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.

Tolerance to heated egg in egg allergy: Explanations and implications for prevention and treatment

Hen's egg allergy is the second most frequent food allergy found in children. Allergic symptoms can be caused by raw or heated egg, but a majority of egg-allergic children can tolerate hard-boiled or baked egg. Understanding the reasons for the tolerance towards heated egg provides clues about the molecular mechanisms involved in egg allergy, and the differential allergenicity of heated and baked egg might be exploited to prevent or treat egg allergy. In this review, we therefore discuss (i) why some patients are able to tolerate heated egg; by highlighting the structural changes of egg white (EW) proteins upon heating and their impact on immunoreactivity, as well as patient characteristics, and (ii) to what extent heated or baked EW might be useful for primary prevention strategies or oral immunotherapy. We describe that the level of immunoreactivity towards EW helps to discriminate patients tolerant or reactive to heated or baked egg. Furthermore, the use of heated or baked egg seems effective in primary prevention strategies and might limit adverse reactions. Oral immunotherapy is a promising treatment strategy, but it can sometimes cause significant adverse events. The use of heated or baked egg might limit these, but current literature is insufficient to conclude about its efficacy.

Psychological needs and support among patients and families undergoing food oral immunotherapy

BACKGROUND

Oral immunotherapy (OIT) is a promising treatment for food allergy (FA) however it is a challenging process for patients and parents. Induction can generate stress and anxiety. This may in turn affect their motivation and ability to cope with OIT challenges.

OBJECTIVE

This study aimed to investigate psychological needs and support to patients/parents undergoing food OIT assessing participants' main characteristics, reasons for seeking psychological support, OIT phase and related psychological difficulties, type and timing of treatments and patients' perception of the effectiveness of the intervention.

METHODS

This is an observational, retrospective study. 50 psychological interventions required for OIT related problems were selected consecutively in a Referral Centre in North-Eastern Italy. All patients had a medical diagnosis of FA and were undergoing OIT or had just discontinued it. Data were collected from hospital records. A descriptive statistical analysis was performed.

RESULTS

66% of patients asked for psychological support for the initial phase (e.g., oral food challenge, first maintenance doses), 20% during the up-dosing phase, 8% during maintenance and 6% after discontinuation. 70% of treatments were required mainly because of emotional problems including dysfunctional anxiety and mood disorders, increased distress and excessive worry and/or fear related to OIT; 20% because of difficulties in managing OIT; 10% because of eating difficulties; 50% of patients reported recent anaphylaxis. All patients reported improvement and felt the psychological intervention was helpful.

CONCLUSION

It is recommended to evaluate the psychological needs in profiling patients and families suitable to OIT and offer specific psychological support when needed.

Integration of in vitro allergy test results and ratio analysis for the diagnosis and treatment of allergic patients (INTEGRA)

The introduction of molecular diagnosis into routine clinical practice has substantially improved the diagnosis and management of allergic patients by allowing clinicians to precisely identify the allergenic molecule responsible for immunoglobulin E (IgE)-mediated allergies. However, it can be challenging to accurately interpret the results of molecular assays, partly due to the limited evidence base. In this context, a panel of experts with extensive experience in interpreting in vitro measures of total and serum specific IgE reviewed the available scientific evidence. After this review, the panel selected a series of representative case studies to demonstrate how determination of specific and total IgE values and the relationship between them (ratio analysis) can add value to the diagnostic process by more precisely defining the patient's sensitization profile. Finally, the experts developed a series of recommendations on the clinical application of ratio analysis to optimize and complement the classical approach to allergy diagnosis.

Array-based measurements of aero-allergen-specific IgE correlate with skin-prick test reactivity in asthma regardless of specific IgG4 or total IgE measurements

Skin prick testing (SPT) and measurement of serum allergen-specific IgE (sIgE) are used to investigate asthma and other allergic conditions. Measurement of serum total IgE (tIgE) and allergen-specific IgG4 (sIgG4) may also be useful. The aim was to ascertain the correlation between these serological parameters and SPT. Sera from 60 suspected asthmatic patients and 18 healthy controls were assayed for sIgE and sIgG4 reactivity against a panel of 70 SPT allergen preparations, and for tIgE. The patients were also assessed by skin prick tests for reactivity to cat, dog, house dust mite and grass allergens. Over 50% of the patients had tIgE levels above the 75th percentile of the controls. 58% of patients and 39% of controls showed sIgE reactivity to ≥1 allergen. The mean number of allergens detected by sIgE was 3.1 in suspected asthma patients and 0.9 in controls. 58% of patients and 50% of controls showed sIgG4 reactivity to ≥1 allergen. The mean number of allergens detected by sIgG4 was 2.5 in patients and 1.7 in controls. For the patients, a strong correlation was observed between clinical SPT reactivity and serum sIgE levels to cat, dog, house dust mite (HDM) and grass allergens. SPT correlations using sIgE/sIgG4 or sIgE/tIgE ratios were not markedly higher. The measurement of serum sIgE by microarray using SPT allergen preparations showed good correlation with clinical SPT reactivity to cat, dog, HDM and grass allergens. This concordance was not improved by measuring tIgE or sIgG4.

Biomarkers of diagnosis and resolution of food allergy

Food allergy is increasing in prevalence, affecting up to 10% of children in developed countries. Food allergy can significantly affect the quality of life and well-being of patients and their families; therefore, an accurate diagnosis is of extreme importance. Some food allergies can spontaneously resolve in 50%-60% of cow's milk and egg-allergic, 20% of peanut-allergic and 9% of tree nut-allergic children by school age. For that reason, food-allergic status should be monitored over time to determine when to reintroduce the food back into the child's diet. The gold-standard to confirm the diagnosis and the resolution of food allergy is an oral food challenge; however, this involves the risk of causing an acute-allergic reaction and requires clinical experience and resources to treat allergic reactions of any degree of severity. In the clinical setting, biomarkers have been used and validated to enable an accurate diagnosis when combined with the clinical history, deferring the oral food challenge, whenever possible. In this review, we cover the tools available to support the diagnosis of food allergies and to predict food allergy resolution over time. We review the latest evidence on different testing modalities and how effective they are in guiding clinical decision making in practice. We also evaluate predictive test cut-offs for the more common food allergens to try and provide guidance on when challenges might be most successful in determining oral tolerance in children.

Food allergy: an updated review on pathogenesis, diagnosis, prevention and management

Food allergy (FA) is an adverse immunologic response triggered by normally innocuous food protein antigens.  FA can be broadly classified into those that are IgE mediated, those that are mediated by both IgE-dependent and IgE-independent pathways (mixed), and those that are not IgE mediated  Immunoglobulin E. (IgE)-mediated reaction is characterized by rapid onset of symptoms involving respiratory, gastrointestinal, dermatologic and cardiovascular systems; mixed and non-IgE-mediated has a longer onset and manifests primary in the gastrointestinal tract and skin. The diagnosis of food allergy is based on clinical history, diagnostic testing (skin prick test and allergen-specific IgE levels in the serum), elimination diet and, oral food challenge. In recent years the diagnosis and treatment of pediatric FA have notably improved. In the diagnostic pathway of FA an important recent innovation is the CRD introduction.  This resulted in the possibility of improving diagnostic accuracy through FA prediction severity and prognosis and thereby decreasing the OCF necessity. Recent studies emphasize the possibility of preventing FA through early introduction of food (peanuts and egg) to high-risk infants. FA management is based on avoidance of offending food and prompt treatment of allergic reaction. Currently under study are recently developed treatment approaches for FA management including specific OIT.

Component-Resolved Diagnostic Study of Egg Allergy in Northern Chinese Children

BACKGROUND

Egg component-specific IgE can be useful to evaluate and diagnose egg allergy, but their prevalence and clinical significance remain unclear in the local population. Previous studies have led to contradictory results regarding the value of specific IgG and specific IgG4 in sensitization.

OBJECTIVE

We aimed to determine the level of specific IgE, IgG, and IgG4 antibodies to the major egg allergens in egg-allergic children.

METHODS

Children from 6 months to 10 years of age were recruited. Egg allergy was confirmed by either a strong clinical history or an increased egg white-sIgE level. Other allergies were diagnosed by reactivity to other allergens but without egg-related symptoms and history. The serum sIgE, sIgG, and sIgG4 levels to major egg allergenic components (Gal d 1, Gal d 2, Gal d 3, Gal d 4, and Gal d 5), sIgE level to egg white, and tIgE level were determined by light-initiated chemiluminescent assay (LICA), ELISA, or ImmunoCAP.

RESULTS

Egg-allergic children had significantly higher levels of sIgE, sIgG, and sIgG4 to egg components than nonallergic children. Gal d 2 was the predominant allergen, and Gal d 2 sIgE level correlated with the egg white-sIgE level. Ratios of sIgE/sIgG4 to egg components were highest before 1 year of age and dropped gradually in the first decade of life.

CONCLUSION

Patterns of sIgE to egg components could distinguish different forms of egg allergy. Ratios of sIgE/sIgG4 could be useful in predicting tolerance in egg-sensitive subjects, but this needs further evaluation and investigation using more accurate models.

Novel Bead-Based Epitope Assay is a sensitive and reliable tool for profiling epitope-specific antibody repertoire in food allergy

Identification of allergenic IgE epitopes is instrumental for the development of novel diagnostic and prognostic methods in food allergy. In this work, we present the quantification and validation of a Bead-Based Epitope Assay (BBEA) that through multiplexing of epitopes and multiple sample processing enables completion of large experiments in a short period of time, using minimal quantities of patients’ blood. Peptides that are uniquely coupled to beads are incubated with serum or plasma samples, and after a secondary fluorophore-labeled antibody is added, the level of fluorescence is quantified with a Luminex reader. The signal is then normalized and converted to epitope-specific antibody binding values. We show that the effect of technical artifacts, i.e. well position or reading order, is minimal; and batch effects - different individual microplate runs - can be easily estimated and eliminated from the data. Epitope-specific antibody binding quantified with BBEA is highly reliable, reproducible and has greater sensitivity of epitope detection compared to peptide microarrays. IgE directed at allergenic epitopes is a sensitive biomarker of food allergy and can be used to predict allergy severity and phenotypes; and quantification of the relationship between epitope-specific IgE and IgG4 can further improve our understanding of the immune mechanisms behind allergic sensitization.

Oral Food Challenge

Oral food challenge (OFC) is the gold standard for diagnosis of IgE-mediated and non-IgE mediated food allergy. It is usually conducted to make diagnosis, to monitor for resolution of a food allergy, or to identify the threshold of responsiveness. Clinical history and lab tests have poor diagnostic accuracy and they are not sufficient to make a strict diagnosis of food allergy. Higher concentrations of food-specific IgE or larger allergy prick skin test wheal sizes correlate with an increased likelihood of a reaction upon ingestion. Several cut-off values, to make a diagnosis of some food allergies (e.g., milk, egg, peanut, etc.) without performing an OFC, have been suggested, but their use is still debated. The oral food challenge should be carried out by experienced physicians in a proper environment equipped for emergency, in order to carefully assess symptoms and signs and correctly manage any possible allergic reaction. This review does not intend to analyse comprehensively all the issues related to the diagnosis of food allergies, but to summarize some practical information on the OFC procedure, as reported in a recent issue by The Expert Review of Food Allergy Committee of Italian Society of Pediatric Allergy and Immunology (SIAIP).

Component-Resolved Diagnosis in Food Allergies

Component-resolved diagnostics (CRD) in food allergies is an approach utilized to characterize the molecular components of each allergen involved in a specific IgE (sIgE)-mediated response. In the clinical practice, CRD can improve diagnostic accuracy and assist the physician in many aspects of the allergy work-up. CRD allows for discriminatory co-sensitization versus cross-sensitization phenomena and can be useful to stratify the clinical risk associated with a specific sensitization pattern, in addition to the oral food challenge (OFC). Despite this, there are still some unmet needs, such as the risk of over-prescribing unnecessary elimination diets and adrenaline auto-injectors. Moreover, up until now, none of the identified sIgE cutoff have shown a specificity and sensitivity profile as accurate as the OFC, which is the gold standard in diagnosing food allergies. In light of this, the aim of this review is to summarize the most relevant concepts in the field of CRD in food allergy and to provide a practical approach useful in clinical practice.

The Impact of Baked Egg and Baked Milk Diets on IgE- and Non-IgE-Mediated Allergy

Baked milk (BM) and baked egg (BE) diets are increasingly used in the management of milk and egg allergy, rather than avoidance. Children with tolerance versus reactivity to BM and BE may have smaller skin prick test and lower specific IgE, and BM-tolerant children have less basophil reactivity and more peripheral T regulatory cells. However, most milk- and egg-allergic children tolerate BM and BE and an individual's reactivity is unpredictable. Non-reactivity is due to conformational changes in the allergens. Significant differences in the published advice about methods of introduction exist from graded introduction at home to a medically supervised full dose. These approaches carry different risks and may have different immunological effects. Reactivity to BM is a predictor of a severe milk allergy. Therefore, medical supervision for BM and BE introduction is prudent. The baked diet allows dietary liberation. Most, but not all, BM- and BE-tolerant children continue eating the baked foods. The prognosis of children who can eat BM and BE is favorable with likely resolution of their allergy over the next few years. Murine models of BE diets demonstrate that heated egg can impart clinical protection against anaphylaxis and cause immune changes. Most observational human studies of BM and BE diets demonstrate clinical resolution of allergy and favorable immune changes versus regular care controls. However, the one randomized controlled trial for the BE diet in BE-tolerant children did not support an immune-modifying effect of the BE diet. Another study of BE immunotherapy is expected to be completed in 2018. There is currently no evidence for prevention of allergy with the baked diets. There may be a future role for BM and BE in liberating the diets of individuals with non-IgE-mediated allergy given recent studies that a subset of these patients can consume BM without a clinical reaction.

A light-initiated chemiluminescent assay for rapid quantitation of allergen-specific IgG4 in clinical samples

BACKGROUND

An increase in allergen-specific IgG₄ (sIgG₄), which serves as a blocking antibody, is associated with acquisition of immune tolerance after immunotherapy. In this study, we developed a rapid, sensitive, and homogeneous immunoassay based on the light-initiated chemiluminescent assay (LICA) technology for quantifying allergen sIgG₄ in serum samples.

METHODS

Allergen sIgG₄ was measured in vitro by incubating the sample with biotinylated allergens and chemiluminescent beads coated with anti-human IgG₄ antibody, followed by the addition of streptavidin-coated sensitizer beads. Multiple tests were performed to optimize the working conditions of the LICA and evaluate its performance.

RESULTS

We established the optimal concentration of biotinylated allergens (250 ng/mL), the optimal dilution range (1:8 for Gal d 1, Gal d 2 sIgG₄ and 1:4 for Gal d 3, Gal d 4 sIgG₄), and the optimal incubation time (20 min for Gal d 1, Gal d 2 sIgG₄ and 40 min for Gal d 3, Gal d 4 sIgG₄). The lower limit of quantification (LLOQ) was 0.261 ng/mL. The coefficient variation (CV) of the LICA was <10%. The assay was unaffected by general interfering substances at physiological concentrations. It exhibited excellent accuracy to detect allergen-sIgG₄ in human serum. Additionally, we demonstrated that the levels of Gal d 1, Gal d 2, and Gal d 3-sIgG₄ were significantly higher in the egg allergy group (p < .05), but no differences were found between the groups for Gal d 4-sIgG₄.

CONCLUSIONS

The LICA demonstrated satisfactory performance and can be used for quantifying allergen sIgG₄ in clinical practice.

Clinical and immunological profile of children aged 5-9 years with persistent egg allergy before oral immunotherapy with egg. A multicenter, randomized controlled trial of the Spanish Society of Pediatric Allergy, Asthma and Clinical Immunology (SEICAP)

BACKGROUND

In children with egg protein allergy (EA), the probability of overcoming the allergy decreases with age, and the possibility of suffering severe adverse reactions as a consequence of dietetic transgressions results in worsened quality of life. One treatment option in such cases is oral immunotherapy (OIT) with foods.

METHODS

We present a cohort of children with EA scheduled for OIT with pasteurized raw egg white, describing their clinical and allergic characteristics before the start of OIT.

RESULTS

The median age was six years, and 93% of the patients also suffered other allergies (58% asthma and 38.6% allergy to more than two food groups). In the last year, 14.8% had suffered a severe reaction due to dietetic transgression with egg. The median IgE specific of egg white titer was 38.5kU/l. A double-blind placebo-controlled food challenge with cooked egg white was performed, and if the test proved positive, it was repeated with pasteurized raw egg white. The mean symptoms-provoking dose was 1.26g and 0.55g for cooked egg white and raw egg white, respectively. An IgE specific of ovomucoid titer of <2.045kU/l differentiated those patients that tolerated cooked egg white.

CONCLUSIONS

OIT with egg is regarded as an option in patients with persistent egg allergy. In the previous challenge test, an IgE specific of ovomucoid titer of <2.045kU/l differentiates those patients that tolerate cooked egg white.

Patterns of sensitization to inhalant and food allergens among pediatric patients from the Moscow region (Russian Federation)

The immunological profiles of human specific IgE (sIgE) and specific IgG4 (sIgG4) vary by genetic predisposition, living conditions in different geographical locations and patient’s age. The aim of our study was to analyze sIgE and sIgG4 patterns and their age-dependent changes in patients from the Moscow region. For identifying sIgE and sIgG4 profiles the blood samples from 513 patients aged 6 months to 17 years who were showing symptoms of allergic diseases were analyzed using microarrays containing 31 allergens. The highest sIgE prevalence was observed for birch pollen (32%) among pollen allergens, cat dander (24%) among indoor allergens, and egg whites (21%) among food allergens. The most common sIgG4 response was developed toward egg whites (80% of patients). Age-related elevation was identified for patients with increased sIgE to pollen allergens and indoor allergens (cat or dog dander and house dust mites). For each allergen, the proportion of cases with significant levels of sIgG4 appeared to increase with patients’ age. The data on allergen-specific sIgE and sIgG4 prevalence show both general trends and some local special aspects that are indicative for the Moscow region. This information should be useful in terms of epidemiology of allergic diseases.

Making the Most of In Vitro Tests to Diagnose Food Allergy

Various in vitro tests assess different aspects of the underlying immune mechanism of IgE-mediated food allergy. Some can be used for diagnostic purposes; specific IgE to allergen extracts is widely available; specific IgE to allergen components is used in most specialist centers, and the basophil activation test is becoming increasingly used clinically. IgE to allergen peptides, T-cell assays, allergen-specific/total IgE ratios, and allergen-specific IgG4/IgE ratios are currently reserved for research. Different factors can modulate the likelihood of IgE-mediated food allergy of a given allergy test result, namely, the patients' age, ethnicity, previous allergic reaction to the identified food, concomitant atopic conditions, and geographical location, and need to be taken into account when interpreting the allergy test results in the clinic. The importance of the specific food, the clinical resources available, and patient preferences are additional aspects that need to be considered when deciding whether an oral food challenge is required to reach an accurate diagnosis of IgE-mediated food allergy.

Development of a microarray-based method for allergen-specific IgE and IgG4 detection

Background

sIgE and sIgG4 detection is necessary for more accurate and effective type I hypersensitivity diagnostics and the estimation of disease development. Typically, the analyses of these antibodies are performed separately with the help of various specialized systems. The aim of this study was to develop a microarray-based method for the simultaneous quantitative detection of sIgE and sIgG4 to the most common allergens in a single sample.

Methods

A quantitative method for the simultaneous detection of sIgE and sIgG4 was developed based on the technology of hydrogel microchips previously designed at Engelhardt Institute of Molecular Biology, Russian Academy of Sciences (EIMB RAS). The microarray contained gel pads with immobilized allergens and gel pads that allow for the obtaining of sIgE and sIgG4 internal calibration curves for each allergen during the assay. The possibility of the simultaneous detection of sIgE and sIgG4 was developed using the corresponding Cy5 and Cy3 fluorescent dyes.

Results

The multiplex immunoassay method using hydrogel microarrays developed in this study allowed the quantitative detection of sIgE and sIgG4 to 31 allergens from different groups in a single assay. A comparison of the microarray with the existing plate-based analogues (i.e., ALLERG-O-LIQ and sIgG4 ELISA) was performed by analysing 152 blood serum samples and by evaluating Pearson correlation coefficients, ROC analysis, and Passing-Bablok linear regression results.

Conclusion

The implementation of this method in allergy diagnostics will provide the possibility of simultaneously performing primary patient screening and obtaining additional information concerning the severity of the allergies and the choice of an appropriate therapy.

Developments in the field of allergy in 2014 through the eyes of Clinical and Experimental Allergy

The pathogenesis of asthma continues to be a major topic of interest to our authors with reviews and original papers on the role of viruses, mechanisms of inflammation, biomarkers, and phenotypes of asthma being major topics. A number of papers described new treatments for asthma focusing on blocking the Th2 response reflecting the fact that two decades of work in this area is finally bearing fruit. The pathogenesis of chronic rhinosinusitis is a growing area of interest, but there has been less on the genetics of airways disease than in previous years possibly reflecting the degree of rigour (and therefore a smaller body of work), with which these sorts of studies are now being undertaken. There continues to be a wide range of papers dealing with mechanisms of allergic disease ranging from clinical-based studies to basic research and the use of in vivo animal models especially mice. As before, mechanisms and new approaches to immunotherapy are common themes. Several were published in the allergens section investigating modification of allergens to increase their effectiveness and reduce the risk of adverse events. Risk factors for allergic disease was a common theme in the epidemiology section and food allergy a common theme in clinical allergy with papers on the development of protocols to induce tolerance and attempts to find biomarkers to distinguish sensitization from allergic disease. This was another exciting year for the editors, and we hope the readers of the journal.

Matrix effect on baked egg tolerance in children with IgE-mediated hen's egg allergy

BACKGROUND

Children with IgE-mediated hen's egg allergy (IgE-HEA) often tolerate baked egg within a wheat matrix.

OBJECTIVE

To evaluate the influence of wheat matrix and the effects of little standardized cooking procedures on baked egg tolerance.

METHODS

Fifty-four children with IgE-HEA were enrolled. They underwent prick-by-prick (PbP) tests and open oral food challenges (OFC) performed with baked HE within a wheat matrix (a home-made cake, locally called ciambellone), baked HE without a wheat matrix (in the form of an omelet, locally named frittata) and boiled HE. Three months after passing ciambellone OFC, parents were asked to answer a survey.

RESULTS

About 88% of children tolerated ciambellone, 74% frittata, and 56% boiled HE. Negative predictive value of PbP performed with ciambellone, frittata, and boiled HE was 100%. No IgE-mediated adverse reactions were detected at follow-up carried out by the survey.

CONCLUSIONS

Wheat matrix seemed to be relevant only in few cases. If our results will be confirmed by larger studies, a negative PbP with ciambellone, frittata, or boiled HE will allow patients with IgE-HEA to eat these foods without undergoing OFC. Moreover, our study showed that very strict standardized cooking procedures do not seem to be essential, to guarantee tolerance toward baked HE.

Longitudinal profiles of serum specific IgE and IgG4 to Dermatophagoides pteronyssinus allergen and its major components during allergen immunotherapy in a cohort of southern Chinese children

Longitudinal data on serum specific sIgE and sIgG4 to allergen component of Dermatophagoides pteronyssinus (Der p) during allergen immunotherapy (AIT) are limited in Chinese populations. We serially followed up serum sIgE and sIgG4 to Der p and its components (Der p 1 and 2) in 51 Der p-sensitized children receiving guideline-based medications alone and additional 36-month AIT. The the Der p 1 and Der p 2 sIgE levels were elevated at 6 months and progressively declined from 12 months; the sIgG4 levels for Der p, Der p 1 and Der p 2 were increasing during the first year and reached a plateau thereafter; the sIgE/sIgG4 ratios for Der p 1 and Der p 2 decreased continuously from 6 through 24 months of AIT. Subgroup analysis showed that younger children (≤8years) experienced a greater increase in sIgG4 levels for Der p, Der p 1 and Der p 2 during AIT compared with older children (9-16 years). In summary, sIgE and sIgG4 to Der p 1 and Der p 2 may be more useful than those to Der p in reflecting the change in immunological reactivity during AIT. Earlier delivery of AIT may yield greater increase in sIgG4 after 36-month treatment than given later in life.

Successful immunotherapy induces previously unidentified allergen-specific CD4+ T-cell subsets

Allergen immunotherapy can desensitize even subjects with potentially lethal allergies, but the changes induced in T cells that underpin successful immunotherapy remain poorly understood. In a cohort of peanut-allergic participants, we used allergen-specific T-cell sorting and single-cell gene expression to trace the transcriptional "roadmap" of individual CD4+ T cells throughout immunotherapy. We found that successful immunotherapy induces allergen-specific CD4+ T cells to expand and shift toward an "anergic" Th2 T-cell phenotype largely absent in both pretreatment participants and healthy controls. These findings show that sustained success, even after immunotherapy is withdrawn, is associated with the induction, expansion, and maintenance of immunotherapy-specific memory and naive T-cell phenotypes as early as 3 mo into immunotherapy. These results suggest an approach for immune monitoring participants undergoing immunotherapy to predict the success of future treatment and could have implications for immunotherapy targets in other diseases like cancer, autoimmune disease, and transplantation.

Is it possible to make a diagnosis of raw, heated, and baked egg allergy in children using cutoffs? A systematic review

The diagnosis of IgE-mediated egg allergy lies both on a compatible clinical history and on the results of skin prick tests (SPTs) and IgEs levels. Both tests have good sensitivity but low specificity. For this reason, oral food challenge (OFC) is the ultimate gold standard for the diagnosis. The aim of this study was to systematically review the literature in order to identify, analyze, and synthesize the predictive value of SPT and specific IgEs both to egg white and to main egg allergens and to review the cutoffs suggested in the literature. A total of 37 articles were included in this systematic review. Studies were grouped according to the degree of cooking of the egg used for OFC, age, and type of allergen used to perform the allergy workup. In children <2 years, raw egg allergy seems very likely when SPTs with egg white extract are ≥4 mm or specific IgEs are ≥1.7 kUA /l. In children ≥2 years, OFC could be avoided when SPTs with egg white extract are ≥10 mm or prick by prick with egg white is ≥14 mm or specific IgE is ≥7.3 kUA /l. Likewise, heated egg allergy can be diagnosed if SPTs with egg white extract are >5 and >11 mm in children <2 and ≥2 years, respectively. Further and better-designed studies are needed to determine the remaining diagnostic cutoff of specific IgE and SPT for heated and baked egg allergy.

High IgE levels to α-lactalbumin, β-lactoglobulin and casein predict less successful cow's milk oral immunotherapy

BACKGROUND

A new treatment option for persistent cow's milk allergy (CMA) is oral immunotherapy (OIT). Not all patients develop tolerance during therapy, and markers to identify those who will benefit from it are needed. The objective was to study the IgE and IgG4 antibody profiles to milk and milk proteins before and after OIT in relation to clinical outcome.

METHODS

Seventy-six children (5-17 years) with challenge-verified CMA were subjected to a 6-month OIT protocol. The treatment aimed at reaching a maintenance dose of 200 ml CM (high dose = HD). Those who did not reach target were analysed as a low-dose (LD) group. Sera were characterized before and after OIT regarding serum levels of IgE and IgG4 to milk and five milk allergen components evaluated together with clinical CMA symptoms and outcome of OIT.

RESULTS

Fifty-five (72%) patients reached the maintenance dose (HD) during therapy. High specific IgE levels towards the milk allergens α-lactalbumin (P = 0.048), β-lactoglobulin (P = 0.006) and casein (P = 0.015) before OIT start were associated with lower maintenance dose reached. Patients who developed desensitization had a larger increase in IgG4 levels to α-lactalbumin (P = 0.034), β-lactoglobulin (P = 0.010), casein (P = 0.047) and lactoferrin (P = 0.030) during treatment than those who failed.

CONCLUSIONS

Component-resolved diagnostics before OIT can help to identify children with lower probability of a successful OIT outcome, as high IgE levels to α-lactalbumin, β-lactoglobulin and casein are associated with lower maintenance dose reached. An increase in the IgG4 concentration to milk components during treatment indicated effective desensitization.

Allergenicity of pasteurized whole raw Hen's egg compared with fresh whole raw Hen's egg

BACKGROUND

Oral food challenges for diagnosis and management of egg allergy using fresh egg are common; however, to limit the risk of foodborne infection, many allergy units use pasteurized raw egg. Pasteurization and drying processes have the potential to affect the structure of egg proteins in egg powder and thus the allergenicity when compared to fresh egg. Our aim was to compare the binding of serum IgE from egg-allergic children to in vitro digested and undigested pasteurized whole raw egg powder with unpasteurized fresh whole raw egg.

METHODS

Egg proteins from in vitro digested or undigested pasteurized whole raw egg powder, fresh whole egg, egg white and egg yolk were separated by SDS-PAGE, transferred onto nitrocellulose membrane and incubated overnight with pooled sera from egg-allergic children.

RESULTS

In both the raw egg samples and the pasteurized whole egg powder, protein bands corresponding to known molecular weights of the major egg allergens were present. Pasteurized whole raw egg powder was bound by serum IgE in a similar manner to unpasteurized whole raw egg and was unaffected by in vitro digestion. Serum IgE also bound egg yolk, indicating sensitization to both egg yolk and egg white proteins.

CONCLUSIONS

The main egg allergens are present in pasteurized whole raw egg powder, and serum IgE of egg-allergic children binds to them in a similar pattern to those in fresh whole raw egg. Pasteurized whole raw egg powder is a suitable substitute for raw egg in clinical practice for oral food challenges.

Diagnosis and treatment of pediatric food allergy: an update

The prevalence of pediatric food allergy and anaphylaxis has increased in the last decades, especially in westernized countries where this emerging phenomenon was marked as a "second wave" of the allergic epidemic. Over recent years great advances have been achieved in the field of in vitro allergy testing and component-resolved diagnosis has increasingly entered clinical practice. Testing for allergen components can contribute to a more precise diagnosis by discriminating primary from cross-reactive sensitizations and assessing the risk of severe allergic reactions.The basic concept of the management of food allergy in children is also changing. Avoidance of the offending food is still the mainstay for disease management, especially in primary health care settings, but it severely affects the patients' quality of life without reducing the risk of accidental allergic reactions. There is a growing body of evidence to show that specific oral tolerance induction can represent a promising treatment option for food allergic patients. In parallel, education of food allergic patients and their caregivers as well as physicians about anaphylaxis and its treatment is becoming recognized a fundamental need. International guidelines have recently integrated these new evidences and their broad application all over Europe represents the new challenge for food allergy specialists.

Ovomucoid specific immunoglobulin E as a predictor of tolerance to cooked egg

BACKGROUND

Ovomucoid is the dominant allergen in hen's egg. Although several studies evaluated the utility of ovomucoid specific immunoglobulin E (sIgE) levels in predicting baked (e.g., muffin or cupcake) or raw egg food challenge outcomes, studies that evaluated ovomucoid sIgE as a predictor of cooked egg (e.g., scrambled or hard boiled) challenge outcomes are limited.

OBJECTIVE

To determine the relation of ovomucoid sIgE levels with cooked egg food challenge outcomes.

METHODS

A retrospective review of 44 children who underwent cooked egg food challenge and who had the ovomucoid sIgE level measured.

RESULTS

Thirty-six of 44 children (81.8%) passed cooked egg challenge. The ovomucoid sIgE level predicted cooked egg challenge outcome (passed median, <0.35 kU/L [range, <0.35-0.64 kU/L]; failed median, 0.40 kU/L [range, <0.35-3.13 kU/L]; p = 0.004). Ovomucoid sIgE levels correlated with egg white (EW) sIgE levels (Spearman correlation coefficient, 0.588; p < 0.001). Receiver operating characteristic curve analysis of ovomucoid and EW sIgE demonstrated areas under the curve of 0.711 and 0.766, respectively. No significant difference was observed among those immunologic parameters in their abilities to predict cooked egg challenge outcome (p = 0.559).

CONCLUSION

The ovomucoid sIgE level may be helpful in predicting cooked egg challenge outcomes. However, our study did not support a role for ovomucoid sIgE replacing EW sIgE testing in evaluating egg allergy.

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.