Monitoring Ara h 1, 2 and 3-sIgE and sIgG4 antibodies in peanut allergic children receiving oral rush immunotherapy

Current perspective on allergen immunotherapy for food allergies

Food allergies are an increasing global problem and societal issue. In addition to the potential for severe allergic reactions from accidental ingestion, food allergies impose a significant burden on the quality of life, nutrition, cost of living, and social activities of both those afflicted and their caregivers. Strict avoidance of allergens and use of emergency medications to treat allergic reactions are the traditional management and treatment strategies; however, significant progress has been made in recent years toward better treatment of food allergies. Many clinical trials on food allergen immunotherapy (oral, epicutaneous, and sublingual) have revealed its efficacy in increasing reaction thresholds and desensitization. These positive results led to the first FDA approval of peanut oral immunotherapy (OIT). However, safer and more effective approaches are required, and adjunct treatments and allergen modifications are being considered. More than 100 facilities in Japan conduct OIT, and numerous studies on it have been reported. Unlike in Europe and the US, stepwise oral food challenges with dietary guidance are conducted separately from the OIT. This review describes the current perspectives on allergen immunotherapy for the treatment of food allergies, focusing on evidence from Japan.

Biomarkers in oral immunotherapy

Food allergy (FA) is a global health problem that affects a large population, and thus effective treatment is highly desirable. Oral immunotherapy (OIT) has been showing reasonable efficacy and favorable safety in most FA subjects. Dependable biomarkers are needed for treatment assessment and outcome prediction during OIT. Several immunological indicators have been used as biomarkers in OIT, such as skin prick tests, basophil and mast cell reactivity, T cell and B cell responses, allergen-specific antibody levels, and cytokines. Other novel indicators also could be potential biomarkers. In this review, we discuss and assess the application of various immunological indicators as biomarkers for OIT.

Immunotherapy Effectiveness in Treating Peanut Hypersensitivity: A Systemic Review

Peanut hypersensitivity is one of the top causes of food-related allergic responses and death in high-income countries. As a result, the goal of this study was to see if various forms of immunotherapies can help reduce the severity of peanut hypersensitivity reactions.

From 2019 to 2021, a systematic search of PubMed, Web of Science, Wiley online library, and Science Direct was done. Peanut immunotherapy (PIT) clinical trials were considered. There were 19 trials with a total of 1565 participants. Twelve were on oral immunotherapy (OIT), two on sublingual immunotherapy (SLIT), two on subcutaneous immunotherapy (SCIT), two on epicutaneous immunotherapy (EPIT), and one was a comparison of SLIT and OIT.

Desensitization was achieved by 74.3% of those who received OIT, 11% of those who received SLIT, 61% of those who received SCIT, and 49% of those who received EPIT. The majority of adverse events (AE) were mild to moderate. Those requiring epinephrine, on the other hand, were moderate to severe and were more common in the therapy groups.

This systematic review showed that the current PIT regimens can accomplish desensitization regardless of the route of administration, with an acceptable safety profile.

Adverse events associated with peanut oral immunotherapy in children - a systematic review and meta-analysis

While peanut oral immunotherapy (POIT) represents a promising treatment for peanut allergies in children, safety concerns remain a common barrier to widespread adoption. We aimed to systematically assess available evidence to determine the risk and frequency of adverse events occurring during POIT, and examine study-level characteristics associated with their occurrence and severity. A systematic search of MEDLINE, EMBASE, and Web of Science was conducted through April 2019. Controlled and non-controlled studies evaluating POIT were eligible. Twenty-seven studies, involving 1488 subjects, were included. Adverse events to POIT were common and led to treatment discontinuation in 6.6% of children (95% CI 4.4–9.0; 27 studies, I² = 48.7%). Adverse events requiring treatment with epinephrine occurred among 7.6% (4.5–11.4; 26 studies, I² = 75.5%) of participants, at a rate of 2.0 per 10,000 doses (0.8–3.7; 15 studies, I² = 64.4). Use of a rush treatment phase and targeting a higher maintenance dose were associated with a higher risk and frequency of epinephrine use, while using co-treatments in addition to POIT was associated with a lower risk of treatment discontinuation due to adverse events. While adverse events to POIT are common, this study provides promising explorative evidence that certain modifications to existing treatment protocols could significantly improve treatment outcomes.

Basic Research and Clinical Reports Associated with Low Serum IgG4 Concentrations

Elevated IgG4 concentrations in serum have received a great deal of attention recently, whereas the significance of decreased IgG4 levels was frequently neglected in spite of its close relation with infectious and noninfectious inflammations. In this review, based on the structural and functional characteristics of IgG4, we bring together case reports and research related to low levels of IgG4 and try to scratch the importance of decreased IgG4 concentrations in serum. As with elevated IgG4 levels, low serum IgG4-related diseases can be involved in multiple systems such as infection in the respiratory system, stroke in the circulatory system, and glomerulonephritis in the urinary system. Both genetic and immune dysregulation can contribute to decreased IgG4 levels. In the light of animal experiments, we believe that the mystery of low IgG4 can be revealed as long as enough attention is acquired.

Long-Term Outcome of Peanut Oral Immunotherapy Facilitated Initially by Omalizumab

BACKGROUND

We successfully used omalizumab to facilitate peanut oral immunotherapy (OIT) in children with reactivity to ≤50mg peanut protein and with high peanut IgE (median, 229 kU/L).

OBJECTIVE

We report on long-term OIT outcomes in these patients, including dosing changes, adverse events, peanut immunoglobulin changes, and quality of life (QoL).

METHODS

Patients were followed for up to 72 months (67 months of maintenance). Outcomes were collected on peanut dose amount, form, and frequency, as well as adverse events, (QoL), and laboratory studies.

RESULTS

Of 13 patients initially enrolled, 7 patients (54%) continued on peanut OIT through month 72; 6 (46%) discontinued therapy because of adverse reactions. Maintenance peanut protein dose varied between 500 and 3500mg. Most patients consumed different peanut-containing products. All patients experienced at least 1 adverse event, and 1 patient developed eosinophilic esophagitis. Peanut-IgE, Arah1-IgE and Arah2-IgE, peanut-SPT, peanut-IgE:IgE ratio, and Arah2-IgE:Arah2-IgG4 ratio decreased on OIT. Peanut-IgG4, Arah1-IgG4, and Arah2-IgG4 initially increased on OIT and then decreased, though not falling to baseline levels. In patients who stopped OIT, there was a trend for reversal of these biomarker changes. Higher peanut-IgE and Arah2-IgE at study month 12 were associated with discontinuation. Patient and parent QoL improved from baseline, even in patients who discontinued OIT.

CONCLUSIONS

Although adjunctive omalizumab allowed for faster and successful desensitization in patients with high peanut-IgE, almost half of patients discontinued OIT within 72 months because of reactions. Patients who stopped therapy had higher month 12 peanut-IgE and Arah2-IgE. It is possible that these patients might benefit from longer omalizumab administration.

Low-dose oral immunotherapy for children with anaphylactic peanut allergy in Japan

BACKGROUND

Oral immunotherapy (OIT) is a promising treatment for persons with allergy; however, it can also cause adverse allergic reactions. In this study, we investigated the efficacy of low-dose OIT for anaphylactic peanut allergy.

METHODS

Twenty-four children (median age, 9.6 years) with anaphylaxis to peanuts were hospitalized for 5 days and then gradually fed increasing amounts of peanut powder up to 133 mg/day. One year later, they underwent an oral food challenge after 2 weeks of peanut avoidance. Those who were asymptomatic after ingesting 795 mg of peanut protein were defined as having achieved sustained unresponsiveness. We measured peanut- and Ara h2-specific immunoglobulin (Ig) E, IgG, and IgG4 levels at 0, 1, 3, 6, and 12 months in the OIT group and at 0 and 12 months in the control group.

RESULTS

At baseline, all children in the OIT group and 8 in the control group had a history of anaphylaxis. The median peanut-/Ara h2-specific IgE levels in the OIT and control groups were 55.4/48.6 and 58.2/38.1 kUa/L, respectively. One year later, 8 (33.3%) children in the OIT group exhibited sustained unresponsiveness, while none in the control group did. In the OIT group, the median peanut-specific IgE levels significantly increased to 194.0 kUa/L, after 1 month and then significantly decreased to 57.5 kUa/L at 12 months. Meanwhile, the median peanut- and Ara h2-specific IgG and IgG4 levels increased significantly after 1 month.

CONCLUSION

Low-dose OIT induces immunological changes and has the capability of achieving sustained unresponsiveness in children with peanut anaphylaxis.

Nationwide questionnaire-based survey of oral immunotherapy in Japan

BACKGROUND

Clinical trials on oral immunotherapy (OIT) have been increasing for nearly a decade; however, several national guidelines do not recommend OIT as a standardized procedure. The aim of this study was to obtain insights into the current use and practice of OIT in Japan.

METHODS

A first questionnaire was mailed to 524 training and teaching facilities of the Japan Pediatric Society. The first survey requested information on the implementation of OIT, whereas the second survey aimed to gather more detailed information on OIT, such as its safety.

RESULTS

In total, 360 facilities (69%) responded to the survey; among them, 102 (28%) provided OIT to 7973 patients [1544 received OIT while hospitalized (inpatient OIT), whereas 6429 received OIT without hospitalization (outpatient OIT)]. Approval for OIT was obtained from an ethics committee or institutional review board in 89% and 31% of facilities for inpatient and outpatient OIT, respectively. In inpatient OIT, immediate allergic reactions requiring treatment occurred in 68% of patients while hospitalized, and in another 56%, following discharge. In contrast, 11% of patients developed immediate allergic reactions in outpatient OIT. Adrenaline injections at home were required in 2%. Sixteen patients developed adverse reactions other than immediate allergic reactions, among which eosinophilic gastroenteritis was most common.

CONCLUSIONS

OIT is widely provided not only as clinical research but also as general practice in Japan. However, because there is a high risk of developing anaphylaxis at home, OIT should be conducted carefully as in a clinical research setting taking safety into consideration.

Novel immunotherapy and treatment modality for severe food allergies

PURPOSE OF REVIEW

In recent years, many studies on oral immunotherapy (OIT) have been conducted; however, few have focused on severe food allergies. The purpose of this review was to assess the efficacy and safety of oral immunotherapies for patients with severe food allergy.

RECENT FINDINGS

We reviewed multiple immunotherapy reports published within a few years or reports focusing on severe food allergies. We also investigated recent studies on OIT and novel food allergy management.

SUMMARY

Immunotherapies targeting low-dose antigen exposure and oral food challenges using low-dose target volumes may be safer than conventional OIT. It is necessary to consider which immunotherapy regimen is appropriate based on allergy severity of the patient.

B-FAHF-2 plus oral immunotherapy (OIT) is safer and more effective than OIT alone in a murine model of concurrent peanut/tree nut allergy

BACKGROUND

Concurrent sensitization to peanut (PN) and tree nuts (TN), the most dangerous food allergies, is common. Current oral immunotherapy (OIT) is not fully satisfactory.

OBJECTIVE

To determine whether the herbal formula B-FAHF-2 (BF2) ameliorates PN/TN OIT adverse reactions and enhances persistence of a tolerant state.

METHODS

Concurrently sensitized PN-, walnut- (WN) and cashew (CSH)-allergic mice received 1-day PN/WN/CSH rush OIT plus 3 weeks of maintenance dosing, with or without 3 weeks prior and 3 weeks BF2 co-treatment. Anaphylactic symptom scores, core body temperatures, plasma histamine levels, basophil numbers, antigen-specific IgE, cytokine levels, and IL-4, INF-γ and Foxp3 gene promoter DNA methylation status, and their correlation with final challenge symptom scores were determined.

RESULTS

BF2+OIT-treated mice experienced significantly fewer and less severe adverse reactions than OIT-only-treated mice (P<.01) during the 1-day rush OIT build-up dose phase. Both OIT-only and BF2+OIT mice showed significant desensitization (P<.01 and .001, respectively) at 1 week post-therapy challenge, being greater in BF2+OIT mice. All sham-treated and 91% of OIT-treated mice experienced anaphylaxis whereas only 21% of BF2+OIT-treated mice exhibited reactions during 5-6 weeks of dose escalation single PN and TN challenges. Greater and more persistent protection in BF2+OIT mice was associated with significantly lower plasma histamine and IgE levels, increased IFN-γ/IL-4 and IL-10/IL-4 ratios, DNA remethylation at the IL-4 promoter and demethylation at IFN-γ and Foxp3 promoters. Final challenge symptom scores were inversely correlated with IL-4 DNA methylation levels (P<.0002) and positively correlated with IFN-γ and Foxp3 gene promoter methylation levels (P<.0011) (P<.0165).

CONCLUSIONS AND CLINICAL RELEVANCE

Combined BF2/OIT therapy was safer and produced longer post-treatment protection and more tolerance-prone immunological and epigenetic modifications than OIT alone. BF2/OIT may provide an additional OIT option for patients with concurrent PN/TN and other food allergies.

High-dose bee venom exposure induces similar tolerogenic B-cell responses in allergic patients and healthy beekeepers

BACKGROUND

The involvement of B cells in allergen tolerance induction remains largely unexplored. This study investigates the role of B cells in this process, by comparing B-cell responses in allergic patients before and during allergen immunotherapy (AIT) and naturally exposed healthy beekeepers before and during the beekeeping season.

METHODS

Circulating B cells were characterized by flow cytometry. Phospholipase A2 (PLA)-specific B cells were identified using dual-color staining with fluorescently labeled PLA. Expression of regulatory B-cell-associated surface markers, interleukin-10, chemokine receptors, and immunoglobulin heavy-chain isotypes, was measured. Specific and total IgG1, IgG4, IgA, and IgE from plasma as well as culture supernatants of PLA-specific cells were measured by ELISA.

RESULTS

Strikingly, similar responses were observed in allergic patients and beekeepers after venom exposure. Both groups showed increased frequencies of plasmablasts, PLA-specific memory B cells, and IL-10-secreting CD73^- CD25⁺ CD71⁺ B_R 1 cells. Phospholipase A2-specific IgG4-switched memory B cells expanded after bee venom exposure. Interestingly, PLA-specific B cells showed increased CCR5 expression after high-dose allergen exposure while CXCR4, CXCR5, CCR6, and CCR7 expression remained unaffected.

CONCLUSIONS

This study provides the first detailed characterization of allergen-specific B cells before and after bee venom tolerance induction. The observed B-cell responses in both venom immunotherapy-treated patients and naturally exposed beekeepers suggest a similar functional immunoregulatory role for B cells in allergen tolerance in both groups. These findings can be investigated in other AIT models to determine their potential as biomarkers of early and successful AIT responses.

Double-blind placebo-controlled challenge showed that peanut oral immunotherapy was effective for severe allergy without negative effects on airway inflammation

AIM

This study examined the efficacy and the safety of peanut oral immunotherapy (OIT).

METHODS

We recruited 60 patients aged six years to 18 years who had a moderate-to-severe reaction to a double-blind placebo-controlled peanut challenge: 39 received OIT during an eight-month build-up phase and maintenance phase and 21 controls avoided peanuts. We measured specific immunoglobulin E and G4 (IgE and IgG4) to peanuts and to Ara h 1, 2, 3, 8 and 9 and monitored adverse events, bronchial hyper-responsiveness (BHR) to methacholine and fractional concentrations of exhaled nitric oxide (FeNO). The median follow-up period was 30 months.

RESULTS

Most (85%) of the OIT patients passed the build-up phase and 67% tolerated 5 g of peanuts during the post-treatment challenge. No controls were desensitised, with a risk ratio of 29 and 95% confidence interval of 1.9-455. During OIT, IgE to peanut, Ara h 1, 2 and 3 decreased and IgG4 increased. Consuming peanuts had no harmful effects on BHR or FeNO. The annual incidence rate of emergency visits during the follow-up period was 11% or 3.0 per 10 000 patient-days.

CONCLUSION

Peanut OIT was efficacious in severe allergies without negative effects on airway inflammation, but unpredictable long-term reactions might occur.

Treatment of allergic children - Where is the progress (for the practicing allergist)?

For any kind of therapeutic intervention in allergic diseases such as environmental control, pharmacological, or immunomodulating treatment including educational programs, children are addressed separately from adults. Health authorities like the Food and Drug Administration in the United States of America or the European Medicine Agency in Europe request a specific 'Pediatric investigational plan' with studies addressing dose-response relationship, safety, and efficacy for infants, children, and adolescents. During the last 2 years, promising advances have been reported for the treatment of a variety of allergic and immunologic disorders. This review summarizes the progress in the treatment of pediatric asthma and allergic diseases, based on publications of approximately the last 2.5 years (end of 2013 until May 2016) in and beyond this journal. Meanwhile, it highlights areas with promising novel therapeutic approaches, which are likely to change treatment for allergic children in the near future.

Recent advances in component resolved diagnosis in food allergy

Due to the high prevalence of food allergic diseases globally there are increasing demands in clinical practice for managing IgE-mediated conditions. During the last decade, component resolved diagnostics has been introduced into the field of clinical allergology, providing information that cannot be obtained from extract-based tests. Component resolved data facilitate more precise diagnosis of allergic diseases and identify sensitizations attributable to cross-reactivity. Furthermore it assists risk assessment in clinical practice as sensitization to some allergenic molecules is related to persistence of clinical symptoms and systemic rather than local reactions. The information may also aid the clinician in prescription of oral immunotherapy (OIT) in patients with severe symptoms, and in giving advice on food allergen avoidance or on the need to perform food challenges. The use of allergen components is rapidly evolving and increases our possibility to treat food allergic patients with a more individual approach. Using molecular allergology, we can already now better diagnose, prognose and grade the food allergy. In summary, daily routine molecular allergy diagnostics offers a number of benefits that give us a higher diagnostic precision and allow for better management of the patient.

Food allergen detection by mass spectrometry: the role of systems biology

Food allergy prevalence is rising worldwide, motivating the development of assays that can sensitively and reliably detect trace amounts of allergens in manufactured food. Mass spectrometry (MS) is a promising alternative to commonly employed antibody-based assays owing to its ability to quantify multiple proteins in complex matrices with high sensitivity. In this review, we discuss a targeted MS workflow for the quantitation of allergenic protein in food products that employs selected reaction monitoring (SRM). We highlight the aspects of SRM method development unique to allergen quantitation and identify opportunities for simplifying the process. One promising avenue identified through a comprehensive survey of published MS literature is the use of proteotypic peptides, which are peptides whose presence appears robust to variations in food matrix, sample preparation protocol, and MS instrumentation. We conclude that proteotypic peptides exist for a subset of allergenic milk, egg, and peanut proteins. For less studied allergens such as soy, wheat, fish, shellfish, and tree nuts, we offer guidance and tools for peptide selection and specificity verification as part of an interactive web database, the Allergen Peptide Browser (http://www.AllergenPeptideBrowser.org). With ongoing improvements in MS instrumentation, analysis software, and strategies for targeted quantitation, we expect an increasing role of MS as an analytical tool for ensuring regulatory compliance.

Allergen immunotherapy: an update on protocols of administration

PURPOSE OF REVIEW

Allergen immunotherapy (AIT) is still the only causal treatment for allergic rhinitis and asthma. However, conventional subcutaneous AIT administration schedules are time-consuming and safety issues still play a role; for sublingual AIT, the best efficacy is still investigated and for food allergy the best efficacy-safety balance is not yet completely discovered. Investigators have made progress in these fields lately. (Figure is included in full-text article.)

RECENT FINDINGS

Since January 2014, several (ultra) rush or cluster build-up phases with hypoallergic variants of extracts have been explored with success. Also, the efficacy of only preseasonal subcutaneous AIT was demonstrated for tree and grass pollen. Sublingual AIT was shown to be effective and well tolerated in allergic rhinitis and asthma with tablets and with highly concentrated liquid formulations (ragweed, house dust mite), but not cockroach. For food allergy, oral immunotherapy is promising, but close attention should be paid to the exact administration schedule, maintenance dose, and the definition of efficacy (desensitization or real tolerance, as defined by a negative challenge test at least 4 months off treatment).

SUMMARY

The practicing physician should be watchful for advances in the field of aeroallergen AIT and food oral immunotherapy, analyzing the presented information in detail and interpreting conclusions product specifically, without generalizing.

Analysis of cytokine production by peanut-reactive T cells identifies residual Th2 effectors in highly allergic children who received peanut oral immunotherapy

BACKGROUND

Only limited evidence is available regarding the cytokine repertoire of effector T cells associated with peanut allergy, and how these responses relate to IgE antibodies to peanut components.

OBJECTIVE

To interrogate T cell effector cytokine populations induced by Ara h 1 and Ara h 2 among peanut allergic (PA) children in the context of IgE and to evaluate their modulation during oral immunotherapy (OIT).

METHODS

Peanut-reactive effector T cells were analysed in conjunction with specific IgE profiles in PA children using intracellular staining and multiplex assay. Cytokine-expressing T cell subpopulations were visualized using SPICE.

RESULTS

Ara h 2 dominated the antibody response to peanut as judged by prevalence and quantity among a cohort of children with IgE to peanut. High IgE (> 15 kU(A)/L) was almost exclusively associated with dual sensitization to Ara h 1 and Ara h 2 and was age independent. Among PA children, IL-4-biased responses to both major allergens were induced, regardless of whether IgE antibodies to Ara h 1 were present. Among subjects receiving OIT in whom high IgE was maintained, Th2 reactivity to peanut components persisted despite clinical desensitization and modulation of allergen-specific immune parameters including augmented specific IgG4 antibodies, Th1 skewing and enhanced IL-10. The complexity of cytokine-positive subpopulations within peanut-reactive IL-4(+) and IFN-γ(+) T cells was similar to that observed in those who received no OIT, but was modified with extended therapy. Nonetheless, high Foxp3 expression was a distinguishing feature of peanut-reactive IL-4(+) T cells irrespective of OIT, and a correlate of their ability to secrete type 2 cytokines.

CONCLUSION

Although total numbers of peanut-reactive IL-4(+) and IFN-γ(+) T cells are modulated by OIT in highly allergic children, complex T cell populations with pathogenic potential persist in the presence of recognized immune markers of successful immunotherapy.

Utility of component analyses in subjects undergoing sublingual immunotherapy for peanut allergy

BACKGROUND

Sublingual immunotherapy (SLIT) with peanut changes clinical and immune responses in most peanut-allergic individuals, but the response is highly variable.

OBJECTIVE

We sought to examine the component-specific effects of peanut SLIT and determine whether peanut component testing could predict the outcome of a double-blind, placebo-controlled food challenge (DBPCFC) after 12 months of peanut SLIT.

METHODS

We included 33 subjects who underwent peanut SLIT with a DBPCFC of 2500 mg of peanut protein performed after 12 months of therapy. Plasma samples from baseline and after 12 months of peanut SLIT were assayed using ImmunoCAP for IgE and IgG4 against whole peanut, Ara h 1, Ara h 2, Ara h 3, Ara h 8, and Ara h 9.

RESULTS

Following 12 months of SLIT, 10 subjects (30%) passed the DBPCFC without symptoms and were considered desensitized. Subjects that failed the DBPCFC tolerated a median of 460 mg peanut protein (range: 10-1710 mg). The desensitized group had significantly lower baseline levels of IgE against peanut (median 40.8 vs. 231 kUA /L, P = 0.0082), Ara h 2 (median 17 vs. 113 kUA /L, P = 0.0082), and Ara h 3 (median 0.3 vs. 8.5 kUA /L, P = 0.0396). ROC curves indicated that baseline IgE against peanut and Ara h 2 were equally effective at discriminating between the two groups (AUC = 0.7957, P = 0.007752 for both).

CONCLUSION AND CLINICAL RELEVANCE

In this cohort of subjects undergoing SLIT for peanut allergy, lower baseline levels of IgE against Ara h 2, Ara h 3, and peanut were associated with successful desensitization.

Food Allergy in childhood: phenotypes, prevention and treatment

The prevalence of food allergy in childhood increased in the last decades, especially in Westernized countries where this phenomenon has been indicated as a second wave of the allergic epidemic. In parallel, scientific interest also increased with the effort to explain the reasons of this sudden rise and to identify potential protective and risk factors. A great attention has been focused on early exposures to allergenic foods, as well as on other nutritional factors or supplements that may influence the immune system in a positive direction. Both interventions on maternal diet before birth or during breastfeeding and then directly on infant nutrition have been investigated. Furthermore, the natural history of food allergy also seems to be changing over time; IgE-mediated cow's milk allergy and egg allergy seem to be more frequently a persistent rather than a transient disease in childhood, as described in the last years. Food avoidance and the emergency drugs in case of an adverse event, such as epinephrine self-injector, are currently the first-line treatment in patients with food allergies, with a resulting impairment in the quality of life and social behaviour. During the last decade, oral immunotherapy emerged as an optional treatment with remarkable results, offering a novel perspective in the treatment for and management of food allergy.

Pharmacologic options for the treatment and management of food allergy

Food allergy affects approximately 5% of adults and 8% of children in developed countries, and there is currently no cure. Current pharmacologic management is limited to using intramuscular epinephrine or oral antihistamines in response to food allergen exposure. Recent trials have examined the efficacy and safety of subcutaneous, oral, sublingual, and epicutaneous immunotherapy, with varying levels of efficacy and safety demonstrated. Bacterial adjuvants, use of anti-IgE monoclonal antibodies, and Chinese herbal formulations represent exciting potential for development of future pharmacotherapeutic agents. Ultimately, immunotherapy may be a viable option for patients with food allergy, although efficacy and safety are likely to be less than ideal.

Food allergies: the basics

IgE-associated food allergy affects approximately 3% of the population and has severe effects on the daily life of patients-manifestations occur not only in the gastrointestinal tract but also affect other organ systems. Birth cohort studies have shown that allergic sensitization to food allergens develops early in childhood. Mechanisms of pathogenesis include cross-linking of mast cell- and basophil-bound IgE and immediate release of inflammatory mediators, as well as late-phase and chronic allergic inflammation, resulting from T-cell, basophil, and eosinophil activation. Researchers have begun to characterize the molecular features of food allergens and have developed chip-based assays for multiple allergens. These have provided information about cross-reactivity among different sources of food allergens, identified disease-causing food allergens, and helped us to estimate the severity and types of allergic reactions in patients. Importantly, learning about the structure of disease-causing food allergens has allowed researchers to engineer synthetic and recombinant vaccines.

IgG4 inhibits peanut-induced basophil and mast cell activation in peanut-tolerant children sensitized to peanut major allergens

Background

Most children with detectable peanut-specific IgE (P-sIgE) are not allergic to peanut. We addressed 2 non–mutually exclusive hypotheses for the discrepancy between allergy and sensitization: (1) differences in P-sIgE levels between children with peanut allergy (PA) and peanut-sensitized but tolerant (PS) children and (2) the presence of an IgE inhibitor, such as peanut-specific IgG₄ (P-sIgG₄), in PS patients.

Methods

Two hundred twenty-eight children (108 patients with PA, 77 PS patients, and 43 nonsensitized nonallergic subjects) were studied. Levels of specific IgE and IgG₄ to peanut and its components were determined. IgE-stripped basophils or a mast cell line were used in passive sensitization activation and inhibition assays. Plasma of PS subjects and patients submitted to peanut oral immunotherapy (POIT) were depleted of IgG₄ and retested in inhibition assays.

Results

Basophils and mast cells sensitized with plasma from patients with PA but not PS patients showed dose-dependent activation in response to peanut. Levels of sIgE to peanut and its components could only partially explain differences in clinical reactivity between patients with PA and PS patients. P-sIgG₄ levels (P = .023) and P-sIgG₄/P-sIgE (P < .001), Ara h 1–sIgG₄/Ara h 1–sIgE (P = .050), Ara h 2–sIgG₄/Ara h 2–sIgE (P = .004), and Ara h 3–sIgG₄/Ara h 3–sIgE (P = .016) ratios were greater in PS children compared with those in children with PA. Peanut-induced activation was inhibited in the presence of plasma from PS children with detectable P-sIgG₄ levels and POIT but not from nonsensitized nonallergic children. Depletion of IgG₄ from plasma of children with PS (and POIT) sensitized to Ara h 1 to Ara h 3 partially restored peanut-induced mast cell activation (P = .007).

Conclusions

Differences in sIgE levels and allergen specificity could not justify the clinical phenotype in all children with PA and PS children. Blocking IgG₄ antibodies provide an additional explanation for the absence of clinical reactivity in PS patients sensitized to major peanut allergens.