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Probiotics prevent enterohaemorrhagic Escherichia coli O157 : H7-mediated inhibition of interferon--induced tyrosine phosphorylation of STAT-1

Research Institute, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada

Correspondence
Philip M. Sherman
philip.sherman{at}sickkids.ca

Enterohaemorrhagic Escherichia coli (EHEC) O157 : H7 inhibits interferon (IFN)--stimulated tyrosine phosphorylation of signal transducer and activator of transcription (STAT)-1 in epithelial cells. We determined the effects of probiotics on EHEC-mediated disruption of IFN--stimulated STAT-1 activation in epithelial cell lines. Confluent Intestine 407, HEp-2 and Caco-2 epithelial cells were pre-treated (3 h) with either probiotics or surface-layer proteins derived from Lactobacillus helveticus R0052 prior to infection with EHEC O157 : H7 strain CL56 (m.o.i. 100 : 1, 6 h, 37 °C in 5 % CO₂). Subsequently, cells were washed and stimulated with human recombinant IFN- (50 ng ml^–1, 0.5 h, 37 °C) followed by whole-cell protein extraction and immunoblotting for tyrosine-phosphorylated STAT-1. Relative to uninfected cells, STAT-1-activation was reduced after EHEC O157 : H7 infection. Pre-incubation with the probiotic L. helveticus R0052 followed by EHEC infection abrogated pathogen-mediated disruption of IFN-–STAT-1 signalling. As determined using Transwell inserts, probiotic-mediated protection was independent of epithelial cell contact. In contrast, pre-incubation with boiled L. helveticus R0052, an equal concentration of viable Lactobacillus rhamnosus R0011, or surface-layer proteins (0.14 mg ml^–1) did not restore STAT-1 signalling in EHEC-infected cells. The viable probiotic agent L. helveticus R0052 prevented EHEC O157 : H7-mediated subversion of epithelial cell signal transduction responses.