Preventing Peanut Allergy: Where Are We Now?

Risk subgroups and intervention effects among infants at high risk for peanut allergy: A model for clinical decision making

BACKGROUND

The Learning Early About Peanut Allergy (LEAP) trial showed that early dietary introduction of peanut reduced the risk of developing peanut allergy by age 60 months in infants at high risk for peanut allergy. In this secondary analysis of LEAP data, we aimed to determine risk subgroups within these infants and estimate their respective intervention effects of early peanut introduction.

METHODS

LEAP raw data were retrieved from ITNTrialShare.org. Conditional random forest was applied to participants in the peanut avoidance arm to select statistically important features for the classification and regression tree (CART) analysis to group infants based on their risk of peanut allergy at 60 months of age. Intervention effects were estimated for each derived risk subgroup using data from both arms. Our main model was generated based on baseline data when the participants were 4-11 months old. Specific IgE measurements were truncated to account for the limit of detection commonly used by laboratories in clinical practice.

RESULTS

The model found infants with higher predicted probability of peanut allergy at 60 months of age had a similar relative risk reduction, but a greater absolute risk reduction in peanut allergy with early introduction of peanut, than those with lower probability. The intervention effects were significant across all risk subgroups. Participants with baseline peanut sIgE ≥0.22 kU/L (n = 78) had an absolute risk reduction of 40.4% (95% CI 27.3, 51.9) whereas participants with baseline peanut sIgE<0.22 kU/L and baseline Ara h 2 sIgE <0.10 kU/L (n = 226) had an absolute risk reduction of 6.5% (95% CI 2.6, 11.0). These findings were consistent in sensitivity analyses using alternative models.

CONCLUSION

In this study, risk subgroups were determined among infants from the LEAP trial based on the probability of developing peanut allergy and the intervention effects of early peanut introduction were estimated. This may be relevant for further risk assessment and personalized clinical decision-making.

A novel IgE epitope-specific antibodies-based sandwich ELISA for sensitive measurement of immunoreactivity changes of peanut allergen Ara h 2 in processed foods

Background

Peanut is an important source of dietary protein for human beings, but it is also recognized as one of the eight major food allergens. Binding of IgE antibodies to specific epitopes in peanut allergens plays important roles in initiating peanut-allergic reactions, and Ara h 2 is widely considered as the most potent peanut allergen and the best predictor of peanut allergy. Therefore, Ara h 2 IgE epitopes can serve as useful biomarkers for prediction of IgE-binding variations of Ara h 2 and peanut in foods. This study aimed to develop and validate an IgE epitope-specific antibodies (IgE-EsAbs)-based sandwich ELISA (sELISA) for detection of Ara h 2 and measurement of Ara h 2 IgE-immunoreactivity changes in foods.

Methods

DEAE-Sepharose Fast Flow anion-exchange chromatography combining with SDS-PAGE gel extraction were applied to purify Ara h 2 from raw peanut. Hybridoma and epitope vaccine techniques were employed to generate a monoclonal antibody against a major IgE epitope of Ara h 2 and a polyclonal antibody against 12 IgE epitopes of Ara h 2, respectively. ELISA was carried out to evaluate the target binding and specificity of the generated IgE-EsAbs. Subsequently, IgE-EsAbs-based sELISA was developed to detect Ara h 2 and its allergenic residues in food samples. The IgE-binding capacity of Ara h 2 and peanut in foods was determined by competitive ELISA. The dose-effect relationship between the Ara h 2 IgE epitope content and Ara h 2 (or peanut) IgE-binding ability was further established to validate the reliability of the developed sELISA in measuring IgE-binding variations of Ara h 2 and peanut in foods.

Results

The obtained Ara h 2 had a purity of 94.44%. Antibody characterization revealed that the IgE-EsAbs recognized the target IgE epitope(s) of Ara h 2 and exhibited high specificity. Accordingly, an IgE-EsAbs-based sELISA using these antibodies was able to detect Ara h 2 and its allergenic residues in food samples, with high sensitivity (a limit of detection of 0.98 ng/mL), accuracy (a mean bias of 0.88%), precision (relative standard deviation < 16.50%), specificity, and recovery (an average recovery of 98.28%). Moreover, the developed sELISA could predict IgE-binding variations of Ara h 2 and peanut in foods, as verified by using sera IgE derived from peanut-allergic individuals.

Conclusion

This novel immunoassay could be a user-friendly method to monitor low level of Ara h 2 and to preliminary predict in vitro potential allergenicity of Ara h 2 and peanut in processed foods.

Peanut butter feeding induces oral tolerance in genetically diverse collaborative cross mice

Background

Early dietary introduction of peanut has shown efficacy in clinical trials and driven pediatric recommendations for early introduction of peanut to children with heightened allergy risk worldwide. Unfortunately, tolerance is not induced in every case, and a subset of patients are allergic prior to introduction. Here we assess peanut allergic sensitization and oral tolerance in genetically diverse mouse strains.

Objective

We aimed to determine whether environmental adjuvant-driven airway sensitization and oral tolerance to peanut could be induced in various genetically diverse mouse strains.

Methods

C57BL/6J and 12 Collaborative Cross (CC) mouse strains were fed regular chow or ad libitum peanut butter to induce tolerance. Tolerance was tested by attempting to sensitize mice via intratracheal exposure to peanut and lipopolysaccharide (LPS), followed by intraperitoneal peanut challenge. Peanut-specific immunoglobulins and peanut-induced anaphylaxis were assessed.

Results

Without oral peanut feeding, most CC strains (11/12) and C57BL/6J induced peanut-specific IgE and IgG1 following airway exposure to peanut and LPS. With oral peanut feeding none of the CC strains nor C57BL/6J mice became sensitized to peanut or experienced anaphylaxis following peanut challenge.

Conclusion

Allergic sensitization and oral tolerance to peanut can be achieved across a range of genetically diverse mice. Notably, the same strains that became allergic via airway sensitization were tolerized by feeding high doses of peanut butter before sensitization, suggesting that the order and route of peanut exposure are critical for determining the allergic fate.

Early Peanut Introduction in Primary Care: Evaluation of a Multicomponent Intervention

OBJECTIVE

To determine whether a multicomponent intervention focused on early peanut introduction was associated with a lower peanut allergy incidence in young children.

METHODS

The study cohort comprised all children born January 1, 2013 through December 31, 2018 receiving care at a large health care organization. Intervention activities occurred over 16 months and included provider educational programs, electronic health record tools, and new patient instructions. We used an interrupted time series design to assess whether peanut allergy incidence differed across 3 time periods (preintervention, interim, postintervention) among high- and low-risk children. The primary outcome was incident peanut allergy by age 24 months, defined as peanut allergy in the allergy field or active problem list plus a positive supportive test. Severe eczema and/or egg allergy presence defined high-risk. Because the study was conducted as part of routine care, it was not feasible to measure what counseling clinicians provided, or how and when parents fed their children peanut-containing foods.

RESULTS

In a cohort of 22,571 children, the percent with peanut allergy by age 24 months was 17.3% (116 of 671) among high-risk and 0.8% (181 of 21,900) among low-risk children. In multivariate analyses, the adjusted peanut allergy rate per 100 person-years was not significantly different across study periods among high-risk (9.6 preintervention, 11.7 interim, and 9.9 postintervention, P = .70) or low-risk (0.5 preintervention, 0.7 interim, and 0.5 postintervention, P = .17) children.

CONCLUSIONS

In a community-based setting, the incidence of peanut allergy did not decline following a multicomponent intervention focused on early peanut introduction.

Tree nut introduction in a peanut-allergic child: To eat, to screen, or to avoid?

There is no defined standard of care around tree nut introduction in a peanut-allergic child, and the role of screening prior to tree nut introduction is controversial. There is some evidence that peanut-allergic children are at increased risk of tree nut allergy, with approximately 23-68% of children with co-existent peanut/tree nut allergy. In some studies, it has been shown that tree nut allergy in children has the potential to be a severe allergy. However, this appears to be age-specific as infant anaphylaxis in general tends to be milder, and there has been no fatality reported on the first ingestion of an allergen in infancy. Familial hesitancy has been identified as a possible condition for undertaking screening tests prior to allergen introduction. Indeed, there has been limited evidence that caregiver hesitancy may exist in peanut-allergic families with tree nut introduction. However, pre-emptive screening has the potential to overdiagnose tree nut allergy and delay introduction (which could paradoxically increase risk). As a result, the decision is best made in the context of shared decision-making and patient preference-sensitive care.

Overview of oral tolerance induction for prevention of food allergy-Where are we now?

Oral tolerance induction through early introduction of allergenic food has proven effective in randomized controlled trials. This new approach to weaning has been incorporated into many national and international infants' feeding guidelines. However, there are questions that require further discussion, such as, which foods should be introduced early, should the intervention be targeted to infants at high-risk or to the general population, and what is the ideal timing for early food introduction. This review examines the extent to which recent trials address these critical questions and highlights areas where further research is required.

International Peanut Allergy Prevention, 6 Years After the Learning Early About Peanut Study

Six years ago, the Learning Early About Peanut (LEAP) trial findings helped fundamentally shift the paradigm of peanut allergy prevention. Although the results of LEAP are well accepted, policy-makers, caregivers, and clinicians struggle with how best to implement and apply the study's key findings in clinical practice. Differences in guidelines highlight issues related to peanut allergy prevention implementation, including caregiver acceptability, cost, fidelity, feasibility, appropriateness, and adoption. The goals of this rostrum are to review how the LEAP study has informed international peanut allergy prevention policy, as well as to review the strengths and ongoing controversies in peanut allergy prevention implementation.

Structural Phylogeny of Different Allergens May Reveal Common Epitopic Footprint

BACKGROUND

The incidence of allergy is increasing at an alarming rate for the last few decades.

OBJECTIVE

Our present study is focused on finding out the structurally homologous motifs present in different proteinaceous allergens Methods: Significant number of protein sequences and their corresponding structures of various pollen, fungal, bacterial, and food allergens were retrieved, and the sequence and structural identity were analyzed.

RESULTS

Intra- and inter-sequence and their structural analysis of the proteinaceous allergens, resulted in no significant relationships among them. A few, but not negligible number of high structural similarities were observed within different groups of allergens from fungus, angiosperms, and animals (Aves and Mammalia).

CONCLUSION

Our in silico study on thirty-six different allergens showed a significant level of structural similarities among themselves, regardless of their sequences.

Food Allergy Prevention: More Than Peanut

Given an apparent increase in food allergies worldwide, the focus on prevention strategies has intensified. Following the Learning Early About Peanut study, there is now a widespread acceptance that peanut should be introduced promptly into the diet of high-risk infants. However, most food allergies are caused by triggers other than peanut and additional prevention strategies are being evaluated. The appreciation of the role of an impaired skin barrier in the process of food sensitization and subsequent allergy has led to a spectrum of dermatologically orientated studies. Other prevention strategies address the role of the microbiome, dietary components, and other modifiable risk factors. With regard to early introduction of foods other than peanut, studies are heterogeneous in design and governmental and professional society response to the early introduction trials has varied, ranging from new guidelines confining advice specifically to peanut, to ones recommending prompt introduction of a broad spectrum of allergenic foods. Much remains to be determined with regard to the acceptability and uptake of the new guidelines and their impact on infant feeding behavior and food allergy outcomes. This review discusses the panoply of prevention approaches, their promise, and limitations.

Food Allergy from Infancy Through Adulthood

Food allergies are the result of immune responses that cause adverse reactions to foods. Immune responses to foods may produce a spectrum of symptoms and disorders, including acute allergic reactions and anaphylaxis, food protein-induced allergic proctocolitis, food protein-induced enterocolitis syndrome, food-dependent, exercise-induced anaphylaxis, and oral allergy syndrome (pollen-food allergy syndrome). Food-allergic responses also contribute to chronic inflammatory disorders such as eosinophilic esophagitis and atopic dermatitis. Although food allergy affects people from infancy through adulthood, there are allergic features that differ according to age (ie, presentation, triggers, and natural course) and have important implications for diagnosis, prognosis, and management. New food allergies can develop at any age, and we propose similarities in the etiology of de novo food allergy whether in infancy or adulthood. The approach to managing food allergy changes dramatically over the life course, and physicians and patients must respond accordingly to optimize care. Food allergy therapies are emerging, and the efficacy and safety of these interventions could differ by age group of those treated. In this review, we highlight interesting observations on the etiology and characteristics of food allergy presenting at different ages and discuss clinical management as it relates to life stage.

Cow's milk allergy prevention

OBJECTIVE

Scoping review on IgE-mediated cow's milk allergy prevention.

DATA SOURCES

Literature search of PubMed database and gray literature.

STUDY SELECTIONS

Peer-reviewed relevant observational and randomized controlled studies in the pediatric population in the English language were selected and reviewed.

RESULTS

There is increasing literature supporting the role of early and ongoing cow's milk ingestion in the prevention of cow's milk allergy. The studies supporting a preventive role with early cow's milk ingestion suggest cow's milk introduction at a very early age (most within the first month of life), suggesting the possibility of a different mechanism of sensitization than other common allergens. It is possible that gut colonization and the diversity and intensity of microbial exposure may play a role in inducing cow's milk tolerance. It is also possible that vitamin D may have a role in modulating those immune functions.

CONCLUSION

Further research regarding the role that early cow's milk ingestion plays in the prevention of cow's milk allergy is required, and questions remain. The absolute amount required for tolerance is unclear. Studies in higher risk populations are required. However, there is an intriguing and increasingly more pervasive association between early ongoing cow's milk ingestion and cow's milk allergy prevention.

Early Peanut Protein Introduction in Clinical Practice

PURPOSE

New multiple agency recommendations have encouraged the early introduction of peanut protein (PP) in high-risk children to decrease peanut allergies. However, many providers are hesitant to use these recommendations. Our objective was to increase the recommendation of new guidelines by providers during routine infant care and evaluate caregiver acceptance of early PP introduction.

DESIGN AND METHODS

This QI project focused on changing providers' knowledge and attitudes as a means to change practice using the "Plan-Do-Study-Act" model. Following provider educational sessions in 4 clinical sites providers and caregivers were questioned about instruction on the introduction of PP. Pre and post educational intervention data were collected from providers using chart audit and caregivers' report through the modified Promoting Healthy Development Survey (PHDS).

RESULTS

The educational intervention was effective in increasing provider knowledge (p < .05), providers' dissemination of knowledge to caregivers through provider report (p < .001) and caregiver report (p < .05).

CONCLUSIONS

Education increased providers' knowledge about the safety and importance of early introductions of PP, and allayed fears about initiating an allergic reaction. The increased provider recommendation to caregivers was validated by both provider and caregiver report. Caregivers felt comfortable initiating peanut protein.

PRACTICE IMPLICATIONS

Provider education led to increased recommendation to caregivers on early introduction of PP and increased caregiver comfort introducing PP.

Management of Peanut Allergy

Peanut allergy is a growing public health concern in westernized countries. Peanut allergy is characterized as an often severe and lifelong allergy, which can have detrimental effects on quality of life and trigger anxiety. Although multiple therapeutic options are emerging, the focus of current management strategies is strict peanut avoidance and carriage of self-injectable epinephrine. The greatest risk of reacting to peanut comes from direct ingestion, whereas casual skin contact or airborne exposure is highly unlikely to provoke significant symptoms. Patients and families must be educated about how to best execute strict peanut avoidance through careful label reading as well as how to understand and address likely and unlikely risk with regard to peanut exposure in public, in particular when dining outside of the home and for children attending school or child care. This review discusses the risk of exposure in public such as at school or on an airplane and how such risk can be abated, situations and scenarios when dining out of the house that may pose more risks than others, the essentials of US and EU label reading laws with particular emphasis on precautionary labeling and the risk implied by such, quality of life and psychosocial issues that may affect the peanut allergic individual and family, and a discussion of how risk may differ and evolve based on the patient's age.

Covalent conjugation with (-)-epigallo-catechin 3-gallate and chlorogenic acid changes allergenicity and functional properties of Ara h1 from peanut

Ara h1 is a major allergen from peanut. We investigated the effect of covalent conjugation of Ara h1 and dietary polyphenols on allergenicity and functional properties of Ara h1. Enzyme-linked immunosorbent assay revealed that the covalent conjugation of dietary polyphenols significantly reduced the IgE binding capacity of Ara h1. Covalent binding of dietary polyphenols with Ara h1 reduced histamine release by 40% in basophils. The decreased IgE binding capacity of Ara h1 could be ascribed to changes in protein conformation. The IgE epitope of Ara h1 might be blocked by polyphenols at the binding site. Analysis of pepsin digestion of Ara h1-polyphenol conjugates indicated that the covalent binding increased pepsin digestibility and reduced IgE binding capacity. Furthermore, covalent conjugation of Ara h1 with polyphenols decreased denaturation temperature and increased antioxidant activity. Ara h1 conjugated with polyphenols may be a promising approach for reducing the allergenicity of Ara h1.

Current Controversies and Future Prospects for Peanut Allergy Prevention, Diagnosis and Therapies

Peanut allergy has increased substantially in the past few decades, both in developed and developing countries. Peanut allergy has become a major public health concern, affecting up to 1 in 50 children, with repercussions for school and airline policies. Recent research findings have shown that, contrary to the long-standing teaching of "delayed" introduction of allergens, early introduction of peanut protein is of benefit as an allergy prevention strategy, especially in high-risk cases. Ideal dose, frequency and duration of "proactive" peanut therapy for maximum protection remain to be determined in order for it to become acceptable and practical on a large scale. Logistics around widespread screening of high-risk patients remain complex. The correct diagnosis of peanut allergy is crucial and diagnostic tests have been fine-tuned in the past 2 decades in order to help differentiate true allergy from false-positive sensitization through cross-reactivity. Component-resolved diagnostics have become routinely available, and the use of basophil activation tests has increased, although standardization and availability remain issues. Future tests, including epitope testing and histamine-release assays, promise to be even more specific in ruling out false positives and reducing the need for incremental food challenges. Stringent peanut avoidance and prompt treatment of reactions remain the cornerstone of treatment. The concept of exposing the allergic body to small amounts of peanut protein in a cautious, orderly, escalating fashion in the form of desensitization has been widely applied in the past 10-15 years, mainly in the research domain, but of late spilling over into every-day practice. However, desensitization does not equate to a cure, and has significant safety concerns and practical ramifications; probably requiring lifelong-controlled peanut ingestion for ongoing protection. Further strategies to enhance the safety and efficacy of immunotherapy are under exploration, many with a non-specific immune-modifying effect. Despite recent advances in peanut allergy, we still need to go back to basics with accurate diagnosis, nutritional counselling, well-organized allergy action plans and accessible emergency kits.

Earlier ingestion of peanut after changes to infant feeding guidelines: The EarlyNuts study

BACKGROUND

Randomized controlled trials demonstrate that timely introduction of peanut to infants reduces the risk of peanut allergy. However, much debate remains regarding how to best achieve earlier peanut introduction at the population level. Our previous study in 2007-2011 (HealthNuts, n = 5300) indicated that few infants were consuming peanut in the first year. Australian infant feeding guidelines were updated in 2016 to recommend introducing peanut before 12 months for all infants. There were no data available on the subsequent effect on peanut introduction or peanut reactions.

OBJECTIVE

We sought to assess the consequences of a nonscreening approach to allergenic food introduction in a population-based sample of infants in their first year of life.

METHODS

EarlyNuts is a population-based, cross-sectional study of 12-month-old infants in Melbourne, Australia, recruited by using an identical sampling frame and methods to HealthNuts (72% response rate vs 73% response rate in HealthNuts). We report here on the first 860 participants recruited between November 2016 and October 2018.

RESULTS

Most infants (88.6%; 95% CI, 86.1% to 90.7%) had introduced peanut by 12 months (median age, 6 months), an increase from 28.4% (95% CI, 27.2% to 29.7%) in the HealthNuts study. By 12 months, the majority of these (76.4%) had consumed peanut more than 4 times, and 28% were eating peanut more than once per week. Preliminary results on parent-reported reactions show that 4.0% of those consuming peanut by 12 months had possible IgE-mediated reactions.

CONCLUSIONS

There has been a striking shift toward earlier peanut introduction, with a 3-fold increase in peanut introduction by age 1 year in 2018 compared with 2007-2011.

Timing of Food Introduction and the Risk of Food Allergy

Given that the prevalence of pediatric IgE-mediated food allergies (FA) has followed a substantive increase in recent decades, nowadays, a research challenge is to establish whether the weaning strategy can have a role in FA prevention. In recent decades, several studies have demonstrated that delayed exposure to allergenic foods did not reduce the risk of FA, leading to the publication of recent guidelines which recommend against delaying the introduction of solid foods after 4–6 months of age, both in high- and low-risk infants, in order to prevent food allergy. In the present review, focusing on cow’s milk protein, hen’s eggs, peanuts, soy, wheat and fish, we describe the current scientific evidence on the relationship between timing of these foods’ introduction in infants’ diet and allergy development.