Managing Cross-Reactivity in Those with Peanut Allergy

Legume Allergens Pea, Chickpea, Lentil, Lupine and Beyond

PURPOSE OF THE REVIEW

In the last decade, an increasing trend towards a supposedly healthier vegan diet could be observed. However, recently, more cases of allergic reactions to plants and plant-based products such as meat-substitution products, which are often prepared with legumes, were reported. Here, we provide the current knowledge on legume allergen sources and the respective single allergens. We answer the question of which legumes beside the well-known food allergen sources peanut and soybean should be considered for diagnostic and therapeutic measures.

RECENT FINDINGS

These "non-priority" legumes, including beans, pea, lentils, chickpea, lupine, cowpea, pigeon pea, and fenugreek, are potentially new important allergen sources, causing mild-to-severe allergic reactions. Severe reactions have been described particularly for peas and lupine. An interesting aspect is the connection between anaphylactic reactions and exercise (food-dependent exercise-induced anaphylaxis), which has only recently been highlighted for legumes such as soybean, lentils and chickpea. Most allergic reactions derive from IgE cross-reactions to homologous proteins, for example between peanut and lupine, which is of particular importance for peanut-allergic individuals ignorant to these cross-reactions. From our findings we conclude that there is a need for large-scale studies that are geographically distinctive because most studies are case reports, and geographic differences of allergic diseases towards these legumes have already been discovered for well-known "Big 9" allergen sources such as peanut and soybean. Furthermore, the review illustrates the need for a better molecular diagnostic for these emerging non-priority allergen sources to evaluate IgE cross-reactivities to known allergens and identify true allergic reactions.

Development of validated sandwich ELISA for detecting peanut allergen Ara h 3 in food

Peanut is an important food that can cause food allergies, often leading to moderate and severe allergic symptoms such as skin rashes, asthma, and even anaphylactic shock.Research indicates that Ara h 3 is one of the major peanut allergen. In order to establish a simple analytical method for detecting Ara h 3, we developed a sandwich enzyme-linked immunosorbent assay (ELISA) with antibodies that were induced from purified Ara h 3. The experimental results showed that the purified Ara h 3 had good purity, and we successfully prepared capture and detection antibodies. The method established in this study exhibited high specificity and did not cross-react with soybeans, cashew nuts, and sesame. For validation, including precision, recovery and sensitivity were in good condition. We also detected the Ara h 3 in peanut related foods. Overall, the ELISA developed in this study is a reliable method for Ara h 3 detection.

Diagnosis and Management of Pollen Food Allergy Syndrome to Nuts

Oral allergy syndrome or pollen food allergy syndrome (PFAS) represents a common clinical conundrum when the reported trigger food is a tree nut (usually almond or hazelnut) or peanut. The PFAS may give rise to uncertainty about the potential severity of the future reactions, indications for prescribing epinephrine, and the extent of the necessary dietary avoidance. As a food allergy, secondary to cross-reactivity with airborne pollen, PFAS usually manifests toward the end of the first decade of life as contact urticaria of the oropharyngeal mucous membranes. Molecular allergology facilitates diagnosis and risk stratification by establishing the profile of sensitization. Exclusive sensitization to pathogenesis-related proteins family 10 (PR10) and profilins indicates that signs and symptoms are due to PFAS, whereas sensitization to seed storage proteins with or without sensitization to PR10 and profilins may indicate a more severe primary nut allergy phenotype. Management relies on avoidance of the specific nut trigger, advice on the likelihood of more severe local or systemic symptoms, and treatment of reactions according to the severity. Future studies are needed to better delineate the risk of systemic reactions in individuals with nut PFAS and to establish the role of food or pollen allergen immunotherapy for the prevention or moderation of this condition.

Allergenicity of alternative proteins: research hotspots, new findings, evaluation strategies, regulatory status, and future trends: a bibliometric analysis

As the world population rises, the demand for protein increases, leading to a widening gap in protein supply. There is an unprecedented interest in the development of alternative proteins, but their allergenicity has raised consumer concerns. This review aims to highlight and correlate the current research status of allergenicity studies on alternative proteins based on previously published studies. Current research keywords, hotspots and trends in alternative protein sensitization were analyzed using a mixed-method approach that combined bibliometric analysis and literature review. According to the bibliometric analysis, current research is primarily focused on food science, agriculture, and immunology. There are significant variations in the type and amount of allergens found in alternative proteins. A significant amount of research has been focused on studying plant-based proteins and the cross-reactivity of insect proteins. The allergenicity of alternative proteins has not been studied extensively or in depth. The allergenicity of other alternative proteins and the underlying mechanisms warrant further study. In addition, the lack of a standardized allergy assessment strategy calls for additional efforts by international organizations and collaborations among different countries. This review provides new research and regulatory perspectives for the safe utilization of alternative proteins in human food systems.

Pollen Sensitization Can Increase the Allergic Reaction to Non-Cross-Reactive Allergens in a Soy-Allergic Patient

During and after the pollen season, an increase in food-triggered allergic symptoms has been observed in pollen-food syndrome patients, possibly due to seasonal boosting of pollen-IgE levels. It has been suggested that consumption of birch-pollen-related foods plays a role in seasonal allergenic inflammation. However, whether this increased pollen sensitization during the pollen season can also affect the allergenicity of allergens that are non-cross-reactive with birch pollen remains in question. This study presents the case of a patient with soy allergy and pollinosis, who experiences worsening of gastrointestinal (GI) symptoms during the birch pollen season even though the eliciting food factor does not cross-react with birch pollen allergens and their homologs (e.g., Bet v 1 and Gly m 4). The results showed a notable increase in sIgE for Gly m 4 (3.3 fold) and Bet v 1 (2.6 fold) during the birch pollen season compared to outside the birch pollen season, while Gly m 5 and Gly m 6 showed only a slight increase (1.5 fold). The basophil activation test (BAT) showed that in this patient Gly m 5 and Gly m 6 are clinically relevant soy allergens, which correlates with the reported clinical symptoms to processed soy. Moreover, the BAT against raw soy shows an increase in basophil activation during the birch pollen season and a negative basophil activation result outside the birch pollen season. Thus, the worsening of GI symptoms could possibly be due to an increase in IgE receptors, an over-reactive immune system, and/or significant intestinal allergic inflammation. This case highlights the importance of including allergens that do not cross-react with birch pollen and using a functional assay such as the BAT to evaluate clinical relevance when assessing birch pollen seasonal influence on soy allergenicity.

Peanut Allergenicity: An Insight into Its Mitigation Using Thermomechanical Processing

Peanuts are the seeds of a legume crop grown for nuts and oil production. Peanut allergy has gained significant attention as a public health issue due to its increasing prevalence, high rate of sensitization, severity of the corresponding allergic symptoms, cross-reactivity with other food allergens, and lifelong persistence. Given the importance of peanuts in several sectors, and taking into consideration the criticality of their high allergic potential, strategies aiming at mitigating their allergenicity are urgently needed. In this regard, most of the processing methods used to treat peanuts are categorized as either thermal or thermomechanical techniques. The purpose of this review is to provide the reader with an updated outlook of the peanut’s allergens, their mechanisms of action, the processing methods as applied to whole peanuts, as well as a critical insight on their impact on the allergenicity. The methods discussed include boiling, roasting/baking, microwaving, ultrasonication, frying, and high-pressure steaming/autoclaving. Their effectiveness in alleviating the allergenicity, and their capacity in preserving the structural integrity of the treated peanuts, were thoroughly explored. Research data on this matter may open further perspectives for future relevant investigation ultimately aiming at producing hypoallergenic peanuts.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Relevance of sensitization to legumes in peanut-allergic children

BACKGROUND

Legume consumption has increased during the two past decades. In France, legumes are responsible for 14.6% of food-related anaphylaxis in children, with peanut as the main allergen (77.5%). Few studies have demonstrated cross-reactivities between peanut and other legumes. The aim of this study was to determine prevalence and relevance of sensitization to legumes in peanut-allergic children.

METHODS

All children, aged of 1-17 years, admitted to the Pediatric Allergy Department of the University Hospital of Nancy between January 1, 2017 and February 29, 2020 with a confirmed peanut allergy (PA) and a documented consumption or sensitization to at least one other legume were included. Data were retrospectively collected regarding history of consumption, skin prick tests, specific immunoglobulin E (IgE), prior allergic reactions, and oral food challenges for each legume.

RESULTS

Among the 195 included children with PA, 122 were sensitized to at least one other legume (63.9%). Main sensitizations were for fenugreek (N = 61, 66.3%), lentil (N = 38, 42.2%), soy (N = 61, 39.9%), and lupine (N = 63, 34.2%). Among the 122 sensitized children, allergy to at least one legume was confirmed for 34 children (27.9%), including six children who had multiple legume allergies (4.9%). Lentil, lupine, and pea were the main responsible allergens. Half of allergic reactions to legumes other than peanut were severe.

CONCLUSION

The high prevalence of legume sensitization and the frequent severe reactions reported in children with PA highlight that tolerated legume consumption should be explored for each legume in the case of PA, and sensitization should be investigated if not.

A practical focus on legume oral immunotherapy

Legumes other than peanut are an important source of protein and consist of a wide variety of species, such as soy, peas, chickpeas, lentils, and lupin. Due to their health benefits and the rising popularity of veganism, legume consumption has increased. Legume allergy, cross-sensitization, and cross-reactivity between different species have been reported in the literature and are increasingly recognized. Unlike peanut, oral immunotherapy (OIT) for nonpeanut legumes has not been well studied and published protocols are lacking. Future studies are needed to provide real-world data on the safety and effectiveness of nonpeanut legume OIT, and whether desensitization to one legume leads to desensitization to other legumes in patients with multiple legume allergy. Nevertheless, due to the abundance of clinical trial and real-world data for peanut OIT, it is reasonable to use protocols that substitute peanut protein with other legume protein when desensitizing individuals with nonpeanut legume allergy. Clinicians who are starting to offer legume OIT in their practices may consider starting with preschoolers, an age group for whom real-world data has shown the greatest safety and effectiveness.

Recent advances in the management of nut allergy

Peanut/tree nut allergy is common and has been associated with particularly severe reactions. Epidemiological data have shown that the prevalence ranges between 0.05% and 4.9% for tree nut and between 0.5% and 3% for peanut. These large variations can be explained by differences in the age of included patients and the geographical region. In addition, the food consumption modality (ie, raw versus roasted) plays a major role, as heat treatment has the capacity to modify the allergenicity of nuts and legumes. Nut allergies tend to persist into adulthood and consequently have a high impact on quality of life.

Recently, it has been demonstrated that a significant proportion of nut allergic patients are able to tolerate other nuts. As opposed to the avoidance of all nuts, this approach is currently proposed in several tertiary allergy centers. However, diagnosis of nut allergy is particularly difficult due to co-sensitization leading to high rate of false positive skin prick tests and/or specific IgE to whole allergen extracts. The use of component resolved diagnosis leads to major improvement of diagnosis, particularly to distinguish between primary and secondary nut allergies. The basophil activation test has been suggested to be useful but is still used mainly as a research tool. Thus, diagnosis remains mainly based on the oral food challenge, which is considered as the gold standard.

Regarding treatment, avoidance remains the cornerstone of management of nut allergy. Oral immunotherapy is increasingly proposed as an alternative management strategy.

Clinical Relevance of Cross-Reactivity in Food Allergy

The diagnosis and management of food allergy is complicated by an abundance of homologous, cross-reactive proteins in edible foods and aeroallergens. This results in patients having allergic sensitization (positive tests) to many biologically related foods. However, many are sensitized to foods without exhibiting clinical reactivity. Although molecular diagnostics have improved our ability to identify clinically relevant cross-reactivity, the optimal approach to patients requires an understanding of the epidemiology of clinically relevant cross-reactivity, as well as the food-specific (degree of homology, protein stability, abundance) and patient-specific factors (immune response, augmentation factors) that determine clinical relevance. Examples of food families with high rates of cross-reactivity include mammalian milks, eggs, fish, and shellfish. Low rates are noted for grains (wheat, barley, rye), and rates of cross-reactivity are variable for most other foods. This review discusses clinically relevant cross-reactivity related to the aforementioned food groups as well as seeds, legumes (including peanut, soy, chickpea, lentil, and others), tree nuts, meats, fruits and vegetables (including the lipid transfer protein syndrome), and latex. The complicating factor of addressing co-allergy, for example, the risks of allergy to both peanut and tree nuts among atopic patients, is also discussed. Considerations for an approach to individual patient care are highlighted.

Nutritional management of food allergies

Food allergy is a significant public health concern, with a rising prevalence. Elimination diets remain the cornerstone of food allergy management, and they are not without nutritional risk. Children who avoid nutritionally important foods, such as milk or multiple foods allergens, may be at greater risk. Even adults with food allergies may encounter challenges to meet current recommended dietary guidelines for health and reduced risk of chronic disease. The type of food allergy disorder will also impact nutritional risk. A food allergy affects food choices, nutritional intake, and health; therefore, guidance to provide nutritionally appropriate substitutes within the context of the elimination diet is invaluable.

IgE cross-reactivity measurement of cashew nut, hazelnut and peanut using a novel IMMULITE inhibition method

Background Tree nut-allergic individuals are often sensitised towards multiple nuts and seeds. The underlying cause behind a multi-sensitisation for cashew nut, hazelnut, peanut and birch pollen is not always clear. We investigated whether immunoglobulin E antibody (IgE) cross-reactivity between cashew nut, hazelnut and peanut proteins exists in children who are multi-allergic to these foods using a novel IMMULITE®-based inhibition methodology, and investigated which allergens might be responsible. In addition, we explored if an allergy to birch pollen might play a role in this co-sensitisation for cashew nut, hazelnut and peanut. Methods Serum of five children with a confirmed cashew nut allergy and suffering from allergic symptoms after eating peanut and hazelnut were subjected to inhibition immunoassays using the IMMULITE® 2000 XPi. Serum-specific IgE (sIgE) to seed storage allergens and pathogenesis-related protein 10 (PR10) allergens were determined and used for molecular multicomponent allergen correlation analyses with observed clinical symptoms and obtained inhibition data. Results IgE cross-reactivity was observed in all patients. Hazelnut extract was a strong inhibitor of cashew nut sIgE (46.8%), while cashew nut extract was less able to inhibit hazelnut extract (22.8%). Peanut extract showed the least inhibition potency. Moreover, there are strong indications that a birch pollen sensitisation to Bet v 1 might play a role in the observed symptoms provoked upon ingestion of cashew nut and hazelnut. Conclusions By applying an adjusted working protocol, the IMMULITE® technology can be used to perform inhibition assays to determine the risk of sIgE cross-reactivity between very different food components.

Immunoglobulin E-Binding Pattern of Canadian Peanut Allergic Children and Cross-Reactivity with Almond, Hazelnut and Pistachio

Peanut allergic individuals can be both co-sensitized and co-allergic to peanut and tree nuts. At the moment, standard diagnostic approaches do not always allow differentiation between clinically relevant sensitization and nonsignificant cross-reactions, and the responsibility of each allergen remains unclear. The objective of this study was therefore to determine a peanut sensitization profile in a cohort of Canadian peanut allergic children and assess the immunoglobulin E (IgE) molecular cross-reactivity between peanut, almond, hazelnut and pistachio. The specific IgE (sIgE) levels of each patient serum were determined by ImmunoCAP, indirect ELISA and immunoblot to examine their sIgE-binding levels and profiles to peanut proteins. Reciprocal inhibition ELISA and immunoblotting were used to study sIgE cross-reactions between peanut and the selected tree nuts using an adjusted and representative serum pool of the nine allergic patients. The results showed that the prepared peanut and tree nut protein extracts allowed for the detection of the majority of peanut and selected tree nut known allergens. The reciprocal inhibition ELISA experiments showed limited sIgE cross-reactivities between peanut and the studied tree nuts, with peanut being most likely the sensitizing allergen and tree nuts the cross-reactive ones. In the case of hazelnut and pistachio, a coexisting primary sensitization to hazelnut and pistachio was also demonstrated in the serum pool. Reciprocal inhibition immunoblotting further revealed that storage proteins (2S albumin, 7S vicilin and 11S legumin) could possibly account for the observed IgE-cross-reactions between peanut and the studied tree nuts in this cohort of allergic individuals. It also demonstrated the importance of conformational epitopes in the exhibited cross-reactions.

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.

Immunoreactivity of Lupine and Soybean Allergens in Foods as Affected by Thermal Processing

Lupine and soybean are important technological aids for the food industry. However, they are also capable of inducing severe allergic reactions in food-sensitized/allergic individuals. In this context, this work intended to study the combined effects of thermal processing and food matrix on the immunoreactivity of lupine and soybean proteins used as ingredients in bakery and meat products, respectively. For this purpose, the effects of baking, mild oven cooking, and autoclaving on the protein profiles were evaluated, using model mixtures simulating the production of lupine-containing breads and soybean-containing cooked hams/sausages, by native- and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and immunoblotting using specific antibodies. The results showed that lupine gamma-conglutin immunoreactivity was slightly decreased in wheat flour mixtures compared to rice, but it was more pronounced in baked products. In meat mixtures, substantial protein fragmentation was noted after autoclaving, with decreased immunoreactivity of soybean trypsin inhibitor. The analysis of 22 commercial products enabled the identification of lupine gamma-conglutin in four bakery samples and soybean trypsin-inhibitor in five sausages, and further differentiated autoclaved from other milder thermally treated products. Generally, the immunoreactivity of target proteins was reduced by all the tested thermal treatments, though at a higher extent after autoclaving, being slightly altered by the food matrix.