Sarcoplasmic calcium-binding protein is an EF-hand–type protein identified as a new shrimp allergen

Clinical and immunochemical profiles of food challenge proven or anaphylactic shrimp allergy in tropical Singapore

BACKGROUND

Shellfish allergy in Singapore is highly prevalent, and shrimp allergy is the most common.

OBJECTIVE

This study aims to evaluate the clinical characteristics and immunological phenotype of shellfish allergy in this population.

METHODS

Patients with self-reported shellfish allergy were recruited from outpatient clinics of three large hospitals and from a population survey. Open oral food challenges (OFC) to glass prawn (Litopenaeus vannamei) and tiger prawn (Penaeus monodon) were carried out on all patients except for those who had a history of severe anaphylaxis. Skin prick tests (SPT) and specific IgE to crude and recombinant allergens were carried out to evaluate shrimp and dust mite sensitization. Immunoblots were used to assess IgE-binding proteins.

RESULTS

The 104 patients recruited were categorized into shellfish allergic (SA) when OFC was positive or had a history of severe anaphylaxis (n = 39), shellfish tolerant (ST) when OFC was negative (n = 27), and house dust mite positive controls (HDM(+) ) who were ST (n = 38). Oral symptoms (87.1%) were the predominant clinical manifestation. Positive challenge doses ranged from 2 to 80 g of cooked shrimp, with 25/52 patients reacting to either one or both shrimps challenged. The presence of specific IgE to shrimp either by SPT and/or ImmunoCAP(®) assay provided diagnostic test sensitivity of 82% and specificity of 22.2%. The inclusion of specific IgE to shrimp tropomyosin and IgE immunoblots with shrimp extracts did not improve the diagnostic proficiency substantially.

CONCLUSIONS AND CLINICAL RELEVANCE

This study highlights the predominance of oral symptoms in shrimp allergy in tropical Asia and that a high provocation dose may be necessary to reveal shrimp allergy. Furthermore, specific IgE diagnostic tests and immunoblots were of limited use in this population.

Common food allergens and their IgE-binding epitopes

Food allergy is an adverse immune response to certain kinds of food. Although any food can cause allergic reactions, chicken egg, cow's milk, wheat, shellfish, fruit, and buckwheat account for 75% of food allergies in Japan. Allergen-specific immunoglobulin E (IgE) antibodies play a pivotal role in the development of food allergy. Recent advances in molecular biological techniques have enabled the efficient analysis of food allergens. As a result, many food allergens have been identified, and their molecular structure and IgE-binding epitopes have also been identified. Studies of allergens have demonstrated that IgE antibodies specific to allergen components and/or the peptide epitopes are good indicators for the identification of patients with food allergy, prediction of clinical severity and development of tolerance. In this review, we summarize our current knowledge regarding the allergens and IgE epitopes in the well-researched allergies to chicken egg, cow's milk, wheat, shrimp, and peanut.

Purification, Characterization, and Analysis of the Allergenic Properties of Myosin Light Chain in Procambarus clarkii

Myosin light chain (MLC) plays a vital role in cell and muscle functions and has been identified as an allergen in shrimp. In this study, MLC with a molecular mass of 18 kDa was purified from crayfish (Procambarus clarkii) muscle. Its physicochemical characterization showed that the purified MLC is a glycoprotein with 4.3% carbohydrate, highly stable to heat, acid-alkali, and digestion, and weakly retains IgE-binding activity when its secondary structure was altered. Serological assays suggested that conformational epitopes predominate over linear epitopes in the purified MLC. Two isoforms of the MLC gene (MLC1 and MLC2) were cloned, and the purified MLC was identified as MLC1. Analysis of the secondary and tertiary structures of the MLCs indicated that MLC1 has four conformational epitopes and three linear epitopes, whereas MLC2 had a major conformational epitope and three linear epitopes. These results are significant for understanding hypersensitization of humans to crayfish.

Shellfish and House Dust Mite Allergies: Is the Link Tropomyosin?

Crustacean shellfish allergy is an important cause of food allergy and anaphylaxis in Asia. The major allergen in shellfish allergy is tropomyosin, a pan-allergen that is also found in house dust mites and cockroaches. Tropomyosins from house dust mites (HDMs) have a high sequence homology to shellfish tropomyosins, and cross-reactivity between HDM and shrimp tropomyosins has been demonstrated. Exposure to inhaled tropomyosins from house dust mites has been postulated to be the primary sensitizer for shellfish allergy, in a reaction analogous to the oral allergy (inhalant-food) syndrome. This notion is supported by indirect data from the effects of HDM immunotherapy on shellfish allergy, and strong correlations of shellfish and HDM sensitization. HDM immunotherapy has been reported to induce both shrimp allergy in non-allergic patients and shrimp tolerance in shrimp-allergic patients. Epidemiological surveys have also demonstrated a strong correlation between shellfish and HDM sensitization in both hospital-based and community-based studies. Unexposed populations have also been shown to develop sensitization-shellfish sensitization in orthodox Jews with no history of shellfish consumption was associated with HDM sensitization. Reciprocally, HDM sensitization in an Icelandic population living in a HDM-free environment was associated with shrimp sensitization. In vitro IgE inhibition studies on sera in shrimp-allergic Spanish patients indicate that mites are the primary sensitizer in shrimp-allergic patients living in humid and warm climates. Current data supports the hypothesis that tropomyosin is the link between HDM and shellfish allergies. The role of tropomyosin in HDM and shellfish allergies is a fertile field for investigation as it may provide novel immunotherapeutic strategies for shellfish allergy.

Molecular Diagnosis of Shrimp Allergy: Efficiency of Several Allergens to Predict Clinical Reactivity

BACKGROUND

The diagnosis of shellfish allergy remains a challenge for clinicians. Several shellfish allergens have been characterized and their IgE epitopes identified. However, the clinical relevance of this sensitization is still not clear.

OBJECTIVE

The objective of this study was to identify allergens and epitopes associated with clinical reactivity to shrimp.

METHODS

Shrimp-sensitized subjects were recruited and grouped based on the history of shrimp-allergic reactions and challenge outcome. IgE reactivity to recombinant crustacean allergens, and IgE and IgG4 reactivity to peptides were determined. Subjects sensitized to dust mites and/or cockroach without shrimp sensitization or reported allergic reactions, as well as nonatopic individuals, were used as controls.

RESULTS

A total of 86 subjects were recruited with a skin prick test to shrimp; 74 reported shrimp-allergic reactions, 58 were allergic (38 positive double-blind placebo-controlled food challenge and 20 recent anaphylaxis), and 16 were tolerant. All subjects without a history of reactions had negative challenges. The individuals with a positive challenge more frequently recognized tropomyosin and sarcoplasmic calcium-binding proteins than those found tolerant by the challenge. Especially a sarcoplasmic-calcium-binding-protein positive test is very likely to result in a positive challenge, though the frequency of recognition is low. Subjects with dust mite and/or cockroach allergy not sensitized to shrimp recognized arginine kinase and hemocyanin. Several epitopes of these allergens may be important in predicting clinical reactivity.

CONCLUSION

Tropomyosin and sarcoplasmic-calcium-binding-protein sensitization is associated with clinical reactivity to shrimp. Myosin light chain testing may help in the diagnosis of clinical reactivity. Arginine kinase and hemocyanin appear to be cross-reacting allergens between shrimp and arthropods. Detection of IgE to these allergens and some of their epitopes may be better diagnostic tools in the routine workup of shrimp allergy.

Current immunological and molecular biological perspectives on seafood allergy: a comprehensive review

Seafood is an important component in human diet and nutrition worldwide. However, seafood also constitutes one of the most important groups of foods in the induction of immediate (type I) food hypersensitivity, which significantly impacts the quality of life and healthcare cost. Extensive efforts within the past two decades have revealed the molecular identities and immunological properties of the major fish and shellfish allergens. The major allergen involved in allergy and cross-reactivity among different fish species was identified as parvalbumin while that responsible for shellfish (crustaceans and mollusks) allergy was identified as tropomyosin. The cloning and expression of the recombinant forms of these seafood allergens facilitate the investigation on the detailed mechanisms leading to seafood allergies, mapping of IgE-binding epitopes, and assessment of their allergenicity and stability. Future research focusing on the immunological cross-reactivity and discovery of novel allergens will greatly facilitate the management of seafood allergies and the design of effective and life-long allergen-specific immunotherapies.

Immunization with Hypoallergens of shrimp allergen tropomyosin inhibits shrimp tropomyosin specific IgE reactivity

Designer proteins deprived of its IgE-binding reactivity are being sought as a regimen for allergen-specific immunotherapy. Although shrimp tropomyosin (Met e 1) has long been identified as the major shellfish allergen, no immunotherapy is currently available. In this study, we aim at identifying the Met e 1 IgE epitopes for construction of hypoallergens and to determine the IgE inhibitory capacity of the hypoallergens. IgE-binding epitopes were defined by three online computational models, ELISA and dot-blot using sera from shrimp allergy patients. Based on the epitope data, two hypoallergenic derivatives were constructed by site-directed mutagenesis (MEM49) and epitope deletion (MED171). Nine regions on Met e 1 were defined as the major IgE-binding epitopes. Both hypoallergens MEM49 and MED171 showed marked reduction in their in vitro reactivity towards IgE from shrimp allergy patients and Met e 1-sensitized mice, as well as considerable decrease in induction of mast cell degranulation as demonstrated in passive cutaneous anaphylaxis assay. Both hypoallergens were able to induce Met e 1-recognizing IgG antibodies in mice, specifically IgG2a antibodies, that strongly inhibited IgE from shrimp allergy subjects and Met e 1-sensitized mice from binding to Met e 1. These results indicate that the two designer hypoallergenic molecules MEM49 and MED171 exhibit desirable preclinical characteristics, including marked reduction in IgE reactivity and allergenicity, as well as ability to induce blocking IgG antibodies. This approach therefore offers promises for development of immunotherapeutic regimen for shrimp tropomyosin allergy.

Next generation of food allergen quantification using mass spectrometric systems

Food allergies are increasing worldwide and becoming a public health concern. Food legislation requires detailed declarations of potential allergens in food products and therefore an increased capability to analyze for the presence of food allergens. Currently, antibody-based methods are mainly utilized to quantify allergens; however, these methods have several disadvantages. Recently, mass spectrometry (MS) techniques have been developed and applied to food allergen analysis. At present, 46 allergens from 11 different food sources have been characterized using different MS approaches and some specific signature peptides have been published. However, quantification of allergens using MS is not routinely employed. This review compares the different aspects of food allergen quantification using advanced MS techniques including multiple reaction monitoring. The latter provides low limits of quantification for multiple allergens in simple or complex food matrices, while being robust and reproducible. This review provides an overview of current approaches to analyze food allergens, with specific focus on MS systems and applications.

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

BACKGROUND

The increasing consumption of shellfish can cause an increase in allergic symptoms. Shrimp allergy can be species specific, but specific allergies in different organs have not been studied. Identification of allergens in muscle and others organs of banana shrimp is necessary for improved diagnostics of allergies for shrimp and food safety control.

OBJECTIVE

To identify the IgE-binding proteins in various organs of Fenneropenaeus merguiensis by immunoblotting and tandem mass spectrometry.

METHODS

Proteomic methods were used to investigate the allergenic proteins from banana shrimp. Proteins from muscle and various organs were separated by denaturing polyacrylamide gel electrophoresis. Allergens were analyzed by immunoblotting with pooled sera from shrimp allergic patients (n = 21) and tandem mass spectrometry.

RESULTS

The important allergens in banana shrimp are arginine kinase, sarcoplasmic calcium-binding protein, myosin heavy chain, hemocyanin, enolase, and glyceraldehyde-3-phosphate dehydrogenase, which can be demonstrated by immunoblotting in muscle and shell. Moreover, vitellogenin, ovarian peritrophin 1 precursor, β-actin, and 14-3-3 protein were suggested as allergens in the ovary at different stages of ovarian development.

CONCLUSION

Ten allergens were identified as allergens in various organs, and they are suggested as novel allergens in banana shrimp. The major allergen in muscle and shell from this shrimp is arginine kinase, whereas the major allergen in the ovary is vitellogenin.

New shrimp IgE-binding proteins involved in mite-seafood cross-reactivity

SCOPE

Shrimp is a seafood consumed worldwide and the main cause of severe allergenic reactions to crustaceans. Seafood allergy has been related to mite sensitization, mainly mediated by tropomyosin, but other proteins could be involved. The aim of the study was to identify new shrimp allergens implicated in mite-seafood cross-reactivity (CR) in two different climate populations: dry and humid climates.

METHODS AND RESULTS

Shrimp and mite IgE-binding profiles of patients from continental dry and humid climates were analyzed by immunoblotting, and the most frequently recognized Solenocera melantho shrimp proteins were identified by MS as α-actinin, β-actin, fructose biphosphate aldolase, arginine kinase, sarcoplasmic calcium-binding protein, and ubiquitin. Using inhibition immunoblot assays, we demonstrate that tropomyosin and ubiquitin were responsible for mite-seafood CR from both climates; but also α-actinin and arginine kinase are implicated in dry- and humid-climate populations, respectively. Reciprocal inhibition assays demonstrated that mites are the primary sensitizer in humid-climate, as shrimp is in continental dry-climate population.

CONCLUSION

Several new shrimp allergens have been identified and should be considered in the diagnosis and treatment of shrimp allergy and mite-seafood CR. Differences in mite-seafood CR were founded to be based on the climate.

A 24-48 h fed Amblyomma americanum tick saliva immuno-proteome

BACKGROUND

Multiple tick saliva proteins, the majority of which are unknown, confer tick resistance in repeatedly infested animals. The objective of this study was to identify the 24-48 h fed Amblyomma americanum tick saliva immuno-proteome. The 24-48 h tick-feeding phase is critical to tick parasitism as it precedes important events in tick biology, blood meal feeding and disease agent transmission. Fed male, 24 and 96 h fed female phage display cDNA expression libraries were biopanned using rabbit antibodies to 24 and 48 h fed A. americanum female tick saliva proteins. Biopanned immuno-cDNA libraries were subjected to next generation sequencing, de novo assembly, and bioinformatic analysis.

RESULTS

More than 800 transcripts that code for 24-48 h fed A. americanum immuno-proteins are described. Of the 895 immuno-proteins, 52% (464/895) were provisionally identified based on matches in GenBank. Of these, ~19% (86/464) show high level of identity to other tick hypothetical proteins, and the rest include putative proteases (serine, cysteine, leukotriene A-4 hydrolase, carboxypeptidases, and metalloproteases), protease inhibitors (serine and cysteine protease inhibitors, tick carboxypeptidase inhibitor), and transporters and/or ligand binding proteins (histamine binding/lipocalin, fatty acid binding, calreticulin, hemelipoprotein, IgG binding protein, ferritin, insulin-like growth factor binding proteins, and evasin). Others include enzymes (glutathione transferase, cytochrome oxidase, protein disulfide isomerase), ribosomal proteins, and those of miscellaneous functions (histamine release factor, selenoproteins, tetraspanin, defensin, heat shock proteins).

CONCLUSIONS

Data here demonstrate that A. americanum secretes a complex cocktail of immunogenic tick saliva proteins during the first 24-48 h of feeding. Of significance, previously validated immunogenic tick saliva proteins including AV422 protein, calreticulin, histamine release factor, histamine binding/lipocalins, selenoproteins, and paramyosin were identified in this screen, supporting the specificity of the approach in this study. While descriptive, this study opens opportunities for in-depth tick feeding physiology studies.

Allergen component specific ige measurement with the Immulite™ 2000 system: diagnostic accuracy and intermethod comparison

BACKGROUND

The identification of the allergenic molecules, associated to the advances in the field of recombinant allergens, led to the development of a new concept in allergy diagnosis called component-resolved diagnosis. The aim of our study was to evaluate the diagnostic accuracy of different allergen components using the full automatic singleplex quantitative platform Immulite™ 2000.

METHODS

One hundred ninety-five allergic outpatients (35 to olive pollen, 35 to birch pollen, 35 to profilin, 35 to house dust mites, 35 to peach, and 20 to shrimp) and 20 negative controls were enrolled for the study. Bet v 1, Bet v 2, Ole e 1, Der p 1, Der p 2, Der f 1, Der f 2, Pru p 3, tropomyosin were tested both with Immulite™ 2000 and ImmunoCAP™ (Thermo Fisher Scientific, Uppsala, Sweden).

RESULTS

Sensitivity of allergen-specific Immunoglobulin E (sIgE) to Ole e 1, Bet v 1, Der p 1, Der p 2, Der f 1, Der f 2, Pen m 1, and Pru p 3 with Immulite™ 2000 was 100%, 100%, 77.1%, 94.3%, 71.4%, 94%, 75%, and 97.1%, respectively, and the specificity was 100% for all the allergens. The overall agreement between Immulite™ 2000 and ImmunoCAP™ (Thermo Fisher Scientific) platforms was 98.6% (Cohen's kappa = 0.979; confidence interval [CI] 95%: 0.960-0.997). From moderate to strong, positive linear correlations between the assays (r(2) from 0.322 to 0.860, and Spearman's rho from 0.824 to 0.971) were showed.

CONCLUSIONS

A high diagnostic accuracy of the sIgE to allergen components measurement with Immulite™ 2000 and a high agreement with ImmunoCAP™ platforms were shown in this study.

Effect of heat processing on antibody reactivity to allergen variants and fragments of black tiger prawn: A comprehensive allergenomic approach

SCOPE

Prawn allergy is one of the leading causes of IgE-mediated hypersensitivity to food. Alterations of IgE-antibody reactivity to prawn allergens due to thermal processing are not fully understood. The aim of this study was to analyze the impact of heating on prawn allergens using a comprehensive allergenomic approach.

METHODS AND RESULTS

Proteins from raw and heat-processed black tiger prawn (Penaeus monodon) extracts as well as recombinant tropomyosin (rPen m1) were analyzed by SDS-PAGE and immunoblotting using sera from 16 shellfish allergic patients. IgE antibody binding proteins were identified by advanced mass spectroscopy, characterized by molecular structure analysis and their IgE reactivity compared among the prepared black tiger prawn extracts. Heat processing enhanced the overall patient IgE binding to prawn extracts and increased recognition of a number of allergen variants and fragments of prawn allergens. Allergens identified were tropomyosin, myosin light chain, sarcoplasmic calcium binding protein, and putative novel allergens including triose phosphate isomerase, aldolase, and titin.

CONCLUSION

Seven allergenic proteins are present in prawns, which are mostly heat-stable and form dimers or oligomers. Thermal treatment enhanced antibody reactivity to prawn allergens as well as fragments and should be considered in the diagnosis of prawn allergy and detection of crustacean allergens in processed food.

Alpha-actinin is a new type of house dust mite allergen

Main indoor allergens for humans are from house dust mites. There are more than 30 allergens in Dermatophagoides farinae but only fourteen allergens have been identified from this mite including Der f 1–3, 6, 7, 10, 11, 13–18, and 22. A native allergen protein (Der f 24, 90 kDa) was purified from D. farinae by gel filtration and anionic exchange liquid chromatography combined with IgE immunodetection. Its primary structure was determined by Edman degradation, mass spectrometry analysis and cDNA cloning. Enzyme-linked immunosorbent assay inhibition tests (ELISA-IT), immunoblots, basophil activation test (BAT) and skin prick test (SPT) were performed to evaluate the allergenicity. It was identified as an alpha (α)-actinin containing a CaM-like domain with EF-hand motifs. Der f 24 reacted to sera from 85.4% (35/41) of patients on western blot analysis. It reduced ∼20% sera IgE reactivity to D. farinae extracts on a competitive ELISA. Eighty percent (8/10) of patients with D. farinae allergy showed positive reactions to Der f 24 in skin prick test. The expression of CD63 on basophils from patients was up-regulated by Der f 24 by ∼5.4-fold. Alpha-actinin was identified as a new type of house dust mite allergen. To the best of our knowledge, this is the first report of α-actinin as an allergen.

Comprehensive proteomics approach in characterizing and quantifying allergenic proteins from northern shrimp: toward better occupational asthma prevention

Occupational asthma is a major chronic health dilemma among workers involved in the seafood industry. Several proteins notoriously known to cause asthma have been reported in different seafood. This work involves the application of an allergenomics strategy to study the most potent allergens of northern shrimp. The proteins were extracted from shrimp tissue and profiled by gel electrophoresis. Allergenic proteins were identified based on their reactivity to patient sera and were structurally identified using tandem mass spectrometry. Northern shrimp tropomyosin, arginine kinase, and sarcoplasmic calcium-binding protein were found to be the most significant allergens. Multiple proteolytic enzymes enabled 100% coverage of the sequence of shrimp tropomyosin by tandem mass specrometry. Only partial sequence coverage was obtained, however, for the shrimp allergen arginine kinase. Signature peptides, for both tropomyosin and arginine kinase, were assigned and synthesized for use in developing the multiple reaction monitoring tandem mass spectrometric method. Subsequently, air samples were collected from a shrimp processing plant and two aerosolized proteins quantified using tandem mass specrometry. Allergens were detected in all areas of the plant, reaching levels as high as 375 and 480 ng/m(3) for tropomyosine and arginine kinase, respectively. Tropomyosine is much more abundant than arginine kinase in shrimp tissues, so the high levels of arginine kinase suggest it is more easily aerosolized. The present study shows that mass spectrometric analysis is a sensitive and accurate tool in identifying and quantifying aerosolized allergens.

Measuring parvalbumin levels in fish muscle tissue: relevance of muscle locations and storage conditions

Fish is an allergenic food capable of provoking severe anaphylactic reactions. Parvalbumin is the major allergen identified in fish and frog muscles. Antibodies against fish and frog parvalbumin have been used to quantify parvalbumin levels from fish. However, these antibodies react variably with parvalbumin from different fish species. Several factors might be responsible for this variation including instability of parvalbumin in fish muscle as a result of frozen storage and differential parvalbumin expression in muscles from various locations within the whole fish. We aimed to investigate whether these factors contribute to the previously observed variable immunoreactivity of the anti-parvalbumin antibodies. Results showed the detection of parvalbumin by these antibodies was unaffected by frozen storage of muscles for 112 days. However, the parvalbumin content decreased in fish muscles from anterior to posterior positions. This factor may partially explain for the inconsistent reactivity of anti-parvalbumin antibodies to different fish species.

Identification of the major allergen of Macrobrachium rosenbergii (giant freshwater prawn)

OBJECTIVE

To characterize the major allergens of Macrobrachium rosenbergii (giant freshwater prawn).

METHODS

Raw and cooked extracts of the giant freshwater prawn were prepared. The IgE reactivity pattern was identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting technique with the sera of 20 skin prick test (SPT) positive patients. The major allergen identified was then characterized using the proteomics approach involving a combination of two-dimensional (2-DE) electrophoresis, mass spectrometry and bioinformatics tools.

RESULTS

SDS-PAGE of the raw extract showed 23 protein bands (15-250 kDa) but those ranging from 40 to 100 kDa were not found in the cooked extract. From immunoblotting experiments, raw and cooked extracts demonstrated 11 and 5 IgE-binding proteins, respectively, with a molecular mass ranging from 15 to 155 kDa. A heat-resistant 36 kDa protein was identified as the major allergen of both extracts. In addition, a 42 kDa heat-sensitive protein was shown to be a major allergen of the raw extract. The 2-DE gel fractionated the prawn proteins to more than 50 different protein spots. Of these, 10 spots showed specific IgE reactivity with patients' sera. Matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis led to identification of 2 important allergens, tropomyosin and arginine kinase.

CONCLUSIONS

It can be concluded that the availability of such allergens would help in component-based diagnosis and therapy of prawn allergies.

Penaeus monodon tropomyosin induces CD4 T-cell proliferation in shrimp-allergic patients

Shellfish allergy affects approximately 2% of the population and can cause immediate hypersensitivity reactions such as urticaria, swelling, difficulty breathing, and, in some cases, anaphylaxis. Tropomyosin is the major shrimp allergen and binds IgE in two-thirds of patients. A total of 38 shrimp-allergic patients and 20 negative control subjects were recruited and evaluated on the basis of history, skin prick testing, specific immunoglobulin E (IgE) levels, and peripheral blood mononuclear cell proliferation in response to shrimp tropomyosin or shrimp tropomyosin-derived peptides. Of the classically allergic patients by history, 59% tested positive for serum shrimp IgE antibodies. Of patients with shrimp-specific IgE in sera, 70% also had significant IgE levels specific for shrimp tropomyosin. Peripheral blood mononuclear cells from classically shrimp-allergic patients proliferated in a dose-dependent manner in response to to tropomyosin. In addition, a T-cell line derived from a shrimp-allergic patient proliferated specifically in response to tropomyosin-derived peptides. These studies suggest a strategy for immunotherapy using a tropomyosin-derived T-cell epitope vaccination.

Is epitope recognition of shrimp allergens useful to predict clinical reactivity?

BACKGROUND

Shrimp is a frequent cause of severe allergic reactions world-wide. Due to issues such as cross-reactivity, diagnosis of shrimp allergy is still inaccurate, requiring the need for double-blind, placebo-controlled food challenges (DBPCFC). A better understanding of the relationship between laboratory findings and clinical reactivity is needed.

OBJECTIVE

To determine whether sensitization to certain shrimp allergens or recognition of particular IgE epitopes of those allergens are good biomarkers of clinical reactivity to shrimp.

METHODS

Thirty-seven consecutive patients were selected with clinical histories of shrimp allergy. Skin prick test, specific IgE determinations, DBPCFC and immunoblot assays to shrimp extract were performed. IgE binding to synthetic overlapping peptides representing the sequence of the four allergens from the Pacific white shrimp (Litopenaeus vannamei) identified to date (Lit v1, Lit v2, Lit v3 and Lit v4) was analysed.

RESULTS

Of 37 (46%) patients, 17 had a positive challenge to shrimp (11 children and 6 adults). By microarray, patients with positive challenges showed more intense binding to shrimp peptides than those with negative challenges. Statistically significant differences in terms of the frequency and intensity of IgE binding to some epitopes were observed between the two groups. Diagnostic efficiency was higher for individual epitopes than for proteins. Particularly, efficiency was highest for certain Lit v 1 and Lit v 2 epitopes, followed by Lit v 3 and Lit v 4 epitopes.

CONCLUSION AND CLINICAL RELEVANCE

Patients with positive shrimp challenges present in general more intense and diverse epitope recognition to all four shrimp allergens. IgE antibodies to these shrimp epitopes could be used as biomarkers for prediction of clinical reactivity in subjects with sensitization to shrimp. Patients with positive shrimp challenges show more intense sensitization and more diverse epitope recognition. Several IgE-binding shrimp epitopes could be used as biomarkers for predicting clinical reactivity in subjects with sensitization to shrimp.

Tropomyosin sensitization in house dust mite allergic patients

The growing popularity and frequency of consumption of seafood is accompanied by an increasing number of adverse reactions reported in literature. Allergic reactions to seafood can generate a variety of symptoms ranging from a mild oral allergy syndrome to keen anaphylactic reactions. Tropomyosin, the major shellfish allergen is regarded to be responsible for clinical cross-reactivity to inhaled house dust mites. The aim of the study was to investigate the prevalence of sensitization to tropomyosin in house dust mite allergic patients in southern Bavaria and to compare the results with allergic symptoms. Sera of house dust mite allergic patients (positive skin prick test, allergen-specific IgE and intranasal provocation) were screened for IgE antibodies to tropomyosin (Der p 10). Patients were contacted by phone to evaluate allergic symptoms when consuming seafood. IgE antibodies to house dust mite tropomyosin (Der p 10) could be found in 4 out of 93 sera (4.3%). Two of these four patients (50%) showed itching and swelling of oral mucosa accompanied by bronchial obstruction after consumption of shrimp. Two patients had no problems when eating seafood. None of the seronegative patients complained about any health problems during or after consumption of seafood. In conclusion, cross-reactivity to tropomyosin in house dust mite allergic patients in southern Bavaria, Germany is rarer than suspected. Beside the direct allergic reactions, a further part of reactions to seafood must therefore be ascribed to other mechanisms such as intoxication or intolerance to, e.g. additives in the food product.

Update on the diagnosis and treatment of shellfish allergy

Shellfish allergy is a frequent, long-lasting, life-threatening disorder. As shellfish consumption increases, the number of allergic reactions to shellfish is expected to continue to rise as well. During the past decade, much has been learned about the allergens involved in shellfish allergy. Potential cross-reacting allergens between shellfish and other arthropods have been identified. As our knowledge of shellfish allergen improves, we will be able to develop more accurate methods of diagnosing shellfish allergy. In addition, extensive research is currently under way for the development of safer, more effective methods of managing shellfish hypersensitivity.

Shrimp allergy in Italian adults: a multicenter study showing a high prevalence of sensitivity to novel high molecular weight allergens

BACKGROUND

Shrimp is a frequent cause of food allergy worldwide. Besides tropomyosin, several allergens have been described recently.

OBJECTIVE

We investigated which allergens are involved in Italian shrimp-allergic adults.

METHODS

Sera from 116 shrimp-allergic patients selected in 14 Italian allergy centers were studied. Skin prick tests with house dust mite (HDM) as well as measurements of IgE to Pen a 1 (shrimp tropomyosin) and whole shrimp extract were performed. All sera underwent shrimp immunoblot analysis, and inhibition experiments using HDM extract as inhibitor were carried out on some Pen a 1-negative sera.

RESULTS

Immunoblots showed much variability. IgE reactivity at about 30 kDa (tropomyosin) was found in <50% of cases, and reactivity at about 67 kDa and >90 kDa was frequent. Further reactivities at 14-18, 25, 43-50, about 60 and about 80 kDa were detected. Most subjects had a history of shrimp-induced systemic symptoms irrespective of the relevant allergen protein. IgE to Pen a 1 were detected in sera from 46 (41%) patients. Skin reactivity to HDM was found in 43/61 (70%) Pen 1-negative subjects and inhibition studies showed that pre-adsorption of sera with HDM extract induced a marked weakening of the signal at >67 kDa.

CONCLUSIONS

Several allergens other than tropomyosin are involved in shrimp allergy in adult Italian patients. Some hitherto not described high molecular weight allergens seem particularly relevant in this population and their cross-reactivity with HDM allergens makes them novel potential panallergens of invertebrates.

Generation of a comprehensive panel of crustacean allergens from the North Sea Shrimp Crangon crangon

BACKGROUND

Published data on crustacean allergens are incomplete. The identification of tropomyosin (TM), arginine kinase (AK), sarcoplasmic Ca-binding protein (SCP) and myosin light chain (MLC) as shrimp allergens are all important contributions but additional allergens are required for the development of a complete set of reagents for component resolved diagnosis and the exploration of novel vaccination strategies.

METHODS

The North Sea shrimp (Crangon crangon), which is frequently consumed in Europe, served as a model organism in this study. TM and AK were directly cloned from mRNA based on sequence homology and produced as recombinant proteins. Additional IgE-reactive proteins were isolated by preparative SDS-PAGE and identified by mass spectrometry and corresponding cDNAs were cloned and expressed in E. coli. The relevance of the 6 cloned crustacean allergens was confirmed with sera of 31 shrimp-allergic subjects, 12 of which had a positive double-blind, placebo-controlled food challenge (DBPCFC) to shrimp and 19 a convincing history of food allergy to shrimp, including 5 cases of anaphylaxis. Quantitative IgE measurements were performed by ImmunoCAP.

RESULTS

Six recombinant crustacean proteins: TM, AK, SCP, a novel MLC, troponin C (TnC), and triosephosphate isomerase (TIM) bound IgE in ImmunoCAP analysis. Specific IgE to at least one of these single shrimp allergens was detected in 90% of the study population, thus the in vitro diagnostic sensitivity was comparable to that of shrimp extract (97%). In 75% of the subjects, the combined technical sensitivity was similar to or greater with single shrimp allergens than with natural shrimp extract.

CONCLUSIONS

We identified six IgE-binding proteins from C. crangon, three of which have not before been described as allergens in crustaceans. This extensive panel of shrimp allergens forms a valuable asset for future efforts towards the identification of clinically relevant biomarkers and as a basis to approach patient-tailored immunotherapeutic strategies.

Not all shellfish "allergy" is allergy!

The popularity of shellfish has been increasing worldwide, with a consequent increase in adverse reactions that can be allergic or toxic. The approximate prevalence of shellfish allergy is estimated at 0.5-2.5% of the general population, depending on degree of consumption by age and geographic regions. The manifestations of shellfish allergy vary widely, but it tends to be more severe than most other food allergens.

Tropomyosin is the major allergen and is responsible for cross-reactivity between members of the shellfish family, particularly among the crustacea. Newly described allergens and subtle differences in the structures of tropomyosin between different species of shellfish could account for the discrepancy between in vitro cross-antigenicity and clinical cross-allergenicity. The diagnosis requires a thorough medical history supported by skin testing or measurement of specific IgE level, and confirmed by appropriate oral challenge testing unless the reaction was life-threatening.

Management of shellfish allergy is basically strict elimination, which in highly allergic subjects may include avoidance of touching or smelling and the availability of self-administered epinephrine. Specific immunotherapy is not currently available and requires the development of safe and effective protocols.

Identification of hemocyanin as a novel non-cross-reactive allergen from the giant freshwater shrimp Macrobrachium rosenbergii

SCOPE

Sensitization to giant freshwater shrimp Macrobrachium rosenbergii (Mr) was recently reported. However, the allergens have yet to be identified. This study aimed to identify and characterize a novel allergen of Mr shrimp.

METHODS AND RESULTS

Extracted proteins were separated and purified by anion and in some experiments, size-exclusion chromatography. Serum IgE from shrimp allergic donors identified a candidate protein, which was characterized by LC-MS/MS. The specificity of IgE binding was tested using immunoblotting and inhibition ELISA. The IgE-binding profiles from 12 of 13 Mr allergic subjects that were pre-incubated with an extract of Penaeus monodon showed residual binding to ~60-80 kDa proteins. The 60-80 kDa IgE-bound proteins were fractionated in the flow-through of anion chromatography showing a high IgE reactivity. Peptides identified by LC-MS/MS showed the proteins closely match subunits of hemocyanin (Hcs). Purified Hcs from hemolymph markedly inhibited binding of IgE from sera of Mr allergic subjects to solid-phased Mr proteins in inhibition ELISA.

CONCLUSION

Hcs were identified as heat-stable, non-cross-reactive, high-molecular-weight (MW) allergens from Mr shrimp. Since circulatory organs are not always removed during food preparation, high concentrations of Hcs may be present along with shrimp meat, which contains the known cross-reactive tropomyosin protein.

Liquid chromatography and mass spectrometry in food allergen detection

Food allergy is an important issue in the field of food safety because of the hazards for affected persons and the hygiene requirements and legal regulations imposed on the food industry. Consumer protection and law enforcement require suitable analytical techniques for the detection of allergens in foods. Immunological methods are currently preferred; however, confirmatory alternatives are needed. The determination of allergenic proteins by liquid chromatography and mass spectrometry has greatly advanced in recent years, and gel-free allergenomics is becoming a routinely used approach for the identification and quantitation of food allergens. The present review provides a brief overview of the principles of proteomic procedures, various chromatographic set ups, and mass spectrometry instrumentation used in allergenomics. A compendium of published liquid chromatography methods, proteomic analyses, typical marker peptides, and quantitative assays for 14 main allergy-causing foods is also included.

Seafood hypersensitivity in mite sensitized individuals: is tropomyosin the only responsible allergen?

BACKGROUND

Seafood allergy has been related to mite sensitization, mainly mediated by the muscle protein tropomyosin.

OBJECTIVES

To determine the correlation between seafood hypersensitivity and mite sensitization (Dermatophagoides pteronyssinus and Chortoglyphus arcuatus, a highly prevalent storage mite in Spain) and to investigate the implication of tropomyosin in cross-reactivity.

METHODS

Patients from Northwest Spain were divided into 2 groups. The mite-seafood group contained 30 allergic mite individuals with a clinical history of food hypersensitivity. The mite group contained 40 individuals with positive skin prick test results to D pteronyssinus and C arcuatus but negative seafood test results. Specific IgE (sIgE) to whole mite and shrimp extracts, mite tropomyosin (rDer p 10), and shrimp tropomyosin (rPen a 1) were determined in each serum sample. Allergenic profiles were analyzed by immunoblot. Cross-reactivity studies were investigated by enzyme-linked immunosorbent assay and immunoblot inhibition studies.

RESULTS

In the mite-seafood group, 71% of patients had positive sIgE results to shrimp and 55% of them to shrimp tropomyosin. A strong correlation was found between sIgE to shrimp tropomyosin and mite tropomyosin. Positive correlation was observed between sIgE to shrimp tropomyosin and severity of symptoms. In the mite group, none of the 20% of patients with sIgE to shrimp tested positive to shrimp tropomyosin. In the immunoblot inhibition experiment, the shrimp extract was totally inhibited by mite extract. These data suggest that primary sensitization is related to mite sensitization.

CONCLUSION

Tropomyosin does not seem to be the main allergen involved in mite-seafood sensitization in mite sensitized individuals. High levels of sIgE to tropomyosin seem to be related to severity of symptoms.

Molecular diagnosis in allergy

Development and progress made in the field of recombinant allergens have allowed for the development of a new concept in allergy diagnosis, molecular diagnosis (MD), which makes it possible to identify potential disease-eliciting molecules. Microarray-based testing performed with a small amount of serum sample enables clinicians to determine specific-IgE antibodies against multiple recombinants or purified natural allergen components. Performance characteristics of allergens so far tested are comparable with current diagnostic tests, but have to be confirmed in larger studies. The use of allergen components and the successful interpretation of test results in the clinic require some degree of knowledge about the basis of allergen components and their clinical implications. Allergen components can be classified by protein families based on their function and structure. This review provides a brief overview of basic information on allergen components, recombinants or purified, currently available or soon to become commercially available in ImmunoCAP or ISAC systems, including names, protein family and function. Special consideration is given to primary or species-specific sensitization and possible cross-reactivity, because one of the most important clinical utility of MD is its ability to reveal whether the sensitization is genuine in nature (primary, species-specific) or if it is due to cross-reactivity to proteins with similar protein structures, which may help to evaluate the risk of reaction on exposure to different allergen sources. MD can be a support tool for choosing the right treatment for the right patient with the right timing. Such information will eventually give clinicians the possibility to individualize the actions taken, including an advice on targeted allergen exposure reduction, selection of suitable allergens for specific immunotherapy, or the need to perform food challenges. Nevertheless, all in vitro tests should be evaluated together with the clinical history, because allergen sensitization does not necessarily imply clinical responsiveness.

Greater epitope recognition of shrimp allergens by children than by adults suggests that shrimp sensitization decreases with age

BACKGROUND

Shellfish allergy is a long-lasting disorder typically affecting adults. Despite its high prevalence, there is limited information about allergenic shrimp proteins and the epitopes implicated in such allergic reactions.

OBJECTIVE

We sought to identify the IgE-binding epitopes of the 4 shrimp allergens and to characterize epitope recognition profiles of children and adults with shrimp allergy.

METHODS

Fifty-three subjects, 34 children and 19 adults, were selected with immediate allergic reactions to shrimp, increased shrimp-specific serum IgE levels, and positive immunoblot binding to shrimp. Study subjects and 7 nonatopic control subjects were tested by means of peptide microarray for IgE binding with synthetic overlapping peptides spanning the sequences of Litopenaeus vannamei shrimp tropomyosin, arginine kinase (AK), myosin light chain (MLC), and sarcoplasmic calcium-binding protein (SCP). The Wilcoxon test was used to determine significant differences in z scores between patients and control subjects.

RESULTS

The median shrimp IgE level was 4-fold higher in children than in adults (47 vs 12.5 kU(A)/L). The frequency of allergen recognition was higher in children (tropomyosin, 81% [94% for children and 61% for adults]; MLC, 57% [70% for children and 31% for adults]; AK, 51% [67% for children and 21% for adults]; and SCP, 45% [59% for children and 21% for adults]), whereas control subjects showed negligible binding. Seven IgE-binding regions were identified in tropomyosin by means of peptide microarray, confirming previously identified shrimp epitopes. In addition, 3 new epitopes were identified in tropomyosin (epitopes 1, 3, and 5b-c), 5 epitopes were identified in MLC, 3 epitopes were identified in SCP, and 7 epitopes were identified in AK. Interestingly, frequency of individual epitope recognition, as well as intensity of IgE binding, was significantly greater in children than in adults for all 4 proteins.

CONCLUSIONS

Children with shrimp allergy have greater shrimp-specific IgE antibody levels and show more intense binding to shrimp peptides and greater epitope diversity than adults.

Shellfish allergy

Seafood plays an important role in human nutrition and health. The growing international trade in seafood species and products has added to the popularity and frequency of consumption of a variety of seafood products across many countries. This increased production and consumption of seafood has been accompanied by more frequent reports of adverse health problems among consumers as well as processors of seafood. Adverse reactions to seafood are often generated by contaminants but can also be mediated by the immune system and cause allergies. These reactions can result from exposure to the seafood itself or various non-seafood components in the product. Non-immunological reactions to seafood can be triggered by contaminants such as parasites, bacteria, viruses, marine toxins and biogenic amines. Ingredients added during processing and canning of seafood can also cause adverse reactions. Importantly all these substances are able to trigger symptoms which are similar to true allergic reactions, which are mediated by antibodies produced by the immune system against specific allergens. Allergic reactions to 'shellfish', which comprises the groups of crustaceans and molluscs, can generate clinical symptoms ranging from mild urticaria and oral allergy syndrome to life-threatening anaphylactic reactions. The prevalence of crustacean allergy seems to vary largely between geographical locations, most probably as a result of the availability of seafood. The major shellfish allergen is tropomyosin, although other allergens may play an important part in allergenicity such as arginine kinase and myosin light chain. Current observations regard tropomyosin to be the major allergen responsible for molecular and clinical cross-reactivity between crustaceans and molluscs, but also to other inhaled invertebrates such as house dust mites and insects. Future research on the molecular structure of tropomyosins with a focus on the immunological and particularly clinical cross-reactivity will improve diagnosis and management of this potentially life-threatening allergy and is essential for future immunotherapy.

Advances in environmental and occupational respiratory diseases in 2009

The year 2009 led to a number of significant advances in environmental and occupational allergic diseases. The role of exposure to environmental pollutants, respiratory viruses, and allergen exposure showed significant advances. New allergens were identified. Occupational asthma and the relationship of complementary and alternative medicine to allergic diseases were extensively reviewed. New approaches to immunotherapy, novel vaccine techniques, and methods to reduce risks for severe allergic disease were addressed.

Advances in allergic skin disease, anaphylaxis, and hypersensitivity reactions to foods, drugs, and insects in 2009

This review highlights some of the research advances in anaphylaxis and hypersensitivity reactions to foods, drugs, and insects, as well as advances in allergic skin disease that were reported in the Journal in 2009. Among key epidemiologic observations, several westernized countries report that more than 1% of children have peanut allergy, and there is some evidence that environmental exposure to peanut is a risk factor. The role of regulatory T cells, complement, platelet-activating factor, and effector cells in the development and expression of food allergy were explored in several murine models and human studies. Delayed anaphylaxis to mammalian meats appears to be related to IgE binding to the carbohydrate moiety galactose-alpha-1,3-galactose, which also has implications for hypersensitivity to murine mAb therapeutics containing this oligosaccharide. Oral immunotherapy studies continue to show promise for the treatment of food allergy, but determining whether the treatment causes tolerance (cure) or temporary desensitization remains to be explored. Increased baseline serum tryptase levels might inform the risk of venom anaphylaxis and might indicate a risk for mast cell disorders in persons who have experienced such episodes. Reduced structural and immune barrier function contribute to local and systemic allergen sensitization in patients with atopic dermatitis, as well as increased propensity of skin infections in these patients. The use of increased doses of nonsedating antihistamines and potential usefulness of omalizumab for chronic urticaria was highlighted. These exciting advances reported in the Journal can improve patient care today and provide insights on how we can improve the diagnosis and treatment of these allergic diseases in the future.