A Proteomic- and Bioinformatic-Based Identification of Specific Allergens from Edible Insects: Probes for Future Detection as Food Ingredients

IgE-based analysis of sensitization and cross-reactivity to yellow mealworm and edible insect allergens before their widespread dietary introduction

The European Commission authorized the use of dried yellow mealworm (Tenebrio molitor - TM) as a food ingredient under Regulation EU 2021/882. As TM emerges as an important allergen source, sensitization and allergy to TM in various populations need investigation. The aim of this study was to assess the incidence of sensitization to TM before its introduction as a food ingredient in Poland, as well as checking the occurrence of co-sensitivity to TM and other invertebrate allergenic extracts and molecules. This analysis was performed using serum allergen-specific immunoglobulin E (sIgE) results in 6,173 individuals using the ALEX2 test to detect sensitivity to TM and other related allergens. A total of 4.3% of the study population had sIgE to TM extract, with 0.7% of those individuals being mono-sensitized to TM. Sensitization to TM was most commonly associated with a positive response to house cricket and migratory locust allergens. sIgE antibodies against TM significantly more commonly (p < 0.001) co-occurred with sIgE against other invertebrate allergens. Patients with sIgE against TM were most likely sensitised to tropomyosins (49.1% of patients), Niemann-Pick C2 protein (43.8%), group 5/21 allergen (38.6%), class III chitinases (37.1%), and cysteine proteases (34.1%). Based on the serum asIgE levels to TM prior to this ingredient being introduced as a food in Poland, we hypothesised that this primary sensitization may be associated with invertebrate allergies. Our analysis showed that sensitisation to TM was most commonly associated with a positive reaction to house dust mites and shrimp tropomyosins. Therefore, we speculate that individuals allergic to shrimp should exercise caution when consuming foods containing TM.

Leg muscles of migratory locust (Locusta migratoria) as a protein source: Extraction, protein composition and foaming properties

Migratory locust (Locusta migratoria) is an edible insect species that is usually consumed at the adult developmental stage and represents a valuable source of proteins. Locusts can be processed into food ingredients or directly consumed after removal of legs and wings. Legs represent a unique matrix, which comprises a chitin-based exoskeleton typical for insects and muscle tissues commonly occurring also in other animals. Muscle proteins can be easily extracted from traditional animal sources, but the efficiency of these methods for locust legs as well as the functional characteristics of the resulting protein extracts have not been previously explored. This study first compared protein extraction methods at acid, alkaline, and salt-assisted conditions. All three methods resulted in a significantly higher extraction yield from locust leg muscles (0.465-0.595 g/g) than from whole locusts (0.061-0.125 g/g). Shotgun proteomics of the protein fraction extracted at alkaline conditions assigned 310 muscle proteins, comprising components assigned to energy and carbon metabolism, as well as to skeletal, protein folding, membrane trafficking, and cell adhesion functions. The techno-functional potential of locust leg muscles was assessed by a foamability assay. Foam stability of locust leg extracts varied as a function of pH extraction and re-solubilization conditions and was significantly higher (58.3-70.8 %) than for whey proteins taken as a benchmark (38.3-51.7 %); foam capacity at t = 0 h was in the range of 48.6-68.8 %. This study demonstrates that locust legs, which can be a by-product of locust consumption or processing, should be considered a rich source of muscle proteins with promising technological functionality.

Edible crickets as a possible way to curb protein-energy malnutrition: Nutritional status, food applications, and safety concerns

Protein malnutrition is a major public health concern in the developing world. The livestock products are a good source of high-quality protein, but the livestock industry is a source of pollution and one of the leading causes of climate change because the slaughtering of animals results in the accumulation of waste, offals, and several inedible body portions. The rapid increase in the human population and inadequate supply of traditional protein sources have driven a search for novel and alternative protein sources such as edible insects. This review extensively explores the nutritional value, allergenicity, and safety considerations associated with consuming common house crickets and other related insect species. A wide range of cricket protein-based products are currently available and provide some attractive options to the consumers such as protein-enriched bakery products and gluten-free bread for celiac patients. The cricket protein hydrolysates are used as preservatives to improve the stability of cheddar cheese and goat meat emulsions during storage. The risks associated with edible crickets and their products are bacteria, mycotoxins, polychlorinated dibenzodioxins, pesticide residues, heavy metals, and the presence of allergenic proteins.

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.

Utilizing the Banana S-Adenosyl-L-Homocysteine Hydrolase Allergen to Identify Cross-Reactive IgE in Ryegrass-, Latex-, and Kiwifruit-Allergic Individuals

Food allergies mediated by specific IgE (sIgE) have a significant socioeconomic impact on society. Evaluating the IgE cross-reactivity between allergens from different allergen sources can enable the better management of these potentially life-threatening adverse reactions to food proteins and enhance food safety. A novel banana fruit allergen, S-adenosyl-L-homocysteine hydrolase (SAHH), has been recently identified and its recombinant homolog was heterologously overproduced in E. coli. In this study, we performed a search in the NCBI (National Center for Biotechnology Information) for SAHH homologs in ryegrass, latex, and kiwifruit, all of which are commonly associated with pollen-latex-fruit syndrome. In addition, Western immunoblot analysis was utilized to identify the cross-reactive IgE to banana SAHH in the sera of patients with a latex allergy, kiwifruit allergy, and ryegrass allergy. ClustalOmega analysis showed more than 92% amino acid sequence identity among the banana SAHH homologs in ryegrass, latex, and kiwifruit. In addition to five B-cell epitopes, in silico analysis predicted eleven T-cell epitopes in banana SAHH, seventeen in kiwifruit SAHH, twelve in ryegrass SAHH, and eight in latex SAHH, which were related to the seven-allele HLA reference set (HLA-DRB1*03:01, HLA-DRB1*07:01, HLA-DRB1*15:01, HLA-DRB3*01:01, HLA-DRB3*02:02, HLA-DRB4*01:01, HLA-DRB5*01:01). Four T-cell epitopes were identical in banana and kiwifruit SAHH (positions 328, 278, 142, 341), as well as banana and ryegrass SAHH (positions 278, 142, 96, and 341). All four SAHHs shared two T-cell epitopes (positions 278 and 341). In line with the high amino acid sequence identity and B-cell epitope homology among the analyzed proteins, the cross-reactive IgE to banana SAHH was detected in three of three latex-allergic patients, five of six ryegrass-allergic patients, and two of three kiwifruit-allergic patients. Although banana SAHH has only been studied in a small group of allergic individuals, it is a novel cross-reactive food allergen that should be considered when testing for pollen-latex-fruit syndrome.

An analysis of emerging food safety and fraud risks of novel insect proteins within complex supply chains

Food consumption play a crucial role in human life, yet conventional food production and consumption patterns can be detrimental to the environment. Thus, research and development has been directed towards alternative proteins, with edible insects being promising sources. Edible insects have been recognised for their sustainable benefits providing protein, with less emission of greenhouse gas, land and water usage compared to sources, such as beef, chicken, and dairy products. Among the over 2000 known edible insect species, only four, namely yellow mealworm (Tenebrio molitor), migratory locust/grasshopper (Locusta migratoria), grain mould beetle, also known as lesser mealworm which is a larval form of Alphitobius diaperinus (from the family of Tenebrionidae of darkling beetles) and house cricket (Acheta domesticus), are currently authorised in specific products through specific producers in the EU. The expansion of such foods into Western diets face challenges such as consumer barriers, gaps in microbiological and chemical safety hazard data during production and processing, and the potential for fraudulent supply chain activity. The main aim of this study was to map the supply chain, through interviews with personnel along the supply chain, coupled with searches for relevant publications and governmental documents. Thus, the main potential points of food safety and fraud along the edible insect supply chain were identified. Feed substrate was identified as the main area of concern regarding microbiological and chemical food safety and novel processing techniques were forecast to be of most concern for future fraudulent activity. Despite the on-going authorisation of insect species in many countries there are substantial food safety and authenticity information gaps in this industry that need to be addressed before edible insects can be viewed as a safe and sustainable protein sources by Western consumers.

Rhynchophorus ferrugineus larvae: A novel source for combating broad-spectrum bacterial and fungal infections

Antimicrobial resistance is a growing concern due to the growth of antibiotic-resistant microorganisms, which makes it difficult to treat infection. Due to its broad-spectrum antimicrobial properties against a diverse array of bacteria, both Gram-positive and Gram-negative bacteria, and fungi, Rhynchophorus ferrugineus larval antimicrobial peptides (AMPs) have demonstrated potential as antimicrobial agents for the treatment of microbial infections and prevention of antibiotic resistance. This study emphasizes the unexplored mechanisms of action of R. ferrugineus larvae against microorganisms. Among the most widely discussed mechanisms is the effect of AMPs in larvae in response to a threat or infection. Modulation of immune-related genes in the intestine and phagocytic capacity of its hemocytes may also affect the antimicrobial activity of R. ferrugineus larvae, with an increase in phenoloxidase activity possibly correlated with microbial clearance and survival rates of larvae. The safety and toxicity of R. ferrugineus larvae extracts, as well as their long-term efficacy, are also addressed in this paper. The implications of future research are explored in this paper, and it is certain that R. ferrugineus larvae have the potential to be developed as a broad-spectrum antimicrobial agent with proper investigation.

Food allergen detection by mass spectrometry: From common to novel protein ingredients

Food allergens are molecules, mainly proteins, that trigger immune responses in susceptible individuals upon consumption even when they would otherwise be harmless. Symptoms of a food allergy can range from mild to acute; this last effect is a severe and potentially life-threatening reaction. The European Union (EU) has identified 14 common food allergens, but new allergens are likely to emerge with constantly changing food habits. Mass spectrometry (MS) is a promising alternative to traditional antibody-based assays for quantifying multiple allergenic proteins in complex matrices with high sensitivity and selectivity. Here, the main allergenic proteins and the advantages and drawbacks of some MS acquisition protocols, such as multiple reaction monitoring (MRM) and data-dependent analysis (DDA) for identifying and quantifying common allergenic proteins in processed foodstuffs are summarized. Sections dedicated to novel foods like microalgae and insects as new sources of allergenic proteins are included, emphasizing the significance of establishing stable marker peptides and validated methods using database searches. The discussion involves the in-silico digestion of allergenic proteins, providing insights into their potential impact on immunogenicity. Finally, case studies focussing on microalgae highlight the value of MS as an effective analytical tool for ensuring regulatory compliance throughout the food control chain.

Unveiling the potential of proteomics in addressing food and feed safety challenges

The food and feed sector in Europe is rapidly evolving to address contemporary challenges, striving for fairer, safer, greener and more sustainable food systems. This includes the exploration of new protein sources for human consumption and animal feed such as protein derived from insects, algae or novel plant-derived proteins, and the re-evaluation of existing sources like processed animal protein (PAP). To generate reliable data on the diverse array of emerging protein sources for future food and feed safety assessments, a growing demand for the development and implementation of advanced analytical techniques exists. New approach methodologies (NAMs) including, mass spectrometry (MS)-based proteomics methods have been emerging as valuable techniques which potentially can be implemented in regulatory laboratory settings to complement conventional approaches in this realm. These MS-driven strategies have already proven their utility in diverse applications, including the detection of prohibited substances in feed, identification of allergens, differentiation of fish species in complex mixtures for fraud detection and the verification of novel foods and alternative protein sources. This EU-FORA programme was focused on three core objectives namely: (i) the training of the fellow in utilising MS-based proteomics for food and feed safety analyses, (ii) the involvement of the fellow in the development of standardised operating procedures (SOP) for targeted and non-targeted proteomic MS-based workflows for species and tissues specific PAP identification in a national reference laboratory (NRL) and (iii) the transfer and implementation of MS-based approaches and standardised protocols for PAP analysis at the fellow's home institution. Altogether, this programme facilitates the broadening and diversification of use of MS-based proteomic methodologies for reinforcing their significance within the domains of food and feed safety research and regulatory science applications.

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.

Monitoring Yellow Mealworm (Tenebrio molitor) as a Potential Novel Allergenic Food: Effect of Food Processing and Matrix

The consumption of insects has increased in western countries, raising concerns about their potential to induce food allergic reactions in sensitized/allergic individuals. This work intended to develop a real-time PCR approach for the detection/quantification of yellow mealworm (Tenebrio molitor) as a potential allergenic food in complex matrices. For this purpose, reference mixtures simulating the production of pork sausages and wheat biscuits containing known amounts of mealworm were used. Real-time PCR with TaqMan probe targeting the cytochrome b gene of T. molitor was able to detect up to 2 fg of insect DNA, and 1.0 and 0.1 mg/kg of mealworm flour in autoclaved sausages and baked biscuits, respectively. Generally, the method showed acceptable analytical performance parameters, confirming its suitability/applicability for a wide range of foods. However, real-time PCR data showed significant differences among food matrix and processing, highlighting the importance of using appropriate calibration models for quantitative analysis. Finally, the real-time PCR approach was successfully validated with blind mixtures and applied to commercial samples, demonstrating its efficacy and reliability in the quantification of mealworm in processed foodstuffs.

Insects in food and their relevance regarding allergenicity assessment

Within the European Green Deal, the 'Farm-to-Fork' strategy aims to accelerate the transition to a sustainable food system and to make food systems fair, healthy and environmentally friendly. Insects contribute to the circularity of agriculture, and are ideal candidates to complement traditional sources of protein. In this context, a working programme within the European Food Risk Assessment (EU-FORA) Fellowship Programme framework was developed at the German Federal Institute for Risk Assessment in collaboration with the Spanish National Research Council. The purpose of this technical report is to describe the activities in which the fellow was involved. As part of the training, the fellow performed a literature search regarding insects as food and allergenicity resulting in 493 hits. Out of the literature search a comprehensive scientific database with 200 publications has been built using the application 'EndNote'. Furthermore, an extensive scientific review with the title 'Sustainable food systems: EU regulatory framework and contribution of insects to the Farm-to-Fork strategy' approaching several important issues regarding insects (Regulatory frame, Market situation, Labelling and Control, Application as food/feed, Consumer acceptance and Allergenicity risk assessment) has been drafted and sent for publication in a peer reviewed journal. In order to analyse the impact of food processing on the allergenicity of insects, different food samples were prepared and artificially digested using a protocol simulating the gastrointestinal tract. Further laboratory work to analyse the readouts, including enzyme-linked immunosorbent assay (ELISA), has been discussed and proposed, scheduled for the end of July. In conclusion, the present working programme, together with additional activities and training provided by different institutions, enabled the fellow to gain a broader perspective in food safety, particularly concerning insects as novel foods and their safety assessment.

Current Scenario of Pathogen Detection Techniques in Agro-Food Sector

Over the past-decade, agricultural products (such as vegetables and fruits) have been reported as the major vehicles for foodborne diseases, which are limiting food resources. The spread of infectious diseases due to foodborne pathogens poses a global threat to human health and the economy. The accurate and timely detection of infectious disease and of causative pathogens is crucial in the prevention and treatment of disease. Negligence in the detection of pathogenic substances can be catastrophic and lead to a pandemic. Despite the revolution in health diagnostics, much attention has been paid to the agro-food sector regarding the detection of food contaminants (such as pathogens). The conventional analytical techniques for pathogen detection are reliable and still in operation. However, laborious procedures and time-consuming detection via these approaches emphasize the need for simple, easy-to-use, and affordable detection techniques. The rapid detection of pathogens from food is essential to avoid the morbidity and mortality originating from the suboptimal nature of empiric pathogen treatment. This review critically discusses both the conventional and emerging bio-molecular approaches for pathogen detection in agro-food.

Safety of frozen and dried formulations from whole house crickets (Acheta domesticus) as a Novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Food and Food Allergens (NDA) was asked to deliver an opinion on the safety of frozen and dried formulations from house crickets (Acheta domesticus) as a novel food pursuant to Regulation (EU) 2015/2283. The NF is proposed in three formulations: (i) frozen, (ii) dried, (iii) ground. The main components of the NF are protein, fat and fibre (chitin) in the dried form of the NF, and water, protein, fat and fibre (chitin) in the frozen form of the NF. The Panel notes that the concentrations of contaminants in the NF depend on the occurrence levels of these substances in the insect feed. The Panel further notes that there are no safety concerns regarding the stability of the NF if the NF complies with the proposed specification limits during its entire shelf-life. The NF has a high-protein content, although the true protein levels in the NF are overestimated when using the nitrogen-to-protein conversion factor of 6.25, due to the presence of non-protein nitrogen from chitin. The applicant proposed to use the NF in the form of a snack, and as a food ingredient in a number of food products. The target population proposed by the applicant is the general population. The Panel notes that, considering the composition of the NF and the proposed conditions of use, the consumption of the NF is not nutritionally disadvantageous. The Panel notes that no genotoxicity and no subchronic toxicity studies with the NF were provided by the applicant. Considering that no safety concerns arise from the history of use of A. domesticus or from the compositional data of the NF, the Panel identified no other safety concerns than allergenicity. The Panel considers that the consumption of the NF might trigger primary sensitisation to A. domesticus proteins and may cause allergic reactions in subjects allergic to crustaceans, mites and molluscs. Additionally, allergens from the feed may end up in the NF. The Panel concludes that the NF is safe under the proposed uses and use levels.

Safety of frozen and dried formulations from migratory locust (Locusta migratoria) as a Novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Food and Food Allergens (NDA) was asked to deliver an opinion on the safety of frozen and dried formulations from migratory locust (Locusta migratoria) as a novel food pursuant to Regulation (EU) 2015/2283. The term migratory locust refers to the adult of the insect species Locusta migratoria. The NF is proposed in three formulations i) frozen without legs and wings; ii) dried without legs and wings; iii) ground with legs and wings. The main components of the NF are protein, fat and fibre (chitin) in the dried form of the NF, and water, protein, fat and fibre (chitin) in the frozen form of the NF. The Panel notes that the concentration of contaminants in the NF depends on the occurrence levels of these substances in the insect feed. The Panel notes that there are no safety concerns regarding the stability of the NF if the NF complies with the proposed specification limits during its entire shelf-life. The NF has a high protein content, although the true protein levels in the NF are overestimated when using the nitrogen-to-protein conversion factor of 6.25, due to the presence of non-protein nitrogen from chitin. The applicant proposed to use the NF as frozen, dried and ground in the form of snack, and as a food ingredient in a number of food products. The target population proposed by the applicant is the general population. The Panel notes that considering the composition of the NF and the proposed conditions of use, the consumption of the NF is not nutritionally disadvantageous. The submitted history of use and toxicity studies from literature did not raise safety concerns. The Panel considers that the consumption of the NF might trigger primary sensitisation to L. migratoria proteins and may cause allergic reactions in subjects with allergy to crustaceans, mites and molluscs. Additionally, allergens from the feed may end up in the NF. The Panel concludes that the NF is safe under the proposed uses and use levels.

Insect Protein-Based Diet as Potential Risk of Allergy in Dogs

Before insects can be used widely as an alternative source of dietary protein, their allerginicity should be investigated. Therefore, the aim of our study was to assess the potential adverse reactions of the immune system of dogs against Tenebrio molitor proteins. Dogs sensitised to storage mites T. putrescentiae and A. siro were included. Clinically healthy and clinically allergic dogs were compared. Proteins were extracted from mealworm larvae and their digestibility determined by in vitro incubation with digestive proteases. Mealworm protein extracts and digests were analysed by SDS-PAGE. Canine sera tested for the presence of mite-specific IgEs were used for subsequent Western blotting. LC-MS/MS analysis was used to identify mealworm proteins and their allergenic potential was predicted with the AllermatchTM tool. The binding of canine sera IgEs to mealworm proteins was confirmed; however, the differences between the two groups of dogs were not significant. Moreover, no clear correlation was found between sensitisation to storage mites and clinical status of the dogs. Altogether, 17 different proteins were identified, including tropomyosin, α-amylase, and Tm-E1a cuticular protein that are known cross-reacting IgE-binding allergens. Our results suggest that dogs allergic to mites may clinically express also the cross-reactivity with mealworm proteins.