Microarray immunoassay: association of clinical history, in vitro IgE function, and heterogeneity of allergenic peanut epitopes

Correlation between skin prick test using commercial extract of cow's milk protein and fresh milk and food challenges

The skin prick test (SPT) is regarded as an important diagnostic measure in the diagnostic work-up of cow's milk protein allergy. It is not known whether commercial extracts have any advantage over fresh milk. The aims of the study were to (i) compare the diagnostic capacity of SPTs for the three main cow's milk proteins (alpha-lactalbumin, casein and beta-lactoglobulin) with fresh milk and (ii) determine a cut-off that discriminates between allergic and tolerant children in a controlled food challenge. A study was carried out on 104 children consecutively attending two paediatric allergy clinics for suspected cow's milk allergy. A clinical history, SPTs with fresh cow's milk and commercial extracts of its three main proteins and a challenge test were performed on all the children. A study of the validity of the prick test was also performed by taking different cut-off points for fresh milk and its proteins. Twenty-eight of 104 challenge tests (26.9%) were positive. At a cut-off point of 3 mm, fresh milk showed the greatest negative predictive value (98%), whereas casein showed the greatest positive predictive value (PPV, 85%). Calculation of 95% predicted probabilities using logistic regression revealed predictive decision points of 12 mm for lactalbumin, 9 mm for casein, 10 mm for beta-lactoglobulin and 15 mm for fresh cow's milk. We found that the greater the number of positive SPTs for milk proteins, the more likely the positive response to challenge. Having a positive SPT for all three milk proteins had PPV of 92.3% and would seem more clinically useful than any cut-off. Both fresh milk and cow's milk extract of the three main proteins could be useful in the diagnostic work-up of cow's milk allergy. Finding positivity to all three cow's milk proteins seems to be a simpler and more useful way of avoiding oral food challenges.

IgG and IgE avidity characteristics of peanut allergic individuals

The role of antibody avidity in allergy is poorly understood and there is no existing literature describing antibody avidity in food allergy. The main aim of this study was to investigate IgE and IgG avidity to a total peanut protein extract (TPPE) and purified Ara h 2 in a group of well-characterized peanut allergic individuals. Forty peanut allergic patients underwent a double-blind placebo-controlled low-dose peanut challenge, during which the severity of the patients' peanut allergy was scored. Serum peanut-specific IgE (psIgE) and IgG (psIgG) concentrations were measured for 37 individuals and the avidities of the same antibodies to a TPPE and purified Ara h 2 were determined using a thiocyanate ELISA method. Both IgE and IgG avidity to Ara h 2 showed weak positive correlations with challenge score [r = 0.459 (p = 0.012) and r = 0.486 (p = 0.003), respectively]. IgE avidity to TPPE showed a weak positive correlation with skin prick test results (SPT), r = 0.467 (p = 0.004) and there was an inverse relationship between the ratio of total IgE:psIgE and challenge score r = -0.561 (p < 0.001). No significant relationship was found between the ratios of IgE avidity:IgG avidity and challenge score or SPT. This is the first description of IgE and IgG avidity in peanut allergy, and it appears that the avidities of IgE and IgG antibodies to purified Ara h 2 are weakly related to the severity of peanut allergy (as measured by a challenge score).

The changing face of food hypersensitivity in an Asian community

BACKGROUND

Food allergy seems to be increasing in Asia as well as world-wide. Our aim was to characterize food protein sensitization patterns in a population of Asian children with possible food allergy.

METHODS

Children presenting to our allergy clinic over 3 years with symptomatic allergic disease and at least one specific food allergen sensitization documented on skin prick testing were included in the analysis.

RESULTS

Two hundred and twenty-seven patients fulfilled inclusion criteria. Ninety (40%) of the positive skin tests were positive to egg, 87 (39%) to shellfish, 62 (27.3%) to peanut, 30 (13.2%) to fish, 27 (11.8%) to cow's milk, 21 (9.3%) to sesame, 13 (3.7%) to wheat and eight (3.2%) to soy. Peanut sensitization was the third most common sensitizing allergen, and seen mostly in young atopic children with multiple food hypersensitivities and a family history of atopic dermatitis. The median reported age of first exposure to fish and shellfish was 6 and 12 months, respectively. The mean age at presentation of children with shellfish hypersensitivity was at 6.7 years of age. The likelihood of shellfish sensitization was increased in children with concomitant sensitization to cockroaches.

CONCLUSIONS

In contrast to previously reported low peanut allergy rates in Asia, in our review, peanut sensitization is present in 27% (62/227) of food-allergic children, mostly in patients with multiple food protein sensitizations. Temporal patterns of first exposure of infants to fish and shellfish are unique to the Asian diet. Shellfish are a major sensitizing food source in Asian children, especially in allergic rhinitis patients sensitized to cockroaches.

Proteomic approaches for identifying new allergens and diagnosing allergic diseases

BACKGROUND

Allergic diseases are (IgE)-mediated hypersensitivity reactions affecting more than 25% of the world's population. Proteomic technologies have been increasingly used in the field of allergy and include the use of protein microarrays and two-dimensional gel electrophoresis coupled with immunoblotting.

METHODS

The literature relevant to proteomic approaches to allergic diseases was searched using MEDLINE database. We reviewed proteomics approaches and applications, focusing specifically on two-dimensional immunoblotting techniques and allergen microarrays.

RESULTS

The results obtained show that proteomic approaches using two-dimensional immunoblotting appear to be a powerful strategy for the identification of allergenic proteins. Likewise, the use of allergen microarrays allows a large number of IgE antibodies to be simultaneously identified.

CONCLUSIONS

Proteomic approaches are only beginning to be applied to the study of allergy. In the field of in vitro diagnosis, allergen microarrays provide a promising tool not routinely used in the allergy laboratory. In the near future this powerful technique will be used as a standard technique for in vitro diagnosis of allergy.

Does skin prick test reactivity to purified allergens correlate with clinical severity of peanut allergy?

BACKGROUND

Recognition of specific peanut allergens or the diversity of IgE binding to peanut allergens may play a role in the elicitation of severe allergic reactions.

OBJECTIVE

To investigate whether sensitization to individual allergens Ara h 1, Ara h 2, Ara h 3 and Ara h 6 is correlated with clinical severity.

METHODS

The reactivity of purified peanut allergens was measured by skin prick test (SPT) and by IgE immunoblot in 30 patients. The results were related to the clinical reactivity by history, and in 25 of them to the eliciting dose (ED).

RESULTS

The majority of patients recognized Ara h 2 and Ara h 6. Patients with severe symptoms had a higher SPT response to Ara h 2 and Ara h 6 at low concentrations (0.1 micro g/mL) and to Ara h 1 and Ara h 3 at higher concentrations (100 micro g/mL), compared with patients with mild symptoms. They also recognized a greater number of allergens and showed a higher cumulative SPT response compared with patients with mild symptoms. No significant differences were observed between patients with a low or high ED.

CONCLUSIONS

Ara h 2 and Ara h 6 appeared to be more potent than Ara h 1 and Ara h 3. Both SPT reactivity to low concentrations of Ara h 2 and Ara h 6 and to higher concentrations of Ara h 1 and Ara h 3 were shown to be indicative of severe symptoms.

Peanut allergy: Emerging concepts and approaches for an apparent epidemic

Peanut allergy is typically lifelong, often severe, and potentially fatal. Because reactions can occur from small amounts, the allergy presents patients with significant obstacles to avoid allergic reactions. In North America and the United Kingdom, prevalence rates among schoolchildren are now in excess of 1%, framing an increasing public health concern and raising research questions about environmental, immunologic, and genetic factors that may influence outcomes of peanut allergy. This review focuses on recent observations that continue to question the influences of maternal and infant diet on outcomes of peanut allergy, and explore how peanut may be uniquely suited to induce an allergic response. We highlight studies that affect current diagnosis, management, and the nature of advice that can be provided to patients, including the utility of diagnostic tests, doses that elicit reactions, characteristics of reactions from exposure, issues of cross-reactivity, concerns about peanut contamination of manufactured goods, and the natural course of the allergy. Clinical, molecular, and immunologic advances are reviewed, highlighting research discoveries that influence strategies for improved diagnosis, prevention, and treatment. Among the therapeutic strategies reviewed are sublingual and oral immunotherapy, anti-IgE, Chinese herbal medicine, and vaccine strategies.

The management of anaphylaxis in childhood: position paper of the European academy of allergology and clinical immunology

Anaphylaxis is a growing paediatric clinical emergency that is difficult to diagnose because a consensus definition was lacking until recently. Many European countries have no specific guidelines for anaphylaxis. This position paper prepared by the EAACI Taskforce on Anaphylaxis in Children aims to provide practical guidelines for managing anaphylaxis in childhood based on the limited evidence available. Intramuscular adrenaline is the acknowledged first-line therapy for anaphylaxis, in hospital and in the community, and should be given as soon as the condition is recognized. Additional therapies such as volume support, nebulized bronchodilators, antihistamines or corticosteroids are supplementary to adrenaline. There are no absolute contraindications to administering adrenaline in children. Allergy assessment is mandatory in all children with a history of anaphylaxis because it is essential to identify and avoid the allergen to prevent its recurrence. A tailored anaphylaxis management plan is needed, based on an individual risk assessment, which is influenced by the child's previous allergic reactions, other medical conditions and social circumstances. Collaborative partnerships should be established, involving school staff, healthcare professionals and patients' organizations. Absolute indications for prescribing self-injectable adrenaline are prior cardiorespiratory reactions, exercise-induced anaphylaxis, idiopathic anaphylaxis and persistent asthma with food allergy. Relative indications include peanut or tree nut allergy, reactions to small quantities of a given food, food allergy in teenagers and living far away from a medical facility. The creation of national and European databases is expected to generate better-quality data and help develop a stepwise approach for a better management of paediatric anaphylaxis.

The natural history of peanut and tree nut allergy

Peanut and tree nut allergies were once thought to be permanent. Recent studies have shown that about 20% and 10%, respectively, of young patients may outgrow peanut and tree nut allergies. For the majority of patients, however, the natural history is not favorable. In addition, approximately 8% of patients who outgrow peanut allergy may suffer a recurrence. The rising prevalence of these allergies, coupled with the knowledge that allergic reactions to these foods have the potential to be severe or fatal and that accidental exposures are common, makes developing effective treatments to alter the natural history of peanut and tree nut allergies even more crucial for those who will not outgrow them. At this time, avoidance of the offending foods and being prepared to treat a potential reaction after accidental ingestion is the only treatment, but many promising therapeutic interventions are being investigated.

Contribution of Ara h 2 to peanut-specific, immunoglobulin E-mediated, cell activation

BACKGROUND

Ara h 2 is a potent peanut allergen but its contribution to the ability of a crude peanut extract (CPE) to cross-link IgE and activate mast cells has not been rigorously evaluated.

OBJECTIVE

To measure the contribution that Ara h 2 makes to the effector function of a CPE.

METHODS

Ara h 2 was specifically removed from a CPE as demonstrated by immunoblots, 2D gels, and an inhibitory ELISA. Functional assays of sham-treated and Ara h 2-depleted CPEs were performed with RBL SX-38 cells sensitized with IgE from highly peanut-allergic subjects and with naturally sensitized basophils.

RESULTS

Depletion of approximately 99% of the Ara h 2 from the CPE led to an increase in the concentration of the CPE necessary to give 50% of maximal degranulation (EC50) of the SX-38 cells following sensitization with sera that contain anti-Ara h 2 IgE. Assays with a pool of 10 sera showed a small but significant increase in the EC50 following depletion of Ara h 2 (1.65+/-0.15-fold; P<0.05) and assays of seven individual sera showed a similar increase in the average EC50 (1.7+/-0.2-fold; P<0.02). The percent of the anti-peanut IgE that binds Ara h 2 correlated with an increase in the EC50 of the CPE following depletion of Ara h 2 (r=0.83; P<0.02). On the other hand, data from three of these patients studied with a basophil histamine release assay did not show a significant effect of depletion of Ara h 2.

CONCLUSION

Based on its ability to cross-link IgE effectively, Ara h 2 is clearly an important peanut allergen. Its ability to cross-link IgE effectively from a specific serum is related to the proportion of anti-Ara h 2 in that serum but Ara h 2 does not account for a majority of the effector activity of the CPE for any of the sera studied.

Food anaphylaxis

Anaphylaxis is a life-threatening allergic reaction, and food is one of the most common responsible allergens in the outpatient setting. The prevalence of food-induced anaphylaxis has been steadily rising. Education regarding food allergen avoidance is crucial as most of the fatal reactions occurred in those with known food allergies. The lack of a consensus definition for anaphylaxis has made its diagnosis difficult. Symptoms affect multiple organ systems and include pruritus, urticaria, angioedema, vomiting, diarrhoea, abdominal cramps, respiratory difficulty, wheezing, hypotension, and shock. Prompt recognition of anaphylaxis is essential as delayed treatment has been associated with fatalities. Although epinephrine is accepted as the treatment of choice, timely administration does not always occur, partly due to a lack of awareness of the diagnostic criteria. Several novel tools are currently being investigated, which will potentially aid in the diagnosis and treatment of food-induced anaphylaxis.

Bioinformatics approaches to classifying allergens and predicting cross-reactivity

Allergenic proteins from very different environmental sources have similar sequences and structures. This fact may account for multiple allergen syndromes, whereby a myriad of diverse plants and foods may induce a similar IgE-based reaction in certain patients. Identifying the common triggering protein in these sources, in silico, can aid designing individualized therapy for allergen sufferers. This article provides an overview of databases on allergenic proteins, and ways to identify common proteins that may be the cause of multiple allergy syndromes. The major emphasis is on the relational Structural Database of Allergenic Proteins (SDAP []), which includes cross-referenced data on the sequence, structure, and IgE epitopes of over 800 allergenic proteins, coupled with specially developed bioinformatics tools to group all allergens and identify discrete areas that may account for cross-reactivity. SDAP is freely available on the Web to clinicians and patients.

The peanut allergy epidemic: allergen molecular characterisation and prospects for specific therapy

Peanut (Arachis hypogaea) allergy is a major cause of food-induced anaphylaxis, with increasing prevalence worldwide. To date, there is no cure for peanut allergy, and, unlike many other food allergies, it usually persists through to adulthood. Prevention of exposure to peanuts is managed through strict avoidance, which can be compromised by the frequent use of peanuts and peanut products in food preparations. Conventional subcutaneous-injection allergen immunotherapy using crude peanut extract is not a recommended treatment because of the risk of severe side effects, largely as a result of specific IgE antibodies. Consequently, there is an urgent need to develop a suitable peanut allergen preparation that can induce specific clinical and immunological tolerance to peanuts in allergic individuals without adverse side effects. This requires detailed molecular and immunological characterisation of the allergenic components of peanut. This article reviews current knowledge on clinically relevant peanut allergens, in particular Ara h 1, Ara h 2 and Ara h 3, together with options for T-cell-reactive but non-IgE-binding allergen variants for specific immunotherapeutic strategies. These include T-cell-epitope peptide and hypoallergenic mutant vaccines. Alternative routes of administration such as sublingual are also considered, and appropriate adjuvants for delivering effective treatments at these sites examined.

[In vitro allergy testing]

Along with the history, skin tests and provocation tests, in vitro test procedures are essential for the adequate care for patients with allergies. While serological investigations of immediate-type allergic reactions primarily detect allergen-specific IgE antibodies, basophil activation tests with different read-out parameters are available for cellular diagnosis of immediate-type reaction patterns. If clinically necessary, further immunological methods (i. e. immunoblots, lymphocyte transformation tests) can be employed. New options are provided by allergen microarray technology, which makes it possible to determine not only the specific antigenic protein but also to analyze different epitopes.

Human body fluid proteome analysis

The focus of this article is to review the recent advances in proteome analysis of human body fluids, including plasma/serum, urine, cerebrospinal fluid, saliva, bronchoalveolar lavage fluid, synovial fluid, nipple aspirate fluid, tear fluid, and amniotic fluid, as well as its applications to human disease biomarker discovery. We aim to summarize the proteomics technologies currently used for global identification and quantification of body fluid proteins, and elaborate the putative biomarkers discovered for a variety of human diseases through human body fluid proteome (HBFP) analysis. Some critical concerns and perspectives in this emerging field are also discussed. With the advances made in proteomics technologies, the impact of HBFP analysis in the search for clinically relevant disease biomarkers would be realized in the future.

Mechanisms of type I food allergy

The gastrointestinal tract represents the biggest immune organ of the human body and has 3 distinct functions: (1) barrier and defense against potential pathogens, (2) ignorance or tolerance of innocuous agents, and (3) digestion and nutritional uptake of alimentary compounds. Recent studies have indicated that especially structural features of dietary proteins seem to be a precondition for the induction of immediate type immune responses. Crystallographic studies of allergen molecules have been fundamental for epitope studies in a 3-dimensional format using peptides or mimotopes. The identified IgE epitopes were all conformational and responsible for high-affinity interactions with specific IgE. Moreover, numerous studies have indicated that allergens, among them food allergens, preferentially form di-, tri-, or multimers, thus leading to a repetitive display of epitopes. As B-lymphocytes are pattern recognizers, this feature is essential for a memory response, but may also be critical for the very first allergen contact and initiation of the IgE response. Here we review the key candidate cells in the gut, which are capable of recognizing conformation and molecular patterns, but may also be involved in skewing the immune response towards Th2. Animal models have been basic for understanding the molecular principles of food allergy and they will be increasingly indispensable for the definition of novel vaccination strategies. Therefore, the available models are critically analyzed in this review.

Food allergies: prevalence, molecular characterization, and treatment/prevention strategies

A significant proportion of the population is either affected by or concerned about food allergy. Our knowledge about food allergens and how they stimulate the immune system has increased dramatically over the past decade. However, reasons for the increased prevalence of food allergy are not clear. The diagnosis of food allergy requires that the patient and caregivers examine all foods for the presence of potential allergens in order to prevent inadvertent ingestion and further reactions. Fortunately, many children develop tolerance to allergenic foods after a period of dietary elimination. Various immunotherapy approaches are under investigation to alleviate or prevent food-induced reactions in those who have persistent food allergies.

Diagnosis of food allergy

The diagnosis of food allergy requires obtaining a detailed medical history and consideration of differential diagnosis. The offending food(s) may be identified by the medical history, trials of elimination diets, SPT, food-specific IgE measurement, or some combination. However, the reliability of these methods is usually suboptimal, and confirmation of the offending food(s) requires well-designed challenge tests.

From functional genomics to functional immunomics: new challenges, old problems, big rewards

The development of DNA microarray technology a decade ago led to the establishment of functional genomics as one of the most active and successful scientific disciplines today. With the ongoing development of immunomic microarray technology—a spatially addressable, large-scale technology for measurement of specific immunological response—the new challenge of functional immunomics is emerging, which bears similarities to but is also significantly different from functional genomics. Immunonic data has been successfully used to identify biological markers involved in autoimmune diseases, allergies, viral infections such as human immunodeficiency virus (HIV), influenza, diabetes, and responses to cancer vaccines. This review intends to provide a coherent vision of this nascent scientific field, and speculate on future research directions. We discuss at some length issues such as epitope prediction, immunomic microarray technology and its applications, and computation and statistical challenges related to functional immunomics. Based on the recent discovery of regulation mechanisms in T cell responses, we envision the use of immunomic microarrays as a tool for advances in systems biology of cellular immune responses, by means of immunomic regulatory network models.

Lack of association of HLA class II alleles with peanut allergy

BACKGROUND

Peanut allergy is a common and severe phenotype of food allergy with a strong genetic component; HLA class II polymorphisms are attractive candidate genes for this disorder.

OBJECTIVE

To determine possible genotypic associations of HLA class II with peanut allergy and attempt replication of previously reported associations.

METHODS

Sibling pairs discordant for peanut allergy were genotyped (low resolution) by polymerase chain reaction-based methods to 7 DQ and 18 DR allele groups. A chi2 analysis was undertaken against sibling controls with statistical adjustment for multiple analyses.

RESULTS

Seventy-three children with confirmed peanut allergy (mean age, 6.5 years; male, 72%; asthma, 58%; atopic dermatitis, 62%; allergic rhinitis, 67%; other food allergies, 41%) and 75 of their siblings who eat peanut (mean age, 8 years; male, 52%; asthma, 12%; atopic dermatitis, 22%; allergic rhinitis, 37%; other food allergy, 7%) were genotyped. Distribution of DQ7 (29% of children with peanut allergy vs 47% sibling controls) was statistically significantly different (P = .04) before statistical correction for multiple comparisons was made by multiplying them by the number of alleles tested (and not statistically significant after correction; P = .30). Distribution of DR11 was nearly statistically significant without statistical adjustment (26% with peanut allergy vs 41% of sibling controls; P = .07; corrected P = 1.3). Alleles that were previously reported to have a weak association with peanut allergy (DRB1 *03, *08; DQB1 *0302, *04) were not verified in this cohort (unadjusted P > .44).

CONCLUSIONS

We could not establish an association between the HLA class II alleles evaluated in this cohort of sibling pairs discordant for peanut allergy.

Evaluation of basophil activation in food allergy: present and future applications

PURPOSE OF REVIEW

The diagnosis of immediate hypersensitivity relies on specific IgE and history. Because of low specificity, however, provocation challenges are often necessary. Furthermore, IgE testing does not predict features such as reaction severity; nor can it discriminate cross-reactivity from multiple sensitizations. Direct and passive basophil activation tests may address these needs. In addition, measuring basophil activation ex vivo may be useful for monitoring patients with food allergies.

RECENT FINDINGS

Several papers using basophil activation tests demonstrate comparable sensitivity and specificity to current testing for food allergy. Flow-based basophil activation tests have also been used to assess functional characteristics of patient IgE. Finally, several activation phenotypes have been identified as markers of allergic inflammation in vivo; these phenotypes appear to correspond to earlier reports of spontaneous histamine-releasing basophils in patients with active allergic inflammation.

SUMMARY

Although in their early stages, direct basophil activation tests may prove to be useful in the clinic. Indirect basophil activation studies are useful when applied to compare functional aspects of IgE. Identification of basophil activation ex vivo is a promising approach for monitoring allergic inflammation.

Current developments in peanut allergy

PURPOSE OF REVIEW

Peanut allergy is among the most serious, life-threatening food sensitivities, and recent studies indicate increasing prevalence, particularly among children. Our objective is to highlight recent advances in the immunology and treatment of peanut allergy.

RECENT FINDINGS

Peanut sensitization may be both a Th1- and Th2-driven process, and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) may play a role in regulating the response intensity. Preliminary work shows that the food matrix is important in the immune response to peanut and that purified peanut allergens may have little intrinsic stimulatory capacity. Studies characterizing peanut allergens have revealed Ara h 1 and Ara h 2 as the most potent allergens, but Ara h 3 may be more allergenic than previously thought. There appears to be a relationship between the diversity of IgE-binding patterns and the severity of clinical symptoms. Multiple novel approaches to treatment are being investigated, which include traditional Chinese medicine, various forms of modified immunotherapy and the use of adjuvants in modified immunotherapy.

SUMMARY

By understanding the immunologic response to peanut and the roles of the major peanut allergens, it may be possible to predict those at risk for severe reactions, prevent peanut sensitization and effectively treat those already sensitized.

Component-resolved diagnostics in food allergy

PURPOSE OF REVIEW

The purpose of this paper is to review and discuss recent studies on component-resolved diagnostics in food allergy, involving panels of pure allergen molecules or arrays of peptides derived from allergen sequences, and to summarize the reporting of new food allergens during the past 2 years.

RECENT FINDINGS

Several component-resolved diagnostic studies in food allergy suggest that the use of panels of allergen molecules may allow refined clinical information to be obtained on the likelihood or severity of an allergic food reaction and regarding diagnostic specificity. Further, in some studies the use of pure allergen molecules has led to a clearly higher sensitivity of the immunoglobulin E immunoassay compared with conventional allergen extracts.

SUMMARY

While common diagnostic methods in allergy assess the presence or absence of allergen-specific sensitization, to date, no in-vitro or in-vivo test exists which exhibits full correlation with clinical food allergy. A multitude of recently reported findings and observations indicate that molecular analysis of allergen sensitization pattern may serve to enhance the clinical utility of immunoglobulin E antibody-based allergy diagnostics. Pure natural and recombinant allergen molecules as well as panels of synthetic peptides have been used for this purpose.

The performance of a component-based allergen-microarray in clinical practice

BACKGROUND

Currently, the diagnosis of IgE-mediated allergy is based on allergen-specific history and diagnostic procedures using natural allergen extracts for in vivo and in vitro tests.

OBJECTIVE

The aim of the study was to comparatively analyse a new component-based allergen-microarray and the 'quasi-standard' ImmunoCAP for their clinical relevance in patients with allergic rhinoconjunctivitis to five aeroallergens [house dust mite (HDM), cat dander, birch, grass and mugwort pollen] in a prospective, double-centre study.

METHODS

We enrolled 120 subjects at the two study centres. Allergic patients were defined as having an allergen-specific history plus a concomitant positive skin-prick test (SPT) to natural allergen extracts and specific serum IgE was measured by both methods. Each allergen was analysed separately.

RESULTS

The microarray performed equally well in receiver-operating characteristic curve (ROC) analyses when compared with the CAP in cat (23 allergic vs 97 non-allergic, ROC area under the curve microarray 0.950 vs CAP 0.894, P = 0.211), birch (31/89, 0.908 vs 0.878, P = 0.483) and grass pollen (47/73, 0.923 vs 0.915, P = 0.770). It was slightly less sensitive in HDM-allergic subjects (26 allergic vs 94 non-allergic, ROC area microarray 0.808 vs CAP 0.911, P = 0.053) and displayed a reduced sensitivity in the mugwort pollen-allergic patients (17/103, 0.723 vs 0.879, P = 0.032).

CONCLUSIONS

Component-based testing and the whole-allergen CAP are equally relevant in the diagnosis of grass-, birch- and cat-allergic patients. Although slightly less sensitive, the microarray is sufficient for the diagnosis of HDM-allergic patients, but needs alternative and/or additional components for detecting mugwort allergy.

Second Symposium on the Definition and Management of Anaphylaxis: Summary Report—Second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network Symposium

There is no universal agreement on the definition of anaphylaxis or the criteria for diagnosis. In July 2005, the National Institute of Allergy and Infectious Disease and Food Allergy and Anaphylaxis Network convened a second meeting on anaphylaxis, which included representatives from 16 different organizations or government bodies, including representatives from North America, Europe, and Australia, to continue working toward a universally accepted definition of anaphylaxis, establish clinical criteria that would accurately identify cases of anaphylaxis with high precision, further review the evidence on the most appropriate management of anaphylaxis, and outline the research needs in this area.

Second symposium on the definition and management of anaphylaxis: summary report--Second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium

There is no universal agreement on the definition of anaphylaxis or the criteria for diagnosis. In July 2005, the National Institute of Allergy and Infectious Disease and Food Allergy and Anaphylaxis Network convened a second meeting on anaphylaxis, which included representatives from 16 different organizations or government bodies, including representatives from North America, Europe, and Australia, to continue working toward a universally accepted definition of anaphylaxis, establish clinical criteria that would accurately identify cases of anaphylaxis with high precision, further review the evidence on the most appropriate management of anaphylaxis, and outline the research needs in this area.

Anaphylaxis, killer allergy: long-term management in the community

Traditionally, physicians are trained to diagnose and treat anaphylaxis as an acute emergency in a health care setting. In addition to this crucial and time-honored role, we should be cognizant of our wider responsibility to (1) provide a risk assessment for individuals with anaphylaxis, (2) prevent future anaphylaxis episodes by developing long-term personalized risk reduction strategies for affected individuals, and (3) emphasize anaphylaxis education. Risk assessment should include verification of the trigger factor or factors for the anaphylaxis episode by obtaining a comprehensive history and performing relevant investigations, including allergen skin tests and measurement of allergen-specific IgE in serum. In addition, the potential effect of comorbidities and concurrently administered medications on the recognition and emergency treatment of subsequent episodes should be determined. Risk reduction strategies should be personalized to include information about avoidance of specific triggers and initiation of relevant specific preventive treatment (eg, venom immunotherapy). At-risk individuals should be coached in the use of self-injectable epinephrine and equipped with an anaphylaxis emergency action plan and with accurate medical identification. Anaphylaxis education should be provided for these individuals, their families and caregivers, health care professionals, and the general public. Further development of an optimal diagnostic test for anaphylaxis and of tests and algorithms to predict future risk and prevent fatality are urgently needed.

Increasing robustness and sensitivity of protein microarrays through microagitation and automation

Assay systems that employ protein microarrays for the analysis of complex samples are powerful tools to generate a high amount of data from a limiting amount of sample. Due to miniaturization, these systems are susceptible to fluctuations during signal generation and the use of uniform conditions for sample incubation and during the assay procedure is required to get reproducible results. Diffusion limits may prevent constant conditions on all parts of the array and can lead to the decease of the sensitivity of the array. Therefore, we set-up an automated assay system integrating a novel microagitation device using surface acoustic wave (SAW) technology. Multiplexed assays for the detection of autoantibodies from human serum and sandwich immunoassay for the detection of matrix metalloproteases (MMPs) were used to evaluate the system. Diffusion-rate limited solid phase reactions were enhanced by microagitation using the SAW technology resulting in up to three-fold higher signals.

Food allergy--accurately identifying clinical reactivity

Up to 25% of adults believe that they or their children are afflicted with a food allergy. However, the actual prevalence of food allergy is much lower: approximately 6-8% of children suffer from food allergy during their first 3 years of life, and many children then develop clinical tolerance. Food allergy encompasses a whole spectrum of disorders, with symptoms that may be cutaneous, gastrointestinal or respiratory in nature. Food disorders also differ according to the extent that they are immunoglobulin E (IgE)-mediated. Skin-prick testing is often used to identify food sensitization, although double-blind, placebo-controlled food challenge (DBPCFC) tests remain the gold standard for diagnosis. Recent evidence suggests that quantitative IgE measurements can predict the outcome of DBPCFC tests and can replace about half of all oral food challenges. When an extensive medical history is obtained in combination with IgE quantification, even fewer patients may require formal food challenges. It has also become possible to map the IgE-binding regions of many major food allergens. This may help to identify children with persistent food allergy, as opposed to those who may develop clinical tolerance. In future, microarray technology may enable physicians to screen patients for a large number of food proteins and epitopes, using just a few drops of blood.

Multiplexed measurement of serum antibodies using an array biosensor

The array biosensor provides the capability for simultaneously measuring titers of antibody against multiple antigens. Human antibodies against four different targets, tetanus toxin, diphtheria toxin, staphylococcal enterotoxin B (SEB) and hepatitis B, were measured simultaneously in sera from eight different donors in a single assay and titers were determined. The assays could measure amounts of bound antibody as low as approximately 100 fg. Each individual serum exhibited a different pattern of reactivity against the four target antigens. Applications of this biosensor capability include monitoring for exposure to pathogens and for efficacy of vaccination.

Protein-detecting microarrays: current accomplishments and requirements

The sequencing of the human genome has been successfully completed and offers the chance of obtaining a large amount of valuable information for understanding complex cellular events simply and rapidly in a single experiment. Interestingly, in addressing these proteomic studies, the importance of protein-detecting microarray technology is increasing. In the coming few years, microarray technology will become a significantly promising and indispensable research/diagnostic tool from just a speculative technology. It is clear that the protein-detecting microarray is supported by three independent but strongly related technologies (surface chemistry, detection methods, and capture agents). Firstly, a variety of surface-modification methodologies are now widely available and offer site-specific immobilization of capture agents onto surfaces in such a way as to keep the native conformation and activity. Secondly, sensitive and parallel detection apparatuses are being developed to provide highly engineered microarray platforms for simultaneous data acquisition. Lastly, in the development of capture agents, antibodies are now probably the most prominent capture agents for analyzing protein abundances. Alternative scaffolds, such as phage-displayed antibody and protein fragments, which provide the advantage of increasing diversity of proteinic capture agents, however, are under development. An approach involving recombinant proteins fused with affinity tag(s) and coupled with a highly engineered surface chemistry will provide simple production protocols and specific orientations of capture agents on the microarray formats. Peptides and other small molecules can be employed in screening highly potent ligands as well as in measuring enzymatic activities. Protein-detecting microarrays supported by the three key technologies should contribute in accelerating diagnostic/biological research and drug discovery.

IgE and IgG4 epitope mapping by microarray immunoassay reveals the diversity of immune response to the peanut allergen, Ara h 2

BACKGROUND

Detailed assessment of antibody responses to allergens reveals clinically relevant information about both host response and antigen structure. Microarray technology offers advantages of scale and parallel design over previous methods of epitope mapping.

OBJECTIVE

We designed a redundant peptide microarray for IgE and IgG4 epitope mapping of the previously characterized peanut allergen, Ara h 2.

METHODS

Six complete sets of overlapping peptides were commercially synthesized and site-specifically bound to epoxy-derivatized glass slides in triplicate. Peptides were 10, 15, or 20 amino acids in length with an offset of either 2 or 3 amino acids. A total of 10 control and 45 peanut-allergic sera were assayed. Specific IgE and IgG4 were detected by using fluorochrome-labeled monoclonal secondary antibodies.

RESULTS

By using 15-mer and 20-mer peptides, we could define 11 antigenic regions, whereas only 5 were identifiable using 10-mers. Controls and patients produced IgG4 recognizing a comparable number of Ara h 2 peptides, although the dominant epitopes were distinct. As expected, patient IgE bound a larger number of Ara h 2 peptides (9.4% vs 0.9%). IgE and IgG4 epitopes recognized by patients were largely the same, and there was a positive association between IgE and IgG(4) signal, suggesting coordinate regulation. Cluster analysis of peptide binding patterns confirmed the specificity of antibody-peptide interactions and was used to define 9 core epitopes ranging from 6 to 16 residues in length-7 of which (78%) agreed with previous mapping.

CONCLUSION

Epitope mapping by microarray peptide immunoassay and cluster analysis reveals interpatient heterogeneity and a more detailed map.

Common physical-chemical properties correlate with similar structure of the IgE epitopes of peanut allergens

Although many sequences and linear IgE epitopes of allergenic proteins have been identified and archived in databases, structural and physicochemical discriminators that define their specific properties are lacking. Current bioinformatics tools for predicting the potential allergenicity of a novel protein use methods that were not designed to compare peptides. Novel tools to determine the quantitative sequence and three-dimensional (3D) relationships between IgE epitopes of major allergens from peanut and other foods have been implemented in the Structural Database of Allergenic Proteins (SDAP; http://fermi.utmb.edu/SDAP/). These peptide comparison tools are based on five-dimensional physicochemical property (PCP) vectors. Sequences from SDAP proteins similar in their physicochemical properties to known epitopes of Ara h 1 and Ara h 2 were identified by calculating property distance (PD) values. A 3D model of Ara h 1 was generated to visualize the 3D structure and surface exposure of the epitope regions and peptides with a low PD value to them. Many sequences similar to the known epitopes were identified in related nut allergens, and others were within the sequences of Ara h 1 and Ara h 2. Some of the sequences with low PD values correspond to other known epitopes. Regions with low PD values to one another in Ara h 1 had similar predicted structure, on opposite sides of the internal dimer axis. The PD scale detected epitope pairs that are similar in structure and/or reactivity with patient IgE. The high immunogenicity and IgE reactivity of peanut allergen proteins might be due to the proteins' arrays of similar antigenic regions on opposite sides of a single protein structure.

Importance of databases in experimental and clinical allergology

Information technology (IT) is leading us to reconsider some of the approaches we have been using in both basic research and clinical work in allergology. Resources mainly coming from the advent of the Internet are further amplified by the parallel development of other new tools, such as molecular biology and nanotechnology. These three powerful tools are now available and are cross-linked to a certain degree to express their power when applied to biomedical fields. Bioinformatics applied to allergy simplifies our way of handling an increasing wealth of knowledge. This review assesses the current status of allergen databases that are mainly dedicated to sequence homology collection for computational purposes. Whether or not they integrate features that are now typical of IT in other biomedical fields is analyzed as well. The results of these analyses are discussed with a view to the critical need of integrating biochemical data with clinical, epidemiological information and how this goal can be reached by the use of proteomic microarrays for IgE detection. Future directions for a more comprehensive use of allergen databases are proposed.

Food allergy diagnostics: scientific and unproven procedures

PURPOSE OF REVIEW

The accurate diagnosis of food allergy is crucial not only for the right treatment but also for the avoidance of unnecessary diets. The diagnostic work-up of suspected food allergy includes the measurement of food-specific IgE antibodies using serologic assays, the skin prick test, elimination diets and oral provocation tests. In addition, some approaches are either under further rigorous investigation (the atopy patch test) or are already in widespread use, particularly by practitioners of alternative or complementary medicine, but are considered unproven. These diagnostic methods include specific IgG to foods, provocation/neutralization testing, kinesiology, cytotoxic tests and electrodermal testing. This review covers some of the most common scientifically validated and unproven approaches used in the diagnosis of food allergy.

RECENT FINDINGS

For specific serum IgE and the SPT, decision points have been established for some foods, allowing prediction of clinical relevance. The APT may be helpful, especially when considered in combination with defined levels of specific IgE. In regard to other approaches, most scientific studies do refute the usefulness of these approaches.

SUMMARY

In most patients, controlled oral food challenges remain the gold standard in the diagnostic work-up of suspected food allergy. The skin prick test and measurement of specific IgE antibodies to food extracts, individual allergens or allergenic peptides are helpful in the diagnostic approach. Food-specific IgG continues to be an unproven or experimental test. The other alternative and complementary techniques have no proven benefit and may endanger patients via misdiagnosis.

Assessing Genetically Modified Crops to Minimize the Risk of Increased Food Allergy: A Review

The first genetically modified (GM) crops approved for food use (tomato and soybean) were evaluated for safety by the United States Food and Drug Administration prior to commercial production. Among other factors, those products and all additional GM crops that have been grown commercially have been evaluated for potential increases in allergenic properties using methods that are consistent with the current understanding of food allergens and knowledge regarding the prediction of allergenic activity. Although there have been refinements, the key aspects of the evaluation have not changed. The allergenic properties of the gene donor and the host (recipient) organisms are considered in determining the appropriate testing strategy. The amino acid sequence of the encoded protein is compared to all known allergens to determine whether the protein is a known allergen or is sufficiently similar to any known allergen to indicate an increased probability of allergic cross-reactivity. Stability of the protein in the presence of acid with the stomach protease pepsin is tested as a risk factor for food allergenicity. In vitro or in vivo human IgE binding are tested when appropriate, if the gene donor is an allergen or the sequence of the protein is similar to an allergen. Serum donors and skin test subjects are selected based on their proven allergic responses to the gene donor or to material containing the allergen that was matched in sequence. While some scientists and regulators have suggested using animal models, performing broadly targeted serum IgE testing or extensive pre- or post-market clinical tests, current evidence does not support these tests as being predictive or practical. Based on the evidence to date, the current assessment process has worked well to prevent the unintended introduction of allergens in commercial GM crops.