Food Allergens of Plant and Animal Origin: Classification, Characteristics, and Properties

Food allergy is an adverse immune response to specific foods that can be either IgE-mediated or non-IgE mediated. The causes of IgE-mediated food allergy are multifactorial and involve genetic, dietary, and environmental factors. The prevalence of food allergy has increased over the last few decades, especially in urbanized, industrialized, and Westernized countries, and the epithelial barrier hypothesis has been recently suggested as a possible explanation for this increase. Food allergens of plant and animal origin are classified into a few families and superfamilies that are widely distributed and conserved. While it is known that food allergens share common properties, such as stability to enzymes and solubility, they also exhibit differential properties, and exceptions to the common characteristics exist. In recent years, novel characteristics of food allergens have been proposed based on their immunological properties and their ability to act as adjuvants or enhancers of the immune system.This chapter provides an overview of the current knowledge of food allergy, covering their prevalence, classification of food allergens from plant and animal origins, and recent advancements in the characterization of the properties of these allergens.

Preclinical Pharmacokinetic Study on Caffeine as an Excipient for Monoclonal Antibody Formulations

Caffeine is a novel excipient that effectively reduces viscosity of high concentration mAb formulations intended for subcutaneous (SQ) delivery. Two preclinical studies were conducted in rats to evaluate pharmacokinetic (PK) parameters of caffeine as well as its effects on the PK profile of a model mAb, namely ipilimumab. Results show that SQ absorption and elimination of caffeine was rapid, with the average Tmax of 0.4 h and T1/2 of 1.6 h, administered with or without ipilimumab. Furthermore, caffeine did not affect ipilimumab SQ PK profiles. Independent of caffeine concentration, ipilimumab serum T1/2 was between 2 and 3 days, Tmax was between 3 and 4 days and SQ bioavailability was about 64%. In addition, SQ injection of caffeine at different dose levels showed no irritation at the injection site or adverse effects. Results from the current PK studies warrant further development of caffeine as a viscosity reducing excipient for mAb SQ formulations.

Perspectives of Proteomics in Respiratory Allergic Diseases

Proteomics in respiratory allergic diseases has such a battery of techniques and programs that one would almost think there is nothing impossible to find, invent or mold. All the resources that we document here are involved in solving problems in allergic diseases, both diagnostic and prognostic treatment, and immunotherapy development. The main perspectives, according to this version, are in three strands and/or a lockout immunological system: (1) Blocking the diapedesis of the cells involved, (2) Modifications and blocking of paratopes and epitopes being understood by modifications to antibodies, antagonisms, or blocking them, and (3) Blocking FcεRI high-affinity receptors to prevent specific IgEs from sticking to mast cells and basophils. These tools and targets in the allergic landscape are, in our view, the prospects in the field. However, there are still many allergens to identify, including some homologies between allergens and cross-reactions, through the identification of structures and epitopes. The current vision of using proteomics for this purpose remains a constant; this is also true for the basis of diagnostic and controlled systems for immunotherapy. Ours is an open proposal to use this vision for treatment.

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.

Dust Exposure and Respiratory Health Among Workers in Primary Coffee Processing Factories in Tanzania and Ethiopia

Introduction: In primary coffee factories the coffee beans are cleaned and sorted. Studies from the 80- and 90-ties indicated respiratory health effects among the workers, but these results may not represent the present status. Our aim was to review recent studies on dust exposure and respiratory health among coffee factory workers in Tanzania and Ethiopia, two major coffee producing countries in Africa.

Methods: This study merged data from cross-sectional studies from 2010 to 2019 in 4 and 12 factories in Tanzania and Ethiopia, respectively. Personal samples of “total” dust and endotoxin were taken in the breathing zone. Chronic respiratory symptoms were assessed using the American Thoracic Society (ATS) questionnaire. Lung function was measured by a spirometer in accordance with ATS guidelines.

Results: Dust exposure among male production workers was higher in Ethiopia (GM 12 mg/m³; range 1.1–81) than in Tanzania (2.5; 0.24–36). Exposure to endotoxins was high (3,500; 42–75,083) compared to the Dutch OEL of 90 EU/m³. The male workers had higher prevalence of respiratory symptoms than controls. The highest symptom prevalence and odds ratio were found for cough (48.4%; OR = 11.3), while for breathlessness and wheezing the odds ratios were 3.2 and 2.4, respectively. There was a significant difference between the male coffee workers and controls in the adjusted FEV1 (0.26 l/s) and FVC (0.21 l) and in the prevalence of airflow limitation (FEV1/FVC < 0.7) (6.3 vs. 0.9%). Among the male coffee workers, there was a significant association between cumulative dust exposure and the lung function variables FEV1 and FVC, respectively.

Conclusions: The results suggest that coffee production workers are at risk of developing chronic respiratory symptoms and reduced lung function, and that the findings are related to high dust levels. Measures to reduce dust exposure should be targeted to factors identified as significant determinants of exposure.

Occupational Respiratory Allergy: Risk Factors, Diagnosis, and Management

Occupational allergies are among the most common recorded occupational diseases. The skin and the upper and lower respiratory tract are the classical manifestation organs. More than 400 occupational agents are currently documented as being potential "respiratory sensitizers" and new reported causative agents are reported each year. These agents may induce occupational rhinitis (OR) or occupational asthma (OA) and can be divided into high-molecular weight (HMW) and low-molecular weight (LMW) agents. The most common occupational HMW agents are (glycol)proteins found in flour and grains, enzymes, laboratory animals, fish and seafood, molds, and Hevea brasiliensis latex. Typical LMW substances are isocyanates, metals, quaternary ammonium persulfate, acid anhydrides, and cleaning products/disinfectants. Diagnosis of occupational respiratory allergy is made by a combination of medical history, physical examination, positive methacholine challenge result or bronchodilator responsiveness, determination of IgE-mediated sensitization, and specific inhalation challenge tests as the gold standard. Accurate diagnosis of asthma is the first step to managing OA as shown above. Removal from the causative agent is of central importance for the management of OA. The best strategy to avoid OA is primary prevention, ideally by avoiding the use of and exposure to the sensitizer or substituting safer substances for these agents.

High-Resolution Mapping of Human Norovirus Antigens via Genomic Phage Display Library Selections and Deep Sequencing

Norovirus (NoV) infections are a leading cause of gastroenteritis. The humoral immune response plays an important role in the control of NoV, and recent studies have identified neutralizing antibodies that bind the capsid protein VP1 to block viral infection. Here, we utilize a NoV GI.1 Jun-Fos-assisted phage display library constructed from randomly fragmented genomic DNA coupled with affinity selection for antibody binding and subsequent deep sequencing to map epitopes. The epitopes were identified by quantitating the phage clones before and after affinity selection and aligning the sequences of the most enriched peptides. The HJT-R3-A9 single-chain variable fragment (scFv) antibody epitope was mapped to a 12-amino-acid region of VP1 that is also the binding site for several previously identified monoclonal antibodies. We synthesized the 12-mer peptide and found that it binds the scFv antibody with a K_D (equilibrium dissociation constant) of 46 nM. Further, alignment of enriched peptides after affinity selection on rabbit anti-NoV polyclonal antisera revealed five families of overlapping sequences that define distinct epitopes in VP1. One of these is identical to the HJT-R3-A9 scFv epitope, further suggesting that it is immunodominant. Similarly, other epitopes identified using the polyclonal antisera overlap binding sites for previously reported monoclonal antibodies, suggesting that they are also dominant epitopes. The results demonstrate that affinity selection and deep sequencing of the phage library provide sufficient resolution to map multiple epitopes simultaneously from complex samples such as polyclonal antisera. This approach can be extended to examine the antigenic landscape in patient sera to facilitate investigation of the immune response to NoV.IMPORTANCE NoV infections are a leading cause of gastroenteritis in the United States. Human NoVs exhibit extensive genetic and antigenic diversity, which makes it challenging to design a vaccine that provides broad protection against infection. Antibodies developed during the immune response play an important role in the control of NoV infections. Neutralizing antibodies that act by sterically blocking the site on the virus used to bind human cells have been identified. Identification of other antibody binding sites associated with virus neutralization is therefore of interest. Here, we use a high-resolution method to map multiple antibody binding sites simultaneously from complex serum samples. The results show that a relatively small number of sites on the virus bind a large number of independently generated antibodies, suggesting that immunodominance plays a role in the humoral immune response to NoV infections.

Mapping Protein-Protein Interaction Interface Peptides with Jun-Fos Assisted Phage Display and Deep Sequencing

Protein-protein interactions govern many cellular processes, and identifying binding interaction sites on proteins can facilitate the discovery of inhibitors to block such interactions. Here we identify peptides from a randomly fragmented plasmid encoding the β-lactamase inhibitory protein (BLIP) and the Lac repressor (LacI) that represent regions of protein-protein interactions. We utilized a Jun-Fos-assisted phage display system that has previously been used to screen cDNA and genomic libraries to identify antibody antigens. Affinity selection with polyclonal antibodies against LacI or BLIP resulted in the rapid enrichment of in-frame peptides from various regions of the proteins. Further, affinity selection with β-lactamase enriched peptides that encompass regions of BLIP previously shown to contribute strongly to the binding energy of the BLIP/β-lactamase interaction, i.e., hotspot residues. Further, one of the regions enriched by affinity selection encompassed a disulfide-constrained region of BLIP that forms part of the BLIP interaction surface in the native complex that we show also binds to β-lactamase as a disulfide-constrained macrocycle peptide with a K_D of ∼1 μM. Fragmented open reading frame (ORF) libraries may efficiently identify such naturally constrained peptides at protein-protein interaction interfaces. With sufficiently deep coverage of ORFs by peptide-coding inserts, phage display and deep sequencing can provide detailed information on the domains or peptides that contribute to an interaction. Such information should enable the design of potentially therapeutic macrocycles or peptidomimetics that block the interaction.

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

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

Chitinases as Food Allergens

Food allergies originate from adverse immune reactions to some food components. Ingestion of food allergens can cause effects of varying severity, from mild itching to severe anaphylaxis reactions. Currently there are no clues to predict the allergenic potency of a molecule, nor are cures for food allergies available. Cutting-edge research on allergens is aimed at increasing information on their diffusion and understanding structure-allergenicity relationships. In this context, purified recombinant allergens are valuable tools for advances in the diagnostic and immunotherapeutic fields. Chitinases are a group of allergens often found in plant fruits, but also identified in edible insects. They are classified into different families and classes for which structural analyses and identification of epitopes have been only partially carried out. Moreover, also their presence in common allergen databases is not complete. In this review we provide a summary of the identified food allergenic chitinases, their main structural characteristics, and a clear division in the different classes.

Allergen component analysis as a tool in the diagnosis and management of occupational allergy

We are now in the epoch of "molecular allergology" and numerous clinically relevant allergenic molecules are available improving the performance of in vitro allergen tests and allergen detection methods. This review is focusing on characterized occupational allergens and their implementation into the in vitro diagnosis for occupational allergy and in allergen detection methods. More than 400 occupational agents are identified and documented as being 'respiratory sensitizers', but currently only a limited number of them are characterized on the molecular level and available for routine diagnosis as native or recombinant allergens. One exception, however, is natural rubber latex (NRL) from Hevea brasiliensis still remaining an important occupational allergen source. Characterization of 15 NRL allergens led to the development of assays for the determination of allergen content of NRL materials and the implementation of component-resolved diagnosis (CRD) for specific IgE antibody measurement. Microarray or singleplex using recombinant or native allergens are reliable tools for NRL allergy diagnosis. In addition, NRL allergy is an excellent model for improving extract-based specific IgE measurement by amplification of NRL extract preparation with stable recombinant major allergen rHev b 5. Despite the many efforts to characterize the occupationally relevant wheat allergens for baker's asthma, the most frequently occurring forms of occupational asthma, the results are highly diverse. Wheat sensitization profiles of bakers showed great interindividual variability and no wheat allergen could be classified as the major allergen. For diagnosis of baker's asthma, a whole wheat extract is still the best option for specific IgE determination. But single wheat allergens might help to discriminate between wheat-induced food allergy, grass pollen allergy and baker's asthma. For workplace-related allergens like coffee, wood, soybean, seafood and moulds allergens are characterized and few of them are available, but their relevance for occupational sensitization routes should be verified in the further studies.

Plant food allergy: Influence of chemicals on plant allergens

Plant-derived foods are the most common allergenic sources in adulthood. Owing to the rapidly increasing prevalence of plant food allergies in industrialized countries, the environmental factors are suspected to play a key role in development of allergic sensitization. The present article provides an overview of ways by which chemicals may influence the development and severity of allergic reactions to plant foods, with especial focus on plant allergens up-regulated under chemical stress. In plants, a substantial part of allergens have defense-related function and their expression is highly influenced by environmental stress and diseases. Pathogenesis-related proteins (PR) account for about 25% of plant food allergens and some are responsible for extensive cross-reactions between plant-derived foods, pollen and latex allergens. Chemicals released by anthropogenic sources such as agriculture, industrial activities and traffic-related air pollutants are potential drivers of the increasing sensitization to allergenic PRs by elevating their expression and by altering their immunogenicity through post-translational modifications. In addition, some orally-taken chemicals may act as immune adjuvants or directly trigger non-IgE mediated food allergy. Taken together, the current literature provides an overwhelming body of evidence supporting the fact that plant chemical exposure and chemicals in diet may enhance the allergenic properties of certain plant-derived foods.

Addressing Molecular Diagnosis of Occupational Allergies

PURPOSE OF REVIEW

Numerous clinically relevant allergenic molecules enhance the performance of specific (s) IgE tests and improve the specificity of allergy diagnosis. This review aimed to summarize our current knowledge of the high-molecular-weight allergens involved in the development of occupational asthma and rhinitis and to critically analyze the contribution of component-resolved diagnosis in the management of these conditions.

RECENT FINDINGS

There is a lack of standardization and validation for most available extracts of occupational agents, and assessment of sIgE reactivity to occupational allergen components has been poorly investigated, with the notable exception of natural rubber latex (NRL) and wheat flour. In the case of NRL, the application of recombinant single allergens and amplification of natural extracts with stable recombinant allergens improved the test sensitivity. IgE-sensitization profile in patients with baker's asthma showed great interindividual variation, and extract-based diagnostic is still recommended. For other occupational allergens, it remains necessary to evaluate the relevance of single allergen molecules for the sensitization induced by occupational exposure. Progress has been made to characterize occupational allergens especially NRL and wheat, although there is still an unmet need to increase the knowledge of occupational allergens, to include standardized tools into routine diagnostic, and to evaluate their usefulness in clinical practice.

Endotoxin, dust and exhaled nitrogen oxide among hand pickers of coffee; a cross-sectional study

BACKGROUND

Primary coffee processing takes place in countries where coffee is grown, and may include hand picking of coffee to remove low quality beans. Hand picking is mostly performed by women. No previous studies on dust and respiratory health have been performed in this occupational group, although studies indicate respiratory problems among other coffee production workers.

FINDINGS

Our aim was to assess dust and endotoxin exposure among hand pickers in a coffee factory and compare the levels with limit values. In addition we wanted to examine the fraction of exhaled nitric oxide (FeNO) as a possible inflammatory marker in the airways among the hand pickers and evaluate the association between FeNO and years of hand picking. All hand pickers in a factory were examined during 1 week. The response was 100 %; 69 participated. FeNO was measured using an electrochemistry-based NIOX MINO device. Nine out of 69 workers (13 %) had levels of FeNO above 25 ppb, indicating presence of respiratory inflammation. A significant positive association was found between increasing FeNO and years of hand picking. Nine personal samples of total dust and endotoxin were taken. None of the dust samples exceeded the occupational limit value for total organic dust of 5 mg/m(3). Three samples of endotoxin (33 %) were above the recommended value of 90 EU/m(3).

CONCLUSIONS

Levels of endotoxin were higher than recommended standards among hand pickers, and there was a positive association between the level of exhaled nitrogen oxide and years of work with hand picking coffee.

Identification of two metallothioneins as novel inhalative coffee allergens cof a 2 and cof a 3

Background

Dust of green coffee beans is known to be a relevant cause for occupational allergic disorders in coffee industry workers. Recently, we described the first coffee allergen (Cof a 1) establishing an allergenic potential of green coffee dust.

Objective

Our aim was to identify allergenic components of green coffee in order to enhance inhalative coffee allergy diagnosis.

Methods

A Coffea arabica pJuFo cDNA phage display library was created and screened for IgE binding with sera from allergic coffee workers. Two further coffee allergens were identified by sequence analysis, expressed in E. coli, and evaluated by Western blots. The prevalence of sensitization to recombinant Cof a 1, Cof a 2, and Cof a 3 and to commercially available extract was investigated by ELISA (enzyme-linked immunosorbent assay) respectively CAP (capacity test) screening in 18 sera of symptomatic coffee workers.

Results

In addition to the previously described chitinase Cof a 1, two Coffea arabica cysteine-rich metallothioneins of 9 and 7 kDa were identified and included in the IUIS Allergen Nomenclature as Cof a 2 and Cof a 3. Serum IgE antibodies to at least one of the recombinant allergens were found in 8 out of 18 symptomatic coffee workers (44%). Only 2 of the analysed sera (11%) had reacted previously to the commercial allergy test.

Conclusions

In addition to the previously described Cof a 1 we have identified two further coffee proteins to be type I coffee allergens (Cof a 2 and Cof a 3) which may have a relevant potential for the specific diagnosis and/or therapy of coffee allergy.

Overview of plant chitinases identified as food allergens

Food allergies are induced by proteins belonging to a limited number of families. Unfortunately, relationships between protein structure and capacity to induce the immune response have not been completely clarified yet, which precludes possible improvements in the diagnosis, prevention, and therapy of allergies. Plant chitinases constitute a good example of food allergenic proteins for which structural analysis of allergenicity has only been carried out partially. In plants, there are at least five structural classes of chitinases plus a number of chitinase-related polypeptides. Their allergenicity has been mostly investigated for chitinases of class I, due to both their higher prevalence among plant chitinases and by the high structural similarity between their substrate-binding domain and hevein, a well-known allergen present in the latex of rubber trees. Even if allergenic molecules have been identified for at least three other classes of plant chitinases, the involvement of the different structural motifs in the allergenicity of molecules has been disregarded so far. In this review, we provide a structurally based catalog of plant chitinases investigated for allergenicity, which could be a useful base for further studies aimed at better clarifying the structure-allergenicity relationships for this protein family.

Current overview of allergens of plant pathogenesis related protein families

Pathogenesis related (PR) proteins are one of the major sources of plant derived allergens. These proteins are induced by the plants as a defense response system in stress conditions like microbial and insect infections, wounding, exposure to harsh chemicals, and atmospheric conditions. However, some plant tissues that are more exposed to environmental conditions like UV irradiation and insect or fungal attacks express these proteins constitutively. These proteins are mostly resistant to proteases and most of them show considerable stability at low pH. Many of these plant pathogenesis related proteins are found to act as food allergens, latex allergens, and pollen allergens. Proteins having similar amino acid sequences among the members of PR proteins may be responsible for cross-reactivity among allergens from diverse plants. This review analyzes the different pathogenesis related protein families that have been reported as allergens. Proteins of these families have been characterized in regard to their biological functions, amino acid sequence, and cross-reactivity. The three-dimensional structures of some of these allergens have also been evaluated to elucidate the antigenic determinants of these molecules and to explain the cross-reactivity among the various allergens.