Screening Of Lactobacillus Resistant To Soybean Allergy And Its Mechanism Of Antiallergic Effect

Soybean and its products are widely used in the food processing industry.However,as the main food allergen,soybean can cause adverse reactions in many aspects such as respiratory tract,gastrointestinal tract and skin,which seriously affects the quality of soybean allergic individuals.Recent studies have shown that gut microbiota play an important role in the development of food allergy,which makes it possible for probiotics to treat food allergy.Some studies have shown that lactobacillus play a positive role in the allergic reaction of peanut,OVA and lactoglobulin,but the research on lactobacillus against soybean allergy is very limited.In this paper,eight strains of lactobacillus commonly used in industry were co-cultured with mouse splenocytes in vitro,and the strains with potential of anti-soybean allergy were screened according to the level of cytokine secretion.Then,a Balb/c mouse model was constructed to evaluate the alleviation effects of lactobacillus on soybean protein allergy from the aspects of anaphylactic symptoms,cellular immunity and humoral immunity.Furthermore,the differentiation of intestinal dendritic cells,different T cell subsets and the changes of cecum content microflora were detected to evaluate the effects of lactobacillus on the intestinal mucosal immunity and intestinal microbial composition of mice sensitized with soybean protein.In this study,lactobacillus with the potential of anti-allergy were screened,and the immunological function of lactobacillus in the key stage of soybean allergy were evaluated comprehensively,which revealed its mechanism of anti-allergy.The main methods,results and conclusions are described as follows:1.Lactobacillus were co-cultured with soybean protein-sensitized mouse splenocytes in vitro,and anti-allergic strains were selected based on the levels of IFN-? and IL-4 secreted by the mouse splenocytes.The results showed that Lactobacillus casei(CICC6117),Streptococcus thermophilus(CICC6222),Lactobacillus acidophilus(CICC6081),Lactobacillus plantarum subsp.plantarum(CICC 20988)and Lactobacillus delbrueckii subsp.bulgaricus(CICC6103)significantly increased the IFN-y/IL-4 level.Among them,Lactobacillus acidophilus(CICC6081),Lactobacillus plantarum subsp.plantarum(CICC 20988)and Lactobacillus delbrueckii subsp.bulgaricus(CICC6103)were particularly effective.2.The soybean protein-sensitized Balb/c mouse model was established to evaluate the effects of Lactobacillus acidophilus,Lactobacillus plantarum subsp.plantarum and Lactobacillus delbrueckii subsp.bulgaricus on the clinical symptoms,humoral immunity,cellular immunity and effector cell differentiation of mice.The results showed that all three strains significantly reduced the anaphylactic symptom scores of mice.Meanwhile.Lactobacillus delbrueckii subsp.bulgaricus significantly alleviated the problem of slow weight gain in hypersusceptible mice.In terms of humoral immunity,the three strains significantly reduced the levels of specific antibodies(IgE.IgG and IgG1)in the serum of hypersusceptible mice,but they had no effect on the expression of B cells in the peripheral blood of mice.In terms of cellular immunity,the three strains restrained the differentiation of Th cells and promoted the differentiation of Tc cells to a certain extent.Lactobacillus acidophilus and Lactobacillus delbrueckii subsp.bulgaricus significantly promoted the differentiation of Treg in mouse splenocytes.Moreover,they also significantly enhanced the secretion of Treg-related cytokine(IL-10)and restrained the secretion of Th17-related cytokine(IL-17A)and Th2-related cytokines(IL-4 and IL-6).Lactobacillus delbrueckii subsp.bulgaricus also significantly stimulated the secretion of Thl-related cytokine(IFN-? and IL-2).In addition,all three strains significantly reduced the expression of mast cells in the ascites of hypersusceptible mice.3.MLN and PP were isolated from mouse intestinal tract,and the effect of lactobacillus on intestinal mucosal immunity was identified using flow cytometry.Meanwhile,the cecum contents of mice were collected,and the effect of lactobacillus on intestinal microbial composition was analyzed by 16S rDNA sequencing.The results showed that all three strains promoted the differentiation of CD103+ dendritic cells in the intestinal MLN and PP to a certain extent.In the aspect of T cell subsets differentiation,three strains of lactobacillus promoted the differentiation of Thl cells and inhibited the differentiation of Th2 cells in different degrees,of which Lactobacillus delbrueckii subsp.bulgaricus had the most obvious effect.Moreover,three strains of lactobacillus significantly inhibited the differentiation of Th17 cells in MLN.Lactobacillus acidophilus and Lactobacillus delbrueckii subsp.bulgaricus also significantly promoted the differentiation of Treg.In terms of the composition of gut microbiota,the three strains reduced the diversity and abundance of microorganisms in the intestine of hypersusceptible mice to varying degrees.Among them,Lactobacillus plantarum subsp.plantarum had a significant effect.In addition,the three strains promoted the proportion of Clostridiales in the intestine of hypersusceptible mice but significantly reduced the proportion of Bacillales.