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.

Comparative analysis of allergenicity and predicted linear epitopes in α and ß parvalbumin from turbot (Scophthalmus maximus).

BACKGROUND: Parvalbumin (PV) can be subdivided into two phylogenetic lineages, αPV and ßPV. The bony fish ßPV is considered a major fish allergen. However, there is no available report on the immunological property and epitope mapping of bony fish αPV. RESULTS: To characterize the allergenic property of bony fish αPV and investigate the difference in allergenic property of bony fish αPV and ßPV, turbot (Scophthalmus maximus) αPV and ßPV were identified by mass spectrometry and were expressed in Escherichia coli system in this study. Spectra analysis and three-dimensional (3D) modeling showed the similar structure between αPV and ßPV. However, αPV exhibited lower immunoglobulin E/immunoglobulin G (IgE/IgG) binding capacity than ßPV. Three identified ßPV epitopes possessed higher IgE reactivity and more hydrophobic residues than three identified αPV epitopes. In addition, less similarity in sequence homology of αPV epitopes was observed with allergen sequences in database. CONCLUSION: These finding expanded information on fish PV epitopes and substantiated the difference in allergenicity and epitope mapping between fish αPV and ßPV, which will improve the epitope-based detection tools of PV and diagnostic of PV induced fish allergy. © 2023 Society of Chemical Industry.

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 review on food processing and preparation methods for altering fish allergenicity.

People eat many varieties of food to satiate their hunger. Among them, a few numbers of food cause overreaction of the body's immune system, and fish holds a permanent position on that list. Processing methods, including one treatment or a combination, can have different effects on the allergenic potential of food proteins. An important point to note, however, is that not all of these methods can eliminate the potential for protein allergy. Thus, it is essential to understand the risk involved with the consumption of processed fish and its derivatives. Fish could be prepared in various ways before come to the dining plate. It has shown some of these methods can effectively manipulate the allergenicity owing to the alterations occurred in the protein conformation. This article provides an overview of the impact of fish processing methods (thermal and non-thermal) on the allergenic potential of fish along with possible causative structural modification provokes allergen stability. The article begins with current trends related to fish consumption, proceeds with the prevalence and underlying mechanism of fish allergy. Properties of clinically relevant fish proteins, projected IgE epitopes of PV, cross-reactivity of fish allergens are also addressed in this context to understand and compare the behavioral patterns of PV profiles of different species on processing methods.

The first reptilian allergen and major allergen for fish-allergic patients: Crocodile ß-parvalbumin.

BACKGROUND: Clinical cross-reactivity between bony fish, cartilaginous fish, frog, and chicken muscle has previously been demonstrated in fish-allergic patients. In indicative studies, two reports of anaphylaxis following the consumption of crocodile meat and IgE-cross-binding were linked to the major fish allergen parvalbumin (PV). This study investigates IgE-binding proteins in crocodile meat with a focus on PV and their clinical relevance. METHODS: Proteins were extracted from muscle tissue of crocodile, three bony fish, and two cartilaginous fish. A cohort of fish-allergic pediatric patients (n = 77) underwent allergen skin prick testing (SPT) to three fish preparations (n = 77) and crocodile (n = 12). IgE-binding proteins were identified and quantified by SDS-PAGE, mass spectrometric analyses, and immunoblotting using commercial and in-house antibodies, as well as individual and pooled patients' serum. PV isoforms were purified or recombinantly expressed before immunological analyses, including human mast cell degranulation assay. RESULTS: Of the tissues analyzed, PV was most abundant in heated crocodile preparation, triggering an SPT of ≥3 mm in 8 of 12 (67%) fish-allergic patients. Seventy percent (31 of 44) of fish PV-sensitized patients demonstrated IgE-binding to crocodile PV. Crocodile ß-PV was the major IgE-binding protein but 20-fold less abundant than α-PV. Cellular reactivity was demonstrated for ß-PV and epitopes predicted, explaining frequent IgE-cross-binding of ß-PVs. Both PV isoforms are now registered as the first reptile allergens with the WHO/IUIS (ß-PV as Cro p 1 and α-PV as Cro p 2). CONCLUSION: Fish-allergic individuals may be at risk of an allergy to crocodile and should seek specialist advice before consuming crocodilian meat.

IgE-mediated fish allergy in children: is omega-3 supplementation useful?

The management of fish allergy relies on the elimination of all fish from the diet. Nevertheless, an exclusion diet can be problematic from a paediatric nutritional perspective. The issue of a substitute diet for children suffering from fish allergy seems to be not adequately addressed and the consequences of a fish exclusion diet in paediatric age are not known. Fish has an important nutritional value, it is rich in vitamins of group B, D and A, selenium, calcium and phosphorus, iron, zinc, magnesium, iodine and omega-3. While vitamins and iodine are normally present in the diet, omega-3 is present in few other foods, such as vegetable seed oils and nuts. Hence, the scientific research indicates a generic advice regarding a possible omega-3 supplementation in children with fish allergy. Given the knowledge about omega-3 supplementation having a potential good risk-benefit ratio and the absence of serious adverse events related to the omega-3 supplementation, this type of supplementation may seem advisable in children affected by fish allergy.

Expanding the allergen repertoire of salmon and catfish.

BACKGROUND: Diagnostic tests for fish allergy are hampered by the large number of under-investigated fish species. Four salmon allergens are well-characterized and registered with the WHO/IUIS while no catfish allergens have been described so far. In 2008, freshwater-cultured catfish production surpassed that of salmon, the globally most-cultured marine species. We aimed to identify, quantify, and compare all IgE-binding proteins in salmon and catfish. METHODS: Seventy-seven pediatric patients with clinically confirmed fish allergy underwent skin prick tests to salmon and catfish. The allergen repertoire of raw and heated protein extracts was evaluated by immunoblotting using five allergen-specific antibodies and patients' serum followed by mass spectrometric analyses. RESULTS: Raw and heated extracts from catfish displayed a higher frequency of IgE-binding compared to those from salmon (77% vs 70% and 64% vs 53%, respectively). The major fish allergen parvalbumin demonstrated the highest IgE-binding capacity (10%-49%), followed by triosephosphate isomerase (TPI; 19%-34%) in raw and tropomyosin (6%-32%) in heated extracts. Six previously unidentified fish allergens, including TPI, were registered with the WHO/IUIS. Creatine kinase from salmon and catfish was detected by IgE from 14% and 10% of patients, respectively. Catfish L-lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, pyruvate kinase, and glucose-6-phosphate isomerase showed IgE-binding for 6%-13% of patients. In salmon, these proteins could not be separated successfully. CONCLUSIONS: We detail the allergen repertoire of two highly farmed fish species. IgE-binding to fish tropomyosins and TPIs was demonstrated for the first time in a large patient cohort. Tropomyosins, in addition to parvalbumins, should be considered for urgently needed improved fish allergy diagnostics.

Poor prognosis of food protein-induced enterocolitis syndrome to fish.

BACKGROUND: Fish is the most common causative food of food protein-induced enterocolitis syndrome (FPIES) in Southern Europe. In children with FPIES, the development of tolerance varies according to the culprit food and specifically fish seems to have a poorer prognosis than other solid foods. We sought to evaluate the fish-FPIES resolution rate in children. METHODS: A descriptive retrospective analysis of children with fish-FPIES, followed during the last 20 years, was performed. The offending fish, age and symptoms at onset, the coexistence of atopic diseases and FPIES to other foods were registered. All the children included had undergone an oral food challenge (OFC) with the offending fish. We recorded those children that overcame their fish-FPIES and those that did not outgrow the disease. RESULTS: Seventy children were enrolled in this study (median age: 9 yo; IQR 6.4-13.8). Forty-two (60%) achieved tolerance to the offending fish with a median age of 4 years (IQR: 3-5). Among children ≤5 yo (n = 40), 35 (87.5%) developed tolerance; among 6-8yo (n = 14), 40% developed tolerance; and only 12.5% among those ≥9 yo (n = 16) developed tolerance. Twenty-eight children did not outgrow the disease (median age: 8.9 yo; IQR: 9-13.8). We did not find any statistical differences regarding the offending fish, presence of single vs multiple fish-FPIES, symptoms at the beginning, coexistence of other atopic diseases or the coexistence of other FPIES, between the children who overcame the disease and those who did not. CONCLUSION: One in five children with FPIES to fish will not overcome the disease during childhood.

IgE-Mediated Fish Allergy in Children.

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

Molecular and immunological characterization of grass carp (Ctenopharyngodon idella) parvalbumin Cten i 1: A major fish allergen in Hong Kong.

BACKGROUND: Grass carp is the most commonly consumed fish species in Hong Kong. The allergenicity of grass carp and its allergen content are yet to be reported. This study characterized the major allergen in grass carp and investigated its allergenicity. METHODS: Sixty-nine subjects with history of IgE-mediated allergic reaction to grass carp were recruited. The protein content in steamed grass carp extract was resolved by SDS-PAGE, and the major allergen was identified by immunoblotting with serum from subjects allergic to grass carp. The identity of allergen was elucidated by mass spectrometry and amino acid sequence obtained by amplifying the specific gene from cDNA library of grass carp. The cross-reactivity between parvalbumins from grass carp and other phylogenetically close (common carp) or commercially important (cod and salmon) species was investigated by competitive inhibition ELISA. RESULTS: A major IgE-binding protein was found at approximately 9 kDa and identified as parvalbumin by immunoblotting and mass spectrometry. Grass carp parvalbumin was more allergenic than common carp, salmon, and cod parvalbumins despite sharing high sequence homology. This newly identified major allergenic parvalbumin isoform from grass carp was registered as Cten i 1 in the World Health Organization and International Union of Immunological Societies allergen database. CONCLUSIONS: Grass carp parvalbumin is identified as the major fish allergen in Hong Kong. The strong allergenicity of Cten i 1 contributes to the high IgE reactivity of grass carp. Grass carp, among other fish species, should be considered when managing fish-allergic patients.

IgE reactivity to fish allergens from Pacific cod (Gadus macrocephalus) in atopic dogs.

BACKGROUND: IgE reactivity to fish allergens in atopic dogs, which are used as models for food allergy, has not been elucidated to date. We investigated IgE reactivity to crude extracts and purified allergens derived from the Pacific cod (Gadus macrocephalus) in atopic dogs to identify the allergenic proteins of cod. RESULTS: The levels of specific IgE to crude cod extracts were measured in the sera of 179 atopic dogs, including 27 dogs with cod allergy, using enzyme-linked immunosorbent assay (ELISA). Specific IgE to crude cod extracts were present in 36 (20%) of the 179 atopic dogs and in 12 (44%) of the 27 dogs with cod allergy. The allergens in crude cod extracts were analyzed by ELISA, immunoblotting, and liquid chromatography-tandem mass spectrometry. In allergen component analysis, IgE reactivity to tropomyosin and enolase was observed in the sera of dogs with cod allergy. IgE reactivity to parvalbumin, collagen, and tropomyosin was evaluated using the sera of atopic dogs that tested positive for specific IgE to crude cod extracts. Among the 36 dogs with IgE reactivity to crude cod extracts, 9 (25%), 14 (39%), and 18 (50%) dogs tested positive for specific IgE to parvalbumin, collagen, and tropomyosin, respectively. CONCLUSIONS: The IgE reactivity to cod allergens observed in dogs was similar to that in humans, and this finding further supports the use of atopic dogs with fish allergy as a model for fish allergy in humans.

Role of Recombinant Parvalbumin Gad c 1 in the Diagnosis and Prognosis of Fish Allergy.

BACKGROUND AND OBJECTIVES: The prevalence of fish allergy has increased in recent years. The parvalbumin Gad c 1 is a major cod allergen that is used as a follow-up marker in patients with fish allergy. Objectives: To determine the clinical and laboratory characteristics of a population of patients with fish allergy. To analyze the role of the specific IgE (sIgE) of recombinant Gad c 1 (rGad c 1) and skin prick tests (SPTs) in confirming the acquisition of tolerance to fish. METHODS: We performed a retrospective study of patients with fish allergy from July 1, 2005 to December 31, 2016. The population was characterized according to demographic data, species of fish associated with allergic reactions, and symptoms. The SPT wheal diameter and sIgE for fish and rGad c 1 were evaluated before acquisition of tolerance (T0) and afterwards (T1). RESULTS: The study population comprised 81 patients (68% male). Most reactions were triggered by hake (51%), mackerel (30%), and cod (26%). The most frequent manifestations were urticaria/angioedema (72%), gastrointestinal symptoms (35%), and eczema (33%); 42% of patients experienced anaphylaxis. At T0, the average sIgE values were as follows: cod, 32.2 kUA/L; sardine, 18.4 kUA/L; hake, 17.5 kUA/L; salmon, 13.9 kUA/L; tuna, 4.5 kUA/L; and rGad c 1, 22.9 kUA/L. In patients who acquired tolerance to at least 1 fish species (n=60; 74%), the mean value of rGad c 1 at T1 (5.1 kUA/L) was significantly lower than at T0 (16.8 kUA/L) (P=.001). Significant values were also recorded for the average diameter of the SPT wheal and the evaluations at T0 and T1 for hake (9.42 mm/3.79 mm) and salmon (7.8 mm/2.8 mm) (P=.002 and P=.026, respectively). CONCLUSION: The decrease in sIgE to rGad c 1 and the mean wheal diameter of SPT for hake and salmon can be used as markers of prognosis in the acquisition of tolerance by fish-allergic patients.

Commercial fish ELISA kits have a limited capacity to detect different fish species and their products.

BACKGROUND: Fish is a major food and allergen source, requiring safety declarations on packages. Enzyme-linked immunosorbent assays (ELISAs) are often used to ensure that the product meets the required standards with regard to the presence of allergens. Over 1000 different fish species are traded and consumed worldwide, and they are increasingly provided by aquaculture. Up to 3% of the general population is at risk of sometimes fatal allergic reactions to fish, requiring strict avoidance of this commodity. The aim of this study is to evaluate the capacity of three commercially available ELISA tests to detect a wide variety of bony and cartilaginous fish and their products, which is essential to ensure reliable and safe food labeling. RESULTS: The detection rates for 57 bony fish ranged from 26% to 61%. Common European and North American species, including carp, cod, and salmon species, demonstrated a higher detection rate than those from the Asia-Pacific region, including pangasius and several mackerel and tuna species. Among the 17 canned bony fish products, only 65% to 86% were detected, with tuna showing the lowest rate. None of the cartilaginous fish (n = 9), other vertebrates (n = 8), or shellfish (n = 5) were detected. CONCLUSIONS: We demonstrated that three commercial fish ELISA kits had a limited capacity to detect fish and their products. The complexity of fish as a protein source that is increasingly utilized means that there is an urgent need for improved detection methods. This is crucial for the food industry to provide safe seafood products and comply with international legislation. © 2020 Society of Chemical Industry.

[A CASE OF ANAPHYLAXIS CAUSED BY LANDLOCKED AYU FISH, KOAYU FISH, FROM LAKE BIWA].

A 28-year-old man was transferred to our emergency room for dyspnea and wheals on the entire body. He had eaten landlocked ayu fish (Plecoglossus altivelis) the so-called "koayu fish", from Lake Biwa, and had immediately experienced a stomachache. Wheals and dyspnea developed one hour later and were successfully treated with intravenous corticosteroids. The patient was examined for koayu fish and related allergens by skin prick and allergen-specific immunoglobulin E (IgE) (ImmunoCAP®) tests. Positive skin prick results were obtained for Lake Biwa koayu fish (raw and heated) as well as for standard skin test allergens (prepared by Torii pharmaceuticals) including shrimp, crab, and squid. Negative prick test results were observed for regular ayu fish and other fish such as horse mackerel, sardine, salmon, mackerel, codfish, and tuna. Allergen-specific IgE tests (ImmunoCAP ®) showed positivity for shrimp, crab, ticks, moths, and mosquitoes, while ImmunoCAP® tests were negative for the allergen components rGad c 1 (pollackparvalbumin) and rPen a 1 (shrimp tropomyosin). Moreover, enzyme-linked immunosorbent assay (ELISA) tests were negative for mackerel parvalbumin and collagen. We considered this case to be of anaphylaxis caused by koayu fish from Lake Biwa and speculated that a novel koayu-specific antigen might have been the cause of the condition.

Variability of allergens in commercial fish extracts for skin prick testing.

BACKGROUND: Commercial allergen extracts for allergy skin prick testing (SPT) are widely used for diagnosing fish allergy. However, there is currently no regulatory requirement for standardization of protein and allergen content, potentially impacting the diagnostic reliability of SPTs. We therefore sought to analyse commercial fish extracts for the presence and concentration of fish proteins and in vitro IgE reactivity using serum from fish-allergic patients. METHODS: Twenty-six commercial fish extracts from five different manufacturers were examined. The protein concentrations were determined, protein compositions analysed by mass spectrometry, followed by SDS-PAGE and subsequent immunoblotting with antibodies detecting 4 fish allergens (parvalbumin, tropomyosin, aldolase and collagen). IgE-reactive proteins were identified using serum from 16 children with confirmed IgE-mediated fish allergy, with focus on cod, tuna and salmon extracts. RESULTS: The total protein, allergen concentration and IgE reactivity of the commercial extracts varied over 10-fold between different manufacturers and fish species. The major fish allergen parvalbumin was not detected by immunoblotting in 6/26 extracts. In 7/12 extracts, five known fish allergens were detected by mass spectrometry. For cod and tuna, almost 70% of patients demonstrated the strongest IgE reactivity to collagen, tropomyosin, aldolase A or ß-enolase but not parvalbumin. CONCLUSIONS: Commercial fish extracts often contain insufficient amounts of important allergens including parvalbumin and collagen, resulting in low IgE reactivity. A comprehensive proteomic approach for the evaluation of SPT extracts for their utility in allergy diagnostics is presented. There is an urgent need for standardized allergen extracts, which will improve the diagnosis and management of fish allergy.

A cross-sectional, population-based study on the prevalence of food allergies among children in two different socio-economic regions of Vietnam.

BACKGROUND: There is a paucity of data on the prevalence of food allergy (FA) in Vietnam. A cross-sectional, population-based study was conducted to evaluate the current prevalence of FA among 2- to 6-year-old children in two different regions in Vietnam. METHOD: A structured, anonymous questionnaire, modified from published FA epidemiologic studies and based on EAACI guidelines, was distributed to parents/guardians of participating children in Hue City (urban area) and Tien Giang Province (rural area). Data collected from the survey were statistically analyzed to generate the prevalence of self-reported and doctor-diagnosed FA and overarching pattern of food allergens. RESULTS: A total of 8620 responses were collected (response rate 81.5%). Children in Tien Giang reported more than twice the food-induced adverse reactions seen in children in Hue (47.8% vs. 20.5%). In contrast, children in Hue showed higher self-reported FA (9.8%) and doctor-diagnosed FA rates (8.4%) than children in Tien Giang (7.9% and 5.0%, respectively). Crustacean was the predominant allergy-inducing food in both areas (330 of 580 cases, 56.9%), followed by fish, mollusk, beef, milk, and egg. However, substantial variations of FA patterns were seen between the study sites. Geographic location and co-morbidities of other allergic diseases were key risk factors for FA (P < 0.001). CONCLUSIONS: The prevalence of FA in Vietnamese children seems to be higher than previously reported from other Asian countries. Crustacean is the predominant allergy-inducing food among participating preschool children in Vietnam. The variation of reported food allergen sources across different socio-economic locations could imply different eating habits or the participation of indoor and outdoor allergen exposure.

Retrospective study identified fish and milk as the main culprits in cases of food protein-induced enterocolitis syndrome.

AIM: Food protein-induced enterocolitis syndrome (FPIES) is a non-immunoglobulin E (IgE)-mediated food allergy, which is confined to the gastrointestinal tract and occurs most frequently in the first year of life. Our aim was to examine the clinical features, causative agents and outcomes of Greek children with FPIES. METHODS: This was a five-year (2013-2017) retrospective study, based on chart reviews of 78 children with FPIES from six Greek paediatric allergy centres. RESULTS: Only five children needed an oral food challenge (OFC) for diagnosis, but 54 children (69%) had OFCs to monitor tolerance development. The most common problems were fish and milk, which affected affecting 42 (54%) and 25 (35%) of children, respectively. The median age of tolerance based on the results of the negative OFCs occurred by 34.0 (26.6-58.4) months. Fish and milk were tolerated by 24 (57%) and 13 (52%) of children by 43.8 and 24.3 months, respectively. Coexisting IgE sensitisation to the offending food was related to delayed tolerance. CONCLUSION: Fish and milk were the most common food allergies in our series of Greek children with FPIES. Cases with IgE sensitisation to the food trigger took longer to resolve their allergies.

Hazardous Medications in Children with Egg, Red Meat, Gelatin, Fish, and Cow's Milk Allergy.

Childhood food allergies are a growing public health problem. Once the offending food allergens have been identified, a strict elimination diet is necessary in treatment or prevention of most of the allergic reactions. Accidental food ingestion can lead to severe anaphylaxis. Food- derived substances can be used in medications at various stages of the manufacturing process. In this review, the possible roles of medications which may contain egg, red meat, gelatin, and fish allergens on allergic reactions in children with food allergy were evaluated.

Characterization of Ras k 1 a novel major allergen in Indian mackerel and identification of parvalbumin as the major fish allergen in 33 Asia-Pacific fish species.

BACKGROUND: Fish is a well-recognized cause of food allergy and anaphylaxis. The evolutionary and taxonomic diversity of the various consumed fish species pose a challenge in the identification and characterization of the major fish allergens critical for reliable diagnostics. Globally, fish is a rising cause of food allergy complicated by a large under-investigated variety of species as well as increasing global tourism and trade. This is the first comprehensive study on allergen profiles of heat-processed fish from Vietnam. OBJECTIVE: The aim of this study was to identify the major heat-stable allergens from frequently exported Asia-Pacific freshwater and marine fish and to characterize the major allergen parvalbumin (PV) from one of the most consumed and exported fish species from Asia, the Indian mackerel (Rastrelliger kanagurta). METHODS: Heated protein extracts from 33 fish species were separated by gel electrophoresis. PV isoforms were identified by immunoblotting utilizing 3 different PV-specific monoclonal and polyclonal antibodies and further characterized by mass spectrometry. IgE reactivity was investigated using sera from 21 patients with confirmed fish allergy. RESULTS: Heat-stable IgE-reactive PVs, with up to 5 isoforms per species, were identified in all 33 analysed fish species. In the Indian mackerel, 7 PV isoforms were identified by 2D-gel electrophoresis combined with mass spectrometric analyses. The amino acid sequence deduced from cDNA of the most expressed isoform showed a high identity (>90%) to PVs from 2 other mackerel species. CONCLUSIONS AND CLINICAL RELEVANCE: Different PVs were identified as the major heat-stable allergens in all 33 analysed freshwater and marine fish species from Vietnam, many of which are exported world-wide and 21 species that have never been investigated before. The Indian mackerel PV represents a novel fish allergen, now officially registered as Ras k 1. Improved diagnostics for fish allergy against Asia-Pacific species should be developed with focus on PV.