Diagnostic problems due to cross-reactions in food allergy

It's not just the food you eat: Environmental factors in the development of food allergies

The dramatic rise in the prevalence of food allergy and food allergy-associated anaphylaxis in the past few decades has fueled investigative interest into understanding this puzzling trend. Here, we review the question as to whether important external environmental determinants beyond dietary habits and exposure to food allergens are involved. This review will summarize our current understanding of these environment determinants, derived from the latest experimental and epidemiological research. Specifically, we will review the role of exposures that affect skin barrier function, development of a diverse microbiome, and food processing. Additional exposures of concern are insufficient sunlight, endocrine disrupting chemicals and pesticides, and use of specific pharmaceutical agents that may drive or modify the risk for food allergy. Despite limitations in the quantity and quality of research to date, many new epidemiological associations and experimental data in support of this paradigm have emerged.

Sublingual Reactivity to rBET V1 and rPHL P1 in Patients with Oral Allergy Syndrome

Oral Allergy Syndrome (OAS) in patients with pollen-induced rhinoconjunctivitis is caused by specific IgE recognizing cross-reacting epitopes of fruits and plants, which were clearly shown in vitro, but failed to be demonstrated in vivo by cross-challenges in the target organs. Considering the hypothesis of degradation of such epitopes in natural extracts, challenges with recombinant pollen allergens were done to evaluate the reactivity of the oral mucosa in OAS patients. Seventeen patients with OAS and rhinitis from birch (10) and grass pollen (7) and 10 non-atopic controls were studied by skin prick tests (SPT), allergen specific nasal challenges (ASNC) and allergen specific sublingual challenges (ASSC) with birch and timothy extracts and with rBet v1 and rPhl p1 at increasing concentrations from 1 to 1000 mcg/ml. None of the healthy subjects in the control group had any positive test for birch and timothy extracts or for recombinant allergens. In the OAS group the following results were observed: SPTs with recombinant allergens were positive in all patients, mostly at 10 mcg/ml concentration; ASNC with rBet v1 were positive in all patients, mostly at 100 mcg/ml; ASSC with natural pollen extracts were positive in only 2 of 17 patients, but in 15 of 17 with rBet v1 and rPhl p1, mostly at 500 mcg/ml and 1000 mcg/ml. ASSC with rBet v1 and rPhl p1 were positive with a mean concentration of 677 and 533 mcg/ml, respectively. The results of sublingual challenges with rBet v1 and rPhl p1 showed the in vivo cross-reactivity between pollens and foods in patients with OAS, but high concentrations of the recombinant allergens were needed to reproduce oral symptoms, thus explaining the failure of challenges performed with natural extracts, which have concentrations of major allergens lower than 50 mcg/ml. This indicates that sublingual mucosa is much less reactive to allergens than other surfaces, such as skin and nasal mucosa, probably because of its anatomic and immunologic peculiarity.

Involvement of cross-reactive carbohydrate determinants-specific IgE in pollen allergy testing

Background

Specific IgE antibodies against the low-molecular-weight carbohydrate antigen that does not bridge IgE molecules on mast cells are not associated with clinical symptoms. Cross reactivity can be determined in allergen-specific IgE detection assays when the carbohydrate structures between pollen allergens and plant derived food allergens are similar; in such cases, false positive results for grain or legume allergens can be reported for pollen allergic patients who are not sensitized to those allergens. This phenomenon arises owing to the presence of cross-reactive carbohydrate determinants (CCDs).

Objective

This study aimed to assess the impact of CCD interference on the results for pollen allergen-specific IgE antibodies in the general adult population and to perform CCD inhibition tests evaluating the involvement of CCD on samples positive to pollen allergens.

Methods

Serum samples from 322 subjects were tested for IgE antibodies to pollens and CCD. The research subjects were given questionnaires about pollen allergic symptoms to help assess the presence of allergies. Allergen IgE antibodies for Japanese cedar, Japanese cypress, orchard grass, ragweed, MUXF, bromelain, horseradish peroxidase (HRP), and ascorbate oxidase (ASOD) were analyzed.

Results

It was observed that among individuals who tested positive to any of the pollen allergens, the positive ratio of CCD-specific IgE antibody was the highest for HRP (13.5%–50.0%). The results from the inhibition tests revealed that CCD was marginally present. Although IgE antibodies for cedar pollen did not react with CCD, IgE antibodies for Japanese cypress, orchard grass, and ragweed might be detected by the presence of CCD.

Conclusion

The results of the inhibition tests revealed the obvious presence of CCD suggesting its involvement. Considering these findings, careful evaluation of patient IgE results should be performed for Japanese cypress, orchard grass, and ragweed.

How relevant is panallergen sensitization in the development of allergies?

Panallergens comprise various protein families of plant as well as animal origin and are responsible for wide IgE cross-reactivity between related and unrelated allergenic sources. Such cross-reactivities include reactions between various pollen sources, pollen and plant-derived foods as well as invertebrate-derived inhalants and foodstuff. Here, we provide an overview on the most clinically relevant panallergens from plants (profilins, polcalcins, non-specific lipid transfer proteins, pathogenesis-related protein family 10 members) and on the prominent animal-derived panallergen family, tropomyosins. In addition, we explore the role of panallergens in the sensitization process and progress of the allergic disease. Emphasis is given on epidemiological aspects of panallergen sensitization and clinical manifestations. Finally, the issues related to diagnosis and therapy of patients sensitized to panallergens are outlined, and the use of panallergens as predictors for cross-reactive allergy and as biomarkers for disease severity is discussed.

Evidence for novel tomato seed allergens: IgE-reactive legumin and vicilin proteins identified by multidimensional protein fractionation-mass spectrometry and in silico epitope modeling

Tomato fruit and seed allergens were detected by IgE-immunoblotting using sera from 18 adult tomato-sensitized patients selected based on a positive history skin prick test (SPT) and specific Immunglobulin (Ig) E-levels. Isolated tomato seed total protein showed high SPT activity comparable or even higher than tomato fruit protein. For the molecular characterization of tomato seed allergens, a multidimensional protein fractionation strategy and LC-MS/MS was used. Two legumin- and vicilin-proteins were purified and showed strong IgE-reactivity in immunoblots. Individual patient sera exhibited varying IgE-sensitivity against the purified proteins. In silico structural modeling indicates high homology between epitopes of known walnut allergens and the detected IgE-crossreactive tomato proteins.

In vitro Analysis of Birch-Pollen-Associated Food Allergy by Use of Recombinant Allergens in the Basophil Activation Test

BACKGROUND

Basophil activation is associated with the expression of CD63. In birch-pollen-associated food allergy to celery, carrot and apple, Bet v 1, Api g 1, Dau c 1 and Mal d 1 are major allergens. Recombinant allergens have not yet been used in the CD63-based basophil activation test (BAT).

OBJECTIVE

To evaluate the feasibility of using recombinant allergens in the BAT in the diagnosis of allergy to apple, carrot and celery and to compare results with routine tests, i.e. skin prick tests (SPTs) and specific IgE.

METHODS

Thirty-two patients with an oral allergy syndrome induced by apple, carrot or celery and 22 controls were studied. SPTs were performed with native foods. Specific IgE was determined by the CAP method and basophil activation by flowcytometry upon double staining with anti-IgE/anti-CD63 monoclonal antibodies after incubating with purified recombinant Bet v 1, Bet v 2, Api g 1, Dau c 1 and Mal d 1.

RESULTS

By the combined use of the BAT and the CAP method, sensitization to Bet v 1 and Bet v 2 was detected in 100 and 25% of all subjects, respectively. Sensitivity of specific IgE for apple, carrot and celery was 60, 70 and 75% with corresponding specificities of 64, 86 and 82%. Sensitivity of the BAT for Mal d 1, Dau c 1 and Api g 1 was 75, 65 and 75% with corresponding specificities of 68, 100 and 77%.

CONCLUSIONS

The BAT using recombinant allergens provides a valuable new in vitro method for the detection of sensitization to foods. Although double-blind placebo-controlled food challenges remain the gold standard to confirm food allergy, the CD63-based BAT with recombinant allergens may supplement routine tests for allergy diagnosis.

Flow cytometric analysis of in vitro activated basophils, specific IgE and skin tests in the diagnosis of pollen-associated food allergy

BACKGROUND

Specific immunoglobulin E (IgE) and commercially available skin prick tests have been demonstrated to be unreliable methods to diagnose pollen-associated food allergy. To evaluate the predictive value of the basophil activation test (BAT) in pollen-associated food allergy, the apple-mediated oral allergy syndrome (OAS) in patients with birch pollinosis was chosen as a representative model.

METHODS

Patients with birch pollen allergy and a history of apple-mediated OAS (OAS(+), n = 29), patients with birch allergic without OAS (OAS(-), n = 22), and healthy controls (HC, n = 10) without birch pollen allergy and OAS were included. Apple IgE was quantified by the CAP FEIA method. Skin prick tests were performed with a Jonagold apple extract. Flow cytometric analysis of basophils activated with the same Jonagold extract was based on double staining with anti-IgE/anti-CD63 monoclonal antibodies.

RESULTS

Comparison between OAS(+) subjects and HC showed sensitivities and specificities of 96% and 100% for apple IgE and 88% and 100% for the apple skin prick test, respectively. For the BAT, sensitivity and specificity were 100%. In contrast, when nonresponders on the BAT were considered, sensitivity decreased to 90%. In a separate analysis between OAS(+) and OAS(-) subjects, specificities decreased to 30% for apple IgE and to 80% for the apple skin test, respectively. The BAT reached a sensitivity of 88% and a specificity of 75%.

CONCLUSION

Flow cytometry-assisted quantification of in vitro basophil activation seems to be a reliable instrument in the diagnosis of this model of pollen-associated food allergy. In addition, this study reemphasizes that the specificity of diagnostic allergy tests decreases considerably when, apart from HC, control individuals with cross-reactive antibodies are included.

Prevalence of adverse reactions to food in Germany - a population study

OBJECTIVE

A population study was performed to identify the prevalence of all kinds of adverse reactions to food.

METHODS

In a representative cross-sectional survey performed in 1999 and 2000 in Berlin, 13 300 inhabitants of all ages were addressed by questionnaire. This questionnaire was answered by 4093 persons. All respondents mentioning any sign of food intolerance or the existence of allergic diseases (n = 2298) were followed up by telephone and, in case food intolerance could not be ruled out by patient history, were invited to attend to the clinic for personal investigation including double-blind, placebo-controlled food challenge tests (DBPCFC).

RESULTS

The self-reported lifetime prevalence of any adverse reaction to food in the Berlin population (mean age 41 years) was 34.9%. Eight hundred and fourteen individuals were personally investigated according to the guidelines. The point prevalence of adverse reactions to food confirmed by DBPCFC tests in the Berlin population as a mean of all age groups was 3.6% (95% confidence interval [3.0-4.2%]) and 3.7% in the adult population (18-79 years, 95% confidence interval [3.1-4.4.%]). Two and a half percent were IgE-mediated and 1.1% non-IgE-mediated, females were more frequently affected (60.6%). Based on a statistical comparison with available data of adults from the nationwide German Health Survey from 1998, adverse reactions to food in the adult population of Germany (age 18-79) were calculated with 2.6% [2.1-3.2%]).

CONCLUSIONS

The study gives for the first time information about the point prevalence of both immunological and nonimmunological adverse reactions to food and underlines the relevance of this issue in public health. The data also show that an individualized stepwise approach including provocation tests is mandatory to confirm the diagnosis.

CD63 expression on basophils as a tool for the diagnosis of pollen-associated food allergy: sensitivity and specificity

BACKGROUND

Basophil activation is associated with the expression of CD63. Because allergens can induce basophil activation by cross-linking specific IgE, increased CD63 expression has been proposed as a novel in vitro test for immediate type allergy.

OBJECTIVE

We compared the CD63-based basophil activation test (BAT) in the diagnosis of allergy to carrot, celery and hazelnut with skin prick tests (SPT) and measurement of allergen-specific IgE.

METHODS

Twenty-nine patients with a history of an oral allergy syndrome induced by carrot, celery or hazelnut (n = 20 for each allergen) and 20 controls were studied. SPT were performed with standardized and native carrot, celery and hazelnut extracts. Allergen-specific IgE was determined by the CAP FEIA method and basophil activation was determined by flow cytometry upon double staining with anti-IgE/anti-CD63 mAb.

RESULTS

SPT with native carrot, celery and hazelnut showed sensitivities of 100%, 100% and 90%, and specificities of 80%, 80% and 90%. SPT with commercial extracts of the same allergens gave sensitivities of 85%, 80% and 85%, and specificities of 80%, 80% and 90%. Sensitivity of allergen-specific IgE and the BAT for carrot, celery and hazelnut was 80% vs. 85%, 70% vs. 85%, and 80% vs. 90%, with corresponding specificities of 80% vs. 85%, 80% vs. 80%, and 95% vs. 90%. The cut-off for a positive BAT was 10% CD63+ basophils. Moreover, there was a positive correlation between IgE reactivity and the number of CD63+ basophils for all food allergens (carrot: r = 0.69, celery: r = 0.67, hazelnut: r = 0.66).

CONCLUSIONS

Quantification of basophil activation by CD63 expression is a valuable new in vitro method for diagnosis of immediate type food sensitization. Although double-blind placebo-controlled food challenges remain the gold standard, the CD63-based BAT may supplement routine diagnostic tests such as SPT or allergen-specific IgE in the future.

Reactivity to potential cross-reactive foods in fruit-allergic patients: implications for prescribing food avoidance

BACKGROUND

Prescribing therapeutic elimination diets in patients with fruit allergy should include recommendations on which other foods of the same family or group may be safely consumed. Evidence-based data on the management of fruit allergy are lacking; therefore, advice may vary from just avoiding the offending fruit, to overly restrictive diets of the entire botanical family. The aims of this investigation were to assess clinical reactivity to potential cross-reactive foods in fruit-allergic patients, and the implications for prescribing specific therapeutic elimination diets.

METHODS

Sixty-five adults diagnosed with clinical allergy to one or more fruits were evaluated for IgE-mediated allergy to other related foods, which might share cross-reactive antigens. Those with actual allergy to some Rosaceae fruit (including peach, apple, apricot, plum, and almond) underwent skin prick testing (SPT), food-specific IgE assessment by the Pharmacia CAP-FEIA system, and oral challenges with the entire group. For those with allergy to other fruits (chestnut, melon, banana, kiwi, or avocado) immunologic and clinical reactivity to all five were evaluated. Since a number of people in the study also had proven clinically allergy to some nut or legume (peanut, sunflower seed, walnut, pistachio, or hazelnut), the reactivity to the entire set was investigated.

RESULTS

Thirty-four of those tested (52%) were found to be clinically allergic to more than one fruit, so 125 allergic reactions occurred in the 65 patients. Peach, melon, kiwi, apple, and banana accounted for 72% of allergic reactions. Forty-two (65%) had sensitization to pollens, causing seasonal allergic rhinitis and/or asthma, and 18 (28%) were sensitized to latex. The 65 with IgE-mediated fruit allergy underwent 351 additional SPT and food-specific IgE determinations with potential cross-reactive foods considered in this study; 223 (64%) of these results were positive. The routine challenges with potential cross-reactive foods uncovered 18 further reactions in 14 (22%) out of 65 (to avocado in seven; apricot in three; plum in one; almond and peanut in one; banana and hazelnut in one; avocado, banana and kiwi in one). Only 8% (18/223) of positive results for SPT, or food-specific IgE levels of greater than 0.35 kU(A)/l to potential cross-reactive foods investigated in this study, were clinically relevant.

CONCLUSION

Elimination diets that rely on total group avoidance, or only on the results of allergy testing, might have resulted in unnecessary restriction of 205 foods in the 65 people studied. The lack of routine oral challenges with related fruits--before prescribing dietary restriction--may have allowed 18 food reactions in one-fifth (14/65) of patients to be overlooked.

Recombinant food allergens

Allergenic (glyco)proteins are the elicitors of food allergies and can cause acute severe hypersensitivity reactions. Recombinant food allergens are available in standardised quantity and constant quality. Therefore, they offer new perspectives to overcome current difficulties in the diagnosis, treatment and investigation of food allergies. This review summarises the expression strategies and characteristics of more than 40 recombinant food allergens that have been produced until today. Their IgE-binding properties are compared to those of their natural counterparts, in addition their application as diagnostic tools, the generation of hypoallergenic recombinant isoforms and mutants for therapeutic purposes, the determination of epitopes and cross-reactive structures are described.

Mustard allergy in children

BACKGROUND

Mustard allergy is not well known. This study aimed to assess its clinical features and other associated allergies, and to define skin prick tests (SPT), specific IgE, and dose response by oral food challenge.

METHODS

Our study investigated 36 children with positive mustard SPT. The diagnosis of mustard allergy was based on open or single-blind, placebo-controlled food challenge (SBPCFC). We compared the subjects to 22 controls.

RESULTS

The initial clinical features were atopic dermatitis (51.8%), and urticaria and/or angioedema (37%). Fifteen children were allergic (positive SBPCFC) and 21 children were nonallergic (negative SBPCFC). Symptoms after mustard ingestion started under 3 years of age in 53.3% of the subjects. There was no significant difference in the food allergies and associated inhalant allergen sensitizations between the two groups. In the allergic group, the mean wheal diameter for mustard SPT was 8.8 mm and the median concentration of mustard serum (s) IgE 14.8 kU/l. The mean cumulative reactive dose were 153 mg.

CONCLUSIONS

Allergic reactions to mustard started early in life. Clinical symptoms were not severe in children. Mustard should be included in screening tests of food allergy in children.

Fennel, cucumber, and melon allergy successfully treated with pollen-specific injection immunotherapy

BACKGROUND

In subjects with both pollinosis and vegetable food allergy, most allergenic epitopes of fruits and vegetables are present in pollen. A recent study showed a marked reduction or a total disappearance of apple-induced oral allergy syndrome in patients receiving injection immunotherapy with birch pollen extracts.

OBJECTIVE

To assess whether vegetable food allergy following other kinds of primary pollinosis may be successfully treated with pollen-specific immunotherapy.

METHODS

A 34-year-old woman with long-standing pollinosis and typical oral allergy syndrome (OAS) with the ingestion of both fennel and cucumber and whose OAS was associated with immediate laryngeal edema after the ingestion of melon, was treated with two commercial depot aluminum hydroxide-adsorbed extracts of 1 grass pollen and 2 mugwort pollen 50% + ragweed pollen 50%.

RESULTS

After 36 months of injection specific immunotherapy, the patient was able to tolerate both fresh fennel and cucumber without consequence on open oral challenge tests. After 43 months of immunotherapy, the patient tolerated fresh melon as well on open oral challenge. She has re-introduced these vegetables in her normal diet. Skin tests showed no reactivity to fresh fennel and there was a reduction of the wheal induced by fresh cucumber.

CONCLUSION

Vegetable food allergy following primary sensitization to pollens, other than birch, may also be effectively reduced by pollen-specific injection immunotherapy.

Pollen allergy in peach-allergic patients: sensitization and cross-reactivity to taxonomically unrelated pollens

BACKGROUND

Fruit allergy has been attributed to cross-reactive IgE to pollens and has been associated with a particular pollen sensitization.

OBJECTIVE

The aim of the study was to evaluate sensitization to several taxonomically unrelated pollens in peach- and pollen-allergic patients and to study cross-reactivity between them.

METHODS

One hundred sixty-five patients were evaluated: 70 peach- allergic patients together with 95 pollen-allergic patients (control group). Pollen skin tests in duplicate were performed to 5 grasses, 8 trees, and 7 weeds. Cross-reactivity between peach and taxonomically diverse pollens was determined by radioallergosorbent inhibition and Western blot inhibition tests. Experiments were also carried out after preadsorption of the sera with purified natural profilin.

RESULTS

The skin test results revealed that peach-allergic patients frequently reacted to most pollens-grasses, weeds, and trees-even when some of these are not found in our geographic area. There was a statistically significant increase in sensitization frequency to most trees and weeds, with a statistically higher occurrence of asthma (odds ratio 2.98, 95% confidence interval 1.46-6.09). Inhibition test results provided evidence that taxonomically unrelated grasses, weeds, and trees produced various and substantial degrees of inhibition in specific IgE to peach and that the peach extract elicited strong inhibitions to those pollens. Profilin was found to be a relevant cross-reactive antigen in these patients.

CONCLUSION

The results of this study provide evidence that peach allergy is linked to sensitization to several taxonomically unrelated pollens. This is attributable to the ubiquitous nature of the IgE binding determinants-such as profilins-between peach and taxonomically unrelated pollens.