Sublingual immunotherapy for hazelnut food allergy: a randomized, double-blind, placebo-controlled study with a standardized hazelnut extract

BACKGROUND

Food allergy may be life-threatening, and patients affected need to receive accurate diagnoses and treatment. Hazelnut has often been implicated as responsible for allergic reactions, and trace quantities can induce systemic reactions.

OBJECTIVE

The aim of this study was to evaluate the efficacy and tolerance of sublingual immunotherapy with a standardized hazelnut extract in patients allergic to hazelnut.

METHODS

This was a randomized, double-blind, placebo-controlled study. Inclusion criteria were a history of hazelnut allergy and positive skin prick test and double-blind placebo-controlled food challenge results. Patients were then randomly assigned into 2 treatment groups (hazelnut immunotherapy or placebo). Efficacy was assessed by double-blind, placebo-controlled food challenge after 8 to 12 weeks of treatment. Blood samples were drawn for measurement of specific IgE, IgG(4), and serum cytokines before and after treatment.

RESULTS

Twenty-three patients were enrolled and divided into 2 treatment groups. Twenty-two patients reached the planned maximum dose at 4 days. Systemic reactions were observed in only 0.2% of the total doses administered. Mean hazelnut quantity provoking objective symptoms increased from 2.29 g to 11.56 g (P = .02; active group) versus 3.49 g to 4.14 g (placebo; NS). Moreover, almost 50% of patients who underwent active treatment reached the highest dose (20 g), but only 9% in the placebo. Laboratory data showed an increase in IgG(4) and IL-10 levels after immunotherapy in only the active group.

CONCLUSION

Our data confirm significant increases in tolerance to hazelnut after sublingual immunotherapy as assessed by double-blind, placebo-controlled food challenge, and good tolerance to this treatment.

The natural history of tree nut allergy

BACKGROUND

Although 20% of children outgrow peanut allergy, the natural history of tree nut (TN) allergy has not been well studied.

OBJECTIVE

The goals of the study were to estimate the proportion of children who outgrow TN allergy and examine predictors of outgrowing it.

METHODS

Patients with TN allergy, defined as a history of reaction on ingestion and evidence of TN-specific IgE (TN-IgE) or positive TN-specific IgE level but no history of ingestion, were evaluated. If all current TN-IgE levels were less than 10 kilounits of antibody (kU(A))/L, double-blind, placebo-controlled food challenges were offered. Patients who had undergone open TN challenges as part of routine clinical care were also included.

RESULTS

Two hundred seventy-eight patients with TN allergy were identified. One hundred one (36%) had a history of acute reactions, 12 (12%) of whom had reactions to multiple TNs and 73 (63%) of whom had a history of moderate-to-severe reactions. Nine of 20 patients who had previously reacted to a TN passed challenges, so that 9 (8.9%; 95% CI, 4% to 16%) of 101 patients with a history of prior TN reactions outgrew TN allergy. Fourteen of 19 who had never ingested TNs but had detectable TN-specific IgE levels passed challenges. One hundred sixty-one did not meet the challenge criteria, and 78 met the criteria but declined challenges. Looking at specific TN-IgE cutoffs, 58% with TN-IgE levels of 5 kU(A)/L or less and 63% with TN-IgE levels of 2 kU(A)/L or less passed challenges.

CONCLUSIONS

Approximately 9% of patients outgrow TN allergy, including some who had prior severe reactions. Although ideal cutoffs for challenge cannot be firmly recommended on the basis of these data, patients aged 4 years or older with all TN-IgE levels of 5 kU(A)/L or less should be considered for challenge.

Identification of an 11S globulin as a major hazelnut food allergen in hazelnut-induced systemic reactions

BACKGROUND

Hazelnuts are a common cause of food allergy. Allergic reactions to hazelnuts range from oral allergy syndrome caused by cross-reactivity between tree pollen and hazelnut proteins to severe anaphylactic reactions. Little information is available regarding the identification of pollen-independent hazelnut allergens.

OBJECTIVE

The aim of the study was to identify these pollen-independent allergens in patients with hazelnut allergy with systemic reactions.

METHODS

Extracted hazelnut proteins were separated by means of 2-dimensional PAGE, and immunolabeling was performed with individual sera from 14 patients with hazelnut-induced systemic reactions. Edman sequencing was performed on a 40-kd protein identified as an allergen. In parallel, RNA isolated from hazelnuts was used to construct a cDNA library. By using the peptide sequence data, oligonucleotide primers were synthesized and used to screen the library. Full-length cDNA clones were isolated, sequenced, expressed, and screened with patient sera.

RESULTS

By using 2-dimensional proteomics, a protein fraction at 40 kd was recognized by serum IgE from 86% (12/14) of the patients with hazelnut allergy with systemic reactions. Two internal amino acid sequences were determined by means of Edman sequencing. Screening of the prepared hazelnut cDNA library with oligonucleotides based on these internal peptide sequences resulted in isolation of a novel protein cDNA. The new protein, named Cor a 9, belongs to the 11S globulin seed storage protein family. This family comprises known food allergens in peanut (Ara h 3) and soybean (glycine max). The pairwise homology among these 3 proteins ranges from 45% to 50%. Interestingly, one known IgE-binding epitope of Ara h 3 shares 67% of homologous amino acid residues with the corresponding area of Cor a 9. The amino acids that differ were previously shown not to be critical for IgE binding in Ara h 3.

CONCLUSION

Cor a 9 is the first tree pollen-unrelated hazelnut allergen isolated, sequenced, and cloned. The identification of food allergens is the first step toward generating recombinant allergens for use in future immunotherapeutic approaches. In addition, the detection of conserved IgE epitopes in common food allergens, such as seed storage proteins, might be a useful tool for predicting cross-reactivity to certain foods.

Tree nut allergens

Allergic reactions to tree nuts can be serious and life threatening. Considerable research has been conducted in recent years in an attempt to characterize those allergens that are most responsible for allergy sensitization and triggering. Both native and recombinant nut allergens have been identified and characterized and, for some, the IgE-reactive epitopes described. Some allergens, such as lipid transfer proteins, profilins, and members of the Bet v 1-related family, represent minor constituents in tree nuts. These allergens are frequently cross-reactive with other food and pollen homologues, and are considered panallergens. Others, such as legumins, vicilins, and 2S albumins, represent major seed storage protein constituents of the nuts. The allergenic tree nuts discussed in this review include those most commonly responsible for allergic reactions such as hazelnut, walnut, cashew, and almond as well as those less frequently associated with allergies including pecan, chestnut, Brazil nut, pine nut, macadamia nut, pistachio, coconut, Nangai nut, and acorn.

Recombinant lipid transfer protein Cor a 8 from hazelnut: a new tool for in vitro diagnosis of potentially severe hazelnut allergy

BACKGROUND

Cor a 1.04 has been identified as the major hazelnut allergen in 65 European patients with positive double-blind, placebo-controlled food challenge results to hazelnut. Recently, the 11S globulin Cor a 9 was shown to be a pollen-independent hazelnut allergen in the United States, whereas preliminary data suggest the lipid transfer protein (LTP) as an important birch pollen-unrelated hazelnut allergen in Europe.

OBJECTIVE

We sought to recruit a group of European patients allergic to hazelnut without birch pollen allergy and to identify and clone the major food allergen(s) in this study population.

METHODS

We recruited 26 such Spanish patients, including 10 patients with anaphylaxis. IgE immunoblotting was performed with hazelnut extract. Hazelnut LTP Cor a 8 was cloned by using a PCR strategy, purified, and subjected to IgE immunoblotting. Recombinant Cor a 8, rCor a 1.0401, and rCor a 2 (profilin) were further investigated by means of enzyme allergosorbent test. Immunoblot inhibition experiments were used to compare the immunologic properties of natural and recombinant LTP.

RESULTS

A 9-kd major allergen was identified in hazelnut extract. Cloning, sequencing, heterologous expression, and inhibition experiments identified it as an LTP. The prevalence of specific IgE antibody reactivity to LTP was 62% in hazelnut extract and 77% when recombinant LTP was tested by means of immunoblotting. IgE immunoblot inhibition with hazelnut extract showed that natural Cor a 8 and rCor a 8 shared identical epitopes. Only one patient had positive reactivity to Cor a 1.04, and no patients had positive reactivity to Cor a 2. Two sera bound to high-molecular-weight allergens. The LTP was denominated as Cor a 8 and submitted to the allergen database of the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Subcommittee.

CONCLUSIONS

Cor a 8 is a relevant allergen for a majority of Spanish patients with hazelnut allergy that can cause severe allergic reactions.

Antiulcer drugs promote oral sensitization and hypersensitivity to hazelnut allergens in BALB/c mice and humans

BACKGROUND

Hazelnut allergy can be a consequence of sensitization to cross-reactive pollen, especially from the Fagales family. However, severe allergic reactions after ingestion of hazelnuts without associated pollen allergy have been reported. In these cases, oral sensitization by hazelnut ingestion is plausible.

OBJECTIVE

We have reported that antiulcer drugs promote oral sensitization to digestion-labile food allergens. Because hazelnut proteins were sensitive to gastric digestion in our in vitro assay, we aimed to analyze the effect of antiulcer treatment on oral sensitization to hazelnut proteins.

DESIGN

BALB/c mice were fed hazelnut extract with or without antiulcer drugs. In parallel, gastroenterologic patients (n = 153) were screened during antiulcer treatment for specific immunoglobulin (Ig) E to hazelnut and inhalative allergens in vitro and in vivo.

RESULTS

Mice fed hazelnut extract in combination with antiulcer drugs formed anaphylactogenic IgG1 toward hazelnut and developed type I skin reactivity to hazelnut extract. In the human study population, 5 of 153 (3.3%) patients developed hazelnut-specific IgE, 4 of 5 developed specific skin reactivity, 3 of 5 had a positive result to oral provocation, and 2 of 5 manifested a food allergy to hazelnut after a 3-mo course of antiulcer treatment. Immunoblot testing with recombinant allergens showed that hazelnut, but not Fagales pollen, was the genuine elicitor in mice and humans.

CONCLUSION

Our experimental and epidemiologic data suggest that the intake of antiulcer drugs may lead to the induction of immediate-type food hypersensitivity toward hazelnut.

Immunological analysis of allergenic cross-reactivity between peanut and tree nuts

BACKGROUND

Peanut and tree nut allergy is characterized by a high frequency of life-threatening anaphylactic reactions and typically lifelong persistence. Peanut allergy is more common than tree nut allergy, but many subjects develop hypersensitivity to both peanuts and tree nuts. Whether this is due to the presence of cross-reactive allergens remains unknown.

OBJECTIVE

The aim of this study was to investigate the presence of allergenic cross-reactivity between peanut and tree nuts.

METHODS

Western blotting and ELISA were performed using sera from subjects with or without peanut and tree nut allergy to assess immunoglobulin E (IgE) reactivity to peanut and tree nut extracts. Inhibition ELISA studies were conducted to assess the presence of allergenic cross-reactivity between peanut and tree nuts.

RESULTS

Western blot and ELISA results showed IgE reactivity to peanut, almond, Brazil nut, hazelnut and cashew nut for peanut- and tree nut-allergic subject sera. Raw and roasted peanut and tree nut extracts showed similar IgE reactivities. Inhibition ELISA showed that pre-incubation of sera with almond, Brazil nut or hazelnut extracts resulted in a decrease in IgE binding to peanut extract, indicating allergenic cross-reactivity. Pre-incubation of sera with cashew nut extract did not cause any inhibition.

CONCLUSION

These results show that multiple peanut and tree nut sensitivities observed in allergic subjects may be due to cross-reactive B cell epitopes present in different peanut and tree nut allergens. The plant taxonomic classification of peanut and tree nuts does not appear to predict allergenic cross-reactivity.

Ana o 2, a Major Cashew (Anacardium occidentale L.) Nut Allergen of the Legumin Family

BACKGROUND

We recently cloned and described a vicilin and showed it to be a major cashew allergen. Additional IgE-reactive cashew peptides of the legumin group and 2S albumin families have also been reported. Here, we attempt to clone, express and characterize a second major cashew allergen.

METHODS

A cashew cDNA library was screened with human IgE and rabbit IgG anti-cashew extract antisera, and a reactive nonvicilin clone was sequenced and expressed as a fusion protein in Escherichia coli. Immunoblotting was used to screen for reactivity with patients' sera, and inhibition of immunoblotting was used to identify the corresponding native peptides in cashew nut extract. The identified allergen was subjected to linear epitope mapping using SPOTs solid-phase synthetic peptide technology.

RESULTS

Sequence analysis showed the selected clone, designated Ana o 2, to encode for a member of the legumin family (an 11S globulin) of seed storage proteins. By IgE immunoblotting, 13 of 21 sera (62%) from cashew-allergic patients were reactive. Immunoblot inhibition data showed that the native Ana o 2 constitutes a major band at approximately 33 kD and a minor band at approximately 53 kD. Probing of overlapping synthetic peptides with pooled human cashew-allergic sera identified 22 reactive peptides, 7 of which gave strong signals. Several Ana o 2 epitopes were shown to overlap those of the peanut legumin group allergen, Ara h 3, in position but with little sequence similarity. Greater positional overlap and identity was observed between Ana o 2 and soybean glycinin epitopes.

CONCLUSIONS

We conclude that this legumin-like protein is a major allergen in cashew nut.

Comparison of four variants of a major allergen in hazelnut (Corylus avellana) Cor a 1.04 with the major hazel pollen allergen Cor a 1.01

The aim of this study was to produce the Bet v 1-related major hazelnut allergen Cor a 1.0401 and variants thereof as recombinant allergens, and to compare their immuno-reactivity with the major hazel pollen allergen using sera of patients whose hazelnut allergy recently was confirmed by double-blind placebo-controlled food challenges (DBPCFC) in a multicenter study. Total RNA was isolated from immature hazelnuts and transcribed into cDNA. Full length coding DNA obtained by PCR-strategy was subcloned into pTYB11 vector and expressed in E. coli ER2566 cells. Native non-fusion target proteins were purified by DTT-induced self-cleavage of the intein-tagged N-terminal fusion proteins. IgE reactivity of the recombinant allergens was tested by enzyme allergosorbent test (EAST), EAST-inhibition, immunoblot-inhibition and histamine release assays. Four recombinant allergens were produced showing deduced amino acid sequence identities among each other of 97-99%, and were considered as variants Cor a 1.0401 (GenBank Accession no.: AF136945), Cor a 1.0402 (AF323973), Cor a 1.0403 (AF323974) and Cor a 1.0404 (AF323975). Cor a 1.0402 and 03 only differed in a C4S exchange. Cor a 1.0404 had a unique proline residue in position 99. Surprisingly, only 63% identity was revealed with hazel pollen Cor a 1. EAST with 43 sera of patients with positive DBPCFC to hazelnut indicated IgE reactivity to Cor a 1.0401 in 95% of the sera, to Cor a 1.0402 in 93%, to Cor a 1.0403 in 91%, and in only 74% of the sera to the proline variant Cor a 1.0404. The allergenic activity of the four variants was confirmed by histamine release assays in 15 hazelnut-allergic patients stimulated with the four variants and controls. Eleven sera were positive with extract from native hazelnut, 13 with rCor a 1.0401, 12 with rCor a 1.0402, 11 with rCor a 1.0403, and only two with rCor a 1.0404 containing the proline exchange. The high IgE binding variant Cor a 1.0401 showed only partial IgE cross-reactivity with pollen Cor a 1. IgE-binding and histamine release capacity led to a concordant ranking of the allergenic activity of the recombinant variants: Cor a 1.0401>Cor a 1.0402 and 03>Cor a 1.0404 (the proline variant). Similar results for Cor a 1.0402 and 03 suggest a minor influence in IgE binding of cysteine in position 4, whereas proline in position 99 appears to be responsible for the decrease in IgE reactivity in Cor a 1.0404. It appears that the epitopes of hazelnut Cor a 1.04 are less related to pollen Cor a 1 than to Bet v 1 from birch pollen. Low IgE binding variants or mutants of Cor a 1.04 are candidate compounds for developing a novel and safe approach of specific immunotherapy of hazelnut allergy.

Peanut and hazelnut traces in cookies and chocolates: Relationship between analytical results and declaration of food allergens on product labels

Accidental exposure to hazelnut or peanut constitutes a real threat to the health of allergic consumers. Correct information regarding food product ingredients is of paramount importance for the consumer, thereby reducing exposure to food allergens. In this study, 569 cookies and chocolates on the European market were purchased. All products were analysed to determine peanut and hazelnut content, allowing a comparison of the analytical results with information provided on the product label. Compared to cookies, chocolates are more likely to contain undeclared allergens, while, in both food categories, hazelnut traces were detected at higher frequencies than peanut. The presence of a precautionary label was found to be related to a higher frequency of positive test results. The majority of chocolates carrying a precautionary label tested positive for hazelnut, whereas peanut traces were not be detected in 75% of the cookies carrying a precautionary label.

Efficacy of a management plan based on severity assessment in longitudinal and case-controlled studies of 747 children with nut allergy: proposal for good practice

BACKGROUND

There are few data on the long-term management of children with peanut/nut allergy. Advice is variable and often inadequate; further reactions are common. There is no consensus on the criteria for prescription of rescue medication, particularly adrenaline.

METHOD

A longitudinal prospective and case-control study in a tertiary allergy clinic. Patients/parents/school staff of 747 children with confirmed peanut or tree nut allergy received detailed verbal and written advice on nut avoidance, training in recognition and (self-) treatment of reactions and a written treatment plan. The severity of nut allergy was graded (mild-severe) and emergency medication was allocated according to our criteria: all received oral antihistamines, injected adrenaline (EpiPen) was given to those with reactions with airway narrowing, milder reactions to low-dose exposure or concomitant asthma. At annual follow-up over 25 906 patient-months (median: 39 months) retraining was given and details of further reactions (frequency, severity and treatment) were obtained. Criteria for allocation of EpiPen were evaluated.

RESULTS

The worst reaction pre-enrolment was mild in 64% and moderate/severe in 36% (airway narrowing). Of 615 subjects followed up, 21% had a further reaction (eightfold reduction in frequency), mostly mild. There was a 60-fold reduction in the frequency of severe reactions. Of those with a moderate-severe initial reaction, 99.5% had no or a less severe follow-up reaction. No child with a mild or severe index reaction had a severe follow-up reaction. Only 1/615 (0.2%) had a severe follow-up reaction and only 2/615 (0.3%) used adrenaline, both successfully and had it available according to our criteria. Of mild-moderate reactions, 77% required oral antihistamines alone and 15% no treatment. Children who had follow-up reactions had more frequent and severe reactions pre-enrolment.

CONCLUSION

The management plan greatly reduced the frequency and severity of further reactions and was successful for all children. Our criteria for selective prescription of EpiPen in the context of this management plan were appropriate. This is the first study to provide evidence on which to inform practice.

Risk assessment and food allergy: the probabilistic model applied to allergens

In order to assess the risk of unintended exposure to food allergens, traditional deterministic risk assessment is usually applied, leading to inconsequential conclusions as 'an allergic reaction cannot be excluded'. TNO therefore developed a quantitative risk assessment model for allergens based on probabilistic techniques resulting in a more exhaustive risk assessment and more detailed information. By now, this approach is recognized as the future approach in allergen risk assessment. A case study (hazelnut proteins in chocolate spread) is presented as a proof of concept.

Cashew nut causes more severe reactions than peanut: case-matched comparison in 141 children

BACKGROUND

Cashew nut allergy is becoming common, but the risk of severe reactions in comparison with peanut allergy is unknown.

METHOD

A case-matching study of children with a recent history of a reaction after definite nut ingestion, with positive skin prick test. Children whose worst ever reaction was to cashew nut (cashew group), were matched with two children each whose worst ever reaction was to peanut (peanut group) for sex, age of reaction and presentation, amount ingested, and asthma. Severity of the worst clinical reactions to date was compared.

RESULTS

A total of 47 children in the cashew group were matched to 94 in the peanut group. There were no differences in clinical features between groups for matching criteria, except asthma (more prevalent in the peanut group). Wheezing and cardiovascular symptoms were reported more frequently during reactions in the cashew compared with the peanut group: odds ratios (OR) 8.4 (95% CI: 3.2-22.0) and 13.6 (95% CI: 5.6-32.8), respectively. The cashew group received intramuscular adrenaline more frequently: OR 13.3 (95% CI: 5.5-32.2). Overall, the OR for a severe reaction (severe dyspnoea and/or collapse) in the cashew group was 25.1 (95% CI: 3.1-203.5).

CONCLUSIONS

Previous studies show cashew nut can cause severe reactions; this is the first study to show by case-matching that severe clinical reactions occur more frequently in cashew compared with peanut allergy. The nut type which caused the worst reaction to date should be considered when providing emergency medication.

The development and progression of allergy to multiple nuts at different ages

The aims of this study were to define the development of sensitization and clinical allergy to multiple nut types by age, and to identify associations. This observational cross- sectional study was carried out in a tertiary level allergy clinic. Seven hundred and eighty four nut-allergic children, prospectively enrolled on first attendance with history of a type-1 allergic reaction shortly after definite nut ingestion with evidence of sensitization (presence of nut-specific IgE) by skin prick test (SPT) to peanut, Brazil, almond, hazel and walnut (positive > or = 3 mm). Details of exposure (tolerance or allergy) to each nut were obtained. The main outcome measures were mono or multi-sensitization (specific IgE to one or more than one nut type, demonstrated by SPT); mono or multi-allergy (clinical allergy to one or more than one nut type). By 2 yr of age at least 19% were multi-sensitized, and 2% multi-allergic. Increasing proportions were exposed to multiple nut types with increasing age (23% at 2 yr to 73% by 10 yr) and greater proportions were multi-sensitized (19% at 2 yr to 86% at 5-14 yr) and multi-allergic (2% at 2 yr to 47% at 14 yr). This study is the first to define the natural history of multiple nut allergies in childhood. New findings are that a large proportion of those aged 0-1 yr with nut allergy are already sensitized (have specific IgE) to multiple nut types, implying in utero or early life sensitization; those who present later in childhood are increasingly likely to be sensitized and clinically allergic to multiple nuts. This is related to increased duration of allergy and exposure to multiple nut types with age. Children with nut allergy should avoid all nut types from the onset.

Cross-reactivity among edible nuts: double immunodiffusion, crossed immunoelectrophoresis, and human specific igE serologic surveys

BACKGROUND

As many as one third of all food allergen anaphylactic events are related to tree nut ingestion. Although concurrent allergen sensitivity to tree nuts is common, cross-reactivity among nut antigens is less well defined.

OBJECTIVE

To survey serologic cross-reactivities among 7 tree nuts (walnut, pecan, hazelnut, cashew, Brazil nut, pistachio, and almond) and peanut.

METHODS

Human specific IgE enzyme-linked immunosorbent assay inhibition was used to identify nut allergen cross-reactivities. Single-nut rabbit antisera were used in double immunodiffusion, crossed-line immunoelectrophoresis, and crossed immunoelectrophoresis with intermediate gel studies of nut antigen cross-reactivity.

RESULTS

Nut specific IgE enzyme-linked immunosorbent assay inhibition demonstrated no cross-reactivities between peanut and tree nuts. Among tree nuts, 2 groups with allergen cross-reactivity were defined: (1) walnut, pecan, and hazelnut and (2) hazelnut, cashew, Brazil nut, pistachio, and almond. Double immunodiffusion, crossed-line immunoelectrophoresis, and crossed immunoelectrophoresis with intermediate gel results supported the same groupings of cross-reactive tree nuts and identified several less prominent nut-nut antigen cross-reactivities between groups and with peanut.

CONCLUSION

With few exceptions (notably limited peanut cross-reactivity with pistachio and walnut), peanut antigens did not serologically cross-react with tree nuts. Walnut, pecan, and hazelnut form a group of strongly cross-reactive tree nuts. Hazelnut, cashew, Brazil nut, pistachio, and almond form a group of moderately cross-reactive tree nuts. Cross-reactivities between these groups are less pronounced (notably limited cross-reactivity of walnut and pecan with Brazil nut). The strongest cross-reactivities among tree nuts follow botanical family associations: (1) walnut and pecan in the family Juglandaceae and (2) cashew and pistachio in the family Anacardiaceae.

Almond allergens: molecular characterization, detection, and clinical relevance

Almond ( Prunus dulcis ) has been widely used in all sorts of food products (bakery, pastry, snacks), mostly due to its pleasant flavor and health benefits. However, it is also classified as a potential allergenic seed known to be responsible for triggering several mild to life-threatening immune reactions in sensitized and allergic individuals. Presently, eight groups of allergenic proteins have been identified and characterized in almond, namely, PR-10 (Pru du 1), TLP (Pru du 2), prolamins (Pru du 2S albumin, Pru du 3), profilins (Pru du 4), 60sRP (Pru du 5), and cupin (Pru du 6, Pru du γ-conglutin), although only a few of them have been tested for reactivity with almond-allergic sera. To protect sensitized individuals, labeling regulations have been implemented for foods containing potential allergenic ingredients, impelling the development of adequate analytical methods. This work aims to present an updated and critical overview of the molecular characterization and clinical relevance of almond allergens, as well as review the main methodologies used to detect and quantitate food allergens with special emphasis on almond.

IgE cross-reactivity between the major peanut allergen Ara h 2 and tree nut allergens

Allergy to peanut and tree nuts is characterised by a high frequency of life-threatening anaphylactic reactions and typically lifelong persistence. Although peanut is the most common cause of nut allergy, peanut allergic patients are frequently also sensitive to tree nuts. It is not known if this is due to cross-reactivity between peanut and tree nut allergens. In this study, the major peanut allergen Ara h 2 was cloned from peanut cDNA, expressed in E. coli cells as a His-tag fusion protein and purified using a Ni-NTA column. Immunoblotting, ELISA and basophil activation indicated by CD63 expression all confirmed the IgE reactivity and biological activity of rAra h 2. To determine whether or not this allergen plays a role in IgE cross-reactivity between peanut and tree nuts, inhibition ELISA was performed. Pre-incubation of serum from peanut allergic patients with increasing concentrations of almond or Brazil nut extract inhibited IgE binding to rAra h 2. Purified rAra h 2-specific serum IgE antibodies also bound to proteins present in almond and Brazil nut extracts by immunoblotting. This indicates that the major peanut allergen, Ara h 2, shares common IgE-binding epitopes with almond and Brazil nut allergens, which may contribute to the high incidence of tree nut sensitisation in peanut allergic individuals.

Cashew nut allergy is associated with a high risk of anaphylaxis

Cashew allergy is an evolving clinical problem. A retrospective chart review of 213 children with peanut or tree nut allergy was undertaken over a 42 month period. Anaphylaxis to cashew nut was more common than to peanut (74.1% v 30.5%). Children with cashew allergy are at risk of anaphylaxis.

The natural history of peanut and tree nut allergy

Peanut and tree nut allergies were once thought to be permanent. Recent studies have shown that about 20% and 10%, respectively, of young patients may outgrow peanut and tree nut allergies. For the majority of patients, however, the natural history is not favorable. In addition, approximately 8% of patients who outgrow peanut allergy may suffer a recurrence. The rising prevalence of these allergies, coupled with the knowledge that allergic reactions to these foods have the potential to be severe or fatal and that accidental exposures are common, makes developing effective treatments to alter the natural history of peanut and tree nut allergies even more crucial for those who will not outgrow them. At this time, avoidance of the offending foods and being prepared to treat a potential reaction after accidental ingestion is the only treatment, but many promising therapeutic interventions are being investigated.

How Accurate and Safe Is the Diagnosis of Hazelnut Allergy by Means of Commercial Skin Prick Test Reagents?

BACKGROUND

Allergy to tree nuts, like hazelnuts, ranks among the most frequently observed food allergies. These allergies can start at early childhood and are, in contrast to other food allergies, not always outgrown by the patient. Tree nut allergy is frequently associated with severe reactions. Diagnosis partially relies on in vivo testing by means of a skin prick test (SPT) using commercially available SPT reagents.

METHODS

Protein and allergen composition of nine commercial SPT solutions was evaluated using standard protein detection methods and specific immunoassays for measurement of five individual allergens. Diagnostic performance was assessed by SPT in 30 hazelnut-allergic subjects, of which 15 were provocation proven.

RESULTS

Protein concentrations ranged from 0.2-14 mg/ml. SDS-PAGE/silver staining revealed clear differences in protein composition. The major allergen Cor a 1 was present in all extracts but concentrations differed up to a factor 50. An allergen associated with severe symptoms, Cor a 8 (lipid transfer protein), was not detected on immunoblot in three products, and concentrations varied by more than a factor 100 as was shown by RAST inhibition. Similar observations were made for profilin, thaumatin-like protein and a not fully characterized 38-kD allergen. Ratios of individual allergens were variable among the nine extracts. SPT showed significant difference, and 6/30 patients displayed false-negative results using 3/9 products.

CONCLUSION

Variability in the composition of products for the diagnosis of hazelnut allergy is extreme. Sometimes, allergens implicated in severe anaphylaxis are not detected by immunoblotting. These shortcomings in standardisation and quality control can potentially cause a false-negative diagnosis in subjects at risk of severe reactions to hazelnuts.

The atopic dog as a model of peanut and tree nut food allergy

BACKGROUND

Animal models are needed that mimic human IgE-mediated peanut and tree nut allergy. Atopic dogs have been previously used in a model of food allergy to cow's milk, beef, wheat, and soy, with the demonstration of specific IgE production and positive oral challenges similar to those seen in human subjects.

OBJECTIVE

We sought to sensitize dogs to peanut, walnut, and Brazil nut and to assess whether sensitization is accompanied by clinical reactions and whether there is cross-reactivity among the different preparations.

METHODS

Eleven dogs were sensitized subcutaneously by using an established protocol with 1 microg each of peanut, English walnut, or Brazil nut protein extracts in alum first at birth and then after modified live virus vaccinations at 3, 7, and 11 weeks of age. The dogs were sensitized to other allergens, including soy and either wheat or barley. Intradermal skin tests, IgE immunoblotting to nut proteins, and oral challenges were performed with ground nut preparations.

RESULTS

At 6 months of age, the dogs' intradermal skin test responses were positive to the nut extracts. IgE immunoblotting to peanut, walnut, and Brazil nut showed strong recognition of proteins in the aqueous preparations. Each of the 4 peanut- and the 3 Brazil nut-sensitized dogs and 3 of the 4 walnut-sensitized dogs reacted on oral challenge with the corresponding primary immunogen at age 2 years. None of the peanut-sensitized dogs reacted clinically with walnut or Brazil nut challenges. One of the walnut-sensitized dogs had delayed (overnight) vomiting to Brazil nut.

CONCLUSIONS

On the basis of measurements of the mean amount of allergen eliciting a skin test response in dogs, the hierarchy of reactivity by skin testing is similar to the clinical experience in human subjects (peanut > tree nuts > wheat > soy > barley). Cross-reactivity, which was not apparent between soy and peanut or tree nuts or between peanut and tree nuts, was slight between walnut and Brazil nut. The results give further support to the dog as a model of human food allergy.

Passive transfer of nut allergy after liver transplantation

An anaphylactic reaction to cashew nut developed in a nonatopic 60-year-old man 25 days after receiving a liver allograft from a 15-year-old atopic boy who died of anaphylaxis after peanut ingestion. The liver recipient had no history of nut allergy. Posttransplantation skin prick test results were positive for peanut, cashew nut, and sesame seed, and the donor had allergen-specific IgE antibodies to the same 3 allergens. Contact tracing of the recipients of other solid organs from the same donor disclosed no other development of allergic symptoms after ingestion of peanut or cashew nut. Results of molecular HLA typing did not detect any donor-origin leukocytes in the recipient after transplantation, which excluded peripheral microchimerism. The patient inadvertently ingested peanut-contaminated food and suffered a second anaphylactic reaction 32 weeks after the transplantation. This case illustrates that transfer of IgE-mediated hypersensitivity can occur after liver transplantation and have potentially serious consequences. We therefore recommend that organ donors undergo screening for allergies, and that recipients be advised regarding allergen avoidance.

Homology modelling and conformational analysis of IgE-binding epitopes of Ara h 3 and other legumin allergens with a cupin fold from tree nuts

Linear IgE-binding epitopes identified in legumin allergens of peanut (Ara h 3) and other allergenic tree nuts (Jug r 4 of walnut, Cor a 9 of hazelnut, Ana o 2 cashew nut) were mapped on three-dimensional models of the proteins built up by homology modelling. A conformational analysis revealed that consensual surface-exposed IgE-binding epitopes exhibited some structural homology susceptible to account for the IgE-binding cross-reactivity observed among peanut and tree nut allergens. This structurally related cross-reactivity seems irrespective of the botanical origin of the allergens and thus demands that persons allergic to peanut avoid other three nuts to prevent possible allergic reactions. IgE-binding epitopes similar to those found in 11S globulin allergens do not apparently occur in other vicilin allergens with the cupin fold from peanut (Ara h 1) or tree nuts (Jug r 2 of walnut, Cor a 1 of hazel nut, Ana o 3 of cashew nut).

Effects of processing on immunoreactivity of cashew nut (Anacardium occidentale L.) seed flour proteins

Cashew nut seeds were subjected to processing including autoclaving (121 degrees C for 5, 10, 20, and 30 min), blanching (100 degrees C for 1, 4, 7, and 10 min), microwave heating (1 and 2 min each at 500 and 1000 W), dry roasting (140 degrees C for 20 and 30 min; 170 degrees C for 15 and 20 min; and 200 degrees C for 10 and 15 min), gamma-irradiation (1, 5, 10, and 25 kGy), and pH (1, 3, 5, 7, 9, 11, and 13). Proteins from unprocessed and processed cashew nut seeds were probed for stability using anti-Ana o 2 rabbit polyclonal antibodies and mouse monoclonal antibodies directed against Ana o 1, Ana o 2, and Ana o 3 as detection agents. Results indicate that Ana o 1, Ana o 2, and Ana o 3 are stable regardless of the processing method to which the nut seeds are subjected.