Purpose of the review
Recent investigation has resulted in significant advances toward definitive therapeutic options for food allergy. In this review, we will explore novel immunotherapeutic interventions for the active treatment of food allergy.
Because the injection route for allergen immunotherapy to foods has been associated with an unacceptable risk of severe anaphylactic reactions, use of mucosally targeted therapeutic strategies is of significant interest for food allergy. Allergen-specific immunotherapeutic approaches such as oral, sublingual, epicutaneous, and peptide immunotherapy have demonstrated efficacy in increasing threshold dose and inducing immunologic changes associated with both desensitization and oral tolerance in animal and human trials. More global immunomodulatory strategies, such as Traditional Chinese Medicine and anti-IgE therapy have been shown to effectively target the allergic response, and clinical trials are ongoing to determine the efficacy and safety in human food allergy.
The advent of therapies that target the mucosal immune response to promote oral tolerance have shown great promise in the treatment of food hypersensitivity. However, there is still significant risk of adverse reactions associated with these therapeutic strategies and further study is needed to carefully advance these therapeutic modalities toward general clinical implementation.
Food allergy; oral tolerance; immunotherapy; T-regulatory cells
In Westernized countries, over 1% of the population is allergic to peanuts or tree nuts, which carries a risk of severe allergic reactions. Several studies support the efficacy of peanut oral immunotherapy (OIT) for reducing the clinical sensitivity of affected individuals; however, the mechanisms of this effect are still being characterized. One mechanism that may contribute is the suppression of effector cells, such as basophils. Basophil anergy has been characterized in vitro as a pathway-specific hyporesponsiveness; however, this has not been demonstrated to occur in vivo.
To evaluate the hypothesis that basophil anergy occurs in vivo due to chronic allergen exposure in the setting of a clinical oral immunotherapy trial.
Samples of peripheral blood were obtained from subjects during a placebo-controlled clinical trial of peanut OIT. Basophil reactivity to in vitro stimulation with peanut allergen and controls was assessed by the upregulation of activation markers, CD63 and CD203c, measured by flow cytometry.
The upregulation of CD63 following stimulation of the IgE receptor, either specifically with peanut allergen or non-specifically with anti-IgE antibody, was strongly suppressed by active OIT. However, OIT did not significantly suppress this response in basophils stimulated by the distinct fMLP receptor pathway. In the subset of subjects with egg sensitization, active peanut OIT also suppressed CD63 upregulation in response to stimulation with egg allergen. Allergen OIT also suppressed the upregulation of CD203c including in response to stimulation with IL-3 alone.
Peanut OIT induces a hyporesponsive state in basophils that is consistent with pathway-specific anergy previously described in vitro. This suggests the hypothesis that effector cell anergy could contribute to clinical desensitization.
human basophils; desensitization; basophil anergy; CD63; CD203c; oral immunotherapy; peanut allergy
For egg allergy, dietary avoidance is the only currently approved treatment. We evaluated oral immunotherapy using egg-white powder for the treatment of children with egg allergy.
In this double-blind, randomized, placebo-controlled study, 55 children, 5 to 11 years of age, with egg allergy received oral immunotherapy (40 children) or placebo (15). Initial dose-escalation, build-up, and maintenance phases were followed by an oral food challenge with egg-white powder at 10 months and at 22 months. Children who successfully passed the challenge at 22 months discontinued oral immunotherapy and avoided all egg consumption for 4 to 6 weeks. At 24 months, these children underwent an oral food challenge with egg-white powder and a cooked egg to test for sustained unresponsiveness. Children who passed this challenge at 24 months were placed on a diet with ad libitum egg consumption and were evaluated for continuation of sustained unresponsiveness at 30 months and 36 months.
After 10 months of therapy, none of the children who received placebo and 55% of those who received oral immunotherapy passed the oral food challenge and were considered to be desensitized; after 22 months, 75% of children in the oral-immunotherapy group were desensitized. In the oral-immunotherapy group, 28% (11 of 40 children) passed the oral food challenge at 24 months and were considered to have sustained unresponsiveness. At 30 months and 36 months, all children who had passed the oral food challenge at 24 months were consuming egg. Of the immune markers measured, small wheal diameters on skin-prick testing and increases in egg-specific IgG4 antibody levels were associated with passing the oral food challenge at 24 months.
These results show that oral immunotherapy can desensitize a high proportion of children with egg allergy and induce sustained unresponsiveness in a clinically significant subset. (Funded by the National Institutes of Health; ClinicalTrials.gov number, NCT00461097.)
To examine circumstances of allergic reactions to foods in a cohort of preschool-aged children.
We conducted a prospective, 5-site observational study of 512 infants aged 3 to 15 months with documented or likely allergy to milk or egg, and collected data prospectively examining allergic reactions.
Over a median follow-up of 36 months (range: 0–48.4), the annualized reaction rate was 0.81 per year (367/512 subjects reporting 1171 reactions [95% confidence interval: 0.76–0.85]). Overall, 269/512 (52.5%) reported >1 reaction. The majority of reactions (71.2%) were triggered by milk (495 [42.3%]), egg (246 [21.0%]), and peanut (93 [7.9%]), with accidental exposures attributed to unintentional ingestion, label-reading errors, and cross-contact. Foods were provided by persons other than parents in 50.6% of reactions. Of 834 reactions to milk, egg, or peanut, 93 (11.2%) were attributed to purposeful exposures to these avoided foods. A higher number of food allergies (P < .0001) and higher food-specific immunoglobulin E (P < .0001) were associated with reactions. Of the 11.4% of reactions (n = 134) that were severe, 29.9% were treated with epinephrine. Factors resulting in undertreatment included lack of recognition of severity, epinephrine being unavailable, and fears about epinephrine administration.
There was a high frequency of reactions caused by accidental and nonaccidental exposures. Undertreatment of severe reactions with epinephrine was a substantial problem. Areas for improved education include the need for constant vigilance, accurate label reading, avoidance of nonaccidental exposure, prevention of cross-contamination, appropriate epinephrine administration, and education of all caretakers.
food allergy; IgE-mediated allergic reaction; epinephrine
The β2-adrenergic receptor (β2AR) is a primary target for medications used to treat asthma. Due to the low abundance of β2AR, very few studies have reported its localization in tissues. However, the intracellular location of β2AR in lung tissue, especially in airway smooth muscle cells, is very likely to have a significant impact on how the airways respond to β-agonist medications. Thus, a method for visualizing β2AR in tissues would be of utility. The purpose of this study was to develop an immunofluorescent labeling technique for localizing native and recombinant β2AR in primary cell cultures.
A panel of six different antibodies were evaluated in indirect immunofluorescence assays for their ability to recognize human and rat β2AR expressed in HEK 293 cells. Antibodies capable of recognizing rat β2AR were identified and used to localize native β2AR in primary cultures of rat airway smooth muscle and epithelial cells. β2AR expression was confirmed by performing ligand binding assays using the β-adrenergic antagonist [3H] dihydroalprenolol ([3H]DHA).
Among the six antibodies tested, we identified three of interest. An antibody developed against the C-terminal 15 amino acids of the human β2AR (Ab-Bethyl) specifically recognized human but not rat β2AR. An antibody developed against the C-terminal domain of the mouse β2AR (Ab-sc570) specifically recognized rat but not human β2AR. An antibody developed against 78 amino acids of the C-terminus of the human β2AR (Ab-13989) was capable of recognizing both rat and human β2ARs. In HEK 293 cells, the receptors were predominantly localized to the cell surface. By contrast, about half of the native rat β2AR that we visualized in primary cultures of rat airway epithelial and smooth muscle cells using Ab-sc570 and Ab-13989 was found inside cells rather than on their surface.
Antibodies have been identified that recognize human β2AR, rat β2AR or both rat and human β2AR. Interestingly, the pattern of expression in transfected cells expressing millions of receptors was dramatically different from that in primary cell cultures expressing only a few thousand native receptors. We anticipate that these antibodies will provide a valuable tool for evaluating the expression and trafficking of β2AR in tissues.
The intestine has an unenviable task: to identify and respond to a constant barrage of environmental stimuli that can be both dangerous and beneficial. The proper execution of this task is central to the homeostasis of the host, and as a result the gastrointestinal tract contains more lymphocytes than any other tissue compartment in the body, as well as unique antigen presenting cells with specialized functions. When antigen is initially encountered through the gut, this system generates a robust T-cell mediated hyporesponsiveness called oral tolerance. Although seminal observations of oral tolerance were made a century ago, the relevant mechanisms are only beginning to be unraveled with the use of modern investigational techniques. Food allergy is among the clinical disorders that occur from a failure of this system, and therapies that seek to reestablish tolerance are currently under investigation.
oral tolerance; T regulatory cell; Foxp3; dendritic cell; food allergy; microbiota; vitamin A; TGF-β; CD103
To develop and validate a food allergy educational program.
Materials developed through focus groups, parental and expert review were submitted to 60 parents of newly referred children having a prior food allergy diagnosis and an epinephrine autoinjector. The main outcome was correct demonstration of an autoinjector.
The correct number of autoinjector activation steps increased from 3.4 to 5.95 (of 6) after training (p<.001) and was 5.47 at 1 year (p<.05). The mean score for comfort with using the autoinjector (7 point Likert scale) before the curriculum was 4.63 (somewhat comfortable) and increased to 6.23 after the intervention (p<.05) and remained elevated at 1 year (6.03). Knowledge tests (maximum 15) increased from a mean score of 9.2 to 12.4 (p<.001) at the initial visit and remained at 12.7 at 1 year. The annualized rate of allergic reactions fell from 1.77 (historical) the year prior, to 0.42 (p<.001) after the program. On a 7 point Likert-scale, all satisfaction categories remained above a favorable mean score of 6: straight-forward, organized, interesting, relevant, and recommend to others.
This food allergy educational curriculum for parents, now available online at no cost, showed high levels of satisfaction and efficacy.
food allergy; anaphylaxis; education
β2-Adrenergic receptors (β2AR) play important regulatory roles in a variety of cells and organ systems and are important therapeutic targets in the treatment of airway and cardiovascular disease. Prolonged use of β-agonists results in tolerance secondary to receptor down-regulation resulting in reduced therapeutic efficiency. The purpose of this work is to evaluate the signaling capabilities of the β2AR expressed by a recombinant adeno-associated viral (AAV) vector that also included an enhanced green fluorescent protein (EGFP) gene (AAV-β2AR/EGFP).
By epifluorescence microscopy, ~40% of infected HEK 293 cells demonstrated EGFP expression. β2AR density measured with [3H]dihydroalprenolol ([3H]DHA) increased either 13- or 77-fold in infected cells compared to mock infected controls depending on the culture conditions used. The [3H]DHA binding was to a single receptor population with a dissociation constant of 0.42 nM, as would be expected for wild-type β2AR. Agonist competition assays with [3H]DHA showed the following rank order of potency: isoproterenol>epinephrine> norepinephrine, consistent with β2AR interaction. Isoproterenol-stimulated cyclic AMP levels were 5-fold higher in infected cells compared to controls (314 ± 43 vs. 63.4 ± 9.6 nmol/dish; n = 3). Receptor trafficking demonstrated surface expression of β2AR with vehicle treatment and internalization following isoproterenol treatment.
We conclude that HEK 293 cells infected with AAV-β2AR/EGFP effectively express β2AR and that increased expression of these receptors results in enhanced β2AR signaling. This method of gene transfer may provide an important means to enhance function in in vivo systems.
Data from many studies have suggested a rise in the prevalence of food allergies during the past 10 to 20 years. Currently, no curative treatments for food allergy exist, and there are no effective means of preventing the disease. Management of food allergy involves strict avoidance of the allergen in the patient's diet and treatment of symptoms as they arise. Because diagnosis and management of the disease can vary between clinical practice settings, the National Institute of Allergy and Infectious Diseases (NIAID) sponsored development of clinical guidelines for the diagnosis and management of food allergy. The guidelines establish consensus and consistency in definitions, diagnostic criteria, and management practices. They also provide concise recommendations on how to diagnose and manage food allergy and treat acute food allergy reactions. The original guidelines encompass practices relevant to patients of all ages, but food allergy presents unique and specific concerns for infants, children, and teenagers. To focus on those concerns, we describe here the guidelines most pertinent to the pediatric population.
food allergy; food hypersensitivity; infants; children; guidelines; anaphylaxis
Open-label oral immunotherapy (OIT) protocols have been used to treat small numbers of patients with peanut allergy. Peanut OIT has not been evaluated in double-blind, placebo-controlled trials.
To investigate the safety and effectiveness of OIT for peanut allergy in a double blind, placebo-controlled study.
In this multicenter study, peanut-allergic children ages 1-16 years received OIT with peanut flour or placebo. Initial escalation, build-up, and maintenance phases were followed by an oral food challenge at approximately one year. Titrated skin prick tests (SPT) and laboratory studies were performed at regular intervals.
Twenty-eight subjects were enrolled in the study. Three peanut OIT subjects withdrew early in the study due to allergic side effects. During the double-blind, placebo-controlled food challenge, all remaining peanut OIT subjects (N=16) ingested the maximum cumulative dose of 5000 mg (approximately 20 peanuts), while placebo subjects (N=9) ingested a median cumulative dose of 280 mg (range, 0-1900 mg) [p<0.001]. In contrast to the placebo group, the peanut OIT group showed reductions in SPT size (p<0.001), IL-5 (p=0.01), and IL-13 (p=0.02) and increases in peanut-specific IgG4 (p<0.001). Peanut OIT subjects had initial increases in peanut-specific IgE (p<0.01) but did not show significant change from baseline by the time of OFC. The ratio of FoxP3 hi: FoxP3 intermediate CD4+CD25+ T cells increased at the time of OFC (p=0.04) in peanut OIT subjects.
These results conclusively demonstrate that peanut OIT induces desensitization and concurrent immune modulation. The present study continues and is evaluating the hypothesis that peanut OIT causes long-term immune tolerance.
peanut allergy; oral immunotherapy; desensitization; food allergy
Peanut allergy is typically severe, life-long and prevalent.
To identify factors associated with peanut sensitization.
We evaluated 503 infants 3–15 months of age (mean, 9.4 months) with likely milk or egg allergy but no previous diagnosis of peanut allergy. A total of 308 had experienced an immediate allergic reaction to cow’s milk and/or egg and 204 had moderate to severe atopic dermatitis and a positive allergy test to milk and/or egg. A peanut IgE level of ≥ 5 kUA/L was considered likely indicative of peanut allergy.
A total of 140 (27.8%) infants had PN-IgE levels ≥5 kUA/L. Multivariate analysis including clinical, laboratory and demographic variables showed frequent peanut consumption during pregnancy (OR 2.9, 95% CI 1.7–4.9, p < 0.001), IgE levels to milk (p = 0.001) and egg (p < 0.001), male sex (p = 0.02) and non-white race (p = 0.02) to be the primary factors associated with peanut IgE ≥5 kUA/L. Frequency of peanut consumption during pregnancy and breast feeding showed a dose-response association with peanut IgE ≥ 5 kUA/L, but only consumption during pregnancy was a significant predictor. Among 71 infants never breastfed, frequent consumption of peanut during pregnancy was strongly associated with peanut IgE ≥ 5 kUA/L (OR-4.99, 95% CI-1.69–14.74, p < 0.004).
In this cohort of infants with likely milk or egg allergy, maternal ingestion of peanut during pregnancy was strongly associated with a high level of peanut sensitization.
food allergy; sensitization; atopy; peanut allergy
Peanut OIT has shown promise as a potential treatment for food allergy. However, there remain numerous unanswered questions surrounding this investigational treatment, including the risks of OIT compared to avoidance, dosing regimen issues, patient selection, post-desensitization strategy, allocation of clinical resources, and reimbursement. Further studies are needed to address these outstanding issues in order to determine if this type of therapy is appropriate for clinical use.
peanut allergy; oral immunotherapy; desensitization
Immune features of infants with food allergy have not been delineated.
To explore basic mechanisms responsible for food allergy and identify biomarkers, e.g. prick skin tests (PST), food-specific IgE, and mononuclear cell responses in a cohort of infants with likely milk/egg allergy at increased risk of developing peanut allergy.
Infants aged 3–15 months were enrolled with a positive PST to milk or egg and either a corresponding convincing clinical history of allergy to milk or egg, or with moderate to severe atopic dermatitis (AD). Infants with known peanut allergy were excluded.
Overall, 512 infants (67% males) were studied with 308 (60%) having a history of a clinical reaction. Skin tests and/or detectable food-specific IgE revealed sensitization as follows: milk-78%, egg-89% and peanut-69%. PST and food-specific IgE levels were discrepant for peanut: 15% IgE ≥ 0.35 kUA/L/PST- versus 8% PST+/IgE < 0.35, p = 0.001. Mononuclear cell allergen stimulation screening for CD25, CISH, FOXP3, GATA3, IL-10, IL-4, IFN-gamma and TBET expression using casein, egg white and peanut revealed that only allergen-induced IL-4 expression was significantly increased in those with clinical allergy to milk (compared to non-allergic) and in those sensitized to peanut, despite the absence of an increase in GATA-3 mRNA expression.
Infants with likely milk/egg allergy are at considerably high risk of having elevated peanut-specific IgE (potential allergy). Peanut-specific serum IgE was a more sensitive indicator of sensitization than PST. Allergen-specific IL-4 expression may be a marker of allergic risk. Absence of an increase in GATA-3 mRNA expression suggests that allergen-specific IL-4 may not be of T cell origin.
food allergy; sensitization; atopy
food allergy; peanut allergy; oral immunotherapy
Oral immunotherapy (OIT) has been thought to induce clinical desensitization to allergenic foods, but trials coupling the clinical response and immunologic effects of peanut OIT have not been reported.
The study objective was to investigate the clinical efficacy and immunologic changes associated with OIT.
Peanut-allergic children underwent an OIT protocol including initial day escalation, build-up, and maintenance phases, and then oral food challenge. Clinical response and immunologic changes were evaluated.
Of 29 subjects who completed the protocol, 27 ingested 3.9 g peanut protein during food challenge. Most symptoms noted during OIT resolved spontaneously or with antihistamines. By 6 months, titrated skin prick tests and activation of basophils significantly declined. Peanut-specific IgE decreased by 12–18 months, while IgG4 increased significantly. Serum factors inhibited IgE–peanut complex formation in an IgE-facilitated allergen binding assay. Secretion of IL-10, IL-5, IFN-γ, and TNF-α from PBMCs increased over 6–12 months. Peanut-specific FoxP3 T cells increased until 12 months and then decreased thereafter. Additionally, T cell microarrays showed downregulation of genes in apoptotic pathways.
OIT induces clinical desensitization to peanut, with significant longer term humoral and cellular changes. Microarray data suggest a novel role for apoptosis in OIT.
Peanut hypersensitivity; immunotherapy; immune tolerance; apoptosis; immunoglobulin E; immunoglobulin G; interleukin-5; interleukin-10
Oral immunotherapy offers a promising therapeutic option for peanut allergy. Given that during oral immunotherapy an allergic patient ingests an allergen that could potentially cause a serious reaction, safety of oral immunotherapy is of particular concern.
The purpose of this study is to examine safety during the initial escalation day, build-up phase, and home dosing phase in subjects enrolled in a peanut oral immunotherapy study.
Skin, upper respiratory, chest and abdominal symptoms were recorded with initial escalation day and build-up phase dosings. Subjects also maintained daily diaries detailing symptoms after each home dosing. A statistical analysis of this data was performed.
Twenty of 28 patients completed all phases of the study. During the initial escalation day, upper respiratory (79%) and abdominal (68%) symptoms were the most likely symptoms experienced. The risk of mild wheezing during the initial escalation day was 18%. The probability of having any symptoms after a build-up phase dose was 46%, with a risk of 29% for upper respiratory symptoms and 24% for skin symptoms. The risk of reaction with any home dose was 3.5%. Upper respiratory (1.2%) and skin (1.1%) were the most likely symptoms after home doses. Treatment was given with 0.7% of home doses. Two subjects received epinephrine after one home dose each.
Subjects were more likely to have significant allergic symptoms during the initial escalation day when they were in a closely monitored setting than during other phases of the study. Allergic reactions with home doses were rare.
peanut; food allergy; oral immunotherapy