differential features of the pollinosis in melon allergy were a higher prevalence of asthma and a higher frequency of sensitization to several weed and tree pollens.

Watermelon Profilin: Characterization of a Major Allergen as a Model for Plant-Derived Food Profilins

Background: Plant profilins have been reported as minor allergens. They are a well-known pan-allergen family responsible for cross-reactivity between plant-derived foods and pollens. Watermelon profilin has been reported to be a major allergen in watermelon (Citrullus lanatus).The aim of this study was to characterize recombinant watermelon profilin, confirming its reactivity for diagnostic purposes and the development of immunotherapy. Methods: Native profilin was purified from watermelon extract by affinity chromatography using poly-L-proline. Recombinant His-tagged profilin was produced in Pichia pastoris yeast using pPICZαA vector and purified by metal chelate affinity chromatography. ELISA and immunoblot were carried out with sera from 17 watermelon-allergic patients. Biological activity was tested by the basophil activation test. Results: Native profilin and recombinant profilin were purified and identified by mass spectrometry. Both show similar IgE reactivity in vitro and are biologically active. Conclusions: Similarities were found in the IgE-binding patterns and biological activity of recombinant profilin and native profilin. Recombinant profilin may be a powerful tool for specific diagnosis.

Molecular and immunological characterization of the first allergenic lipocalin in hamster: the major allergen from Siberian hamster (Phodopus sungorus).

Background: Exposure to uncommon pets such as a Siberian hamster has been described as a new risk factor for the development of allergic disease. Results: For the first time, we have cloned and characterized an allergen from Siberian hamster. Conclusion: The recombinant allergen shows a similar pattern of IgE binding and biological activity compared with salivary gland extract. Significance: The recombinant form will be useful for clinical applications. The most frequent pet allergy is to cat and dog, but in recent years, it has become increasingly popular to have other pets, and the risk of exposure to new allergens is more prevalent. The list of new pets includes hamsters, and one of the most popular hamsters is the Siberian hamster (Phodopus sungorus). The aim of this study was the characterization and cloning of the major allergen from this hamster. The study of its allergenicity and cross-reactivity could improve the specific diagnosis and treatment for hamster-allergic patients. Thirteen Siberian hamster-allergic patients were recruited at the outpatient clinic. Protein extracts were prepared from the hair, urine, and salivary glands of four hamster species (European, golden, Siberian, and Roborovski). IgE-binding proteins were detected by immunoblotting and identified by mass spectrometry. The recombinant protein was produced in Escherichia coli and then purified by metal chelate affinity chromatography. The allergenic properties of the recombinant protein were tested by ELISA and immunoblotting, and biological activity was tested according to capacity for basophil activation. Three IgE-binding proteins were identified in extracts obtained from Siberian hamster hair, urine, and salivary glands. All proteins corresponded to the same protein, which was identified as a lipocalin. This lipocalin had no cross-reactivity with common and golden hamsters. The recombinant allergen was cloned and purified, showing similar IgE reactivity in vitro to Siberian hamster protein extracts. Also, the recombinant allergen was capable of producing biological activation in vivo. The major Siberian hamster allergen was cloned, and allergenic properties were characterized, providing a new tool for specific diagnosis of allergy to Siberian hamster.

Nut Allergy in Two Different Areas of Spain: Differences in Clinical and Molecular Pattern

Introduction: Different clinical and molecular patterns of food allergy have been reported in different areas of the world. The aim of the study is to evaluate differences in allergen patterns among nut-allergic patients in two different areas of Spain. Material and methods: A total of 77 patients with nut allergy from two different regions of Spain (Madrid and Asturias) were evaluated. Results: Hazelnut, peanut, and walnut were the three most frequent nuts eliciting allergy in both regions, but in a different order. Patients from Madrid experienced systemic reactions more often than patients from Asturias (73.5% Madrid vs. 50.0%, p < 0.05). The percentage of sensitizations to LTP (Lipid Transfer Protein) was higher than Bet v 1 (p < 0.05) in the Madrid area. The percentage of sensitizations in Asturias area was similar to LTP than Bet v 1 (Pru p 3 46.4%, Bet v 1 42.9%, ns). Bet v 1 was the predominant allergen involved among hazelnut-allergic patients (56.2%), while LTP was more common in peanut-allergic patients (61.5%). Conclusion: Walnut, hazelnut, and peanut were the most frequent nuts eliciting allergy in Spain. Despite this, important differences in molecular pattern were appreciated not only between both regions, but also among nut-allergic patients in Asturias. The different molecular pattern was linked to the frequency of systemic symptoms.

Contact dermatitis to both tropicamide and phenylephrine eye drops.

To the Editor: The eye drops most frequently used in ophthalmology for diagnostic purposes are phenylephrine eye drops administered in combination with other mydriatic agents such as tropicamide and cyclopentolate (anticholinergic agents that produce mydriasis and cyclopegia). Referral of patients to our allergy department for the evaluation of allergy to mydriatic eye drops, drugs used both in diagnosis for retina scan and refraction due to ciliary muscle relaxant action, and in treatment of inflammatory diseases, is becoming increasingly frequent. Negative patch testing to eye drops is common, even with a positive history of an allergic reaction. Allergic contact dermatitis to phenylephrine is an infrequent but well-known complication. Despite similarities in the chemical structure of the offending substances, cross-reactivity between different sympathomimetic agents has not been well defined. We report a case of an 84-year-old man with conjunctival itching and hyperemia after instillation of eye drop containing phenylephrine, tropicamide, and double anesthetic (oxybuprocaine, tetracaine) for diagnostic purposes. The physical examination showed eyelid edema and desquamation 24 hours after the instillation. Epicutaneous tests were performed with 3 different phenylephrine reagents, a commercial battery of eye drop reagents (Marti Tor, Barcelona, Spain), and different commercial eye drops from Alcon Cusi (Barcelona, Spain), shown in Table 1. Results of patch tests were negative after 48 and 96 hours for all of the reagents. To confirm these negative results, the patient underwent a conjunctival challenge test following a method previously reported, using the eye drops involved in the reaction at intervals of 2 weeks after obtaining written informed consent. The results of the conjunctival challenge test were positive to Colircusi Fenilefrina and Colircusi Tropicamida eye drops eliciting substantial itching, periocular erythema, conjunctival hyperemia, and eyelid edema 8 hours after the instillation accompanied by eyelid desquamation in the following days. The result of the conjunctival challenge test was negative to Colircusi Anestésico Doble (oxybuprocaine, tetracaine), Colircusi Ciclopléjico, Colircusi Fluoresceı́na, and Tobrabact eye drops. We report a case in which a challenge test was used to successfully detect contact dermatitis to 2 mydriatic eye drops involved in an allergic reaction despite negative skin-test results to both substances. The diagnosis was based on a conjunctival challenge test to phenylephrine and tropicamide eye drops. Nonspecific reaction to eye drops in this patient was ruled out because the results of the challenge tests with double anesthetic, cyclopentolate, fluorescein, and tobramycin were negative. In addition, an adverse reaction to preservatives contained in the eye drops was ruled out because the results of a patch test and conjunctival challenge test with fluorescein and tobramycin eye drops were negative. This case report highlights the need to perform challenge tests using eye drops involved in allergic reactions to detect false-negative results obtained through skin testing. A positive finding of challenge tests to 1 substance does not rule out the possibility of a reaction to other mydriatic agents despite a patch test with negative findings. For this reason, in cases in which several mydriatic agents are involved, challenge tests should be performed to all substances.

Novel causes of drug-induced occupational asthma

Work-related asthma comprises occupational asthma (OA), which is caused by work, and work-exacerbated asthma, in which existing asthma is worsened by conditions in the workplace. OA is currently one of the most common types of occupational lung disease in industrialized countries. Investigation of work-related asthma first aims to demonstrate the presence of asthma and then objectively confirm its relationship to work. Diagnosing OA involves combining functional and inflammatory markers alongside environmental and immunological methods in a stepwise fashion. Briefly, diagnostic workup includes taking a detailed clinical and environmental history,