Markers of tolerance development to food allergens

Detection of egg white allergy in children by specific IgE microarray chemiluminescence immunoassay

BACKGROUND

Allergen testing has emerged as a pivotal component in prevention and treatment strategies for allergic diseases among children and the utilization of specific IgE (sIgE) through a fully automated chemiluminescent microarray immunoassay (CLMIA) has emerged as a promising trend in the simultaneous detection of multiple allergenic components of children.

METHODS

The accuracy and reliability of CLMIA were verified using children's serum samples that concentrated on allergens. the allergens. The clinical diagnostic practicability of CLMIA was assessed through comprehensive evaluations including measurements of the limit of detection (LOD), intra-batch, and inter-batch precision, linearity analysis, the cross-contamination rate, and the concordance rate with the Phadia system.

RESULTS

After the optimization process of CLMIA, the LODs for allergens were calculated to be below 0.01 kU/L, demonstrating the high sensitivity of CLMIA. All components exhibited good linearity within the range of 0.1-100.0 kU/L and the coefficient of determinations (R2 > 0.99). The data of intra-batch precision (<10 %) and inter-batch data (<15 %) illustrated the high reproducibility of CLMIA. The cross-contamination rates for allergens (<0.5 %) showed the high accuracy of CLMIA without interfering. The positive concordance rate between CLMIA and the Phadia system exceeds 90 % with a good negative concordance rate (>85 %) and the Kappa coefficients (>0.8), suggesting the close alignment of CLMIA and the Phadia system and showing the satisfactory clinical potential of CLMIA in children's allergy disease.

CONCLUSIONS

The application of CLMIA has been promising in allergen testing, especially for detecting multiple allergenic components in children.

Predicting the Outcome of Pediatric Oral Food Challenges for Determining Tolerance Development

PURPOSE

Despite the risk of anaphylaxis, oral food challenges (OFCs) are performed clinically for various indications, particularly to confirm tolerance development. This study aimed to assess OFCs by relevant indications and build an outcome prediction model to help determine when to perform OFCs in children who are likely to have developed immune tolerance.

METHODS

In total, 432 pediatric OFCs were retrospectively analyzed according to indications. Clinical characteristics, serum total immunoglobulin (Ig) E, blood eosinophils, and specific IgE and IgG4 levels for food allergens were noted and compared. Machine learning was utilized to select the most important variables in determining the passage of the OFCs, and prediction models were constructed using the selected variables.

RESULTS

OFCs were most commonly performed to confirm tolerance development (number, %; 267, 61.8%). The most common food allergens tested were egg (191, 44.2%) and milk (135, 31.3%). Children who passed the egg challenges for confirming tolerance acquisition had significantly lower egg white-specific IgE level (P = 0.008). Similarly, those who passed milk challenges had significantly lower cow's milk-specific IgE (P = 0.002) and casein-specific IgE levels (P = 0.005). We developed a nomogram to predict the outcome of OFCs to determine the tolerance acquisition with the selected variables; lower food-specific IgE, higher total IgE, and younger age indicated a higher probability of passage. The area under the curve (95% confidence interval) was 0.623 (0.503-0.743) for egg and 0.734 (0.628-0.840) for milk.

CONCLUSIONS

Serum total IgE and food-specific IgE combined with age showed trends toward passing OFCs for confirming tolerance development. The constructed model may be used by clinicians as a practical guide for minimizing the risks of OFCs and a timely reintroduction for children with food allergies.

Immune signatures predicting the clinical outcome of peanut oral immunotherapy: where we stand

Peanut allergy is a growing health concern that can cause mild to severe anaphylaxis as well as reduced quality of life in patients and their families. Oral immunotherapy is an important therapeutic intervention that aims to reshape the immune system toward a higher threshold dose reactivity and sustained unresponsiveness in some patients. From an immunological point of view, young patients, especially those under 3 years old, seem to have the best chance for therapy success. To date, surrogate markers for therapy duration and response are evasive. We provide a comprehensive overview of the current literature state regarding immune signatures evolving over the course of oral immunotherapy as well as baseline immune conditions prior to the initiation of treatment. Although research comparing clinical and immune traits in the first years of life vs. later stages across different age groups is limited, promising insights are available on immunological endotypes among peanut-allergic patients. The available data call for continued research to fill in gaps in knowledge, possibly in an integrated manner, to design novel precision health approaches for advanced therapeutic interventions in peanut allergy.

Biomarkers associated with persistence and severity of IgE-mediated food allergies: a systematic review

OBJECTIVE

The prevalence of food allergies (FA) has increased worldwide over the last few decades. Milk, eggs, and peanuts are among the most common allergens and can cause anaphylaxis. Therefore, we aimed to identify biomarkers that could predict the persistence and/or severity of IgE-mediated allergies to milk, eggs, and peanuts via a systematic review.

METHODS

This systematic review proceeded according to a protocol registered in the International Prospective Register of Systematic Reviews. Two independent authors extracted studies of interest from PubMed, SciELO, EMBASE, Scopus, and Ebsco databases and assessed their quality using the Newcastle-Ottawa Scale.

RESULTS

We selected 14 articles describing 1,398 patients. Among eight identified biomarkers, total IgE, specific IgE (sIgE), and IgG4 were the most often cited biomarkers of persistent allergies to milk, eggs, and peanuts. Skin prick tests, endpoint tests, and sIgE cutoff levels may predict positive responses to challenges with these foods. The basophil activation test is a biomarker for the severity and/or threshold of allergic reactions to milk and peanuts.

CONCLUSION

Only a few publications identified possible prognostic indicators of the persistence or severity of FA and outcomes of oral food challenges, indicating that more accessible biomarkers are needed to determine the likelihood of having a severe food allergic reaction.

Patient-important outcomes in clinical trials of atopic diseases and asthma in the last decade: A systematic review

Background

Randomized Clinical Trials (RCTs) are important tools to establish the effects of a given intervention. Investigators should focus on outcomes that patients perceive: patient-important outcomes (PIOs), clinical endpoints that patients value directly and reflect how they feel, function, or survive. However, it is easier to consider surrogated outcomes to reduce costs and achieve better-looking results. The problem with these outcomes is that they indirectly measure PIOs, which might not correlate linearly or translate reliably into a positive PIO.

Methods

We systematically searched MEDLINE for atopic disease RCTs rated among the top 10 allergic diseases and general internal medicine journals from the last 10 years. Two independent reviewers worked in duplicate and independently to collect data from all eligible articles. We gathered information regarding the type of study, title, author information, journal, intervention type, atopic disease, and primary and secondary outcomes. We assessed the outcomes investigators used in RCTs of atopic diseases and asthma.

Results

This quantitative analysis included n = 135 randomized clinical trials. The most studied atopic disease during the period selected was asthma (n = 69), followed by allergic rhinitis (n = 51). When divided by atopic disease, primary outcomes in RCTs valuing allergic rhinitis had the most significant proportion of PIOs (76.7), asthma surrogated outcomes (38), and asthma/allergic rhinitis laboratory outcomes (42.9). PIOs in allergic rhinitis trials had the most significant proportion of PIOs favoring the intervention (81.4), asthma had the greatest proportion of surrogated outcomes (33.3), and asthma/allergic rhinitis laboratory outcomes (40). When divided by atopic disease, trials studying atopic dermatitis and urticaria had the same proportion of PIOs (64.7) as their secondary outcomes. Asthma had the highest (37.5) surrogate outcomes. Journals of general/internal medicine had a greater proportion of PIOs, and a post hoc analysis showed a significant difference in the proportion and secondary outcomes that favored the intervention between PIOs and laboratory outcomes.

Conclusion

Approximately 7.5 out of 10 primary outcomes in RCTs published in general/internal medicine are PIOs compared to 5 out of 10 primary outcomes in atopic disease journals. Investigators should focus on selecting patient-important outcomes in their clinical trials to establish clinical guidelines with better-quality recommendations that impact patients' life and values.

Registration

International Prospective Register of Systematic Reviews (PROSPERO, NIHR) ID: CRD42021259256.

High prevalence of IgE sensitization to inactivated influenza vaccines, yet robust IgG4 responses, in a healthy pediatric population

BACKGROUND

Anaphylaxis following influenza vaccination is a rare but serious problem. The underlying immune responses are not well understood. This study elucidated the IgE and IgG antibody responses in healthy children and adolescents following inactivated influenza vaccines (IIVs).

METHODS

The efficacy and safety of quadrivalent IIV (QIV) and trivalent IIV (TIV) were compared in healthy subjects aged 0-18 years. Serum IIV-specific IgE, IgG, and IgG4 levels (sIgE, sIgG, and sIgG4) were measured with ImmunoCAP. Hemagglutination inhibition (HI) assay was performed for each influenza virus subtype. Sera from earlier patients who developed anaphylaxis to different IIVs were similarly tested.

RESULTS

A total of 393 subjects were enrolled: 96 were 6 months-2 years old, 100 were 3-5 years old, 100 were 6-12 years old, and 97 were 13-18 years old. No anaphylaxis was observed. Generally, QIV and TIV induced similar antibody responses. IIV-sIgE levels rose significantly after vaccination in the 6 months-2 years old and 3-5 years old groups, did not change in the 6-12 years old group, and decreased in the 13-18 years old group. In contrast, the IIV-sIgG4/sIgE ratio increased significantly after vaccination in all age groups. Sensitized subjects had significantly higher HI titers and IIV-sIgG levels in the youngest age group and higher IIV-sIgG4 levels in all age groups compared with the non-sensitized. The IIV-sIgG4/sIgE ratio in five patients with anaphylaxis was significantly lower than in age-matched healthy subjects.

CONCLUSION

IIVs induce IgE sensitization in healthy children but also robust IgG4 responses that may protect them from anaphylaxis.

Alternatives to Cow’s Milk-Based Infant Formulas in the Prevention and Management of Cow’s Milk Allergy

Cow’s milk-based infant formulas are the most common substitute to mother’s milk in infancy when breastfeeding is impossible or insufficient, as cow’s milk is a globally available source of mammalian proteins with high nutritional value. However, cow’s milk allergy (CMA) is the most prevalent type of food allergy among infants, affecting up to 3.8% of small children. Hypoallergenic infant formulas based on hydrolysed cow’s milk proteins are commercially available for the management of CMA. Yet, there is a growing demand for more options for infant feeding, both in general but especially for the prevention and management of CMA. Milk from other mammalian sources than the cow, such as goat, sheep, camel, donkey, and horse, has received some attention in the last decade due to the different protein composition profile and protein amino acid sequences, resulting in a potentially low cross-reactivity with cow’s milk proteins. Recently, proteins from plant sources, such as potato, lentil, chickpeas, quinoa, in addition to soy and rice, have gained increased interest due to their climate friendly and vegan status as well as potential lower allergenicity. In this review, we provide an overview of current and potential future infant formulas and their relevance in CMA prevention and management.

Subjects develop tolerance to Pru p 3 but respiratory allergy to Pru p 9: A large study group from a peach exposed population

Peach tree allergens are present in fruit, pollen, branches, and leaves, and can induce systemic, respiratory, cutaneous, and gastrointestinal symptoms. We studied the capacity of peach fruit/Pru p 1, Pru p 3, Pru p 4, Pru p 7 and peach pollen/Pru p 9 for inducing symptoms following oral or respiratory exposure in a large group of subjects. We included 716 adults (aged 21 to 83 y.o.) exposed to peach tree pollen and fruit intake in the study population. Participants completed a questionnaire and were skin tested with a panel of inhalant and food allergens, including peach tree pollen, Pru p 9 and peach fruit skin extract. Immunoglobulin E antibodies (SIgE) to Pru p 1, Pru p 3, Pru p 4 and Pru p 7 were quantified. Sensitised subjects underwent oral food challenge with peach fruit and nasal provocation test with peach tree pollen and Pru p 9. The prevalence of sensitisation to peach fruit was 5% and most of these had SIgE to Pru p 3, with a very low proportion to Pru p 4 SIgE and no SIgE to Pru p 1 and Pru p 7. In only 1.8%, anaphylaxis was the clinical entity induced. Cases with positive skin tests to peach and SIgE to Pru p 3 presented a good tolerance after oral challenge with peach fruit. The prevalence of skin sensitisation to peach tree pollen was 22%, with almost half recognising Pru p 9. This induced respiratory symptoms in those evaluated by nasal provocation. In a large population group exposed to peach fruit and peach tree pollen, most individuals were tolerant, even in those with SIgE to Pru p 3. A positive response to Pru p 9 was associated with respiratory allergy.

Induction of food tolerance is dependent on intestinal inflammatory state

Food allergies are usually managed by food avoidance. Hidden allergens in food, due to cross-contamination and/or allergenic additives added during production, place an important concern in today's increasing food allergy cases worldwide. Previous studies showed that the introduction of unacquainted food components, in an inflamed intestine, results in sensitization to this food. Thus, our aim was to evaluate the kinetics of multiple food allergy induction. Adult male C57BL/6 mice were divided into five groups, four of which were submitted to an intestinal inflammation induction protocol to peanuts. Egg white (OVA) diluted 1:5 v/v in distilled water was instilled by gavage 6h-before (PRIOR), concomitant (AT) and 6h-after (DURING) the onset of the peanut challenge diet. Positive control (POS CONT) and NEG CONT received saline per gavage. Finally, animals were challenged with subcutaneous injections of OVA. Results showed no changes in diet intake were observed. Anti-OVA polyisotypic IgG antibody titers significantly increased in AT. Flow cytometry revealed significant decrease in CD4⁺CD25⁺Foxp3⁺ and significant increase in TCD8⁺ in AT. Histomorphometrically, AT and DURING were classified as Infiltrative and Partial Destruction stages. PRIOR was classified as Infiltrative, while POS CONT was classified as Partial Destruction. NEG CONT was classified as Normal. Together, our results confirm that the introduction of unfamiliar food only a few hours before the initiation of a gut inflammation process is able to induce oral tolerance, however the introduction of a dietary protein concomitant to the onset or during an ongoing gut inflammation may induce multiple allergies.

Biomarkers of diagnosis and resolution of food allergy

Food allergy is increasing in prevalence, affecting up to 10% of children in developed countries. Food allergy can significantly affect the quality of life and well-being of patients and their families; therefore, an accurate diagnosis is of extreme importance. Some food allergies can spontaneously resolve in 50%-60% of cow's milk and egg-allergic, 20% of peanut-allergic and 9% of tree nut-allergic children by school age. For that reason, food-allergic status should be monitored over time to determine when to reintroduce the food back into the child's diet. The gold-standard to confirm the diagnosis and the resolution of food allergy is an oral food challenge; however, this involves the risk of causing an acute-allergic reaction and requires clinical experience and resources to treat allergic reactions of any degree of severity. In the clinical setting, biomarkers have been used and validated to enable an accurate diagnosis when combined with the clinical history, deferring the oral food challenge, whenever possible. In this review, we cover the tools available to support the diagnosis of food allergies and to predict food allergy resolution over time. We review the latest evidence on different testing modalities and how effective they are in guiding clinical decision making in practice. We also evaluate predictive test cut-offs for the more common food allergens to try and provide guidance on when challenges might be most successful in determining oral tolerance in children.

Biomarkers for diagnosis and prediction of therapy responses in allergic diseases and asthma

Modern health care requires a proactive and individualized response to diseases, combining precision diagnosis and personalized treatment. Accordingly, the approach to patients with allergic diseases encompasses novel developments in the area of personalized medicine, disease phenotyping and endotyping, and the development and application of reliable biomarkers. A detailed clinical history and physical examination followed by the detection of IgE immunoreactivity against specific allergens still represents the state of the art. However, nowadays, further emphasis focuses on the optimization of diagnostic and therapeutic standards and a large number of studies have been investigating the biomarkers of allergic diseases, including asthma, atopic dermatitis, allergic rhinitis, food allergy, urticaria and anaphylaxis. Various biomarkers have been developed by omics technologies, some of which lead to a better classification of distinct phenotypes or endotypes. The introduction of biologicals to clinical practice increases the need for biomarkers for patient selection, prediction of outcomes and monitoring, to allow for an adequate choice of the duration of these costly and long‐lasting therapies. Escalating healthcare costs together with questions about the efficacy of the current management of allergic diseases require further development of a biomarker‐driven approach. Here, we review biomarkers in diagnosis and treatment of asthma, atopic dermatitis, allergic rhinitis, viral infections, chronic rhinosinusitis, food allergy, drug hypersensitivity and allergen immunotherapy with a special emphasis on specific IgE, the microbiome and the epithelial barrier. In addition, EAACI guidelines on biologicals are discussed within the perspective of biomarkers.

Food allergens: Classification, molecular properties, characterization, and detection in food sources

Food allergy is a large and growing public health problem in many areas of the world. The prevalence of food allergy has increased in the last decades in a very significant way in many world regions, particularly in developed countries. In that respect, the research field of food allergy has experienced an extensive growth and very relevant progress has been made in recent years regarding the characterization of food allergens, the study of their immunological properties, and their detection in food sources. Furthermore, food labeling policies have also been improved decidedly in recent years. For that immense progress made, it is about time to review the latest progress in the field of food allergy. In this review, we intend to carry out an extensive and profound overview regarding the latest scientific advances and knowledge in the field of food allergen detection, characterization, and in the study of the effects of food processing on the physico-chemical properties of food allergens. The advances in food labeling policies, and methodologies for the characterization of food allergens are also thoroughly reviewed in the present overview.

Recent developments and highlights in food allergy

The achievement of long-lasting, safe treatments for food allergy is dependent on the understanding of the immunological basis of food allergy. Accurate diagnosis is essential for management. In recent years, data from oral food challenges have revealed that routine allergy testing is poor at predicting clinical allergy for tree nuts, almonds in particular. More advanced antigen-based tests including component-resolved diagnostics and epitope reactivity may lead to more accurate diagnosis and selection of therapeutic intervention. Additional diagnostic accuracy may come from cellular tests such as the basophil activation test or mast cell approaches. In the context of clinical trials, cellular tests have revealed specific T-cell and B-cell populations that are more abundant in food-allergic individuals with distinct mechanistic features. Awareness of clinical markers, such as the ability to eat baked forms of milk and egg, continues to inform the understanding of natural tolerance development. Mouse models have allowed for investigation into multiple mechanisms of food allergy including modification of epithelial metabolism, and the induction of regulatory cell subsets and the microbiome. Increasing numbers of children who underwent food immunotherapy enlarged the body of evidence on mechanisms and predictors of treatment success. Experimental immunological markers in conjunction with clinical determinants such as lower age and lower initial specific IgE appear to be of benefit. More research on the optimal dose, preparation, and route of application integrating a high-level safety and efficacy is demanded. Alternatively, biologics blocking TSLP, IL-33, IL-4 and IL-13, or IgE may help to achieve that.

Retinoic acid prevents immunogenicity of milk lipocalin Bos d 5 through binding to its immunodominant T-cell epitope

The major cow’s milk allergen Bos d 5 belongs to the lipocalin protein family, with an intramolecular pocket for hydrophobic ligands. We investigated whether Bos d 5 when loaded with the active vitamin A metabolite retinoic acid (RA), would elicit differential immune responses compared to the unloaded state. By in silico docking an affinity energy of −7.8 kcal/mol was calculated for RA into Bos d 5. Loading of RA to Bos d 5 could be achieved in vitro, as demonstrated by ANS displacement assay, but had no effect on serum IgE binding in tolerant or challenge-positive milk allergic children. Bioinformatic analysis revealed that RA binds to the immunodominant T-cell epitope region of Bos d 5. In accordance, Bos d 5 significantly suppressed the CD3+ CD4+ cell numbers, proliferative response and IL-10, IL-13 and IFN-γ secretion from stimulated human PBMCs only when complexed with RA. This phenomenon was neither associated with apoptosis of T-cells nor with the activation of Foxp3+ T-cells, but correlated likely with enhanced stability to lysosomal digestion due to a predicted overlap of Cathepsin S cleavage sites with the RA binding site. Taken together, proper loading of Bos d 5 with RA may suppress its immunogenicity and prevent its allergenicity.

Dietary Intervention with β-Lactoglobulin-Derived Peptides and a Specific Mixture of Fructo-Oligosaccharides and Bifidobacterium breve M-16V Facilitates the Prevention of Whey-Induced Allergy in Mice by Supporting a Tolerance-Prone Immune Environment

Cow's milk allergy (CMA) prevails in infants and brings increased risk of developing other allergic diseases. Oral administration of specific β-lactoglobulin (BLG)-derived peptides (PepMix) and a specific blend of short- and long-chain fructo-oligosaccharides and Bifidobacterium breve M-16V (FF/Bb) was found to partially prevent CMA development in mice. In this study, we aimed to expand the knowledge on the preventive potential and the underlying mechanisms of this approach. Three-week-old female C3H/HeOuJ mice were orally exposed to PepMix±FF/Bb prior to a 5-week oral sensitization with whole whey and cholera toxin as an adjuvant. The acute allergic skin response was determined after an intradermal challenge with whole whey protein. Following an oral challenge with whey, regulatory T cells (T_regs) in the small intestine lamina propria (SI-LP) and mRNA expression of immune markers in the Peyer's patches (PP) were investigated. The early impact of PepMix and FF/Bb interventions on the immune system during the oral tolerance (OT) induction phase was investigated after the last OT administration. Pre-exposing mice to PepMix+FF/Bb partially prevented the acute allergic skin response compared to PBS and increased T_regs and activated T cells in the SI-LP compared to sham-sensitized mice. It also increased the mRNA expression of Tbet over GATA3 in the PP of whey-sensitized mice. Directly upon the 6-day OT phase, FF/Bb intervention enhanced cecal content levels of propionic and butyric acid in PepMix-fed mice and the former was positively correlated with Foxp3⁺ cell numbers in the colon. In the PP of PepMix+FF/Bb-exposed mice, IL-22 mRNA expression increased and IL-10 followed the same tendency, while the Foxp3 expression was increased over GATA3 and RorγT. In the colon, the Tbet mRNA expression increased over GATA3, while IL-22 decreased. In addition, the Foxp3⁺/GATA3⁺ and regulatory/effector T cell ratios in the mesenteric lymph nodes and the CD11b⁺/CD11b^- conventional dendritic cells ratio in the SI-LP were increased. In conclusion, the FF/Bb diet facilitates the capacity of the specific BLG-peptides to partially prevent the allergic response after sensitization to whole whey protein, possibly by creating a tolerance-prone environment during the OT phase. Such a dietary intervention might contribute to tailoring successful strategies for CMA prevention.

Novel approaches and perspectives in allergen immunotherapy

In this review, we report on relevant current topics in allergen immunotherapy (AIT) which were broadly discussed during the first Aarhus Immunotherapy Symposium (Aarhus, Denmark) in December 2015 by leading clinicians, scientists and industry representatives in the field. The aim of this symposium was to highlight AIT-related aspects of public health, clinical efficacy evaluation, mechanisms, development of new biomarkers and an overview of novel therapeutic approaches. Allergy is a public health issue of high socioeconomic relevance, and development of evidence-based action plans to address allergy as a public health issue ought to be on national and regional agendas. The underlying mechanisms are in the focus of current research that lays the ground for innovative therapies. Standardization and harmonization of clinical endpoints in AIT trials as well as current knowledge about potential biomarkers have substantiated proof of effectiveness of this disease-modifying therapeutic option. Novel treatments such as peptide immunotherapy, intralymphatic immunotherapy and use of recombinant allergens herald a new age in which AIT may address treatment of allergy as a public health issue by reaching a large fraction of patients.

Therapeutic vaccines for allergic disease

Allergic diseases are highly prevalent worldwide and affect all age groups, contributing to a high personal and socioeconomic burden. Treatment with an “allergy vaccine” or allergen immunotherapy aims to provide long-lasting benefits by inducing unresponsiveness to the relevant antigen. The consequences of the therapy are considered disease modifying and range from dampening of the immediate immune responses to the reduction of secondary tissue remodeling. Furthermore, allergen immunotherapy interventions have a potential to slow or cease the development of additional allergic manifestations with a long-term overall effect on morbidity and quality of life. Here, we review proposed mechanisms underlying the therapeutic effects of immunotherapy for allergic diseases. Further, we discuss both standard and novel approaches and possible future directions in the development of allergen immunotherapy.