Prevalence of fish and shellfish allergy: A systematic review

Investigation of conformational and epitope alterations of shrimp tropomyosin under α-dicarbonyl glycation and conformation-allergenicity relationship

The incidence of shrimp-induced food allergy is increasing yearly. Glycation has been reported to reduce shrimp tropomyosin (TM) allergenicity, and how advanced glycation end products (AGEs) impact TM allergenicity has garnered worldwide attention. This work investigated the conformational and epitope alterations of TM under α-dicarbonyl compounds (glyoxal (GO), methylglyoxal (MGO), butanedione (BU)) glycation and conformation-allergenicity relationship. As the results, α-dicarbonyl compounds glycation induced high glycation and TM conformational alterations. AGEs glycation sites on TM epitopes were identified by HPLC-MS/MS, with epitope destruction rates of 62.5 %, 50 % and 62.5 % for GO-TM, MGO-TM and BU-TM, respectively. Immunological results revealed TM glycated by α-dicarbonyls compounds performed weaker IgE binding by 33.38-33.86 %, while GO and MGO reduced IgG binding by 63.60 % and 77.72 %, respectively, suggesting α-dicarbonyls compounds reduced TM allergenicity via AGEs-induced epitope loss and conformational changes. This investigation could provide novel insights into how α-dicarbonyls compounds reduce TM allergenicity and prevent shrimp-induced allergy.

Mollusc and crustacean consumption in the first 1000 days: a scoping review

Mollusc and crustacean consumption in the first 1000 d may improve maternal and child health by providing essential nutrients. However, in some contexts, molluscs and crustaceans have been associated with allergies and environmental contamination, potentially leading to adverse health and development outcomes. It is unclear whether the health benefits of consuming molluscs and crustaceans, collectively classified as shellfish in nutrition, are outweighed by the potential risks to pregnant women and children. We conducted a scoping review (PROSPERO: CRD42022320454) in PubMed, Scopus and EBSCO Global Health of articles published between January 2000 and March 2022 that assessed shellfish consumption during pregnancy, lactation or childhood (0-2 years) in relation to maternal health, child health or child development. A total of forty-six articles were included in this review. Overall, shellfish consumption was associated with higher biomarkers of environmental contaminants, with mercury being the most studied and having the strongest evidence base. The limited research on nutritional biomarker status shows an association between shellfish consumption and iodine status. Preterm birth was not associated with shellfish consumption, but newborn anthropometry showed mixed results, with several studies reporting lower birth weight with higher shellfish consumption. The few studies that examined child development and maternal health outcomes reported no significant associations. This review revealed trade-off health risks and benefits with inclusion of molluscs and crustaceans in the dietary patterns of mothers and young children. More research is needed to understand how these aquatic animal-source foods may be safely consumed and leveraged for improving human nutrition.

Fish Allergenicity Ladder and Parvalbumin Epitopes for Predicting Clinical Cross-Reactivity and Reintroduction in Chinese Population

BACKGROUND

IgE-mediated fish allergy has long been considered an umbrella term due to the high cross-reactivity of parvalbumin, the major fish allergen. Yet, clinical tolerance to certain fish highlights allergenicity differences. In this study, we sought to construct a fish allergenicity ladder and identify fish parvalbumin epitopes to improve the diagnosis of fish allergy.

METHODS

Reported clinical history and the serum-specific IgE (sIgE) responses of 200 Chinese subjects with suspected fish allergy were collected and analyzed, while the relative parvalbumin content in different fish was measured for the construction of a fish allergenicity ladder. Double-blind placebo-controlled food challenge (DBPCFC) and open challenge against salmon, grass carp, and grouper were performed in 58 selected patients for validation of the ladder. Epitope mapping was performed by peptide array against parvalbumins of salmon (both β-1 and β-2), cod, grouper, and grass carp with sera from fish allergic (n = 11), partial fish tolerant (n = 12), and complete fish tolerant (n = 5) patients diagnosed based on oral food challenge outcome.

RESULTS

The distribution pattern of reported history of fish allergy and tolerance, sIgE and molecular data, as well as their strong positive correlation led to the construction of a 3-step fish allergenicity ladder comprising: step 1 of the least allergenic fishes (tuna, halibut, salmon and cod), steps 2 of moderately allergenic fishes (herring and grouper) to step 3 of highly allergenic fishes (catfish, grass carp and tilapia). Epitope mapping revealed one epitope from grouper parvalbumin (AA64-78) for diagnosing general fish allergy and one epitopic region from salmon parvalbumin (AA19-33) as a biomarker of specific fish tolerance. Only epitope-specific IgE differentiated these patients but not sIgE to fish extract or parvalbumin.

CONCLUSION

The fish ladder and epitopes discovery can precisely differentiate fish-allergic and tolerant subjects and guide fish reintroduction by stepping up the ladder, which innovates fish allergy care in the next millennium.

Persistence, Severity, and Reactivity Thresholds in Fish-Allergic Patients Sensitized to Parvalbumin

BACKGROUND

Fish allergy affects children and adults worldwide, and there are transient and persistent phenotypes.

OBJECTIVE

We aimed to analyze persistence, severity, and reactivity thresholds in challenge-confirmed fish-allergic patients sensitized to parvalbumin.

METHODS

Patients 12 to 65 years old reporting immediate reactions to fish, with fish skin prick test ≥5 mm and IgE to cod and carp β-parvalbumins ≥0.70 kUA/L, were recruited in 6 European centers. Except for the case with recent severe anaphylaxis, patients were eligible for a double-blind placebo-controlled food challenge with cod, followed, if negative, by an open food challenge. Severity of reported and elicited reactions was graded with the Food Allergy Severity Score, eliciting dose (ED) was calculated using interval-censoring survival analysis and probabilistic models, and factors associated with a positive challenge and severe reactions were analyzed by logistic regression.

RESULTS

Of 42 patients fulfilling inclusion criteria, fish allergy was confirmed in 30 (71.4%) patients. The median fish allergy duration was 23 years. Although 70% of cases reported anaphylaxis with respiratory or cardiovascular involvement, food challenges resulted in oropharyngeal symptoms (34.7%) or mild systemic reactions (73.9%), with only 1 anaphylaxis with bronchospasm (4.3%). Male sex was associated with severe reactions (odds ratio: 5.44, 95% confidence interval: 1.04-28.53). ED10 for objective symptoms was 0.99 to 2.54 mg of protein. No correlation was found between severity and ED.

CONCLUSIONS

Adolescents and adults with persistent fish allergy linked to parvalbumin sensitization have experienced severe allergic reactions in real life and have a low threshold of reactivity. Our findings support the need for large-scale studies and new therapeutic options for these fish-allergic patients.

Microhomology-mediated end-joining Knock-In approaches to delete the allergenic domain of trout parvalbumin beta-1. Preliminary results in F0 animals and feedback

Background

Gene editing techniques offer new opportunities to improve important traits in aquaculture. The allergenicity of fish flesh is a major problem in aquaculture. Parvalbumin (Parv) is the most prevalent fish allergen. For instance, in salmonids, a single parvalbumin beta-1 protein (parvb1) has been identified as an allergen in specific patients. Therefore, generating trout carrying two parvb1 alleles deleted from the allergenic peptide-encoding region could prevent allergies in these sensitive individuals.

Methods

Here, we describe the application of the Crispr/cas9 system in an attempt to delete parvb1 exon 2 encoding the allergenic peptide and, alternatively, to replace exon 2 of parvb1 with exon2 of parvalbumin beta-2 protein (parvb2,) which does not encode the allergenic peptide. Exon skipping and swapping were pursued through microhomology-mediated end-joining (MMEJ) knock-In using specifically designed double-stranded donor DNA.

Results

Genotyping of approximately 200 F0 fingerlings originating from eggs injected with donor DNA designed for exon 2 skipping led to the identification of only one animal carrying an allele lacking exon 2. Genotyping of approximately 150 fingerlings originating from eggs injected with donor DNA for exon 2 swapping did not result in any trout carrying the expected modified allele.

Conclusions

These preliminary results indicate the potential difficulties associated with the MMEJ KI experiments performed in farmed fish. Finally, new genomic techniques in aquaculture are further discussed in the context of lively debates taking place in the European parliament regarding a possible revision of the current law that determines the legal status of farm animals modified by genome editing. Gene editing, microhomology-mediated end-joining knock-in, parvalbumin, allergenicity, trout, and genetically modified organisms (GMOs).

Recent Advances of Processing and Detection Techniques on Crustacean Allergens: A Review

Crustaceans are delicious and highly nutritional food. However, crustaceans are one of the main food allergens, causing severe public health issues. Thus, it is important to increase the knowledge on crustacean allergens and protect the health of sensitized individuals. This review systematically summarizes the basic information on major crustacean allergens' characteristics, structures, and function. It also summarizes the latest evaluation and detection methods of crustacean allergens. In addition, various processing techniques to alleviate crustacean's allergenicity are discussed and compared. A host of multiplex approaches as innovative research is attractive to decrease crustacean allergenicity. In addition, the strategies to address the risk of crustacean allergens are also reviewed and discussed in detail. This review provides updates and new findings on crustacean allergens, which helps better understand crustacean allergy and provide novel strategies for its prevention and management.

Effect of Maillard reaction on the allergenicity of crude extract of Mactra quadrangularis

Food allergy incidents resulting from the consumption of Mactra quadrangularis is frequently reported. Investigating the impact of the Maillard reaction on the allergenicity of M. quadrangularis allergens is beneficial for the development of hypoallergenic mollusks aquatic products. This study examined the effects of the reaction products (Mactra-Xyl) on the allergenicity using Maillard reaction between crude extract (Mactra) of M. quadrangularis and xylose. The IgE-binding activity with sera from M. quadrangularis allergic patients and allergenicity potential by a mouse food allergy model of Mactra-Xyl were evaluated. Structural changes of Mactra-Xyl were analyzed by UV spectroscopy and surface hydrophobicity assessment, and the amino acid modification sites of the major allergen tropomyosin were further identified using LC-MS/MS. The sera results showed that the IgE-binding activity of Mactra-Xyl was reduced by 56.66 % ± 15.48 % compared to Mactra. In the BALB/c mouse food allergy model, the levels of specific IgE antibody and CD4+IL-4+ cells were significantly decreased, whereas the levels of IgG2a antibody and CD4+IFN-γ+ cells were observably increased in Mactra-Xyl group compared to those observed in Mactra group, thereby alleviating the allergic response. Furthermore, the UV fluorescence intensity and protein surface hydrophobicity of Mactra-Xyl were decreased. LC-MS/MS results revealed that 6 amino acid residues (K21, R77, K86, R140, K189, N202) on 4 IgE epitopes of tropomyosin in Mactra-Xyl were modified, the finding explain the reduced allergenicity of Mactra-Xyl. Therefore, this study provided a theoretical basis for the development of hypoallergenic M. quadrangularis products.

Diagnostic Decision Points of Specific Immunoglobulin E Concentrations for Seafood Allergies in Korean Children: A Nationwide Multicenter Study

Shellfish and fish are common causes of food allergy (FA) in Asia, with significant prevalence rates reported across various countries. This study aimed to identify the diagnostic decision points (DDPs) for shrimp, crab, and cod allergies in Korean children. We enrolled participants aged 18 years or younger with suspected shrimp, crab, or cod allergies through a retrospective review of medical records from a nationwide 14-center study between January 2018 and March 2022. FA was diagnosed using an open oral food challenge or a reproducible and convincing history with positive serum specific immunoglobulin E (sIgE) levels. The sIgE cut-off values for shrimp, crab, and cod were determined by analyzing receiver operating characteristic curves. Out of 266 children, 90 (33.8%) were confirmed to have a shrimp allergy. Crab allergies were found in 37 (39.8%) of 93 children. Of 66 children, 15 (22.7%) were found to be allergic to cod. The optimal sIgE cut-off values based on the largest area under the curve were 1.43, 3.25, and 2.05 kU/L for shrimp, crab, and cod, respectively. Levels of sIgE with more than 90% positive predictive value (PPV) were 33.8, 47.5, and 29.9 kU/L for shrimp, crab, and cod, respectively. Levels of sIgE with greater than 90% negative predictive value (NPV) were 0.36, 0.04, and 3.93 kU/L for shrimp, crab, and cod, respectively. Our results suggest that DDPs of sIgE levels with high PPV and NPV can be used to diagnose shrimp, crab, and cod allergies in Korean children.

Diagnosis and management of shrimp allergy

Shrimp allergy, the most common food allergy in the United States, affects up to 2% of the population. Its etiology is multi-factorial with the combination of genetic predisposition and environmental exposures. This review summarizes the latest diagnosis and management strategies for shrimp allergy. Currently, the double-blind, placebo-controlled food challenge is the gold standard for diagnosis. Moreover, mainstream and experimental management strategies include food allergen avoidance, the FDA-approved omalizumab, and oral immunotherapy. Herein, we emphasize the urgent need to develop more effective diagnostic tools and therapies for shrimp allergy.

Combined Integrative RNA-Seq and Serological sIgE Analysis Enhances Understanding of Fish Allergen Profiles and Diagnostic Strategy for Fish Allergy

Fish allergy is a significant health concern, with diagnosis and management complicated by diverse fish species and allergens. We conducted a comprehensive RNA-seq analysis of eight fish species to identify allergen profiles, integrating ImmunoCAP sIgE data to explore associations with allergen expression and diagnostic performance. Over 30 putative fish allergens were identified, with varying sequence similarities and expression levels, roughly classifying fish into two groups based on parvalbumin (PV) expression. Higher similarities in allergen expression correlated with stronger sIgE data relationships among fish extracts. High PV expression and conserved PV sequences were linked to elevated sIgE measurements, potentially indicating higher allergenicity. For diagnosis, species-specific extract sIgE remained the best indicator of corresponding fish allergy diagnosis, while incorporating multiple sIgE data enhanced performance. In component-resolved diagnosis (CRD), the current panel with PV alone showed comparable performance to fish extract for PV-high fish allergy, while PV-low fish may require the inclusion of more minor allergens for improved CRD accuracy. This RNA-seq allergen analysis helps reveal fish allergen profiles, classify fish groups, and predict allergenicity, potentially improving CRD design and food management in fish allergy.

Molecular Cloning, Prokaryotic Expression, and Immunological Characterization of β-Enolase from Grass Carp (Ctenopharyngodon idella)

β-Enolase is a cross-allergen commonly found in fungi, plants, and aquatic products. Although studies on the allergenicity of fish enolase have been reported in recent years, they are still limited to a few species of marine fish. Therefore, the detection of freshwater fish in the food industry requires more studies of the molecular characterization as well as the allergenicity of enolase. In this study, the nucleotide sequence of β-enolase from grass carp was obtained by molecular cloning technology. Structural domain analysis showed that it contained the characteristic structural domains of the enolase superfamily, and homology analysis indicated that enolases are highly conserved evolutionarily. Recombinant β-enolase was obtained by prokaryotic expression, and its allergenicity was assessed by β-enolase-sensitized mice, which confirmed the ability of β-enolase to trigger an allergic response and cause a rise in Th1 and Th2 immune responses in mice. These results suggest that β-enolase could be used as a characterizing substance for the detection of fish allergens in the food industry as well as the preparation of drugs for allergy-related studies.

Characterization, Epitope Confirmation, and Cross-Reactivity Analysis of Parvalbumin from Lateolabrax maculatus by Multiomics Technologies

Spotted seabass (Lateolabrax maculatus) is the second largest maricultural fish species in China and is the main trigger of food-related allergic reactions. Nevertheless, studies on the allergens of L. maculatus are limited. This study aimed to characterize pan-allergen parvalbumin from L. maculatus. Two proteins of about 11 kDa were purified and confirmed as parvalbumins by mass spectrometry. The IgG- and IgE-binding activities were evaluated through an immunoblotting assay. The molecular characteristics of β-parvalbumin were investigated by combining proteomics, genomics, and immunoinformatics approaches. The results indicated that β-parvalbumin consists of 109 amino acids with a molecular weight of 11.5 kDa and is the major allergen displaying strong IgE-binding capacity. In silico analysis and a dot blotting assay confirmed seven linear B cell epitopes distributed mainly on α-helixes and the calcium-binding loops. In addition, the cross-reactivity among 26 commonly consumed fish species was analyzed. The in-house generated anti-L. maculatus parvalbumin polyclonal antibody recognized 100% of the 26 fish species, demonstrating cross-reactivity and better binding capacity than the anticod parvalbumin antibody. Together, this study provides an efficient protocol to characterize allergens with multiomics methods and supports parvalbumin from L. maculatus as a candidate for fish allergen determination and allergy diagnosis.

Development of Hypoallergenic Derivatives of Cra a 1 with B Cell Epitope Deletion and T Cell Epitope Retention

Tropomyosin was reported as an important allergen in Crassostrea angulata and designated as Cra a 1. The localization of the T cell epitopes and the reduction of the immunoreactivity of Cra a 1 are still lacking. In this study, four T cell epitopes were identified by using wild-type Cra a 1 (wtCra a 1)-immunized mouse splenocytes cultured with synthetic peptides. The immunoreactivity was maintained after chemical denaturation treatment, indicating that the linear epitope is an immunodominant epitope of wtCra a 1. Furthermore, the hypoallergenic derivative (mCra a 1) was developed by the deletion of linear B cell epitopes and retention of T cell epitopes. mCra a 1 could stimulate CD4+T cell proliferation and upregulate interleukin-10 secretion. Overall, basophil activation by mCra a 1 was low, but its ability to induce T cell proliferation was retained, suggesting that mCra a 1 may serve as a viable candidate for treating oyster allergy.

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.

3D bio-printing-based vascular-microtissue electrochemical biosensor for fish parvalbumin detection

A novel 3D bio-printing vascular microtissue biosensor was developed to detect fish parvalbumin quickly. The graphite rod electrode was modified with gold and copper organic framework (Cu-MOF) to improve the sensor properties. Polydopamine-modified multi-wall carbon nanotubes (PDA-MWCNT) were mixed with gelatin methacryloyl (GelMA) to prepare a conductive hydrogel. The conductive hydrogel was mixed with mast cells and endothelial cells to produce a bio-ink for 3D bioprinting. High throughput and standardized preparation of vascular microtissue was performed by stereolithography 3D bioprinting. The vascular microtissue was immobilized on the modified electrode to construct the microtissue sensor. The biosensor's peak current was positively correlated with the fish parvalbumin concentration, and the detection linear concentration range was 0.1 ∼ 2.5 μg/mL. The standard curve equation was IDPV(μA) = 31.30 + 5.46 CPV(μg/mL), the correlation coefficient R2 was 0.990 (n = 5), and the detection limit was 0.065 μg/mL. These indicated a biomimetic microtissue sensor detecting fish parvalbumin has been successfully constructed.

Allergenicity and Linear Epitope Analysis of Scy p 8, an Allergen from Mud Crab

Scy p 8 (triosephosphate isomerase) as a crab allergen in inducing distinct T-helper (Th) cell differentiation and a linear epitope associated with allergenicity remain elusive. In this study, mice sensitized with Scy p 8 exhibited significantly upregulated levels of IgE, IgG1, and IL-4 release, inducing a Th2 immune response. Moreover, the release of IFN-γ (Th1) and the levels of Treg cells were downregulated, while IL-17A (Th17) was upregulated, indicating that Scy p 8 disrupted the Th1/Th2 balance and Th17/Treg balance in mice. Furthermore, bioinformatics prediction and serum samples from crab-allergic patients and mice enabled the discovery of 8 linear epitopes of Scy p 8. Meanwhile, the analysis of peptide similarity and tertiary superposition revealed that 8 epitopes of Scy p 8 exhibited conservation across various species, potentially resulting in cross-reactivity. These findings possess the potential to enhance the comprehension of crab allergens, thereby establishing a foundation for investigating cross-reactivity.

Variation in Shrimp Allergens: Place of Origin Effects on Food Safety Assessment

Due to the widespread use of shellfish ingredients in food products, accurate food labelling is urgently needed for consumers with shellfish allergies. Most crustacean allergen detection systems target the immunorecognition of the allergenic protein tropomyosin. However, this mode of detection may be affected by an origin-dependent protein composition. This study determined if the geographic location of capture, or aquaculture, influenced the allergenic protein profiles of Black Tiger Shrimp (Penaeus monodon), one of the most farmed and consumed shrimp species worldwide. Protein composition was analysed in shrimp from nine different locations in the Asia-Pacific by SDS-PAGE, immunoblotting, and mass spectrometry. Ten of the twelve known shrimp allergens were detected, but with considerable differences between locations. Sarcoplasmic calcium-binding protein, myosin light chain, and tropomyosin were the most abundant allergens in all locations. Hemocyanin-specific antibodies could identify up to six different isoforms, depending on the location of origin. Similarly, tropomyosin abundance varied by up to 13 times between locations. These findings suggest that allergen abundance may be related to shrimp origin and, thus, shrimp origin might directly impact the readout of commercial crustacean allergen detection kits, most of which target tropomyosin, and this should be considered in food safety assessments.

Risk Factors for Severe Seafood Allergy Among Adults in an Urban City in Vietnam

Purpose

Increasing seafood consumption is associated with more frequent reports of food allergy. Little is known about seafood allergy (SFA) among adults in Vietnam. We investigated the characteristics of individuals with SFA and the risk factors for severe SFA.

Patients and methods

A cross-sectional, web-based survey was conducted among individuals aged ≥ 18 years from universities in Ho Chi Minh City (Vietnam) between December 2021 and July 2022. The survey was based on a structured, validated questionnaire related to FA. Strict definitions of "convincing allergy" were used. Multivariate analysis was used to estimate the risk factors for severe SFA after adjusting for covariates. Data were analyzed using JASP (v.0.16.3) and SPSS (v.22.0).

Results

Totally, 1038 out of 2137 (48.57%) individuals completed the questionnaire, of whom 285 (27.46%) had reported SFA. Convincing SFA accounted for 20.13% (209/1038) of the cases, with convincing shellfish allergy being more common than fish allergy. Participants with comorbid shellfish and fish allergy had higher prevalence of atopic dermatitis, peanut/nut allergy, other food allergy, and cutaneous and upper airway symptoms compared to participants with shellfish allergy (p < 0.05). The spectrum of reactive seafood was diverse and characterized by local species. The age of symptom onset was most commonly during late childhood and adolescence, with most reactions persisting into adulthood. A history of anaphylaxis, comorbid peanut, and tree nut allergy, and ≥3 allergens were associated with severe SFA.

Conclusion

Features of causative, coexisting seafood allergy, and risk factors for severe SFA were demonstrated, which can provide a reference for future studies.

Real-World Sensitization and Tolerance Pattern to Seafood in Fish-Allergic Individuals

BACKGROUND

Seafood is a common cause of food allergy and anaphylaxis, but there are limited published real-world data describing the clinical presentation of fish and shellfish allergies.

OBJECTIVE

This study aimed to examine the clinical characteristics, immunological profile, and tolerance pattern to fish, crustaceans, and mollusks in fish-allergic individuals.

METHODS

Patients presenting with IgE-mediated fish allergy between 2016 and 2021 were recruited. A comprehensive sensitization profile including specific IgE and skin prick test to various fish and shellfish species and a detailed clinical history including individuals' recent seafood consumption were evaluated.

RESULTS

A total of 249 fish-allergic individuals (aged 4.2 ± 5.8 years) were recruited from 6 allergy clinics in Hong Kong, and they had experienced their fish-allergic reaction 2.2 ± 3.4 years before enrollment. Seventy-five subjects (30%) reacted to either grass carp, salmon, grouper, or cod in oral food challenges. We identified an IgE sensitization gradient that corresponded to the level of β-parvalbumin in fish. In total, 40% of fish-allergic individuals reported tolerance to 1 or more types of fish, more commonly to fish with a lower β-parvalbumin level such as tuna and salmon, compared with β-parvalbumin-rich fish such as catfish and grass carp. Despite fish and shellfish cosensitization, 41% of individuals reported tolerance to crustaceans, mollusks, or both, whereas shellfish avoidance occurred in half of the fish-allergic individuals, of whom 33% lacked shellfish sensitization.

CONCLUSIONS

Fish allergy commonly presents in early childhood. A considerable proportion of fish-allergic patients are selectively tolerant to certain fish, typically those with lower levels of β-parvalbumin. There is an unmet need to promote precision medicine for seafood allergies.

Local Sources of Protein in Low- and Middle-Income Countries: How to Improve the Protein Quality?

Protein inadequacy is a major contributor to nutritional deficiencies and adverse health outcomes of populations in low- and middle-income countries (LMICs). People in LMICs often consume a diet predominantly based on staple crops, such as cereals or starches, and derive most of their daily protein intakes from these sources. However, plant-based sources of protein often contain low levels of indispensable amino acids (IAAs). Inadequate intake of IAA in comparison with daily requirements is a limiting factor that results in protein deficiency, consequently in the long-term stunting and wasting. In addition, plant-based sources contain factors such as antinutrients that can diminish protein digestion and absorption. This review describes factors that affect protein quality, reviews dietary patterns of populations in LMICs and discusses traditional and novel small- and large-scale techniques that can improve the quality of plant protein sources for enhanced protein bioavailability and digestibility as an approach to tackle malnutrition in LMICs. The more accessible small-scale food-processing techniques that can be implemented at home in LMICs include soaking, cooking, and germination, whereas many large-scale techniques must be implemented on an industrial level such as autoclaving and extrusion. Limitations and considerations to implement those techniques locally in LMICs are discussed. For instance, at-home processing techniques can cause loss of nutrients and contamination, whereas limitations with larger scale techniques include high energy requirements, costs, and safety considerations. This review suggests that combining these small- and large-scale approaches could improve the quality of local sources of proteins, and thereby address adverse health outcomes, particularly in vulnerable population groups such as children, adolescents, elderly, and pregnant and lactating women.

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.

Thermostable allergens in canned fish: Evaluating risks for fish allergy

BACKGROUND

Major fish allergens, including parvalbumin (PV), are heat stable and can withstand extensive cooking processes. Thus, the management of fish allergy generally relies on complete avoidance. Fish-allergic patients may be advised to consume canned fish, as some fish-allergic individuals have reported tolerance to canned fish. However, the safety of consuming canned fish has not been evaluated with comprehensive immunological and molecular analysis of canned fish products.

METHODS

We characterized the in vitro immunoreactivity of serum obtained from fish-allergic subjects to canned fish. Seventeen canned fish products (salmon n = 8; tuna n = 7; sardine n = 2) were assessed for the content and integrity of PV using allergen-specific antibodies. Subsequently, the sIgE binding of five selected products was evaluated for individual fish-allergic patients (n = 53). Finally, sIgE-binding proteins were identified by mass spectrometry.

RESULTS

The canned fish showed a markedly reduced PV content and binding to PV-specific antibodies compared with conventionally cooked fish. However, PV and other heat-stable fish allergens, including tropomyosin and collagen, still maintained their sIgE-binding capacity. Of 53 patients, 66% showed sIgE binding to canned fish proteins. The canned sardine contained proteins bound to sIgE from 51% of patients, followed by canned salmon (43%-45%) and tuna (8%-17%). PV was the major allergen in canned salmon and sardine. Tropomyosin and/or collagen also showed sIgE binding.

CONCLUSION

We showed that canned fish products may not be safe for all fish-allergic patients. Canned fish products should only be considered into the diet of individuals with fish allergy, after detailed evaluation which may include in vitro diagnostics to various heat-stable fish allergens and food challenge conducted in suitable environments.

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.

Ultrasensitive Quantification of Crustacean Tropomyosin by Immuno-PCR

Tropomyosin is the major and predominant allergen among shellfish. This study developed an ultrasensitive immuno-PCR method for the quantification of crustacean tropomyosin in foods. The method couples sandwich ELISA with the real-time PCR (rtPCR) amplification of marker DNAs. Monoclonal anti-TPM antibody was the capture antibody, polyclonal rabbit anti-shrimp tropomyosin antibody was the detection antibody, while natural shrimp tropomyosin served as the standard. A double-stranded amino-DNA was covalently conjugated to a secondary anti-rabbit antibody and subsequently amplified and quantified via rtPCR. The quantification sensitivity of immuno-PCR was 20-fold higher than analogous ELISA, with LOQ 19.8 pg/mL. The developed immuno-PCR method is highly specific for the detection of crustacean tropomyosin and is highly precise in a broad concentration range. Tropomyosin recovery in the spiked vegetable soup was 87.7-115.6%. Crustacean tropomyosin was also quantified in commercial food products. The reported immuno-PCR assay is the most sensitive method for the quantification of crustacean tropomyosin and is the first immuno-PCR-based assay for the quantification of food allergen and food protein in general. The described method could be easily adapted for the specific and ultrasensitive immuno-PCR-based detection of traces of any food allergen that is currently being quantified with ELISA, which is of critical importance for people with food allergies.

Anaphylaxis after Shrimp Intake in a European Pediatric Population: Role of Molecular Diagnostics and Implications for Novel Foods

(1) Background: Tropomyosin is a major cause of shellfish allergy and anaphylaxis triggered by food. It acts as a pan-allergen, inducing cross-reactivity in insects, dust mites, crustaceans, and mollusks. Our study investigates anaphylaxis in children with asthma or atopic diseases after consuming tropomyosin-containing food. (2) Methods: We analyzed the molecular sensitization profiles of pediatric patients at the University of Campania 'Luigi Vanvitelli' from 2017 to 2021, with conditions such as allergic rhinitis, asthma, atopic dermatitis, urticaria, and food allergies. (3) Results: Out of a total of 253 patients aged 1 to 18 years (167 males, 86 females), 21 patients (8.3%) experienced anaphylaxis after shrimp ingestion. All 21 (100%) were sensitized to various tropomyosins: Pen m 1 (100%), Der p 10 (90.5%), Ani s 3 (81%), and Bla g 7 (76.2%). Clinical symptoms included allergic asthma (76.2%), atopic dermatitis (61.9%), urticaria (38.1%), and allergic rhinitis (38.1%). (4) Conclusions: Crustaceans and mollusks are major allergens in Italy and Europe, requiring mandatory declaration on food labels. Italian pediatric patients demonstrated significant anaphylaxis after consuming shrimp, often accompanied by multiple atopic disorders such as asthma, rhinitis, and atopic dermatitis. Considering the cross-reactivity of tropomyosin among various invertebrates and the emergence of 'novel foods' containing insect flours in Europe, there is ongoing debate about introducing precautionary labeling for these products.

IgE-Mediated and Non-IgE-Mediated Fish Allergy in Pediatric Age: A Holistic Approach-A Consensus by Diagnostic Commission of the Italian Society of Pediatric Allergy and Immunology

Fish is one of the "big nine" foods triggering allergic reactions. For this reason, fish allergens must be accurately specified on food labels. Fish allergy affects less than 1% of the world population, but a higher prevalence is observed in pediatric cohorts, up to 7%. Parvalbumin is the main fish allergen found in the muscles. In childhood, sensitization to fish allergens occurs most frequently through the ingestion of fish, rarely transcutaneously or by inhalation. Fish allergy symptoms usually appear within two hours of the allergen contact. The diagnosis begins with the collection of the history. If it is suggestive of fish allergy, prick tests or the measurement of serum-specific IgE should be performed to confirm the suspicion. The oral food challenge is the gold standard for the diagnosis. It is not recommended in case of a severe allergic reaction. It is important to make a differential diagnosis with anisakiasis or scombroid poisoning, which have overlapping clinical features but differ in pathogenesis. Traditionally, managing fish allergy involves avoiding the triggering species (sometimes all bony fish species) and requires an action plan for accidental exposures. The present review will analyze IgE- and non-IgE-mediated fish allergy in children from epidemiology, pathogenesis to clinical features. Moreover, clinical management will be addressed with a particular focus on potential nutritional deficiencies.

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.

Food allergy-A holistic approach to dietary management. A joint EAACI Research & Outreach Committee and INDANA review

Following a diagnosis of IgE-mediated food allergy, to secure the best outcome, the patient should receive individualized advice tailored to their specific needs, which considers the type and presentation of the food involved, level of exclusion required, risk of cross-contamination and any variance required for age, ethnicity, financial issues, and lifestyle. Issues such as food labels "may contain" statements, and variation in the threshold of reaction and impact of cofactors should also be considered. Most important is the need to ensure that the diagnosis is robust, especially given the nutritional, psychological, and socioeconomic issues that can affect an individual with a diagnosis of food allergy. Unnecessary exclusion of one or more foods that have not triggered allergic reactions, especially in individuals with allergic comorbidities, can result in severe IgE-mediated reactions on re-exposure. Given that food allergies may change over time, the diagnosis should be reviewed, to determine whether resolution is likely, or new-food triggers are reported. Regular assessment is vital, especially during childhood, to ensure reintroduction occurs at an appropriate time, thus enabling increased diversity of the diet and improvement in the quality of life. For some, an IgE-mediated food allergy may necessitate the life-long exclusion of foods, and for others, a food habitually eaten suddenly triggers an allergic reaction in adult life. People of all ages, ethnicities, and socioeconomic backgrounds deserve individual advice on the management of their food allergy to support a healthy diet and improve quality of life.

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.

Evaluation of Der p 10 in a Cohort of European Children: Role of Molecular Diagnostics and Clinical Features

BACKGROUND

Allergy toward the dust mite is steadily increasing on the European continent. This sensitization may be a risk factor for developing sensitization to other mite molecules such as tropomyosin Der p 10. This molecule often correlates with food allergy and the risk of anaphylaxis after ingesting mollusks and shrimps.

MATERIALS AND METHODS

We analyzed the sensitization profiles by ImmunoCAP ISAC of pediatric patients from 2017 to 2021. The patients under investigation were being followed for atopic disorders such as allergic asthma and food allergies. The study aimed to analyze the prevalence of sensitization toward Der p 10 in our pediatric population and assess the related clinical symptoms and reactions after ingestion of foods containing tropomyosins.

RESULTS

This study included 253 patients; 53% were sensitized toward Der p 1 and Der p 2; 10.4% were also sensitized to Der p 10. Assessing patients sensitized to Der p 1 or Der p 2, and Der p 10, we observed that 78.6% were affected by asthma (p < 0.005) and had a history of prior anaphylaxis after ingestion of shrimp or shellfish (p < 0.0001).

CONCLUSION

The component-resolved diagnosis gave us a deeper understanding of patients' molecular sensitization profiles. Our study showed that a fair proportion of children sensitive to Der p 1 or Der p 2 are also sensitive to Der p 10. However, many patients sensitized to all three molecules had a high risk of asthma and anaphylaxis. Therefore, the assessment of Der p 10 sensitization should be considered in atopic patients with sensitization to Der p 1 and Der p 2 to avoid encountering possible adverse reactions after ingesting foods containing tropomyosins.

IgE-Mediated Shellfish Allergy in Children

Shellfish, including various species of mollusks (e.g., mussels, clams, and oysters) and crustaceans (e.g., shrimp, prawn, lobster, and crab), have been a keystone of healthy dietary recommendations due to their valuable protein content. In parallel with their consumption, allergic reactions related to shellfish may be increasing. Adverse reactions to shellfish are classified into different groups: (1) Immunological reactions, including IgE and non-IgE allergic reactions; (2) non-immunological reactions, including toxic reactions and food intolerance. The IgE-mediated reactions occur within about two hours after ingestion of the shellfish and range from urticaria, angioedema, nausea, and vomiting to respiratory signs and symptoms such as bronchospasm, laryngeal oedema, and anaphylaxis. The most common allergenic proteins involved in IgE-mediated allergic reactions to shellfish include tropomyosin, arginine kinase, myosin light chain, sarcoplasmic calcium-binding protein, troponin c, and triosephosphate isomerase. Over the past decades, the knowledge gained on the identification of the molecular features of different shellfish allergens improved the diagnosis and the potential design of allergen immunotherapy for shellfish allergy. Unfortunately, immunotherapeutic studies and some diagnostic tools are still restricted in a research context and need to be validated before being implemented into clinical practice. However, they seem promising for improving management strategies for shellfish allergy. In this review, epidemiology, pathogenesis, clinical features, diagnosis, and management of shellfish allergies in children are presented. The cross-reactivity among different forms of shellfish and immunotherapeutic approaches, including unmodified allergens, hypoallergens, peptide-based, and DNA-based vaccines, are also addressed.

IgE Epitope Analysis and Hypo-Immunoreactivity Derivative of Arginine Kinase in Mantis Shrimp (Oratosquilla oratoria)

As the main allergenic food, shrimp can trigger allergic reactions in various degrees. In this study, arginine kinase (AK) was identified as an allergen in Oratosquilla oratoria by LC-MS/MS. The open reading frame of AK was obtained, which included 356 amino acids, and recombinant AK (rAK) was expressed in Escherichia coli. The results of immunological analysis and circular dichroism showed that rAK displayed similar IgG-/IgE-binding activity and structure as native AK. Besides, five IgE linear epitopes of AK were verified by serological analysis, on the basis of which an epitope-deleted derivative was obtained and named as mAK-L. It has been shown that mAK-L displayed hypo-immunoreactivity compared to rAK, and the contents of secondary structures were different. In conclusion, these discoveries enrich the overall understanding of crustacean allergens and epitopes and set the foundations for food allergy diagnosis and immunotherapy.

Study on the Sensitization and Antigenic Epitopes of Tropomyosin from Antarctic Krill (Euphausia superba)

Antarctic krill (Euphausia superba), a shrimp-like marine crustacean, has become a beneficial source of high-quality animal protein. Meanwhile, a special focus has been placed on its potential sensitization issue. In this study, a 35 kDa protein was purified and identified to be Antarctic krill tropomyosin (AkTM) by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The purified TM showed a strong IgE-binding capacity to shrimp/crab-allergic patients' sera, indicating that TM is the primary allergen in Antarctic krill. Simulated gastrointestinal digestion revealed that the digestion stability of TM to pepsin was higher than that to trypsin. The strong degranulation triggered by TM in RBL-2H3 cells suggested that AkTM has a strong sensitization capacity. The TM-sensitized BALB/c mice displayed severe anaphylactic symptoms; high levels of TM-specific IgE, sIgG1, and histamine; and increased IL-4, indicating that AkTM could provoke IgE-mediated allergic reactions. Bioinformatics prediction, indirect competition ELISA, and mast cell degranulation assay were used to map the antigenic epitopes of AkTM. Finally, nine peptides of T_43-58, T_88-101, T_111-125, T_133-143, T_144-155, T_183-197, T_223-236, T_249-261, and T_263-281 were identified as the linear epitopes of AkTM. The findings may help us develop efficient food processing techniques to reduce krill allergy and gain a deeper comprehension of the allergenicity of krill allergens.

Insight into the IgE-binding sites of allergenic peptides of tropomyosin in shrimp (Penaeus chinensis) induced by cold plasma active particles

Tropomyosin (TM) is a major allergen in crustaceans, and its allergenicity mainly depends on epitopes. In this study, the locations of IgE-binding sites between plasma active particles and allergenic peptides of TM in shrimp (Penaeus chinensis) during cold plasma (CP) treatment were explored. Results showed that the IgE-binding ability of two critical peptides (P1 and P2) increased and then decreased by 9.97 % and 19.50 % after 15 min of CP treatment. It was the first time to show that the contribution rate of target active particles was •O > e_(aq)^- > •OH for reducing IgE-binding ability by 23.51 %-45.40 %, and the contribution rates of other long-lived particles including NO₃^- and NO₂^- was about 54.60 %-76.49 %. In addition, Glu131 and Arg133 in P1 and Arg255 in P2 were certified as the IgE sites. These results were helpful for accurately controlling TM allergenicity, shedding more light on allergenicity mitigation during food processing.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Seafood allergy: Allergen, epitope mapping and immunotherapy strategy

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

Identification of Fish Species and Targeted Genetic Modifications Based on DNA Analysis: State of the Art

Food adulteration is one of the most serious problems regarding food safety and quality worldwide. Besides misleading consumers, it poses a considerable health risk associated with the potential non-labeled allergen content. Fish and fish products are one of the most expensive and widely traded commodities, which predisposes them to being adulterated. Among all fraud types, replacing high-quality or rare fish with a less valuable species predominates. Because fish differ in their allergen content, specifically the main one, parvalbumin, their replacement can endanger consumers. This underlines the need for reliable, robust control systems for fish species identification. Various methods may be used for the aforementioned purpose. DNA-based methods are favored due to the characteristics of the target molecule, DNA, which is heat resistant, and the fact that through its sequencing, several other traits, including the recognition of genetic modifications, can be determined. Thus, they are considered to be powerful tools for identifying cases of food fraud. In this review, the major DNA-based methods applicable for fish meat and product authentication and their commercial applications are discussed, the possibilities of detecting genetic modifications in fish are evaluated, and future trends are highlighted, emphasizing the need for comprehensive and regularly updated online database resources.

Detection of Fish Allergens in Foods Using an In-House Real-Time PCR Targeting the Ribosomal 18S rRNA Gene

Fish is one of the major food allergens which, in sensitised individuals, can cause life-threatening allergic reactions, even when present in small amounts. To protect consumers' health, the correct labeling of foods is important. The objective of the present study was to validate an in-house real-time PCR method targeting the ribosomal 18S rRNA gene as universal DNA marker for the detection of fish in foods. The specificity of the primers was assessed on 20 fish species commonly marketed in the Mediterranean basin and other species of molluscs and crustaceans and foods of animal and plant origin. The absolute detection of the method was assessed using DNA extracted from a fish mixture and the SureFood^® QUANTARD Allergen 40 reference material. The relative amount was assessed on a fish and béchamel sauce blend. Commercial food samples either labelled with or without fish in the ingredient list, were tested for the presence of fish DNA. The primer showed high specificity against the selected fish species. The limit of detection (LOD) and limit of quantification (LOQ) of the in-house method were 0.5 pg/µL and 5 pg/µL, respectively. The relative quantification in fish and béchamel blend samples detected a concentration as low as 0.000025%, corresponding to 0.25 mg/kg of fish, indicating the suitability of the method in a food matrix. The presence of fish DNA was always detected in commercial samples in which the presence of fish was listed in the ingredient list. The method was able to detect the presence of fish DNA also in samples in which the presence of fish was indicated as traces or was not declared on the label. The proposed method was demonstrated to be a reliable, specific, and sensitive method for the detection of fish allergens in foods. Therefore, the proposed real-time PCR method could be used as a useful instrument in the verification of compliance with allergen labelling regulations.

Identification of linear epitopes and their major role in the immunoglobulin E-binding capacity of tropomyosin from Alectryonella plicatula

Tropomyosin (TM) is an important allergen in molluscans. However, there was a lack of information about TM as an allergen in oysters. TM was purified and identified from Alectryonella plicatula (ATM), and its primary sequence was cloned and encoded with 284 amino acids (AAs). Chemical denaturants were used to destroy the structure to confirm that linear epitopes played a major role in the immunoglobulin E-binding capacity of ATM. Subsequently, nine linear epitopes were identified using a serological test. The peptide with AA_27-41 was regarded as the key epitope because it could be recognized strongly by most sera of oyster-sensitive individuals in comparison to other epitope peptides. Finally, the epitopes and the primary sequence of TM among shellfish were aligned to find the two conserved epitopes (AA_117-132 and AA_164-178) in oyster, octopus, abalone, scallop, clam, shrimp, and crab. Overall, these data provide a foundation for the allergenicity and cross-reactivity of TM.

Characterization, Epitope Identification, and Cross-reactivity Analysis of Tropomyosin: An Important Allergen of Crassostrea angulata

Oyster is a common shellfish product in China, which is associated with food allergy. However, there is still lack of research on allergens in oysters. In this study, tropomyosin (TM), an important allergen of Crassostrea angulata, was purified and identified by mass spectrometry. Subsequently, TM was cloned and expressed, with a sequence of size 852 bp, encoding 284 amino acid residues. The results of circular dichroism, digestion assay, inhibition enzyme-linked immunosorbent assay, and basophil activation test showed that recombinant TM had similar physicochemical properties and immunological properties to native TM. Furthermore, two conformational mimotopes were obtained and 10 IgE linear epitopes were verified. Meanwhile, different degrees of cross-reactivity were observed between C. angulata TM and the other 8 shellfish TMs using antibodies and serological analysis, which may relate to the 3 conserved epitope regions. These findings are expected to provide a theoretical basis for the molecular diagnosis of oyster allergy and cross-reactivity among shellfish.

A comprehensive overview of emerging processing techniques and detection methods for seafood allergens

Seafood is rich in nutrients and plays a significant role in human health. However, seafood allergy is a worldwide health issue by inducing adverse reactions ranging from mild to life-threatening in seafood-allergic individuals. Seafood consists of fish and shellfish, with the major allergens such as parvalbumin and tropomyosin, respectively. In the food industry, effective processing techniques are applied to seafood allergens to lower the allergenicity of seafood products. Also, sensitive and rapid allergen-detection methods are developed to identify and assess allergenic ingredients at varying times. This review paper provides an overview of recent advances in processing techniques (thermal, nonthermal, combined [hybrid] treatments) and main allergen-detection methods for seafood products. The article starts with the seafood consumption and classification, proceeding with the prevalence and symptoms of seafood allergy, followed by a description of biochemical characteristics of the major seafood allergens. As the topic is multidisciplinary in scope, it is intended to provide information for further research essential for food security and safety.

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

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

Food allergy in children-the current status and the way forward

Food allergy in children is a major health concern, and its prevalence is rising. It is often over-diagnosed by parents, resulting occasionally in unnecessary exclusion of some important food. It also causes stress, anxiety, and even depression in parents and affects the family's quality of life. Current diagnostic tests are useful when interpreted in the context of the clinical history, although cross-sensitivity and inability to predict the severity of the allergic reactions remain major limitations. Although the oral food challenge is the current gold standard for making the diagnosis, it is only available to a small number of patients because of its requirement in time and medical personnel. New diagnostic methods have recently emerged, such as the Component Resolved Diagnostics and the Basophil Activation Test, but their use is still limited, and the latter lacks standardisation. Currently, there is no definite treatment available to induce life-long natural tolerance and cure for food allergy. Presently available treatments only aim to decrease the occurrence of anaphylaxis by enabling the child to tolerate small amounts of the offending food, usually taken by accident. New evidence supports the early introduction of the allergenic food to infants to decrease the incidence of food allergy. If standardised and widely implemented, this may result in decreasing the prevalence of food allergy.