Atopic allergens of plant foods

The exact knowledge of what structural characteristics of an antigen are responsible for its allergenicity may not be available for several years. However, it is striking that the majority of the plant food allergens are clustered within a few protein families, and these are reviewed in this article. In most cases, plant food allergens are proteins that ensure the survival of the species as either seed storage proteins or proteins that are actively involved in the defence of the organism.     

A case of occupational contact urticaria and oral allergy syndrome due to seafood]

A 20-year-old woman was referred for evaluation after about 2 years of recurrent episodes of localized urticaria during handling of several kinds of raw fish in a sushi shop, where she had worked part-time for 2 years. She had also experienced allergic symptoms such as itching and swelling of her lips, generalized urticaria, laryngeal tightness, stridor and dyspnea immediately after ingestion of raw and cooked seafood, including sole, horse mackerel, sea eel and shellfish, over the previous 1 year before referral. Skin prick tests and blood test for specific IgE antibodies were positive for many kinds of seafood, including sole, horse mackerel, sea eel, eel, crab, and abalone, which belonged to different taxonomic phyla, including Chordata, Arthropoda, and Mollusca. A challenge with a piece of broiled sole induced swelling of the lips, obstruction of the larynx, difficulty with deglutition, and abdominal pain. In addition, serum-specific IgE antibodies to two major fish allergens, parvalbumin and collagen, were detected by ELISA, suggesting that allergic symptoms could be induced by many kinds of seafood in the present patient. She was therefore diagnosed with occupational contact urticaria and oral allergy syndrome due to seafood. At the time of this report, the present patient had been followed for one year and no reactions have occurred since she started to avoid the causative types of seafood.     

Relationships between oral allergy syndrome and sensitization to pollen antigen, especially to mugwort]

BACKGROUND: In order to know the relationships between mugwort pollinosis and oral allergy syndrome (OAS), an etiological study was performed at Muroran City, where mugwort is the most frequent cause of pollinosis. METHODS: Allergic rhinitis patients positive to serum IgE to birch, mugwort or grass pollen visited to the outpatient-clinic of Otorhinolaryngology of Muroran City General Hospital from 1998 to 2002, were studied by a questionnaire concerning a past-history of OAS. RESULTS: The prevalence of OAS was significantly higher in patients positive to serum IgE antibody specific to birch pollen or mugwort pollen than those negative to each pollen-specific antibody (birch; 54.5 vs 23.5%, p<0.0001, mugwort; 41.0 vs 21.5%, p<0.01). The main causative foods were fruits of rose family in patients with only birch pollen-specific IgE antibody, and were those other than rose family, such as kiwi, melon, orange, celery and onion in those with only mugwort pollen-specific IgE antibody. The patients group with high Lumiward score to mugwort pollen tended to include severe OAS cases. CONCLUSION: A close relationship was suggested between mugwort pollen sensitization and OAS.     

Correlation of oral allergy syndrome due to plant-derived foods with alder pollen, rbet v 1 and rbet v 2 sensitization in Yokohama region]

BACKGROUND.AIM: Oral allergy syndrome (OAS) to plant foods is often caused by cross-reactivity to pollen. We investigated whether there was any significant correlation between sensitization to the pollen of alder and Japanese cedar flying off in spring and prevalence of OAS in Yokohama region. METHODS: We measured specific IgE antibodies (CAP-FEIA: CAP) against alder and Japanese cedar in 337 outpatients with skin allergy in 2005 (M:F=167:170, 33.4 years of age, on the average). In the patients who showed positive response to CAP against alder and Japanese cedar, we also tested response to CAP against rBet v 1 and rBet v 2. In addition, we statistically analyzed whether there was any correlation between prevalence of OAS and sensitization to the pollen. RESULTS: Ratio of positive response to CAP against alder was 23.4% (79 cases) while that to CAP against Japanese cedar was 73.7% (244 cases). Response to CAP against rBet v 1 and rBet v 2 was tested in 55 cases, and the ratio of positive response to CAP against rBet v 1 was 43.6% (24 cases) while that to CAP against rBet v 2 was 27.3% (15 cases). Prevalence of OAS showed a significant positive correlation (p<0.001) with sensitization to alder, but no correlation with sensitization to Japanese cedar. CONCLUSION: It was suggested that sensitization to alder pollen would be involved in prevalence of OAS in Yokohama region.     

Molecular cloning of fungal allergens and clinical applications of recombinant allergens in fungal allergy]

A large number of fungi are associated with allergic disorders. There are many problems in using non-standardized fungal extracts for diagnosis of fungal allergy. These problems can be solved by using genetically engineered recombinant allergens. At present, more than 70 fungal allergens have been cloned and sequenced, and the recombinant forms of several of these are commercially available. Measurement of IgE antibodies to these commercially available recombinant allergens could provide the tools useful for characterizing the differential sensitization pattern in relation to a particular disease and the allergenic cross-reactivity among fungi. Only a limited number of recombinant allergens are available at present, thus further studies on the molecular biology of fungal allergens are needed so that more recombinant allergens can be used in the clinical field.     

Clinical characteristics of seafood allergy and classification of 10 seafood allergens by cluster analysis]

The aim of this study was to investigate the clinical characteristics of children who showed sensitization to any type of seafood and to classify the 10 seafood allergens based on IgE reactivities by a cluster analysis. In children with bronchial asthma (BA) and/or atopic dermatitis (AD), we defined the 'seafood' group as 23 patients having any type of seafood specific IgE antibody (CAP system). We analyzed the clinical features, the serum total IgE and each allergen specific IgE level. In addition, ten seafood allergens were also classified by a cluster analysis. Three patients revealed immediate hypersensitivity to some seafood. The frequency of patients with AD and the total IgE in the seafood group were high and the patients in this group were tend to be sensitized to multiple allergens. Seafood allergens were classified into 4 groups, 1) salmon, sardine, horse mackerel and mackerel, 2) cod and tuna, 3) octopus and squid, and 4) crab and shrimp, by a cluster analysis. These findings corresponded to the biological classification and the classification by the reported common allergens among various types of seafood. Based on our findings, this classification is therefore considered to be useful when selecting allergens to screen for sensitization to seafood.     

Detection and clinical characterization of patients with oral allergy syndrome caused by stable allergens in Rosaceae and nuts.

BACKGROUND: A minority of patients with oral allergy syndrome (OAS) induced by Rosaceae or nuts are positive on skin prick tests with commercial food extracts. This suggests reactivity against distinct stable allergens. OBJECTIVES: (1) To define the prevalence of subjects positive on skin prick tests with commercial extracts among patients with OAS caused by Rosaceae and/or nuts and (2) To investigate whether commercial extracts-positive subjects show some peculiar clinical feature and may represent a specific subset with food allergy. METHODS: Skin prick tests were carried out with a large panel of commercial extracts of airborne allergens (Allergopharma) and of vegetable foods (Dome/Hollister-Stier) in 298 adults with OAS caused by Rosaceae (n = 237) and or nuts (n = 161), positive on skin prick tests with fresh offending foods. RESULTS: 25/237 (11%) patients were positive on prick tests with commercial plum extract. This subgroup showed a higher incidence of systemic symptoms (64% versus 6%; P < .001) and a lower incidence of birch pollen allergy (12% versus 99%; P < .001) than commercial extract-negative patients; moreover, 36% versus 0%, respectively, did not have respiratory allergy (P < .001). Apple and peach were the main offending foods among commercial extract-negative and commercial extract-positive patients, respectively (87% versus 44% for apple, P < .001; and 52% versus 88% for peach, P < .005). Eight of one hundred sixty-one (5%) nuts-sensitive patients were positive on prick test with commercial walnut extract. This subgroup showed a higher proportion of patients who experienced systemic symptoms (63% versus 6%, P < .001), a lower prevalence of birch pollen allergy (13% versus 97%, P < .001), and a higher prevalence of grass pollen allergy (88% versus 41%, P < .05) than commercial extract-negative subjects. Further, reactivity against commercial walnut extract was associated with skin reactivity against commercial extracts of peanut (88% versus 37%, P < .005), tomato (75% versus 5%, P < .001), and plum (63% versus 8%, P < .001), and inversely related with skin reactivity against fresh apple (P < .001). In most cases, high levels of IgE specific for peach, apple, and hazelnut were associated with peanut reactivity rather than with clinical sensitivity to specific foods. In a preliminary investigation, most commercial extract-positive patients reacted against a 10-kDa protein characterized as a lipid transfer protein (LTP). CONCLUSIONS: Skin prick tests with commercial extracts of plum and walnut may be usefully employed to detect patients with OAS reacting against stable allergens. The high prevalence of systemic symptoms in these patients suggests that allergens' stability is associated with a higher resistance to the gastrointestinal environment and strongly influences the clinical expression of vegetable food allergy. At least some stable allergens, namely lipid transfer protein might be shared by botanically unrelated fruits such as nuts, peanuts, legumes, tomato, and Prunoideae.     

Clinical presentation,allergens, and management of wheat allergy

IgE-mediated allergy to wheat proteins can be caused by exposure through ingestion, inhalation, or skin/mucosal contact, and can affect various populations and age groups. Respiratory allergy to wheat proteins is commonly observed in adult patients occupationally exposed to flour, whereas wheat food allergy is more common in children. Wheat allergy is of growing importance for patients with recurrent anaphylaxis, especially when exercise related. The diagnosis of wheat allergy relies on a consistent clinical history, skin prick testing with well-characterized extracts and specific IgE tests. The accuracy of wheat allergy diagnosis may be improved by measuring IgE responses to several wheat components. However, a high degree of heterogeneity has been found in the recognition pattern of allergens among patient groups with different clinical profiles, as well as within each group. Thus, oral provocation with wheat or the implicated cereal is the reference test for the definitive diagnosis of ingested wheat/cereal allergy.     

Cross-reactivities between date palm (Phoenix dactylifera L.) polypeptides and foods implicated in the oral allergy syndrome

BACKGROUND: Date fruit and pollen antigens share a number of cross-reactive epitopes. Date pollen has been shown to cross-react with antigens from Artemisia, cultivated rye (Secale cereale), Timothy grass (Phleum pratense), Sydney golden wattle (Acacia longifolia) and Bermuda grass (Cynodon dactylon) pollen. The present study was carried out to examine any cross-reactivities between date palm polypeptides and antigens of some common foods and vegetables that have been implicated in the oral allergy syndrome (OAS). Because most of such cross-reactivities in other allergens are attributable to the presence of carbohydrate chains and profilin, their role was also investigated. METHODS: Fresh extracts of 20 common fruits and vegetables were prepared. Putative date profilins were isolated by affinity chromatography using a poly L-proline column. Date fruit extracts were digested by various endoglycosidases and the immunoglobulin (Ig)E binding of the postdigest products was assessed in immunoblots. Rabbit antisera to whole date fruit extracts, Timothy grass profilin and putative date profilins, as well as human sera from date sensitive individuals were used in immunoblotting, ELISA and in inhibition experiments. RESULTS: IgG, ELISA and immunoblot results with the different rabbit antisera and date-sensitive atopic sera showed several antigenic cross-reactivities and similar cross-reactivities were seen with birch, date and timothy grass profilins. IgE, ELISA and immunoblot experiments with pooled date sensitive human sera showed a range of cross-reactivities with some food extracts. A number of the IgE cross-reactivities could be inhibited after preabsorption of pooled sera with date extracts. Sixty-six percent of individual date hypersensitive human sera bound IgE in putative date fruit profilin and their pooled sera bound IgE in birch pollen profilin. IgE-binding of the endoglycosidase digested date fruit extracts to atopic serum pool was restricted to only a very low molecular weight band of 6.5-8 kDa. CONCLUSION: These results indicate that date palm polypeptides share cross-reactive IgG and IgE epitopes with a number of foods implicated in the oral allergy syndrome, bind to birch and Timothy grass profilins and bind IgE through glycosyl residues. The clinical relevance of these cross-reactivities needs to be further elucidated.     

Oral allergy syndrome (OAS): symptoms of IgE-mediated hypersensitivity to foods

Eighty highly atopic patients were selected for study because they had either atopic eczema (fifty cases) or atopic reactivity to foods, as judged by a positive skin-prick test (thirty cases). In all, sixty-five out of eighty subjects (81%) described symptoms of some kind provoked by foods, but correspondingly positive skin tests were found in only half of these, thirty-three out of eighty (41%). The symptoms experienced by thirty-one of the thirty-three patients with positive skin tests were immediate in onset (within 1 hr) and were at first confined to the upper gastrointestinal tract, the most frequent symptoms being oral irritation and throat tightness. In a proportion of these patients, further symptoms such as urticaria, asthma or anaphylaxis developed following the initial oral symptoms, which suggested the term'oral allergy syndrome'. In the absence of the oral allergy, symptoms such as asthma, urticaria, migraine or eczema starting later than 1 hr after food were seldom associated with positive skin tests. In the oral allergy syndrome, the characteristic symptoms (strong association with positive skin tests and RAST, time of onset and sites at which symptoms are expressed) suggest a causative relationship between exposure to food antigens and specific IgE-induced release of mediators. In cases of food intolerance that lack a characteristic symptom pattern and a positive skin test or radio-allergo-sorbent test, it seems appropriate to consider non-IgE-mediated causes.     

Recombinant birch allergens (Bet v 1 and Bet v 2) and the oral allergy syndrome in patients allergic to birch pollen.

BACKGROUND: IgE cross-reactivity between pollen and food allergens represents the molecular basis for oral allergy syndrome (OAS). OBJECTIVE: To evaluate specific IgE for Bet v 1 and Bet v 2 in the serum of patients sensitized to birch pollen and to identify whether IgE antibodies to Bet v 1 and Bet v 2 were predictors of OAS. METHODS: Thirty-three patients with skin prick test results and radioallergosorbent assay test results positive to birch pollen, 12 (36%) of whom had OAS symptoms, were enrolled in the study. Serum levels of specific IgE were determined by the fluoroenzyme immunoassay technique. RESULTS: The t test revealed significantly higher serum IgE levels against Bet v 1, Bet v 2, and birch pollen in the 12 symptomatic patients with respect to those without OAS (32.4 vs 12.4 kU/L, 7.6 vs 1.3 kU/L, and 42.3 vs 17.3 kU/L, respectively). Attempts to establish a threshold value of serum IgE antibirch pollen and the appearance of OAS revealed that a level of 20 kU/L or more yields an efficiency of the test equal to 70%. CONCLUSIONS: In our study, quantitative birch specific IgE level proved useful in predicting clinical allergy symptoms with birch exposure.     

Oral allergy syndrome due to plant-derived foods: a clinical review of 63 patients over a period of 6 years]

BACKGROUND: The clinical features of many patients with oral allergy syndrome (OAS) due to plant-derived foods have rarely been reported in Japan. OBJECTIVES: We aimed to determine the causative foods of OAS due to plant-derived foods based on clinical features and skin prick tests (SPTs). Furthermore, we aimed to elucidate the association between causative foods and sensitized pollens in patients with OAS due to plant-derived foods. METHODS: SPTs and specific IgE measurements (CAP-FEIA: CAP) were performed in relation to foods and pollens in 118 patients with positive histories of OAS due to plant-derived foods. Patients with positive histories and with positive skin test responses were identified as having type I allergy to the causative foods. RESULTS: The mean age of 63 patients with positive histories and positive skin test responses was 29.2 years (range, 2-61 years), and there were twice as many females as male. The most frequent causative foods were found to be apple, peach, kiwi, and melon in 13, 12, 12, and 11 patients, respectively. CAP frequency was shown to be similar to that of SPT regarding apple, whereas it was less than that of SPT regarding melon, peach, and kiwi. A significant correlation between the frequencies of SPT and CAP was found regarding apple (r=0.39, p<0.05) but not peach, kiwi, and melon. Forty-one of 63 patients with OAS (66.1%) had pollinosis and/or allergic rhinitis. In patients with OAS due to apple, the positive ratio of CAP response against alder pollen was higher than that in patients with OAS due to melon. In patients with OAS due to melon, the positive ratio of CAP responses against ragweed pollen, grass pollen, and mugwort pollen was higher than that in patients with OAS due to apple. CONCLUSION: In this study, positive ratios of SPT and CAP tended to differ according to the causative food, showing a smaller potential for reaction than might be suggested by patient history. Therefore, for the time being it would be more accurate to use a skin test for the diagnosis of OAS due to plant-derived foods.