Quantitative analysis of species specificity of two anti-parvalbumin antibodies for detecting southern hemisphere fish species demonstrating strong phylogenetic association

Development of a sensitive sandwich ELISA with broad species specificity for improved fish allergen detection

A sensitive Enzyme-linked Immunosorbent Assay (ELISA) with improved broad species specificity was developed for the detection of southern hemisphere fish residues in processed foods. The polyclonal antibodies were raised against parvalbumins from 13 fish species representing 7 fish orders selected for their molecular diversity and immunoreactivity profile. The optimized ELISA-2 (based on the rabbit capture antibody (RB#4) - sheep detection antibody (S2#4) pair) displayed an improved detection limit of 0.6 μg/L (3.7 μg of /kg). Our immunoreactivity-directed species selection approach in the strategized antibody production significantly improved the detection of no or weakly immunoreactive fish species previously not detected immunochemically. Of 37 commercially important fish species tested, the ELISA-2 could detect 28 fish species (76%). The optimized sample extraction with a buffer additive achieved good protein recoveries of 87.2 - 117.3% (within the AOAC recommended range). The ELISA-2 was able to detect fish residues in five highly processed food products.

Austral birds offer insightful complementary models in ecology and evolution

The Southern Hemisphere differs from the Northern Hemisphere in many aspects. However, most ecological and evolutionary research is conducted in the Northern Hemisphere and its conclusions are extrapolated to the entire globe. Therefore, unique organismal and evolutionary characteristics of the south are overlooked. We use ornithology to show the importance of including a southern perspective. We present examples of plumage pigmentation, brood-parasitic nestling ejection, flightlessness, female song, and female aggression modulated by progesterone as complementary models for investigating fundamental biological questions. More research in the Southern Hemisphere, together with increased cooperation among researchers across the hemispheres and within the Southern Hemisphere, will provide a greater global outlook into ecology and evolution.

Recombinant Tropomyosin from the Pacific Oyster (Crassostrea gigas) for Better Diagnosis

The Pacific oyster is a commercially important mollusc and, in contrast to most other shellfish species, frequently consumed without prior heat treatment. Oysters are rich in many nutrients but can also cause food allergy. Knowledge of their allergens and cross-reactivity remains very limited. These limitations make an optimal diagnosis of oyster allergy difficult, in particular to the Pacific oyster (Crassostrea gigas), the most cultivated and consumed oyster species worldwide. This study aimed to characterise IgE sensitisation profiles of 21 oyster-sensitised patients to raw and heated Pacific oyster extract using immunoblotting and advanced mass spectrometry, and to assess the relevance of recombinant oyster allergen for improved diagnosis. Tropomyosin was identified as the major allergen recognised by IgE from 18 of 21 oyster-sensitised patients and has been registered with the WHO/IUIS as the first oyster allergen (Cra g 1). The IgE-binding capacity of oyster-sensitised patients’ IgE to purified natural and recombinant tropomyosin from oyster, prawn, and dust mite was compared using enzyme-linked immunosorbent assay. The degree of IgE binding varied between patients, indicating partial cross-sensitisation and/or co-sensitisation. Amino acid sequence alignment of tropomyosin from these three species revealed five regions that contain predicted IgE-binding epitopes, which are most likely responsible for this cross-reactivity. This study fully biochemically characterises the first and major oyster allergen Cra g 1 and demonstrates that the corresponding recombinant tropomyosin should be implemented in improved component-resolved diagnostics and guide future immunotherapy.

Fish Allergy Around the World—Precise Diagnosis to Facilitate Patient Management

The accurate and precise diagnosis of IgE-mediated fish allergy is one of the biggest challenges in allergy diagnostics. A wide range of fish species that belong to evolutionary distant classes are consumed globally. Moreover, each fish species may contain multiple isoforms of a given allergen that often differ in their allergenicity. Recent studies indicated that the cross-reactivity between different fish species is limited in some cases and depends on the evolutionary conservation of the involved allergens. Fish allergens belong to several protein families with different levels of stability to food processing. Additionally, different preparation methods may contribute to specific sensitization patterns to specific fish species and allergens in different geographic regions. Here, we review the challenges and opportunities for improved diagnostic approaches to fish allergy. Current diagnostic shortcomings include the absence of important region-specific fish species in commercial in vitro and in vivo tests as well as the lack of their standardization as has been recently demonstrated for skin prick test solutions. These diagnostic shortcomings may compromise patients' safety by missing some of the relevant species and yielding false negative test results. In contrast, the avoidance of all fish as a common management approach is usually not necessary as many patients may be only sensitized to specific species and allergens. Although food challenges remain the gold standard, other diagnostic approaches are investigated such as the basophil activation test. In the context of molecular allergy diagnosis, we discuss the usefulness of single allergens and raw and heated fish extracts. Recent developments such as allergen microarrays offer the possibility to simultaneously quantify serum IgE specific to multiple allergens and allergen sources. Such multiplex platforms may be used in the future to design diagnostic allergen panels covering evolutionary distant fish species and allergens relevant for particular geographic regions.

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

BACKGROUND

Fish is a major food and allergen source, requiring safety declarations on packages. Enzyme-linked immunosorbent assays (ELISAs) are often used to ensure that the product meets the required standards with regard to the presence of allergens. Over 1000 different fish species are traded and consumed worldwide, and they are increasingly provided by aquaculture. Up to 3% of the general population is at risk of sometimes fatal allergic reactions to fish, requiring strict avoidance of this commodity. The aim of this study is to evaluate the capacity of three commercially available ELISA tests to detect a wide variety of bony and cartilaginous fish and their products, which is essential to ensure reliable and safe food labeling.

RESULTS

The detection rates for 57 bony fish ranged from 26% to 61%. Common European and North American species, including carp, cod, and salmon species, demonstrated a higher detection rate than those from the Asia-Pacific region, including pangasius and several mackerel and tuna species. Among the 17 canned bony fish products, only 65% to 86% were detected, with tuna showing the lowest rate. None of the cartilaginous fish (n = 9), other vertebrates (n = 8), or shellfish (n = 5) were detected.

CONCLUSIONS

We demonstrated that three commercial fish ELISA kits had a limited capacity to detect fish and their products. The complexity of fish as a protein source that is increasingly utilized means that there is an urgent need for improved detection methods. This is crucial for the food industry to provide safe seafood products and comply with international legislation. © 2020 Society of Chemical Industry.

Determination of biogenic amines in Chub Mackerel from different storage methods

The eight biogenic amines (BA), which are histamine (HIS), tryptamine, putrescine, 2-phenylethylamine, cadaverine, tyramine, spermidine, and spermine, were determined in Chub Mackerel under different storage conditions after being freshly caught. The storage time and temperature were varied and the guts either present or removed. This study describes a reverse-phase high-performance liquid chromatography (HPLC) with a fluorescence detector following precolumn derivation with dansyl chloride method for the determination of BA in in Chub Mackerel samples. HIS represented the highest content of BA regardless of the storage temperature and time. During a 24-hr period, the content of HIS reached its highest level of 6,466.63 mg/kg at the storage temperature of 30 °C, whereas it only reached 28.73 mg/kg in 24 hr when the storage temperature was 0 °C, which is way below the standard acceptable threshold level (400 mg/kg). The storage times for the content of HIS to exceed the standard threshold level for HIS at different storage temperatures of 0, 4, 10, 15, 20, and 25 °C were 12, 5, 4 days, 48, 36, 15, and 14 hr, respectively. However, these times were significantly shortened when the viscera was removed from freshly-caught fish before storage. This study not only provides data for monitoring the content of BA, especially HIS, to ensure the safe storage and consumption of freshly-caught Chub Mackerel, but also presents a cost-effective method to extend the storage time of freshly-caught Chub Mackerel. PRACTICAL APPLICATION: This study not only provides data for monitoring the content of BA, especially HIS, to ensure the safe storage and consumption of freshly-caught Chub Mackerel, but also presents a cost-effective method, which is gut-removal during storage, to extend the storage time of freshly-caught Chub Mackerel.

Variability of allergens in commercial fish extracts for skin prick testing

BACKGROUND

Commercial allergen extracts for allergy skin prick testing (SPT) are widely used for diagnosing fish allergy. However, there is currently no regulatory requirement for standardization of protein and allergen content, potentially impacting the diagnostic reliability of SPTs. We therefore sought to analyse commercial fish extracts for the presence and concentration of fish proteins and in vitro IgE reactivity using serum from fish-allergic patients.

METHODS

Twenty-six commercial fish extracts from five different manufacturers were examined. The protein concentrations were determined, protein compositions analysed by mass spectrometry, followed by SDS-PAGE and subsequent immunoblotting with antibodies detecting 4 fish allergens (parvalbumin, tropomyosin, aldolase and collagen). IgE-reactive proteins were identified using serum from 16 children with confirmed IgE-mediated fish allergy, with focus on cod, tuna and salmon extracts.

RESULTS

The total protein, allergen concentration and IgE reactivity of the commercial extracts varied over 10-fold between different manufacturers and fish species. The major fish allergen parvalbumin was not detected by immunoblotting in 6/26 extracts. In 7/12 extracts, five known fish allergens were detected by mass spectrometry. For cod and tuna, almost 70% of patients demonstrated the strongest IgE reactivity to collagen, tropomyosin, aldolase A or β-enolase but not parvalbumin.

CONCLUSIONS

Commercial fish extracts often contain insufficient amounts of important allergens including parvalbumin and collagen, resulting in low IgE reactivity. A comprehensive proteomic approach for the evaluation of SPT extracts for their utility in allergy diagnostics is presented. There is an urgent need for standardized allergen extracts, which will improve the diagnosis and management of fish allergy.

Seafood allergy: A comprehensive review of fish and shellfish allergens

Seafood refers to several distinct groups of edible aquatic animals including fish, crustacean, and mollusc. The two invertebrate groups of crustacean and mollusc are, for culinary reasons, often combined as shellfish but belong to two very different phyla. The evolutionary and taxonomic diversity of the various consumed seafood species poses a challenge in the identification and characterisation of the major and minor allergens critical for reliable diagnostics and therapeutic treatments. Many allergenic proteins are very different between these groups; however, some pan-allergens, including parvalbumin, tropomyosin and arginine kinase, seem to induce immunological and clinical cross-reactivity. This extensive review details the advances in the bio-molecular characterisation of 20 allergenic proteins within the three distinct seafood groups; fish, crustacean and molluscs. Furthermore, the structural and biochemical properties of the major allergens are described to highlight the immunological and subsequent clinical cross-reactivities. A comprehensive list of purified and recombinant allergens is provided, and the applications of component-resolved diagnostics and current therapeutic developments are discussed.