A peptidic fraction from milk fermented with Lactobacillus helveticus protects mice against Salmonella infection

A peptidic fraction, isolated from milk fermented with Lactobacillus helveticus, was assessed for its ability to bolster the immunity in mice against an oral Salmonella enteritidis challenge. Following four days of feeding with the fraction or saline, mice were challenged with a single Salmonella dose. Mice fed at 0.02 μg day−1 (PO2 group) had higher general health score and survival rate than mice in the control group and in those fed at 0.01 μg day−1. The Salmonella burden in the spleen and liver of mice in the control group was higher than that of mice in the PO2 group. The active fraction up-regulated tumour necrosis factor-alpha (TNF-α) production but had no effect on interferon gamma (IFN-γ) secretion. Pathological studies showed that the fraction was non toxic at a dose of 0.2 μg day−1. Antivirulent and antimicrobial properties of the active fraction were also studied to understand the mechanisms associated with the in vivo effects observed.