Abstract
Shellfish is one of the major allergen sources worldwide, and tropomyosin (Tm) is the predominant allergic protein in shellfish. Probiotics has been appreciated for its beneficial effects on the host, including anti-allergic and anti-inflammatory effects, although the underlying mechanisms were not fully understood. In this study, oral administration of probiotic strain Bifidobacterium infantis 14.518 (Binf) effectively suppressed Tm-induced allergic response in a mouse model by both preventive and therapeutic strategies. Further results showed that Binf stimulated dendritic cells (DCs) maturation and CD103+ tolerogenic DCs accumulation in gut-associated lymphoid tissue, which subsequently induced regulatory T cells differentiation for suppressing Th2-biased response. We also found that Binf regulates the alterations of gut microbiota composition. Specifically, the increase of Dorea and decrease of Ralstonia is highly correlated with Th2/Treg ratio and may contribute to alleviating Tm-induced allergic responses. Our findings provide molecular insight into the application of Binf in alleviating food allergy and even gut immune homeostasis.
Highlights
Food allergy is a major public health issue, which torments 2% of the adult and 2–8% of children all over the world [1] and presents a remarkable increasing incidence in recent years [2]
We evaluated the effect of probiotic Bifidobacterium infantis 14.518 (Binf) in modulating Tm-induced allergic responses in a mouse model (Figure 1)
At the end of entire experimental period, the levels of histamine (p < 0.05) and Tm-specific IgE (p < 0.001) were significantly lower in mice supplemented with oral administration of Binf in both therapeutic and preventive ways compared with Tm stimulation group (Figures 2A–D), while no significant difference found in the level of Tm-specific IgG2a and IgG1 between Tm + Binf and Tm groups (Figures 2E–H)
Summary
Food allergy is a major public health issue, which torments 2% of the adult and 2–8% of children all over the world [1] and presents a remarkable increasing incidence in recent years [2]. In the process of food allergy, naïve T cells preferentially differentiate into T helper (Th) cells Th2, which further induce IgE-producing plasma cells, and in turn, resulting in mast cells degranulation and histamine releasing. In the process of immune tolerance, naïve T cells are mostly differentiated into Th1 cells so as to inhibit Th2 polarization, or differentiated into regulatory T cells (Tregs), which shut down the overall immune response to oral antigens [10]. CD103-expressing DCs (CD103+ DCs) are present at high frequency in the small intestine and migrate to the mesenteric lymph node (MLN) to initiate oral tolerance [12, 13]
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