Allergen Microarrays for In Vitro Diagnostics of Allergies: Comparison with ImmunoCAP and AdvanSure

Establishment of a homogeneous chemiluminescence immunoassay for cat dander sIgE antibody detection

BACKGROUND

In vitro specific IgE (sIgE) testing has become an important tool for the diagnosis of IgE-mediated allergic diseases. Current methods used to detect allergen sIgE are time consuming and/or expensive. Therefore, a new method was developed for rapid quantitative detection of cat dander-sIgE antibody based on homogeneous chemiluminescence immunoassay.

METHODS

Selection of chemibeads with different chemical groups, and the best Light-initiated chemiluminescence assay (LiCA) analytical mode for cat dander-sIgE detection. To validate and eliminate the interference of IgE on the detection of cat dander-sIgE, concentration of biotinylated anti-human IgE antibody was optimized. For quantification of cat dander-sIgE, a calibration curve was established, and the performance of the assay was evaluated according to clinical guidelines.

RESULTS

Indirect LiCA is the best mode of analysis and biotinylated anti-human IgE antibody at a dilution ratio of 1:250 minimizes IgE interference. The coefficient of variation of the developed LiCA was 1.49% to 4.66%, with an intermediate precision of 6.90% to 8.21%. The LoB, LoD, and LoQ of the assay were 0.023 kUA/L, 0.056 kUA/L and 0.185 kUA/L. The coefficient of correlation (r) between LiCA and ImmounoCAP was 0.9478.

CONCLUSIONS

A cat dander-sIgE quantitation assay based on homogeneous chemiluminescence immunoassay was established, which could be a new reliable analytical tool for the determination of cat dander-sIgE.

Effect of house dust mite allergen on sleep parameters and sleep quality

PURPOSE

The role of nasal problems such as allergic rhinitis in the development of obstructive sleep apnea (OSA) is controversial. The purpose of this study was to analyze the effects of house dust mite (HDM) allergen on sleep-related problems.

METHODS

In a retrospective study patients were classified according to the house dust mite (HDM)-related specific immunoglobulin E (IgE) level into a low HDM-IgE group (group A) and a high HDM-IgE group (group B). Polysomnographic indices, OSA severity, and self-administered questionnaire results were compared between groups. Correlational analysis was used to identify associations between specific IgE values and sleep parameters related to respiratory events.

RESULTS

A total of 327 patients were enrolled. N1 stage ratio, apnea index, and apnea-hypopnea index were significantly higher in group B (P = 0.010, 0.003, and 0.002 respectively) than in group A. N2 stage ratio, and lowest and mean oxygen saturation were significantly lower in group B (P = 0.001, 0.001, and < 0.001 respectively). After propensity score matching, the apnea index and lowest and mean oxygen saturation remained significantly different (P = 0.005, 0.005, and 0.001 respectively). Patients in group B were more likely to have severe OSA and worse subjective sleep quality. In correlational analysis, lowest and mean oxygen saturation were significantly negatively correlated with specific IgE values.

CONCLUSION

A high HDM-specific IgE level was associated with the occurrence of respiratory events and oxygen desaturation during sleep, and with the presence of severe OSA, as well as poorer subjective sleep quality.

AHR rs4410790 genotype and IgG levels: Effect modification by lifestyle factors

Inflammation is a multifaceted marker resulting from complex interactions between genetic and lifestyle factors. Emerging evidence suggests Aryl hydrocarbon receptor (AHR) protein may be implicated in the regulation of immune system and inflammatory responses. To investigate whether rs4410790 genotype (TT, TC, CC) near AHR gene is related to serum IgG levels, a marker of chronic inflammation, and whether lifestyle factors modifies the relationship, we conducted a cross-sectional study by recruiting 168 Korean adults. Participants responded to a lifestyle questionnaire and provided oral epithelial cells and blood samples for biomarker assessment. Among these participants, C allele was the minor allele, with the minor allele frequency of 40%. The rs4410790 TT genotype was significantly associated with elevated IgG levels compared with TC/CC genotypes, after adjusting for potential confounders (p = 0.04). The relationship varied significantly by levels of alcohol consumption (P interaction = 0.046) and overweight/obese status (P interaction = 0.02), but not by smoking status (P interaction = 0.64) and coffee consumption (P interaction = 0.55). Specifically, higher IgG levels associated with the TT genotype were evident in frequent drinkers and individuals with BMI≥23kg/m2, but not in their counterparts. Thus, rs4410790 genotype may be associated with IgG levels and the genetic predisposition to higher IgG levels may be mitigated by healthy lifestyle factors like infrequent drinking and healthy weight.

Modern Concept of Molecular Diagnostics of Allergy to Dogs

The number of people suffering from allergies is increasing worldwide every year. With the prevalence of domestic animals, especially dogs, allergens associated with them can be found ubiquitously, thereby increasing the risk of anaphylaxis in sensitized individuals. Currently, there are 8 known dog allergens, but not all of them have been thoroughly studied. The commonly used skin prick tests often fall short and fail to provide a comprehensive assessment of a patient's condition, thus making allergy diagnosis challenging. Fortunately, the introduction of new allergy diagnostic methods has made it possible to accurately identify clinically significant allergens for patients. These findings can then be used to prescribe appropriate therapy or provide specific recommendations to the patients. This review focuses on the most important dog allergens and modern allergy diagnostic techniques that are gradually being incorporated into medical practice, thus expanding the capabilities of allergists.

Inter-laboratory comparison of semiquantitative allergen-specific Immunoglobulin E test: 7 years of experience in Korea

INTRODUCTION

Multiple allergen simultaneous test (MAST) is widely used as a screening tool for allergic diseases and has the advantage of providing specific IgE (sIgE) results for various allergens in semiquantitative class. We have continuously conducted external quality assessment (EQA) since 2012 for clinical laboratories performing MAST using AdvanSure allergy screen test (LG CHEM, Korea). This study provides an account of the EQA experience.

METHODS

Samples were prepared using pooled sera collected from patients with suspected allergic disease and sent to each laboratory twice a year. Each round included 4-6 serum samples with sIgE for 10-20 inhaled or food allergens. The acceptable class value was the most frequently reported MAST class ±1 titer that exceeded 80% of the total laboratory results.

RESULTS

The average number of participating laboratories was 76 (49-90) and the average response rate was 97.3% during the entire survey period. The acceptable rates were consistently high at 97.7% ± 3.7%. Of the total 537 trials, 18 trials (3.4%) were regarded as nonconsensus results, in which acceptable answers did not exceed 80%. For unacceptable results, the false-negative rate (1.5% ± 2.8%) was higher than the false-positive rate (0.8% ± 2.7%) (p < 0.001). MAST class results were correlated with quantitative IgE results by ImmunoCAP (Spearman's correlation coefficient of 0.682 (p < 0.001) and gamma index of 0.777 (p < 0.001).

CONCLUSION

Although EQA for MAST showed a high level of acceptable answer, some allergen assays require harmonization. Continuous performance of systematic EQA is needed to improve the accuracy of sIgE assays and quality control in clinical laboratories.

Validation of a commercial allergen microarray platform for specific immunoglobulin E detection of respiratory and plant food allergens

BACKGROUND

As the use of multiplex-specific immunoglobulin E (sIgE) detection methods becomes increasingly widespread, proper comparative validation assessments of emerging new platforms are vital.

OBJECTIVE

To evaluate the clinical and technical performance of a newly introduced microarray platform, Allergy Explorer (ALEX) (MacroArray Diagnostics), in the diagnosis of pollen (cypress, grass, olive), dust mite (Dermatophagoides pteronyssinus), mold (Alternaria alternata), fruit (apple, peach), and nut (walnut, hazelnut and peanut) allergies and to compare it with those of the ImmunoCAP Immuno Solid-phase Allergen Chip (ISAC) 112 microarray and the ImmunoCAP singleplex method (ThermoFisher Scientific).

METHODS

We enrolled 153 patients with allergy and 16 controls without atopy. The sIgE assays were conducted using ISAC112, ALEX version 2 (ALEX2), and ImmunoCAP for whole extracts and major components. Technical validation of ALEX2 was performed by measuring repeatability and interassay, interbatch, and interlaboratory reproducibility.

RESULTS

When measured globally (detection by 1 or more allergen components), ALEX2 had adequate sensitivity and specificity for most of the allergens studied, comparable in general with that of ISAC112 (except for olive pollen and walnut) and similar to that of ImmunoCAP whole extract measurements. Component-by-component analysis revealed comparable results for all techniques, except for Ole e 1 and Jug r 3, in both ISAC112 and ImmunoCAP comparisons, and Alt a 1, when compared with ISAC112. Continuous sIgE levels correlate with sIgE by ImmunoCAP. Good reproducibility and repeatability were observed for ALEX2.

CONCLUSION

ALEX2 has sound technical performance and adequate diagnostic capacity, comparable in general with that of ISAC112 and ImmunoCAP.

A light-initiated chemiluminescent assay for the detection of children's milk protein-specific IgE with excellent ability to avoid interference of specific IgG

The detection of allergen-specific IgE is of value for the diagnosis of children's milk allergy. However, its accuracy will interfere with the presence of high levels of specific IgG in the serum of children with milk allergy. To solve this problem, we established a light-initiated chemiluminescent assay (LICA) based on nanomicrospheres, which neutralized the interference of specific IgG by increasing the amount of antigen coated on the microspheres. The ability of this method to resist IgG interference was confirmed by adding extra specific IgG to the serum of allergic patients. Finally, the positive rate of allergen-specific IgE was increased to 85%, which was better than the indirect ELISA (70%), indicating that this method has certain advantages for the detection of specific IgE in children with milk allergy.

Noninvasive and minimally invasive techniques for the diagnosis and management of allergic diseases

Allergic diseases of the (upper and lower) airways, the skin and the gastrointestinal tract, are on the rise, resulting in impaired quality of life, decreased productivity, and increased healthcare costs. As allergic diseases are mostly tissue-specific, local sampling methods for respective biomarkers offer the potential for increased sensitivity and specificity. Additionally, local sampling using noninvasive or minimally invasive methods can be cost-effective and well tolerated, which may even be suitable for primary or home care sampling. Non- or minimally invasive local sampling and diagnostics may enable a more thorough endotyping, may help to avoid under- or overdiagnosis, and may provide the possibility to approach precision prevention, due to early diagnosis of these local diseases even before they get systemically manifested and detectable. At the same time, dried blood samples may help to facilitate minimal-invasive primary or home care sampling for classical systemic diagnostic approaches. This EAACI position paper contains a thorough review of the various technologies in allergy diagnosis available on the market, which analytes or biomarkers are employed, and which samples or matrices can be used. Based on this assessment, EAACI position is to drive these developments to efficiently identify allergy and possibly later also viral epidemics and take advantage of comprehensive knowledge to initiate preventions and treatments.

The use of microarray and other multiplex technologies in the diagnosis of allergy

OBJECTIVE

To give an overview and describe the strengths and weaknesses of immunoglobulin E (IgE) microarray and other multiplex assays that have been developed and are being used for allergy diagnostics.

DATA SOURCES

Queries for IgE microarray and multiplex assays were conducted with PubMed and Google Scholar, searching for primary articles and review papers.

STUDY SELECTIONS

We focused on articles written in English on commercially available IgE multiplex assays that were reported in the allergy and immunology literature.

RESULTS

Several commercial IgE assays that use microarray or other multiplex technology have been developed, and some have been implemented into clinical practice in Europe and Asia, with the Immuno Solid-Phase Allergen Chip being the most widely studied. Results of these assays generally correlate with results using "singleplex" IgE assays (eg, ImmunoCAP), though there can be variability among products and among allergens. A strength of the microarray technology is that IgE to a large number of allergens can be detected simultaneously in a single test, and only a small amount of patient serum is required. Cost, inadequate sensitivity under some scenarios, and difficulties with data interpretation, in some cases of 100 or more allergens, can be limitations.

CONCLUSION

IgE microarray assays are already a valuable tool in research applications. These assays, and also other forms of IgE multiplex assays, are likely to play an important role in the clinical practice of allergy in the future. Additional studies focused on clinical outcomes, and the development of more targeted allergen panels could facilitate increased clinical use.

Genetically encoded biosensors for the detection of rapamycin: toward the screening of agonists and antagonists

Biosensors are valuable tools for the rapid screening of biological targets with high sensitivity and specificity. It is important to screen biological events in their native context for pharmacological and toxicological applications. However, in vitro biosensors often require purified probes and targets for screening, thus providing limited information on the biological activities of targets in their native environment. To address this issue, we developed a cell-based sensing system that could detect a biologically active small molecule, rapamycin (Rapa). We designed a reporter system based on fluorescence translocation by signal peptide reconstitution. Herein, signal peptides are activated by conditional protein splicing without the need for refolding into a functional tertiary structure, thus eliminating false positives and negatives due to mere binding or misfolding. The developed biosensor demonstrated excellent sensitivity with a limit of detection of 0.1 nM, and it was able to screen the agonist and antagonist of Rapa. The developed cell-based sensing system could contribute to improving the screening system aimed to identify the natural mimetics of Rapa and potential drug candidates.

Fabrication of Microarrays for the Analysis of Serological Antibody Isotypes against Food Antigens

Food intolerance is delayed adverse food reactions which follow consumption of specific foods. The underlying mechanisms are not well understood, but food intolerance is often considered as a type 2 hypersensitivity reaction mediated by immunoglobulin G (IgG) antibody. To understand the causes of food intolerance, it is important to investigate sensitization patterns of food-specific IgGs (sIgG) in relation to dietary patterns and physical conditions. Conventional approaches to measure serological IgGs often require large volumes of serum, thus are not suitable for highly multiplexed assays. To overcome this impracticality, we developed a highly sensitive method to screen the sIgGs and other antibody isotypes against 66 antigens with minimal amount of serums. We prepared a microarray by immobilizing food antigens on activated glass slides. Human sera and their dietary information were obtained from 30 subjects. Aliquots (200 nl) of sera were analyzed against 66 food antigens in parallel. sIgG levels were determined and analyzed in relation to subjects' dietary patterns. The levels of antibody isotypes were also examined to understand the relationship between allergy and food intolerance. The developed microarray showed exceptional performances in antibody screening and demonstrated the potential to be used as an automated assay system.

Development of a comprehensive protein microarray for immunoglobulin E profiling in horses with severe asthma

BACKGROUND

Severe asthma in horses, known as severe equine asthma (SEA), is a prevalent, performance-limiting disease associated with increased allergen-specific immunoglobulin E (IgE) against a range of environmental aeroallergens.

OBJECTIVE

To develop a protein microarray platform to profile IgE against a range of proven and novel environmental proteins in SEA-affected horses.

ANIMALS

Six SEA-affected and 6 clinically healthy Warmblood performance horses.

METHODS

Developed a protein microarray (n = 384) using protein extracts and purified proteins from a large number of families including pollen, bacteria, fungi, and arthropods associated with the horses, environment. Conditions were optimized and assessed for printing, incubation, immunolabeling, biological fluid source, concentration techniques, reproducibility, and specificity.

RESULTS

This method identified a number of novel allergens, while also identifying an association between SEA and pollen sensitization. Immunolabeling methods confirmed the accuracy of a commercially available mouse anti-horse IgE 3H10 source (R2 = 0.91). Biological fluid source evaluation indicated that sera and bronchoalveolar lavage fluid (BALF) yielded the same specific IgE profile (average R2 = 0.75). Amicon centrifugal filters were found to be the most efficient technique for concentrating BALF for IgE analysis at 40-fold. Overnight incubation maintained the same sensitization profile while increasing sensitivity. Reproducibility was demonstrated (R2 = 0.97), as was specificity using protein inhibition assays. Arthropods, fungi, and pollens showed the greatest discrimination for SEA.

CONCLUSIONS AND CLINICAL IMPORTANCE

We have established that protein microarrays can be used for large-scale IgE mapping of allergens associated with the environment of horses. This technology provides a sound platform for specific diagnosis, management, and treatment of SEA.

A paper-based chemiluminescence immunoassay device for rapid and high-throughput detection of allergen-specific IgE

The fast and precise detection of potential allergen-specific immunoglobulin E (sIgE) is imperative for the diagnosis and appropriate treatment of allergic diseases. In this study, we have successfully fabricated a novel paper-based immunoassay device for the detection of sIgE in allergic diseases. We used Can f 1, one of the main dog allergens, as a model allergen to detect sIgE in human sera. To achieve excellent performance, the experimental parameters were optimized. Further, we extended this device for potential applications in the clinical diagnosis of allergic diseases: worthwhile clinical performance in the detection of allergens was achieved as compared to that achieved by commercial enzyme-linked immunosorbent assay (ELISA) kit. Therefore, it was proven that this strategy has the advantages of high-throughput, rapid, sensitive, and highly accurate detection of trace amounts of sIgEs. Furthermore, by simply changing the antigen and antibody, this device could be used for the high-throughput detection of other allergens, so as to achieve multiallergen detection and appropriate desensitization therapy, thereby making it promising in the determination of allergic diseases in clinics.

Recent advances in the diagnosis of allergic rhinitis

INTRODUCTION

Allergic rhinitis (AR) is a disorder with high prevalence worldwide. Identification of clinically relevant allergens is the key step for the diagnosis, allergen avoidance and allergen specific immunotherapy for AR. Areas covered: With the new findings of mechanisms of AR and the development of technology, much progress has been achieved in the diagnosis of AR recently. We review the recent advances about local IgE, in vivo and in vitro tests, cytological diagnosis and nitric oxide (NO) in the diagnosis of AR. Expert commentary: AR is traditionally diagnosed with the combined evaluation of history and allergen sensitization by in vivo skin prick tests and in vitro allergen specific IgE in serum, to confirm the correlation between clinical history and potential allergens. Nasal provocation test and local IgE measurement can be used to diagnose local AR. Allergen microarray has the ability to detect more potential allergens. Basophil activation and mast cell activation tests can be used in allergen diagnosis and to modify the response to immunotherapy, while cytological diagnosis is useful in the differential diagnosis of AR and non-AR. Nasal NO has been confirmed to be an optimal biomarker to discriminate between AR and non-AR.