Cross-reactive monoclonal antibodies against fish parvalbumins as a tool for studying antigenic similarity of different parvalbumins and analysis of fish extracts.

Fish parvalbumins are heat-stable calcium-binding proteins that are highly cross-reactive in causing allergy symptoms in fish-sensitized patients. The reactivities of parvalbumin-specific monoclonal or polyclonal antibodies with parvalbumins of different fish species allowed their application for development of various immunoassays for allergen identification in fish samples. In this study, monoclonal antibodies (MAbs) were generated against two parvalbumins - natural Atlantic cod parvalbumin and recombinant common carp ß-parvalbumin expressed in E. coli. Large collections of recombinant parvalbumins and natural allergen extracts of different fish species and other animals were used to identify the specificities of these MAbs using ELISA, Western blot, and dot blot. MAbs demonstrated different patterns of cross-reactivities with recombinant parvalbumins. Their binding affinities were affected by the addition and removal of Ca2+ ions. Moreover, all MAbs showed a broad reactivity with the target antigens in natural fish, chicken, and pork extracts. The ability of two MAbs (clones 7B2 and 3F6) to identify and isolate native parvalbumins from allergen extracts was confirmed by Western blot. Epitope mapping using recombinant fragments of Atlantic cod parvalbumin (Gad m 1) and common carp parvalbumin (Cyp c 1) revealed that 4 out of 5 MAbs recognize parvalbumin regions that contain calcium binding sites. In conclusion, the generated broadly reactive well-characterized MAbs against fish ß-parvalbumins could be applied for investigation of parvalbumins of fish and other animals and their detection in allergen extracts.

IgE and IgG4 epitopes revealed on the major fish allergen Lat c 1.

BACKGROUND: The IgE- and IgG4-binding patterns of the major fish allergen parvalbumins are not clearly understood. IgE antibody-binding to parvalbumin from Asian seabass, Lat c 1.01, is implicated in up to 90 % of allergic reactions, although the region of IgE or IgG4 epitopes are unknown. In the present study, we characterized the specific IgE- and IgG4-binding regions of Lat c 1.01 using serum from pediatric and adult patients with clinically-confirmed fish allergy. METHODS: A comparative investigation of patient IgE- and IgG4-binding to recombinant Lat c 1.01 was performed by immunoblotting and indirect ELISA using serum from 15 children and eight adults with clinically confirmed IgE-mediated reactions to fish. The IgE- and IgG4-binding regions of Lat c 1.01 were determined by inhibition ELISA using seven overlapping peptides spanning the entire 102 amino acid sequence. Elucidated IgE-binding regions were modelled and compared to known antibody-binding regions of parvalbumins from five other fish species. RESULTS: Ninety five percent (22/23) patients demonstrated IgE-binding to rLat c 1.01, while fewer patients (10/15 children and 7/8 adults) demonstrated robust IgG4 binding when determined by immunoblots. IgE-binding for both cohorts was significantly higher compared to IgG4-binding by ELISA. All patients in this study presented individual IgE and IgG4 epitope-recognition profiles. In addition to these patient-specific antibody binding sites, general IgE epitopes were also identified at the C- and N-terminal regions of this major fish allergen. CONCLUSIONS AND CLINICAL RELEVANCE: Our findings demonstrate two specific IgE epitopes on parvalbumin from Asian seabass, while IgG4 binding is much lower and patient specific. This study highlights the importance of advancement in epitope analysis regardless of the age group for diagnostics and immunotherapies for fish allergy.

A novel method based on infrared spectroscopic inception-resnet networks for the detection of the major fish allergen parvalbumin.

We have developed a novel approach that involves inception-resnet network (IRN) modeling based on infrared spectroscopy (IR) for rapid and specific detection of the fish allergen parvalbumin. SDS-PAGE and ELISA were used to validate the new method. Through training and learning with parvalbumin IR spectra from 16 fish species, IRN, support vector machine (SVM), and random forest (RF) models were successfully established and compared. The IRN model extracted highly representative features from the IR spectra, leading to high accuracy in recognizing parvalbumin (up to 97.3%) in a variety of seafood matrices. The proposed infrared spectroscopic IRN (IR-IRN) method was rapid (~20 min, cf. ELISA ~4 h) and required minimal expert knowledge for application. Thus, it could be extended for large-scale field screening and identification of parvalbumin or other potential allergens in complex food matrices.

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.

Identification and characterization of parvalbumin-like protein in Trichophyton violaceum.

Parvalbumins play crucial physiological roles in neuromuscular systems of vertebrates, such as cell-cycle, development of neurons, contraction of muscles, and regulation of intracellular calcium. To perform these neuromuscular functions, parvalbumin may be in associated with other proteins including calbindin, carbonic anhydrase, and cytochrome oxidase. Humans may show an IgE-specific hypersensitivity to parvalbumins after consumption of some distinct fish species. While this protein is abundant in fish muscles, literature review of publications related to fish parvalbumins, do not point to the presence of parvalbumins in eukaryotic microbes. In this study, we propose that distantly related parvalbumins may be found in some non-fish species. Bioinformatics studies such as multiple sequence alignment (MSA), phylogenetic analysis as well as molecular-based experiments indicate that, at least two parvalbumins sequences (UniProt IDs: A0A178F775 and A0A178F7E4) with EF-hand domains and Ca2+-binding sites could be identified in Trichophyton violaceum, a pathogenic fungal species. It was determined that both genes consisted of a single exon and encoded for parvalbumin proteins possessing conserved amino acid motifs. Antigenicity prediction revealed antigenic sites located in both sides of the Ca2+-binding site of the first EF-hand domain. Our phylogenetic analysis revealed that one of parvalbumins (UniProt ID: 0A178F775) can be evolved to other parvalbumins in T. violaceum (UniProt ID: A0A178F7E4) and fish species through evolutionary phenomenon. To confirm our in-silico findings, we designed three primer pairs to detect one of the T. violaceum parvalbumins (UniProt ID: A0A178F7E4) by polymerase chain reaction (PCR); one primer pair showed a strong and specific band in agarose gel electrophoresis. To evaluate the specificity of the method, the primers were tested on extracted DNA from Trichophyton rubrum and T. mentagrophytes. The results demonstrated that the evaluated parvalbumin gene (UniProt ID: A0A178F7E4) was T. violaceum-specific and this pathogenic fungus can be differentiated from T. rubrum and T. mentagrophytes through identification of parvalbumin genes. Further studies are necessary to unravel the biochemical and physiological functions of parvalbumins in T. violaceum.

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.

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.

Lipid emulsion enhances fish allergen parvalbumin's resistance to in vitro digestion and IgG/IgE binding capacity.

This study was performed to determine Parvalbumin (PV), a well-known fish allergenic protein, digestion kinetics and immunoreactivity of digestion products with Immunoglobulin G/Immunoglobulin E recognition to understand its allergic potential with or without lipid emulsion process. PV was subjected to simulated gastrointestinal digestion in emulsified condition. Digestion kinetics of the protein was analysed by electrophoresis, IgG/IgE binding ability by immunoblotting and indirect ELISA. Lipid emulsion significantly (p < 0.01) reduced the degree of PV hydrolysis by 52.10% for gastric digestion. Immune fragments of gastric digestion were detectable for 90-120 min longer in emulsified condition showing resistance. Consequently, lipid emulsion decreased the digestive ability of PV in stomach, increasing resistance to gastrointestinal digestion by pepsin proteases. It also altered IgG/IgE binding ability of digestion products, thereby indicating that PV with lipid emulsion was resistant to digestion and possessed increased IgE binding ability resulting in higher risk of allergy among sensitized individuals.

Resistance of parvalbumin to gastrointestinal digestion is required for profound and long-lasting prophylactic oral tolerance.

BACKGROUND: Early introduction of food allergens into children's diet is considered as a strategy for the prevention of food allergy. The major fish allergen parvalbumin exhibits high stability against gastrointestinal digestion. We investigated whether resistance of carp parvalbumin to digestion affects oral tolerance induction. METHODS: Natural Cyp c 1, nCyp c 1, and a gastrointestinal digestion-sensitive recombinant Cyp c 1 mutant, mCyp c 1, were analyzed for their ability to induce oral tolerance in a murine model. Both antigens were compared by gel filtration, circular dichroism measurement, in vitro digestion, and splenocyte proliferation assays using synthetic Cyp c 1-derived peptides. BALB/c mice were fed once with high doses of nCyp c 1 or mCyp c 1, before sensitization to nCyp c 1. Immunological tolerance was studied by measuring Cyp c 1-specific antibodies and cellular responses by ELISA, basophil activation, splenocyte proliferations, and intragastric allergen challenge. RESULTS: Wild-type and mCyp c 1 showed the same physicochemical properties and shared the same major T-cell epitope. However, mCyp c 1 was more sensitive to enzymatic digestion in vitro than nCyp c 1. A single high-dose oral administration of nCyp c 1 but not of mCyp c 1 induced long-term oral tolerance, characterized by lack of parvalbumin-specific antibody and cellular responses. Moreover, mCyp c 1-fed mice, but not nCyp c 1-fed mice developed allergic symptoms upon challenge with nCyp c 1. CONCLUSION: Sensitivity to digestion in the gastrointestinal tract influences the capacity of an allergen to induce prophylactic oral tolerance.

Effect of EDTA enriched diets on farmed fish allergenicity and muscle quality; a proteomics approach.

Fish is one of the most common elicitors of food-allergic reactions worldwide. These reactions are triggered by the calcium-binding muscle protein ß-parvalbumin, which was shown to have reduced immunoglobulin E (IgE)-binding capacity upon calcium depletion. This work aimed to reduce gilthead seabream allergenicity using diets supplemented with a calcium chelator. Three experimental feeds were tested, differing in ethylenediaminetetraacetic acid (EDTA) supplementation, and its effects on muscle and parvalbumin's IgE-reactivity were analyzed. Chromatographic determination of EDTA showed no accumulation in the muscle and sensory results demonstrated that the lowest concentration did not affect fish quality as edible fish. Proteomics revealed one protein related to muscle contraction with significantly different relative abundance. Immunoblot assays performed with fish-allergic patients sera indicated a 50% reduction in IgE-reactivity upon EDTA presence. These preliminary results provide the basis for the further development of a non-GMO approach to modulate fish allergenicity and improve safety of aquaculture fish.

Reconstruction of fish allergenicity from the content and structural traits of the component ß-parvalbumin isoforms.

Most fish-allergic patients have anti-ß-parvalbumin (ß-PV) immunoglobulin E (IgE), which cross-reacts among fish species with variable clinical effects. Although the ß-PV load is considered a determinant for allergenicity, fish species express distinct ß-PV isoforms with unknown pathogenic contributions. To identify the role various parameters play in allergenicity, we have taken Gadus morhua and Scomber japonicus models, determined their ß-PV isoform composition and analyzed the interaction of the IgE from fish-allergic patient sera with these different conformations. We found that each fish species contains a major and a minor isoform, with the total PV content four times higher in Gadus morhua than in Scomber japonicus. The isoforms showing the best IgE recognition displayed protease-sensitive globular folds, and if forming amyloids, they were not immunoreactive. Of the isoforms displaying stable globular folds, one was not recognized by IgE under any of the conditions, and the other formed highly immunoreactive amyloids. The results showed that Gadus morhua muscles are equipped with an isoform combination and content that ensures the IgE recognition of all PV folds, whereas the allergenic load of Scomber japonicus is under the control of proteolysis. We conclude that the consideration of isoform properties and content may improve the explanation of fish species allergenicity differences.

Identification and comparison of allergenicity of native and recombinant fish major allergen parvalbumins from Japanese flounder (Paralichthys olivaceus).

Parvalbumin is the major fish allergen that can trigger anaphylactic reactions in predisposed individuals. We extracted and purified native parvalbumins from Japanese flounder (Paralichthys olivaceus) with gradient ammonium sulfate fractionation, and cloned DNAs into the expression vector pET-28a (+) to produce highly purified recombinant parvalbumin in Escherichia coli. The identification of native and recombinant parvalbumins was performed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, and mass spectrometry. The IgG-binding capacity was examined by indirect and inhibition ELISA. The immuno-reactivity was further evaluated by the release assay of ß-hexosaminidase in an RBL-2H3 cell model. Three parvalbumin isoforms were purified, namely PVI, PVII and PVIII with a purity of over 90%. Mass data showed that PVII and PVIII matched with XP_019958408.1 and XP_019938975.1 in the NCBI database, respectively. The recombinant parvalbumin was successfully expressed with high purity and matched with PVIII, which has been proved as the major parvalbumin isoform. Data from an ELISA assay revealed that the recombinant PVIII contains most of the IG-binding epitopes of the native PVIII. Meanwhile, the recombinant PVIII showed a lower immuno-reactivity in the RBL-2H3 cell model. The results suggest that recombinant PVIII could be a useful tool for the confirmation of fish allergens and diagnosis of fish allergies.

Effect of tyrosinase and caffeic acid crosslinking of turbot parvalbumin on the digestibility, and release of mediators and cytokines from activated RBL-2H3 cells.

Turbot can induce allergy in susceptible individuals due to the presence of parvalbumin (PV), a major fish allergen. This study aimed at evaluating the digestibility and the ability of PV to elicit the release of cellular degranulation, following treatment with tyrosinase (PV-Tyr), caffeic acid (PV-CA) and in combination (PV-Tyr/CA), using in vitro digestion and RBL-2H3 (passive rat basophil leukemia) cell line. The digestion assay products revealed that the stability of PV in simulated gastric fluid (SGF) was stronger, while in simulated intestinal fluid (SIF) was rather weak. Western blot analysis revealed that the IgG-binding abilities of the cross-linked PV were markedly reduced. Moreover, crosslinking hampered the release of cellular degranulation process in RBL-2H3 cell lines. PV-Tyr/CA showed highly significant reduction in the release rate of ß-hexosaminidase (66.02%), histamine (35.01%), tryptase (29.25%), cysteinyl leukotrienes (29.72%), prostaglandin D2 (34.96%), IL-4 (43.99%) and IL-13 (38.93%) and shown potential in developing hypoallergenic fish products.

Effect of laccase-catalyzed cross-linking on the structure and allergenicity of Paralichthys olivaceus parvalbumin mediated by propyl gallate.

The aim of the present study was to evaluate Paralichthys olivaceus parvalbumin (PV) following treatment by laccase (LAC) in the presence of propyl gallate (PG) on the structure and potential allergenicity. The structure of LAC + PG treated PV was analyzed through SDS-PAGE, CD, fluorescence, and allergenicity was analyzed by immunological and cell model. Our results showed that LAC + PG treatment can induce structural changes through PV cross-linking. Western blotting and indirect ELISA analysis revealed the decrease in IgG binding capacity of PV, corresponding with the structural changes. The results of in vitro digestion illustrate that LAC + PG treated PV showed more resistance to gastrointestinal digestion compared to untreated PV. The release rate of ß-hexosaminidase and histamine decreased by 35.6% and 66.9%, respectively, with LAC + PG treatment by RBL-2H3 cell assay. Considering the wide utilization of LAC in food industry, our treatment reveals its potential for creation of hypoallergenic fish products under mild reaction conditions.

Fish-derived low molecular weight components modify bronchial epithelial barrier properties and release of pro-inflammatory cytokines.

The prevalence of fish allergy among fish-processing workers is higher than in the general population, possibly due to sensitization via inhalation and higher exposure. However, the response of the bronchial epithelium to fish allergens has never been explored. Parvalbumins (PVs) from bony fish are major sensitizers in fish allergy, while cartilaginous fish and their PVs are considered less allergenic. Increasing evidence demonstrates that components other than proteins from the allergen source, such as low molecular weight components smaller than 3 kDa (LMC) from pollen, may act as adjuvants during allergic sensitization. We investigated the response of bronchial epithelial cells to PVs and to LMC from Atlantic cod, a bony fish, and gummy shark, a cartilaginous fish. Polarized monolayers of the bronchial epithelial cell line 16HBE14o- were stimulated apically with fish PVs and/-or the corresponding fish LMC. Barrier integrity, transport of PVs across the monolayers and release of mediators were monitored. Intact PVs from both the bony and the cartilaginous fish were rapidly internalized by the cells and transported to the basolateral side of the monolayers. The PVs did not disrupt the epithelial barrier integrity nor did they modify the release of proinflammatory cytokines. In contrast, LMC from both fish species modified the physical and immunological properties of the epithelial barrier and the responses differed between bony and cartilaginous fish. While the barrier integrity was lowered by cod LMC 24 h after cell stimulation, it was increased by up to 2.3-fold by shark LMC. Furthermore, LMC from both fish species increased basolateral and apical release of IL-6 and IL-8, while CCL2 release was increased by cod but not by shark LMC. In summary, our study demonstrated the rapid transport of PVs across the epithelium which may result in their availability to antigen presenting cells required for allergic sensitization. Moreover, different cell responses to LMC derived from bony versus cartilaginous fish were observed, which may play a role in different allergenic potentials of these two fish classes.

Molecular characterization of B-cell epitopes for the major fish allergen, parvalbumin, by shotgun proteomics, protein-based bioinformatics and IgE-reactive approaches.

Parvalbumins beta (ß-PRVBs) are the main fish allergens. The only proven and effective treatment for this type of hypersensitivity is to consume a diet free of fish. We present the molecular characterization of B-cell epitopes by shotgun proteomics of different ß-PRVBs combined with protein-based bioinformatics and IgE-reactive approaches. The final goal of this work is to identify potential peptide vaccine candidates for fish allergy. Purified ß-PRVBs from the main fifteen different fish species that cause allergy were analyzed by shotgun proteomics. Identified ß-PRVBs peptide sequences and ninety-eight ß-PRVB protein sequences from UniProtKB were combined, aligned and analyzed to determine B-cell epitopes using the Kolaskar and Tongaonkar algorithm. The highest rated predicted B-cell peptide epitopes were evaluated by ELISA using the corresponding synthetic peptides and sera from healthy and fish allergic patients. A total of 35 peptides were identified as B-cell epitopes. The top B-cell peptide epitopes (LKLFLQV, ACAHLCK, FAVLVKQ and LFLQNFV) that may induce protective immune responses were selected as potential peptide vaccine candidates. The 3D model of these peptides were located in the surface of the protein. This study provides the global characterization of B-cell epitopes for all ß-PRVBs sequences that will facilitate the design of new potential immunotherapies. SIGNIFICANCE: This work provides the global characterization of B-cell epitopes for all ß-PRVBs sequences by Shotgun Proteomics combined with Protein-based Bioinformatics and IgE-reactive approaches. This study will increase our understanding of the molecular mechanisms whereby fish allergens elicit allergic reactions and will facilitate the design of new potential peptide vaccine candidates.

Parvalbumin-immunoreactive cells in the olfactory bulb of the pigeon: Comparison with the rat.

The olfactory bulb (OB) shows special characteristics in its phylogenetic cortical structure and synaptic pattern. In the OB, gamma-aminobutyric acid (GABA), as an inhibitory neurotransmitter, is secreted from GABAergic neurons which contain parvalbumin (a calcium-binding protein). Many studies on the distribution of parvalbumin-immunoreactive neurons in the rodent OB have been published but poorly reported in the avian OB. Therefore, in this study, we compared the structure of the OB and distribution of parvalbumin-immunoreactive neurons in the OB between the rat and pigeon using cresyl violet staining and immunohistochemistry for parvalbumin, respectively. Fundamentally, the pigeon OB showed layers like those of the rat OB; however, some layers were not clear like in the rat OB. Parvalbumin-immunoreactive neurons in the pigeon OB were predominantly distributed in the external plexiform layer like that in the rat OB; however, the neurons did not have long processes like those in the rat. Furthermore, parvalbumin-immunoreactive fibres were abundant in some layers; this finding was not shown in the rat OB. In brief, parvalbumin-immunoreactive neurons were found like those in the rat OB; however, parvalbumin-immunoreactive fibres were significantly abundant in the pigeon OB compared to those in the rat OB.

Effect of tyrosinase-catalyzed crosslinking on the structure and allergenicity of turbot parvalbumin mediated by caffeic acid.

BACKGROUND: Enzymatic treatment of allergenic protein can alter their functional properties under a mild reaction condition due to specificity of enzymes. Phenolic compounds act as mediators and enhance the crosslinking reactions. The study aimed to assess the changes in the structure and immunoglobulin G (IgG) binding capacity of turbot parvalbumin (PV) upon crosslinking with tyrosinase (Tyr) in the absence and presence of caffeic acid. RESULTS: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed the appearance of higher molecular weight bands (24, 36 kDa) in the crosslinked PV. The secondary structure of crosslinked PV became loosened and disordered. The results of intrinsic fluorescence and ultraviolet absorption spectral analyses, as well as surface hydrophobicity and free amino group analyses also revealed structural changes. As observed by western blot analysis, the intensity of the PV bands reduced upon Tyr treatment, indicating reduced binding of specific IgG to PV. Moreover, the indirect ELISA (enzyme-linked immunosorbent assay) analysis confirmed that the IgG binding ability of crosslinked PV was reduced 34.94%. CONCLUSION: Enzymatic treatment mitigated the allergenicity of fish PV, which was closely related to the alterations in the conformational structure. This treatment showed potential for developing hypoallergenic fish products under mild reaction conditions. © 2019 Society of Chemical Industry.

Matrix effect on food allergen detection - A case study of fish parvalbumin.

Two fish parvalbumin models were established to study relationships among matrix effect, extractability, and thermostability during in vitro immunodetection using two parvalbumin-specific monoclonal antibodies (3E1 and PARV19). Our results illustrated that matrix-induced thermal instability of parvalbumin was due mainly to physical (hydrophobic effect) and chemical (thiol-disulfide interchange) interactions. The addition of sodium dodecyl sulfate (SDS, surfactant), ß-mercaptoethanol (reducing agent) or ethylenediaminetetraacetic acid (EDTA, metal chelator) during sample preparation could not only increase the extractability of parvalbumin but also enhanced its immunodetection. Our findings demonstrated excess EDTA completely chelated Ca2+ in parvalbumin and rendered it undetectable using PARV19 (a Ca2+-dependent antibody). Overall, our resulted showed that matrix effect on in vitro analyte quantification cannot be underestimated. Any false negative or positive results could lead to severe or life-threatening allergic reactions.

Patients Allergic to Fish Tolerate Ray Based on the Low Allergenicity of Its Parvalbumin.

BACKGROUND: Clinical reactions to bony fish species are common in patients with allergy to fish and are caused by parvalbumins of the ß-lineage. Cartilaginous fish such as rays and sharks contain mainly α-parvalbumins and their allergenicity is not well understood. OBJECTIVE: To investigate the allergenicity of cartilaginous fish and their α-parvalbumins in individuals allergic to bony fish. METHODS: Sensitization to cod, salmon, and ray among patients allergic to cod, salmon, or both (n = 18) was explored by prick-to-prick testing. Clinical reactivity to ray was assessed in 11 patients by food challenges or clinical workup. IgE-binding to ß-parvalbumins (cod, carp, salmon, barramundi, tilapia) and α-parvalbumins (ray, shark) was determined by IgE-ELISA. Basophil activation tests and skin prick tests were performed with ß-parvalbumins from cod, carp, and salmon and α-parvalbumins from ray and shark. RESULTS: Tolerance of ray was observed in 10 of 11 patients. Prick-to-prick test reactions to ray were markedly lower than to bony fish (median wheal diameter 2 mm with ray vs 11 mm with cod and salmon). IgE to α-parvalbumins was lower (median, 0.1 kU/L for ray and shark) than to ß-parvalbumins (median, ≥1.65 kU/L). Furthermore, α-parvalbumins demonstrated a significantly reduced basophil activation capacity compared with ß-parvalbumins (eg, ray vs cod, P < .001; n = 18). Skin prick test further demonstrated lower reactivity to α-parvalbumins compared with ß-parvalbumins. CONCLUSIONS: Most patients allergic to bony fish tolerated ray, a cartilaginous fish, because of low allergenicity of its α-parvalbumin. A careful clinical workup and in vitro IgE-testing for cartilaginous fish will improve patient management and may introduce an alternative to bony fish into patients' diet.