Risk assessment of clinical reactions to legumes in peanut-allergic children

Legume and sesame oral food challenge outcomes

Background

Legume and sesame are emerging food allergens. The utility of specific immunoglobulin E (sIgE) testing to predict clinical reactivity to these allergens is not well described.

Objective

To describe clinical outcomes and sIgE in sesame and legume oral food challenges (OFC).

Methods

We performed a retrospective review of 74 legume and sesame OFCs between 2007 and 2017 at the Ann and Robert H. Lurie Children's Hospital of Chicago. Clinical data, OFC outcome, and sIgE to legume and sesame were collected. Receiver operating characteristic curves and logistic regression models that predicted OFC outcome were generated.

Results

Twenty-eight patients (median age, 6.15 years) passed legume OFC (84.9%), and 25 patients (median age, 5.91 years) passed sesame OFC (61.0%). The median sIgE to legume was 1.41 kUA/L and, to sesame, was 2.34 kUA/L. In patients with failed legume OFC, 60.0% had cutaneous symptoms, 20.0% had gastrointestinal symptoms, and 20.0% had anaphylaxis. Of these reactions, 80.0% were controlled with antihistamine alone and 20.0% required epinephrine. In patients for whom sesame OFC failed, 50.0% had cutaneous symptoms, 12.5% had gastrointestinal symptoms, and 37.50% had anaphylaxis. Of these reactions, 6.3% required epinephrine, 31.3% were controlled with diphenhydramine alone, and 63.50% required additional epinephrine or prednisone.

Conclusion

Most OFCs to legumes were passed and reactions to failed legume OFCs were more likely to be nonsevere. Sesame OFC that failed was almost twice as likely compared with legume OFC that failed, and reactions to sesame OFC that failed were often more severe. Sesame sIgE did not correlate with OFC outcome.

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.

Inability to detect significant absorption of immunoreactive soya protein in healthy adults may be relevant to its weak allergenicity

Soya and peanut are botanically closely related and share cross-reacting antigens, but compared to soya, peanut allergy has a higher prevalence with more severe allergic reactions. Furthermore, the threshold dose for eliciting reactions is higher for soya. A difference in undigested protein absorption between the two foods, might explain this diversity.

In the current study the amount of soya protein absorbed after soya bean ingestion in healthy adults was estimated. Ten subjects ingested 100 grams of soya beans (40 grams of soya protein) and blood was drawn before and 1, 3 and 24 hours after administration. Serum was analysed by ELISA and histamine release (HR). In all serum samples the soya protein concentration was below quantification limit (1.6 ng/ml which corresponds to 4.8 μg or 0.12 parts per million absorbed soya protein.

We could not detect any significant absorption of soya protein. While we cannot totally exlude technical reasons, it may also reflect a true poor absorption in healthy adult volunteers. This could, in turn, be relevant to the apparently weak allergenicity of soy protein by comparison with peanut protein in allergic subjects.