Evolution and predictive value of IgE responses toward a comprehensive panel of house dust mite allergens during the first 2 decades of life

BACKGROUND

The evolution of the IgE response to the numerous allergen molecules of Dermatophagoides pteronyssinus is still unknown.

OBJECTIVES

We sought to characterize the evolutionary patterns of the IgE response to 12 molecules of D pteronyssinus from birth to adulthood and to investigate their determinants and clinical relevance.

METHODS

We investigated the clinical data and sera of 722 participants in the German Multicenter Allergy Study, a birth cohort started in 1990. Diagnoses of current allergic rhinitis (AR) related to mite allergy and asthma were based on yearly interviews at the ages of 1 to 13 years and 20 years. IgE to the extract and 12 molecules of D pteronyssinus were tested by means of ImmunoCAP and microarray technology, respectively, in sera collected at ages 1, 2, 3, 5, 6, 7, 10, 13, and 20 years. Exposure to mites at age 6 and 18 months was assessed by measuring Der p 1 weight/weight concentration in house dust.

RESULTS

One hundred ninety-one (26.5%) of 722 participants ever had IgE to D pteronyssinus extract (≥0.35 kU_A/L). At age 20 years, their IgE recognized most frequently Der p 2, Der p 1, and Der p 23 (group A molecules; prevalence, >40%), followed by Der p 5, Der p 7, Der p 4, and Der p 21 (group B molecules; prevalence, 15% to 30%) and Der p 11, Der p 18, clone 16, Der p 14, and Der p 15 (group C molecules; prevalence, <10%). IgE sensitization started almost invariably with group A molecules and expanded sequentially first to group B and finally to group C molecules. Early IgE sensitization onset, parental hay fever, and higher exposure to mites were associated with a broader polymolecular IgE sensitization pattern. Participants reaching the broadest IgE sensitization stage (ie, ABC) had significantly higher risk of mite-related AR and asthma than unsensitized participants. IgE to Der p 1 or Der p 23 at age 5 years or less predicted asthma at school age.

CONCLUSIONS

Parental hay fever and early exposure to D pteronyssinus allergens promote IgE polysensitization to several D pteronyssinus molecules, which in turn predicts current mite-related AR and current/future asthma. These results might inspire predictive algorithms and prevention strategies against the progression of IgE sensitization to mites toward AR and asthma.

Evolution pathways of IgE responses to grass and mite allergens throughout childhood

BACKGROUND

Little is known about longitudinal patterns of the development of IgE to distinct allergen components.

OBJECTIVE

We sought to investigate the evolution of IgE responses to allergenic components of timothy grass and dust mite during childhood.

METHODS

In a population-based birth cohort (n = 1184) we measured IgE responses to 15 components from timothy grass and dust mite in children with available samples at 3 time points (ages 5, 8, and 11 years; n = 235). We designed a nested, 2-stage latent class analysis to identify cross-sectional sensitization patterns at each follow-up and their longitudinal trajectories. We then ascertained the association of longitudinal trajectories with asthma, rhinitis, eczema, and lung function in children with component data for at least 2 time points (n = 534).

RESULTS

Longitudinal latent class analysis revealed 3 grass sensitization trajectories: (1) no/low sensitization; (2) early onset; and (3) late onset. The early-onset trajectory was associated with asthma and diminished lung function, and the late-onset trajectory was associated with rhinitis. Four longitudinal trajectories emerged for mite: (1) no/low sensitization; (2) group 1 allergens; (3) group 2 allergens; and (3) complete mite sensitization. Children in the complete mite sensitization trajectory had the highest odds ratios (ORs) for asthma (OR, 7.15; 95% CI, 3.80-13.44) and were the only group significantly associated with comorbid asthma, rhinitis, and eczema (OR, 5.91; 95% CI, 2.01-17.37). Among children with wheezing, those in the complete mite sensitization trajectory (but not other longitudinal mite trajectories) had significantly higher risk of severe exacerbations (OR, 3.39; 95% CI, 1.62-6.67).

CONCLUSIONS

The nature of developmental longitudinal trajectories of IgE responses differed between grass and mite allergen components, with temporal differences (early vs late onset) dominant in grass and diverging patterns of IgE responses (group 1 allergens, group 2 allergens, or both) in mite. Different longitudinal patterns bear different associations with clinical outcomes, which varied by allergen.

Diagnostic accuracy, risk assessment, and cost-effectiveness of component-resolved diagnostics for food allergy: A systematic review

BACKGROUND

Component-resolved diagnostics (CRD) are promising tools for diagnosing food allergy, offering the potential to determine specific phenotypes and to develop patient-tailored risk profiles. Nevertheless, the diagnostic accuracy of these tests varies across studies; thus, their clinical utility remains unclear. Therefore, we synthesized the evidence from studies investigating the diagnostic accuracy, risk assessment ability, and cost-effectiveness of CRD for food allergy.

METHODS

We systematically searched 10 electronic databases and four clinical trial registries for studies published from January 2000 to February 2017. The quality of included studies was assessed using QUADAS-2. Due to heterogeneity, we narratively synthesized the evidence.

RESULTS

Eleven studies met inclusion criteria, altogether recruiting 1098 participants. The food allergies investigated were cow's milk, hen's egg, peanut, hazelnut, and shrimp. The components with the highest diagnostic accuracy for each allergen, along with their sensitivity-specificity pairs, were as follows: Bos d 4 for cow's milk (62.0% and 87.5%), Gal d 1 for hen's egg (84.2% and 89.8% for heated egg, and 60.6% and 97.1% for raw egg), Ara h 6 for peanut (94.9% and 95.1%), Cor a 14 for hazelnut (100% and 93.8%), and Lit v 1 for shrimp (82.8% and 56.3%) allergy.

CONCLUSION

Selected components of cow's milk, hen's egg, peanut, hazelnut, and shrimp allergen showed high specificity, but lower sensitivity. However, few studies exist for each component, and studies vary widely regarding the cutoff values used, making it challenging to synthesize findings across studies. Further research is needed to determine clinically appropriate cutoff values, risk assessment abilities, and cost-effectiveness of CRD approaches.

Patterns of IgE responses to multiple allergen components and clinical symptoms at age 11 years

BACKGROUND

The relationship between sensitization to allergens and disease is complex.

OBJECTIVE

We sought to identify patterns of response to a broad range of allergen components and investigate associations with asthma, eczema, and hay fever.

METHODS

Serum specific IgE levels to 112 allergen components were measured by using a multiplex array (Immuno Solid-phase Allergen Chip) in a population-based birth cohort. Latent variable modeling was used to identify underlying patterns of component-specific IgE responses; these patterns were then related to asthma, eczema, and hay fever.

RESULTS

Two hundred twenty-one of 461 children had IgE to 1 or more components. Seventy-one of the 112 components were recognized by 3 or more children. By using latent variable modeling, 61 allergen components clustered into 3 component groups (CG1, CG2, and CG3); protein families within each CG were exclusive to that group. CG1 comprised 27 components from 8 plant protein families. CG2 comprised 7 components of mite allergens from 3 protein families. CG3 included 27 components of plant, animal, and fungal origin from 12 protein families. Each CG included components from different biological sources with structural homology and also nonhomologous proteins arising from the same biological source. Sensitization to CG3 was most strongly associated with asthma (odds ratio [OR], 8.20; 95% CI, 3.49-19.24; P < .001) and lower FEV1 (P < .001). Sensitization to CG1 was associated with hay fever (OR, 12.79; 95% CI, 6.84-23.90; P < .001). Sensitization to CG2 was associated with both asthma (OR, 3.60; 95% CI, 2.05-6.29) and hay fever (OR, 2.52; 95% CI, 1.38-4.61).

CONCLUSIONS

Latent variable modeling with a large number of allergen components identified 3 patterns of IgE responses, each including different protein families. In 11-year-old children the pattern of response to components of multiple allergens appeared to be associated with current asthma and hay fever but not eczema.

Ana o 3-specific IgE is a good predictor for clinically relevant cashew allergy in children

INTRODUCTION

Component-resolved diagnostics using specific IgE to 2 S albumins has shown to be a valuable new option in diagnostic procedure. Ana o 3 is a 2 S albumin from cashew. The aim of this study was to investigate the role of Ana o 3-specific serum IgE in the diagnosis of cashew allergy and to identify cut-off levels to replace oral food challenges. Moreover, the value of additional determination of total IgE has been investigated.

METHODS

In a multicentre study, we analysed specific IgE to cashew extract and Ana o 3 as well as total IgE in children with suspected cashew allergy using the ImmunoCAP-FEIA and a standardized diagnostic procedure including oral challenges where indicated.

RESULTS

A total of 61 patients were included in the study. Forty-two were allergic to cashew, and 19 were tolerant. In receiver operating curves, Ana o 3 discriminates between allergic and tolerant children better than cashew-specific IgE with an area under the curve of 0.94 vs 0.78. The ratio of Ana o 3-specific IgE to total IgE did not further improve the diagnostic procedure. Probability curves for Ana o 3-specific IgE have been calculated, and a 95% probability could be estimated at 2.0 kU/l.

CONCLUSION

Specific IgE to Ana o 3 is a valuable tool for the diagnosis of cashew allergy. Considering its positive predictive value, it might allow to make a considerable number of oral challenges superfluous.

Molecular diagnosis for allergen immunotherapy

The extensive use of allergen molecules in birth cohort studies revealed that atopic sensitization is a sequential IgE response to distinct non-cross-reacting molecules from the same allergenic source (ie, molecular spreading), starting with an initiator molecule. This phenomenon reaches different degrees of progression (monomolecular, oligomolecular, and polymolecular) according to the individual atopic propensity and allergen exposure, thus producing an extreme heterogeneity of IgE sensitization profiles in patient populations. In patients with allergic rhinitis, the broader the IgE molecular sensitization profile, the greater is the risk of asthma and other allergic comorbidities, such as oral allergy syndrome. Hence it has been proposed to anticipate immunologic intervention at disease onset (early allergen immunotherapy) or even earlier during the preclinical sensitization stage (allergen immunoprophylaxis). Diagnostic algorithms based on singleplex or multiplex molecular IgE tests allow the discrimination of genuine from cross-reacting sensitization and the selection of the right extracts for allergen immunotherapy composition. Patients with extreme molecular poly-sensitization and greater risk of asthma or other IgE-mediated comorbidities, can be easily identified by means of allergen microarray or macroarray procedures and might benefit from anti-IgE treatment. IgE molecular tests have opened the era of precision allergology, and their routine use should aim at cost-effectiveness, according to the principles of the Choosing Wisely initiative.

Sesame allergy: current perspectives

Sesame is an important global allergen affecting ~0.1% of the North American population. It is a major cause of anaphylaxis in the Middle East and is the third most common food allergen in Israel. We conducted a systematic review of original articles published in the last 10 years regarding the diagnosis and management of sesame allergy. Skin prick testing appears to be a useful predictor of sesame allergy in infants, although data are less consistent in older children and adults. The diagnostic capacity of serum-specific immunoglobulin E is poor, especially in studies that used oral food challenges to confirm the diagnosis. Double-blind, placebo-controlled food challenge thus remains the diagnostic gold standard for sesame allergy. The cornerstone of sesame allergy management is allergen avoidance, though accidental exposures are common and patients must be prepared to treat the consequent reactions with epinephrine. Novel diagnostic and treatment options such as component-resolved diagnostics, basophil activation testing, and oral immunotherapy are under development but are not ready for mainstream clinical application.

Evolution of IgE responses to multiple allergen components throughout childhood

BACKGROUND

There is a paucity of information about longitudinal patterns of IgE responses to allergenic proteins (components) from multiple sources.

OBJECTIVES

This study sought to investigate temporal patterns of component-specific IgE responses from infancy to adolescence, and their relationship with allergic diseases.

METHODS

In a population-based birth cohort, we measured IgE to 112 components at 6 follow-ups during childhood. We used a Bayesian method to discover cross-sectional sensitization patterns and their longitudinal trajectories, and we related these patterns to asthma and rhinitis in adolescence.

RESULTS

We identified 1 sensitization cluster at age 1, 3 at age 3, 4 at ages 5 and 8, 5 at age 11, and 6 at age 16 years. "Broad" cluster was the only cluster present at every follow-up, comprising components from multiple sources. "Dust mite" cluster formed at age 3 years and remained unchanged to adolescence. At age 3 years, a single-component "Grass" cluster emerged, which at age 5 years absorbed additional grass components and Fel d 1 to form the "Grass/cat" cluster. Two new clusters formed at age 11 years: "Cat" cluster and "PR-10/profilin" (which divided at age 16 years into "PR-10" and "Profilin"). The strongest contemporaneous associate of asthma at age 16 years was sensitization to dust mite cluster (odds ratio: 2.6; 95% CI: 1.2-6.1; P < .05), but the strongest early life predictor of subsequent asthma was sensitization to grass/cat cluster (odds ratio: 3.5; 95% CI: 1.6-7.4; P < .01).

CONCLUSIONS

We describe the architecture of the evolution of IgE responses to multiple allergen components throughout childhood, which may facilitate development of better diagnostic and prognostic biomarkers for allergic diseases.

Challenges in interpreting allergen microarrays in relation to clinical symptoms: a machine learning approach

BACKGROUND

Identifying different patterns of allergens and understanding their predictive ability in relation to asthma and other allergic diseases is crucial for the design of personalized diagnostic tools.

METHODS

Allergen-IgE screening using ImmunoCAP ISAC(®) assay was performed at age 11 yrs in children participating a population-based birth cohort. Logistic regression (LR) and nonlinear statistical learning models, including random forests (RF) and Bayesian networks (BN), coupled with feature selection approaches, were used to identify patterns of allergen responses associated with asthma, rhino-conjunctivitis, wheeze, eczema and airway hyper-reactivity (AHR, positive methacholine challenge). Sensitivity/specificity and area under the receiver operating characteristic (AUROC) were used to assess model performance via repeated validation.

RESULTS

Serum sample for IgE measurement was obtained from 461 of 822 (56.1%) participants. Two hundred and thirty-eight of 461 (51.6%) children had at least one of 112 allergen components IgE > 0 ISU. The binary threshold >0.3 ISU performed less well than using continuous IgE values, discretizing data or using other data transformations, but not significantly (p = 0.1). With the exception of eczema (AUROC~0.5), LR, RF and BN achieved comparable AUROC, ranging from 0.76 to 0.82. Dust mite, pollens and pet allergens were highly associated with asthma, whilst pollens and dust mite with rhino-conjunctivitis. Egg/bovine allergens were associated with eczema.

CONCLUSIONS

After validation, LR, RF and BN demonstrated reasonable discrimination ability for asthma, rhino-conjunctivitis, wheeze and AHR, but not for eczema. However, further improvements in threshold ascertainment and/or value transformation for different components, and better interpretation algorithms are needed to fully capitalize on the potential of the technology.

Diagnostic relevance of IgE sensitization profiles to eight recombinant Phleum pratense molecules

BACKGROUND

Grass pollen-related seasonal allergic rhinoconjunctivitis (SARg) is clinically heterogeneous in severity, comorbidities, and response to treatment. The component-resolved diagnostics disclosed also a high heterogeneity at molecular level. Our study aimed at analyzing the characteristics of the IgE sensitization to Phleum pratense molecules and investigating the diagnostic relevance of such molecules in childhood.

METHODS

We examined 1120 children (age 4-18 years) with SARg. Standardized questionnaires on atopy were acquired through informatics platform (AllergyCARD™). Skin prick tests were performed with pollen extracts. Serum IgE to airborne allergens and eight P. pratense molecules (rPhl p 1, rPhl p 2, rPhl p 4, rPhl p 5b, rPhl p 6, rPhl p 7, rPhl p 11, rPhl p 12) were tested by ImmunoCAP FEIA.

RESULTS

The analysis of IgE responses against eight P. pratense molecules showed 87 profiles. According to the number of molecules recognized by IgE, the more complex profiles were characterized by higher serum total IgE, higher grass-specific serum IgE, and higher number and degree of sensitization to pollens. The most frequent IgE sensitization profile was the monomolecular Phl p 1. Sensitization to Phl p 7 was a reliable biomarker of asthma, whereas Phl p 12 of oral allergy syndrome. Sensitization to Phl p 7 was associated with a higher severity of SARg, and complex profiles were associated with longer disease duration.

CONCLUSIONS

In a large pediatric population, the complexity of IgE sensitization profiles against P. pratense molecules is related to high atopic features although useless for predicting the clinical severity. The detection of serum IgE to Phl p 1, Phl p 7, and Phl p 12 can be used as clinical biomarkers of SARg and comorbidities. Further studies in different areas are required to test the impact of different IgE molecular profiles on AIT response.

Systematic review and meta-analyses on the accuracy of diagnostic tests for IgE-mediated food allergy

The European Academy of Allergy and Clinical Immunology (EAACI) is updating the Guidelines on Food Allergy Diagnosis. We aimed to undertake a systematic review of the literature with meta-analyses to assess the accuracy of diagnostic tests for IgE-mediated food allergy. We searched three databases (Cochrane CENTRAL (Trials), MEDLINE (OVID) and Embase (OVID)) for diagnostic test accuracy studies published between 1 October 2012 and 30 June 2021 according to a previously published protocol (CRD42021259186). We independently screened abstracts, extracted data from full texts and assessed risk of bias with QUADRAS 2 tool in duplicate. Meta-analyses were undertaken for food-test combinations for which three or more studies were available. A total of 149 studies comprising 24,489 patients met the inclusion criteria and they were generally heterogeneous. 60.4% of studies were in children ≤12 years of age, 54.3% were undertaken in Europe, ≥95% were conducted in a specialized paediatric or allergy clinical setting and all included oral food challenge in at least a percentage of enrolled patients, in 21.5% double-blind placebo-controlled food challenges. Skin prick test (SPT) with fresh cow's milk and raw egg had high sensitivity (90% and 94%) for milk and cooked egg allergies. Specific IgE (sIgE) to individual components had high specificity: Ara h 2-sIgE had 92%, Cor a 14-sIgE 95%, Ana o 3-sIgE 94%, casein-sIgE 93%, ovomucoid-sIgE 92/91% for the diagnosis of peanut, hazelnut, cashew, cow's milk and raw/cooked egg allergies, respectively. The basophil activation test (BAT) was highly specific for the diagnosis of peanut (90%) and sesame (93%) allergies. In conclusion, SPT and specific IgE to extracts had high sensitivity whereas specific IgE to components and BAT had high specificity to support the diagnosis of individual food allergies.

Molecular-based allergy diagnosis of allergic bronchopulmonary aspergillosis in Aspergillus fumigatus-sensitized Japanese patients

BACKGROUND

Distinguishing between patients with allergic bronchopulmonary aspergillosis (ABPA) and Aspergillus fumigatus (Af)-sensitized asthmatic patients without ABPA is sometimes difficult owing to the IgE-cross-reactivity between Af and other fungal allergens.

OBJECTIVE

To establish the usefulness of molecular-based allergy diagnostics using allergen components from Af in distinguishing ABPA from Af-sensitized asthma without ABPA.

METHODS

Sera from Japanese patients with ABPA (n = 53) and Af-sensitized asthma without ABPA (n = 253) were studied. The levels of IgE and IgG antibodies to allergen components from Af and IgE antibodies to different fugal allergen extracts were measured by ImmunoCAP. Comorbid atopic dermatitis (AD) was taken into consideration in the sensitization profile analysis.

RESULTS

Patients with ABPA possessed significantly higher levels of IgE antibodies to Asp f 1, and Asp f 2 than asthmatic patients without ABPA. The areas under the receiver operating characteristic curves for the levels of IgE to Asp f 1 and Asp f 2 as diagnostic markers of ABPA were 0.75 and 0.78, respectively. The presence of IgE positivity to Asp f 1 and/or Asp f 2 resulted in increased sensitivity while losing little specificity. Comorbid AD was associated with higher levels of IgE to Asp f 6 (manganese superoxide dismutase from Af, a ubiquitous pan-allergen in fungi) and low but positive levels of IgE to other Af-components, which hampered the serological discrimination of ABPA.

CONCLUSIONS AND CLINICAL RELEVANCE

The levels of IgE to Asp f 1 and/or Asp f 2 can effectively differentiate ABPA from Af-sensitized asthma, suggesting that the amounts of IgE specific for these molecules are markers for genuine Af-sensitization in ABPA. However, comorbid AD must be taken into consideration in the interpretation of high IgE to Asp f 6. Establishing of IgE-sensitization profiles using panel of Af-allergen components provides valuable information for distinguishing genuine vs. cross-reactive sensitization in Af-sensitized patients.

Utility of recombinant Aspergillus fumigatus antigens in the diagnosis of allergic bronchopulmonary aspergillosis: A systematic review and diagnostic test accuracy meta-analysis

BACKGROUND

The role of recombinant A. fumigatus (rAsp) antigens in the diagnosis of allergic bronchopulmonary aspergillosis (ABPA) has not been systematically evaluated. Herein, we evaluate the utility of recombinant A. fumigatus (rAsp) antigens in diagnosing ABPA.

METHODS

We systematically reviewed the PubMed, EmBase and Scopus databases for studies evaluating rAsp antigens in ABPA. The QUADAS-2 tool and the GRADE approach were used to assess the risk of bias and the quality of evidence, respectively. The diagnostic performance of IgE or skin test against rAsp f1, f2, f3, f4, f6 and their combination was evaluated separately for ABPA complicating asthma or cystic fibrosis (CF), using an HSROC model. The reference standard for diagnosing ABPA was the composite (clinical, radiological, immunological) criteria.

RESULTS

Our search yielded 26 studies (n = 1694) and 17 studies (n = 1131) for inclusion in the systematic review and meta-analysis, respectively. In asthmatics, the pooled sensitivity for diagnosing ABPA was best for IgE against a combination of rAsp f1 or f3 (96.7%; 95% confidence interval [CI], 87.6-99.2). The pooled specificity for diagnosing ABPA was highest (99.2%; 95% CI, 88.2-99.9) for IgE against a combination of f4 or f6. In CF patients, the pooled sensitivity of rAsp f1 or f3 was 93.3% (95% CI, 55.2-99.9) while the pooled specificity of rAsp f4 or f6 was 93.9% (95% CI, 68.8-99.9). The quality of evidence was low as per the GRADE approach.

CONCLUSIONS

A combination of IgE against rAsp antigens (f1, f2, f3, f4 and f6) is likely to be helpful in the diagnosis of ABPA.

Update on food allergy

Food allergies are a global health issue with increasing prevalence. Allergic reactions can range from mild local symptoms to severe anaphylactic reactions. Significant progress has been made in diagnostic tools such as component-resolved diagnostics and its impact on risk stratification as well as in therapeutic approaches including biologicals. However, a cure for food allergy has not yet been achieved and patients and their families are forced to alter eating habits and social engagements, impacting their quality of life. New technologies and improved in vitro and in vivo models will advance our knowledge of the pathogenesis of food allergies and multicenter-multinational cohort studies will elucidate interactions between genetic background, lifestyle, and environmental factors. This review focuses on new insights and developments in the field of food allergy and summarizes recently published articles.

Allergen components in diagnosing childhood hazelnut allergy: Systematic literature review and meta-analysis

BACKGROUND

Hazelnut-specific IgE antibodies (sIgEs) in serum support the diagnosis of hazelnut allergy, but extract-based tests have low diagnostic specificity, commonly leading to over-diagnosis. Measuring sensitization to individual allergen components may enhance the diagnosis of hazelnut allergy. We systematically examined data on diagnostic accuracy of sIgE to commercially available hazelnut components to compare their individual contributions in diagnosing hazelnut allergy.

METHODS

Seven databases were searched for diagnostic studies on patients suspected of having hazelnut allergy. Studies employing component-specific IgE testing on patients whose final diagnosis was determined by oral food challenges were included in the meta-analysis. Study quality was assessed as recommended by Cochrane.

RESULTS

Seven cross-sectional studies and one case-control study were identified, seven presenting data on children (N = 635), and one on a mixed age population. Overall, the diagnostic accuracies of sIgE to both Cor a 9 and Cor a 14 were significantly higher than for Cor a 1-sIgE (P < .05). In children, the specificity of Cor a 14-sIgE at 0.35 kU_A /L cutoff was 81.7% (95% CI 77.1, 85.6), and 67.3% (60.3, 73.6) for Cor a 9-sIgE. The specificities for Cor a 1-sIgE and hazelnut-sIgE were 22.5% (7.4, 51.2) and 10.8% (3.4, 29.8), respectively. The sensitivity of Cor a 1-sIgE (60.2% [46.9, 72.2]) was lower than for hazelnut extract-sIgE (95.7% [88.7, 98.5]), while their specificities did not differ significantly.

CONCLUSION

sIgE to Cor a 14 and Cor a 9 hazelnut storage proteins increases diagnostic specificity in assessing hazelnut allergy in children. The combined use of hazelnut extract and hazelnut storage proteins may improve diagnostic value.

Accuracy of component-resolved diagnostics in peanut allergy: Systematic literature review and meta-analysis

BACKGROUND

Peanut allergy diagnosis relies on clinical reactivity to peanut supported by detection of specific IgE (sIgE) antibodies. Extract-based sIgE tests have low specificity, so component-resolved diagnostics may complement whole-extract testing.

METHODS

We systematically collected peanut allergen component data in seven databases and studied the diagnostic accuracy of peanut storage proteins (Arah1, 2, 3) and cross-reactive peanut proteins (Arah8 PR-10 and Arah9 lipid transfer protein) through meta-analyses. The systematic literature review included studies employing peanut components and oral food challenge (OFC) as reference standard in patients suspected of peanut allergy. Data for component sIgE at pre-defined detection thresholds were extracted and combined in random-effects bivariate meta-analyses. Risk of bias was assessed as recommended by Cochrane, with two additional quality items of importance for this review.

RESULTS

Nineteen eligible studies presented data suitable for meta-analysis. In cross-sectional pediatric studies, the pooled sensitivity of Arah2-sIgE at 0.35 kU_A /L cutoff was 83.3% [95% CI 75.6, 88.9] and specificity in diagnosing objective peanut allergy was 83.6% [95% CI 77.4, 88.4]. Compared with 0.1 and 1.0 kU_A /L, this threshold provided the best diagnostic accuracy. At 0.35 kU_A /L, Arah1 and Arah3 had comparable specificity (86.0% and 88.0%, respectively) but significantly lower sensitivity compared with Arah2 (37.0% and 39.1%, respectively; P < .05).

CONCLUSION

sIgE to Arah2 can enhance the certainty of diagnosis and reduce the number of OFC necessary to rule out clinical peanut allergy in unclear cases.

Cow's milk allergic children-Can component-resolved diagnostics predict duration and severity?

BACKGROUND

Cow's milk allergy (CMA) affects 2% of all children. This study investigatescomponent-resolved diagnostics(CRD) to cow's milk proteins in children suspected of CMA, by correlating the level of CRD with outcome of the oral challenge. Furthermore, we evaluate the ability of serial CRD measurements to distinguish children with persistent CMA from children developing tolerance.

METHODS

We included data from 78 children referred to the Allergy Centre during a 13-year period. Results from oral food challenges including threshold, severity, and sensitization data (IgE antibodies to whole milk protein, IgE components toward milk and skin prick test (SPT)) were collected. The milk allergic children were re-evaluated with sensitization data and rechallenges regularly.

RESULTS

Thirty-nine children had negative first challenges, and 39 had positive first challenges. The positive group was rechallenged and separated into 3 groups depending on time to remission. At inclusion, children with persistent CMA had significantly larger size of SPT and higher levels of s-IgE to milk and CRD compared to the other groups. SPT wheal size was significantly larger in children with persistent CMA compared to children outgrowing CMA. Furthermore, a correlation between s-IgE level to cow's milk and casein and the severity of the allergic reaction elicited by food challenges was found.

CONCLUSION

Oral food challenge cannot be replaced by s-IgE to whole milk protein or milk components nor SPT in the diagnosis of CMA; however, high levels of milk components and s-IgE to milk increase the risk of a long-lasting or persisting CMA.

Component-resolved diagnostics in pet allergy: Current perspectives and future directions

Furry mammals kept as pets are important allergen sources. The prevalence of sensitization to dander from various animals appears to be increasing worldwide. Several mammalian allergens from diverse species and distinct protein families have been characterized, and some are available for component-resolved diagnostics (CRD). This review presents an overview of mammalian aeroallergens, with a focus on cat, dog, and horse allergens. The potential of CRD in fine-tuning the diagnostic workup following traditional methods based on whole- allergen extracts and allergen immunotherapy is discussed. The review highlights the clinical utility of CRD, particularly as a marker/predictor of increased asthma risk and disease severity. Finally, several perspectives of the future implications of CRD are offered in the context of furry animal allergens.

Food allergy endotype with high risk of severe anaphylaxis in children-Monosensitization to cashew 2S albumin Ana o 3

BACKGROUND

Food allergy in children can be life-threatening. Component-resolved diagnostics approach to food anaphylaxis is rarely assessed in children. The aim of the study was to identify the food allergen components as the triggers responsible for severe anaphylaxis, with regard to characteristics and associated risks, among children in a large, population-based setting.

METHODS

Two hundred and seventy-one children who were hospitalized due to systemic allergic reaction (SAR) and food anaphylaxis were recruited. Medical history was assessed, and culprit allergen source and anaphylaxis severity grade were established. Specific IgE to 112 allergen components using multiplex ImmunoCAP ISAC immunoassay and specific IgE to hazelnut, Cor a 14, and cashew, Ana o 3, using singleplex ImmunoCAP immunoassay were determined.

RESULTS

We analyzed data from 237 SAR/anaphylaxis in 237 children. Trigger at allergen component level was defined for every episode. The most common triggers of SAR/anaphylaxis were seeds (50.6%), among them, the storage proteins. Anaphylaxis triggered by Ana o 3, 2S albumin from cashews (aOR = 15.0; 95% CI: 3.27 to 73.47); Tri a 19 from wheat (aOR = 9.93; 95% CI: 1.73 to 56.97); and Cor a 9 from hazelnut (aOR = 6.53; 95% CI: 1.16 to 36.72) had the worst clinical presentation including cardiovascular and severe respiratory symptoms (grade IV-V vs I-III in Cox scale). Thirteen out of 237 (5.5%) SAR/anaphylaxis patients were triggered by Ana o 3. Almost 82% of patients with severe Ana o 3 anaphylaxis were sensitized only to this component and had no concomitant food sensitization.

CONCLUSION

Monosensitization to Ana o 3 is, irrespective of other parameters, connected with high risk of severe anaphylaxis.

Molecular Diagnosis of Allergy: The Pediatric Perspective

In times of "Precision Medicine" it is fundamental to identify the individual disease phenotype in order to provide an individualized therapy for every patient. This concept is also becoming increasingly important for the treatment of allergic diseases. Thanks to the biological engineering of recombinant and native allergens for the assessment of allergen-specific IgE antibodies, it is now possible to easily obtain the individual sensitization profile of a patient. This allows the allergist to precisely identify the primary elicitor of an IgE response and, based on this knowledge, to choose the best treatment option. Several studies have observed the longitudinal evolution of sensitization profiles and identified a phenomenon termed "molecular spreading," which describes a broadening of the recognized allergen spectrum from a source over time. Additionally, the identification of marker proteins, which can trigger an IgE response or correlate with an increased risk for certain clinical symptoms, helps to establish an individual risk profile. This information may not only affect the decision-making concerning immunotherapy, but also opens up avenues for future investigations with regard to prevention strategies. We provide here an overview on the role of individual sensitization patterns and their predictive value.

Determination of the clinical egg allergy phenotypes using component-resolved diagnostics

IgE-mediated egg allergy presents as one of the most common food allergies in children and is a food which is widely consumed all over the world. Measurement of egg white-specific IgE levels has been shown to be a poor predictor of clinical phenotypes of egg allergy, including to raw egg white, but particularly to baked or cooked egg. Egg white and yolk contain more than 20 different glycoproteins, including ovomucoid, ovalbumin, ovotransferrin, alpha-livetin, and the newly identified Gal d 6. Recent developments in component-resolved diagnostic technology, including microarrays, have enabled us to improve the way in which we diagnose food allergy. This technology allows us to measure specific IgE antibodies to individual egg allergens which have been highly purified. Characterization of the major egg allergens could help profile the relevant binding epitopes to each region and may also help diagnose the different clinical phenotypes of egg allergy.

Gly m 5/Gly m 8 fusion component as a potential novel candidate molecule for diagnosing soya bean allergy in Japanese children

BACKGROUND

Soya bean is a major food allergen in children. Component-resolved diagnostics has improved the accuracy of diagnosing immunoglobulin E (IgE)-mediated food allergies.

OBJECTIVE

We aimed to develop a novel component for the diagnosis of soya bean allergy using recombinant technology.

METHODS

Japanese paediatric patients with suspected soya bean allergy (n = 91) were included, and symptomatic (n = 40) and asymptomatic (n = 51) cases were divided through oral food challenge testing. Specific IgE (sIgE) antibodies to each recombinant allergen component were analysed by enzyme-linked immunosorbent assay, and the diagnostic performances of the components were assessed by area under the receiver operating characteristic curves (AUC).

RESULTS

Among the recombinant components, sIgE antibody levels to Gly m 8 showed the highest AUC (0.706). A combination of Gly m 8 and α' subunit of Gly m 5, improved the diagnostic performance of the single components. Moreover, the N-terminal extension region of α' subunit of Gly m 5, which has low cross-reactivity among the vicilins, showed higher diagnostic performance (AUC 0.695) than the full-length α' subunit of Gly m 5 (AUC 0.613). Based on these findings, we developed a fusion protein of Gly m 8 plus the extension region of α' subunit of Gly m 5; this fusion protein was very efficient for diagnosing soya bean allergy (AUC 0.801).

CONCLUSION

A fusion protein of Gly m 8 and the extension region of α' subunit of Gly m 5 could potentially diagnose soya bean allergy in paediatric patients. Fusion proteins may be useful for producing novel allergen components with improved diagnostic value.

Molecular Aspects of Allergen-Specific Immunotherapy in Patients with Seasonal Allergic Rhinitis

A systematic review and narrative synthesis of publications was undertaken to analyze the role of component-resolved diagnosis technology in identifying polysensitization for the provision of allergen-specific immunotherapy to patients with seasonal allergic rhinitis. A search of publications was carried out in electronic databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The search helped to identify 568 publications, 12 of which were included in this review. Overall, 3302 patients were enrolled. The major finding was that component-resolved diagnostics change the choice of relevant allergens for allergen-specific immunotherapy in at least 50% of cases. Sensitization to allergen components differs with age, type of disease, and overall disease duration. Patients who had both bronchial asthma and allergic rhinitis were sensitized to a larger number of allergens than patients who had bronchial asthma alone.

CytoBas: Precision component-resolved diagnostics for allergy using flow cytometric staining of basophils with recombinant allergen tetramers

BACKGROUND

Diagnostic tests for allergy rely on detecting allergen-specific IgE. Component-resolved diagnostics incorporate multiple defined allergen components to improve the quality of diagnosis and patient care.

OBJECTIVE

To develop a new approach for determining sensitization to specific allergen components that utilizes fluorescent protein tetramers for direct staining of IgE on blood basophils by flow cytometry.

METHODS

Recombinant forms of Lol p 1 and Lol p 5 proteins from ryegrass pollen (RGP) and Api m 1 from honeybee venom (BV) were produced, biotinylated, and tetramerized with streptavidin-fluorochrome conjugates. Blood samples from 50 RGP-allergic, 41 BV-allergic, and 26 controls were incubated with fluorescent protein tetramers for flow cytometric evaluation of basophil allergen binding and activation.

RESULTS

Allergen tetramers bound to and activated basophils from relevant allergic patients but not controls. Direct fluorescence staining of Api m 1 and Lol p 1 tetramers had greater positive predictive values than basophil activation for BV and RGP allergy, respectively, as defined with receiver operator characteristics (ROC) curves. Staining intensities of allergen tetramers correlated with allergen-specific IgE levels in serum. Inclusion of multiple allergens coupled with distinct fluorochromes in a single-tube assay enabled rapid detection of sensitization to both Lol p 1 and Lol p 5 in RGP-allergic patients and discriminated between controls, BV-allergic, and RGP-allergic patients.

CONCLUSION

Our novel flow cytometric assay, termed CytoBas, enables rapid and reliable detection of clinically relevant allergic sensitization. The intensity of fluorescent allergen tetramer staining of basophils has a high positive predictive value for disease, and the assay can be multiplexed for a component-resolved and differential diagnostic test for allergy.