Identification of a novel allergen from muscle and various organs in banana shrimp (Fenneropenaeus merguiensis)

The Allergen Profile of Two Edible Insect Species-Acheta domesticus and Hermetia illucens

SCOPE

Edible insect proteins are increasingly introduced as an alternative sustainable food source to address the world's need to feed the growing population. Tropomyosin is the main insect allergen; however, additional potential allergens are not well characterized and the impact of extraction procedures on immunological reactivity is unknown.

METHODS AND RESULTS

Proteins from different commercial food products derived from cricket (Acheta domesticus) and black soldier fly (BSF) (Hermetia illucens) are extracted using five different extraction buffers. The proteins are analyzed by SDS-PAGE and immunoblotting using allergen-specific antibodies and crustacean allergic patient sera. IgE binding bands are analyzed by mass spectrometry as well as the complete allergen profile of all 30 extracts. Urea-based buffers are most efficient in extracting insect allergens. Shrimp-specific antibody cross-reactivity to tropomyosin from cricket and BSF indicates high sequence and structural similarity between shrimp and insects. Additional unique allergens are identified in both species, including hemocyanin, vitellogenin, HSP20, apolipophorin-III, and chitin-binding protein.

CONCLUSIONS

Identifying potential allergenic proteins and their isoforms in cricket and BSF requires specific extraction approaches using urea-based methods. While tropomyosin is the most abundant and immunoreactive allergen, seven unique allergens are identified, highlighting the need for insect species-specific allergen detection in food products.

In silico evaluation of the potential allergenicity of a fungal biomass from Rhizomucor pusillus for use as a novel food ingredient

The world's hunger for novel food ingredients drives the development of safe, sustainable, and nutritious novel food products. For foods containing novel proteins, potential allergenicity of the proteins is a key safety consideration. One such product is a fungal biomass obtained from the fermentation of Rhizomucor pusillus. The annotated whole genome sequence of this strain was subjected to sequence homology searches against the AllergenOnline database (sliding 80-amino acid windows and full sequence searches). In a stepwise manner, proteins were designated as potentially allergenic and were further compared to proteins from commonly consumed foods and from humans. From the sliding 80-mer searches, 356 proteins met the conservative >35% Codex Alimentarius threshold, 72 of which shared ≥50% identity over the full sequence. Although matches were identified between R. pusillus proteins and proteins from allergenic food sources, the matches were limited to minor allergens from these sources, and they shared a greater degree of sequence homology with those from commonly consumed foods and human proteins. Based on the in silico analysis and a literature review for the source organism, the risk of allergenic cross-reactivity of R. pusillus is low.

A comprehensive review on hemocyanin from marine products: Structure, functions, its implications for the food industry and beyond

Hemocyanin, an oxygen-transport protein, is widely distributed in the hemolymph of marine arthropods and mollusks, playing an important role in their physiological processes. Recently, hemocyanin has been recognized as a multifunctional glycoprotein involved in the immunological responses of aquatic invertebrates. Consequently, the link between hemocyanin functions and their potential applications has garnered increased attention. This review offers an integrated overview of hemocyanin's structure, physicochemical characteristics, and bioactivities to further promote the utilization of hemocyanin derived from marine products. Specifically, we review its implication in two aspects of food and aquaculture industries: quality and health. Hemocyanin's inducible phenoloxidase activity is thought to be an inducer of melanosis in crustaceans. New anti-melanosis agents targeted to hemocyanin need to be explored. The red-color change observed in shrimp shells is related to hemocyanin, affecting consumer preferences. Hemocyanin's adaptive modification in response to the aquatic environment is available as a biomarker. Additionally, hemocyanin is endowed with bioactivities encompassing anti-microbial, antiviral, and therapeutic activities. Hemocyanin is also a novel allergen and its allergenic features remain incompletely characterized.

Animal-derived food allergen: A review on the available crystal structure and new insights into structural epitope

Immunoglobulin E (IgE)-mediated food allergy is a rapidly growing public health problem. The interaction between allergens and IgE is at the core of the allergic response. One of the best ways to understand this interaction is through structural characterization. This review focuses on animal-derived food allergens, overviews allergen structures determined by X-ray crystallography, presents an update on IgE conformational epitopes, and explores the structural features of these epitopes. The structural determinants of allergenicity and cross-reactivity are also discussed. Animal-derived food allergens are classified into limited protein families according to structural features, with the calcium-binding protein and actin-binding protein families dominating. Progress in epitope characterization has provided useful information on the structural properties of the IgE recognition region. The data reveals that epitopes are located in relatively protruding areas with negative surface electrostatic potential. Ligand binding and disulfide bonds are two intrinsic characteristics that influence protein structure and impact allergenicity. Shared structures, local motifs, and shared epitopes are factors that lead to cross-reactivity. The structural properties of epitope regions and structural determinants of allergenicity and cross-reactivity may provide directions for the prevention, diagnosis, and treatment of food allergies. Experimentally determined structure, especially that of antigen-antibody complexes, remains limited, and the identification of epitopes continues to be a bottleneck in the study of animal-derived food allergens. A combination of traditional immunological techniques and emerging bioinformatics technology will revolutionize how protein interactions are characterized.

Allergen Diversity and Abundance in Different Tissues of the Redclaw Crayfish (Cherax quadricarinatus)

Shellfish allergy affects ~2.5% of the global population and is a type I immune response resulting from exposure to crustacean and/or molluscan proteins. The Australian Redclaw crayfish (Cherax quadricarinatus) is a freshwater species endemic to and farmed in northern Australia and is becoming an aquaculture species of interest globally. Despite being consumed as food, allergenic proteins from redclaw have not been identified or characterised. In addition, as different body parts are often consumed, it is conceivable that redclaw tissues vary in allergenicity depending on tissue type and function. To better understand food-derived allergenicity, this study characterised allergenic proteins in various redclaw body tissues (the tail, claw, and cephalothorax) and how the stability of allergenic proteins was affected through cooking (raw vs. cooked tissues). The potential of redclaw allergens to cross-react and cause IgE-binding in patients allergic to other shellfish (i.e., shrimp) was also investigated. Raw and cooked extracts were prepared from each body part. SDS-PAGE followed by immunoblotting was performed to determine allergen-specific antibody reactivity to sarcoplasmic calcium-binding protein and hemocyanin, as well as to identify redclaw proteins binding to IgE antibodies from individual and pooled sera of shrimp-allergic patients. Liquid chromatography-mass spectrometry (LC/MS) was utilised to identify proteins and to determine the proportion within extracts. Known crustacean allergens were found in all tissues, with a variation in tissue distribution (e.g., higher levels of hemocyanin in the claw and cephalothorax than in the tail). The proportion of some allergens as a percentage of remaining heat-stable proteins increased in cooked tissues. Previously described heat-stable allergens (i.e., hemocyanin and sarcoplasmic calcium-binding protein) were found to be partially heat-labile. Immunoblotting indicated that shrimp-allergic patients cross-react to redclaw allergens. IgE-binding bands, analysed by LC/MS, identified up to 11 known shellfish allergens. The findings of this study provide fundamental knowledge into the diagnostic and therapeutic field of shellfish allergy.

Characterization and Structural Analyses of Enolase from Shrimp (Litopenaeus vannamei)

Transcriptome analysis had recognized enolase from shrimp Litopenaeus vannamei (L. vannamei), which is termed LvEnolase, as one of the allergens, but its amino acid sequence and protein structure have been lacking. In this study, natural LvEnolase was isolated from L. vannamei and characterized for the first time. The full-length cDNA sequence of LvEnolase was effectively cloned, which encoded 434 amino acid residues. The crystal structure of LvEnolase was successfully determined at a resolution of 2.5 Å by X-ray crystallography (PDB: 8UEL). Notably, it was observed that near the active center, a loop exists in either an open or closed state, and the open loop was associated with the product release phase. Furthermore, enzyme activity assays were conducted to validate the catalytic capabilities of purified LvEnolase. These findings significantly enhance our comprehension of the enolase family and provide valuable support for delving into the functions and characteristics of LvEnolase.

Genomics of Shrimp Allergens and Beyond

Allergy to shellfishes, including mollusks and crustaceans, is a growing health concern worldwide. Crustacean shellfish is one of the "Big Eight" allergens designated by the U.S. Food and Drug Administration and is the major cause of food-induced anaphylaxis. Shrimp is one of the most consumed crustaceans triggering immunoglobulin E (IgE)-mediated allergic reactions. Over the past decades, the allergen repertoire of shrimp has been unveiled based on conventional immunodetection methods. With the availability of genomic data for penaeid shrimp and other technological advancements like transcriptomic approaches, new shrimp allergens have been identified and directed new insights into their expression levels, cross-reactivity, and functional impact. In this review paper, we summarize the current knowledge on shrimp allergens, as well as allergens from other crustaceans and mollusks. Specific emphasis is put on the genomic information of the shrimp allergens, their protein characteristics, and cross-reactivity among shrimp and other organisms.

A comprehensive review on glycation and its potential application to reduce food allergenicity

Food allergens are a major concern for individuals who are susceptible to food allergies and may experience various health issues due to allergens in their food. Most allergenic foods are subjected to heat treatment before being consumed. However, thermal processing and prolonged storage can cause glycation reactions to occur in food. The glycation reaction is a common processing method requiring no special chemicals or equipment. It may affect the allergenicity of proteins by altering the structure of the epitope, revealing hidden epitopes, concealing linear epitopes, or creating new ones. Changes in food allergenicity following glycation processing depend on several factors, including the allergen's characteristics, processing parameters, and matrix, and are therefore hard to predict. This review examines how glycation reactions affect the allergenicity of different allergen groups in allergenic foods.

IgE Mediated Shellfish Allergy in Children-A Review

Shellfish is a leading cause of food allergy and anaphylaxis worldwide. Recent advances in molecular characterization have led to a better understanding of the allergen profile. High sequence homology between shellfish species and between shellfish and house dust mites leads to a high serological cross-reactivity, which does not accurately correlate with clinical cross-reactions. Clinical manifestations are immediate and the predominance of perioral symptoms is a typical feature of shellfish allergy. Diagnosis, as for other food allergies, is based on SPTs and specific IgE, while the gold standard is DBPCFC. Cross-reactivity between shellfish is common and therefore, it is mandatory to avoid all shellfish. New immunotherapeutic strategies based on hypoallergens and other innovative approaches represent the new frontiers for desensitization.

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.

Crustacean shellfish allergens: influence of food processing and their detection strategies

Despite the increasing popularity of crustacean shellfish among consumers due to their rich nutrients, they can induce a serious allergic response, sometimes even life-threatening. In the past decades, a variety of crustacean allergens have been identified to facilitate the diagnosis and management of crustacean allergies. Although food processing techniques can ease the risk of crustacean shellfish allergy, no available processing methods to tackle crustacean allergies thoroughly. Strict dietary avoidance of crustacean shellfish and its component is the best option for the protection of sensitized individuals, which should rely on the compliance of food labeling and, as such, on their verification by sensitive, reliable, and accurate detection techniques. In this present review, the physiochemical properties, structure aspects, and immunological characteristics of the major crustacean allergens have been described and discussed. Subsequently, the current research progresses on how various processing techniques cause the alterations and modifications in crustacean allergens to produce hypoallergenic crustacean food products were summarized and discussed. Particularly, various analytical methodologies employed in crustacean shellfish allergen detection, and the effect of food processing and matrix on these techniques, are also herein emphasized for the appropriate selection of analytical detection tools to safeguard consumers safety.

Identification of Per a 13 as a novel allergen in American cockroach

BACKGROUND

Cockroaches are an important source of indoor allergens. Environmental exposure to cockroach allergens is closely associated with the development of immunoglobulin E (IgE)-mediated allergic diseases. However, the allergenic components in the American cockroaches are not fully studied yet. In order to develop novel diagnostic and therapeutic strategies for cockroach allergy, it is necessary to comprehensively investigate this undescribed allergen in the American cockroach.

METHODS

The full-length cDNA of the potential allergen was isolated from the cDNA library of the American cockroach by PCR cloning. Both the recombinant and natural protein molecules were purified and characterized. The allergenicity was further analyzed by enzyme linked immunosorbent assay, immunoblot, and basophil activation test using sera from cockroach allergic patients.

RESULTS

A novel allergen belonging to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was firstly identified in the American cockroach and named as Per a 13. The cDNA of this allergen is 1255 base pairs in length and contains an open reading frame of 999 base pairs, encoding 332 amino acids. The purified Per a 13 was fully characterized and assessed to react with IgEs from 49.3 % of cockroach allergic patients, and patients with allergic rhinitis were more sensitized to it. Moreover, the allergenicity was further confirmed by immunoblot and basophil activation test.

CONCLUSIONS

We firstly identified GAPDH (Per a 13) in the American cockroach, which is a novel type of inhalant allergen derived from animal species. These findings could be useful in developing novel diagnostic and therapeutic strategies for cockroach allergy.

Cross-reactivity between tick and wasp venom can contribute to frequent wasp sensitization in patients with the α-Gal syndrome

BACKGROUND

α-Gal syndrome (AGS) is a food allergy with severe delayed allergic reactions, mediated by IgE-reactivity to galactose-α1,3-galactose (α-Gal). AGS is strongly associated with tick bites. An increased incidence of venom sensitization has been found in AGS patients. Here, we evaluated the frequency of wasp sensitization in Swedish AGS patients and the possible cross-reactivity between wasp venom and tick proteins.

METHODS

Sera from 136 Swedish AGS patients and 29 wasp-positive non-AGS control sera were analyzed for IgE-reactivity against wasp venom (Vespula spp.), the European tick Ixodes ricinus (Streptavidin ImmunoCAP), α-Gal and total IgE by ImmunoCAP. The presence of α-Gal on wasp venom proteins (Vespula vulgaris) was investigated by western blot (WB), and possible cross-reactivity between wasp venom and tick proteins by enzyme-linked immunosorbent assay and WB. Involvement of cross-reactive carbohydrate domains (CCDs) was also assessed.

RESULTS

Wasp sensitization was present in 54% of AGS patients, although the IgE levels were low. Wasp sensitized patients had higher IgE levels to α-Gal and total IgE levels compared to non-wasp sensitized AGS patients. α-Gal was not detected in wasp venom, but cross-reactivity between wasp and tick proteins was demonstrated which was not dependent on CCDs. The same cross-reactivity was also observed in the control sera. Furthermore, 17 putative cross-reactive peptides were identified using an in silico approach.

CONCLUSIONS

For the first time, cross-reactivity between wasp venom and tick proteins has been described. This may be a reason why the majority of Swedish AGS patients, who have all been tick bitten, are also sensitized against wasp.

Seafood Allergy in Asia: Geographical Specificity and Beyond

Asian countries have unique ways of food processing and dietary habits that may explain the observed differences in the prevalence, natural history, epidemiology and sensitization pattern of food allergic diseases when compared to western countries. Per capita consumption of seafood, including fish and shellfish, is well above the global average for many Asian countries because of their coastal geographical location and rich seafood supply. The wide availability and high abundance of seafood in Asian countries have shaped a diverse way of processing and eating this major food group. Such unique features have significant impact on the sensitization profile and allergenicity of Asians to fish and shellfish. For example, fish and shellfish are eaten raw in some countries that may promote sensitization to heat-labile allergens not otherwise seen in other regions. Fermented fish sauce is commonly used as a condiment in some countries which may promote fish sensitization. Shrimp head and shrimp roe are regarded as delicacies in some countries, but their allergen profiles are yet to be characterized. Freshwater fish and shellfish are a common food source in many Asian countries but the allergenicity of many such species remains unknown. In this review, we discuss factors that may contribute to differences in molecular profile and sensitization pattern for fish and shellfish that are observed in Asian populations and revisit the current status of seafood allergy in this part of the world. Acknowledging the similarities and differences of seafood allergy patterns between Asian and western populations can help us refine a better strategy for diagnosing and managing seafood allergy.

A sensitive immunosensor based on FRET between gold nanoparticles and InP/ZnS quantum dots for arginine kinase detection

Arginine kinase (AK) is one of the most important allergens in shrimp products. Herein, a novel immunoassay for quantitation of AK was developed using the antibody modified gold nanoparticle (AuNP) and quantum dot (QD). When the first antibody modified AuNP (AuNP-Ab1) was bridged by AK with the secondary antibody modified QD (QD-Ab2), fluorescence resonance energy transfer (FRET) would occur between the AuNP and QD, which led to a decrease in fluorescent signals. The decrease in fluorescence intensity was found to correlate linearly with the log of AK concentration in the range of 1.0 × 10^-6-1.0 × 10^-3 mg/mL (R² = 0.9909) and the detection limit was 0.11 ng/mL. The immunoassay was further proved to have encouraging specificity, precision and accuracy. Compared with existing methods, this study provided a promising approach to develop a highly sensitive and selective detection method for AK in shrimp related food samples.

Identification of allergens for food-dependent exercise-induced anaphylaxis to shrimp

Shrimp is a causative food that elicits food-dependent exercise-induced anaphylaxis (FDEIA). In this study, we sought to identify IgE-binding allergens in patients with shrimp-FDEIA. Sera were obtained from eight patients with shrimp-FDEIA and two healthy control subjects. Proteins were extracted from four shrimp species by homogenization in Tris buffer. Immunoblot analysis revealed that IgE from patient sera bound strongly to a 70-kDa and a 43-kDa protein in a preparation of Tris-soluble extracts from Litopenaeus vannamei. Mass spectrometry identified the 70-kDa and 43-kDa proteins as a P75 homologue and fructose 1,6-bisphosphate aldolase (FBPA), respectively. To confirm that the putative shrimp allergens were specifically recognized by serum IgE from shrimp-FDEIA patients, the two proteins were purified by ammonium sulfate precipitation followed by reversed-phase HPLC and/or anion-exchange hydrophobic interaction chromatography and then subjected to immunoblot analysis. Purified P75 homologue and FBPA were positively bound by serum IgE from one and three, respectively, of the eight patients with shrimp-FDEIA, but not by sera from control subjects. Thus, P75 homologue and FBPA are identified as IgE-binding allergens for shrimp-FDEIA. These findings could be useful for the development of diagnostic tools and desensitization therapy for shrimp-FDEIA patients.

Proteomics-Based Methodologies for the Detection and Quantification of Seafood Allergens

Seafood is considered one of the main food allergen sources by the European Food Safety Authority (EFSA). It comprises several distinct groups of edible aquatic animals, including fish and shellfish, such as crustacean and mollusks. Recently, the EFSA recognized the high risk of food allergy over the world and established the necessity of developing new methodologies for its control. Consequently, accurate, sensitive, and fast detection methods for seafood allergy control and detection in food products are highly recommended. In this work, we present a comprehensive review of the applications of the proteomics methodologies for the detection and quantification of seafood allergens. For this purpose, two consecutive proteomics strategies (discovery and targeted proteomics) that are applied to the study and control of seafood allergies are reviewed in detail. In addition, future directions and new perspectives are also provided.

Resolving hemocyanin isoform complexity in haemolymph of black tiger shrimp Penaeus monodon - implications in aquaculture, medicine and food safety

Hemocyanin (Hc) is a multifunctional macromolecule involved in oxygen transport and non-specific immunity in shrimp. Hc is crucial in physiology and nutrition linked with optimal performance in aquaculture production systems. In medicine, Hc has been approved for clinical use in humans as adjuvant and anticancer therapeutic. In contrast, Hc has also been identified as one of the proteins causing anaphylaxis following shrimp consumption. The role of individual Hc isoforms remains unknown due to a lack of resolved Hc isoforms. We successfully identified eleven different Penaeus monodon hemocyanin (PmoHc) γ isoforms including two truncated isoforms (50 and 20 kDa) and one PmoHc β isoform in haemolymph using proteomics informed by transcriptomics. Amino acid sequence homology ranged from 24 to 97% between putative PmoHc gene isoforms. Hc isoforms showed specific patterns of transcript expression in shrimp larval stages and adult hepatopancreas. These findings enable isoform level investigations aiming to define molecular mechanisms underpinning Hc functionality in shrimp physiology and immunity, as well as their individual immunogenic role in human allergy. Our research demonstrates the power of proteomics informed by transcriptomics to resolve isoform complexity in non-model organisms and lay the foundations for improved performance within the aquaculture industry and advance allergenic applications in medicine. SIGNIFICANCE: The roles of hemocyanin (Hc) in shrimp homeostasis and immunity as well as in human allergy are not well understood because the complexity of Hc isoforms has remained unresolved. Our results have confirmed the existence of at least 12 individual Hc isoforms in shrimp haemolymph and validated putative Hc gene assemblies from transcriptomics. Our findings will enable monitoring the expression of specific Hc isoforms in shrimp haemolymph during different environmental, nutritional and pathogenic conditions, thus providing insights into isoform specific functional roles. In medicine, the potential allergenicity of each Hc isoform could be determined and advance allergenic applications. Lastly, since Hc comprises up to 95% of the total protein in haemolymph, these isoforms become ideal targets for prawn provenance, traceability and food contamination studies.

Aptameric biosensor for the sensitive detection of major shrimp allergen, tropomyosin

The development of a sensitive and rapid detection approach for allergens in various food matrices is essential to assist patients in managing their allergies. The most common methods used for allergen detection are based on immunoassays, PCR and mass spectrometry. However, all of them are very complex and time-consuming. Herein, an aptamer biosensor for the detection of the major shrimp allergen tropomyosin (TM) was developed. Graphene oxide (GO) was used as a platform for screening of the minimal-length aptamer sequence required for high-affinity target binding. A fluorescein dye labeled GO quenches the truncated aptamer by π-stacking interactions. After the addition of TM, the fluorescence was restored due to the competitive binding of the aptamer to GO. One of the truncated aptamers was found to bind to TM with four-fold higher affinity (30 nM) compared to the full-length aptamer (124 nM), with a limit of detection (LOD) of 2 nM. The aptamer-based sensor demonstrates the sensitive, selective, and specific detection of TM in 30 min. The performance of the sensor was confirmed using TM spiked chicken soup, resulting in a high percentage recovery (~97 ± 10%). The association of GO and labelled aptamer sensor platform has shown the rapid detection of TM in food, which is compared to other methods very sensitive, specific and performs in high throughput application.

Identification of pyruvate kinase 2 as a possible crab allergen and analysis of allergenic proteins in crabs consumed in Taiwan

In Taiwan, crab is one of the main causes for food allergy. Several proteins are recognized as crustacean allergens, and tropomyosin is known to be the major one. However, sensitization patterns of Taiwanese patients to crustacean allergens remain unclear. Therefore, we analyzed the specific-IgE binding ability of crucifix crab (Charybdis feriatus) allergens by western blot using patients' sera. In particular, we found a 56 kDa protein in crucifix crab reacted with specific-IgEs in patients' sera, and we further identified the protein as a novel crab allergen pyruvate kinase 2. Additionally, little is known about tropomyosin contents in crabs consumed in Taiwan. Thus, we also quantified the levels of tropomyosin by using enzyme-linked immunosorbent assay (ELISA) among raw and cooked crab species. Our results showed tropomyosin levels varied depending on crab species. In summary, these findings improve the understanding of crustacean allergens and contribute to the clinical diagnosis of crustacean allergies.

A review on methodologies for extraction, identification and quantification of allergenic proteins in prawns

Prawn allergy is one of the most common food-borne allergies and current prevention is by avoidance. This review paper summarised different methodologies for the extraction, identification and quantification of prawn protein allergens, reported in various research studies. Following extraction, allergenic components have been analysed using well-established methodologies, such as SDS-PAGE, Immunoblotting, ELISA, CD Spectroscopy, HPLC, DBPCFC, SPT etc. Moreover, the preference towards Aptamer-based technique for allergenicity analysis has also been highlighted in this review paper. The summary of these methodologies will provide a reference platform for present and future research directions.

Limited cross reactivity among arginine kinase allergens from mealworm and cricket edible insects

Insects are seen as a solution to the increasing demand for protein sources for food. However, entomophagy has unfortunately been linked to allergic reactions in Europe with people with professional contacts. As mealworms (Tenebrio molitor) and crickets (Acheta domesticus) have recently become commercially available (both whole or in food formulation) in several European countries, this research assessed the cross allergenicity of arginine kinase (AK). Based on the collection of sera from a entomology laboratory staff, oven cooked insects but also purified AK fractions were tested. Immunoblotting against the protein extracts revealed different Immunoglobulin E reactivity of sera according to the insect target species: two bands (40 and 14 kDa) for crickets and a pattern including light responses at 17, 25 and 37 kDa for mealworms. Focusing on AK, low specific allergenicity was here illustrated and discussed in relation to the development of a safe edible insect consumption by humans.

Novel foods: a risk profile for the house cricket (Acheta domesticus)

Novel foods could represent a sustainable alternative to traditional farming and conventional foodstuffs. Starting in 2018, Regulation (EU) 2283/2015 entered into force, laying down provisions for the approval of novel foods in Europe, including insects. This Approved Regulation establishes the requirements that enable Food Business Operators to bring new foods into the EU market, while ensuring high levels of food safety for European consumers. The present risk profile tackles the hazards for one of the most promising novel food insects, the house cricket (Acheta domesticus). The risk profile envisages a closed A. domesticus crickets rearing system, under Hazard Analysis and Critical Control Points (HACCP) and good farming practices (GFP), in contrast with open cricket farms. The methodology used involves screening the literature and identifying possible hazards, followed by adding relevant inclusion criteria for the evidence obtained. These criteria include animal health and food safety aspects, for the entire lifespan of crickets, based on the farm to fork One Health principle. When data were scarce, comparative evidence from close relatives of the Orthoptera genus was used (e.g. grasshoppers, locusts and other cricket species). Nevertheless, significant data gaps in animal health and food safety are present. Even if HACCP‐type systems are implemented, the risk profile identifies the following considerable concerns: (1) high total aerobic bacterial counts; (2) survival of spore‐forming bacteria following thermal processing; (3) allergenicity of insects and insect‐derived products; and (4) the bioaccumulation of heavy metals (e.g. cadmium). Other hazards like parasites, fungi, viruses, prions, antimicrobial resistance and toxins are ranked as low risk. For some hazards, a need for additional evidence is highlighted.

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.

Identification of pyruvate kinase as a novel allergen in whiteleg shrimp (Litopenaeus vannamei) by specific-IgE present in patients with shrimp allergy

Food allergy is one of the most important health issues worldwide. In Taiwan, current literature suggests shrimps and crabs are the most common causes of food allergy, and are frequently associated with acute allergic reactions such as urticaria, atopic dermatitis, and asthma. However, knowledge regarding the shrimp allergens remains limited. Thus, there is an urgent need to establish comprehensive information for elucidating underlying triggers for food allergy. In this study, whiteleg shrimp (Litopenaeus vannamei) was used to evaluate the IgE-binding properties of various shrimp proteins to 7 allergic patients' sera by western blot. A 63 kDa protein was found in raw and cooked shrimp bound to specific-IgEs in 7 and 4 patients' sera, respectively. This protein was further identified as pyruvate kinase based on the proteomic mass spectrometry. This study identifies an important shrimp allergen unique to Taiwan and further testing and prevention measures might be implemented in the allergen analysis.

Detecting Allergens From Black Tiger Shrimp Penaeus monodon That Can Bind and Cross-link IgE by ELISA, Western Blot, and a Humanized Rat Basophilic Leukemia Reporter Cell Line RS-ATL8

Background

Black tiger shrimp Penaeus monodon is one of the common causes of shellfish allergy that is increasing worldwide. One of the important problems in the management of shellfish allergy is the lack of accurate diagnostic assay because the biological and immunological properties of allergens in black tiger shrimp have not been well characterized. This study aims to detect proteins with the ability to bind and cross-link immunoglobulin E (IgE) from black tiger shrimp by enzyme-linked immunosorbent assay (ELISA), Western blot, and a humanized rat basophilic leukemia reporter cell line RS-ATL8.

Methods

Sera from shrimp allergic subjects were subjected to ELISA and Western blots using raw or cooked shrimp extract as antigens. Pooled sera were used to sensitize the RS-ATL8 reporter cell line and cells were activated by shrimp extract. Eluted protein extracts separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were tested on the RS-ATL8 cell line and subjected to mass spectrometry to identify potential candidate allergens.

Results

Allergic sera reacted stronger to raw shrimp extract than cooked shrimp extract (P=0.009). Western blot demonstrated that major IgE reactivity protein bands were at 32–39 kDa and 91–230 kDa in both raw and cooked shrimp extracts. The eluted protein bands at the molecular weight of 38 and 115 kDa from raw shrimp extract induced IgE cross-linking as assayed by the RS-ATL8 cell line. These protein bands were subjected to mass spectrometry for analysis. Ubiquitin-activating enzyme and crustacyanin were identified as potential candidate novel shrimp allergens.

Conclusions

The RS-ATL8 reporter cell line can be used to identify potential new shrimp allergens that can functionally cross-link IgE and induce mast cell degranulation.

Mite-Induced Asthma and IgE Levels to Shrimp, Mite, Tropomyosin, Arginine Kinase, and Der p 10 Are the Most Relevant Risk Factors for Challenge-Proven Shrimp Allergy

BACKGROUND

Shrimp sensitization is common in the general population, but the presence of symptoms is only moderately related to sensitization. A point still at issue is which in vivo and/or in vitro tests (food challenge, component-resolved diagnosis, house dust mite [HDM] sensitization) can help in distinguishing shrimp-allergic subjects from subjects that are sensitized but tolerant.

METHODS

The aim of this study was to evaluate the role of IgE to the different shrimp and mite allergens in distinguishing shrimp challenge-positive from challenge-negative patients. Subjects with suspected hypersensitivity reactions to shrimp, positive skin prick tests (SPTs), and/or anti-shrimp IgE were submitted to open and double-blind placebo-controlled food challenges (DBPCFC). Specific IgE to shrimp, mites, and the recombinants rPen a 1, rDer p 1, 2, and 10 were tested using ImmunoCAP-FEIA. IgE immunoblotting was performed to identify the patients' allergenic profiles.

RESULTS

In total, 13 out of 51 (25.5%) patients with reported reactions to shrimp were truly shrimp allergic (7 DBPCFC positive and 6 with documented severe reactions). These patients had significantly higher skin test wheal diameters than nonallergic patients, as well as higher levels of IgE to rPen a 1 and rDer p 10. HDM-induced asthma and the simultaneous presence of anti-nDer p 1, 2, and 10 IgE levels increased the risk of true shrimp allergy.

CONCLUSION

Food challenge tests are mandatory for the diagnosis of shrimp allergy. Tropomyosin is associated with clinical reactivity. HDM-induced asthma and anti-mite IgE are risk factors for shrimp allergy.

Allergenome characterization of the mosquito Aedes aegypti

BACKGROUND

Saliva and muscle-derived mosquito allergens have been purified and characterized. However, the complete set of allergens remains to be elucidated. In this study, we identified and characterized IgE-binding proteins from the mosquito species Aedes aegypti.

METHODS

Serum was obtained from 15 allergic individuals with asthma and/or rhinitis and sensitized to mosquito. IgE binding was determined by ELISA. Total proteins from freeze-dried bodies of A. aegypti were extracted and IgE-reactive proteins were identified by 2D gel electrophoresis, followed by Western blot with pooled or individual sera. IgE-reactive spots were further characterized by mass spectrometry.

RESULTS

Twenty-five IgE-reactive spots were identified, corresponding to 10 different proteins, some of which appeared as different variants or isoforms. Heat-shock cognate 70 (HSC-70) and tropomyosin showed IgE reactivity with 60% of the sera, lysosomal aspartic protease, and "AAEL006070-PA" (Uniprot: Q177P3) with 40% and the other proteins with <33.3% of the sera. Different variants or isoforms of tropomyosin, arginine or creatine kinase, glyceraldehyde-3-phosphate dehydrogenase (GPDH), calcium-binding protein, and phosphoglycerate mutase were also identified. The mixture of three allergens (Aed a 6, Aed a 8, and Aed a 10) seems to identify more than 80% of A. aegypti-sensitized individuals, indicating that these allergens should be considered when designing of improved mosquito allergy diagnostic tools.

CONCLUSIONS

The newly identified allergens may play a role in the pathophysiology of mosquito allergy in the tropics, and some of them might be important arthropod-related proteins involved in cross-reactivity between A. aegypti and other allergenic arthropods.

Shellfish allergens: tropomyosin and beyond

IgE-mediated shellfish allergy constitutes an important cause of food-related adverse reactions. Shellfish are classified into mollusks and crustaceans, the latter belonging to the class of arthropoda. Among crustaceans, shrimps are the most predominant cause of allergic reactions and thus more extensively studied. Several major and minor allergens have been identified and cloned. Among them, invertebrate tropomyosin, arginine kinase, myosin light chain, sarcoplasmic calcium-binding protein, and hemocyanin are the most relevant. This review summarizes our current knowledge about these allergens.

A Proteomic Study of Hemocyte Proteins from Mud Crab (Scylla paramamosain) Infected with White Spot Syndrome Virus or Vibrio alginolyticus

In this study, we investigated the hemocytes' immune response to white spot syndrome virus (WSSV) or Vibrio alginolyticus infection at the protein level. The differential proteomes from crab hemocytes infected with WSSV or V. alginolyticus were analyzed using the isobaric tags for relative and absolute quantitation approach immediately after infection. Using this approach, we identified 1,799 proteins by their by LC-MS/MS spectra and sequencing data. These included 157 upregulated proteins and 164 downregulated proteins after WSSV infection. Similarly, 243 proteins were determined to be differentially expressed during V. alginolyticus infection, of these, 121 were upregulated and 122 were downregulated after infection. Interestingly, among these differentially expressed proteins, 106 were up- or downregulated significantly in both WSSV and V. alginolyticus infection. Six genes, β-actin, myosin-9, anti-lipopolysaccharide factor isoform 4, anti-lipopolysaccharide factor 4, transketolase-like protein 2-like isoform 1, and sarcoplasmic calcium-binding protein 1 were chosen for further study. The expression of these genes all showed a trend of upregulation at 24 h post-WSSV or V. alginolyticus infection except for myosin-9 in response to WSSV. To confirm the protective effects of the six genes, crabs were injected with specific dsRNAs before WSSV or V. alginolyticus challenge. The results showed that the knockdown of these genes led to an increase in the morbidity and mortality (P < 0.01) rate, and a decrease in infection time in WSSV-infected crabs. During the first 84 h, knockdown of these genes also led to an increase in the morbidity rates in V. alginolyticus -infected crabs, and results of four genes showed a higher mortality rate than that of the control after they were knocked down. This is the first report of the proteome response in crab hemocytes during WSSV or V. alginolyticus infection. These findings will contribute to our understanding of the immune response to WSSV and V. alginolyticus infection in crabs.

Structure-based modelling of hemocyanin allergenicity in squid and its response to high hydrostatic pressure

The secondary, tertiary, and quaternary structures of squid hemocyanin (Hc) were characterised, and the relationship between Hc structure and allergenicity responses to high hydrostatic pressure (HHP) was modelled. The Hc allergenicity varied with its protein structure. Electrophoresis analysis revealed that HHP treatment significantly decreased the band intensity of Hc when increasing pressure from 200 and 400 MPa to 600 MPa. The protein structure analysis of squid Hc showed that while HHP treatment decreased the α-helix content, free sulfhydryl content, and R_g, it increased the random coil content, surface hydrophobicity index (Ho), Guinier aggregation number (〈N_agg〉_G) and average aggregation number (〈N_agg〉_Q). The α-helix and random coil contents of the 600 MPa treated samples were 23.67% and 37.54%, respectively, compared to 32.37% and 32.02% in the control, respectively. HHP treatment decreased the IgE and IgG-binding capacities, indicating a significant decrease in the allergenicity (P< 0.05) of squid Hc. This study provided meaningful information of applying HHP to reduce allergenicity, and explained the responses of Hc protein structure to HHP for lowering the allergenicity of squid.

Identification and characterization of ovary development-related protein EJO1 (Eri s 2) from the ovary of Eriocheir sinensis as a new food allergen

SCOPE

Crab is a major source of shellfish allergens. Most studies have focused on allergens in crab muscle (CM) rather than on allergens in crab ovary (CO). This study aimed to identify potential allergens in CO from Eriocheir sinensis.

METHODS AND RESULTS

Dot blot and immunoblotting results revealed the differential reactivity of CM and CO extracts to positive sera from patients allergic to crabs. Four CO proteins showed good specific IgE-binding activities in 2-DE/immunoblotting analysis; mass spectrometry identified the proteins as hemocyanin, vitellogenin, ovary development-related protein EJO1and EJO2. The recently identified allergen EJO1 is named 'Eri s 2' in the World Health Organization and International Union of Immunological Societies (WHO/IUIS) allergen nomenclature database. Recombinant Eri s 2 exhibited good reactivity to positive sera, and pre-incubation with recombinant Eri s 2 abrogated the reactivity of positive sera from two patients to CO in a dose-dependent manner. Moreover, co-incubation of recombinant Eri s 2 with patient basophils dose-dependently promoted basophil activation, confirming the biological activity of Eri s 2.

CONCLUSION

CO tissue is an important allergen source, and Eri s 2 is a new crab allergen. This study provides insights that will be useful for component-resolved diagnostics for crab allergy.

Effect of thermal processing on mealworm allergenicity

SCOPE

The growing world population requires the exploration of new sustainable protein sources to ensure food security. Insects such as mealworm are promising candidates. For safety reasons, a risk assessment, including allergy risks, is needed. Since allergenicity can be influenced by thermal processing, it is highly important to take this into account.

METHODS AND RESULTS

Fresh mealworm was heat processed and extracted by a sequential extraction method using in succession Tris, urea, and a combined SDS/DTT buffer. Extracts were tested using immunoblot, basophil activation test and skin prick test in 15 shrimp allergic patients, previously indicated as population at risk for mealworm allergy. Immunoblots showed a difference in IgE binding between processed and unprocessed mealworm extracts. However, this was due to change in solubility. Some allergens were soluble in urea buffer, but became more soluble in Tris buffer and vice versa. IgE binding was seen for all extracts in blot and basophil activation test. The results from 13 skin prick tests showed a skin reaction similar between processed and unprocessed mealworm.

CONCLUSION

Thermal processing did not lower allergenicity but clearly changed solubility of mealworm allergens. A sequential extraction method allowed for assessment of a broader protein panel.

Identification of novel allergen in edible insect, Gryllus bimaculatus and its cross-reactivity with Macrobrachium spp. allergens

Edible insects have recently been promoted as a source of protein and have a high nutrition value. Identification of allergens and cross-reactivity between Macrobrachium spp. and the field cricket (Gryllus bimaculatus) is necessary for food safety control and to assist in the diagnosis and therapy of allergy symptoms. Denaturing polyacrylamide gel electrophoresis (SDS-PAGE) was used to separate proteins. Allergens were determined and identified by IgE-immunoblotting with pooled sera from prawn-allergic patients (n=16) and LC-MS/MS. Arginine kinase (AK) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) were determined as the important allergens in muscle of Macrobrachium rosenbergii whereas, hemocyanin (HC) was identified as an allergen in Macrobrachium spp. The allergens in Macrobrachium lanchesteri were identified as AK and HC. In addition, hexamerin1B (HEX1B) was identified as a novel and specific allergen in G. bimaculatus. The important allergen in G. bimaculatus and Macrobrachium spp. is AK and was found to cross-react between both species.