Effects of the S-layer Protein of Lactobacillus acidophilus on Intestinal Mucosal Immune Function in Mice Infected with Escherichia coli

The influence of the S-layer protein of Lactobacillus acidophilus on the intestinal mucosal immune function in BALB/c mice infected with pathogenic Escherichia coli was investigated. Lactobacillus acidophilus cells without the S-layer protein was obtained using lithium chloride solution(5 M) to extract the S-layer protein from Lactobacillus acidophilus. The SPF grade BALB/c mice were randomly divided into six groups: control group, pathogenic Escherichia coli-infected group, Lactobacillus acidophilus prevention group, Lactobacillus acidophilus treatment group, Lactobacillus acidophilus without S-layer protein prevention group and Lactobacillus acidophilus without S-layer protein treatment group; the experiment was conducted for 14 days. After the mice were sacrificed, the eye blood, intestine, and intestinal mucosa of the mice were collected to examine the changes in morphology of the intestinal mucosa and the differences in the expression of functional factors in it. Compared with control group, the intestinal mucosal morphology changed significantly in pathogenic Escherichia coli-infected group. After the Escherichia coli-infected mice were administered Lactobacillus acidophilus by gavage, the SIg A and IL-8 contents in each mucosa were significantly increased, and the serum contents of TNF-α and IL-1β were significantly reduced compared with the infected group. The result indicated that Lactobacillus acidophilus can reduce the incidence of inflammation and has a better protective effect on the intestinal mucosal immune function than Lactobacillus acidophilus without the S-layer protein. The S-layer protein in Lactobacillus acidophilusplays an important role in its colonization in the intestinal mucosa and the formation of a biological barrier to protect the intestinal mucosal immune function.