In silico prediction of Ara h 2 T cell epitopes in peanut-allergic children

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.

Tolerogenic Nano-/Microparticle Vaccines for Immunotherapy

Autoimmune diseases, allergies, transplant rejections, generation of antidrug antibodies, and chronic inflammatory diseases have impacted a large group of people across the globe. Conventional treatments and therapies often use systemic or broad immunosuppression with serious efficacy and safety issues. Tolerogenic vaccines represent a concept that has been extended from their traditional immune-modulating function to induction of antigen-specific tolerance through the generation of regulatory T cells. Without impairing immune homeostasis, tolerogenic vaccines dampen inflammation and induce tolerogenic regulation. However, achieving the desired potency of tolerogenic vaccines as preventive and therapeutic modalities calls for precise manipulation of the immune microenvironment and control over the tolerogenic responses against the autoantigens, allergens, and/or alloantigens. Engineered nano-/microparticles possess desirable design features that can bolster targeted immune regulation and enhance the induction of antigen-specific tolerance. Thus, particle-based tolerogenic vaccines hold great promise in clinical translation for future treatment of aforementioned immune disorders. In this review, we highlight the main strategies to employ particles as exciting tolerogenic vaccines, with a focus on the particles' role in facilitating the induction of antigen-specific tolerance. We describe the particle design features that facilitate their usage and discuss the challenges and opportunities for designing next-generation particle-based tolerogenic vaccines with robust efficacy to promote antigen-specific tolerance for immunotherapy.

T-cell epitope discovery and single-cell technologies to advance food allergy research

There is good evidence for a role of T cells in food allergy, but there is a lack of mechanistic understanding and phenotypic markers of the specific T cells contributing to pathology. Recent technologic advancements have allowed for a new experimental paradigm where we can find and pull out rare antigen-specific T cells and characterize them at the single-cell level. However, studies in infectious disease and broader allergy have shown that these techniques benefit greatly from precisely defined T-cell epitopes. Food allergens have fewer epitopes currently available, but it is growing and promises to overcome this gap. With growing use of this experimental design, it will be important to unbiasedly map T-cell phenotypes across food allergy and look for commonalities and contrasts to other allergic and infectious diseases. Once a pathologic phenotype for T cells has been established, the frequencies of these cells can be monitored with simpler techniques that could be applied to the clinic and used in diagnosis, prediction of treatment responsiveness, and discovery of targets for new treatments.

Use of a Liver-targeting Nanoparticle Platform to Intervene in Peanut-induced anaphylaxis through delivery of an Ara h2 T-cell Epitope

To address the urgent need for safe food allergen immunotherapy, we have developed a liver-targeting nanoparticle platform, capable of intervening in allergic inflammation, mast cell release and anaphylaxis through the generation of regulatory T-cells (Treg). In this communication, we demonstrate the use of a poly (lactide-co-glycolide acid) (PLGA) nanoparticle platform for intervening in peanut anaphylaxis through the encapsulation and delivery of a dominant protein allergen, Ara h 2 and representative T-cell epitopes, to liver sinusoidal endothelial cells (LSECs). These cells have the capacity to act as natural tolerogenic antigen-presenting cells (APC), capable of Treg generation by T-cell epitope presentation by histocompatibility (MHC) type II complexes on the LSEC surface. This allowed us to address the hypothesis that the tolerogenic nanoparticles platform could be used as an effective, safe, and scalable intervention for suppressing anaphylaxis to crude peanut allergen extract. Following the analysis of purified Ara h 2 and representative MHC-II epitopes Treg generation in vivo, a study was carried out to compare the best-performing Ara h 2 T-cell epitope with a purified Ara h 2 allergen, a crude peanut protein extract (CPPE) and a control peptide in an oral sensitization model. Prophylactic as well as post-sensitization administration of the dominant encapsulated Ara h 2 T-cell epitope was more effective than the purified Ara h2 in eliminating anaphylactic manifestations, hypothermia, and mast cell protease release in a frequently used peanut anaphylaxis model. This was accompanied by decreased peanut-specific IgE blood levels and increased TGF-β release in the abdominal cavity. The duration of the prophylactic effect was sustained for two months. These results demonstrate that targeted delivery of carefully selected T-cell epitopes to natural tolerogenic liver APC could serve as an effective platform for the treatment of peanut allergen anaphylaxis.

Prediction and characterization of the T cell epitopes for the major soybean protein allergens using bioinformatics approaches

Protein allergens is a health risk for consumption of soybeans. To understand allerginicity mechanism, T cell epitopes of 7 soybean allergens were predicted and screened by abilities to induce cytokine interleukin (IL) 4. The relationships among amino acid composition, properties, allergenicity, and pepsin hydrolysis sites were analyzed. Among the 138 T cell epitopes identified, YIKDVFRVIPSEVLS, KDVFRVIPSEVLSNS, DVFRVIPSEVLSNSY of Gly m 6.0501 (P04347), and AKADALFKAIEAYLL, ADALFKAIEAYLLAH of Gly m 4.0101 (P26987) were the most possible epitope candidates. In T cell epitopes pattern, the frequencies of amino acids Q, D, E, P, and G decreased, while F, I, N, V, K, H, A, L, and S increased. Hydrophobic residues at positions p1 and p2 and positively charged residues in positions p13 might contribute to allergenicity. Most of epitopes could be hydrolyzed by pepsin into small polypeptides within 12 residues length, and the anti-digestive epitope regions contained I, V, S, N, and Q residues. T cell epitopes EEQRQQEGVIVELSK from Gly m 5.03 (P25974) showed resistance to pepsin hydrolysis and would cause a higher Th2 cell response. This research provides basis for the development of hypoallergenic soybean products in the soybean industry as well as for the immunotherapy design for protein allergy.

Memory Generation and Re-Activation in Food Allergy

Recent evidence has highlighted the critical role of memory cells in maintaining lifelong food allergies, thereby identifying these cells as therapeutic targets. IgG⁺ memory B cells replenish pools of IgE-secreting cells upon allergen exposure, which contract thereafter due to the short lifespan of tightly regulated IgE-expressing cells. Advances in the detection and highly dimensional analysis of allergen-specific B and T cells from allergic patients have provided insight on their phenotype and function. The newly identified Th2A and Tfh13 populations represent a leap in our understanding of allergen-specific T cell phenotypes, although how these populations contribute to IgE memory responses remains poorly understood. Within, we discuss the mechanisms by which memory B and T cells are activated, integrating knowledge from human systems and fundamental research. We then focus on memory reactivation, specifically, on the pathways of secondary IgE responses. Throughout, we identify areas of future research which will help identify immunotargets for a transformative therapy for food allergy.

T-Cell Epitope Immunotherapy in Mouse Models of Food Allergy

Food allergy has been rising in prevalence over the last two decades, affecting more than 10% of the world population. Current management of IgE-mediated food allergy relies on avoidance and rescue medications; research into treatments that are safer and providing guaranteed and durable curative effects is, therefore, essential. T-cell epitope-based immunotherapy holds the potential for modulating food allergic responses without IgE cross-linking. In this chapter, we describe the methods in evaluating the therapeutic capacities of immunodominant T-cell epitopes in animal models of food allergy. Moreover, we explain in detail the methods to measure the allergen-specific antibody levels, prepare single-cell suspension from spleen, and prepare small intestine for immunohistochemical analysis of eosinophils and Foxp3+ cells.

Development of a novel Ara h 2 hypoallergen with no IgE binding or anaphylactogenic activity

Background

To date, no safe allergen-specific immunotherapy for patients with peanut allergy is available. Previous trials were associated with severe side effects.

Objective

We sought to determine the relative importance of conformational and linear IgE-binding epitopes of the major peanut allergen Ara h 2 and to produce a hypoallergenic variant with abolished anaphylactogenic activity.

Methods

Wild-type Ara h 2 and a mutant lacking the loops containing linear IgE epitopes were produced in insect cells. Conformational IgE epitopes were removed by unfolding these proteins through reduction and alkylation. IgE binding was tested by means of ELISA with sera from 48 Ara h 2–sensitized patients with peanut allergy. Basophil activation and T-cell proliferation were tested with blood samples from selected patients. Anaphylactogenic potency was tested by using intraperitoneal challenge of mice sensitized intragastrically to peanut extract.

Results

Patients’ IgE recognized conformational and linear epitopes in a patient-specific manner. The unfolded mutant lacking both types of epitopes displayed significantly lower IgE binding (median ELISA OD, 0.03; interquartile range, 0.01-0.06) than natural Ara h 2 (median ELISA OD, 0.99; interquartile range, 0.90-1.03; P < .01). Basophil activation by unfolded mutant Ara h 2 was low (median area under the curve, 72 vs 138 for native wild-type Ara h 2; P < .05), but its ability to induce T-cell proliferation was retained. Unfolded mutants without conformational epitopes did not induce anaphylaxis in peanut-sensitized mice.

Conclusions

By removing conformational and linear IgE epitopes, a hypoallergenic Ara h 2 mutant with abolished IgE binding and anaphylactogenic potency but retained T-cell activation was generated.

Peanut-specific T cell responses in patients with different clinical reactivity

Whole extract or allergen-specific IgE testing has become increasingly popular in the diagnosis of peanut allergy. However, much less is known about T cell responses in peanut allergy and how it relates to different clinical phenotypes. CD4+ T cells play a major role in the pathophysiology of peanut allergy as well as tolerance induction during oral desensitization regimens. We set out to characterize and phenotype the T cell responses and their targets in peanut sensitized patients. Using PBMC from peanut-allergic and non-allergic patients, we mapped T cell epitopes for three major peanut allergens, Ara h 1, 2 and 3 (27 from Ara h 1, 4 from Ara h 2 and 43 from Ara h 3) associated with release of IFNγ (representative Th1 cytokine) and IL5 (representative Th2 cytokine). A pool containing 19 immunodominant peptides, selected to account for 60% of the total Ara h 1-3-specific T cell response in allergics, but only 20% in non-allergics, was shown to discriminate T cell responses in peanut-sensitized, symptomatic vs non-symptomatic individuals more effectively than peanut extract. This pool elicited positive T cell responses above a defined threshold in 12/15 sensitized, symptomatic patients, whereas in the sensitized but non-symptomatic cohort only, 4/14 reacted. The reactivity against this peptide pool in symptomatic patients was dominated by IL-10, IL-17 and to a lesser extend IL-5. For four distinct epitopes, HLA class II restrictions were determined, enabling production of tetrameric reagents. Tetramer staining in four donors (2 symptomatic, 2 non-symptomatic) revealed a trend for increased numbers of peanut epitope-specific T cells in symptomatic patients compared to non-symptomatic patients, which was associated with elevated CRTh2 expression whereas cells from non-symptomatic patients exhibited higher levels of Integrin β7 expression. Our results demonstrate differences in T cell response magnitude, epitope specificity and phenotype between symptomatic and non-symptomatic peanut-sensitized patients. In addition to IgE reactivity, analysis of peanut-specific T cells may be useful to improve our understanding of different clinical manifestations in peanut allergy.

Immunomodulating peptides for food allergy prevention and treatment

Among the most promising strategies currently assayed against IgE-mediated allergic diseases stands the possibility of using immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. This review focuses on the beneficial effects of food derived immunomodulating peptides on food allergy, which can be directly exerted in the intestinal tract or once being absorbed through the intestinal epithelial barrier to interact with immune cells. Food peptides influence intestinal homeostasis by maintaining and reinforcing barrier function or affecting intestinal cell-signalling to nearby immune cells and mucus secretion. In addition, they can stimulate cells of the innate and adaptive immune system while supressing inflammatory responses. Peptides represent an attractive alternative to whole allergens to enhance the safety and efficacy of immunotherapy treatments. The conclusions drawn from curative and preventive experiments in murine models are promising, although there is a need for more pre-clinical studies to further explore the immunomodulating strategy and its mechanisms and for a deeper knowledge of the peptide sequence and structural requirements that determine the immunoregulatory function.

T-Cell Proliferation Assay: Determination of Immunodominant T-Cell Epitopes of Food Allergens

Characterization of allergen-specific T cells is critical to understand their contribution to disease pathogenesis. The identification of immunodominant T-cell epitopes is crucial for development of T-cell-based vaccines. Peptide-specific T-cell proliferation studies are usually performed in a library of short synthetic peptides (15mer or 20mer) with 3 or 5 offset spanning the entire length of the allergen. T-cell peptide epitopes lack the primary and tertiary structure of the native protein to cross-link IgE, but retain the ability to stimulate T cells. The peptides sequences can also be obtained either by in silico approaches and in vitro binding assays. The efficacy of T-cell epitope-based peptide immunotherapy has been proven in certain allergies. The present methodology describes T-cell proliferation assays using whole blood sample from allergic subjects.

T-Cell Epitope Prediction

An epitope is a part of an immunogenic protein that can be recognized by the immune system. The peptides that can be recognized by the T-cell receptors after a particular antigen has been intracellularly processed, bound to at least one MHC molecule and expressed on the surface of the antigen presenting cell as a MHC-peptide complex, are called a T-cell epitope. Individuals who have at least one MHC molecule able to most avidly bind to allergenic amino acid sequences from an allergen, and at the same time have the appropriate T-cell clone that can recognize this MHC-peptide complex, are expected to be genetically prone to allergic reactions against that allergen. This possibility can be examined in silico by utilizing modern computational techniques that are based on sophisticated mathematics and statistics. The design principles of these techniques are different and therefore variations in their predictions are expected. The available software programs that have been developed on this basis are able to combine the increasing amount and complexity of the available experimental data that have been organized in immunoinformatics databases to predict potential allergen T-cell epitopes. All relevant T-cell epitope prediction methods can be accessed online as a freeware.

Molecular cloning, expression, IgE binding activities and in silico epitope prediction of Per a 9 allergens of the American cockroach

Per a 9 is a major allergen of the American cockroach (CR), which has been recognized as an important cause of imunoglobulin E-mediated type I hypersensitivity worldwide. However, it is not neasy to obtain a substantial quantity of this allergen for use in functional studies. In the present study, the Per a 9 gene was cloned and expressed in Escherichia coli (E. coli) systems. It was found that 13/16 (81.3%) of the sera from patients with allergies caused by the American CR reacted to Per a 9, as assessed by enzyme-linked immunosorbent assay, confirming that Per a 9 is a major allergen of CR. The induction of the expression of CD63 and CCR3 in passively sensitized basophils (from sera of patients with allergies caused by the American CR) by approximately 4.2-fold indicated that recombinant Per a 9 was functionally active. Three immunoinformatics tools, including the DNAStar Protean system, Bioinformatics Predicted Antigenic Peptides (BPAP) system and the BepiPred 1.0 server were used to predict the potential B cell epitopes, while Net-MHCIIpan-2.0 and NetMHCII-2.2 were used to predict the T cell epitopes of Per a 9. As a result, we predicted 11 peptides (23-28, 39-46, 58-64, 91-118, 131-136, 145-154, 159-165, 176-183, 290-299, 309-320 and 338-344) as potential B cell linear epitopes. In T cell prediction, the Per a 9 allergen was predicted to have 5 potential T cell epitope sequences, 119-127, 194-202, 210-218, 239-250 and 279-290. The findings of our study may prove to be useful in the development of peptide-based vaccines to combat CR-induced allergies.

Hypoallergenic hydrolysates of egg white proteins modulate allergen responses induced ex vivo on spleen cells from sensitized mice

This study describes the in vivo allergenicity of enzymatic hydrolysates of egg white proteins (ovalbumin, lysozyme and ovomucoid) and explores the possibility that they could modulate T cell cytokine responses to egg allergens ex vivo, using splenocytes from BALB/c mice sensitized to individual egg proteins or to their mixtures in different proportions. The hydrolysate of ovalbumin with pepsin could be regarded as a good candidate for peptide-based immunotherapy on the grounds of its reduced ability to trigger allergic symptoms in a passive cutaneous anaphylaxis assay and its potential to reduce Th2 responses (release of IL-4 and IL-5) induced by egg allergens in the spleen cell cultures, but also to enhance Th1 responses (release of TNF-α and IFN-γ). While it is possible to obtain chromatographic fractions containing peptides with different Th2-inhibiting or promoting properties, as judged by cytokine production, selective peptide enrichment did not lead to an increase in the immunomodulating efficiency as compared with the whole ovalbumin hydrolysate, possibly due to the presence in the latter of a combination of immunogenic peptides with synergistic or adjuvant actions.

What Characteristics Confer Proteins the Ability to Induce Allergic Responses? IgE Epitope Mapping and Comparison of the Structure of Soybean 2S Albumins and Ara h 2

Ara h 2, a peanut 2S albumin, is associated with severe allergic reactions, but a homologous protein, soybean 2S albumin, is not recognized as an important allergen. Structural difference between these proteins might explain this clinical discrepancy. Therefore, we mapped sequential epitopes and compared the structure of Ara h 2, Soy Al 1, and Soy Al 3 (Gly m 8) to confirm whether structural differences account for the discrepancy in clinical responses to these two proteins. Commercially synthesized peptides covering the full length of Ara h 2 and two soybean 2S albumins were analyzed by peptide microarray. Sera from 10 patients with peanut and soybean allergies and seven non-atopic controls were examined. The majority of epitopes in Ara h 2 identified by microarray are consistent with those identified previously. Several regions in the 2S albumins are weakly recognized by individual sera from different patients. A comparison of allergenic epitopes on peanut and soybean proteins suggests that loop-helix type secondary structures and some amino acids with a large side chain including lone electron pair, such as arginine, glutamine, and tyrosine, makes the peptides highly recognizable by the immune system. By utilizing the peptide microarray assay, we mapped IgE epitopes of Ara h 2 and two soybean 2S albumins. The use of peptide microarray mapping and analysis of the epitope characteristics may provide critical information to access the allergenicity of food proteins.

Regulation of Exacerbated Immune Responses in Human Peripheral Blood Cells by Hydrolysed Egg White Proteins

The anti-allergic potential of egg white protein hydrolysates (from ovalbumin, lysozyme and ovomucoid) was evaluated as their ability to hinder cytokine and IgE production by Th2-skewed human peripheral blood mononuclear cells (PBMCs), as well as the release of pro-inflammatory factors and generation of reactive oxygen species from Th1-stimulated peripheral blood leukocytes (PBLs). The binding to IgE of egg allergic patients was determined and the peptides present in the hydrolysates were identified. The hydrolysates with alcalase down-regulated the production of Th2-biased cytokines and the secretion of IgE to the culture media of Th2-skewed PBMCs, and they significantly neutralized oxidative stress in PBLs. The hydrolysates of ovalbumin and ovomucoid with pepsin helped to re-establish the Th1/Th2 balance in Th2-biased PBMCs, while they also inhibited the release of pro-inflammatory mediators and reduced oxidative stress in PBLs treated with inflammatory stimuli. The hydrolysates with alcalase, in addition to equilibrating Th2 differentiation, exhibited a low IgE-binding. Therefore, they would elicit mild allergic reactions while retaining T cell-stimulating abilities, which might correlate with an anti-allergic benefit.

Peanut T-cell epitope discovery: Ara h 1

BACKGROUND

Identification of potential T-cell epitopes in the peanut major allergens is essential for development of peptide-based immunotherapy. Traditional methods of T-cell epitope discovery use overlapping short peptides spanning the full length of the protein in T-cell proliferation assays. Because large proteins, such as Ara h 1, require a large number of peptides, this limits screening to a small number of allergic subject-derived T-cell lines.

OBJECTIVE

We sought to identify candidate peptides of Ara h 1 that display promiscuous binding to MHC class II and induce TH2 cytokine production by T cells.

METHODS

In silico MHC class II binding prediction was performed with NetMHCIIpan 2.0 (peptide length, 15; 1-mer offset) and the most abundant class II alleles in the North American population and with an in vitro MHC class II peptide reporter assay performed in parallel, which used synthetic 15-mer peptides offset by 5 mer spanning the protein. High-resolution MHC class II typing and a T-cell proliferation assay using preselected peptides were performed with PBMCs from 98 subjects with peanut allergy and 14 healthy control subjects. IL-4, IL-13, IL-5, IFN-γ, and TNF-α levels were measured in culture supernatants.

RESULTS

Thirty-six Ara h 1 peptides were identified by using in silico predictions and MHC class II binding assays. In combination with T-cell proliferation and cytokines secreted in T-cell assays, we have identified 4 vaccine candidate Ara h 1 peptides.

CONCLUSIONS

Preselection of peptides by using in silico and in vitro approaches in combination with conventional methods appears to be an effective strategy for identifying peanut T-cell peptide vaccine candidates.

Food Allergies: Novel Mechanisms and Therapeutic Perspectives

Childhood food allergy (FA) rates have rapidly increased with significant direct medical costs for the health care system and even larger costs for the families with a food-allergic child. The possible causes of food allergy become the target of intense scrutiny in recent years. Increasing evidence underline the importance in early life of gut microbiome in the development of allergic diseases. There are a range of factors in the modern environment that may be associated with changes to both the gut microbiome and risk of FA, such as mode of delivery, antibiotic exposure, infant feeding practices, farming environment, and country of origin. Knowledge of the relationship between early life gut microbiome and allergic diseases may facilitate development of novel preventive and treatment strategies. Based on our current knowledge, there are no currently available approved therapies for food allergy. More studies are needed to evaluate the safety and efficacy of allergen-specific and allergen-nonspecific approaches, as well as combination approaches.

Common food allergens and their IgE-binding epitopes

Food allergy is an adverse immune response to certain kinds of food. Although any food can cause allergic reactions, chicken egg, cow's milk, wheat, shellfish, fruit, and buckwheat account for 75% of food allergies in Japan. Allergen-specific immunoglobulin E (IgE) antibodies play a pivotal role in the development of food allergy. Recent advances in molecular biological techniques have enabled the efficient analysis of food allergens. As a result, many food allergens have been identified, and their molecular structure and IgE-binding epitopes have also been identified. Studies of allergens have demonstrated that IgE antibodies specific to allergen components and/or the peptide epitopes are good indicators for the identification of patients with food allergy, prediction of clinical severity and development of tolerance. In this review, we summarize our current knowledge regarding the allergens and IgE epitopes in the well-researched allergies to chicken egg, cow's milk, wheat, shrimp, and peanut.

Oral immunotherapy for food allergy: mechanisms and role in management

With the emergence of food allergy as an important public health problem, it has become clear that there is an unmet need in regard to treatment. In particular, IgE-mediated food allergy that is associated with risk of fatal anaphylaxis has been the subject of multiple studies in the past decade. The growing body of evidence derived from multiple centres and various study designs indicates that for IgE-mediated food allergy, immunomodulation through food immunotherapy is possible; however, the extent of protection afforded by such treatment is highly variable. At this time, the capacity for food immunotherapy to restore permanent tolerance to food has not been demonstrated conclusively. This review will discuss these topics as they apply to the most important studies of food oral immunotherapy.

Developments in the field of allergy in 2013 through the eyes of Clinical and Experimental Allergy

2013 was another exciting year for allergy in general and Clinical and Experimental Allergy in particular. In the field of asthma and rhinitis, there continued to be a focus on heterogeneity and phenotypes with increasing use of biostatistical techniques to determine clusters of similar populations. Obesity- and aspirin-associated disease are intriguing associations with asthma which were explored in a number of papers. We published a number of excellent papers on mechanisms of airway inflammation and how this relates to physiology, pathology, genetics and biomarkers in both human and experimental model systems. In terms of mechanisms, there is less on individual cell types in allergic disease at the moment, but the immunology of allergic disease continued to fascinate our authors. Another area that was popular both in the mechanisms and in the epidemiology sections was early life events and how these lead to allergic disease, with an increasing focus on the role of the microbiome and how this influences immune tolerance. In the clinical allergy section, oral immunotherapy for food allergy is clearly a major topic of interest at the moment as was in vitro testing to distinguish between sensitization and allergic disease. There was less on inhalant allergy this year, but a good representation from the drug allergy community including some interesting work on non-IgE-mediated mechanisms. In the allergen section, important new allergens continue to be discovered, but the major focus as in the last couple of years was on working out how component-resolved approaches can improve diagnosis and management of food and venom allergy.

Novel immunotherapy approaches to food allergy. Curr Opin Allergy Clin Immunol. 2014;14:549-556. [PMID: 25159183 DOI: 10.1097/aci.0000000000000109]

PURPOSE OF REVIEW

Despite reaching high percentages of desensitization using allergen-specific immunotherapy (SIT) in patients with food allergy, recent studies suggest only a low number of patients to reach persistent clinical tolerance. This review describes current developments in strategies to improve safety and long-term efficacy of SIT.

RECENT FINDINGS

Modified allergens or tolerogenic peptides, ultimately optimized for human leukocyte antigen background of the patient, are explored for tolerance induction, whereas anti-IgE antibody (Omalizumab) may be used to facilitate SIT safety. Adjunct therapies to enhance efficacy may make use of TH1 polarizing agents, for example, CpG-oligodeoxynucleotides combined with modified allergen packaged in nanoparticles. Preclinical studies showed insulin-like growth factor-2, intravenous immunoglobulin, Tregitopes or allergen encased oligomannose-coated liposomes capable of inducing regulatory T-cells, recognized for their importance in clinical tolerance induction. Dietary intervention strategies utilizing herbal formula 2, VSL#3, nondigestible short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides (scGOS/lcFOS) plus Bifidobacterium breve M-16V or n-3 long-chain polyunsaturated fatty acids may facilitate safety and/or a favourable milieu for tolerance induction.

SUMMARY

Combining SIT using (adapted) allergens or tolerogenic peptides with adjunct therapy may be essential to improve safety and/or efficacy. Beyond using targeted approaches, specific dietary components may be explored to reduce side-effects and support clinical tolerance induction by SIT.

Correlations between basophil activation, allergen-specific IgE with outcome and severity of oral food challenges

BACKGROUND

Double-blinded, placebo-controlled food challenges (DBPCFCs) remain the gold standard for diagnosing food allergies. Skin prick tests (SPTs) and allergen-specific IgE (sIgE) are routinely used in medical practice but are not sufficient to predict severity of clinical reactivity.

OBJECTIVE

To compare the utility of SPT wheal diameter, sIgE, allergen-specific IgG4 (sIgG4), total IgE (tIgE), sIgE/sIgG4 and sIgE/tIgE ratios, peanut component-specific IgE, and basophil activation in predicting outcome and severity of reactions at DBPCFCs.

METHODS

Sixty-seven subjects (12-45 years old) underwent DBPCFCs for peanut, tree nut, fish, shrimp, and/or sesame as part of screening for enrollment in a clinical trial. The SPT, sIgE, tIgE, sIgG4, and peanut component-specific IgE (if applicable) levels were measured. CD63 upregulation on basophils in response to in vitro allergen challenge was analyzed by flow cytometry. Correlations between these measurements and DBPCFC severity scores were analyzed.

RESULTS

The SPT and sIgE showed a weak correlation with DBPCFC severity scores, but tIgE and sIgG4 did not. The sIgE/sIgG4 ratio differentiated between positive and negative reactions but did not correlate with DBPCFC severity scores. A low positive correlation was seen between DBPCFC severity score and Ara h 2 IgE, whereas a low negative correlation with Ara h 8 IgE was observed. Basophil activation was positively correlated with DBPCFC severity scores. Receiver operating characteristic curves showed basophil reactivity had the largest area under the curve at 0.904 and sIgE at 0.870.

CONCLUSION

These results indicate that basophil activation testing can enhance discrimination between allergic and nonallergic individuals and could serve as an additional tool to predict clinical severity.

Recombinant NAD-dependent SIR-2 protein of Leishmania donovani: immunobiochemical characterization as a potential vaccine against visceral leishmaniasis

Background

The development of a vaccine conferring long-lasting immunity remains a challenge against visceral leishmaniasis (VL). Immunoproteomic characterization of Leishmania donovani proteins led to the identification of a novel protein NAD+-dependent Silent Information regulatory-2 (SIR2 family or sirtuin) protein (LdSir2RP) as one of the potent immunostimulatory proteins. Proteins of the SIR2 family are characterized by a conserved catalytic domain that exerts unique NAD-dependent deacetylase activity. In the present study, an immunobiochemical characterization of LdSir2RP and further evaluation of its immunogenicity and prophylactic potential was done to assess for its possible involvement as a vaccine candidate against leishmaniasis.

Methodology/Principal Findings

LdSir2RP was successfully cloned, expressed and purified. The gene was present as a monomeric protein of ~45 kDa and further established by the crosslinking experiment. rLdSir2RP shown cytosolic localization in L. donovani and demonstrating NAD+-dependent deacetylase activity. Bioinformatic analysis also confirmed that LdSir2RP protein has NAD binding domain. The rLdSir2RP was further assessed for its cellular response by lymphoproliferative assay and cytokine ELISA in cured Leishmania patients and hamsters (Mesocricetus auratus) in comparison to soluble Leishmania antigen and it was observed to stimulate the production of IFN-γ, IL-12 and TNF-α significantly but not the IL-4 and IL-10. The naïve hamsters when vaccinated with rLdSir2RP alongwith BCG resisted the L. donovani challenge to the tune of ~75% and generated strong IL-12 and IFN-γ mediated Th1 type immune response thereof. The efficacy was further supported by remarkable increase in IgG2 antibody level which is indicative of Th1 type of protective response. Further, with a possible implication in vaccine design against VL, identification of potential T-cell epitopes of rLdSir2RP was done using computational approach.

Conclusion/Significance

The immunobiochemical characterization strongly suggest the potential of rLdSir2RP as vaccine candidate against VL and supports the concept of its being effective T-cell stimulatory antigen.

Visceral Leishmaniasis (VL) is the most fatal form of leishmaniasis disease in Indian subcontinent. Through proteomic approaches, NAD-dependent Silent information regulator-2 was identified as one of the potent immunostimulatory proteins. Herein, it was first reported the cloning, expression, purification and immunobiochemical characterization of a NAD+-dependent protein from Leishmania donovani. The gene encodes a monomeric protein (LdSir2RP) of approximately 45 kDa and showed NAD+-dependent deacetylase activity. LdSir2RP was immunodetected in whole cell lysate of L. donovani and further it immunolocalized in cytoplasm of the Leishmania parasite. Recombinant protein rLdSir2RP shown immunogenicity in PBMCs of cured Leishmania patients and hamsters (Mesocricetus auratus). rLdSir2RP stimulated the production of IFN-γ, IL-12 and TNF-α but not IL-4 and IL-10. This was further supported by remarkable increase in IgG2 antibody level.

It was further demonstrated that rLdSir2RP was able to provide considerable protection to hamsters against L. donovani challenge. These results supported by the increased iNOS mRNA transcript and the specific Th1-type cytokines—IFN-γ, IL-12 and TNF-α and down-regulation of IL-4, IL-10 and TGF-β. Hence, it is inferred that rLdSir2RP confer significant protection against experimental VL and considered as potential vaccine targets against visceral leishmaniasis.

The role of casein-specific IgA and TGF-β in children with food protein-induced enterocolitis syndrome to milk

BACKGROUND

Food protein-induced enterocolitis syndrome (FPIES) is a gastrointestinal hypersensitivity disorder with a poorly understood pathophysiology and no biomarkers to aid in diagnosis.

OBJECTIVE

To investigate humoral and cellular responses to casein in children with milk-FPIES, including the role of casein-specific (cs) IgA and T-cell mediated TGF-β responses.

PATIENTS AND METHODS

Thirty-one children previously diagnosed with milk-FPIES were challenged with milk. Twelve age-matched children with FPIES to other foods and 6 milk-tolerant children without a history of FPIES were used as controls. Casein-specific IgE, IgG, IgG4, and IgA were measured in serum and TGF-β levels in supernatants of casein-stimulated PBMCs.

RESULT

Twenty-six children with milk-FPIES reacted (active milk-FPIES) and five tolerated milk (milk-FPIES resolved) during food challenge. All of them had significantly lower levels of csIgG, csIgG4, and csIgA than control children (p-value<0.001). There were no TGF-β responses in supernatants of active milk-FPIES children.

CONCLUSION

Children with milk-FPIES have low levels of csIgG, csIgG4, and csIgA. In particular, children with active FPIES to cow's milk have deficient T-cell mediated TGF-β responses to casein, rendering TGF-β a promising biomarker in identifying children who are likely to experience FPIES reactions to this allergen. Prospective studies are needed to validate these findings, elucidate their role in FPIES pathophysiology, and establish the diagnostic utility of TGF-β in milk-induced FPIES.

Diagnosis and management of food allergies: new and emerging options: a systematic review

It is reported that 6% of children and 3% of adults have food allergies, with studies suggesting increased prevalence worldwide over the last few decades. Despite this, our diagnostic capabilities and techniques for managing patients with food allergies remain limited. We have conducted a systematic review of literature published within the last 5 years on the diagnosis and management of food allergies. While the gold standard for diagnosis remains the double-blind, placebo-controlled food challenge, this assessment is resource intensive and impractical in most clinical situations. In an effort to reduce the need for the double-blind, placebo-controlled food challenge, several risk-stratifying tests are employed, namely skin prick testing, measurement of serum-specific immunoglobulin E levels, component testing, and open food challenges. Management of food allergies typically involves allergen avoidance and carrying an epinephrine autoinjector. Clinical research trials of oral immunotherapy for some foods, including peanut, milk, egg, and peach, are under way. While oral immunotherapy is promising, its readiness for clinical application is controversial. In this review, we assess the latest studies published on the above diagnostic and management modalities, as well as novel strategies in the diagnosis and management of food allergy.

In silico prediction of the T-cell and IgE-binding epitopes of Per a 6 and Bla g 6 allergens in cockroaches

Per a 6 and Bla g 6 are cockroach allergens found in Periplaneta americana and Blattella germanica, respectively. The objective of the present study was to predict the B‑ and T‑cell epitopes of the Per a 6 and Bla g 6 allergens. Three immunoinformatics tools, the DNAStar Protean system, the Bioinformatics Predicted Antigenic Peptides system and the BepiPred 1.0 server, were used to predict the potential B‑cell epitopes, while Net‑MHCIIpan‑2.0 and NetMHCII‑2.2 were used to predict the T‑cell epitopes of the two allergens. As a result, seven peptides were predicted in the Per a 6 allergen and seven peptides were predicted in the Bla g 6 allergen in the B‑cell epitope predictions. In the T‑cell prediction, the Per a 6 allergen was predicted to have nine strongly binding nonamer core epitope sequences (IC50<50 nm) and 28 weakly binding sequences (50 nm<IC50<500 nm), while the Bla g 6 allergen was predicted to have nine strong binders and 25 weak binders. These results may be useful for peptide‑based vaccine designs.

In Silico Prediction of T and B Cell Epitopes of Der f 25 in Dermatophagoides farinae

The house dust mites are major sources of indoor allergens for humans, which induce asthma, rhinitis, dermatitis, and other allergic diseases. Der f 25 is a triosephosphate isomerase, representing the major allergen identified in Dermatophagoides farinae. The objective of this study was to predict the B and T cell epitopes of Der f 25. In the present study, we analyzed the physiochemical properties, function motifs and domains, and structural-based detailed features of Der f 25 and predicted the B cell linear epitopes of Der f 25 by DNAStar protean system, BPAP, and BepiPred 1.0 server and the T cell epitopes by NetMHCIIpan-3.0 and NetMHCII-2.2. As a result, the sequence and structure analysis identified that Der f 25 belongs to the triosephosphate isomerase family and exhibited a triosephosphate isomerase pattern (PS001371). Eight B cell epitopes (11-18, 30-35, 71-77, 99-107, 132-138, 173-187, 193-197, and 211-224) and five T cell epitopes including 26-34, 38-54, 66-74, 142-151, and 239-247 were predicted in this study. These results can be used to benefit allergen immunotherapies and reduce the frequency of mite allergic reactions.

Future Therapies for IgE-Mediated Food Allergy

Food allergy is prevalent, affecting approximately 4-8% of children. There is no currently approved treatment for food allergy, and while strict allergen avoidance is recommended it is difficult to achieve and therefore accidental exposures and reactions are common. There is an urgent need for the development of therapeutic approaches that will improve the health and quality of life of children with food allergy. The majority of current clinical research focus is on specific food allergen immunotherapy through oral, sublingual, or epicutaneous routes. Pre-clinical research has focused on making improvements to the safety and efficacy of allergen immunotherapy through modifications of allergen structure and addition of immuno-modulatory factors. The number of novel therapeutics for food allergy reaching the level of clinical trials remains disappointingly low, and there is a need for an expansion of pre-clinical research to provide safe, practical and novel approaches to the treatment of food allergy.

Ara h 1 CD4+ T cell epitope-based peptides: candidates for a peanut allergy therapeutic

Background

Peanut allergy is a life-threatening condition; there is currently no cure. While whole allergen extracts are used for specific immunotherapy for many allergies, they can cause severe reactions and even fatalities in peanut allergy.

Objective

To identify short, HLA-degenerate CD4⁺ T cell epitope-based peptides of the major peanut allergen Ara h 1 that target allergen-specific T cells without causing IgE-mediated inflammatory cell activation, as candidates for safe peanut-specific immunotherapy.

Methods

Ara h 1-specific CD4⁺ T cell lines (TCL) were generated from peripheral blood mononuclear cells (PBMC) of peanut-allergic subjects using CFSE-based methodology. T cell epitopes were identified using CFSE and thymidine-based proliferation assays. Epitope HLA-restriction was investigated using blocking antibodies, HLA-genotyping and epitope prediction algorithms. Functional peanut-specific IgE reactivity to peptides was assessed by basophil activation assay.

Results

A total of 145 Ara h 1-specific TCL were generated from 18 HLA-diverse peanut-allergic subjects. The TCL recognized 20-mer peptides throughout Ara h 1. Nine 20-mers containing the most frequently recognized epitopes were selected and their recognition confirmed in 18 additional peanut-allergic subjects. Ten core epitopes were mapped within these 20-mers. These were HLA-DQ and/or HLA–DR restricted, with each presented on at least two different HLA-molecules. Seven short (≤ 20 aa) non-basophil-reactive peptides encompassing all core epitopes were designed and validated in peanut-allergic donor PBMC T cell assays.

Conclusions and Clinical Relevance

Short CD4⁺ T cell epitope-based Ara h 1 peptides were identified as novel candidates for a safe, T cell targeted peanut-specific immunotherapy for HLA-diverse populations.

Use of animal models to investigate major allergens associated with food allergy

Food allergy is an emerging epidemic that affects all age groups, with the highest prevalence rates being reported amongst Western countries such as the United States (US), United Kingdom (UK), and Australia. The development of animal models to test various food allergies has been beneficial in allowing more rapid and extensive investigations into the mechanisms involved in the allergic pathway, such as predicting possible triggers as well as the testing of novel treatments for food allergy. Traditionally, small animal models have been used to characterise immunological pathways, providing the foundation for the development of numerous allergy models. Larger animals also merit consideration as models for food allergy as they are thought to more closely reflect the human allergic state due to their physiology and outbred nature. This paper will discuss the use of animal models for the investigation of the major food allergens; cow's milk, hen's egg, and peanut/other tree nuts, highlight the distinguishing features of each of these models, and provide an overview of how the results from these trials have improved our understanding of these specific allergens and food allergy in general.