Binding of peanut allergen Ara h 2 with Vaccinium fruit polyphenols.
The potential for 42 different polyphenols found in Vaccinium fruits to bind to peanut allergen Ara h 2 and inhibit IgE binding epitopes was investigated using cheminformatics techniques. Out of 12 predicted binders, delphinidin-3-glucoside, cyanidin-3-glucoside, procyanidin C1, and chlorogenic acid were further evaluated in vitro. Circular dichroism, UV-Vis spectroscopy, and immunoblotting determined their capacity to (i) bind to Ara h 2, (ii) induce protein secondary structural changes, and (iii) inhibit IgE binding epitopes. UV-Vis spectroscopy clearly indicated that procyanidin C1 and chlorogenic acid interacted with Ara h 2, and circular dichroism results suggested that interactions with these polyphenols resulted in changes to Ara h 2 secondary structures. Immunoblotting showed that procyanidin C1 and chlorogenic acid bound to Ara h 2 significantly decreased the IgE binding capacity by 37% and 50%, respectively. These results suggest that certain polyphenols can inhibit IgE recognition of Ara h 2 by obstructing linear IgE epitopes.
Efficacy and safety of oral immunotherapy for peanut allergy: a pilot study in Singaporean children.
BACKGROUND: Peanut allergy is an increasing problem in Singapore and strict avoidance is difficult as peanut is ubiquitous in Asian cuisine. OBJECTIVE: We aimed to assess the efficacy and safety of peanut oral immunotherapy (OIT) in children with obvious peanut allergy in Singapore. METHODS: This was an open-label study of peanut OIT in children living in Singapore, with 2 weekly dose escalation until final maintenance dose of 3,000 mg of peanut protein and a maintenance phase of 12 months. An oral food challenge was performed at 6 months to assess for desensitisation and at 4 weeks after discontinuation of OIT having completed 12 months of maintenance therapy to assess for possible sustained unresponsiveness. The adverse events were monitored using the symptom diaries. RESULTS: Nine subjects were started on OIT, with 7 managing to complete maintenance phase of therapy. Of these 7, all were able to tolerate at least 3,000 mg of peanut protein by 6 months of maintenance therapy, showing that the OIT was effective. Of these 7, 3 patients complied with the 4-week abstinence period after completion of OIT before another peanut challenge; 2 of the 3 subjects showed a significant decrease from the initial ability to tolerate 3,000 mg of peanut protein. Side effects were mainly gastrointestinal in nature and were more common during the updosing phase than the maintenance phase. No episodes of anaphylaxis were observed in this study. CONCLUSION: Peanut OIT seemed to be effective and safe in our cohort of Singaporean children.
The importance of early peanut ingestion in the prevention of peanut allergy.
Peanut allergy appears to have increased in prevalence, is often severe and is typically life-long. Therefore, reducing its incidence through a primary prevention strategy is a priority. Guidelines on peanut introduction have evolved with time and given evidence of peanut allergy risk reduction with early infant ingestion exposure, the current US advice promotes early introduction for infants, particularly targeting those at highest risk. Areas covered: This article describes the evolution of peanut introduction guidelines in infants in the US, as shaped by key research over the last 20-30 years and culminates in the landmark LEAP study. It also compares and contrasts current iterations of peanutintroduction guidelines in infants globally. Finally, the early successes and barriers of implementation of early peanut introduction guidelines are discussed. We included literature from original articles, reviews, and consensus guidelines found in database searches through December 2018. Expert commentary: LEAP guideline implementation has proven to be successful, in the study setting, in decreasing the incidence of peanut allergy. However, its implementation in the community has been met with obstacles including low awareness among stakeholders, and access to testing when needed.
Effect of Epicutaneous Immunotherapy vs Placebo on Reaction to Peanut Protein Ingestion Among Children With Peanut Allergy: The PEPITES Randomized Clinical Trial.
IMPORTANCE: There are currently no approved treatments for peanut allergy. OBJECTIVE: To assess the efficacy and adverse events of epicutaneous immunotherapy with a peanut patch among peanut-allergic children. DESIGN, SETTING, AND PARTICIPANTS: Phase 3, randomized, double-blind, placebo-controlled trial conducted at 31 sites in 5 countries between January 8, 2016, and August 18, 2017. Participants included peanut-allergic children (aged 4-11 years [n = 356] without a history of a severe anaphylactic reaction) developing objective symptoms during a double-blind, placebo-controlled food challenge at an eliciting dose of 300 mg or less of peanut protein. INTERVENTIONS: Daily treatment with peanut patch containing either 250 μg of peanut protein (n = 238) or placebo (n = 118) for 12 months. MAIN OUTCOMES AND MEASURES: The primary outcome was the percentage difference in responders between the peanut patch and placebo patch based on eliciting dose (highest dose at which objective signs/symptoms of an immediate hypersensitivity reaction developed) determined by food challenges at baseline and month 12. Participants with baseline eliciting dose of 10 mg or less were responders if the posttreatment eliciting dose was 300 mg or more; participants with baseline eliciting dose greater than 10 to 300 mg were responders if the posttreatment eliciting dose was 1000 mg or more. A threshold of 15% or more on the lower bound of a 95% CI around responder rate difference was prespecified to determine a positive trial result. Adverse event evaluation included collection of treatment-emergent adverse events (TEAEs). RESULTS: Among 356 participants randomized (median age, 7 years; 61.2% male), 89.9% completed the trial; the mean treatment adherence was 98.5%. The responder rate was 35.3% with peanut-patch treatment vs 13.6% with placebo (difference, 21.7% [95% CI, 12.4%-29.8%; P < .001]). The prespecified lower bound of the CI threshold was not met. TEAEs, primarily patch application site reactions, occurred in 95.4% and 89% of active and placebo groups, respectively. The all-causes rate of discontinuation was 10.5% in the peanut-patch group vs 9.3% in the placebo group. CONCLUSIONS AND RELEVANCE: Among peanut-allergic children aged 4 to 11 years, the percentage difference in responders at 12 months with the 250-μg peanut-patch therapy vs placebo was 21.7% and was statistically significant, but did not meet the prespecified lower bound of the confidence interval criterion for a positive trial result. The clinical relevance of not meeting this lower bound of the confidence interval with respect to the treatment of peanut-allergic children with epicutaneous immunotherapy remains to be determined.
Mouse strain differences in response to oral immunotherapy for peanut allergy.
BACKGROUND: Promising therapies for food allergy are emerging, mostly based on animal experimentation. However, different mouse strains are used, which may make it hard to compare experiments. The current study investigated whether the immunological differences between C3H/HeOuJ (C3H) and BALB/c mice lead to differences in efficacy of peanut-specific immunotherapy. METHODS: After sensitization using peanut extract (PE), C3H and BALB/c mice received oral immunotherapy (OIT) by intragastric dosing for three weeks. Hereafter, mice were exposed to PE via the intradermal, intragastric and intraperitoneal route, to determine allergic outcomes. Furthermore, PE-specific antibody and cytokine production were determined and the number of various immune cells at different time points during the study were measured. RESULTS: OIT protected C3H mice against anaphylaxis, whereas no anaphylaxis was seen in BALB/c mice. In contrast, OIT induced an increase in MMCP-1 levels in BALB/c mice but not in C3H mice. No effect of OIT on the acute allergic skin response was observed in either strain. Specific antibody responses showed similar patterns in both strains for IgA and IgG1. IgE levels were a tenfold higher in BALB/c mice and after the intragastric challenge (day 70) OIT-treated BALB/c mice showed induced IgE levels. Moreover, in C3H mice IgG2a levels were higher and increased in response to OIT and challenges. After the final challenge, but not at other timepoints MLN-derived lymphocytes from OIT-treated BALB/c mice produced less IL-13 and IL-5 compared to control-treated mice, whereas no differences were seen in case of C3H mice. CONCLUSIONS: Taken together, these results show that the C3H strain is more suitable to study clinical outcomes of OIT, whereas the BALB/c strain is more optimal to study T cell responses.
A critical review of the specifications and performance of antibody and DNA-based methods for detection and quantification of allergens in foods.
Despite the availability of a large number of antibody and DNA based methods for detection and quantification of allergens in food there remain significant difficulties in selecting the optimum technique to employ. Published methods from research groups mostly contain sufficient detail concerning target antigen, calibration procedures and method performance to allow replication by others. However, routine allergen testing by the food industry relies upon commercialised test kits and frequently the suppliers provide disappointingly little specification detail on the grounds that this is proprietary information. In this review we have made a critical assessment of the published literature describing the performance of both commercial and non-commercial test kits for food allergens over the period 2008-2018. Mass spectrometric methods, which have the potential to become reference methods for allergens, are not covered in this review. Available information on the specifications of commercial ELISA and LFD test kits are tabulated for milk, egg and peanut allergens, where possible linking to publications concerning collaborative studies and proficiency testing. For a number of commercial PCR test kits, specifications provided by manufacturers for detection of a small selection of allergen are tabulated. In conclusion we support the views of others of the critical need for allergen reference materials as the way forward to improve the comparability of different testing strategies in foods.
Age at introduction to complementary solid food and food allergy and sensitization: a systematic review and meta‐analysis.
BACKGROUND AND OBJECTIVE: An infant's age at introduction of complementary solids may contribute to food allergy. We aimed to synthesize the literature on the association between age at introduction of complementary solids, excluding milk products, and food allergy and sensitization. DESIGN: We searched the electronic databases PubMed and EMBASE (January 1946-February 2017) using solid food, allergy and sensitization terms. METHODS: Two authors selected papers according to inclusion criteria, identifying 16 cohort studies, 1 case-control study and 8 randomized controlled trials (RCTs). Pooled effects across studies were estimated using random-effects meta-analysis. RESULTS: Cohort studies - Introducing complementary solids at age ≥4 months versus <4 months was not associated with food allergy (OR 1.22; 95%CI, 0.76-1.96) but was associated with food sensitization (OR 1.93; 95%CI 1.57-2.38). First exposure from age 4-6 months versus <4 months was not associated with food allergy (OR 1.01; 95%CI, 0.64-1.60) but was associated with food sensitization (OR 2.46; 95%CI 1.55-3.86). RCTs - Egg exposure from age 4 months was associated with reduced egg allergy (OR 0.63, 95%CI, 0.44-0.90) and sensitization (OR 0.76, 95%CI, 0.51-0.95). Peanut exposure from age 4 months compared to delayed exposure was associated with reduced peanut allergy (OR 0.28, 95%CI 0.14-0.57). CONCLUSIONS: We found no evidence from observational studies that introducing solids before 4 months protected against food allergy, but there was evidence for protection against food sensitization. From RCTs, introducing egg from 4-6 months and peanut from 4-11 months, reduced the risk of egg allergy, peanut allergy and egg sensitization.
Epicutaneous peanut patch device for the treatment of peanut allergy.
Food allergy prevalence has increased in recent decades, which has mobilized efforts to develop treatment alternatives. Epicutaneous immunotherapy (EPIT) is a novel method that involves transdermal administration of peanut allergen with the objective to induce tolerance. Recent clinical trials have shown its efficacy at increasing the eliciting dose in children with a favorable safety profile. Areas covered: This review covers the proposed mechanism of action of EPIT in murine models and humans, efficacy and safety data from clinical trials with peanut EPIT, and a discussion on its potential role in the future management of peanut allergy. Expert opinion: With the recent completion of pivotal trials for peanut EPIT and upcoming marketing, the main question for clinicians and food allergic patients is how to define its role in the management of peanut allergy and how it compares to oral immunotherapy (OIT). Like OIT, EPIT seems to promote immunological tolerance over time. However, EPIT could lack the rapid mast-cell desensitization induced by the progressive intake of food in OIT, which explains differences in short-term outcomes and safety profiles. Head-to-head and long-term comparison of real-life efficacy with regards to sustained unresponsiveness will help define its place in the food allergy arsenal.
Evidence for a Role of TGF-β-Activated Kinase 1 and MAP3K7 Binding Protein 3 in Peanut-Specific T-Cell Responses.
Peanut allergy is considered to be the most common cause for food-induced anaphylaxis. Currently, no approved treatment is available. Avoidance is the only measure to prevent anaphylactic reactions to peanuts. T-helper cells are of special importance for the sensitization process and the maintenance of allergic inflammation. Identifying markers of allergen-specific T-cell responses may help to develop novel treatment approaches. Therefore, we aimed to define new T-cell target genes in Ara h 2-specific T cells and to investigate the possibility of using them as biomarkers of peanut allergy in peripheral blood mononuclear cells (PBMCs). We performed whole mRNA array analysis (whole human genome oligo microarray) of in vitro expanded Ara h 2-specific T cells (CFSElowCD3+CD4+) from 5 peanut-allergic (PA) and 5 non-peanut-sensitized individuals. Expression of selected genes as a result of a two-step bioinformatic approach was confirmed in a second cohort by quantitative PCR. TGF-β- activated kinase 1 and MAP3K7 binding protein 3 (TAB3), calcium/calmodulin-dependent protein kinase type IV (CAMK4) and HemK methyltransferase family member 1 (HEMK1) were significantly upregulated in Ara h 2-specific T cells of PA patients. In addition, the expression of these genes was also assessed in unstimulated PBMCs from a cohort (n = 43) of PA, atopic non-PA, and nonatopic controls. Interestingly, in unstimulated PBMCs, TAB3 expression was significantly downregulated in PA patients compared to atopic non-PA individuals. Thus, TAB3 may play a significant role at the level of T-cell activation and may also be a candidate biomarker for PA.
Microbial Adjuncts for Food Allergen Immunotherapy.
PURPOSE OF REVIEW: Food allergen immunotherapy may benefit from adjunct therapies to enhance safety and efficacy. We review preclinical studies investigating the effects of probiotics and other microbial-based interventions on oral tolerance, describe the human clinical trial evidence thus far for microbial adjuncts, and discuss steps for translating research findings in this area to clinical therapy. RECENT FINDINGS: Murine studies support that microbial-based interventions confer protection against sensitization and may augment treatment efficacy for food allergy. Microbial adjunct therapies can promote regulatory T cells and modulate Th1 vs. Th2 responses. There is a wide array of novel modalities utilizing microbial components. Ongoing efforts are focused on translating preclinical data into potential treatments. Probiotics, prebiotics, and microbial components have all been examined as microbial adjunct therapies in murine models of food allergy. The effects of probiotics appear to be strain-specific. Prebiotics and bacterial components are innovative modalities to modulate oral tolerance. Better characterization of dysbiosis in human cohorts with food allergy, deeper mechanistic understanding of microbial adjunct therapies, safety evaluation, and careful clinical trial design will be crucial for the development of microbial adjuncts for food allergen immunotherapy. Microbial adjunct therapies have the potential to enhance the efficacy, safety, and durability of food allergen immunotherapy.