Components Secreted by Lactobacillus Fermentum PC1 Inhibit Salmonella Enterica Serotype Typhimurium Induced IL-8 from Intestinal Epithelial Cells

Lactobacillus strains have been shown to confer health benefits to the host including attenuation of intestinal inflammatory responses. However, the health benefits of lactobacilli are strain specific. The aim of this study was to determine whether Lactobacillus fermentum PC1 (PC1) cell wall extract (CW) and the spent culture supernatant (SCS) had the capacity to inhibit IL-8 production by Salmonella enterica serotype Typhimurium (S. Typhimurium) infected epithelial cells. Epithelial cell line, HT-29 was treated with CW or SCS of PC1 both pre- and post-infection with S. Typhimurium and the resultant levels of IL-8 protein was assayed. Both the CW and SCS of PC1 was shown to inhibit S. Typhimurium induced IL 8 production in HT-29 cells in the therapeutic and prophylactic models. Furthermore, a secreted molecule produced by PC1 responsible for this effect was identified and characterized. The molecule was produced in mid-stationary phase of growth. This active component was present in both the cell wall extracts and spent culture medium of PC1. The bioactive molecule(s) had a size of Mr 2-30KDa, was heat stable at 90°C for 30 min, insensitive to lipase, distinct from acetic and lactic acid, and optimal function at pH 4.5. The activity of the molecules was inactivated by Proteinase K, Na-metaperiodate and Trypsin indicating that the molecule(s) was a glycoprotein. The isolation of an immunomodulatory molecule that could be used in the treatment of S. Typhimurium infection would be of great value.