Functional analysis of cross-reactive immunoglobulin E antibodies: peanut-specific immunoglobulin E sensitizes basophils to tree nut allergens

BACKGROUND: Peanut and tree nuts are a major cause of food-induced anaphylaxis with an appreciable mortality. Co-sensitization to peanuts and tree nuts is a common clinical observation and may be because of peanut-specific serum IgE antibodies that cross-react with tree nut allergens. It is, however, unclear whether these cross-reactive IgE antibodies are involved in effector-cell activation. OBJECTIVE: To determine if cross-reactivity of peanut-specific IgE antibodies with tree nuts can cause effector cell activation using an in vitro basophil activation assay. METHODS: Two peanut allergic subjects with positive specific IgE for peanut and tree nuts (as measured by CAP-FEIA) were studied. Basophil activation to peanut and tree nuts, as indicated by CD63 expression, was assessed by flow cytometry to confirm co-sensitization to peanut and tree nuts. Inhibition ELISA using sera from the subjects was performed to detect peanut-specific IgE antibodies that cross-reacted with tree nut proteins. To determine whether cross-reactive tree nut allergens can induce effector-cell activation, peanut-specific antibodies were affinity purified from the subject sera and used to resensitize non-peanut/tree nut allergic donor basophils stripped of surface IgE. Basophil activation was then measured following stimulation with peanut and tree nut extracts. RESULTS: The two peanut allergic subjects in this study showed positive basophil activation to the peanut and tree nut extracts. Inhibition ELISA demonstrated that pre-incubation of the peanut allergic subject sera with almond, Brazil nut and hazelnut extracts inhibited IgE binding to peanut extract. IgE-stripped basophils from non-peanut/tree nut allergic subjects resensitized with affinity-purified peanut-specific antibodies from the peanut allergic subject sera became activated following stimulation with peanut, almond and Brazil nut extracts, demonstrating biological activity of cross-reactive IgE antibodies. CONCLUSION: Peanut-specific IgE antibodies that cross-react with tree nut allergens can cause effector-cell activation and may contribute to the manifestation of tree nut allergy in peanut allergic subjects.     

Interpretation of tests for nut allergy in one thousand patients, in relation to allergy or tolerance

BACKGROUND: Peanut and tree nut allergy are common, increasing in prevalence and the commonest food cause of anaphylaxis. In the USA, 7.8% are sensitized (have nut-specific IgE), but not all those sensitized are allergic. Lack of data makes interpretation of tests for nut-specific IgE difficult. OBJECTIVES: This is the first study to investigate the clinical significance of test results for peanut and tree nut allergy in allergic or tolerant patients. Findings are related to the severity of the allergy. METHOD: An observational study of 1000 children and adults allergic to at least one nut. History of reactions (severity graded) or tolerance to up to five nuts was obtained and skin prick test (SPT)/serum-specific IgE (CAP) performed. RESULTS: There was no correlation between SPT size and graded severity of worst reaction for all nuts combined or for peanut, hazelnut, almond and walnut. For CAP, there was no correlation for all nuts. Where patients tolerated a nut, 43% had positive SPT of 3-7 mm and 3% > or = 8 mm. For CAP, 35% were positive (0.35-14.99 kU/L) and 5% > or = 15 kU/L. In SPT range 3-7 mm, 54% were allergic and 46% were tolerant. There was poor concordance between SPT and CAP (66%). Of patients with a clear nut-allergic history, only 0.5% had negative SPT, but 22% negative CAP. CONCLUSIONS: Magnitude of SPT or CAP does not predict clinical severity, with no difference between minor urticaria and anaphylaxis. SPT is more reliable than CAP in confirming allergy. Forty-six per cent of those tolerant to a nut have positive tests > or = 3 mm (sensitized but not allergic). One cannot predict clinical reactivity from results in a wide 'grey area' of SPT 3-7 mm; 22% of negative CAPs are falsely reassuring and 40% of positive CAPs are misleading. This emphasizes the importance of the history. Understanding this is essential for accurate diagnosis. Patients with SPT > or = 8 mm and CAP > or = 15 kU/L were rarely tolerant so these levels are almost always (in > or = 95%) diagnostic.     

Tree nut allergy: risk factors for development,mitigation of reaction risk and current efforts in desensitization

Allergy to tree nuts has grown widespread among patients, specifically in the pediatric population, in recent years. In this review, we evaluate and summarize the literature specific to development and treatment of tree nut allergy. The cause of tree nut allergy, such as most food allergies, is unknown; there are theories regarding maternal dietary factors as well as sensitization related to cross-reactivity to peanut allergens. The gold standard for the diagnosis of tree nut allergy is the double-blind, placebo-controlled, oral food challenge; however, simpler and more cost-effective diagnostic methods, such as the skin prick test and serum-specific IgE are often used as a supplement for diagnosis. Management of tree nut allergy consists of dietary avoidance and using epinephrine to manage serious allergic reactions. Alternative therapeutic methods, such as oral and sublingual immunotherapy and modification of allergenic proteins are being explored to develop safer, more effective and long-lasting management of tree nut allergy. We comment on the current studies involving risk factors for sensitization, diagnosis and management of tree nut allergy.     

A multicenter study on anaphylaxis caused by peanut,tree nuts,and seeds in children and adolescents

Peanut (PN) and tree nuts (TNs) are common causes of anaphylaxis in Western countries, but no information is available in Korea. To feature clinical characteristics of anaphylaxis caused by PN, TNs, and seeds, a retrospective medical record review was performed in 14 university hospitals in Korea (2009–2013). One hundred and twenty‐six cases were identified, with the mean age of 4.9 years. PN, walnut (WN), and pine nut accounted for 32.5%, 41.3%, and 7.1%, respectively. The median values of specific IgE (sIgE) to PN, WN, and pine nut were 10.50, 8.74, and 4.61 kU_A/l, respectively. Among 50 cases managed in the emergency department, 52.0% were treated with epinephrine, 66.0% with steroid, 94.0% with antihistamines, 36.0% with oxygen, and 48.0% with bronchodilator. In conclusion, WN, PN, and pine nut were the three most common triggers of anaphylaxis in Korean children, and anaphylaxis could occur at remarkably low levels of sIgE.     

BSACI guideline for the diagnosis and management of peanut and tree nut allergy

Peanut nut and tree nut allergy are characterised by IgE mediated reactions to nut proteins. Nut allergy is a global disease. Limited epidemiological data suggest varying prevalence in different geographical areas. Primary nut allergy affects over 2% of children and 0.5% of adults in the UK. Infants with severe eczema and/or egg allergy have a higher risk of peanut allergy. Primary nut allergy presents most commonly in the first five years of life, often after the first known ingestion with typical rapid onset IgE‐mediated symptoms. The clinical diagnosis of primary nut allergy can be made by the combination of a typical clinical presentation and evidence of nut specifc IgE shown by a positive skin prick test (SPT) or specific IgE (sIgE) test. Pollen food syndrome is a distinct disorder, usually mild, with oral/pharyngeal symptoms, in the context of hay fever or pollen sensitisation, which can be triggered by nuts. It can usually be distinguish clinically from primary nut allergy. The magnitude of a SPT or sIgE relates to the probability of clinical allergy, but does not relate to clinical severity. SPT of ≥ 8 mm or sIgE ≥ 15 KU/L to peanut is highly predictive of clinical allergy. Cut off values are not available for tree nuts. Test results must be interpreted in the context of the clinical history. Diagnostic food challenges are usually not necessary but may be used to confirm or refute a conflicting history and test result. As nut allergy is likely to be a long‐lived disease, nut avoidance advice is the cornerstone of management. Patients should be provided with a comprehensive management plan including avoidance advice, patient specific emergency medication and an emergency treatment plan and training in administration of emergency medication. Regular re‐training is required.     

Role of immunoglobulin E sensitization in eczema,previously referred to as atopic dermatitis

This review aims to clarify existing knowledge on the relationship between eczema and immunoglobulin (Ig)E sensitization. Over the years this debate has been complicated by unclear definitions of what constitutes an atopic individual. The new, uniform allergy nomenclature introduced by the European Academy of Allergology and Clinical Immunology and the World Allergy Organization uses the term eczema to denote what was previously known as ‘atopic dermatitis’ or ‘atopic eczema’. Despite detailed knowledge of localized IgE–allergen interactions at the level of the skin, the exact role of IgE and IgE antibody sensitization in the disease process remains widely debated. The association between IgE sensitization and eczema has been clearly demonstrated in population-based studies. There is, however, variation in the strength of the association between IgE sensitization and eczema in hospital versus community studies. While IgE sensitization is not a useful disease discriminator, once other factors have been taken into account, knowledge of atopic status appears to have prognostic value in children with eczema, since IgE sensitization is associated with an increased risk of developing allergic respiratory disease later in life. These children may also experience a more persistent and severe disease.     

Value of immunoglobulin E density in predicting nasal and bronchial response to inhaled allergens in rhinitic and asthmatic subjects with multiple sensitizations

BACKGROUND: In atopic subjects with multiple sensitizations to inhalant allergens the relationship between the specific serum immunoglobulin (Ig) E and the in vivo response to each allergen is not well established. OBJECTIVE: To investigate the relationship between the specific serum IgE expressed as amount (kU/L) or density (specific IgE/total IgE percentage) with the in vivo response to inhaled allergens in rhinitic and asthmatic subjects with multiple sensitization. METHODS: By means of Reverse Enzyme AllergoSorbent Test (REAST) the absolute values and the density of specific IgE for each sensitizing allergen was determined. Rhinitics (n = 12) underwent nasal and asthmatics (n = 11) bronchial allergen challenges with the two to three sensitizing allergens for a total of 33 nasal and 32 bronchial challenges. Correlations and degree of concordance between specific serum IgE and results of challenges were calculated. RESULTS: IgE density significantly correlated with nasal challenge score (rs = 0.72, P < 0.001), bronchial challenge score (rs = 0.56, P < 0.001) and late asthmatic response (rp = 0.53, P < 0.005). Among subjects with three sensitizations, comparison of values of IgE density with the results of challenges showed significant concordance in graduation (chi2 = 11.3, P < 0.005). CONCLUSIONS: In subjects with multiple sensitizations, the nasal and bronchial response to the different sensitizing allergens may be predicted, at least in part, by the IgE density. A satisfactory agreement between graduation of the IgE density to the different allergens and the in vivo response to the same allergens has been found within subject.     

Patterns of immunoglobulin G responses to egg and peanut allergens are distinct: ovalbumin-specific immunoglobulin responses are ubiquitous, but peanut-specific immunoglobulin responses are up-regulated in peanut allergy

BACKGROUND: The clinical significance of food-specific IgG subclasses in food allergy and tolerance remains unclear. Specific IgG titres are often reported in non-standardized units, which do not allow comparisons between studies or allergens. OBJECTIVE: To quantify, in absolute units, ovalbumin (OVA)- and peanut-specific IgG levels in children with peanut or egg allergy (active or resolved) and in non-allergic controls. Methods Children aged 1-15 years were recruited. Peanut allergy was diagnosed by convincing history and a 95% predictive level of specific IgE; egg allergy or resolution was confirmed by oral challenge. Serum IgG, IgG1 and IgG4 levels (microg/mL) to OVA and peanut extract were quantified by ELISA. RESULTS: OVA- and peanut-specific IgG was detected in all subjects. In non-allergic controls (n=18), OVA-specific IgG levels were significantly higher than peanut-specific IgG (median microg/mL IgG=15.9 vs. 2.2, IgG1=1.3 vs. 0.6, IgG4=7.9 vs. 0.7; P<0.01). There were no differences in OVA-specific IgG, IgG1 and IgG4 between egg-allergic (n=40), egg-resolved (n=22) and control (n=18) subjects. In contrast, peanut-specific IgG (median microg/mL IgG=17.0, IgG1=3.3, IgG4=5.2) were significantly higher in peanut-allergic subjects (n=59) compared with controls and with non-peanut-sensitized but egg-allergic subjects (n=26). Overall, the range of IgG4 was greater than IgG1, and IgG4 was the dominant subclass in >60% of all subjects. CONCLUSION: OVA-specific IgG levels of egg-allergic, egg-resolved or control groups are not distinguishable. Higher peanut-specific IgG levels are associated with clinical allergy, but the range of IgG titres of the allergic and control groups overlapped. Hence, OVA and peanut-specific IgG measurements do not appear to be of diagnostic value. Strong IgG responses to OVA may be a normal physiological response to a protein frequently ingested from infancy, whereas up-regulated IgG responses in peanut allergy may be indicative of a dysregulated immune response to peanut allergens.     

Oral tolerance induction to Dermatophagoides pteronyssinus and Blomia tropicalis in sensitized mice: occurrence of natural autoantibodies to immunoglobulin E

BACKGROUND: The dust mites Dermatophagoides pteronyssinus (Dp) and Blomia tropicalis (Bt) are important sources of indoor allergens in tropical and subtropical countries. Murine models allow the analysis of the immune response and regulation of IgE production to Dp and Bt allergens. Oral tolerance induces unresponsiveness in naive animals, but its application in sensitized animals can provide useful information to improve allergy therapy. OBJECTIVE: To study the profile of IgE and IgG subclasses antibody upon oral administration with Bt and Dp extract in previously sensitized mice. Further, the occurrence of autoantibodies IgG anti-IgE in the immunization and in the oral tolerance was investigated. METHODS: A/Sn mice were immunized with Bt or Dp extract in alum, orally administrated with 0.25 mg of Bt or Dp extract or PBS at the 6th, 7th and 8th days after immunization and boosted twice with their respective allergens. To analyse the mice groups, specific IgE antibodies were measured by passive anaphylaxis reaction and specific IgG subclasses and anti-IgE IgG autoantibody by ELISA assay. RESULTS: IgE levels were markedly increased in Bt-immunized mice compared with Dp-immunized mice. A distinct profile of the specific isotypes was verified in Bt-immunized mice with a preferential production of IgG3 and IgA antibodies, whereas Dp-immunized mice developed high titres of anti-Dp IgG1, IgG2a and IgG2b antibodies. The antigen feeding inhibited IgE response in both fed-mice groups but only Dp-fed mice presented decreased levels of IgG antibodies. Free anti-IgE IgG autoantibodies were detected mainly in the Dp-immunization and they correlated with the antibody isotypes found against the allergen. CONCLUSIONS: This is the first time that the murine-type I hypersensitivity is employed to study Bt-immunization, showing a marked IgE production, associated with IgG response, which is at least in part driven by T-independent antigens. The oral tolerance protocol in previously sensitized animals was able to down-modulate IgE response and points out this route as a strategy for allergy therapy.     

Association and functional relevance of E237G, a polymorphism of the high-affinity immunoglobulin E-receptor β chain gene, to airway hyper-responsiveness

BACKGROUND: The hyper-sensitivity reaction of IgE, with its high-affinity receptors (FcepsilonRI), is central to the phenomenon of atopic diseases. OBJECTIVE: To evaluate the genetic effects of non-synonymous single-nucleotide polymorphisms (SNPs) of FcepsilonRI on intermediate phenotypes of asthma, i.e. atopy and airway hyper-responsiveness (AHR), in the Korean general population. SUBJECTS AND METHODS: Atopy and AHR were evaluated in a cohort of 2055 subjects, aged 10-18 years, using skin prick tests (SPTs) for common aeroallergens and total serum IgE and methacholine bronchial provocation tests. All FcepsilonRI-alpha, FcepsilonRI-beta, and FcepsilonRI-gamma gene exons of 24 healthy subjects were sequenced to locate informative non-synonymous SNPs (minor allele frequency>2%). Informative SNPs were then scored, using the high-throughput single base extension method. Relative risk (RR) was determined by multiple logistic regression analysis, after adjusting for confounding factors. The functional relevance of non-synonymous SNPs was analysed using the sorting intolerant from tolerant (SIFT) program. RESULTS: The SNP search found only one informative non-synonymous SNP in FcepsilonRI-beta: E237G (minor allele frequency=0.21). The positive rate of AHR was lower among subjects with the 237*E allele than among those with 237*G [RR (95% confidence interval)=0.41 (0.19-0.89); P=0.01]. However, the E237G substitution was not associated with either a positive SPT response or total serum IgE levels. Sequence evolution analysis predicted that the E237G variation is an intolerant amino acid substitution, with functional importance. CONCLUSION: In the Korean general population, AHR is significantly associated with the E237G polymorphism of FcepsilonRI-beta, which results in an intolerant amino acid substitution.     

IgE, IgG1, and IgG4 antibody responses to Blomia tropicalis in atopic patients

BACKGROUND: Allergens from house dust mites (HDMs), Dermatophagoides pteronyssinus and Blomia tropicalis are clinically relevant in atopic respiratory diseases in tropical countries. AIMS OF THE STUDY: To evaluate immunoglobulin (Ig)E, IgG1, and IgG4 antibody responses to B. tropicalis in Brazilian atopic patients. METHODS: About 110 patients with allergic rhinitis with/without asthma and 33 control subjects underwent skin prick testing (SPT) with HDM extracts, and their sera were tested for IgE and IgG subclass antibodies to D. pteronyssinus and B. tropicalis by enzyme-linked immunosorbent assay (ELISA) and immunoblotting. RESULTS: Most patients (56%) had positive SPT to B. tropicalis extract (B. tropicalis+ group), although 51% were reactive to both B. tropicalis and D. pteronyssinus and 6% were sensitized to B. tropicalis only. IgE-ELISA detected 43%B. tropicalis positivity with high-specific IgE levels in B. tropicalis+ patients. Specific IgG4 levels were higher in B. tropicalis+ than B. tropicalis- groups and correlated with specific IgE levels. The IgG1 levels to B. tropicalis were higher in patients than controls. The major allergenic B. tropicalis components recognized by B. tropicalis+ patient sera were the 54, 66, and 68 kDa proteins. The IgG4-binding protein profiles closely resembled that of IgE. The IgG1 antibodies recognizing multiple B. tropicalis protein species were detected in sera of all three patient groups. CONCLUSIONS: A large percentage of our allergic patients are B. tropicalis+. They are more frequently sensitized to high-molecular weight (HMW) B. tropicalis components than the major low-molecular weight (11-15 kDa) allergens detected in other studies. The results suggest that HMW B. tropicalis antigenic components are potential candidates for evaluating allergen exposure and sensitization, and for immunotherapy treatment.     

Total serum immunoglobulin E levels in a case–control study in asthmatic/allergic patients, their family members, and healthy subjects from India

BACKGROUND: Total immunoglobulin E (IgE) is an important indicator of allergic disorders. However, its role in allergic patients in India has not been evaluated in relation to atopic status for a reference range as compared with healthy subjects. OBJECTIVE: The aim of the study was to establish serum IgE levels in a diseased group, study its relationship with atopy, and to compare the same with healthy volunteers in Indian subjects. METHODS: Four hundred and eighty asthmatics/allergic patients, 100 first-degree relatives of asthmatics, and 120 unrelated normal healthy volunteers from Delhi region were recruited for the study. Atopy was established by family history and skin test to common indigenous allergens and, total and specific IgE measurements. Statistical analysis was performed with the help of SPSS software program. RESULTS: The mean IgE levels were the highest in asthmatic patients and the lowest in the control healthy group. IgE was significantly high in the male than the female healthy volunteers (P<0.05), but not in the diseased group. Prosopis juliflora among pollen allergens and Alternaria alternata among fungal allergens were important sensitizers in allergic patients with 34.7% and 17.7% skin positivity, respectively. Atopic status and asthma were found to be the best predictor of IgE, which was highly significant (r(2)=0.239, P<0.00001). However, at 95% confidence interval as many as 50% of asthmatic patients had their IgE values in the normal range. CONCLUSION: The IgE levels in Indian allergic patients is significantly related to atopy, but due to wide overlap of IgE levels in patients and healthy subjects, its diagnostic significance in Indian population seems to be limited.