Applications of basophil activation test in paediatric allergic diseases

Basophilic granulocytes, containing and releasing histamine after a specific allergy stimulation, are directly involved in IgE-mediated allergic reactions. CD63 is a transmembrane protein of secretory lysosomes of basophils and its upregulation is related with the release of histamine to the extracellular space during IgE-mediated allergic reactions. Basophil activation test (BAT) measures the activation of circulating basophils upon the in vitro stimulation of living blood cells with specific allergens. Such a test is particularly safe and reproducible and has recently emerged as a new promising diagnostic tool for allergic diseases. BAT can be used to diagnose food allergy and represents a promising alternative to oral food challenge tests, especially in children as it is less invasive, safer, and cheaper than the gold standard tests. As a biomarker of tolerance and reactivity, it is also useful to monitor natural resolution and clinical response to immune-modulatory treatments. Regarding drug allergies, BAT is even the only possible applicable diagnostic tool for allergy reactions to some drugs, because of the lack of alternative test, or given that those commonly used are unreliable, or equivocal. Additionally, BAT allows to screen patients with more active urticarial and identify Hymenoptera-allergic patients with negative venom-specific immunoglobulin (Ig)E. In respiratory allergic diseases, BAT can facilitate the diagnosis of local allergic rhinitis and evaluate basophil allergen sensitivity in allergic asthma. Although IgE-sensitization in allergic asthma is usually demonstrated by skin prick test and specific IgE, those tests do not predict the clinical allergy contribution to asthma pathogenesis. To date, the potential of BAT in the diagnostic work-up of allergic diseases is well established, but a better standardization of its use is needed. This narrative review summarizes the state-of-the-art BAT technology and applications in pediatric allergic diseases, focusing on immune-related mechanisms and the BAT real clinical utility.

[Basophil activation test to follow-up of patients treated with hymenoptera venom immunotherapy: a review of current evidence]

Hymenoptera venom immunotherapy (HVI) is a long-term effective treatment to avoid new systemic reactions in patients with Hymenoptera allergy. The sting challenge test is considered the gold standard to confirm the tolerance. However, the use of this technique is not generalized in clinical practice, being the basophil activation test (BAT), which functionally explores allergen response, an alternative that does not entail any of the provocation risks associated with the sting challenge test. This study reviews the publications that used the BAT to follow up and evaluate the success of the HVI. Studies assessing the changes between a baseline BAT before the start and BATs performed between the starting and maintenance phases of the HVI were selected. Ten articles were found, comprising information from 167 patients, of which 29% used the sting challenge test. The studies concluded the importance of evaluating the responses with submaximal allergen concentrations, which reflect basophil sensitivity, to monitor the HVI using the BAT. It was also observed that changes in the maximum response (reactivity) could not reflect the clinical status of tolerance, particularly in the initial phases of HVI.

Practical guidelines for the response to perioperative anaphylaxis

Perioperative anaphylaxis is a severe adverse event during anesthesia that requires prompt diagnosis and treatment by physicians, including anesthesiologists. Muscle relaxants and antibiotics are the most common drugs that cause perioperative anaphylaxis in Japan, as in many countries. In addition, sugammadex appears to be a primary causative agent. Obtaining previous anesthesia records is necessary in a patient with a history of allergic reactions during anesthesia, whenever possible, to avoid recurrence of anaphylaxis. Although medical staff are likely to notice abnormal vital signs because of complete monitoring during anesthesia, surgical drapes make it difficult to notice the appearance of skin symptoms. Even if there are no skin symptoms, anaphylaxis should be suspected, especially when hypotension resistant to inotropes and vasopressors persists. For improving the diagnostic accuracy of anaphylaxis, it is helpful to collect blood samples to measure histamine/tryptase concentrations immediately after the events and at baseline. The first-line treatment for anaphylaxis is adrenaline. In the perioperative setting, adrenaline should be administered through the intravenous route, which has a faster effect onset and is secured in most cases. Adrenaline can cause serious complications including severe arrhythmias if the appropriate dose is not selected according to the severity of symptoms. The anesthesiologist should identify the causative agent after adverse events. The gold standard for identifying the causative agent is the skin test, but in vitro tests including specific IgE antibody measurements and basophil activation tests are also beneficial. The Working Group of the Japanese Society of Anesthesiologists has developed this practical guide to help appropriate prevention, early diagnosis and treatment, and postoperative diagnosis of anaphylaxis during anesthesia.Grade of recommendations and levels of evidence Anaphylaxis is a relatively rare condition with few controlled trials, and thus a so-called evidence-based scrutiny is difficult. Therefore, rather than showing evidence levels and indicating the level of recommendation, this practical guideline only describes the results of research available to date. The JSA will continue to investigate anaphylaxis during anesthesia, and the results may lead to an amendment of this practical guideline.

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.

Basophil activation test: Mechanisms and considerations for use in clinical trials and clinical practice

The basophil activation test (BAT) is a functional assay that measures the degree of degranulation following stimulation with allergen or controls by flow cytometry. It correlates directly with histamine release. From the dose-response curve resulting from BAT in allergic patients, basophil reactivity (%CD63⁺ basophils) and basophil sensitivity (EC₅₀ or similar) are the main outcomes of the test. BAT takes into account all characteristics of IgE and allergen and thus can be more specific than sensitization tests in the diagnosis of allergic disease. BAT reduces the need for in vivo procedures, such as intradermal tests and allergen challenges, which can cause allergic reactions of unpredictable severity. As it closely reflects the patients' phenotype in most cases, it may be used to support the diagnosis of food, venom and drug allergies and chronic urticaria, to monitor the natural resolution of food allergies and to predict and monitor clinical the response to immunomodulatory treatments, such as allergen-specific immunotherapy and biologicals. Clinical application of BAT requires analytical validation, clinical validation, standardization of procedures and quality assurance to ensure reproducibility and reliability of results. Currently, efforts are ongoing to establish a platform that could be used by laboratories in Europe and in the USA for quality assurance and certification.

A Case of Anaphylaxis in Which a Basophil Activation Test Was Used to Identify the Suspected Agent

This is a case report of anaphylaxis in which the basophil activation test (BAT) was used to identify the etiological agent. Although skin tests are considered the most effective methods for identifying anaphylactic triggers, the test itself presents a risk of inducing anaphylaxis. The BAT is advantageous because of its inherent lack of risk, high sensitivity and specificity to identify the suspected anaphylactic agents, and diagnostic accuracy comparable to conventional skin testing. Therefore, in the future, the BAT is likely to become the preferred test for the detection of allergens over conventional skin tests.

Basophil Activation Test: Old and New Applications in Allergy

PURPOSE OF REVIEW

The basophil activation test (BAT) using flow cytometry has supplanted traditional methods of measuring basophil degranulation using histamine and other mediator release, and can be used for clinical applications as well as to explore the immune mechanisms of effector cell response to allergen. This review discusses the advancements made in clinical, diagnostic and laboratory research of allergy utilizing an ever-evolving BAT.

RECENT FINDINGS

Being an in vitro surrogate of the allergic reaction that happens in vivo in the sick patient, the BAT can be used to support the diagnosis of various allergic conditions, such as food, drug, respiratory and insect venom allergies, and the assessment of clinical response to allergen-specific immunotherapy and other immunomodulatory treatments. The BAT can also be used for research purposes to explore the mechanisms of allergy and tolerance at the level of the basophil, for instance by manipulating IgE and IgG and their receptors and by studying intracellular signalling cascade in response to allergen. This review covers the applications of the BAT to the clinical management of allergic patients and the increased understanding of the mechanisms of immune response to allergens as well as technological advancements made in recent years.

Prueba de activación de basófilos: aspectos técnicos, metodológicos y su utilidad clínica

Introducción. La prueba de activación de basófilos (PAB) se considera una técnica confiable y segura para el diagnóstico de problemas alérgicos.Objetivo. Profundizar en el estado del arte de la PAB y su utilidad clínica.Materiales y métodos. Se realizó una revisión narrativa de la literatura mediante la búsqueda electrónica en las bases de datos y metabuscadores Ovid Medline, Google Scholar y PubMed, sin limitar la búsqueda por fecha, idioma o tipo de artículo. Se buscaron artículos sobre los detalles técnicos de la PAB y su utilidad clínica en el manejo de las enfermedades alérgicas.Resultados. De los marcadores de activación, CD63 ha sido el más estudiado y es el que mejor representa un evento de degranulación anafiláctica, mientras que CD203c es representativo de varias formas de degranulación. La superioridad de uno sobre otro como prueba diagnóstica depende del problema alérgico estudiado. En cuanto a los métodos de detección de basófilos, su selección con un único marcador, CCR3, se propone como una opción con buena relación de costo-efectividad.Conclusiones. La PAB es una herramienta prometedora para evaluar en clínica las reacciones alérgicas de forma segura. Es necesario una mayor estandarización de protocolos para obtener resultados más reproducibles.

Basophil Degranulation Assay

Basophil degranulation assay has gained importance over the last decade in both diagnosis of food allergy and evaluation of progression of immunotherapy. This assay involves the identification and quantification of the expression of CD63 molecule on basophil membrane. CD63 is a marker of multivesicular bodies that is exposed to cell membrane during the process of degranulation in which the contents of basophil granules are released. This chapter describes the methodology for performing this assay.

Allergy tests do not predict food triggers in adult patients with eosinophilic oesophagitis. A comprehensive prospective study using five modalities

BACKGROUND

The use of allergy tests to guide dietary treatment for eosinophilic oesophagitis (EoE) is controversial and data are limited. Aeroallergen sensitisation patterns and food triggers have been defined in Northern Hemisphere cohorts only.

AIMS

To determine if allergy tests that are routinely available can predict food triggers in adult patients with EoE. To define the food triggers and aeroallergen sensitisation patterns in a novel Southern Hemisphere (Australian) cohort of patients.

METHODS

Consecutive patients with EoE who elected to undergo dietary therapy were prospectively assessed, demographic details and atopic characteristics recorded, and allergy tests, comprising skin-prick and skin-patch tests, serum allergen-specific IgE, basophil activation test and serum food-specific IgG, were performed. Patients underwent a six-food elimination diet with a structured algorithm that included endoscopic and histological examination of the oesophagus a minimum of 2 weeks after each challenge. Response was defined as <15 eosinophils per HPF. Foods defined as triggers were considered as gold standard and were compared with those identified by allergy testing.

RESULTS

No allergy test could accurately predict actual food triggers. Concordance among skin-prick and serum allergen-specific IgE was high for aeroallergens only. Among seasonal aeroallergens, rye-grass sensitisation was predominant. Food triggers were commonly wheat, milk and egg, alone or in combination.

CONCLUSIONS

None of the currently-available allergy tests predicts food triggers for EoE. Exclusion-rechallenge methodology with oesophageal histological assessment remains the only effective investigation. The same food triggers were identified in this southern hemisphere cohort as previously described.

Biomarkers of the involvement of mast cells, basophils and eosinophils in asthma and allergic diseases

Biomarkers of disease activity have come into wide use in the study of mechanisms of human disease and in clinical medicine to both diagnose and predict disease course; as well as to monitor response to therapeutic intervention. Here we review biomarkers of the involvement of mast cells, basophils, and eosinophils in human allergic inflammation. Included are surface markers of cell activation as well as specific products of these inflammatory cells that implicate specific cell types in the inflammatory process and are of possible value in clinical research as well as within decisions made in the practice of allergy-immunology.

Flow-assisted basophil activation tests in immediate drug hypersensitivity: two decades of Antwerp experience

The last two decades have witnessed that flow-assisted analysis of in vitro-activated basophils can constitute a valuable adjunct in the in vitro diagnostic approach of immediate drug hypersensitivity reactions (IDHR). This article summarises the current experience with the basophil activation test in the diagnosis of IDHR, with particular focus on allergy to curarising neuromuscular blocking agents, antibiotics (β-lactams and fluoroquinolones), iodinated radiocontrast media and opiates.

Molecular allergy diagnostics using IgE singleplex determinations: methodological and practical considerations for use in clinical routine: Part 18 of the Series Molecular Allergology

Allergen molecules (synonyms: single allergens, allergen components) open up new horizons for the targeted allergen-specific diagnostics of immunoglobulin E (IgE) in singleplex determination. The following rationales support the targeted use of allergen molecules and, more importantly, improve test properties: (1) increased test sensitivity ("analytical sensitivity"), particularly when important allergens are under-represented or lacking in the extract; (2) improved test selectivity (analytical specificity), particularly when the selected IgE repertoire against an allergen yields additional information on: (a) potential risk, (b) possible cross-reactivity, or (c) primary (species-specific) sensitization. However, the appropriate indication for the use of single allergens can only be established on a case-by-case basis (depending on the clinical context and previous history) and in an allergen-specific manner (depending on the allergen source and the single allergens available), rather than in a standardized way. Numerous investigations on suspected food allergy, insect venom allergy, or sensitization to respiratory allergens have meanwhile demonstrated the successful use of defined molecules for allergen-specific singleplex IgE diagnosis. Specific IgE to single allergens is limited in its suitability to predict the clinical relevance of sensitivity on an individual basis. In food allergies, one can at best identify the relative risk of a clinical reaction on the basis of an IgE profile, but no absolutely reliable prediction on (future) tolerance can be made. Ultimately, the clinical relevance of all IgE findings depends on the presence of corresponding symptoms and can only be assessed on an individual basis (previous history, symptom log, and provocation testing with the relevant allergen source where appropriate). Thus, also in molecular allergology, the treating physician and not the test result should determine the clinical relevance of diagnostic findings.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available for this article at 10.1007/s40629-015-0067-z and is accessible for authorized users.