Characterization And Regulational Mechanism Of Lactic Acid Bacteria In Ameliorating Food Allergy By Shrimp (Litopenaeus Vannamei) Protein In Mice

Sensitization of edible proteins from shrimp and other aquatic products has significantly potential threatens to the consumers’health and safety. However, the sensitization mainly depends on the allergen types and amount in foods. Many studies have shown that lactic acid bacteria (LAB) can effectively reduce allergy symptoms and keep balance of immune system. However, there are still many issues to be resolved, such as the various effects and mechanism of anti-allergic strains. Therefore, in the present study, the muscle proteins of shrimp(Litopenaeus vannamei) were extracted for intraperitoneally injection to Balb/c mice, and finally allergic model of Balb/c mice with the shrimp extracts was constructed. After gavage with five different Lactobacillus strains, the indirect ELISA was used to detect the levels of specific IgE and IgG1 antibodies in sera of mice so as to validate if the model has been successfully established. Hematoxylin and eosin (H&E) as well as Toluidine blue staining were used to analyze intestinal mucosal immune responses in mice caused by the shrimp extracts. The levels of cytokines and T cell subsets were analyzed in spleen. The main findings are as follows:1. Intraperitoneally injection of shrimp (Litopenaeus vannamei) muscle protein extracts was used to establish the allergic model of Balb/c mice with the shrimp extracts. The content of specific antibody IgE and IgGl and histamine in high dose group were significantly higher than that in the control group. Also, the results showed that the shrimp protein sensitized mice had severe intestinal inflammation and epithelial damage, as well as intestinal mast cell degranulation and significant reduction in the number of intact mast cells. All of the results indicated that the model has been successfully established and could be used for further experiment.2. Oral administration of five different LAB strains showed variable effects on protection against allergic reactions in sensitized mice. The most effective anti-allergic strain, Bacillus coagulans 09.712 (B. coagulans 09.712), greatly improved epithelial barrier functions. Also, the B. coagulans 09.712 inhibited the mast cell degranulation and reduced the content of IgE and IgG1. In vitro studies indicate that B. coagulans 09.712 regulates the proliferation and function of lymphocytes response to shrimp proteins. Our findings also show that probiotic LAB suppress shrimp protein caused sensitization by improving Th1/Th2/Treg balance and Th2 inflammation.3. Co-culture of B. coagulans 09.712, Treg cells and B cells showed that B. coagulans 09.712 could suppress IgE secretion and promote IgG4 antibody production, which suggested that LAB could induce antibody conversion. In addition, co-culture of B. coagulans 09.712, Treg cells and Th2 cells showed that B. coagulans 09.712 enhanced the mRNA expression of Foxp3、TGF-β and IL-10 and inhibited the secretion of Th2 cytokines, which indicated that LAB could modulate the immune balance in Th1 and Th2. Co-culture of B. coagulans 09.712 and P815 mast cells showed that B. coagulans 09.712 inhibited degranulation and reduced histamine release.