Antiviral innate immunity is differentially modulated by Lactobacillus rhamnosus strains in both intestinal epithelial and antigen presenting cells: role of Toll-like receptors 2 and 9

Abstract

Oral administration of immunobiotic Lactobacillus rhamnosus strains CRL1505 (Lr5) and CRL1506 (Lr6) diminished the occurrence of intestinal infections in children. Therefore, in this study we used the viral pathogen-associated molecular pattern poly(I:C) to mimic the first steps of the antiviral response program elicited by rotavirus and used both non-transformed porcine intestinal epithelial cell line (PIE) and primary cultures of adherent cells isolated from swine Peyer?s patches (PP) as single or combined cultures to evaluate the influence of these immunobiotic bacteria in a context of a viral infection. In these systems, we investigated the modulation of cytokine profiles and activation markers by the strains Lr5 and Lr6 in cells incubated 48 hours with the lactobacilli prior to poly(I:C) challenge. The expression profiles were assessed at the mRNA level by qRT-PCR and at the protein level by flow cytometry. As expected, poly(I:C) administration significantly up-regulated the synthesis of IFN-α, IFN-β, IL-6, TNF-α and MCP-1 in PIE cells. Both Lr5 and Lr6 increased the expression of IL-6 as well as TNF-α via TLR2 activation. In addition, both Lr5 and Lr6 treatments induced a stronger type I IFNs response to poly(I:C) challenge when compared to control cells, being Lr6 the most effective treatment for improving the production of IFN-α and IFN-β in PIE cells. In addition, we observed that this effect was independent from TLR2 or TLR9 signalling. Poly(I:C) enhanced the expression of the surface activation marker CD80/86 as well as the production of IL-12, IFN-γ, IL-1β, IL-6 and IL-10 levels in PP?s derived antigen presenting cells. The pre-incubation with lactobacilli before poly(I:C) challenge differentially increased the expression of MHCII, CD80/86, IL-1β, IL-6, IL-12 and IFN-γ in CD172a-CD11R1low cells, whereas CD172a+CD11R1- and CD172a+CD11R1high cells showed increases in MHCII and IL-10 expression. The effect of Lr5 on antigen presenting cells was significantly stronger (P<0.05) than the one observed for Lr6. In conclusion, this work demonstrate that Lr6 has a marked influence on intestinal epithelial cells and antiviral innate defence mediated by type I IFNs, whereas Lr5 stands out for its influence on intestinal antigen presenting cells.