Effect And Mechanism Of Lactobacillus Casei Regulating Food Allergy In Oral Sensitized Mouse Model With Shrimp Tropomyosin

In recent years,food allergies have occurred frequently,and the number of allergic people has increased.In Asia,the proportion of allergic people with aquatic products is especially high,which seriously affects people’s daily lives and even endanger their lives.Probiotics can alleviate food allergies by regulating intestinal flora,and is a potentially effective means of treating food allergies,but its detailed and in-depth mechanism has not been fully elucidated.Lactobacillus casei Zhang(LcZhang)isolated from sour milk is not only widely used in dairy fermentation,but also has many functions such as regulating intestinal immunity and improving intestinal microbiota in mice.Nevertheless,there are few reports on the effect and mechanism of alleviating food allergies by LcZhang.On the other hand,antibiotic abuse has become one of the important factors leading to a sharp rise in the incidence of food allergies.However,the detailed mechanism of antibiotics exacerbating food allergies is still unclear.Thereby,in this study,a non-toxic mucosal adjuvant,cholera toxin B subunit(CTB),and a fusion protein containing adjuvant and allergen tropomyosin(TM),CTB-TM,were obtained by prokaryotic expression.Subsequently,through the construction of three different oral sensitization models including oral administration of mice with TM,CTB-TM and antibiotic treatment(TM+Abx)and three LcZhang intervention model,the sensitization effects of different oral sensitization models and effect of LcZhang on allergic reaction in mice with different sensitization models were explored.Whether the food allergy oral sensitization model was successfully constructed was determined by mouse body weight change,clinical symptoms,serum specific antibody IgE,IgG2a,IgGl,histamine content,and intestinal mucosal injury(intestinal histopathology and relative expression levels of Tslp and Il33 in the small intestine),which also can explore the effects of antibiotics on food allergies,and whether low-dose CTB-TM recombinants can induce allergic reactions and thus replace natural proteins for food allergy studies.In addition,the potential mechanism and difference of LcZhang on TM sensitized and TM+Abx sensitized mice were explored from T cell immune balance,intestinal flora homeostasis,and oral tolerance.The main conclusions are as follows:(1)The prokaryotic expression fusion protein MBP-CTB-EGFP owns transmembrane function,and can sensitize mice after being mixed with allergen TM,so it can be used as a mucosal adjuvant for the estabishment of a food allergy animal model;(2)The significant rise of TM-specific IgE,IgG2a,and IgGI in the serum of TM,TM+Abx,and CTB-TM groups,the lesions of small intestinal mucosa,and the up-regulation of Tslp mRNA expression indicated that all three oral sensitization models were successfully constructed.Meanwhile,the most significant changes were observed in the TM+Abx group,indicating that antibiotics can aggravate food allergic reactions;(3)Daily oral administration of LcZhang after 14 days can effectively alleviate the symptoms of food allergy in TM sensitized mice.It mainly includes the decrease of serum IgE levels,the partly repair of damaged intestinal tissue,and the decrease of Tslp and 1133 gene expression.However,the mitigation effect in TM+Abx and CTB-TM groups was poor.It indicates that LcZhang has a personalized effect on alleviating food allergies,and may have different therapeutic effects for different sensitization methods;(4)LcZhang alleviates food allergy symptoms by regulating cytokine secretion,cytokine and transcription factor related genes expression and the proportion of Thl/Th2/Th17 cells,but antibiotics can impair its therapeutic efficacy;(5)LcZhang has different regulatory effects on the mRNA expression of tolerance-related genes in the intestine,maturation and differentiation of T cells,B cells,and DC cells in the spleen,and the distribution and abundance of the gut microbiota.It indicates that antibiotics have disadvantage effects on the production of food allergies and the prevention and treatment by probiotics.This study explored the potential sensitization mechanism of TM,a major allergens in aquatic products,by oral administration,and revealed the effect and preliminary mechanism of LcZhang in alleviating TM allergy,as well as the effects of antibiotics on food allergy and probiotic treatment.The above provides a theoretical basis for further studies of the mechanism of food allergy,and provides new ideas for the prevention and treatment of food allergy,in order to ultimately reduce the occurrence of food allergies.