Recognition of an extensive range of IgE-reactive proteins in cod extract

Electrophoretic Behavior in Relation to the Structural Integrity of Codfish Parvalbumin upon Heat Treatment

This work evaluates the impact of heat processing of parvalbumin, a major fish allergen, on the consequences for quantitative analysis of this protein embedded in different matrices during heating (either isolated, in an aqueous extract, or in whole fillets) to assess potential health risks. It is shown that oligomerization of parvalbumin does occur, but only upon heat treatment above 80 °C. This coincides with the ability of the isolated protein to refold up to this temperature in a fully reversible way, as demonstrated by circular dichroism analysis. In autoclaved samples a disintegration of the protein structure is observed. The situation becomes different when parvalbumin is embedded in a matrix with other constituents, as in fish extracts or whole fillets. The electrophoretic analysis of parvalbumin (SDS-PAGE and immunoblotting) is largely determined by complexation with other proteins resulting in insoluble materials caused by the partial unfolding of the parvalbumin at elevated temperatures. This effect is more strongly observed for cod fish extract, compared to whole cod fillets, as in the latter situation the integrity of the tissue hampers this interprotein complexation. Moreover, it is shown by ELISA analysis of heat-treated samples that using blotting procedures where disintegration of complexes may be promoted, restoring some of the IgG-binding propensity, may provide false outcomes. It was concluded that antibody binding to parvalbumin is dominated by the potential to form heat-induced complexes with other proteins. The possibly less-soluble or extractable character of these complexes may provide confusing information regarding potential health risks of fish and fish protein-containing food composites when such heat-treated samples are analyzed by immunochemical assays.

Fish allergens at a glance: variable allergenicity of parvalbumins, the major fish allergens

Fish is a common trigger of severe, food-allergic reactions. Only a limited number of proteins induce specific IgE-mediated immune reactions. The major fish allergens are the parvalbumins. They are members of the calcium-binding EF-hand protein family characterized by a conserved protein structure. They represent highly cross-reactive allergens for patients with specific IgE to conserved epitopes. These patients might experience clinical reactions with various fish species. On the other hand, some individuals have IgE antibodies directed against unique, species-specific parvalbumin epitopes, and these patients show clinical symptoms only with certain fish species. Furthermore, different parvalbumin isoforms and isoallergens are present in the same fish and might display variable allergenicity. This was shown for salmon homologs, where only a single parvalbumin (beta-1) isoform was identified as allergen in specific patients. In addition to the parvalbumins, several other fish proteins, enolases, aldolases, and fish gelatin, seem to be important allergens. New clinical and molecular insights advanced the knowledge and understanding of fish allergy in the last years. These findings were useful for the advancement of the IgE-based diagnosis and also for the management of fish allergies consisting of advice and treatment of fish-allergic patients.

Airborne seafood allergens as a cause of occupational allergy and asthma

Occupational allergy and asthma is a serious adverse health outcome affecting seafood-processing workers. Allergic reactions are directed to two major seafood groups: fish and shellfish, with the latter group comprising crustaceans and molluscs. Several allergenic proteins have been identified in these different groups, but few have been characterised on a molecular level. Parvalbumin appears to be the major fish allergen, while tropomyosin the major crustacean allergen. Other IgE-binding proteins have also been identified in molluscs and other seafood-associated agents (e.g. Anisakis sp), although their molecular nature has not been characterised. Aerosolised allergens can be identified and quantified using immunological and chemical approaches, detecting levels as low as 10 ng/m(3). This contemporary review discusses interesting and recent findings in the area of occupational seafood allergy including high-risk occupations, environmental risk factors for airborne exposures, major and minor allergens implicated and innovative approaches in diagnosing and managing occupational allergy and asthma associated with seafood processing.

Digestibility and IgE-binding of glycosylated codfish parvalbumin

Food-processing conditions may alter the allergenicity of food proteins by different means. In this study, the effect of the glycosylation as a result of thermal treatment on the digestibility and IgE-binding of codfish parvalbumin is investigated. Native and glycosylated parvalbumins were digested with pepsin at various conditions relevant for the gastrointestinal tract. Intact proteins and peptides were analysed for apparent molecular weight and IgE-binding. Glycosylation did not substantially affect the digestion. Although the peptides resulting from digestion were relatively large (3 and 4 kDa), the IgE-binding was strongly diminished. However, the glycosylated parvalbumin had a strong propensity to form dimers and tetramers, and these multimers bound IgE intensely, suggesting stronger IgE-binding than monomeric parvalbumin. We conclude that glycosylation of codfish parvalbumin does not affect the digestibility of parvalbumin and that the peptides resulting from this digestion show low IgE-binding, regardless of glycosylation. Glycosylation of parvalbumin leads to the formation of higher order structures that are more potent IgE binders than native, monomeric parvalbumin. Therefore, food-processing conditions applied to fish allergen can potentially lead to increased allergenicity, even while the protein's digestibility is not affected by such processing.

Physicochemical properties and thermal stability of Lep w 1, the major allergen of whiff

Whiff (Lepidorhombus whiffiagonis) is a fish frequently consumed in Spain. Lep w 1, its major allergen, is a calcium-binding beta-parvalbumin. The resistance of Lep w 1 to heat denaturation and to digestion were studied by circular dichroism spectroscopy and by in vitro gastric digestion systems. Purified Lep w 1 was thermally stable up to 65 degrees C at neutral pH. Calcium depletion resulted in a change of its structure as determined by circular dichroism spectroscopy. A partial loss of structure was also observed at acidic pH; however, the allergen retained its full IgE-binding ability. The partially denatured Lep w 1 was easily digested by pepsin within 2 min. Further, the IgE reactivity of proteins extracted from cooked fish and their stability to proteolysis were analyzed. The extract revealed a higher number of IgE reactive bands than an extract from uncooked fish. IgE binding to these proteins could not be inhibited by an extract from uncooked fish. In contrast to a raw fish extract, the cooked extract showed higher resistance to pepsinolysis. The stability of Lep w 1 to thermal denaturation and digestion explains the high allergenicity of whiff.

Molecular allergology approach to allergic diseases in the paediatric age

Identification, characterization, and purification of allergens are essential for the structural and immunologic studies needed to understand how these molecules induce specific IgE antibody production by the human immune system. Advances in molecular biology techniques have led to the production of recombinant allergens having constant properties, allowing detection of specific IgE directed against different molecular components of an allergenic source. Presence of homologous allergens in different sources is the reason for cross-reaction. Molecule-based diagnostic tools can lead to better interpretation of poly-sensitizations, observed by ST and in vitro tests using allergenic extracts as they were made before. Some examples IgE sensitization to major genuine allergens and panallergens will be presented.

Parvalbumin--the major tropical fish allergen

Fish allergy is common in countries where consumption is high. Asian nations are amongst the world's largest consumers of fish but the allergen profiles of tropical fish are unknown. This study sought to evaluate the allergenicity of four commonly consumed tropical fish, the threadfin (Polynemus indicus), Indian anchovy (Stolephorus indicus), pomfret (Pampus chinensis) and tengirri (Scomberomorus guttatus). Immunoglobulin E (IgE) cross-reactivity with parvalbumin of cod fish (Gad c 1), the major fish allergen, was also studied. Detection of tropical fish and cod specific-IgE was performed by UniCap assay, and skin prick tests were also carried out. The IgE-binding components of tropical fish were identified using IgE immunoblot techniques, and cross-reactivity with Gad c 1 was assessed by ELISA inhibition and IgE immunoblot inhibition. Clinically, nine of 10 patients studied were allergic to multiple fish. All patients exhibited detectable specific-IgE to cod fish (10 of 10 skin prick test positive, eight of 10 UniCap assay positive) despite lack of previous exposure. The major allergen of the four tropical fish was the 12-kDa parvalbumin. IgE cross-reactivity of these allergens to Gad c 1 was observed to be moderate to high in the tropical fish studied. Parvalbumins are the major allergens in commonly consumed tropical fish. They are cross-reactive with each other as well as with Gad c 1. Commercial tests for cod fish appear to be sufficient for the detection of tropical fish specific-IgE.

Changes in the Allergenicity during Different Preparations of Pomfret, Hilsa, Bhetki and Mackerel Fish as Illustrated by Enzyme-Linked Immunosorbent Assay and Immunoblotting

BACKGROUND

Although the identification and characterization of several fish allergens have already been reported, there is almost no data on Indian fish allergens and the effect of thermal processing on their allergenicity. This study aimed at the evaluation of the changes in the level of allergenicity of 4 highly consumed Indian fishes, i.e. pomfret, hilsa, bhetki and mackerel, that occurred after boiling and frying.

METHODS

In this study 110 patients with fish hypersensitivity as evidenced by clinical history and symptoms were recruited based on their positive skin prick test results. The raw, boiled and fried muscle extracts of the 4 fishes were prepared, and each extract was tested by ELISA and immunoblotting with patients' sera.

RESULTS

ELISA and immunoblotting studies demonstrated that the raw muscle extracts of pomfret, hilsa, bhetki and mackerel were allergenic. While the allergenicity of boiled and fried extracts of pomfret and hilsa was considerably reduced, maximum allergenicity of bhetki was demonstrated in the fried extract. The degree of allergenicity of bhetki was demonstrated in the order fried>boiled>raw while that of mackerel followed the order raw>boiled approximately fried.

CONCLUSION

The specific IgE-binding activity and immunoblot profile clearly showed that pomfret and hilsa fish allergens are heat-labile, while allergens of bhetki and mackerel maintained strong reactivity even after thermal treatment.

Seafood allergy: lessons from clinical symptoms, immunological mechanisms and molecular biology

Food allergy consists of a wide range of disorders that result from adverse immune responses to dietary antigens. Manifestations of allergic response includes acute, potentially fatal anaphylactic reactions and a variety of chronic diseases that mainly affect the gastrointestinal tract, skin, and respiratory tract. Tools for clinical diagnosis and management, which have not changed much in the past two decades, include the clinical history, tests for specific IgE antibody to suspected foods, elimination diets, oral food challenges, and provision of medications such as epinephrine for emergency treatment. On the other hand, recent immunological and molecular biological research have enhanced our understanding of the mechanisms of these disorders and revealed the identities of many food allergens. Here, we will discuss seafood allergies with respect to the clinical manifestations, diagnosis, immunological mechanisms, and molecular biology of seafood allergens. Furthermore, potential applications and future directions in the clinical management of seafood allergies are discussed.

Detection of fish antigens aerosolized during fish processing using newly developed immunoassays

BACKGROUND

Aerosolization of fish proteins during seafood processing has been identified as a potential route for allergic sensitization and occupational asthma among workers involved in high-risk activities. The aim of this study was to develop immunological assays for the quantification of aerosolized fish antigens in a fish-processing factory.

METHODS

Polyclonal antibodies to the main fish species processed in the factory (anchovy and pilchard) were generated in rabbits and compared by ELISA inhibition assay and immunoblotting. These antisera were utilized to develop ELISA assays for the detection of fish antigens. The ELISA inhibition assays were evaluated by analyzing environmental air samples collected from three areas in a fish-processing factory: pilchard canning, fish meal production and lobster processing.

RESULTS

By immunoblotting, the rabbit polyclonal antibodies demonstrated IgG antibody binding patterns comparable with IgE antibodies of fish-sensitized patients, particularly in regard to the major fish allergens parvalbumins. The sensitivity of the fish-specific ELISA assays developed was 0.5 microg/ml. The ELISA inhibition assays were able to differentiate between the two different fish species of interest but did not recognize a crustacean species. Notable differences in exposure levels to canned pilchard and anchovy antigens were demonstrated in the three different working areas of the factory, with assays having a detection limit as low as 105 ng/m(3).

CONCLUSION

These ELISA-based assays are sensitive and specific to quantify differential exposure levels to fish antigens produced during fish processing, making it possible to investigate exposure-disease response relationships among workers in this industry.

Clinical tolerance of processed foods

OBJECTIVE

To review the effects of technological processing on selected foods of relevance to childhood allergy from the viewpoints of reduced allergenicity, contamination of processed foods by allergens introduced during processing, and ad hoc technologies to produce reduced hypoallergenic products.

DATA SOURCES

We searched the literature (PubMed/MEDLINE) for articles published between January 1994 and April 2004 using the following keywords: food allergy AND process* OR heat* OR cooking OR toleran*.

STUDY SELECTION

We drew on our collective clinical and biological experience to restrict retrieved studies to those of more frequent relevance to a hospital allergy practice.

RESULTS

Comparatively few clinical studies address the modification of allergenicity of food through cooking or processing. Dairy foods are largely unaffected by processing and may be contaminated by, or themselves become, hidden allergens. Hypoallergenic formulas based on milk, soy, or rice and homogenized beef are successful applications of allergenicity reduction via technological processing. Egg, fish, condiments, and vegetables all carry heat-resistant allergens and should also be considered contaminants. Cereals and bakery products are generally well tolerated, but their allergenicity may be enhanced by processing; the case of rice is still open. Peanut allergens are stable, and the evidence is scant that thermal processing affects the allergenicity of soybean and soy hydrolysates. The debate is ongoing about the tolerance of vegetable oils.

CONCLUSIONS

It is too early to systematize clinical studies based on single procedures. Processing affects antigenicity, but this does not always translate into safety recommendations. Industrial processing is liable to contamination, and monitoring and labeling are industry priorities. Clinicians should evaluate foods by as complete a workup as possible before recommending processed foods.

Cross-reactivity to eel, eelpout and ocean pout in codfish-allergic patients

Fish allergy is one of the most common food allergies in both children and adults and patients with allergic reactions to one fish species have in many cases been given the advice to avoid all fish, without further evaluation. The possible common reactivity between different fish species is not well studied. Because of this and a possible exploitation of fish species hitherto not much used in the Scandinavian diet ocean pout, eelpout and eel were evaluated. We examined the serological and biological cross-reactivity of these species in double-blind challenged-confirmed codfish-allergic patients using CAP, Maxisorp-radio allergosorbent test (RAST) inhibition, western blot, skin prick test (SPT) and histamine release (HR). All 18 codfish allergic patients had specific IgE to ocean pout, eelpout and eel determined by Maxisorp-RAST. All four fish species could induce basophil HR using blood from 16 of 18 patients and all patients tested reacted in SPT. This study demonstrates that patients with a verified clinical allergy to codfish in a high frequency express biological cross-reactivity to other fish species. By RAST inhibition this common reactivity was shown to be a true cross-reactivity.

IgE antibodies of fish allergic patients cross-react with frog parvalbumin

BACKGROUND

The major allergens in fish are parvalbumins. Important immunoglobulin (Ig)E cross-recognition of parvalbumins from different fish species has been shown. Recently frog parvalbumin alpha has been found to be responsible for a case of IgE-mediated anaphylaxis triggered by the ingestion of frog meat. The aim of this study was to investigate whether IgE antibodies of fish allergic persons cross-react with frog parvalbumin and to appreciate its clinical relevance.

METHODS

The sera of 15 fish allergic patients and one fish and frog allergic patient were tested by IgE-immunoblotting against frog muscle extract. Sera were tested against recombinant parvalbumin alpha and beta from Rana esculenta. Skin prick tests were performed in selected patients with recombinant frog parvalbumin. Ca(2+) depletion experiments and inhibition studies with purified cod and frog recombinant parvalbumin were done to characterize the cross-reactive pattern.

RESULTS

Fourteen of the sera tested had IgE antibodies recognizing low molecular weight components in frog muscle extract. Calcium depletion experiments or inhibition of patient sera with purified cod parvalbumin led to a significant or complete decrease in IgE binding. When tested against recombinant parvalbumins, three of 13 sera reacted with alpha parvalbumin and 11 of 12 reacted with beta parvalbumin from R. esculenta. Skin prick tests performed with recombinant frog parvalbumin were positive in fish allergic patients. Inhibition studies showed that a fish and frog allergic patient was primarily sensitized to fish parvalbumin.

CONCLUSION

Cod parvalbumin, a major cross-reactive allergen among different fish species, shares IgE binding epitopes with frog parvalbumin. This in vitro cross-reactivity seems to be also clinically relevant. Parvalbumins probably represent a new family of cross-reactive allergens.

A new oligomeric parvalbumin allergen of Atlantic cod (Gad mI) encoded by a gene distinct from that of Gad cI

BACKGROUND

The major allergen of Baltic cod (Gadus callarias) is a 12.3-kDa parvalbumin with two calcium-binding sites corresponding to EF-hand motifs. Our group found a 24-kDa IgE-reactive band that was also recognized by a monoclonal antiparvalbumin antibody in Atlantic cod (Gadus morhua). Our purpose was to purify and to determine the cDNA deduced sequence of this new cod allergen.

METHODS

Proteins from pre rigor mortis Atlantic cod were separated by gel filtration and the eluted peaks were analysed by SDS-PAGE and Western blotting with sera of sensitized patients and with antiparvalbumin. Protein bands were microsequenced, RNA transcripts were amplified by reverse transcription and polymerase chain reaction (RT-PCR) using primer combinations overlapping the open reading frame.

RESULTS

Four IgE and antiparvalbumin reactive proteins(12.5, 24, 38 and 51 kDa) were detected in gel filtration eluate. The cDNA deduced sequence of the 24 kDa protein had 109 amino acid residues with a molecular weight of 11.5 kDa and a theoretical pI of 4.34. The 24 kDa band corresponded therefore to a dimer of a beta-parvalbumin. Its homology was higher with Sal sI than with Gad cI. This new allergen was named Gad mI.

CONCLUSION

We have characterized a new parvalbumin allergen in Gadus morhua. This protein formed oligomers in native and in reducing conditions. Gad mI and Gad cI may correspond to two distinct genes of Gadus species.

The 18 kDa peanut oleosin is a candidate allergen for IgE-mediated reactions to peanuts

BACKGROUND

Peanut allergy is one of the five most frequent food allergies in children and in adults. Recently, we purified and evaluated the allergenicity of peanut oleosins, a family of small-sized proteins involved in the formation of peanut oil bodies.

METHODS

Allergenicity of the purified native protein and of the recombinant protein was tested by Western blot and by IgE-RIA.

RESULTS

We found IgE-binding with oleosin in 3 of 14 sera of patients who had suffered an allergic reaction to peanuts. Two sera reacted weakly against 16-18 kDa proteins corresponding to oleosin monomers, in Western blot. The main reacting bands had a molecular size estimated at approximately 34 kDa, approximately 50 kDa and approximately 68 kDa and could therefore correspond to oleosin oligomers. IgE reactivity was higher in extracts from roasted peanuts. The same phenomenon occurred with crude soybean oil fraction, with two bands of 16.5 and 24 kDa corresponding to monomers, and two bands of 50 kDa and 76 kDa corresponding to dimers and trimers, respectively. The 18 kDa band was observed in the 3 Western blots of a membrane-enriched fraction of recombinant oleosin produced in the Sf9-baculovirus expression system (performed with the 3 patient sera).

CONCLUSIONS

We have characterized a new peanut allergen which belongs to the oleosins, a family of proteins involved in the formation of oil bodies. The protein may be involved in some of the allergic cross-reactions to peanuts and soybeans.

IgE-binding and cross-reactivity of a new 41 kDa allergen of codfish

BACKGROUND

A 41-kDa IgE-reactive protein (p41) was purified from raw cod extract. This protein is homologous to an aldehyde phosphate dehydrogenase (APDH). The present study aims to evaluate the IgE-binding and the cross-reactivity of this protein in 13 patients allergic to codfish.

METHODS

IgE binding of sera from 13 patients allergic to codfish was tested by Sepharose RIA and by Western blot.

RESULTS

Among the 13 patients, only 4 had specific IgE to APDH detected by APDH-Sepharose RIA. The two patients who had the highest level of specific IgE to human APDH also had a class 5-6 CAP-RAST IgE level to codfish, but two other patients with a class 5 had a negative APDH-Sepharose IgE-RIA. Relative content of APDH was higher in extracts of commercial nonfrozen fish, compared to pre rigor mortis, post rigor mortis and frozen commercial codfish. A high homology of codfish APDH was found with the corresponding human enzyme. A significant inhibition of APDH-Sepharose by human and, to a lesser extent, by rabbit APDH was observed. Western blot of APDH codfish extract showed two bands at 41 and 36 kDa, respectively.

CONCLUSIONS

We have characterized a new allergen from codfish, which had a high level of homology in different species. The p41 relative content of extracts from nonfrozen codfish was higher than in the other samples assessed.

Occupational seafood allergy: a review

BACKGROUND

Recent years have seen increased levels of production and consumption of seafood, leading to more frequent reporting of allergic reactions in occupational and domestic settings. This review focuses on occupational allergy in the fishing and seafood processing industry.

REVIEW

Workers involved in either manual or automated processing of crabs, prawns, mussels, fish, and fishmeal production are commonly exposed to various constituents of seafood. Aerosolisation of seafood and cooking fluid during processing are potential occupational situations that could result in sensitisation through inhalation. There is great variability of aerosol exposure within and among various jobs with reported allergen concentrations ranging from 0.001 to 5.061(microg/m(3)). Occupational dermal exposure occurs as a result of unprotected handling of seafood and its byproducts. Occupational allergies have been reported in workers exposed to arthropods (crustaceans), molluscs, pisces (bony fish) and other agents derived from seafood. The prevalence of occupational asthma ranges from 7% to 36%, and for occupational protein contact dermatitis, from 3% to 11%. These health outcomes are mainly due to high molecular weight proteins in seafood causing an IgE mediated response. Cross reactivity between various species within a major seafood grouping also occurs. Limited evidence from dose-response relations indicate that development of symptoms is related to duration or intensity of exposure. The evidence for atopy as a risk factor for occupational sensitisation and asthma is supportive, whereas evidence for cigarette smoking is limited. Disruption of the intact skin barrier seems to be an important added risk factor for occupational protein contact dermatitis.

CONCLUSION

The range of allergic disease associated with occupational exposure to crab is well characterised, whereas for other seafood agents the evidence is somewhat limited. There is a need for further epidemiological studies to better characterise this risk. More detailed characterisation of specific protein antigens in aerosols and associated establishment of dose-response relations for acute and chronic exposure to seafood; the respective roles of skin contact and inhalational exposure in allergic sensitisation and cross reactivity; and the contribution of host associated factors in the development of occupational seafood allergies are important areas for future research.

IgE antibody to fish gelatin (type I collagen) in patients with fish allergy

BACKGROUND

Most children with anaphylaxis to measles, mumps, and rubella vaccines had shown sensitivity to bovine gelatin that was included in the vaccines. Recently, it was found that bovine type I collagen, which is the main content in the gelatin, is a major allergen in bovine gelatin allergy. Fish meat and skin also contain type I collagen.

OBJECTIVE

The present study was designed to investigate IgE antibody to fish gelatin in children with fish allergy.

METHODS

Serum samples were taken from patients in 3 groups: (1) 10 patients with fish allergy and specific IgE to fish meat; (2) two patients with allergies to both fish meat and bovine gelatin and specific IgE to fish meat and bovine gelatin; and (3) 15 patients with atopic dermatitis and specific IgE to fish meat. Various fish gelatins (type I collagen) were prepared from fish skin. IgE antibody to fish gelatin was analyzed by using ELISA and immunoblotting.

RESULTS

Of 10 patients with fish allergy, 3 had specific IgE to fish gelatin. Of two patients with fish allergy and bovine gelatin allergy, all had specific IgE to fish gelatin. Of 15 patients with atopic dermatitis and specific IgE to fish meat, 5 had specific IgE to fish gelatin. Furthermore, IgE from pooled serum of the patients reacted with both the alpha1 and alpha2 chains of fish type I collagen in immunoblots. There is cross-reactivity among gelatins from various fishes, but there is little cross-reactivity between fish and bovine gelatins.

CONCLUSION

Some fish-sensitive patients possessed IgE antibody to fish gelatin. Fish gelatin (type I collagen) might be an allergen in subjects with fish allergy.