Comparative analysis of asian carps parvalbumin reveals the divergence pattern of major fish allergen.

BACKGROUND: Asian carps, a popular freshwater fish globally, are valued for their flavor and serve as a crucial protein source, especially for infants. However, grass carp parvalbumin is highly allergenic, surpassing the allergenicity of fish like salmon and cod. The allergenic potential of parvalbumin in other Asian carps remains unknown, underscoring the need for allergen identification to improve the precision of fish allergy diagnosis and treatment. OBJECTIVE: To identify all parvalbumin homologs in Asian carps and investigate the role of gene divergence in allergenic homolog formation. METHODS: Three annotated genomes of Asian carp, including grass carp, black carp and bighead carp, were constructed using a hybrid assembly approach. Through sequence homology at the genomic level, all the homologs of major fish allergens were identified. Bioinformatics tools were then employed to reveal the gene structures, expression levels, and protein conformations of parvalbumin. RESULTS: Grass carp genome analysis showed nine parvalbumin homologs, with Cid_PV2 most similar to Cten i 1. Bighead and black carp genomes had ten homologs, including potentially allergenic Mpi_PV7 and Hno_PV7. Tissue-specific expression patterns revealed alternative usage of parvalbumin homologs. Gene duplication events expanded parvalbumin copies in bony fish, with two gene clusters identified in Asian carp genomes. CONCLUSION: All the homologs of Asian carps' parvalbumin were accurately identified and gene divergence contributed to the formation of allergenic homologs. Together with a comprehensive gene sequence profile of carps' parvalbumin, those could be applied to achieve a more precise clinical diagnostic test.

Genomics of Shrimp Allergens and Beyond.

Allergy to shellfishes, including mollusks and crustaceans, is a growing health concern worldwide. Crustacean shellfish is one of the "Big Eight" allergens designated by the U.S. Food and Drug Administration and is the major cause of food-induced anaphylaxis. Shrimp is one of the most consumed crustaceans triggering immunoglobulin E (IgE)-mediated allergic reactions. Over the past decades, the allergen repertoire of shrimp has been unveiled based on conventional immunodetection methods. With the availability of genomic data for penaeid shrimp and other technological advancements like transcriptomic approaches, new shrimp allergens have been identified and directed new insights into their expression levels, cross-reactivity, and functional impact. In this review paper, we summarize the current knowledge on shrimp allergens, as well as allergens from other crustaceans and mollusks. Specific emphasis is put on the genomic information of the shrimp allergens, their protein characteristics, and cross-reactivity among shrimp and other organisms.

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.

Allergen immunotherapy for food allergy from the Asian perspective: key challenges and opportunities.

Introduction: Prevalence of food allergy is rising in different regions of the world. Asia has not been spared from this epidemic, but epidemiological data have revealed a different pattern of food allergens in this continent. Allergen-specific immunotherapy (AIT) for food allergy, which has been revolutionary as the main focus of research in recent years, needs to be adapted for the different populations in Asia. Areas covered: Recent evidence shows increasing popularity and superiority of AIT over strict food avoidance as the cornerstone of food allergy management. Asia is a distinctive continent with specific food allergy triggers, in particular, seafood, and wheat. Peanut, on the contrary, is not a common food allergen in most parts of Asia. The common Asian food allergens, as well as the rapidly developing food-specific AIT in this region will be covered in this article. Expert commentary: Evidence on oral immunotherapy for wheat allergy and preclinical data on shellfish AIT are promising. Further work should be done on resolving cross-sensitization between environmental allergens with wheat and shellfish allergens, and a modified AIT approach to enhance the safety and effectiveness of food-specific immunotherapy.

Low-Dose Allergen-Specific Immunotherapy Induces Tolerance in a Murine Model of Shrimp Allergy.

BACKGROUND: The efficacy and safety of allergen-specific immunotherapy (AIT) are highly dose-dependent. METHODS: We investigated the dosage effects of AIT and the underlying mechanisms in a murine model of shrimp hypersensitivity. BALB/c mice were sensitized with recombinant shrimp allergen rMet e 1 and challenged orally with a high dose of rMet e 1 to elicit an allergic response. These sensitized mice were then treated with a low (0.01 mg), medium (0.05 mg), or high dosage (0.1 mg) of rMet e 1 intraperitoneally before receiving a second oral challenge. The allergic responses and immunological changes in the gut were compared between animals receiving different dosages. RESULTS: We found that all sensitized mice that received rMet e 1 immunotherapy were desensitized, regardless of the dosage, and protected at the second oral challenge. Nevertheless, the mice in the high-dosage group experienced severe systemic reactions during the treatment phase. In contrast, regulatory T (Treg) cell-associated genes were upregulated only in the low- and medium-dosage groups, and Foxp3+ cells were more abundant in the gut lymphoid tissues than in the high-dosage group. CONCLUSIONS: Our results demonstrate that low-dosage immunotherapy favors the induction of local Foxp3+ Treg cells and the upregulation of regulatory cytokines. The safety advantages and long-term efficacy of low-dosage immunotherapy should be taken into consideration when developing immunotherapy dose schedules.