Use of allergen components begins a new era in pediatric allergology

Usefulness of nBos d 4, 5 and nBos d 8 Specific IgE Antibodies in Cow's Milk Allergic Children

PURPOSE

The aim of study was to assess the value of recombinants in predicting the degree of symptoms in children with and without anaphylaxis to cow's milk.

METHODS

The study included 79 children (70±40 months) referred to the Allergological Unit of the Pediatric Department between the years 2008-2012. Group A was composed of 17 children (78±49.6 months) with anaphylaxis after ingestion of milk. Group B was composed of 62 children (73.1±38.6 months) without a history of anaphylaxis, but with less severe symptoms (gastrointestinal and/or skin symptoms). All patients from Group B had a positive open challenge with cow's milk. All patients underwent an allergic evaluation and blood samples were collected to test for IgE to recombinans of milk (nBos d 4, 5, 8).

RESULTS

A significant difference in nBos d 8 emerged with higher levels in Group A (median [IQR]=2.80 [0.91-16.1]) than B (0.65 [0.24-1.67]; P=0.006), whereas there were no statistically significant differences for nBos d 4 and 5. The recombinants' sum was higher in Group A than B: 8.39 [2.72-41.39] vs 3.04 [1.85-7.31] kUA/L; P=0.044. The recombinant nBos d 8 was superior to the other recombinants in identifying children at risk for anaphylaxis, with an area under the curve of 0.718 (95% CI, 0.57-0.86, P=0.006). Considering a cutoff of 1.8 kUA/L, nBos d 8 had the most favorable sensitivity and specificity ratio (sensitivity=0.65, specificity=0.77) with an odd ratio of 6.02 (95% C.I: 1.89-19.23).

CONCLUSIONS

This study suggested 2 phenotypes of allergic children, "high-anaphylaxis-risk" and "milder-risk". These types can be differentiated through measuring the level of IgE to nBos d 8.

Component-resolved diagnostics for the evaluation of peanut allergy in a low-prevalence area

BACKGROUND

Major allergenic components of peanut from distinct geographical regions are widely dispersed. Most of the diagnostic studies are from countries with a high prevalence. There have been only few reports of allergen component sensitizations from countries with a low prevalence of peanut allergy. We aimed to investigate roles of component-resolved diagnostic (CRD) to differentiate peanut allergy and peanut tolerance in the Asian population from a country with low prevalence of peanut allergy.

METHODS

Participants with peanut sensitization were enrolled. Clinical reactions were determined. Skin prick test (SPT) and specific IgE (sIgE) to peanut and related allergen components were performed.

RESULTS

Forty subjects with peanut sensitization were included. The mean wheal sizes of SPT and peanut sIgE were not good predictors for differentiating peanut reactions. SIgE to rAra h 2 was more often found in patients with peanut allergy and anaphylaxis. sIgE to rAra h 9 was also more frequent in the peanut-allergic group but not related to severe reactions. In the peanut-tolerant group, despite positive SPT and/or sIgE to peanut, 90% had negative sIgE to rAha h 2 and rAra h 9. Combining rAra h 2 and rAra h 9 resulted in high performance of the test with sensitivity, specificity, positive predictive value, and negative predictive value of 84%, 90%, 0.89, and 0.86, respectively. The ratio between rAra h 2 sIgE to peanut sIgE of 0.6 can be helpful in predicting patients who will develop severe reaction. SIgE to cross-reactive carbohydrate determinants (CCD) was exclusively found in the peanut-tolerant group (33.3% vs. 0%, p = 0.012).

CONCLUSIONS

Our study identifies three allergen components: rAra h 2, rAra h 9, and CCD as important components in the diagnosis of peanut allergy in an Asian country with low prevalence. The ratio between rArah h 2 sIgE to peanut sIgE can be used for predicting patients who will develop anaphylaxis.

A WAO - ARIA - GA²LEN consensus document on molecular-based allergy diagnostics

Molecular-based allergy (MA) diagnostics is an approach used to map the allergen sensitization of a patient at a molecular level, using purified natural or recombinant allergenic molecules (allergen components) instead of allergen extracts. Since its introduction, MA diagnostics has increasingly entered routine care, with currently more than 130 allergenic molecules commercially available for in vitro specific IgE (sIgE) testing.

MA diagnostics allows for an increased accuracy in allergy diagnosis and prognosis and plays an important role in three key aspects of allergy diagnosis: (1) resolving genuine versus cross-reactive sensitization in poly-sensitized patients, thereby improving the understanding of triggering allergens; (2) assessing, in selected cases, the risk of severe, systemic versus mild, local reactions in food allergy, thereby reducing unnecessary anxiety for the patient and the need for food challenge testing; and (3) identifying patients and triggering allergens for specific immunotherapy (SIT).

Singleplex and multiplex measurement platforms are available for MA diagnostics. The Immuno-Solid phase Allergen Chip (ISAC) is the most comprehensive platform currently available, which involves a biochip technology to measure sIgE antibodies against more than one hundred allergenic molecules in a single assay. As the field of MA diagnostics advances, future work needs to focus on large-scale, population-based studies involving practical applications, elucidation and expansion of additional allergenic molecules, and support for appropriate test interpretation. With the rapidly expanding evidence-base for MA diagnosis, there is a need for allergists to keep abreast of the latest information. The aim of this consensus document is to provide a practical guide for the indications, determination, and interpretation of MA diagnostics for clinicians trained in allergology.

Patterns of sensitization to inhalant and food allergens - findings from the German Health Interview and Examination Survey for Children and Adolescents

BACKGROUND

To assess the prevalence of allergic sensitization and to analyze patterns of sensitization to common inhalant and food allergens in a nationwide representative sample of children and adolescents in Germany.

METHODS

Data were collected from 2003 to 2006 within the KiGGS, the national Health Interview and Examination Survey covering a representative sample of 17,641 children and adolescents in Germany. Immunoglobulin E (IgE) antibodies to 20 specific allergens (11 inhalant and 9 food allergens) were quantitatively measured in a subsample of 12,988 KiGGS participants aged 3-17 years using the ImmunoCAP system. Serum concentrations ≥0.35 kU/l indicate sensitized participants. An exploratory factor analysis was performed in order to identify sensitization patterns.

RESULTS

Sensitization to at least 1 of the 20 tested allergens was detected in 40.2% [95% confidence interval (CI) 39.0-41.4] of the participants. The highest sensitization prevalences were found for pollen from Timothy grass (22.7%; 21.5-23.9) and rye (21.2%; 20.0-22.4). Sensitization was more prevalent in boys than in girls and prevalence increased generally with increasing age. We identified seven sensitization groups, namely (in descending order of magnitude) 'Timothy grass/rye', 'house-dust mites', 'food/mugwort', 'birch/apple', 'animals', 'cow's milk/egg white' and 'moulds'.

CONCLUSIONS

Allergic sensitization is common in German children and adolescents. The fact that sensitization potentially leads to clinically relevant allergic diseases stresses the public health relevance of this topic. Whether the grouping reflects the propensity for persons to be sensitized to multiple allergens within a group, or whether it is due to IgE cross-reactivity between different allergens of similar structure is still being discussed.

The natural course of sensitization and allergic diseases from childhood to adulthood

BACKGROUND

Longitudinal prospective population-based birth cohort studies of the natural history of sensitization and allergic diseases from childhood to adulthood are few. The aim of the present prospective study was to investigate the natural course of sensitization and allergic diseases in a random population-based sample of 276 children from a 1-year birth cohort of unselected Danish children followed from birth to 26 years of age.

METHODS

Questionnaire-based interviews, physical examination, skin prick tests, specific IgE testing, and from 10 years also spirometry, were carried out at 1.5, 5, 10, 15 and 26 years of age. Predefined diagnostic criteria were used.

RESULTS

Follow-up rates were high, 193 (70%) attended the 26-year follow-up. The prevalence of current eczema was stable during childhood; 13% (1.5 yrs.), 9.2% (5 yrs.), 10.8% (10 yrs.), and 9.8% (15 yrs.), and 5.7% at 26 yrs. From birth to 26 years the cumulative prevalence of eczema, food allergy, asthma, and rhinoconjunctivitis was 23.5%, 13.8%, 17%, and 27.9% respectively. More than half of the participants had one or more allergic disease in the period between birth and 26 years of age. The rates of sensitization (S-IgE = 0.35 kU/l) were 8%, 23%, 26%, 32%, and 31% at 1.5, 5, 10, 15, and 26 years of age, respectively. Sensitization to food allergens was most prevalent in early infancy, whereas sensitization to inhalant allergens dominated later on.

CONCLUSION

The results support the concept of the allergic march. Allergic diseases are not only occurring in childhood but persist into adulthood.

Comparison of immunoglobulin E measurements on IMMULITE and ImmunoCAP in samples consisting of allergen-specific mouse-human chimeric monoclonal antibodies towards allergen extracts and four recombinant allergens

BACKGROUND

Specific immunoglobulin E (IgE) antibody in vitro tests are performed on enzyme immunoassay systems. Poor agreement among systems has been reported and comparisons have been made exclusively with allergen extracts - not with recombinant allergens. Here we compare the ImmunoCAP and the IMMULITE systems.

METHODS

Ten patient samples with positive IgE toward egg white, birch pollen or cat or dog dander were compared using allergen extracts or the recombinant allergens Gal d 1, Bet v 1, Fel d 1 and Can f 1 with the two assay systems. Comparisons were also performed using four monoclonal mouse-human chimeric IgE antibodies specific for the same allergenic components.

RESULTS

IMMULITE estimated a higher allergen-specific IgE concentration in sera than ImmunoCAP when testing with allergen extracts as well as recombinant allergens. The chimeric antibodies gave an equivalent response in the total IgE and specific IgE (sIgE) with an average ratio of 1.08 (range 0.9-1.3) on ImmunoCAP. In contrast, IMMULITE exhibited sIgE signals that were substantially higher than the summed level of IgE for all four chimeric antibodies (average ratio 2.96 and range 1.7-4.3).

CONCLUSION

Comparison using chimeric antibodies allowed the evaluation of the true performance of the systems. ImmunoCAP measured total IgE and sIgE equally, whereas IMMULITE displayed higher sIgE signals when compared to the summed level of total IgE for all four chimeric antibodies. Results obtained with the two assay systems are not interchangeable by means of mathematical conversion.

Molecular diagnosis of peanut allergy

Peanut allergy prevalence has increased in developed countries over the last few decades in the frame of the allergy epidemics, currently affecting 1-2% of children. While less frequent in developing countries, its prevalence is rising as these countries adopt a more westernized lifestyle. There is no curative treatment for peanut allergy at present so patient management relies on peanut avoidance, which requires an accurate diagnosis. Recent progress in peanut allergy diagnosis was made with the introduction of component resolved diagnosis that allows the assessment of IgE specific to individual peanut allergens. Component-resolved diagnosis needs to be interpreted in the context of clinical data but overall increases the diagnostic accuracy, as described in the typical cases that we present. Novel diagnostic tools have been proposed recently, such as the basophil activation test, mRNA expression and resonance magnetic evaluation of biomarkers.

Diagnosis of food allergies: the impact of oral food challenge testing

A diagnosis of food allergies should be made based on the observation of allergic symptoms following the intake of suspected foods and the presence of allergen-specific IgE antibodies. The oral food challenge (OFC) test is the most reliable clinical procedure for diagnosing food allergies. Specific IgE testing of allergen components as well as classical crude allergen extracts helps to make a more specific diagnosis of food allergies. The Japanese Society of Pediatric Allergy and Clinical Immunology issued the 'Japanese Pediatric Guideline for Food Allergy 2012' to provide information regarding the standardized diagnosis and management of food allergies. This review summarizes recent progress in the diagnosis of food allergies, focusing on the use of specific IgE tests and the OFC procedure in accordance with the Japanese guidelines.

Advances in diagnosing peanut allergy

Peanut allergy is often severe, potentially fatal, usually persistent, and appears to have increased in prevalence. An accurate diagnosis is essential because there is a significant burden on quality of life. The tools available for diagnosis include the medical history, skin prick test (SPT), determination of serum peanut-specific IgE antibodies (PN-IgE), and medically supervised oral food challenges. Numerous studies, almost exclusively in children, have correlated clinical outcomes against SPTs and PN-IgE with informative results. The diagnostic utility of SPT and PN-IgE is maximized by considering the degree of positive result and consideration of the medical history (a priori estimation of risk). Emerging tests that evaluate IgE binding to specific proteins in peanut (component testing) add important additional diagnostic information in specific settings. Studies are increasingly focused on how the results of tests considered in combination (or performed serially) may increase diagnostic accuracy. Here, we review the utility of currently available tests and provide suggestions on how to best use them to accurately predict peanut allergy. Still, the physician-supervised oral food challenge remains the most definitive test available.

Exploring the temporal development of childhood IgE profiles to allergen components

BACKGROUND

Children often develop allergies that may or not persist into adulthood. Although the different allergic symptoms over time have been well documented, the underlying pattern of sensitization to various proteins and subsequent allergy development is unexplored.The aim was to study the sensitization pattern to allergen components over time from infancy to adulthood in a group of infants with heredity for allergic diseases.

METHODS

IgE profiles were monitored in a group of 67 children from 6 months to 18 years using a microarray chip (ImmunoCAP® ISAC) containing 103 allergen components derived from 47 allergen sources. The chip IgE profile was compared with clinical history, skin prick test results and diagnoses (atopic dermatitis, asthma and allergic rhinoconjunctivitis) at each time point for each child.

RESULTS

IgE profiles were unique for each child and showed broad agreement with the results of skin prick tests and doctors' diagnoses. In addition, close examination of the IgE profiles often revealed early indication of subsequent allergies. IgE profiles also facilitated the examination of cross-reactivity contra co-sensitization, thereby greatly enhancing the possibility for managing patients.

CONCLUSION

This explorative description indicates that sensitization pattern to allergen components differs over time as well as among allergic individuals when examined with microarray technology.

Food allergy and anaphylaxis in pediatrics: update 2010-2012

This review highlights the progress made in food allergy (FA) and anaphylaxis research in pediatrics published in the journal Pediatric Allergy and Immunology since 2010. Putative risk factors for FA are as follows: a family history of allergic disease, particularly in the mother, low birth order, season of birth, and severe atopic eczema. Obstetric practices, antibiotic use, and home environment are factors deserving further research. Diagnostic decision levels and component-specific IgE are useful in the diagnosis of FA; however, oral food challenges remain the gold standard and may also be a means to reduce parental anxiety and to improve education. Oral immunotherapy studies show promise in increasing the threshold of reactivity of allergic patients and therefore improving their quality of life. In single-nut-allergic patients, introduction of other nuts allows broadening the diet and thus reducing the psychological impact of allergen avoidance. Nutritional deficiencies are not uncommon in food-allergic children and should be specifically assessed. The prescription of injectable adrenaline is still insufficient and not consistent among practitioners, requiring improved training and implementation of guidelines. Current research into the epidemiology and immunological mechanisms of FA and tolerance will enable us to devise strategies to both prevent and treat food allergies.

2012 Update: World Allergy Organization Guidelines for the assessment and management of anaphylaxis

PURPOSE OF REVIEW

The World Allergy Organization (WAO) Guidelines for the assessment and management of anaphylaxis published in early 2011 provide a global perspective on patient risk factors, triggers, clinical diagnosis, treatment, and prevention of anaphylaxis. In this 2012 Update, subsequently published, clinically relevant research in these areas is reviewed.

RECENT FINDINGS

Patient risk factors and co-factors that amplify anaphylaxis have been documented in prospective studies. The global perspective on the triggers of anaphylaxis has expanded. The clinical criteria for the diagnosis of anaphylaxis that are promulgated in the Guidelines have been validated. Some aspects of anaphylaxis treatment have been prospectively studied. Novel investigations of self-injectable epinephrine for treatment of anaphylaxis recurrences in the community have been performed. Progress has been made with regard to measurement of specific IgE to allergen components (component-resolved testing) that might help to distinguish clinical risk of future anaphylactic episodes to an allergen from asymptomatic sensitization to the allergen. New strategies for immune modulation to prevent food-induced anaphylaxis and new insights into subcutaneous immunotherapy to prevent venom-induced anaphylaxis have been described.

SUMMARY

Research highlighted in this Update strengthens the evidence-based recommendations for assessment, management, and prevention of anaphylaxis made in the WAO Anaphylaxis Guidelines.

Quantitation of IgE binding to the chitinase and chitinase-like house dust mite allergens Der p 15 and Der p 18 compared to the major and mid-range allergens

BACKGROUND

The prevalence of IgE binding to the group 15 and 18 house dust mite (HDM) allergens of the Dermatophagoides species is reported to be >50% and they are the major allergens of HDM-sensitised dogs. The objective was to quantitate the IgE titres to Der p 15 and Der p 18 and evaluate their importance in human HDM sensitisation compared to the known major and mid-tier allergens.

METHODS

Der p 15 and Der p 18 were produced in Pichia pastoris, and their structure validated by circular dichroism. IgE binding was measured in 37 Australian HDM-allergic adults using a quantitative DELFIA™ assay.

RESULTS

The prevalence of IgE titres to Der p 15 and Der p 18 >0.1 ng/ml was low (38%) and only one subject had a titre >10 ng/ml to either allergen. The mean anti-Der p 15 and Der p 18 titres were 1.2 and 2.6 ng/ml, respectively, i.e. approximately 10- to 20-fold lower than the response to the major Der p 1 and Der p 2 allergens (p < 0.001). The IgE responses to Der p 15 and Der p 18 were lower than the mid-tier allergens Der p 5 and Der p 7 and although they correlated with each other, they did not correlate with titres to either the major or mid-tier allergens.

CONCLUSIONS

Sensitisation to Der p 15 and Der p 18 makes a minor contribution to anti-HDM IgE titres, and the titres do not correlate with the size of the response to the major allergens.

Component-resolved diagnosis in pediatrics

Component resolved diagnosis is a new concept in the investigation of pediatric allergic disease. The aim of the present paper is to review the available data on component resolved diagnosis with respect to implications for investigation of children with allergic disease. In most conditions head-to-head comparisons of component resolved diagnosis with traditional IgE testing have not been performed. Rather than alternatives the molecular methods should be seen as adjuncts to the cheaper traditional specific IgE tests. It may be appropriate to determine IgE antibodies to components as part of the diagnostic work-up in selected cases of peanut and birch pollen allergy and in hymenoptera allergy. However, cost benefit analyses of component resolved diagnosis compared with traditional work-up of allergy are needed. Prospectively planned protocols for assessment of the extent to which component resolved diagnosis may be able to improve the selection of children to immunotherapy and, thus, the efficacy of immunotherapy, are needed. Finally, studies of component resolved diagnosis with microarray technology in screening panels with hundreds of components should be undertaken before it can be determined to which extent such panel screening, if at all, may be helpful in children.