Characterization of systemic allergenicity of tropomyosin from shrimp (Macrobrachium nipponense) and anaphylactic reactions in digestive tract.

BACKGROUND: Tropomyosin (TM) is the major allergen of crustaceans. The allergenicity of TM from Macrobrachium nipponense (MnTM) and the anaphylactic reaction in the digestive tract are still unclear. The aim of this study was to evaluate the allergenicity of MnTM and the anaphylactic reaction in the digestive tract. RESULTS: Serum IgE and IgG1 binding ability in the TM group were significantly higher than those in the PBS and CT groups (P < 0.01) and CP group (P < 0.05), while serum IgG and IgG2a binding ability showed no obvious difference between the four groups (P > 0.05). The levels of cytokines IL-4, IL-5 and IL-13 in TM and CP groups were significantly higher than those in PBS and CT groups. Histamine and ß-hexosaminidase in the TM and CP groups from basophil cell models were significantly higher than those in the PBS group. The highest mRNA expression of IL-4 and IL-13 was in the jejunum from TM-sensitized mice. Histopathological analysis showed that more immune cells infiltrated into the jejunum than the duodenum and ileum from the TM-sensitized mice. CONCLUSIONS: MnTM could promote an allergic response in mice and lead to degranulation in basophil cells. The jejunum was more easily affected by MnTM than duodenum and ileum, and the jejunum may be the major site of allergic response in the digestive tract. © 2020 Society of Chemical Industry.

Association of HLA-DQ and IL13 gene variants with challenge-proven shrimp allergy in West Bengal, India.

Little is known about genetic factors and mechanisms underlying shrimp allergy. Genome-wide association studies identified HLA class-II and IL13 genes as highly plausible candidates for shrimp allergy. The present study was designed to investigate potential associations of HLA-DQ rs9275596, IL13 rs20541, and IL13 rs1800925 polymorphisms with challenge-proven shrimp allergy using the data from 532 people of West Bengal, India; selected on basis of positive skin prick test, elevated specific IgE and medical history. Risk genotypes, i.e., HLA-DQ rs9275596 CC, IL13 rs20541 AA, and IL13 rs1800925 TT, were found to be significantly associated with challenge positive shrimp allergy (P = 0.04, 0.01, and 0.03, respectively). Distribution of genotypes for HLA-DQ and IL13 polymorphisms in allergic and control subjects showed significant difference between younger (20-40 years) and older (> 40 years) age group (P = 0.006). Risk genotypes significantly associated with elevated shrimp-specific IgE. IL13 TA haplotype significantly associated with shrimp allergy and elevated specific IgE (P = 0.02). Synergistic effect of IL13 TA haplotype-HLA-DQ rs9275596 CC genotype interaction significantly elevated specific IgE (P = 0.03). The present study suggests that HLA-DQ and IL13 polymorphisms pose major risk for shrimp allergic patients in West Bengal, India and thus could be helpful for early target-specific therapeutic intervention in near future.

Natural Shrimp (Litopenaeus vannamei) Tropomyosin Shows Higher Allergic Properties than Recombinant Ones as Compared through SWATH-MS-Based Proteomics and Immunological Response.

Tropomyosin (TM) is the major shrimp allergen that could trigger anaphylactic reactions. Recently, recombinant TM (rTM) has been accepted widely in the field of allergen-specific immunotherapy, but the allergenicity of rTM has not been compared with natural TM (nTM) based on an in vitro digestion profile. In this work, IgG-/IgE binding, allergen peptides, and degranulation ability of the digested samples in simulated gastric fluid/simulated intestinal fluid/gastrointestinal models from nTM and rTM were evaluated by immunoassays, proteomics, and basophil degranulation assay. Results showed that pepsin-digested and trypsin-digested samples of rTM exhibited lower IgG-/IgE binding and degranulation than those of nTM. More peptides of the digested samples from rTM (57.8%) matched shrimp allergic epitopes than those from nTM (33.3%). However, the peptide SITDELDQTF (269-278) appeared most frequently. These findings would supply foundation data for epitope-based immunotherapy to shrimp allergic individuals.

Modulating Shrimp Tropomyosin-Mediated Allergy: Hypoallergen DNA Vaccines Induce Regulatory T Cells to Reduce Hypersensitivity in Mouse Model.

Shellfish allergy is one of the most common food allergies, with tropomyosin as the major cross-reactive allergen. However, no allergen-specific immunotherapy is clinically available. Recently, we designed two shrimp hypoallergens MEM49 and MED171. This study aimed to examine and compare the efficacy of the MEM49- and MED171-based DNA vaccines (pMEM49 and pMED171) in modulating shrimp allergy in a murine model of shrimp tropomyosin sensitivity. Intradermal immunization of BALB/c mice with pMEM49 or pMED171 effectively down-modulated allergic symptoms, tropomyosin-specific IgE levels, intestinal Th2 cytokines expression, and inflammatory cell infiltration. Both pMEM49 and pMED171 increased the frequency of regulatory T cells, but to a greater extent by pMED171 with upregulation of gut-homing molecules integrin-α4ß7. The functionality of the pMED171-induced Treg cells was further illustrated by anti-CD25-mediated depletion of Treg cells and the adoptive transfer of CD4+CD25+Foxp3+Treg cells. Collectively, the data demonstrate that intradermal administration of pMED171 leads to the priming, activation, and migration of dermal dendritic cells which subsequently induce Treg cells, both locally and systemically, to downregulate the allergic responses to tropomyosin. This study is the first to demonstrate the potency of hypoallergen-encoding DNA vaccines as a therapeutic strategy for human shellfish allergy via the vigorous induction of functional Treg cells.