Background

Ara h 2 and Ara h 6, co-purified together in a 13-25 kD fraction (Ara h 2/6; 20 kD fraction) on gel filtration chromatography, account for the majority of effector activity in a crude peanut extract (CPE) when assayed with RBL SX-38 cells sensitized with IgE from human peanut allergic sera.

Objectives

To determine if Ara h 2/6 are the primary peanut allergens responsible for allergic reactions in vivo and to determine if Ara h 2/6 would be sufficient to prevent allergic reactions to a complete CPE.

Methods

An oral sensitization mouse model of peanut allergy was used to assess the activity of Ara h 2/6 (20 kD) and CPE without the 20 kD fraction (CPE w/o 20 kD) for allergic provocation challenge and immunotherapy. The activity of these preparations was also tested in an assay of histamine release from human basophils in whole blood.

Results

Compared to mice challenged with control CPE, mice challenged with CPE w/o 20 kD experienced reduced symptoms (p<0.05) and a smaller decrease in body temperature (p<0.01). Results with the basophil histamine release assay corroborated these findings (p<0.01). The mouse model was also used to administer Ara h 2/6 (20 kD) in an immunotherapy protocol, in which peanut-allergic mice treated with the 20 kD fraction experienced significantly reduced symptoms, changes in body temperature, and mast cell protease (MMCP-1) release compared to placebo (p<0.01 for all parameters). Importantly, immunotherapy with the 20 kD fraction was just as effective as treatment with CPE, whereas CPE w/o 20 kD was significantly less effective for higher dose peanut challenges.

Conclusions and Clinical Relevance

Ara h 2/6 are the most potent peanut allergens in vivo and can be used to desensitize peanut-allergic mice. These results have potential implications for clinical research in the areas of diagnosis and immunotherapy for peanut allergy.

Background

Oral immunotherapy (OIT) and sublingual immunotherapy (SLIT) are potential therapies for food allergy, but the optimal method of administration, mechanism of action, and duration of response remain unknown.

Objective

We sought to explore the safety and efficacy of OIT and SLIT for the treatment of cow’s milk (CM) allergy.

Methods

We randomized children with CM allergy to SLIT alone or SLIT followed by OIT. After screening double-blind, placebo-controlled food challenges and initial SLIT escalation, subjects either continued SLIT escalation to 7 mg daily or began OIT to either 1000 mg (the OITB group) or 2000 mg (the OITA group) of milk protein. They were challenged with 8 g of milk protein after 12 and 60 weeks of maintenance. If they passed the 60-week challenge, therapy was withdrawn, with challenges repeated 1 and 6 weeks later. Mechanistic correlates included end point titration skin prick testing and measurement of CM-specific IgE and IgG4 levels, basophil histamine release, constitutive CD63 expression, CD203c expression, and intracellular spleen tyrosine kinase levels.

Results

Thirty subjects with CM allergy aged 6 to 17 years were enrolled. After therapy, 1 of 10 subjects in the SLIT group, 6 of 10 subjects in the SLIT/OITB group, and 8 of 10 subjects in the OITA group passed the 8-g challenge (P = .002, SLIT vs OIT). After avoidance, 6 of 15 subjects (3 of 6 subjects in the OITB group and 3 of 8 subjects in the OITA group) regained reactivity, 2 after only 1 week. Although the overall reaction rate was similar, systemic reactions were more common during OIT than during SLIT. By the end of therapy, titrated CM skin prick test results and CD63 and CD203c expression decreased and CM-specific IgG4 levels increased in all groups, whereas CM-specific IgE and spontaneous histamine release values decreased in only the OIT group.

Conclusion

OIT was more efficacious for desensitization to CM than SLIT alone but was accompanied by more systemic side effects. Clinical desensitization was lost in some cases within 1 week off therapy.

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.)

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.

Summary

In the century since Paul Portier and Charles Richet described their landmark findings of severe fatal reactions in dogs re-exposed to venom after vaccination with sea anemone venom, treatment for anaphylaxis continues to evolve. The incidence of anaphylaxis continues to be difficult to measure. Underreporting due to patients not seeking medical care as well as failure to identify anaphylaxis affects our understanding of the magnitude of the disease. Treatment with intramuscular epinephrine continues to be the recommended first line therapy although studies indicate that education of both the patients and the medical community is needed. Adverse food reactions continue to be the leading cause of anaphylaxis presenting for emergency care. Current therapy for food-induced anaphylaxis is built on the foundation of strict dietary avoidance, rapid access to injectable epinephrine, and education to recognize signs and symptoms of anaphylaxis. Investigation into therapy with oral and sublingual immunotherapy as well as other modalities holds hope for improved treatment of food-induced anaphylaxis.

Summary

Peanut sensitization in diacylglycerol kinase zeta (DGKζ) deficient mice led to elevated peanut-IgE levels and severe anaphylaxis. DGKζ deficient CD4+T cells did not account for the phenotype. Future studies will determine which immune lineage caused increased food hypersensitivity.

Synopsis

Over the past 20 years, food allergy has become an increasingly prevalent international health problem primarily in developed countries[1]. An explanation for this increased prevalence is currently under investigation as it is not well understood. Allergic reactions can result in life threatening anaphylaxis over a short period of time, so the current standard of care dictates strict avoidance of suspected trigger foods and accessibility to injectable epinephrine. Intervention at the time of exposure is considered a rescue therapy rather than a disease modifying treatment. In recent years, investigators have been studying allergen immunotherapy as a way to promote induction of oral tolerance. These efforts have shown some promise towards a viable disease modifying therapy for food allergies. This review will examine the mechanisms of oral tolerance and the breakdown that leads to food allergy, as well as the history and current state of oral and sublingual immunotherapy development.

Background

There are no treatments currently available for peanut allergy. Sublingual immunotherapy is a novel approach to the treatment of peanut allergy.

Objective

To investigate the safety, clinical effectiveness and immunologic changes with sublingual immunotherapy in peanut-allergic children.

Methods

In this double-blind, placebo-controlled study, subjects underwent 6 months of dose escalation and 6 months of maintenance dosing followed by a double-blind, placebo-controlled food challenge.

Results

Eighteen children ages 1 to 11 years completed 12 months of dosing and the food challenge. Dosing side effects were primarily oropharyngeal and uncommonly required treatment. During the double-blind, placebo-controlled food challenge, the treatment group safely ingested 20 times more peanut protein than the placebo group (median 1710 mg vs. 85 mg, p=0.011). Mechanistic studies demonstrated a decrease in prick skin test wheal size (p=0.020) and decreased basophil responsiveness after stimulation with 10−2 mcg/ml (p=0.009) and 10−3 mcg/ml (p=0.009) of peanut. Peanut-specific IgE increased over the initial 4 months (p=0.002) then steadily decreased over the remaining 8 months (p=0.003) while peanut-specific IgG4 increased during the 12 months (p=0.014). Lastly, IL-5 levels decreased after 12 months (p=0.015). No statistically significant changes were found in IL-13 levels, the percent of T regulatory cells, or IL-10 and IFN-gamma production.

Conclusion

Peanut sublingual immunotherapy is able to safely induce clinical desensitization in peanut allergic children with evidence of immunologic changes suggesting a significant change in the allergic response. Further study is required to determine if continued peanut sublingual immunotherapy is able to induce long-term immune tolerance.

Background

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.

Objective

To investigate the safety and effectiveness of OIT for peanut allergy in a double blind, placebo-controlled study.

Methods

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.

Results

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.

Conclusion

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.

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.

Background

Peanut allergy is typically severe, life-long and prevalent.

Objective

To identify factors associated with peanut sensitization.

Methods

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.

Results

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).

Conclusions

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.

Summary

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.

Background

Immune features of infants with food allergy have not been delineated.

Objectives

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.

Methods

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.

Results

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.

Conclusions

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.

Infantile Pompe disease progresses to a lethal cardiomyopathy in absence of effective treatment. Enzyme replacement therapy (ERT) with recombinant human acid α-glucosidase (GAA) has been effective in most patients with Pompe disease, but efficacy was reduced by high titer antibody responses. Immunomodulatory gene therapy with a low dose adeno-associated virus (AAV) vector (2×1010 particles) containing a liver-specific regulatory cassette significantly lowered IgG, IgG1, and IgE antibodies to GAA in Pompe disease mice, when compared with mock-treated mice (p<0.05). AAV-LSPhGAApA had the same effect on GAA-antibody production whether it was given prior to, following, or simultaneously with the initial GAA injection. Mice given AAV-LSPhGAApA had significantly less decrease in body temperature (p<0.001) and lower anaphylactic scores (p<0.01) following the GAA challenge. Mouse mast cell protease-1 followed the pattern associated with hypersensitivity reactions (p<0.05). Regulatory T cells (Treg) were demonstrated to play a role in the tolerance induced by gene therapy as depletion of Treg led to an increase in GAA-specific IgG (p<0.001). Treg depleted mice were challenged with GAA and had significantly stronger allergic reactions than mice given gene therapy without subsequent Treg depletion (temperature: p<0.01; symptoms: p<0.05). Ubiquitous GAA expression failed to prevent antibody formation. Thus, immunomodulatory gene therapy could provide adjunctive therapy in lysosomal storage disorders treated by enzyme replacement.

Background

The national prevalence and patterns of food allergy (FA) in the United States (US) are not well understood.

Objective

We developed nationally representative estimates of the prevalence of and demographic risk factors for FA, and investigated associations of FA with asthma, hay fever, and eczema.

Methods

8,203 participants in the National Health and Nutrition Examination Survey (NHANES) 2005–2006 had food-specific serum IgE measured to peanut, cow's milk, egg white, and shrimp. Food-specific IgE and age-based criteria were used to define Likely FA (LFA), Possible FA (PFA), and Unlikely FA (UFA), and to develop estimates of clinical FA. Self-reported data were used to evaluate demographic risk factors and associations with asthma and related conditions.

Results

In the US, the estimated prevalence of clinical FA was 2.5% (peanut 1.3%, milk 0.4%, egg 0.2%, shrimp 1.0%, not mutually exclusive). Risk of PFA/LFA was increased in non-Hispanic blacks (odds ratio (OR) 3.06; 95% confidence interval (CI) 2.14-4.36), males (1.87; 1.32-2.66), and children (2.04; 1.42-2.93). Study participants with doctor-diagnosed asthma (vs. no asthma) exhibited increased risk of all measures of food sensitization. Moreover, in those with LFA, the adjusted OR for current asthma (3.8; 1.5-10.7) and an emergency room (ER) visit for asthma in the past year (6.9; 2.4-19.7) were both notably increased.

Conclusion

Population-based serologic data on 4 foods indicate an estimated 2.5% of the US population has FA, and increased risk was found for blacks, males, and children. Additionally, FA could be an under-recognized risk factor for problematic asthma.

Capsule Summary

MOIT can be effective in desensitizing children with severe IgE-mediated CMA, with most tolerating markedly increased amounts of cow’s milk protein over time and demonstrating changes in serologic markers.

Background

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.

Objective

The study objective was to investigate the clinical efficacy and immunologic changes associated with OIT.

Methods

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.

Results

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.

Conclusion

OIT induces clinical desensitization to peanut, with significant longer term humoral and cellular changes. Microarray data suggest a novel role for apoptosis in OIT.

Background

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.

Objective

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.

Methods

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.

Results

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.

Conclusions

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.

Purpose of review

This article reviews the AAP’s statement on early nutritional interventions on the development of atopic disease in infants and children.

Recent findings

Recent findings suggest that restriction of maternal diet during pregnancy and lactation does not play a major role in the development of allergic disease. In high risk infants exclusive breastfeeding for at least 4 months prevents or delays atopic dermatitis, cow milk allergy, and wheezing early in life. There is evidence that supplementing breastfeeding with a hydrolyzed formula protects against atopic disease, especially atopic dermatitis in at risk infants. Finally there is little evidence that delaying the introduction of complimentary foods beyond 4 to 6 months of age has any protective effect against allergy. There is insufficient data that any dietary intervention beyond 4 to 6 months of age has any protective effect against developing atopic disease.

Summary

In high risk infants there is evidence for exclusive breastfeeding for at least 4 months and delaying of complimentary foods until 4 to 6 months prevents the development of allergy. There is some evidence that supplementing hydrolyzed formulas in high risk infants may delay or prevent allergic disease. There is no convincing evidence that maternal manipulation of diet during pregnancy or lactation, use of soy products, or infant dietary restrictions beyond 4 to 6 months has any effect on the development of atopic disease.

Mammalian Toll-like receptors (TLRs) recognize microbial pathogen-associated molecular patterns and are critical for innate immunity against microbial infection. Diacylglycerol (DAG) kinases (DGKs) regulate the intracellular levels of two important second messengers involved in signaling from many surface receptors by converting DAG to phosphatidic acid (PA). We demonstrate that the ζ isoform of the DGK family (DGKζ) is expressed in macrophages (Mφ) and dendritic cells. DGKζ deficiency results in impaired interleukin (IL) 12 and tumor necrosis factor α production following TLR stimulation in vitro and in vivo, increased resistance to endotoxin shock, and enhanced susceptibility to Toxoplasma gondii infection. We further show that DGKζ negatively controls the phosphatidylinositol 3–kinase (PI3K)–Akt pathway and that inhibition of PI3K activity or treatment with PA can restore lipopolysaccharide-induced IL-12 production by DGKζ-deficient Mφ. Collectively, our data provide the first genetic evidence that an enzyme involved in DAG/PA metabolism plays an important role in innate immunity and indicate that DGKζ promotes TLR responses via a pathway involving inhibition of PI3K.