Development of a hypoallergenic recombinant parvalbumin for first-in-man subcutaneous immunotherapy of fish allergy

Subcutaneous Immunotherapy of Food Allergy

PURPOSE OF REVIEW

While there are compelling arguments for developing subcutaneous allergen-specific immunotherapy for alleviation of food allergies, there is a limited number of studies in the public domain. The review seeks to present the approaches taken, to explain the paucity of studies, and to identify new roads for development.

RECENT FINDINGS

A literature search revealed clinical trials of immunotherapy of food allergies to fish and peanut, but studies had limited patient numbers, short treatment courses and follow-up periods. Indications, but no clearcut effects, were seen with both classical allergen extracts and hypo-allergenic preparations. A special case is the influence on cross-reactive food allergies, when subcutaneously administered birch-pollen extracts are used for treatment of birch pollen hayfever and/or asthma. Again indications, but no convincing efficacy has been registered. Newer developments include recombinant hypoallergens and DNA-technologies. Subcutaneous immunotherapy for food allergies has not matured to provide clinically relevant treatment opportunities.

Structural analysis of human IgE monoclonal antibody epitopes on dust mite allergen Der p 2

BACKGROUND

Human IgE (hIgE) mAbs against major mite allergen Der p 2 developed using human hybridoma technology were used for IgE epitope mapping and analysis of epitopes associated with the hIgE repertoire.

OBJECTIVE

We sought to elucidate the new hIgE mAb 4C8 epitope on Der p 2 and compare it to the hIgE mAb 2F10 epitope in the context of the allergenic structure of Der p 2.

METHODS

X-ray crystallography was used to determine the epitope of anti-Der p 2 hIgE mAb 4C8. Epitope mutants created by targeted mutagenesis were analyzed by immunoassays and in vivo using a human high-affinity IgE receptor (FcεRIα)-transgenic mouse model of passive systemic anaphylaxis.

RESULTS

The structure of recombinant Der p 2 with hIgE mAb 4C8 Fab was determined at 3.05 Å. The newly identified epitope region does not overlap with the hIgE mAb 2F10 epitope or the region recognized by 3 overlapping hIgE mAbs (1B8, 5D10, and 2G1). Compared with wild-type Der p 2, single or double 4C8 and 2F10 epitope mutants bound less IgE antibodies from allergic patients by as much as 93%. Human FcεRIα-transgenic mice sensitized by hIgE mAbs, which were susceptible to anaphylaxis when challenged with wild-type Der p 2, could no longer cross-link FcεRI to induce anaphylaxis when challenged with the epitope mutants.

CONCLUSIONS

These data establish the structural basis of allergenicity of 2 hIgE mAb nonoverlapping epitopes on Der p 2, which appear to make important contributions to the hIgE repertoire against Der p 2 and provide molecular targets for future design of allergy therapeutics.

Streptococcus iniae in aquaculture: a review of pathogenesis, virulence, and antibiotic resistance

One of the main challenges in aquaculture is pathogenic bacterial control. Streptococcus iniae stands out for its ability to cause high mortality rates in populations of commercially important fish populations and its recent recognition as an emerging zoonotic pathogen. The rise in identifying over 80 strains some displaying antibiotic resistance coupled with the emerging occurrence of infections in marine mammal species and wild fish underscores the urgent need of understanding pathogenesis, virulence and drug resistance mechanisms of this bacterium. This understanding is crucial to ensure effective control strategies. In this context, the present review conducts a bibliometric analysis to examine research trends related to S. iniae, extending into the mechanisms of infection, virulence, drug resistance and control strategies, whose relevance is highlighted on vaccines and probiotics to strengthen the host immune system. Despite the advances in this field, the need for developing more efficient identification methods is evident, since they constitute the basis for accurate diagnosis and treatment.

The Future of Food Allergy Management: Advancements in Therapies

PURPOSE OF REVIEW

To review current and future treatment options for IgE-mediated food allergy.

RECENT FINDINGS

Recent years have seen major developments in both allergen-specific and allergen-non-specific treatment options, with the first FDA-approved peanut oral immunotherapy (OIT) product becoming available in 2020. In addition to OIT, other immunotherapy modalities, biologics, adjunct therapies, and novel therapeutics are under investigation. Food allergy is a potentially life-threatening condition associated with a significant psychosocial impact. Numerous products and protocols are under investigation, with most studies focusing on OIT. A high rate of adverse events, need for frequent office visits, and cost remain challenges with OIT. Further work is needed to unify outcome measures, develop treatment protocols that minimize adverse events, establish demographic and clinical factors that influence candidate selection, and identify patient priorities.

Current practices and future trends in cockroach allergen immunotherapy

PURPOSE OF REVIEW

This review evaluates the current modes of allergen-specific immunotherapy for cockroach allergens, in terms of clinical outcomes and explores future trends in the research and development needed for a more targeted cockroach immunotherapy approach with the best efficacy and minimum adverse effects.

SUMMARY

Cockroach allergy is an important risk factor for allergic rhinitis in the tropics, that disproportionately affects children and young adults and those living in poor socio-economic environments. Immunotherapy would provide long-lasting improvement in quality of life, with reduced medication intake. However, the present treatment regime is long and has a risk of adverse effects. In addition, cockroach does not seem to have an immuno-dominant allergen, that has been traditionally used to treat allergies from other sources. Future trends of cockroach immunotherapy involve precision diagnosis, to correctly identify the offending allergen. Next, precision immunotherapy with standardized allergens, which have been processed in a way that maintains an immunological response without allergic reactions. This approach can be coupled with modern adjuvants and delivery systems that promote a Th1/Treg environment, thereby modulating the immune response away from the allergenic response.

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.

Seafood allergy: Allergen, epitope mapping and immunotherapy strategy

Seafoods are fashionable delicacies with high nutritional values and culinary properties, while seafood belongs to worldwide common food allergens. In recent years, many seafood allergens have been identified, while the diversity of various seafood species give a great challenge in identifying and characterizing seafood allergens, mapping IgE-binding epitopes and allergen immunotherapy development, which are critical for allergy diagnostics and immunotherapy treatments. This paper reviewed the recent progress on seafood (fish, crustacean, and mollusk) allergens, IgE-binding epitopes and allergen immunotherapy for seafood allergy. In recent years, many newly identified seafood allergens were reported, this work concluded the current situation of seafood allergen identification and designation by the World Health Organization (WHO)/International Union of Immunological Societies (IUIS) Allergen Nomenclature Sub-Committee. Moreover, this review represented the recent advances in identifying the IgE-binding epitopes of seafood allergens, which were helpful to the diagnosis, prevention and treatment for seafood allergy. Furthermore, the allergen immunotherapy could alleviate seafood allergy and provide promising approaches for seafood allergy treatment. This review represents the recent advances and future outlook on seafood allergen identification, IgE-binding epitope mapping and allergen immunotherapy strategies for seafood allergy prevention and treatment.

Cross-reactive monoclonal antibodies against fish parvalbumins as a tool for studying antigenic similarity of different parvalbumins and analysis of fish extracts

Fish parvalbumins are heat-stable calcium-binding proteins that are highly cross-reactive in causing allergy symptoms in fish-sensitized patients. The reactivities of parvalbumin-specific monoclonal or polyclonal antibodies with parvalbumins of different fish species allowed their application for development of various immunoassays for allergen identification in fish samples. In this study, monoclonal antibodies (MAbs) were generated against two parvalbumins - natural Atlantic cod parvalbumin and recombinant common carp β-parvalbumin expressed in E. coli. Large collections of recombinant parvalbumins and natural allergen extracts of different fish species and other animals were used to identify the specificities of these MAbs using ELISA, Western blot, and dot blot. MAbs demonstrated different patterns of cross-reactivities with recombinant parvalbumins. Their binding affinities were affected by the addition and removal of Ca²⁺ ions. Moreover, all MAbs showed a broad reactivity with the target antigens in natural fish, chicken, and pork extracts. The ability of two MAbs (clones 7B2 and 3F6) to identify and isolate native parvalbumins from allergen extracts was confirmed by Western blot. Epitope mapping using recombinant fragments of Atlantic cod parvalbumin (Gad m 1) and common carp parvalbumin (Cyp c 1) revealed that 4 out of 5 MAbs recognize parvalbumin regions that contain calcium binding sites. In conclusion, the generated broadly reactive well-characterized MAbs against fish β-parvalbumins could be applied for investigation of parvalbumins of fish and other animals and their detection in allergen extracts.

An overview of the current state of food desensitization

PURPOSE OF REVIEW

To highlight the current evidence on food desensitization in children with food allergy.

RECENT FINDINGS

Food Allergen Specific Immunotherapy (FA-AIT) is currently recognised as a treatment option for treating children with allergy at least to the main common foods (i.e. milk, egg and peanut). The oral route of administration has been proven to be the most effective in achieving desensitisation. Efforts are devoted to overcome the current unmet needs mainly related to safety issues and long-term efficacy, as well as adherence to the treatment and improvement of health-related quality of life. In this perspective, alternative routes of administration and adjunctive treatments are under investigation.

SUMMARY

The future of food allergy management is a personalised approach based on a shared decision-making that takes into account the needs of patients and families. Health professionals will be able to offer multiple treatment options, including FA-AIT with adjunctive or alternative therapies. Thus, patients should be correctly identified, using validated predictive factors, in order to select appropriate candidates for these therapies.

A practical focus on fish and shellfish oral immunotherapy

Although fish and shellfish allergies represent common worldwide allergies, with anaphylaxis being reportedly frequent, treatment approaches, e.g., oral immunotherapy (OIT), are uncommonly performed. A review of the limited literature is discussed here. Both practical and immunologic challenges are common with seafood OIT, including taste, odor, unclear and potentially inconsistent cross-reactivity, and alteration of protein concentration during the cooking process as well as other concerns. Ongoing attempts at standardization of this OIT process should be considered. The experienced OIT physician may consider this treatment in patients who are motivated to begin OIT.

Immunotherapies in the treatment of immunoglobulin E‑mediated allergy: Challenges and scope for innovation (Review)

Immunoglobulin E (IgE)‑mediated allergy or hypersensitivity reactions are generally defined as an unwanted severe symptomatic immunological reaction that occurs due to shattered or untrained peripheral tolerance of the immune system. Allergen‑specific immunotherapy (AIT) is the only therapeutic strategy that can provide a longer‑lasting symptomatic and clinical break from medications in IgE‑mediated allergy. Immunotherapies against allergic diseases comprise a successive increasing dose of allergen, which helps in developing the immune tolerance against the allergen. AITs exerttheirspecial effectiveness directly or indirectly by modulating the regulator and effector components of the immune system. The number of success stories of AIT is still limited and it canoccasionallyhave a severe treatment‑associated adverse effect on patients. Therefore, the formulation used for AIT should be appropriate and effective. The present review describes the chronological evolution of AIT, and provides a comparative account of the merits and demerits of different AITs by keeping in focus the critical guiding factors, such as sustained allergen tolerance, duration of AIT, probability of mild to severe allergic reactions and dose of allergen required to effectuate an effective AIT. The mechanisms by which regulatory T cells suppress allergen‑specific effector T cells and how loss of natural tolerance against innocuous proteins induces allergy are reviewed. The present review highlights the major AIT bottlenecks and the importantregulatory requirements for standardized AIT formulations. Furthermore, the present reviewcalls attention to the problem of 'polyallergy', which is still a major challenge for AIT and the emerging concept of 'component‑resolved diagnosis' (CRD) to address the issue. Finally, a prospective strategy for upgrading CRD to the next dimension is provided, and a potential technology for delivering thoroughly standardized AIT with minimal risk is discussed.

Fish Allergenicity Modulation Using Tailored Enriched Diets—Where Are We?

Food allergy is an abnormal immune response to specific proteins in a certain food. The chronicity, prevalence, and the potential fatality of food allergy, make it a serious socio-economic problem. Fish is considered the third most allergenic food in the world, affecting part of the world population with a higher incidence in children and adolescents. The main allergen in fish, responsible for the large majority of fish-allergic reactions in sensitized patients, is a small and stable calcium-binding muscle protein named beta-parvalbumin. Targeting the expression or/and the 3D conformation of this protein by adding specific molecules to fish diets has been the innovative strategy of some researchers in the fields of fish allergies and nutrition. This has shown promising results, namely when the apo-form of β-parvalbumin is induced, leading in the case of gilthead seabream to a 50% reduction of IgE-reactivity in fish allergic patients.

The Allergen-Specific IgE Concentration Is Important for Optimal Histamine Release From Passively Sensitized Basophils

Background

The basophil histamine release (HR) assay can be used for allergy diagnosis in addition to the conventional measurement of allergen-specific IgE (sIgE). Passive sensitization of basophils increases the versatility and allows testing the biological relevance of allergen-induced IgE cross-linking in any serum unbiased by the cellular component. However, not all the patient sera perform equally well and we hypothesized that the absolute level and fraction of sIgE affect the performance. Choosing birch pollen allergy as a model, we investigated the concentration of sIgE needed for successful passive sensitization using soluble- or matrix-fixed Bet v 1.

Methods

Twenty-eight sera with Bet v 1 sIgE [7 sera within each allergy class (1: 0.1–0.70 kUA/L, 2: 0.71–3.50 kUA/L, 3: 3.51–17.50 kUA/L, and 4+: >17.50 kUA/L)] and a negative control serum pool were used to passively sensitize donor basophils, obtained from buffy coat blood (n = 3). The cells were incubated (30 min) with a soluble allergen (rBet v 1 from 0.2 to 50 ng/ml), matrix-fixed allergen (ImmunoCAP™ containing recombinant Bet v 1), or phorbol 12-myristate 13-acetate (PMA)/ionomycin mixture (maximal HR) and released histamine was quantified fluorometrically.

Results

The lowest level of Bet v 1 sIgE generating a detectable HR (HR > 10% of maximal release) in all the 3 runs was found to be 1.25 kUA/L (corresponding to allergy class 2, 0.71–3.50 kUA/L). Furthermore, sera from allergy classes 3 and 4+ ascertained a significant reproducible HR: 42/42 vs. 5/21 in allergy class 1 and 15/21 in allergy class 2. Using ImmunoCAP™s containing Bet v 1 as a matrix-fixed allergen system, similar results were obtained where the lowest sIgE concentration mediating an HR was 1.68 kUA/L and 7/7 for both allergy classes 3 and 4+.

Conclusion

The results demonstrate that the IgE titer is strikingly robust in predicting the ability to sensitize basophils and produce a measurable HR.

Allergen Immunotherapy: Current and Future Trends

Allergen immunotherapy (AIT) is the sole disease-modifying treatment for allergic rhinitis; it prevents rhinitis from progressing to asthma and lowers medication use. AIT against mites, insect venom, and certain kinds of pollen is effective. The mechanism of action of AIT is based on inducing immunological tolerance characterized by increased IL-10, TGF-β, and IgG4 levels and Treg cell counts. However, AIT requires prolonged schemes of administration and is sometimes associated with adverse reactions. Over the last decade, novel forms of AIT have been developed, focused on better allergen identification, structural modifications to preserve epitopes for B or T cells, post-traductional alteration through chemical processes, and the addition of adjuvants. These modified allergens induce clinical-immunological effects similar to those mentioned above, increasing the tolerance to other related allergens but with fewer side effects. Clinical studies have shown that molecular AIT is efficient in treating grass and birch allergies. This article reviews the possibility of a new AIT to improve the treatment of allergic illness.

Reducing the Allergenicity of Shrimp Tropomyosin and Allergy Desensitization Based on Glycation Modification

Shrimp is a major allergic food that could trigger severe food allergy, with the most significant and potent allergen of shrimp referred to as tropomyosin (TM). Glycation modification (Maillard reaction) could reportedly weaken the allergenicity of TM and generate hypoallergenic TM, while up to now, there is still a lack of investigations on the hypoallergenic glycated tropomyosin (GTM) as a candidate immunotherapy for desensitizing the shrimp TM-induced allergy. This study analyzed the effects of glycation modification on decreasing the allergenicity of TM and generated hypoallergenic GTM and how GTM absorbed to the Al(OH)₃ function as a candidate immunotherapy for desensitizing allergy. As the results, in comparison to TM, the saccharides of smaller molecular sizes could lead to more advanced glycation end products in GTMs than saccharides of greater molecular sizes, and TM glycated by saccharides of different molecular sizes (glucose, maltose, maltotriose, maltopentaose, and maltoheptaose) exhibited lower allergenicity as a hypoallergen upon activating the allergic reactions of the mast cell and mouse model, while TM glycated by maltose had insignificant allergenicity changes upon activating the allergic reactions of the mast cell and mouse model. In addition, the hypoallergenic GTM + Al(OH)₃ was efficient as a candidate immunotherapy; this work intended to offer preclinical data to promote GTM + Al(OH)₃ as a candidate allergen-specific immunotherapy for desensitizing the allergy reactions for patients allergic to shrimp food.

Fish Allergy Around the World—Precise Diagnosis to Facilitate Patient Management

The accurate and precise diagnosis of IgE-mediated fish allergy is one of the biggest challenges in allergy diagnostics. A wide range of fish species that belong to evolutionary distant classes are consumed globally. Moreover, each fish species may contain multiple isoforms of a given allergen that often differ in their allergenicity. Recent studies indicated that the cross-reactivity between different fish species is limited in some cases and depends on the evolutionary conservation of the involved allergens. Fish allergens belong to several protein families with different levels of stability to food processing. Additionally, different preparation methods may contribute to specific sensitization patterns to specific fish species and allergens in different geographic regions. Here, we review the challenges and opportunities for improved diagnostic approaches to fish allergy. Current diagnostic shortcomings include the absence of important region-specific fish species in commercial in vitro and in vivo tests as well as the lack of their standardization as has been recently demonstrated for skin prick test solutions. These diagnostic shortcomings may compromise patients' safety by missing some of the relevant species and yielding false negative test results. In contrast, the avoidance of all fish as a common management approach is usually not necessary as many patients may be only sensitized to specific species and allergens. Although food challenges remain the gold standard, other diagnostic approaches are investigated such as the basophil activation test. In the context of molecular allergy diagnosis, we discuss the usefulness of single allergens and raw and heated fish extracts. Recent developments such as allergen microarrays offer the possibility to simultaneously quantify serum IgE specific to multiple allergens and allergen sources. Such multiplex platforms may be used in the future to design diagnostic allergen panels covering evolutionary distant fish species and allergens relevant for particular geographic regions.

From Allergen Molecules to Molecular Immunotherapy of Nut Allergy: A Hard Nut to Crack

Peanuts and tree nuts are two of the most common elicitors of immunoglobulin E (IgE)-mediated food allergy. Nut allergy is frequently associated with systemic reactions and can lead to potentially life-threatening respiratory and circulatory symptoms. Furthermore, nut allergy usually persists throughout life. Whether sensitized patients exhibit severe and life-threatening reactions (e.g., anaphylaxis), mild and/or local reactions (e.g., pollen-food allergy syndrome) or no relevant symptoms depends much on IgE recognition of digestion-resistant class I food allergens, IgE cross-reactivity of class II food allergens with respiratory allergens and clinically not relevant plant-derived carbohydrate epitopes, respectively. Accordingly, molecular allergy diagnosis based on the measurement of allergen-specific IgE levels to allergen molecules provides important information in addition to provocation testing in the diagnosis of food allergy. Molecular allergy diagnosis helps identifying the genuinely sensitizing nuts, it determines IgE sensitization to class I and II food allergen molecules and hence provides a basis for personalized forms of treatment such as precise prescription of diet and allergen-specific immunotherapy (AIT). Currently available forms of nut-specific AIT are based only on allergen extracts, have been mainly developed for peanut but not for other nuts and, unlike AIT for respiratory allergies which utilize often subcutaneous administration, are given preferentially by the oral route. Here we review prevalence of allergy to peanut and tree nuts in different populations of the world, summarize knowledge regarding the involved nut allergen molecules and current AIT approaches for nut allergy. We argue that nut-specific AIT may benefit from molecular subcutaneous AIT (SCIT) approaches but identify also possible hurdles for such an approach and explain why molecular SCIT may be a hard nut to crack.

Update of the S2k guideline on the management of IgE-mediated food allergies

Not available.

Regulatory Requirements for the Quality of Allergen Products for Allergen Immunotherapy of Food Allergy

Purpose of Review

Medicinal products for allergen immunotherapy (AIT) of food allergies have gained enormous momentum in recent years. With this new class of products entering marketing authorization procedures, compliance to regulatory requirements becomes a critical element. Here, an overview is provided on specific requirements and aspects concerning the quality control and manufacturing of these products.

Recent Findings

Recent developments in the field of AIT for food allergies are divers, including products for oral, epicutaneous, and subcutaneous application, most notably targeting egg, milk, and peanut allergy. As the source materials for food AIT product are typically produced for food consumption and not for medicinal purposes, unique challenges arise in the manufacturing processes and controls of these medicinal products. Individual approaches are needed to assure acceptable quality, including control of relevant quantitative and qualitative characteristics. Major characteristics for quality verification include determination of protein content, total allergenic activity, and major allergen content. The applied manufacturing processes need to be established such that relevant process parameters are kept within justified limits and consistency of produced batches is assured.

Summary

Allergen products for food AIT present specific challenges with respect to quality aspects that differentiate them from other commonly available AIT products. While established regulation is available and provides clear guidance for most aspects, other issues require consideration of new and individual settings relevant here. Consequently, as experience grows, respective amendments to currently available guidance may be needed.

History of safe exposure and bioinformatic assessment of phosphomannose-isomerase (PMI) for allergenic risk

Newly expressed proteins in genetically engineered crops are evaluated for potential cross reactivity to known allergens as part of their safety assessment. This assessment uses a weight-of-evidence approach. Two key components of this allergenicity assessment include any history of safe human exposure to the protein and/or the source organism from which it was originally derived, and bioinformatic analysis identifying amino acid sequence relatedness to known allergens. Phosphomannose-isomerase (PMI) has been expressed in commercialized genetically engineered (GE) crops as a selectable marker since 2010 with no known reports of allergy, which supports a history of safe exposure, and GE events expressing the PMI protein have been approved globally based on expert safety analysis. Bioinformatic analyses identified an eight-amino-acid contiguous match between PMI and a frog parvalbumin allergen (CAC83047.1). While short amino acid matches have been shown to be a poor predictor of allergen cross reactivity, most regulatory bodies require such matches be assessed in support of the allergenicity risk assessment. Here, this match is shown to be of negligible risk of conferring cross reactivity with known allergens.

Investigation of glycated shrimp tropomyosin as a hypoallergen for potential immunotherapy

Tropomyosin (TM) is the most important allergen in shrimps that could cause food allergy. Glycation is reported to be effective in reducing TM allergenicity and produce hypoallergen; however, up to now, there are very few reports on the potential of hypoallergenic glycated TM (GTM) as allergen immunotherapy for shrimp TM-induced food allergy. This study investigated the glycation of TM-produced hypoallergen and the immunotherapeutic efficacy of GTM + Al(OH)₃ as potential allergen immunotherapy. Compared to TM, the TM glycated by glucose (TM-G), maltotriose (TM-MTS), maltopentaose (TM-MPS) and maltoheptaose (TM-MHS) had weaker allergy activation on mast cells and mouse model as a hypoallergen. However, the TM glycated by maltose (TM-M) insignificantly affected the allergenicity. In addition, the GTM absorbed into Al(OH)₃ could be efficacious as potential allergen immunotherapy, particularly for the TM glycated by the saccharides having larger molecular size (e.g., TM-MHS), which could provide preclinical data to develop GTM + Al(OH)₃ as a candidate immunotherapy for shrimp allergic patients.

Vaccines as therapies for food allergies

Food allergy is a growing public health epidemic with few available treatments beyond allergen avoidance and rescue medications for accidental exposures. A major focus of therapeutic development for food allergies is allergen-specific immunotherapy (AIT) in which patients are exposed to increasing amounts of allergen in controlled dosing to induce desensitization or tolerance. The work of the past few decades has culminated in the recent FDA approval of a peanut product for oral AIT for peanut allergies. Despite these advances, current AIT protocols are cumbersome, take a long time to reach clinical benefit and often have significant side effects. Therefore, there is a great need to develop new therapeutics for food allergy. One area of research aims to improve AIT through the use of adjuvants which are substances traditionally added to vaccines to stimulate or direct a specific immune response. Adjuvants that induce Th1-polarized and regulatory immune responses while suppressing Th2 immunity have shown the most promise in animal models. The addition of adjuvants to AIT may reduce the amount and frequency of allergen required to achieve clinical benefit and may induce more long-lasting immune responses. In this chapter, we highlight examples of adjuvanted AIT and vaccines in development to treat food allergies.

Novel diagnostic techniques and therapeutic strategies for IgE-mediated food allergy

Background: Immunoglobulin E (IgE) mediated food allergy is a potentially life-threatening condition and represents a heavy burden for patients and their families. Identification of the most suitable way for management of each patient has currently become the primary goal for physicians. Methods: This study reviewed the current literature related to IgE-mediated food allergy. Results: The use of innovative diagnostic tools, such as allergen-specific IgG4 determination, basophil activation test, and component-resolved diagnostics, is currently available to facilitate a proper diagnosis of food allergy. After several decades of "passive clinical management" of the disease, which was based only on avoidance of the allergenic food and the use of epinephrine in the event of anaphylaxis, there has been a switch to active treatment. The most recent evidence-practice guidelines strongly recommend the use of immunotherapy as an effective therapeutic option, particularly in cases of allergy to cow's milk, egg, or peanut. The use of omalizumab, in association with immunotherapy or alone, has been tested in several studies, and results on its effectiveness seemed to be encouraging. Other biologics, such as dupilumab, reslizumab, mepolizumab, and other anticytokines therapies, are being investigated. Another interesting future treatment strategy could be the use of DNA vaccines. Conclusion: In recent years, the management of IgE-mediated food allergy has greatly improved. Knowledge of pathogenetic mechanisms, understanding of the disease course, and the introduction of novel biomarkers led to more accurate diagnoses along with the active treatment of patients.

IgE-Mediated Fish Allergy in Children

Fish allergy constitutes a severe problem worldwide. Its prevalence has been calculated as high as 7% in paediatric populations, and in many cases, it persists into adulthood with life-threatening signs and symptoms. The following review focuses on the epidemiology of Immunoglobulin E (IgE)-mediated fish allergy, its pathogenesis, clinical manifestations, and a thorough approach to diagnosis and management in the paediatric population. The traditional approach for managing fish allergy is avoidance and rescue medication for accidental exposures. Food avoidance poses many obstacles and is not easily maintained. In the specific case of fish, food is also not the only source of allergens; aerosolisation of fish proteins when cooking is a common source of highly allergenic parvalbumin, and elimination diets cannot prevent these contacts. Novel management approaches based on immunomodulation are a promising strategy for the future of these patients.

IgE and IgG4 epitopes revealed on the major fish allergen Lat c 1

BACKGROUND

The IgE- and IgG₄-binding patterns of the major fish allergen parvalbumins are not clearly understood. IgE antibody-binding to parvalbumin from Asian seabass, Lat c 1.01, is implicated in up to 90 % of allergic reactions, although the region of IgE or IgG4 epitopes are unknown. In the present study, we characterized the specific IgE- and IgG₄-binding regions of Lat c 1.01 using serum from pediatric and adult patients with clinically-confirmed fish allergy.

METHODS

A comparative investigation of patient IgE- and IgG₄-binding to recombinant Lat c 1.01 was performed by immunoblotting and indirect ELISA using serum from 15 children and eight adults with clinically confirmed IgE-mediated reactions to fish. The IgE- and IgG₄-binding regions of Lat c 1.01 were determined by inhibition ELISA using seven overlapping peptides spanning the entire 102 amino acid sequence. Elucidated IgE-binding regions were modelled and compared to known antibody-binding regions of parvalbumins from five other fish species.

RESULTS

Ninety five percent (22/23) patients demonstrated IgE-binding to rLat c 1.01, while fewer patients (10/15 children and 7/8 adults) demonstrated robust IgG₄ binding when determined by immunoblots. IgE-binding for both cohorts was significantly higher compared to IgG₄-binding by ELISA. All patients in this study presented individual IgE and IgG₄ epitope-recognition profiles. In addition to these patient-specific antibody binding sites, general IgE epitopes were also identified at the C- and N-terminal regions of this major fish allergen.

CONCLUSIONS AND CLINICAL RELEVANCE

Our findings demonstrate two specific IgE epitopes on parvalbumin from Asian seabass, while IgG₄ binding is much lower and patient specific. This study highlights the importance of advancement in epitope analysis regardless of the age group for diagnostics and immunotherapies for fish allergy.

Past, present, and future of allergen immunotherapy vaccines

Allergen-specific immunotherapy (AIT) is an allergen-specific form of treatment for patients suffering from immunoglobulin E (IgE)-associated allergy; the most common and important immunologically mediated hypersensitivity disease. AIT is based on the administration of the disease-causing allergen with the goal to induce a protective immunity consisting of allergen-specific blocking IgG antibodies and alterations of the cellular immune response so that the patient can tolerate allergen contact. Major advantages of AIT over all other existing treatments for allergy are that AIT induces a long-lasting protection and prevents the progression of disease to severe manifestations. AIT is cost effective because it uses the patient´s own immune system for protection and potentially can be used as a preventive treatment. However, broad application of AIT is limited by mainly technical issues such as the quality of allergen preparations and the risk of inducing side effects which results in extremely cumbersome treatment schedules reducing patient´s compliance. In this article we review progress in AIT made from its beginning and provide an overview of the state of the art, the needs for further development, and possible technical solutions available through molecular allergology. Finally, we consider visions for AIT development towards prophylactic application.

Perspectives in Allergen-Specific Immunotherapy: Molecular Evolution of Peptide- and Protein-Based Strategies

Allergen-specific Immunotherapy (AIT), through repetitive subcutaneous or sublingual administrations of allergen extracts, represents up to now the unique treatment against allergic sensitizations. However, the clinical efficacy of AIT can be largely dependent on the quality of natural allergen extracts. Moreover, the long duration and adverse side effects associated with AIT negatively impact patient adherence. Tremendous progress in the field of molecular allergology has made possible the design of safer, shorter and more effective new immunotherapeutic approaches based on purified and characterized natural or recombinant allergen derivatives and peptides. This review will summarize the characteristics of these different innovative vaccines including their effects in preclinical studies and clinical trials.

[Recombinant allergens, peptides, and virus-like particles for allergy immunotherapy]

Currently, extract-based therapeutic allergens from natural allergen sources (e.g., house dust mites, tree and grass pollen) are used for allergen-specific immunotherapy (AIT), the only causative therapy that can exhibit positive disease-modifying effects by tolerance induction and prevention of disease progression. Due to variations in the natural composition of the starting materials and different manufacturing processes, there are variations in protein content, allergen composition, and allergenic activity of similar products, which poses specific challenges for their standardization. The identification of the nucleotide sequences of allergenic proteins led to the development of molecular AIT approaches. This allows for the application of exclusively relevant structures as chemically synthesized peptides, recombinant single allergens, or molecules with hypoallergenic properties that potentially allow for an up-dosing with higher allergen-doses without allergic side effects leading more quickly to effective cumulative doses. Further modifications of AIT preparations to improve allergenic and immunogenic properties may be achieved, e.g., by including the use of virus-like particles (VLPs). To date, the herein described therapeutic approaches have been tested in clinical trials only. This article provides an overview of published molecular approaches for allergy treatment used in clinical AIT studies. Their added value and challenges compared to established therapeutic allergens are discussed. The aim of these approaches is to develop highly effective and well-tolerated AIT preparations with improved patient acceptance and adherence.

Recombinant allergens for immunotherapy: state of the art

PURPOSE OF REVIEW

More than 30 years ago, the first molecular structures of allergens were elucidated and defined recombinant allergens became available. We review the state of the art regarding molecular AIT with the goal to understand why progress in this field has been slow, although there is huge potential for treatment and allergen-specific prevention.

RECENT FINDINGS

On the basis of allergen structures, several AIT strategies have been developed and were advanced into clinical evaluation. In clinical AIT trials, promising results were obtained with recombinant and synthetic allergen derivatives inducing allergen-specific IgG antibodies, which interfered with allergen recognition by IgE whereas clinical efficacy could not yet be demonstrated for approaches targeting only allergen-specific T-cell responses. Available data suggest that molecular AIT strategies have many advantages over allergen extract-based AIT.

SUMMARY

Clinical studies indicate that recombinant allergen-based AIT vaccines, which are superior to existing allergen extract-based AIT can be developed for respiratory, food and venom allergy. Allergen-specific preventive strategies based on recombinant allergen-based vaccine approaches and induction of T-cell tolerance are on the horizon and hold promise that allergy can be prevented. However, progress is limited by lack of resources needed for clinical studies, which are necessary for the development of these innovative strategies.

Production of allergen-specific immunotherapeutic agents for the treatment of food allergy

Allergen-specific immunotherapy (IT) is emerging as a viable avenue for the treatment of food allergies. Clinical trials currently investigate raw or slightly processed foods as therapeutic agents, as trials using food-grade agents can be performed without the strict regulations to which conventional drugs are subjected. However, this limits the ability of standardization and may affect clinical trial outcomes and reproducibility. Herein, we provide an overview of methods used in the production of immunotherapeutic agents for the treatment of food allergies, including processed foods, allergen extracts, recombinant allergens, and synthetic peptides, as well as the physical and chemical processes for the reduction of protein allergenicity. Commercial interests currently favor producing standardized drug-grade allergen extracts for therapeutic use, and clinical trials are ongoing. In the near future, recombinant production could replace purification strategies since it allows the manufacturing of pure, native allergens or sequence-modified allergens with reduced allergenicity. A recurring issue within this field is the inadequate reporting of production procedures, quality control, product physicochemical characteristics, allergenicity, and immunological properties. This information is of vital importance in assessing therapeutic standardization and clinical safety profile, which are central parameters for the development of future therapeutic agents.

Can food allergy be cured? What are the future prospects?

Food allergies have become a significant heath burden as prevalence continues to rise, affecting 6%-13% of the global population. In the absence of drugs approved by regulatory agencies, the current standard of care remains avoidance of allergenic foods and management of acute allergic reactions with antihistamines and epinephrine autoinjectors. Allergen immunotherapy has been shown to increase the threshold of reactivity in the majority of food-allergic individuals. However, challenges include long treatment periods, high rates of adverse reactions, and lack of permanence of desensitization and established protocols. To address these limitations, adjunctive allergen-specific immunotherapy, vaccines, and non-allergen-specific therapies (eg, monoclonal antibodies) are being explored. The future of food allergy treatment is promising with a number of clinical trials in progress. Currently, although desensitization can be achieved for the majority of individuals with food allergy through immunotherapy, continued ingestion of allergen is needed for most individuals to maintain desensitization. Further understanding of the mechanisms of food allergy and identification of biomarkers to distinguish between temporary and permanent resolution of allergies is needed before a cure, where reactivity to the allergen is permanently lost enabling the individual to consume the allergen in any amount at any time, can be envisioned.

Identification and characterization of parvalbumin-like protein in Trichophyton violaceum

Parvalbumins play crucial physiological roles in neuromuscular systems of vertebrates, such as cell-cycle, development of neurons, contraction of muscles, and regulation of intracellular calcium. To perform these neuromuscular functions, parvalbumin may be in associated with other proteins including calbindin, carbonic anhydrase, and cytochrome oxidase. Humans may show an IgE-specific hypersensitivity to parvalbumins after consumption of some distinct fish species. While this protein is abundant in fish muscles, literature review of publications related to fish parvalbumins, do not point to the presence of parvalbumins in eukaryotic microbes. In this study, we propose that distantly related parvalbumins may be found in some non-fish species. Bioinformatics studies such as multiple sequence alignment (MSA), phylogenetic analysis as well as molecular-based experiments indicate that, at least two parvalbumins sequences (UniProt IDs: A0A178F775 and A0A178F7E4) with EF-hand domains and Ca²⁺-binding sites could be identified in Trichophyton violaceum, a pathogenic fungal species. It was determined that both genes consisted of a single exon and encoded for parvalbumin proteins possessing conserved amino acid motifs. Antigenicity prediction revealed antigenic sites located in both sides of the Ca²⁺-binding site of the first EF-hand domain. Our phylogenetic analysis revealed that one of parvalbumins (UniProt ID: 0A178F775) can be evolved to other parvalbumins in T. violaceum (UniProt ID: A0A178F7E4) and fish species through evolutionary phenomenon. To confirm our in-silico findings, we designed three primer pairs to detect one of the T. violaceum parvalbumins (UniProt ID: A0A178F7E4) by polymerase chain reaction (PCR); one primer pair showed a strong and specific band in agarose gel electrophoresis. To evaluate the specificity of the method, the primers were tested on extracted DNA from Trichophyton rubrum and T. mentagrophytes. The results demonstrated that the evaluated parvalbumin gene (UniProt ID: A0A178F7E4) was T. violaceum-specific and this pathogenic fungus can be differentiated from T. rubrum and T. mentagrophytes through identification of parvalbumin genes. Further studies are necessary to unravel the biochemical and physiological functions of parvalbumins in T. violaceum.

Resistance of parvalbumin to gastrointestinal digestion is required for profound and long-lasting prophylactic oral tolerance

Background

Early introduction of food allergens into children's diet is considered as a strategy for the prevention of food allergy. The major fish allergen parvalbumin exhibits high stability against gastrointestinal digestion. We investigated whether resistance of carp parvalbumin to digestion affects oral tolerance induction.

Methods

Natural Cyp c 1, nCyp c 1, and a gastrointestinal digestion‐sensitive recombinant Cyp c 1 mutant, mCyp c 1, were analyzed for their ability to induce oral tolerance in a murine model. Both antigens were compared by gel filtration, circular dichroism measurement, in vitro digestion, and splenocyte proliferation assays using synthetic Cyp c 1‐derived peptides. BALB/c mice were fed once with high doses of nCyp c 1 or mCyp c 1, before sensitization to nCyp c 1. Immunological tolerance was studied by measuring Cyp c 1‐specific antibodies and cellular responses by ELISA, basophil activation, splenocyte proliferations, and intragastric allergen challenge.

Results

Wild‐type and mCyp c 1 showed the same physicochemical properties and shared the same major T‐cell epitope. However, mCyp c 1 was more sensitive to enzymatic digestion in vitro than nCyp c 1. A single high‐dose oral administration of nCyp c 1 but not of mCyp c 1 induced long‐term oral tolerance, characterized by lack of parvalbumin‐specific antibody and cellular responses. Moreover, mCyp c 1‐fed mice, but not nCyp c 1‐fed mice developed allergic symptoms upon challenge with nCyp c 1.

Conclusion

Sensitivity to digestion in the gastrointestinal tract influences the capacity of an allergen to induce prophylactic oral tolerance.

Fish Allergy Management: From Component-Resolved Diagnosis to Unmet Diagnostic Needs

Purpose of review

Fish is a common elicitor of IgE-mediated food allergy. Fish includes a large variety of foods, in terms of species and food processing, with marked distinction in local diets around the globe. Fish-allergic patients present with phenotypic diversity and major differences in levels of clinical cross-reactivity, features that pose an important challenge for the clinical diagnosis and management.

Recent findings

Parvalbumin is the major fish allergen. However, a single molecule is not sufficient but several homologs, allergens different from parvalbumin and allergen extracts, are needed for IgE-based diagnosis.

Summary

Parvalbumin-specific IgE are markers for clinical cross-reactions. Added value is provided by IgE typing to parvalbumin homologs from distantly related fish. IgE co-sensitization profiles (parvalbumin, enolase, aldolase) are referred as severity markers. The allergen panel seems to be not yet complete why fish extracts still play a crucial role in serum IgE analysis. Further clinical validation of a multiplex approach in molecular fish allergy diagnosis is needed for striving to avoid unnecessary food restrictions and in a further sense, improved patient care.

Rational Design, Structure-Activity Relationship, and Immunogenicity of Hypoallergenic Pru p 3 Variants

SCOPE

Allergies to lipid transfer proteins involve severe adverse reactions; thus, effective and sustainable therapies are desired. Previous attempts disrupting disulfide bonds failed to maintain immunogenicity; thus, the aim is to design novel hypoallergenic Pru p 3 variants and evaluate the applicability for treatment of peach allergy.

METHODS AND RESULTS

Pru p 3 proline variant (PV) designed using in silico mutagenesis, cysteine variant (CV), and wild-type Pru p 3 (WT) are purified from Escherichia coli. Variants display homogenous and stable protein conformations with an altered secondary structure in circular dichroism. PV shows enhanced long-term storage capacities compared to CV similar to the highly stable WT. Using sera of 33 peach allergic patients, IgE-binding activity is reduced by 97% (PV) and 71% (CV) compared to WT. Both molecules show strong hypoallergenicity in Pru p 3 ImmunoCAP cross-inhibition and histamine release assays. Immunogenicity of PV is demonstrated with a phosphate-based adjuvant formulation in a mouse model.

CONCLUSIONS

An in silico approach is used to generate a PV without targeting disulfide bonds, T cell epitopes, or previously reported IgE epitopes of Pru p 3. PV is strongly hypoallergenic while structurally stable and immunogenic, thus representing a promising candidate for peach allergen immunotherapy.

Molecular Approaches for Diagnosis, Therapy and Prevention of Cow´s Milk Allergy

Cow´s milk is one of the most important and basic nutrients introduced early in life in our diet but can induce IgE-associated allergy. IgE-associated allergy to cow´s milk can cause severe allergic manifestations in the gut, skin and even in the respiratory tract and may lead to life-threatening anaphylactic shock due to the stability of certain cow´s milk allergens. Here, we provide an overview about the allergen molecules in cow´s milk and the advantages of the molecular diagnosis of IgE sensitization to cow´s milk by serology. In addition, we review current strategies for prevention and treatment of cow´s milk allergy and discuss how they could be improved in the future by innovative molecular approaches that are based on defined recombinant allergens, recombinant hypoallergenic allergen derivatives and synthetic peptides.

Ca2+-Binding Proteins of the EF-Hand Superfamily: Diagnostic and Prognostic Biomarkers and Novel Therapeutic Targets

A multitude of Ca²⁺-sensor proteins containing the specific Ca²⁺-binding motif (helix-loop-helix, called EF-hand) are of major clinical relevance in a many human diseases. Measurements of troponin, the first intracellular Ca-sensor protein to be discovered, is nowadays the "gold standard" in the diagnosis of patients with acute coronary syndrome (ACS). Mutations have been identified in calmodulin and linked to inherited ventricular tachycardia and in patients affected by severe cardiac arrhythmias. Parvalbumin, when introduced into the diseased heart by gene therapy to increase contraction and relaxation speed, is considered to be a novel therapeutic strategy to combat heart failure. S100 proteins, the largest subgroup with the EF-hand protein family, are closely associated with cardiovascular diseases, various types of cancer, inflammation, and autoimmune pathologies. The intention of this review is to summarize the clinical importance of this protein family and their use as biomarkers and potential drug targets, which could help to improve the diagnosis of human diseases and identification of more selective therapeutic interventions.

Hypoallergenic Proteins for the Treatment of Food Allergy

PURPOSE OF REVIEW

Food allergy is a growing health problem worldwide that impacts millions of individuals. Current treatment options are limited and strict dietary avoidance remains the standard of care. Immunotherapy using whole, native allergens is under active clinical investigation but harbors the risk of severe side effects including anaphylaxis. Newer food-specific therapies with hypoallergenic proteins may potentially offer safer treatment alternatives, and this review seeks to investigate the evidence supporting the use of these modalities.

RECENT FINDINGS

The utilization of different methods to alter allergen structure and IgE binding leads to reduced allergenicity and decreases the risk for systemic reactions, making the use of potential therapies including extensively heated egg/milk, peptide immunotherapy, recombinant allergen immunotherapy, and DNA vaccines safe and possibly efficacious forms of treatment in food allergy. However, for the majority of these treatment modalities, limited data currently exists looking at the safety and efficacy in human subjects with food allergy. This review provides a comprehensive overview of the current evidence examining the safety and efficacy of hypoallergenic proteins in the treatment of food allergies.

Next-Generation Approaches for the Treatment of Food Allergy

PURPOSE OF REVIEW

IgE-mediated food allergies are an increasing health concern, and current management includes food avoidance and use of emergency medications. Effective treatment of food allergy is highly desirable. Next generation approaches for the treatment of food allergy aim to improve both safety and efficacy, potentially including long-term tolerance.

RECENT FINDINGS

Oral immunotherapy (OIT) and epicutaneous immunotherapy (EPIT) will likely be integrated into clinical practice as part of food allergy management in the near future. Newer approaches, such as sublingual immunotherapy (SLIT), modified proteins, lysosomal-associated membrane protein DNA (LAMP DNA) vaccines, and the use of immunomodulatory agents, are early in development and depending on results, could also become important treatment options. This is a review of novel approaches to the treatment of food allergy that are currently under investigation, including the use of SLIT, modified proteins, probiotics, Chinese herbal supplements, biologic therapies, and DNA vaccines, as well as a summary of the current status of OIT and EPIT.

Allergen immunotherapy for food allergy from the Asian perspective: key challenges and opportunities

Introduction: Prevalence of food allergy is rising in different regions of the world. Asia has not been spared from this epidemic, but epidemiological data have revealed a different pattern of food allergens in this continent. Allergen-specific immunotherapy (AIT) for food allergy, which has been revolutionary as the main focus of research in recent years, needs to be adapted for the different populations in Asia. Areas covered: Recent evidence shows increasing popularity and superiority of AIT over strict food avoidance as the cornerstone of food allergy management. Asia is a distinctive continent with specific food allergy triggers, in particular, seafood, and wheat. Peanut, on the contrary, is not a common food allergen in most parts of Asia. The common Asian food allergens, as well as the rapidly developing food-specific AIT in this region will be covered in this article. Expert commentary: Evidence on oral immunotherapy for wheat allergy and preclinical data on shellfish AIT are promising. Further work should be done on resolving cross-sensitization between environmental allergens with wheat and shellfish allergens, and a modified AIT approach to enhance the safety and effectiveness of food-specific immunotherapy.

Allergen Extracts for In Vivo Diagnosis and Treatment of Allergy: Is There a Future?

Today, in vivo allergy diagnosis and allergen-specific immunotherapy (AIT) are still based on allergen extracts obtained from natural allergen sources. Several studies analyzing the composition of natural allergen extracts have shown severe problems regarding their quality such as the presence of undefined nonallergenic materials, contaminants as well as high variabilities regarding contents and biological activity of individual allergens. Despite the increasing availability of sophisticated analytical technologies, these problems cannot be overcome because they are inherent to allergen sources and methods of extract production. For in vitro allergy diagnosis problems related to natural allergen extracts have been largely overcome by the implementation of recombinant allergen molecules that are defined regarding purity and biological activity. However, no such advances have been made for allergen preparations to be used in vivo for diagnosis and therapy. No clinical studies have been performed for allergen extracts available for in vivo allergy diagnosis that document safety, sensitivity, and specificity of the products. Only for very few therapeutic allergen extracts state-of-the-art clinical studies have been performed that provide evidence for safety and efficacy. In this article, we discuss problems related to the inconsistent quality of products based on natural allergen extracts and share our observations that most of the products available for in vivo diagnosis and AIT do not meet the international standards for medicinal products. We argue that a replacement of natural allergen extracts by defined recombinantly produced allergen molecules and/or mixtures thereof may be the only way to guarantee the supply of clinicians with state-of-the-art medicinal products for in vivo diagnosis and treatment of allergic patients in the future.

Protease resistance of food proteins: a mixed picture for predicting allergenicity but a useful tool for assessing exposure

Background

Susceptibility to pepsin digestion of candidate transgene products is regarded an important parameter in the weight-of-evidence approach for allergenicity risk assessment of genetically modified crops. It has been argued that protocols used for this assessment should better reflect physiological conditions encountered in representative food consumption scenarios.

Aim

To evaluate whether inclusion of more physiological conditions, such as sub-optimal and lower pepsin concentrations, in combination with pancreatin digestion, improved the performance of digestibility protocols used in characterization of protein stability.

Methods

Four pairs of established allergens and their related non/weakly-allergenic counterparts (seed albumins, muscle tropomyosins, plant lipid transfer proteins [LTP] and collagens) plus fish parvalbumin, were subjected to nine combinations of pH (1.2-2.5-4.0) and pepsin-to-protein ratio (PPR: 10-1-0.1 U/µg) for pepsin digestion, followed by pancreatin digestion in the presence of bile salts. Digestion was monitored by SDS-PAGE in conjunction with Coomassie staining and immunoblotting using rabbit antisera and human IgE.

Results

At pH 4.0 and at PPR 0.1 most proteins, both allergen and non-allergen, were highly resistant to pepsin. Under conditions known to favor pepsin proteolysis, the established major allergens Ara h 2, Pru p 3 and Pen a 1 were highly resistant to proteolysis, while the allergen Cyp c 1 was not. However, this resistance to pepsin digestion only made Ara h 2 and to a lesser extent Pen a 1 and Pru p 3 stand out compared to their non-allergenic counterparts. Largely irrespective of preceding pepsin digestion conditions, pancreatin digestion was very effective for all tested proteins, allergens and non-allergens, except for Cyp c 1 and bovine collagen.

Conclusions

Sub-optimal pH, low pepsin-to protein ratio, and sequential pepsin and pancreatin digestion protocols do not improve the predictive value in distinguish allergens from non-allergens. Digestion conditions facilitating such distinction differ per protein pair.

New approaches to allergen immunotherapy

OBJECTIVE

New insights into mechanisms should enable strategic improvement of allergen immunotherapy, aiming to make it safer, faster, more effective, and able to induce long-term tolerance. We review novel approaches with potential to translate into clinical use.

DATA SOURCES

Database searches were conducted in PubMed, Scopus, and Google Scholar.

STUDY SELECTIONS

Search terms were based on current and novel approaches in immunotherapy. Literature was selected primarily from recent randomized double-blinded placebo-controlled trials and meta-analyses.

RESULTS

Alum, microcrystalline tyrosine, and calcium phosphate are adjuvants in current use. Toll-like receptor-4 agonists combined with allergen have potential to shorten duration of treatment. Other novel adjuvants, nanoparticles, and virus-like particles in combination with allergen have shown early promise. Omalizumab lessens systemic side effects but does not improve efficacy. Intralymphatic immunotherapy for aeroallergens, epicutaneous immunotherapy for food allergens, and use of modified allergens (allergoids), recombinant allergens (and hypoallergenic variants), and T- and B-cell peptide approaches have shown evidence of efficacy and permitted shortened courses but have only rarely been compared with conventional extracts.

CONCLUSION

Novel routes of immunotherapy, use of modified allergens, and combination of allergens with immunostimulatory adjuvants or immune modifiers have been developed to augment downregulation of T-helper cell type 2 immunity and/or induce "protective" blocking antibodies. Although these strategies have permitted shortened courses, confirmatory phase 3 trials are required to confirm efficacy and safety and head-to-head trials are required for comparative efficacy. Currently, subcutaneous and sublingual immunotherapies using in-house standardized crude extracts remain the only approaches proved to induce long-term tolerance.

The future outlook on allergen immunotherapy in children: 2018 and beyond

Allergen immunotherapy (AIT) is the only currently available immune-modifying and aetiological treatment for patients suffering from IgE-mediated diseases. In childhood, it represents a suitable therapeutic option to intervene during the early phases of respiratory allergic diseases such as rhino-conjunctivitis and asthma, which is when their progression may be more easily influenced. A growing body of evidence shows that oral immunotherapy represents a promising treatment option in children with persistent IgE- mediated food allergy. The efficacy of AIT is under investigation also in patients with extrinsic atopic dermatitis, currently with controversial results. Furthermore, AIT might be a strategy to prevent the development of a new sensitization or of a (new) allergic disease. However, there are still some methodological criticisms, such as: a) the regimen of administration and the amount of the maintenance dose are both largely variable; b) the protocols of administration are not standardized; c) the description and classification of side effects is variable among studies and needs to be standardized; d) quality of life and evaluation of health economics are overall missing. All these aspects make difficult to compare each study with another. In addition, the content of major allergen(s) remains largely variable among manufacturers and the availability of AIT products differences among countries. The interest and the attention to AIT treatment are currently fervent and increasing. Well-designed studies are awaited in the near future in order to overcome the current gaps in the evidence and furtherly promote implementation strategies.

Next-Generation of Allergen-Specific Immunotherapies: Molecular Approaches

PURPOSE OF REVIEW

The aim of this article is to discuss how allergen-specific immunotherapy (AIT) can be improved through molecular approaches. We provide a summary of next-generation molecular AIT approaches and of their clinical evaluation. Furthermore, we discuss the potential of next generation molecular AIT forms for the treatment of severe manifestations of allergy and mention possible future molecular strategies for the secondary and primary prevention of allergy.

RECENT FINDINGS

AIT has important advantages over symptomatic forms of allergy treatment but its further development is limited by the quality of the therapeutic antigen preparations which are derived from natural allergen sources. The field of allergy diagnosis is currently undergoing a dramatic improvement through the use of molecular testing with defined, mainly recombinant allergens which allows high-resolution diagnosis. Several studies demonstrate that molecular testing in early childhood can predict the development of symptomatic allergy later on in life. Clinical studies indicate that molecular AIT approaches have the potential to improve therapy of allergic diseases and may be used as allergen-specific forms of secondary and eventually primary prevention for allergy.

Seafood allergy: A comprehensive review of fish and shellfish allergens

Seafood refers to several distinct groups of edible aquatic animals including fish, crustacean, and mollusc. The two invertebrate groups of crustacean and mollusc are, for culinary reasons, often combined as shellfish but belong to two very different phyla. The evolutionary and taxonomic diversity of the various consumed seafood species poses a challenge in the identification and characterisation of the major and minor allergens critical for reliable diagnostics and therapeutic treatments. Many allergenic proteins are very different between these groups; however, some pan-allergens, including parvalbumin, tropomyosin and arginine kinase, seem to induce immunological and clinical cross-reactivity. This extensive review details the advances in the bio-molecular characterisation of 20 allergenic proteins within the three distinct seafood groups; fish, crustacean and molluscs. Furthermore, the structural and biochemical properties of the major allergens are described to highlight the immunological and subsequent clinical cross-reactivities. A comprehensive list of purified and recombinant allergens is provided, and the applications of component-resolved diagnostics and current therapeutic developments are discussed.

EAACI Guidelines on allergen immunotherapy: IgE-mediated food allergy

Food allergy can result in considerable morbidity, impairment of quality of life, and healthcare expenditure. There is therefore interest in novel strategies for its treatment, particularly food allergen immunotherapy (FA-AIT) through the oral (OIT), sublingual (SLIT), or epicutaneous (EPIT) routes. This Guideline, prepared by the European Academy of Allergy and Clinical Immunology (EAACI) Task Force on Allergen Immunotherapy for IgE-mediated Food Allergy, aims to provide evidence-based recommendations for active treatment of IgE-mediated food allergy with FA-AIT. Immunotherapy relies on the delivery of gradually increasing doses of specific allergen to increase the threshold of reaction while on therapy (also known as desensitization) and ultimately to achieve post-discontinuation effectiveness (also known as tolerance or sustained unresponsiveness). Oral FA-AIT has most frequently been assessed: here, the allergen is either immediately swallowed (OIT) or held under the tongue for a period of time (SLIT). Overall, trials have found substantial benefit for patients undergoing either OIT or SLIT with respect to efficacy during treatment, particularly for cow's milk, hen's egg, and peanut allergies. A benefit post-discontinuation is also suggested, but not confirmed. Adverse events during FA-AIT have been frequently reported, but few subjects discontinue FA-AIT as a result of these. Taking into account the current evidence, FA-AIT should only be performed in research centers or in clinical centers with an extensive experience in FA-AIT. Patients and their families should be provided with information about the use of FA-AIT for IgE-mediated food allergy to allow them to make an informed decision about the therapy.