Multistrain probiotic modulation of intestinal epithelial cells' immune response to a double-stranded RNA ligand, poly(i·c).

A commercially available product containing three probiotic bacterial strains (Lactobacillus helveticus R0052, Bifidobacterium longum subsp. infantis R0033, and Bifidobacterium bifidum R0071) was previously shown in animal trials to modulate both TH1 and TH2 immune responses. Clinical studies on this combination of bacteria have also shown positive health effects against seasonal winter diseases and rotavirus infection. The goal of this study was to use a well-established in vitro intestinal epithelial (HT-29) cell model that has been shown to constitutively express double-stranded RNA (dsRNA) sensors (Toll-like receptor 3 [TLR3], retinoic acid-inducible gene I, melanoma differentiation-associated gene 5, and dsRNA-activated protein kinase). By using the HT-29 cell model, we wanted to evaluate whether or not this combination of three bacteria had the capacity to immune modulate the host cell response to a dsRNA ligand, poly(I·C). Using a custom-designed, two-color expression microarray targeting genes of the human immune system, we investigated the response of HT-29 cells challenged with poly(I·C) both in the presence and in the absence of the three probiotic bacteria. We observed that the combination of the three bacteria had a major impact on attenuating the expression of genes connected to proinflammatory TH1 and antiviral innate immune responses compared to that obtained by the poly(I·C)-only challenge. Major pathways through which the multistrain combination may be eliciting its immune-modulatory effect include the TLR3 domain-containing adapter-inducing beta interferon (TRIF), mitogen-activated protein kinase, and NF-κB signaling pathways. Such a model may be useful for selecting potential biomarkers for the design of future clinical trials.