Validation of a two-color flow cytometric assay detecting in vitro basophil activation for the diagnosis of IgE-mediated natural rubber latex allergy

IgE-Mediated Cannabis Allergy and Cross-Reactivity Syndromes: A Roadmap for Correct Diagnosis and Management

PURPOSE OF THE REVIEW

With increased access and decriminalization of cannabis use, cases of IgE-dependent cannabis allergy (CA) and cross-reactivity syndromes have been increasingly reported. However, the exact prevalence of cannabis allergy and associated cross-reactive food syndromes (CAFS) remains unknown and is likely to be underestimated due to a lack of awareness and insufficient knowledge of the subject among health care professionals. Therefore, this practical roadmap aims to familiarize the reader with the early recognition and correct management of IgE-dependent cannabis-related allergies. In order to understand the mechanisms underlying these cross-reactivity syndromes and to enable personalized diagnosis and management, special attention is given to the molecular diagnosis of cannabis-related allergies.

RECENT FINDINGS

The predominant signs and symptoms of CA are rhinoconjunctivitis and contact urticaria/angioedema. However, CA can also present as a life-threatening condition. In addition, many patients with CA also have distinct cross-reactivity syndromes, mainly involving fruits, vegetables, nuts and cereals. At present, five allergenic components of Cannabis sativa (Can s); Can s 2 (profilin), Can s 3 (a non-specific lipid protein), Can s 4 (oxygen-evolving enhancer protein 2 oxygen), Can s 5 (the Bet v 1 homologue) and Can s 7 (thaumatin-like protein) have been characterized and indexed in the WHO International Union of Immunological Sciences (IUIS) allergen database. However, neither of them is currently readily available for diagnosis, which generally starts by testing crude extracts of native allergens. The road to a clear understanding of CA and the associated cross-reactive food syndromes (CAFS) is still long and winding, but well worth further exploration.

Latex Allergy - From Discovery to Component-resolved Diagnosis

Latex allergy is a hypersensitivity response to natural rubber latex (NRL) proteins or rubber chemicals used in the manufacture of latex products. An accurate diagnosis is the first step in the effective management of individuals with latex allergy, especially in high-risk groups, such as healthcare workers and those affected by spina bifida. Diagnosis is based on the clinical history and an accurate allergological evaluation. In the case of type I IgE-mediated hypersensitivity reactions, which can manifest urticaria, angioedema, rhinoconjunctivitis, asthma and anaphylaxis after latex exposure, skin prick tests or latex-specific IgE (sIgE) antibody detection using serological assays can be performed to confirm sensitization. Instead, in the case of contact dermatitis, a patch test can be applied to confirm the presence of a type IV T cell-mediated hypersensitivity reaction to rubber accelerators or additives. Basophils activation tests or challenge tests may be performed if there's an incongruity between the clinical history and the results of in vivo and in vitro tests. The aim of this review is to analyze the current state of the art of diagnostic techniques for latex allergy and algorithms employed in clinical practice and possible future developments in this field.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

A quarter of a century fundamental and translational research in perioperative hypersensitivity and anaphylaxis at the Antwerp university hospital, a Belgian Centre of Excellence of the World Allergy Organization

Perioperative hypersensitivity constitutes an important health issue, with potential dramatic consequences of diagnostic mistakes. However, safe and correct diagnosis is not always straightforward, mainly because of the application of incorrect nomenclature, absence of easy accessible in-vitro/ex-vivo tests and uncertainties associated with the non-irritating skin test concentrations. In this editorial we summarize the time line, seminal findings, and major realizations of 25 years of research on the mechanisms, diagnosis, and management of perioperative hypersensitivity.

Reliability of Early and Late Testing for Suspected Perioperative Hypersensitivity

BACKGROUND

The optimal timing of diagnostic testing for perioperative hypersensitivity (POH) remains unknown. It has been recommended that investigation is best carried out at least 4 to 6 weeks after the event. On the other hand, guidelines discourage the use of in vitro tests later than 3 years after the index reaction.

OBJECTIVE

This retrospective study aimed to assess the reliability of early and late skin tests (STs). It also attempted to verify whether discouraging late ex vivo and in vitro tests is substantiated.

METHODS

For the first aim, patients were stratified over three epochs: an early timing group, with investigations performed within 6 weeks; a recommended timing group, with tests performed between 6 weeks and 6 months; and a late timing group, tested later than 6 months after the event. For the second study purpose, we studied the reliability of specific IgE quantification and basophil activation test rocuronium within 6 weeks and after 3 years in patients who experienced an ST-proven POH to rocuronium.

RESULTS

A total of 677 patients were included. Based on a positive ST result, a causative agent was found in 74.2% of the early timing group, 62.6% of the recommended timing group, and 50% of the late timing group. A positive specific IgE for rocuronium or morphine was found in 80% of patients tested within 6 weeks, 63% of patients tested between 6 weeks and 3 years, and 50% of patients tested more than 3 years after the event. A positive basophil activation test was found in 83.3%, 51%, and 20%, respectively, of patients.

CONCLUSIONS

Our data confirm that evaluation of drug allergy for suspected POH can be performed before 6 weeks after the event, and there is no maximal upper time limit disclosing ex vivo and in vitro testing.

Carbohydrate epitopes currently recognized as targets for IgE antibodies

Until recently, glycan epitopes have not been documented by the WHO/IUIS Allergen Nomenclature Sub-Committee. This was in part due to scarce or incomplete information on these oligosaccharides, but also due to the widely held opinion that IgE to these epitopes had little or no relevance to allergic symptoms. Most IgE-binding glycans recognized up to 2008 were considered to be "classical" cross-reactive carbohydrate determinants (CCD) that occur in insects, some helminths and throughout the plant kingdom. Since 2008, the prevailing opinion on lack of clinical relevance of IgE-binding glycans has been subject to a reevaluation. This was because IgE specific for the mammalian disaccharide galactose-alpha-1,3-galactose (alpha-gal) was identified as a cause of delayed anaphylaxis to mammalian meat in the United States, an observation that has been confirmed by allergists in many parts of the world. Several experimental studies have shown that oligosaccharides with one or more terminal alpha-gal epitopes can be attached as a hapten to many different mammalian proteins or lipids. The classical CCDs also behave like haptens since they can be expressed on proteins from multiple species. This is the explanation for extensive in vitro cross-reactivity related to CCDs. Because of these developments, the Allergen Nomenclature Sub-Committee recently decided to include glycans as potentially allergenic epitopes in an adjunct section of its website (www.allergen.org). In this article, the features of the main glycan groups known to be involved in IgE recognition are revisited, and their characteristic structural, functional, and clinical features are discussed.

Update on latex allergy: New insights into an old problem

Despite the efforts made to mitigate the consequences of this disease, natural rubber latex allergy (NRLA) continues to be a global health problem and is still considered one of the main worries in the working environment in many countries throughout the world. Due to thousands of products containing latex, it is not surprising that the current statistics suggest that prevalence remains high among healthcare workers and susceptible patients. In developed countries, reduction in the prevalence of IgE-mediated allergy to latex proteins from gloves may lead to lax attention by health care personnel. On the other hand, this situation is different in developing countries where there is a lack of epidemiological data associated with a deficit in education and awareness of this issue. The aim of this review is to provide an update of the current knowledge and practical recommendations regarding NRLA by allergologists from different parts of the world with experience in this field.

Basophil activation testing in occupational respiratory allergy to low molecular weight compounds

PURPOSE OF REVIEW

There is an unmet need for better immunological tests in cases of suspected occupational asthma to many workplace chemicals; here we consider the basophil activation test (BAT), a potential alternative to the detection of specific IgE antibodies.

RECENT FINDINGS

BAT is fairly widely used in general allergy services; and there is increasing experience of its use in the diagnosis of occupational allergy to low molecular weight agents and chemicals including wood dusts, persulphates, antibiotics and latex.

SUMMARY

There is potential for BAT to become a useful tool in the clinical consideration of occupational asthma and of its mechanisms, and even to take a place in a Bayesian-based diagnostic algorithm. Further development will only occur if specialist centres with appropriate facilities, and preferably in collaboration, contemplate its use.

Hevea latex-associated allergies: piecing together the puzzle of the latex IgE reactivity profile

Introduction: IgE-mediated Hevea latex allergy and associated food-allergies constitute a significant health issue with serious consequences of diagnostic error. Hence, there is a need for more reliable confirmatory diagnostics.Areas covered: Here, we summarize the major limitations of conventional tests using native extracts and describe how piecing together the IgE reactivity profile can benefit correct diagnosis in difficult cases in whom conventional tests yield equivocal or negative results. A diagnostic algorithm integrating traditional sIgE and component-resolved diagnosis (CRD) is presented.Expert opinion: Moreover, it is clear that the discoveries in the field of the Hevea latex proteome will contribute to our understandings and accurate approach of sometimes complex cross-reactivity phenomena that extend beyond the 'latex-fruit syndrome.'

New developments in work-related asthma

INTRODUCTION

Work-related asthma includes two subtypes: occupational asthma or asthma caused by specific agents (sensitizers or irritants) in the workplace, and work-exacerbated asthma or pre-existing asthma worsened by workplace exposures. Areas covered: This review provides an update on the definitions and the clinical features of the different work-related asthma subtypes as well as new insights into their etiology and the pathophysiological mechanisms involved. The diagnosis of work-related asthma should be made on objective basis using a constellation of clinical, physiologic and allergologic tests. Specific inhalation challenge with the suspected occupational agent(s) remains as the reference standard for diagnosis. A literature search was performed using the following terms: work-related asthma, occupational asthma, work-exacerbated asthma, irritant-induced asthma and etiological agents. Expert commentary: Studies focusing on the biological effects and mechanisms of environmental exposures in the development of sensitizer-induced or irritant-induced asthma in various workplace settings are of greatest interest. An integrative approach that combines clinical parameters with component-resolved diagnosis as well as inflammatory biomarkers appears to be very promising. Occupational allergy provides a good opportunity to understand the complex relationships between exposure to allergens in the workplace, interaction with genes and the co-exposures to other factors in the working environment.

Quantification of specific IgE antibodies in immediate drug hypersensitivity: More shortcomings than potentials?

BACKGROUND

For many physicians, quantification of serum drug-specific IgE (sIgE) antibodies constitutes the first measure in the diagnostic approach of immediate drug hypersensitivity reactions (IDHR).

AIM

To review the accuracy and limitations of the main drug-sIgE tests, especially those that are commercially available.

METHODS

A literature search was conducted, using the key-words allergy, diagnosis, drugs, hypersensitivity, specific IgE antibodies; this was complemented by the authors' own experience.

RESULTS

The drugs that have mostly been studied appeared to be β-lactam antibiotics, neuromuscular blocking agents (NMBA) and morphine, the latter as a biomarker for sensitisation to substituted ammonium structures that constitute the major epitope of NMBA. For β-lactams sensitivity and specificity varied between 0-85% and 52-100%, respectively. For NMBA, sensitivity and specificity varied between 38.5-92% and 92-100%, respectively. With respect to sIgE to morphine it appears this drug to be a sensitive biomarker for sensitisation to rocuronium and suxamethonium but not for atracurium. However, sIgE morphine should not be applied in isolation to diagnose IDHR to NMBA nor opiates.

CONCLUSIONS

Although drug-sIgE assay can provide valuable information they should not be performed in isolation to establish correct diagnosis, as their predictive value is not per se absolute. Larger comprehensive studies are urgently required to determine the accuracy of drug-sIgE assays.

Identification and practical management of latex allergy in occupational settings

Allergy to natural rubber latex (NRL) from Hevea brasiliensis is a relevant occupational health hazard. The use of gloves and products manufactured with latex and environmental allergen exposure in the work environment are risks factors for the development of occupational allergy among different job categories. Healthcare workers have been the most commonly affected, but other professions with exposure to latex products such as hairdressers, cleaners, food handlers and those making natural rubber latex (NRL) products are also at risk of developing occupational allergy. Clinical manifestations of IgE-mediated latex allergy can range from troublesome skin disorders to life-threatening systemic reactions. It is very important to identify the occupational allergic diseases in their early stages in order to implement avoidance strategies. For this purpose, the interventions for prevention should emphasize the importance of latex allergy awareness and surveillance among exposed workforces.

CD 63 Cell Expression Detected by Flow-Cytometric Determination and Basophil Activation in Allergic Patients

Flow cytometry analysis of in vitro activated basophils (BATs) based on the detection of CD63 up-regulation on basophil membrane provides the physician and the clinical laboratory with a novel diagnostic approach, proposed as a promising alternative method for in vitro diagnosis of IgE and non-mediated reactions. We performed an optimized flow cytometric procedure to assess CD63 expression on activated basophils on twenty allergic patients, and compared the results with specific IgE determination (RAST) and skin testing (Prick test).

Reliability of basophil activation test using CD203c expression in diagnosis of pollen allergy

BACKGROUND

CD203c is a basophil surface marker and its expression is rapidly up-regulated after cross-linking of high-affinity immunoglobulin E (IgE) receptor (FcepsilonR1) by an allergen. CD203c basophil activation tests have been studied for the in vitro diagnosis of several allergic conditions. However, there is limited data about its diagnostic usefulness. The optimum allergen concentrations for stimulation and allergen specific cutoff values remain unknown for a number of allergens. This study was designed to investigate the efficacy of basophil activation test via CD203c in the diagnosis of pollen allergy.

METHODS

The CD203c basophil activation was determined in 31 allergic rhinitis patients with pollen allergy and 9 healthy nonatopic controls during the off-season. CD203c expression was evaluated using three-color staining protocol by flow cytometry.

RESULTS

After an in vitro stimulation with grass pollen extract, the CD203c assay clearly discriminated pollen-allergic patients from controls (p < 0.001). A dose-dependent increase in the percentages of CD203c-activated basophils was shown in rhinitis patients with pollen allergy (p < 0.001). The sensitivity and specificity was 100% and optimal cutoff values were 14.05 and 10.05% with 45.1 and 4.5 μg/mL Phl p 5 stimulation, respectively. Although the specificity was also 100%, the sensitivity was 93 and 87% and the cutoff values were 5.40 and 5.35% with 4.5 × 10(-4) and 4.5 × 10(-5) micrograms/mL Phl p 5 stimulation, respectively.

CONCLUSION

The CD203c basophil activation test seems to be a reliable tool in the diagnosis of grass pollen allergy. It could be used when conventional diagnostic tests fail or can not be performed.

Monitoring honeybee venom immunotherapy in children with the basophil activation test

BACKGROUND

New in vitro methods are essential for developing better follow-up criteria for venom immunotherapy (VIT).

METHODS

Thirty-one children with a history of honeybee venom-induced systemic anaphylaxis were included in this prospective, single-blinded study. The basophil CD63 activation test (BAT) was assessed before starting VIT, at the end of the build-up phase (day 5), 6 months later, and after 2-4 yr of VIT.

RESULTS

Basophil CD63 activation test allowed identification of the culprit insect in 74% of honeybee venom-allergic children. In comparison, IgE reactivity was single positive in only 52% of children. Five days after starting VIT, BAT was highly comparable to before VIT. However, after 6 months and further after 2-4 yr of VIT, a significant and approximately fourfold decrease was demonstrated in CD63 response at sub-maximal 0.1 μg/ml allergen concentration, which mainly represents cellular sensitivity. No such differences were found at a higher 1 μg/ml of allergen concentration. Person-to-person analyses showed that after 2-4 yr of VIT, a marked CD63 decrease was evident in 85% of children. In addition, elevated basophil sensitivity measured before VIT was associated with the appearance of side effects observed during the build-up phase of VIT.

CONCLUSION

Basophil CD63 allergen-specific sensitivity seems to be a promising tool for monitoring protective immune response in honeybee VIT.

A granular variant of CD63 is a regulator of repeated human mast cell degranulation

BACKGROUND

Mast cells are secretory immune cells whose degranulation can provoke acute allergic reactions. It is presently unclear, however, whether an individual mast cell can repeatedly degranulate or turns dysfunctional after a single antigen stimulus. This work thus aims to better define the mast cell life cycle, with particular focus on new target structures for therapeutic or diagnostic approaches in allergy.

METHODS

Monoclonal antibodies were raised against degranulated cord blood-derived human mast cells. A subset of these antibodies that exclusively recognized degranulated mast cells, but did not cross-react with quiescent mast cells or other hematopoietic cell types, became key reagents in subsequent experiments.

RESULTS

We identified a granular variant of tetraspanin CD63 as an exclusive molecular marker of degranulated human mast cells. Mutant analyses indicate that a cysteine cluster around residue C170 and protein glycosylation at residue N172 account for the antibody specificity. Here, we show that mast cells, which underwent an initial FcεRI-mediated degranulation, can be degranulated for at least another cycle in vitro. Repeated degranulation, however, requires an IgE/antigen stimulus that differs from the preceding one. Furthermore, the new variant-specific anti-CD63 antibodies effectively impair repeated cycles of mast cell degranulation.

CONCLUSION

Our findings indicate that mast cells are stable, multiple-use cells, which are capable of surviving and delivering several consecutive hits. Surface expression of the novel CD63 variant is a distinguishing feature of such primed cells. Reagents directed against this molecular hallmark may thus become valuable diagnostic and therapeutic agents.

Component-resolved diagnosis from latex allergy by microarray

BACKGROUND

A positive specific IgE (sIgE) result for latex does not always mirror the clinical situation and is frequently found in individuals without overt latex allergy.

OBJECTIVE

We sought to investigate the potential of component-resolved diagnosis (CRD) of latex allergy by microarray and to assess whether the technique allows discriminating genuine allergy from asymptomatic sensitization.

METHODS

Twenty-six healthy controls without a history of latex allergy with a negative latex sIgE and skin test, 22 latex-allergic patients with a compelling history of latex allergy with a positive latex sIgE and prick test and 20 latex-sensitized individuals with a frequent asymptomatic exposure to natural rubber latex-containing devices with a negative latex skin test but a positive sIgE were also included. CRD was performed with the ImmunoCAP ISAC microarray and traditional singleplexed ImmunoCAP.

RESULTS

In all patients, the diagnosis of latex allergy could be established by the combination of recombinant latex components present on the microarray (Hev b 1, Hev b 3, Hev b 5 and Hev b 6.02). Over three-quarters of our patients were sensitized for Hev b 5 and/or Hev b 6.02. Some patients also displayed reactivity for Hev b 1 and/or Hev b 3. In contrast, none of the individuals sensitized to natural rubber latex or control individuals demonstrated IgE reactivity for rHev b 1, rHev b 3, rHev b 5 or rHev b 6.02. Three-quarters of the patients sensitized to latex displayed a positive microarray result for recombinant latex profilin (rHev b 8). In contrast to the results obtained by traditional ImmunoCAP for bromelain, almost no sensitization for cross-reactive carbohydrates was demonstrated by bromelain spotted on the microarray. CRD by traditional singleplexed ImmunoCAP showed highly comparable results.

CONCLUSION

CRD by microarray is a reliable tool for diagnosing latex allergy. In addition, the technique allows discrimination between genuine allergy and sensitization. CRD by microarray can improve the diagnosis of IgE-mediated latex allergy by discriminating between genuine allergy and sensitization. CRD by microarray is a reliable tool to diagnose latex allergy. In addition, the technique allows discrimination between a genuine allergy and simple sensitization.

Cross-reactive carbohydrate determinants strongly affect the results of the basophil activation test in hymenoptera-venom allergy

BACKGROUND

In hymenoptera-venom allergy, sera of up to 60% of patients show in vitro reactivity to honeybee venom (HBV) and yellow jacket venom (YJV). This phenomenon is mainly caused by specific IgE (sIgE) against cross-reactive carbohydrate determinants (CCD). Whether or not these antibodies can induce clinical symptoms is a longstanding debate.

OBJECTIVE

The aim of this study was to investigate the biological activity of CCD-sIgE and the suitability of the basophil activation test (BAT) in hymenoptera venom-allergic patients having CCD-sIgE.

METHODS

The biological activity of CCD-sIgE was analysed by application of native and CCD-depleted YJV and HBV in BAT with the blood of 62 hymenoptera venom-allergic patients and 16 non-allergic controls. According to results of intracutaneous skin tests (IC) with YJV and HBV and the existence of CCD-sIgE, patients were classified into six subgroups.

RESULTS

In patients with mono-positive IC and CCD-sIgE, and thus double-positive sIgE, BAT with native venoms was also double positive in up to 67% of the patients. In contrast, BAT with CCD-depleted venoms was positive only with the IC-positive venom. However, activation of basophils with the IC-negative venom was significantly lower compared with the IC-positive one. In IC mono-positive patients without CCD-sIgE, BAT was mono-positive with the IC-positive venom in the native and in the CCD-depleted form. CCD-positive patients with double-positive IC were a heterogeneous group, with the majority of CCD-positive patients also being double positive with the native forms of both venoms but mono-positive with the CCD-depleted ones.

CONCLUSIONS

In vitro BAT clearly demonstrates biological activity of CCD-sIgE. However, because most of the patients showed a mono-positive IC and activation of basophils with the IC-negative venom was significantly lower compared with the IC-positive one, the present data suggest that CCD-sIgE is clinically irrelevant in these patients.

Validation of a flow cytometry based chemokine internalization assay for use in evaluating the pharmacodynamic response to a receptor antagonist

Pharmacodynamic assays are important in clinical trial design to investigate the relationship between drug concentration (pharmacokinetics) and drug "effect' or biological activity. Increasingly flow cytometry is being used to examine the pharmacodynamic effect of new drug entities. However, to date, the analytical validation of cytometry based assays is limited and there is no suitable guidance for method validation of flow cytometry-based pharmacodynamic assays. Here we report the validation of a flow cytometry-based chemokine internalization assay for use in evaluating the effect of a receptor antagonist in clinical trials. The assay method was validated by examining the stability of the reagent, assay robustness, sensitivity, repeatability and reproducibility precision. Experimental results show the assay reagent was stable over 26 weeks. The assay demonstrated a sensitivity to distinguish 0.005 μg/ml of a CCR2 antagonist with a %CV of 13.3%. The intra-assay repeatability was less than 15% with an inter-assay repeatability of less than 20%. In vivo study results demonstrated that the assay was consistent and a reliable measure of antagonist activity.

Differential response of human basophil activation markers: a multi-parameter flow cytometry approach

BACKGROUND

Basophils are circulating cells involved in hypersensitivity reactions and allergy but many aspects of their activation, including the sensitivity to external triggering factors and the molecular aspects of cell responses, are still to be focused. In this context, polychromatic flow cytometry (PFC) is a proper tool to investigate basophil function, as it allows to distinguish the expression of several membrane markers upon activation in multiple experimental conditions.

METHODS

Cell suspensions were prepared from leukocyte buffy coat of K2-EDTA anticoagulated blood specimens; about 1500-2500 cellular events for each tested sample, gated in the lymphocyte CD45dim area and then electronically purified as HLADRnon expressing/CD123bright, were identified as basophilic cells. Basophil activation with fMLP, anti-IgE and calcium ionophore A23187 was evaluated by studying up-regulation of the indicated membrane markers with a two-laser six-color PFC protocol.

RESULTS

Following stimulation, CD63, CD13, CD45 and the ectoenzyme CD203c up-regulated their membrane expression, while CD69 did not; CD63 expression occurred immediately (within 60 sec) but only in a minority of basophils, even at optimal agonist doses (in 33% and 14% of basophils, following fMLP and anti-IgE stimulation respectively). CD203c up-regulation occurred in the whole basophil population, even in CD63non expressing cells. Dose-dependence curves revealed CD203c as a more sensitive marker than CD63, in response to fMLP but not in response to anti-IgE and to calcium ionophore.

CONCLUSION

Use of polychromatic flow cytometry allowed efficient basophil electronic purification and identification of different behaviors of the major activation markers. The simultaneous use of two markers of activation and careful choice of activator are essential steps for reliable assessment of human basophil functions.

Analysis of basophil activation by flow cytometry in pediatric house dust mite allergy

Detection of allergen-induced basophil activation by flow cytometry has been shown to be a useful tool for allergy diagnosis. The aim of this study was to assess the potential of this technique for the diagnosis of pediatric house dust mite allergy. Quantification of total and specific IgE and basophil activation test were performed to evaluate mite allergic (n = 24), atopic (n = 23), and non-allergic children (n = 9). Allergen-induced basophil activation was detected as a CD63-upregulation. Receiver operating characteristics (ROC) curve analysis was performed to calculate the optimal cut-off value of activated basophils discriminating mite allergic and non-allergic children. ROC curve analysis yielded a threshold value of 18% activated basophils when mite-sensitized and atopic children were studied [area under the curve (AUC) = 0.99, 95% confidence interval (CI) = 0.97-1.01, p < 0.001] with a sensitivity and specificity of 96% for 16 microg/ml mite extract. Analysis of the data obtained with 1.6 microg/ml mite extract defined a cut-off value of 8% activated basophils (AUC = 0.96, 95% CI = 0.91-1.01; p < 0.001) with a sensitivity of 82% and specificity of 100%. Comparison between mite allergic and non-allergic children produced a cut-off of 8% activated basophils (AUC = 1.0) with 16 microg/ml allergen extract and a sensitivity and specificity of 100%. The same threshold and specificity values were obtained with 1.6 microg/ml extract (AUC = 97%, 95% CI = 0.92-1.02; p < 0.001) but sensitivity decreased to 83%. Two atopic children showed negative skin prick and basophil activation tests and high specific IgE (>43 kU/l) values for Dermatophagoides pteronyssinus allergen. They also showed positive prick (wheal diameter >1.0 cm) and basophil activation (>87%) tests and high specific IgE (>100 kU/l) with shrimp allergen. Shrimp sensitization was demonstrated by high levels of Pen a 1-specific IgE (>100 kU/l). Cross-reactivity between mite and shrimp was confirmed by fluorescence enzyme immunoassay (FEIA-CAP) inhibition study in these two cases. This study demonstrated that the analysis of allergen-induced CD63 upregulation by flow cytometry is a reliable tool for diagnosis of mite allergy in pediatric patients, with sensitivity similar to routine diagnostic tests and a higher specificity. Furthermore, this method can provide additional information in case of disagreement between in vivo and in vitro test results.

Anaphylaxis during anaesthesia: diagnostic approach

Correct management of anaphylaxis during anaesthesia requires a multidisciplinary approach with prompt recognition and treatment of the acute event by the attending anaesthesiologist, and subsequent determination of the responsible agent(s) with strict avoidance of subsequent administration of all incriminated and/or cross-reacting compounds. However, correct identification of the causative compound(s) and safe alternatives is not always straightforward and, too often, not done. This review is not intended to discuss acute management of anaesthesia-related anaphylaxis but summarizes the major causes of anaphylaxis during anaesthesia and the diagnostic approach of this rare but potentially life-threatening complication. Apart from general principles about the diagnostic approach, history taking and importance of tryptase quantification, more specific confirmatory diagnostic procedures are organized on the basis of the major causes of perioperative anaphylactic reactions.

Flow cytometry for basophil activation markers: the measurement of CD203c up-regulation is as reliable as CD63 expression in the diagnosis of cat allergy

The flow cytometric basophil activation test (BAT), based on the detection of allergen-induced CD63 expression, has been proved effective in the diagnosis of various IgE-mediated allergies. However, there is not yet consensus about the suitability of CD203c expression as a specific basophil activation marker and its diagnostic reliability. The goal of the present study was to compare measurement of CD63 and CD203c expression using BAT in a model of cat allergy and to determine optimal experimental conditions for both markers. Heparinized whole blood samples from 20 cat allergic patients and 19 controls were incubated with Fel d1 (relevant allergen) or anti-FcepsilonRI (positive control) either in IL-3 or IL-3-free conditions. An optimal gating of basophils was achieved in triple staining protocols: anti-IgE PE/anti-CD45 PerCP/anti-CD63 FITC or anti-IgE FITC/anti-CD45 PerCP/anti-CD203c PE. We demonstrated that IL-3 significantly enhanced CD63-induced expression by basophils obtained from cat allergic patients in response to Fel d1. Sensitivity was found to be 100%. The CD203c protocol, when performed under IL-3-free conditions, also demonstrated 100% sensitivity. Only one of the control subjects was positive in both tests. In conclusion, using well-defined experimental conditions, the measurement of CD203c up-regulation on basophils in response to specific allergens is as reliable as CD63-BAT for the in vitro diagnosis of patients with IgE-mediated allergy.

Flow-assisted allergy diagnosis: current applications and future perspectives

Physicians predominantly rely upon quantification of serum-specific immunoglobulin E (IgE) and/or skin test to confirm clinically suspected IgE-mediated allergy. However, for various reasons, identification of the offending allergen(s) and potentially cross-reactive structures is not always straightforward. Flow-assisted allergy diagnosis relies upon quantification of alterations in the expression of particular basophilic activation markers. Actually, upon challenge with a specific allergen, basophils not only secrete quantifiable bioactive mediators but also upregulate the expression of different markers which can be detected efficiently by flow cytometry using specific monoclonal antibodies. Currently, the technique has been applied in the investigation of IgE-mediated allergy caused by classical inhalant allergens, food, Hevea latex, hymenoptera venoms and drugs. It is also appreciated; the technique proves valuable in the diagnosis of non-IgE-mediated (anaphylactoid) reactions such drug hypersensitivity and the detection of autoantibodies in certain forms of chronic urticaria. This review will not address immunologic features, characteristics and general pitfalls of flow-assisted analysis of in vitro-activated basophils as summarized elsewhere. After a recapitulation of the principles and some specific technical issues of flow-assisted analysis of in vitro-activated basophils, we principally focus on the current clinical and research applications of the basophil activation tests. Personal experience of both research groups is provided, where appropriate. Finally, a viewpoint on how the field might evolve in the following years is provided.

Comparision of two-flow cytometry methods for basophil degranulation in patients sensitized to grass pollen

BACKGROUND

Two-flow cytometry methods for quantification of degranulated basophil after allergen-specific activation were discussed. The methods are discerned by used membrane receptors--FcepsilonRI or IL-3Ralpha Our goal was to evaluate the diagnostic potential of the methods and to correlate them to allergen-specific IgE detection and skin prick test (SPT).

METHODS

Patient's and control's groups were studied with Bulgarian grass pollen allergen B1 simultaneously by flow cytometry kits: Basotest and BD FastImmune test. Allergy diagnosis was based on clinical history and SPT. The determination of specific IgE was performed by ELISA--RIDASCREEN.

RESULTS

There were no significant differences between the patient's results from Basotest and FastImmune (P>0.05). A significant correlation between values, analyzed by Basotest and by FastImmune was found (r=0.88). The sensitivity and specificity of the Basotest, FastImmune, specific IgE and SPT were 85%, 72%, 92% and 92% sensitivity and 100%, 92%, 100% and 85% specificity respectively. The efficiency was between 82% and 97%. There were a significant correlation between the specific IgE and flow cytometry tests: tau=0.92 (Basotest) and tau=0.71 (FastImmune) and a moderate significant correlation between the SPT and the in vitro tests: tau=0.26 (Basotest) and tau=0.31 (FastImmune).

CONCLUSION

The successful use of the Bulgarian grass pollen allergen B1 and both flow cytometry tests was presented. These methods could be as specific tools for IgE-mediated diagnosis especially FastImmune in the case of low IgE receptor expression.

R406, an orally available spleen tyrosine kinase inhibitor blocks fc receptor signaling and reduces immune complex-mediated inflammation

Recent compelling evidence has lead to renewed interest in the role of antibodies and immune complexes in the pathogenesis of several autoimmune disorders, such as rheumatoid arthritis. These immune complexes, consisting of autoantibodies to self-antigens, can mediate inflammatory responses largely through binding and activating the immunoglobulin Fc receptors (FcRs). Using cell-based structure activity relationships with cultured human mast cells, we have identified the small molecule R406 [N4-(2,2-dimethyl-3-oxo-4H-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine] as a potent inhibitor of immunoglobulin E (IgE)- and IgG-mediated activation of Fc receptor signaling (EC(50) for degranulation = 56-64 nM). Here we show that the primary target for R406 is the spleen tyrosine kinase (Syk), which plays a key role in the signaling of activating Fc receptors and the B-cell receptor (BCR). R406 inhibited phosphorylation of Syk substrate linker for activation of T cells in mast cells and B-cell linker protein/SLP65 in B cells. R406 bound to the ATP binding pocket of Syk and inhibited its kinase activity as an ATP-competitive inhibitor (K(i) = 30 nM). Furthermore, R406 blocked Syk-dependent FcR-mediated activation of monocytes/macrophages and neutrophils and BCR-mediated activation of B lymphocytes. R406 was selective as assessed using a large panel of Syk-independent cell-based assays representing both specific and general signaling pathways. Consistent with Syk inhibition, oral administration of R406 to mice reduced immune complex-mediated inflammation in a reverse-passive Arthus reaction and two antibody-induced arthritis models. Finally, we report a first-inhuman study showing that R406 is orally bioavailable, achieving exposures capable of inhibiting Syk-dependent IgE-mediated basophil activation. Collectively, the results show R406 potential for modulating Syk activity in human disease.

Perioperative anaphylaxis from locally applied rifamycin SV and latex

A patient developed severe anaphylaxis during irrigation of a wound with rifamycin SV. The temporal relationship between application of rifamycin SV, the positive skin test and basophil activation test for rifamycin SV strongly supported diagnosis of anaphylaxis from the locally applied antibiotic. However, after operation the patient had two anaphylactic reactions with pruritus, urticaria and angio-oedema after routine care by a nurse, and these were probably caused by natural rubber latex. This case report has several messages. First, it is not widely appreciated that topically applied drugs and related compounds can elicit life-threatening anaphylaxis. Second, it illustrates patients can present with more than one allergy. Finally, it provides an opportunity to summarize the applications of flow cytometry-assisted quantification of in vitro activated basophils in diagnosing the cause of anaphylaxis during anaesthesia.

Coriander anaphylaxis in a spice grinder with undetected occupational allergy

BACKGROUND

Anaphylaxis after ingestion of spices as a result from occupational sensitization remains anecdotal. We describe a patient, working in a spice factory, with anaphylaxis from coriander in a meal. He also demonstrated urticaria, angio-edema, rhinoconjunctivitis and bronchospasm during handling coriander and fenugreek.

OBJECTIVE

To determine the mechanism of the anaphylactic reaction and to evaluate cross-reactivity between both botanically unrelated spices.

METHODS

Investigations comprised quantification of total and specific IgE by Immuno-CAP FEIA, skin testing, basophil activation experiments by flow-assisted determination of CD63 expression in the patient and 3 healthy controls. Immuno-CAP inhibition experiments were applied to investigate cross-reactivity.

RESULTS

Specific IgE, skin tests and basophil activation tests were clearly positive in the patient, whereas they remained negative in controls. No cross-reactivity between fenugreek and coriander was demonstrable by inhibition experiments.

CONCLUSIONS

The clinical manifestations in temporal relationship to ingestion of coriander and handling of coriander and/or fenugreek, the positive specific IgE results, skin tests and basophil activation assays support the diagnosis of allergy to both spices. History suggests sensitization by occupational exposure.

Detection of Anisakis simplex-induced basophil activation by flow cytometry

BACKGROUND

Laboratory diagnosis of anisakidosis is based on specific serum IgE detection. Recently, detection of allergen-induced basophil activation by flow cytometry has been proposed as a valuable tool for allergy diagnosis.

OBJECTIVE

To evaluate if detection of Anisakis-induced basophil activation by flow cytometry is a useful tool in the diagnosis of Anisakis allergy.

METHODS

Patients with Anisakis allergy (A.s.+, n = 37), patients reporting chronic urticaria or abdominal pain unrelated to fish ingestion (A.s.-, n = 51), and healthy controls (n = 12) were studied. Specific IgE to Anisakis simplex (A. simplex) was quantified with CAP-FEIA method, and basophil activation test was performed with three different concentrations of an Anisakis crude extract. Basophil gating was performed with CD123 and HLA-DR, and cellular activation was measured with CD63.

RESULTS

A.s.+ patients showed significantly higher age and total IgE levels than did the A.s.- patients. Specific IgE to A. simplex correlated with the activated basophil percentages obtained with 15 microg/mL (r = 0.80; P < 0.001), 1.5 microg/mL (r = 0.84; P < 0.001), and 0.15 microg/mL (r = 0.82; P < 0.001) of A. simplex crude extract. Nine individuals (3 in the A.s.+ group and 6 in the A.s.- group) were nonresponders to basophil stimulation with anti-IgE. Five A.s.- patients showed positive IgE values to A. simplex while the basophil activation test was negative. According to the receiver operating characteristics curves performed between A.s.+ vs. A.s.- and A.s.+ vs. healthy controls, the cutoff for a positive basophil activation test was >or=21% (specificity = 96%, sensitivity = 100%), and 16% (sensitivity and specificity of 100%) respectively. When nonresponders were included in the A.s.+ vs. A.s.- analysis, sensitivity decreased to 95%. Multivariate logistic analysis showed that the specific basophil activation was a factor independently associated with clinical symptoms of A. simplex allergy.

CONCLUSIONS

Detection of A. simplex-induced basophil activation by flow cytometry is a useful laboratory technique for the diagnosis of anisakidosis, supplementing specific IgE determinations.

Haemodialysis-associated anaphylactic and anaphylactoid reactions

Anaphylactic and anaphylactoid reactions related to haemodialysis have been increasingly described for almost 3 decades. The majority of these cases used to occur with ethylene oxide sterilized, and complement-activating cellulose membranes. However, a considerable number of publications have focused on polyacrylonitrile AN69 high flux membranes, angiotensin converting enzyme inhibitors and iron as other important causes of potentially severe haemodialysis-related anaphylactoid reactions. Clinical manifestations vary considerably and generally do not allow differentiation between IgE-mediated anaphylaxis and anaphylactoid reactions (e.g. from nonspecific mediator release). Successful management of these patients requires multidisciplinary approach and involves prompt recognition and treatment by the attending physician, and identification of the offending agent(s) with subsequent avoidance of the incriminated compound(s). This review focuses on some major causes of anaphylactoid and anaphylactic reactions during haemodialysis. Special consideration is given to the therapeutic and diagnostic approach.

Lysis with Saponin improves detection of the response through CD203c and CD63 in the basophil activation test after crosslinking of the high affinity IgE receptor FcepsilonRI

BACKGROUND

The basophil activation test (BAT), in which translocation of markers to the surface of blood basophils is measured in response to allergen by flow cytometry, is a rapid assay that is gaining popularity. Two markers are currently being evaluated for the BAT; CD63 and the lineage-specific CD203c. In a recent report, detection of CD203c after lysis with Saponin was shown to be superior to detection of CD63 after lysis with formic acid. We wanted to compare a) lysis with formic acid and lysis with Saponin, b) the response through CD203c and CD63, and c) the definition 10% activated cells above background with the probability binning metric T(chi) > 4, on sets of data generated with blood basophils stimulated with varying concentrations of anti-FcepsilonRI antibody.

METHODS

Blood from volunteers was incubated with serial logarithmic dilutions of anti-FcepsilonRI and subsequently with antibodies to CD203c PE and CD63 FITC. Sets of samples set up in parallel were lysed with either Saponin based Whole Blood Lysing reagent or with formic acid based Immunoprep/Q-prep. Samples were acquired on a FACS Calibur, but were compensated and analysed offline. Responders were defined as persons who had 10% or more activated basophils above background, or a T(chi) > 4, for two consecutive dilutions of anti-FcepsilonRI antibody.

RESULTS

More basophils (median 1164 vs. median 397) and better discrimination of upregulated CD203c and CD63 amongst responders were obtained after lysis with Saponin than after lysis with formic acid. We suggest that CD203c may be a more sensitive marker for the BAT than CD63, as 6/11 responders were found with CD203c, compared with 3/11 with CD63. Most responders (7/11) were identified with probability binning.

CONCLUSION

A combination of lysis with Saponin and the markers CD203c and CD63 computed by probability binning may be the most sensitive method of detecting activation of basophils after stimulation through FcepsilonRI.

The flow-cytometric determination of basophil activation induced by aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) is useful for in vitro diagnosis of the NSAID hypersensitivity syndrome

BACKGROUND

Hypersensitivity reactions to non-steroidal anti-inflammatory drugs (NSAIDs), manifested by cutaneous symptoms and/or airway manifestations represent 20-25% of all hypersensitivity reactions to drugs. Today, it is still claimed that no in vitro diagnostic tests exist for that condition and that the only way to confirm the diagnosis is a provocation challenge.

OBJECTIVE

The objective of this study was to assess whether NSAIDs may provoke blood basophil activation in vitro in such patients, as detected by a flowcytometric technique.

METHODS

Sixty NSAID hypersensitive patients (38 with cutaneous, 20 with airway and two with cutaneous and airway symptoms) and 30 control patients (15 asthmatics) were selected. Their hypersensitivity was confirmed by documented history indicating at least two clinical episodes to two or more different NSAIDs or by positive oral provocation challenge. Isolated buffy coat leukocytes were stimulated in vitro with aspirin, paracetamol, metamizol, diclofenac, and naproxen. The percentage of activated basophils was evaluated by an anti-CD63.

RESULTS

Aspirin showed a sensitivity of 43.3%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 99.4%. For the other NSAIDs, the sensitivity and specificity values were: for paracetamol 11.7% and 100%, for metamizol 15% and 100%, for diclofenac 43.3% and 93.3% and for naproxen 54.8% and 74.1%. When considering the first four NSAIDs, the global sensitivity raised to 63.3% and specificity to 93.3%. If the number of tests is to be limited for practical reasons, the combination of acetylsalicylic acid and diclofenac at two concentrations yields a sensitivity of 58.3% and a specificity of 93.3%.

CONCLUSIONS

Flowcytometric determinations of basophil activation following stimulation with NSAIDs show a high sensitivity (60-70%) with specificity above 90%. So this test may help avoiding some cumbersome and dangerous provocation challenges.

Flow cytometric analysis of in vitro activated basophils, specific IgE and skin tests in the diagnosis of pollen-associated food allergy

BACKGROUND

Specific immunoglobulin E (IgE) and commercially available skin prick tests have been demonstrated to be unreliable methods to diagnose pollen-associated food allergy. To evaluate the predictive value of the basophil activation test (BAT) in pollen-associated food allergy, the apple-mediated oral allergy syndrome (OAS) in patients with birch pollinosis was chosen as a representative model.

METHODS

Patients with birch pollen allergy and a history of apple-mediated OAS (OAS(+), n = 29), patients with birch allergic without OAS (OAS(-), n = 22), and healthy controls (HC, n = 10) without birch pollen allergy and OAS were included. Apple IgE was quantified by the CAP FEIA method. Skin prick tests were performed with a Jonagold apple extract. Flow cytometric analysis of basophils activated with the same Jonagold extract was based on double staining with anti-IgE/anti-CD63 monoclonal antibodies.

RESULTS

Comparison between OAS(+) subjects and HC showed sensitivities and specificities of 96% and 100% for apple IgE and 88% and 100% for the apple skin prick test, respectively. For the BAT, sensitivity and specificity were 100%. In contrast, when nonresponders on the BAT were considered, sensitivity decreased to 90%. In a separate analysis between OAS(+) and OAS(-) subjects, specificities decreased to 30% for apple IgE and to 80% for the apple skin test, respectively. The BAT reached a sensitivity of 88% and a specificity of 75%.

CONCLUSION

Flow cytometry-assisted quantification of in vitro basophil activation seems to be a reliable instrument in the diagnosis of this model of pollen-associated food allergy. In addition, this study reemphasizes that the specificity of diagnostic allergy tests decreases considerably when, apart from HC, control individuals with cross-reactive antibodies are included.

Confirmation of the diagnosis of natural rubber latex allergy by the Basotest method

BACKGROUND

The flow cytometry CD63-based basophil activation test (Basotest has already been validated for the diagnosis of immediate-type allergy such as venom, house dust mite or cypress pollen allergies. The aim of this study was to evaluate the performance (specificity and sensitivity) of Basotest in the diagnosis of natural rubber latex allergy.

METHODS

We included 46 latex allergic patients (clinical symptoms of latex allergy, positive latex skin prick tests and/or latex specific IgE) and 33 control subjects and performed Basotest on all subjects.

RESULTS

The sensitivity and specificity of Basotest were 84.8 and 87.9%, respectively, when we considered the theoretic cut-off at 15% of CD63-positive cells. Using ROC curves, the optimal cut-off was evaluated at 22%, for which sensitivity and specificity were 79.3 and 96.7%, respectively.

CONCLUSION

The Basotest is a reliable test in addition to clinical history and tests already validated (such as skin prick tests and specific IgE) to confirm the diagnosis of natural rubber latex allergy.

A new combined test with flowcytometric basophil activation and determination of sulfidoleukotrienes is useful for in vitro diagnosis of hypersensitivity to aspirin and other nonsteroidal anti-inflammatory drugs

BACKGROUND

We assessed whether nonsteroidal anti-inflammatory drugs (NSAIDs) may provoke blood basophil activation in vitro in aspirin- and NSAID-hypersensitive patients, as detected by a flowcytometric technique using the CD63 marker--flowcytometric basophil activation test (FAST) assay--in addition to the sulfidoleukotriene (sLT) release--the cellular allergen stimulation test (CAST).

METHODS

Sixty aspirin- and/or NSAID-hypersensitive patients were studied. Thirty control patients without history and negative provocation challenge were also included. The percentage of activated basophils after in vitro stimulation with NSAIDs at 3 different concentrations was evaluated by an anti-CD63 phycoerythrin conjugate (FAST assay) and the amount of sLTs released in the cell supernatant by ELISA (CAST assay).

RESULTS

For aspirin, the FAST indicated a sensitivity of 41.7%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 99.4%; for paracetamol 11.7 and 100%, for metamizol 15 and 100%, for diclofenac 43.3 and 93.3%, and for naproxen 54.8 and 74.1%. Many patients showed positive tests to more than 1 NSAID. When considering the first 4 NSAIDs, the global sensitivity increased to 66.7%, while the specificity remained at 93.3%. The addition of the CAST results still increased the sensitivity up to 73.3%, but with a decrease of the specificity to 71.4%.

CONCLUSIONS

The FAST shows a high percentage of positive reactions, which may reach 60-70% when 4 NSAIDs are tested and even 88% when the test is performed within 1 month of the last clinical drug exposure and reaction. The test has a high specificity above 90%. The addition of sLT determinations yields additional information in a few isolated cases. It is suggested that this test, when properly used, may help avoid some cumbersome and dangerous provocation challenges.

Hypoallergenic variants of the major latex allergen Hev b 6.01 retaining human T lymphocyte reactivity

Hev b 6.01 is a major allergen of natural rubber latex with sensitization of 70-86% of latex glove-allergic subjects. Recently, we mapped the immunodominant T cell sites of Hev b 6.01 to the highly IgE-reactive hevein (Hev b 6.02) domain. Hev b 6.01 contains 14 cysteine residues with multiple disulphide bridges stabilizing tertiary conformation. With the goal of a standardized specific immunotherapy we developed hypoallergenic Hev b 6.01 mutants by site-directed mutagenesis of selected cysteine residues (3, 12, 17, and 41) within the Hev b 6.02 domain. Peptides corresponding to the Hev b 6.02 domain of two of the mutants were also synthesized. These mutants and peptide variants showed markedly decreased or ablated latex-allergic patient serum IgE binding by immunoblotting and ELISA. Basophil activation testing confirmed markedly decreased activation with successive cysteine substitutions of the mutants and complete abrogation with the Hev b 6.02 (Cys 3, 12, 17, 41 Ala) peptide. Retention of T cell reactivity is crucial for effective specific immunotherapy and all mutants and peptide variants maintained their latex-specific T cell reactivity. The ablated allergenicity but retained T cell reactivity of the Hev b 6.02 (Cys 3, 12, 17, 41 Ala) peptide suggests this peptide is a suitable candidate for inclusion in a latex immunotherapy preparation.