Walnut antigens can trigger autoantibody development in patients with pemphigus vulgaris through a "hit-and-run" mechanism

BACKGROUND

Environmental factors, as well as genetic predisposition, are known to be critical for the development of autoimmunity. However, the environmental agents that trigger autoimmune responses have remained elusive. One possible explanation is the "hit-and-run" mechanism in which the inciting antigens that initiate autoimmune responses are not present at the time of overt autoimmune disease.

OBJECTIVE

After our previous findings that some allergens can incite autoimmune responses, we investigated the potential role of environmental allergens in triggering autoantibody development in patients with an autoimmune skin disease, pemphigus vulgaris (PV).

METHODS

Revertant/germline mAbs (with mutations on variable regions of heavy and light chains reverted to germline forms) of 8 anti-desmoglein (Dsg) 3 pathogenic mAbs from patients with PV were tested for reactivity against a panel of possible allergens, including insects, pollens, epithelia, fungi, and food antigens.

RESULTS

All the PV germline mAbs were reactive to antigens from walnut, including the well-known allergen Jug r 2 and an uncharacterized 85-kDa protein component. Sera from patients with PV contained significantly greater levels of anti-Dsg3 autoantibodies than walnut-specific antibodies, suggesting that the autoreactive B-cell response in patients with PV might be initially triggered by walnut antigens but is subsequently driven by Dsg3.

CONCLUSION

Our findings suggest that walnut antigens/allergens can initiate autoantibody development in patients with PV through a "hit-and-run" mechanism. The revertant/germline mAb approach might provide a paradigm for the etiological study of other allergic and autoimmune diseases.

Effects of thermal treatment on walnut detection and allergenicity

BACKGROUND

Peanuts and tree nut allergies pose an increasing food safety problem. The aim of our study was to test the accuracy of different commercial enzyme-linked immunosorbent assay (ELISA) kits in the detection of the presence of walnuts in untreated and heat exposed food samples. The effects of thermal treatment of samples were evaluated by exposing walnuts to different heat treatments. All samples were first analysed by two different commercial ELISA assays. Then, we performed a skin prick test (SPT) on nine patients with proven nut allergy using small walnut pieces from raw and treated samples.

RESULTS

The presence of nuts proteins in thermally processed foods was not accurately detected by ELISA kits. All patients had a positive SPT reaction with raw walnut, while thermal treatments affected walnut allergenicity. The ELISA test gives a negative result in the case of strong thermal treatment, but at the same time allergic subjects react positively to stimulation with the same sample.

CONCLUSION

This study suggests that commercial ELISA kits may not be able to accurately determine the amount of proteins present in thermally processed foods due to changes in the solubility and immunoreactivity of the target proteins. Finally, the clinical results highlight that thermal treatment might induce a reduction in walnut allergenicity. © 2018 Society of Chemical Industry.

First Extensive Microscopic Study of Butternut Defense Mechanisms Following Inoculation with the Canker Pathogen Ophiognomonia clavigignenti-juglandacearum Reveals Compartmentalization of Tissue Damage

Ophiognomonia clavigignenti-juglandacearum endangers the survival of butternut (Juglans cinerea) throughout its native range. While screening for disease resistance, we found that artificial inoculations of 48 butternut seedlings with O. clavigignenti-juglandacearum induced the expression of external symptoms, but only after a period of dormancy. Before dormancy, compartmentalized tissues such as necrophylactic periderms (NPs) and xylem reaction zones (RZs) contributed to limiting pathogen invasion. Phenols were regularly detected in RZs, often in continuity with NPs during wound closure, and confocal microscopy revealed their presence in parenchyma cells, vessel plugs and cell walls. Vessels were blocked with tyloses and gels, particularly those present in RZs. Suberin was also detected in cells formed over the affected xylem by the callus at the inoculation point, in a few tylosis walls, and in longitudinal tubes that formed near NPs. Following dormancy, in all inoculated seedlings but one, defensive barriers were breached by O. clavigignenti-juglandacearum and then additional ones were produced in response to this new invasion. The results of this histopathological study indicate that trees inoculated in selection programs to test butternut canker resistance should go through at least one period of dormancy and that asymptomatic individuals should be dissected to better assess how they defend themselves against O. clavigignenti-juglandacearum.

Purification and Characterization of a Black Walnut (Juglans nigra) Allergen, Jug n 4

Tree nuts as a group cause a significant number of fatal anaphylactic reactions to foods. Walnuts (Juglans spp.) are one of the leading causes of allergic reactions to tree nuts in the U.S. and Japan. The purpose of this study was to purify and characterize potential food allergens from black walnut. Here, we report the isolation of the black walnuts allergen Jug n 4 (an 11S globulin) by ammonium sulfate precipitation, hydrophobic interaction, and size exclusion chromatography. Reducing SDS-PAGE analysis indicated that purified Jug n 4 consists of three major bands. N-Terminal sequencing data of these bands indicated that they were the results of a post-transcriptional protease cleavage of the mature protein at a site that consists of a known conserved protease recognition motif, NGXEET. Western blot experiments revealed that 32% of the sera from 25 patients with double-blind, placebo-controlled clinical walnut allergy contained IgE antibodies that recognized Jug n 4, indicating that it is a walnut allergen. Identifying this and additional allergens may facilitate the understanding of the allergenicity of seed storage proteins in tree nuts and their cross-reactivity.

IgE cross-reactivity of peanut with walnut and soybean in children with food allergy

BACKGROUND

Peanut allergies are common and can be life-threating for sensitised individuals. Peanut allergens share significant amino acid homology with those of other legumes and tree nuts, but their cross-reactivity still remains unclear.

OBJECTIVE

We sought to determine the clinical significance of the cross-reactivity of peanut allergens with those of walnut and soybean.

METHODS

Pooled sera from eight subjects with both peanut and walnut specific IgE were investigated in an inhibition test. After the sera were incubated with either peanut or walnut protein extracts, the quantity of IgE antibodies against the peanut and walnut was measured using an immunoCAP test. Likewise, pooled sera from 18 subjects with both peanut and soybean specific IgE antibodies were incubated with either peanut or soybean protein extracts and evaluated with a peanut and soybean immunoCAP test. SDS-PAGE and immunoblotting were also performed with peanut, walnut and soybean protein extracts and relevant sera.

RESULTS

Peanut specific IgE was inhibited up to 20% and 26% by walnut and soybean protein extracts, respectively. In reverse, walnut and soybean specific IgE were inhibited up to 21% and 23% by peanut protein extracts, respectively. In the immunoblot analysis, pooled serum from the subjects with peanut specific IgE antibodies reacted with walnut protein extracts significantly.

CONCLUSION

Although the clinical significance of the cross-reactivity of peanut specific IgE with walnut and soybean protein extracts has not been established, we believe that individuals who are allergic to peanuts need to be cautious about consuming walnuts and soybeans.

Is Microarray Analysis Really Useful and Sufficient to Diagnose Nut Allergy in the Mediterranean Area?

BACKGROUND

Component-based diagnosis on multiplex platforms is widely used in food allergy but its clinical performance has not been evaluated in nut allergy.

OBJECTIVE

To assess the diagnostic performance of a commercial protein microarray in the determination of specific IgE (sIgE) in peanut, hazelnut, and walnut allergy.

METHODS

sIgE was measured in 36 peanut-allergic, 36 hazelnut-allergic, and 44 walnut-allergic patients by ISAC 112, and subsequently, sIgE against available components was determined by ImmunoCAP in patients with negative ISAC results. ImmunoCAP was also used to measure sIgE to Ara h 9, Cora 8, and Jug r 3 in a subgroup of lipid transfer protein (LTP)-sensitized nut-allergic patients (positive skin prick test to LTP-enriched extract). sIgE levels by ImmunoCAP were compared with ISAC ranges.

RESULTS

Most peanut-, hazelnut-, and walnut-allergic patients were sensitized to the corresponding nut LTP (Ara h 9, 66.7%; Cor a 8, 80.5%; Jug r 3, 84% respectively). However, ISAC did not detect sIgE in 33.3% of peanut-allergic patients, 13.9% of hazelnut-allergic patients, or 13.6% of walnut-allergic patients. sIgE determination by ImmunoCAP detected sensitization to Ara h 9, Cor a 8, and Jug r 3 in, respectively, 61.5% of peanut-allergic patients, 60% of hazelnut-allergic patients, and 88.3% of walnut-allergic patients with negative ISAC results. In the subgroup of peach LTP-sensitized patients, Ara h 9 sIgE was detected in more cases by ImmunoCAP than by ISAC (94.4% vs 72.2%, P < .05). Similar rates of Cora 8 and Jug r 3 sensitization were detected by both techniques.

CONCLUSIONS

The diagnostic performance of ISAC was adequate for hazelnut and walnut allergy but not for peanut allergy. sIgE sensitivity against Ara h 9 in ISAC needs to be improved.

Demographic Assessment of Plant Cultivar Resistance to Insect Pests: A Case Study of the Dusky-Veined Walnut Aphid (Hemiptera: Callaphididae) on Five Walnut Cultivars

To provide a comprehensive evaluation of walnut cultivar resistance to the dusky-veined walnut aphid, Panaphis juglandis (Goeze), we collected the life table data of this aphid reared on five cultivars of walnut ('Akça I,' 'Chandler,' 'Fernette,' 'Fernor,' and 'Pedro') under field conditions. The raw data of the developmental time, survival rate, and fecundity was analyzed using the age-stage, two-sex life table to account for the variable developmental rate and stage differentiation among individuals. Due to the species' longer immature developmental time, shorter adult longevity, shorter reproduction period, and lower fecundity, the net reproduction rate (R0=5.9 offspring), intrinsic rate of increase (r=0.0983 d(-1)), and finite rate (λ=1.1034 d(-1)) were the lowest when aphids were reared on the Fernor cultivar, while those reared on Akça I exhibited the highest population parameters (R0=18.0 offspring, r=0.2031 d(-1), and λ=1.2252 d(-1)). Based on the population characteristics, Fernor is a less favorable cultivar for the development and reproduction of P. juglandis. We also demonstrated the advantages of using bootstrapping for the analysis of standard errors of developmental time, longevity, fecundity, and other parameters as well. Our results indicated that demographic analysis of pest development, survival, and reproduction based on the age-stage, two-sex life table offers a comprehensive assessment of pest growth potential on different crop cultivars.

Characterization of low molecular weight allergens from English walnut (Juglans regia)

Although English walnut is a commonly allergenic tree nut, walnut allergens have been poorly characterized to date. The objective of this work was to characterize the natural, low molecular weight (LMW) allergens from walnut. A protocol was developed to purify LMW allergens (specifically 2S albumins) from English walnuts. In addition to 2S albumins, a series of peptides from the N-terminal region of the 7S seed storage globulin proprotein were also identified and characterized. These peptides comprised a four-cysteine motif (C-X-X-X-C-X10-12-C-X-X-X-C) repeated throughout the 7S N-terminal region. Upon IgE immunoblotting, 3/11 and 5/11 sera from walnut-allergic subjects showed IgE reactivity to the 7S N-terminal fragments and 2S albumin, respectively. The mature 7S protein and the newly described 7S N-terminal peptides represent two distinct types of allergens. Because the proteolytic processing of 7S globulins has not been elucidated in many edible plant species, similar protein fragments may be present in other nuts and seeds.

Isolated IgE reactivity to native walnut vicilin-like protein (nJug r 2) on ISAC™ microarray is due to cross-reactive carbohydrate epitopes

BACKGROUND

The last version of the microarray-based testing ImmunoCAP ISAC 112™ includes the native walnut (Junglans regia) molecules 2S albumin (nJug r 1), vicilin (nJug r 2) and lipid transfer protein (nJug r 3). In view of the many unexpected cases of isolated positivity to nJug r 2 occurring in daily practice, we evaluated the association of these reactivities with clinical symptoms, as well as the relationship between sIgE and nJug r 2 and cross-reactive carbohydrate determinants (CCDs).

METHODS

Sera from 320 consecutive allergic outpatients tested by ImmuoCAP ISAC™ 112 were considered. The medical records of all nJug r 2 positive patients were reviewed to assess clinical symptoms related to walnut allergy. A linear regression analysis was performed to evaluate the correlation between nJug r 2 and CCDs (nMUXF3) sIgE values, and a CAP inhibition assay was carried out to confirm the possible cross-reactivity between CCDs and nJug r 2.

RESULTS

Thirty-seven out of 320 sera tested (11.6%) were positive to nJug r 2. Among them three (8.1%) and eight (21.6%) scored positive for nJug r 1 and nJug r 3 as well, respectively. Twenty-seven (73%) sera showed isolated nJug r 2 positivity. Only nJug r 1 reactors had symptoms referred to walnut allergy. Twenty-five/37 nJug r 2-positive sera (67.6%) showed a simultaneous positivity to nMUXF3 and a significant correlation (p<0.0001) between the IgE levels to nJug r 2 and nMUXF3 (r²=0.787). After incubation with nMUXF3 a complete inhibition of sIgE reactivity to both nMUXF3 and nJug r 2 was shown.

CONCLUSIONS

The unexpected isolated sIgE reactivity to nJug r 2 found by ImmunoCAP ISAC™ 112 is frequently related to reactivity to cross-reactive carbohydrate epitopes and it is lacking clinical significance.

Heterogenity of IgE response to walnut and hazelnut in Italian allergic patients

BACKGROUND

The prevalence of IgE reactivity against genuine walnut and hazelnut allergens is poorly defined.

OBJECTIVE

The IgE response to walnut and hazelnut was investigated in Italian patients with primary allergy to these nuts.

METHODS

Sera from 36 patients allergic to hazelnut and/or walnut, not reactive to PR-10, profilin, and LTP, underwent immunoblot analysis with extracts of both nuts.

RESULTS

Most patients had a history of systemic symptoms following the ingestion of the offending food(s). Twelve patients were sensitized to both walnut and hazelnut, and 13 were sensitized to other nuts and seeds (cashew, peanut, sesame, pine nut, almond, Brazil nut, and pistachio). On walnut immunoblot, the 7 sera which scored positive showed much variability in their IgE profile. Two reacted uniquely at 10 kDa, and the others at 35 , 40, 45, 50, 67, and > 67 kDa. The profiles obtained under reducing and non-reducing conditions showed several differences. The 7 sera positive on hazelnut immunoblot under reducing conditions recognized sera at 10 kDa and at <10 kDa (n=1), 20 kDa (n=4), at about 22, 24, 30, 40, 43, 58, 60, and 90 kDa, and higher m.w. in other cases. Under non-reducing conditions IgE reactivity at 20, 28, 35, 40, 45, 60, 90, and 100 kDa, was detected. Only two sera scored positive under both conditions and showed an IgE profile that partly changed from one assay to another.

CONCLUSION

The current list of walnut and hazelnut allergens is far from being complete. Both reducing and non-reducing conditions are needed to detect IgE reactivity in individual patients.

Natural oils enhance IL-10 and IFN-γ production by human PBMCs cultured with Malassezia furfur

BACKGROUND

Malassezia furfur is a lipophilic yeast that causes skin disease.

OBJECTIVE

To evaluate the level of IL-10, IFN-γ and IL-12P70 in co-incubation of peripheral blood mononuclear cells (PBMCs) with M. furfur grown in the presence of some different types of natural oils.

METHODS

PBMCs were obtained from blood samples of normal volunteers. M. furfur was cultured in different culture media containing almond oil, fish oil, walnut oil, full-fat milk, and a fat-free medium; and the yeasts grown were harvested and used for co-incubation with PBMCs in vitro. The IFN-γ, IL-10, and IL-12P70 levels were measured at different time intervals using ELISA methods.

RESULTS

Generally, IFN-γ and IL-10 levels in the co-incubation of yeasts with walnut oil group (WOG) and fish oil group (FOG) were higher than those in the almond oil group (AOG) and full-fat milk group (FFMG). Although the IL-12P70 was higher in groups such as AOG, FOG, and WOG; the increase was not statistically significant.

CONCLUSION

The results demonstrated that the type of fat used by M. furfur in the culture media can influence the immune response and increasesIFN-γ and IL-10 levels in an early time point of the culture system.

Computationally predicted IgE epitopes of walnut allergens contribute to cross-reactivity with peanuts

BACKGROUND

Cross-reactivity between peanuts and tree nuts implies that similar immunoglobulin E (IgE) epitopes are present in their proteins.

OBJECTIVE

To determine whether walnut sequences similar to known peanut IgE-binding sequences, according to the property distance (PD) scale implemented in the Structural Database of Allergenic Proteins, react with IgE from sera of patients with allergy to walnut and/or peanut.

METHODS

  Patient sera were characterized by western blotting for IgE binding to nut protein extracts and to peptides from walnut and peanut allergens, similar to known peanut epitopes as defined by low PD values, synthesized on membranes. Competitive enzyme-linked immunosorbent assay (ELISA) was used to show that peanut and predicted walnut epitope sequences compete with purified Ara h 2 for binding to IgE in serum from a cross-reactive patient.

RESULTS

Sequences from the vicilin walnut allergen Jug r 2, which had low PD values to epitopes of the peanut allergen Ara h 2, a 2S albumin, bound to IgE in sera from five patients who reacted to either walnut or peanut or both. A walnut epitope recognized by sera from six patients mapped to a surface-exposed region on a model of the N-terminal pro-region of Jug r 2. This predicted walnut epitope competed for IgE binding to Ara h 2 in serum as well as the known IgE epitope from Ara h 2.

CONCLUSIONS

Sequences with low PD value (< 8.5) to known IgE epitopes could contribute to cross-reactivity between allergens. This further validates the PD scoring method for predicting cross-reactive epitopes in allergens.

Linear IgE-epitope mapping and comparative structural homology modeling of hazelnut and English walnut 11S globulins

Allergic reactions to walnuts and hazelnuts can be serious. The 11S globulins (legumins) have been identified as important allergens in these and other nuts and seeds. Here we identify the linear IgE-binding epitopes of walnut and hazelnut 11S globulins, and generate 3D 11S globulin models to map the locations of the epitopes for comparison to other allergenic homologues. Linear IgE-epitope mapping was performed by solid-phase overlapping 15-amino acid peptides probed with IgE from pooled allergic human sera. Several walnut (Jug r 4) and hazelnut (Cor a 9) 11S globulin peptides with reactivity to patient IgE were identified. Comparative alignment with cashew (Ana o 2), peanut (Ara h 3), and soybean G1 (Gly m 6.0101) and G2 (Gly m 6.0201) allergenic homologues revealed several shared allergenic 'hot spots'. Homology modeling was performed based on the atomic structure of the soybean glycinin. Surface map comparisons between the tree nut and peanut homologues revealed structural motifs that could be important for IgE elicitation and binding and show that, contrary to predictions, the reactive epitopes are widely distributed throughout the monomeric subunits, both internally and externally, including regions occluded by quaternary subunit association. These findings reveal structural features that may be important to allergenicity and cross-reactivity of this protein class.

Reliable enzyme-linked immunosorbent assay for the determination of walnut proteins in processed foods

Among food allergens of tree nuts, walnuts are a frequent cause of adverse food reactions in allergic patients. A novel sandwich enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of walnut soluble proteins in processed foods was developed. The sandwich ELISA is highly specific for walnut soluble proteins. The recovery ranged from 83.4 to 123%, whereas the intra- and interassay coefficients of variation were less than 8.8 and 7.2%, respectively. This study showed that the proposed method is a reliable tool for detection in the presence of hidden walnut proteins in processed foods.

Ses i 6, the sesame 11S globulin, can activate basophils and shows cross-reactivity with walnut in vitro

BACKGROUND

Sesame allergy is increasingly being reported, and multi-sensitization to peanut and tree nuts has been described. The clinical relevance and cross-reactivity of many sesame proteins, such as Ses i 6, are unknown.

OBJECTIVE

The aims of this study were to perform a preliminary examination of the cross-reactivity of Ses i 6 in vitro, examine the ability of Ses i 6 to activate basophils in a modified basophil activation test (mBAT), and assess whether such an assay may help to distinguish between potentially relevant and irrelevant IgE reactivity towards 11S globulin proteins.

METHODS

Inhibition immunoblotting and chicken anti-rJug r 4 antibodies were used to determine the cross-reactivity of rSes i 6. Basophils from atopic donors were stripped of resident IgE before passive sensitization with food-allergic sera and challenged with protein extracts or recombinant protein. Basophil activation was measured using two activation markers, CD203c and CD63, via flow cytometry.

RESULTS

IgE immunoblotting showed cross-reactivity between rJug r 4 and rSes i 6 using sera from two human donors and chicken IgY. Additionally, rSes i 6 activated basophils passively sensitized with sesame-allergic sera. Cross-reactive serum from a sesame-allergic but walnut-tolerant donor was not able to activate basophils when challenged by walnut extract despite IgE reactivity to walnut determined by immunoblotting.

CONCLUSIONS

The sesame 11S globulin shows partial immunological cross-reactivity with walnut, and although it is classified as a minor allergen, activated basophils sensitized with serum from seven out of eleven sesame-allergic donors. Additionally, the mBAT may help distinguish between clinically relevant and irrelevant in vitro IgE cross-reactivity of seed storage proteins in nuts and seeds and thus warrants use in further studies.

Jug r 4, a legumin group food allergen from walnut (Juglans regia Cv. Chandler)

Allergy to walnut is the most frequently reported tree nut allergy in the United States. Walnut 2S albumin, a vicilin-like protein, and a lipid transfer protein allergen have previously been described. Our objective was to clone and express a cDNA encoding a legumin group protein, assess IgE-binding with sera from walnut allergic patients, and investigate cross-reactivity with selected nuts. Primers were used to obtain the cDNA by 5' and 3' rapid amplification of cDNA ends from walnut mRNA. The cDNA was subcloned into the pMAL-c2X vector and the recombinant fusion protein, named rJug r 4, was expressed in Escherichia coli. The obtained cDNA encoded a precursor protein with a predicted molecular weight of 58.1 kD, which showed significant sequence homology to hazelnut and cashew legumin allergens. Serum IgE from 21 of 37 (57%) patients bound the rJug r 4 fusion protein. In vitro cross-reactivity was demonstrated with hazelnut, cashew, and peanut protein extracts.

Improving disease resistance of butternut (Juglans cinerea), a threatened fine hardwood: a case for single-tree selection through genetic improvement and deployment

Approaches for the development of disease-resistant butternut (Juglans cinerea L.) are reviewed. Butternut is a threatened fine hardwood throughout its natural range in eastern North America because of the invasion of the exotic fungus, Sirococcus clavigignenti-juglandacearum Nair, Kostichka and Kuntz, which causes butternut canker. Early efforts were made to identify and collect putatively resistant germ plasm, identify vectors and to characterize the disease. More recently, molecular techniques have been employed to genetically characterize both the pathogen and the resistant germ plasm. Much of the host resistance may originate from hybridization with a close Asian relative, Japanese walnut (Juglans ailanthifolia Carr.), and from a few natural phenotypic variants. Further genetic characterization is needed before classical breeding or genetic modification can be used to produce canker-resistant trees.

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.

Extensive in vitro cross-reactivity to seed storage proteins is present among walnut (Juglans) cultivars and species

BACKGROUND

Tree nuts, including English walnuts (Juglans regia), are sources of food allergens often associated with life-threatening allergic reactions. It is unknown if seed storage proteins from other Juglans species have IgE epitopes similar to those of the important English walnut allergens, Jug r 1 (2S albumin) and Jug r 2 (vicilin-like).

OBJECTIVE

To screen for potential germplasm sources of hypoallergenic seed storage proteins of relevance in walnut food allergy. We sought to identify English walnut cultivars (cvs) or other Juglans species that showed decreased IgE binding to major seed storage proteins or an inability to cross-react with Jug r 1 or Jug r 2.

METHODS

We determined if IgE in sera of patients who have had life-threatening systemic reactions to English walnut bound protein extracts from all tested walnut cvs (57 cvs total) or species (six) by Western immunoblot. Further, we used immunoblot inhibition to determine the in vitro cross-reactivity of Jug r 1 and Jug r 2, native and recombinant, with several walnut species.

RESULTS

All walnut cvs and species contain allergenic proteins. Furthermore, as shown by in vitro immunoblot inhibition, the major walnut allergens in the species tested cross-reacted with those in J. regia cv. Chandler and J. nigra cv. Thomas extracts.

CONCLUSIONS

Based on our findings, it is unlikely that a composite hypoallergenic walnut could be bred from available germplasm. In addition, patients with severe allergy to English walnut are likely to be clinically allergic to all commercial English walnut cvs and other closely related Juglans species.

Anaphylaxis due to Brazil nut skin testing in a walnut-allergic subject

The diagnosis and management of nut allergy can be difficult because of the possible severity of the clinical manifestations and the cross reactivity between different species. We report a case of anaphylaxis due to skin testing in a young adult with clinically ascertained walnut allergy. After an episode of anaphylaxis due to walnut ingestion, a routine diagnostic workup was carried out, involving skin prick test with commercial extracts, prick by prick with fresh food and CAP-RAST assay for different nuts. Immediately after pricking with fresh Brazil nut, a severe episode of anaphylaxis occurred, that required epinephrine and intravenous steroids. The subject had never eaten Brazil nut before. Therefore we hypothesize a cross reactivity effect, since this phenomenon is well known for tree nuts. Our case suggests that in vivo diagnosis, especially if fresh nuts are used, should be performed only if adequate equipment to treat anaphylaxis is available.

Lipid transfer protein and vicilin are important walnut allergens in patients not allergic to pollen

BACKGROUND

Walnut is the most common cause of allergic reactions to tree nuts, as reported by large population studies. Two major allergens of walnut have been identified up until now: a 2S albumin and a vicilin-like protein.

OBJECTIVE

This study was designed to identify the walnut major allergens in the Italian population and to compare the walnut IgE-binding profile in patients with or without pollen allergy.

METHODS

We selected 46 patients either with oral allergy syndrome confirmed by open oral challenge or with systemic symptoms after ingestion of walnut. These patients' sera were used for the immunoblotting of walnut extract; the identified allergens were purified by HPLC and sequenced. A peach-walnut cross-inhibition study was then performed.

RESULTS

The only major allergen recognized by our study population was a 9-kd lipid transfer protein (LTP), recognized by 37 patients. Two other minor allergens of approximately 9-kd molecular weight, both belonging to the vicilin family, were recognized by 10 patients. IgE binding to walnut LTP was completely inhibited by peach LTP.

CONCLUSION

In Italian patients with walnut allergy confirmed by documented history of severe systemic reactions or by open oral food challenge, the major allergen is an LTP. The sensitization to this protein seems to be secondary to the sensitization to peach LTP, which acts as the primary sensitizer. LTP and vicilins were able to sensitize patients not allergic to pollen.