Immunobiotic Lactobacillus strains reduce small intestinal injury induced by intraepithelial lymphocytes after Toll-like receptor 3 activation

Objective: Intestinal intraepithelial lymphocytes (IELs) play critical roles in disrupting epithelial homeostasis after Toll-like receptor (TLR)-3 activation with genomic rotavirus dsRNA or the synthetic dsRNA analog poly(I:C). The capacity of immunobiotic Lactobacillus rhamnosus CRL1505 (Lr1505) or Lactobacillus plantarum CRL1506 (Lp1506) to beneficially modulate IELs response after TLR3 activation was investigated in vivo using a mice model. Results: Intraperitoneal administration of poly(I:C) induced inflammatory-mediated intestinal tissue damage through the increase of inflammatory cells (CD3⁺NK1.1⁺, CD3⁺CD8αα⁺, CD8αα⁺NKG2D⁺) and pro-inflammatory mediators (TNF-α, IL-1β, IFN-γ, IL-15, RAE1, IL-8). Increased expression of intestinal TLR3, MDA5, and RIG-I was also observed after poly(I:C) challenge. Treatment with Lr1505 or Lp1506 prior to TLR3 activation significantly reduced the levels of TNF-α, IL-15, RAE1, and increased serum and intestinal IL-10. Moreover, CD3⁺NK1.1⁺, CD3⁺CD8αα⁺, and CD8αα⁺NKG2D⁺ cells were lower in lactobacilli-treated mice when compared to controls. The immunomodulatory capacities of lactobacilli allowed a significant reduction of intestinal tissue damage. Conclusions: This work demonstrates the reduction of TLR3-mediated intestinal tissue injury by immunobiotic lactobacilli through the modulation of intraepithelial lymphocytes response. It is a step forward in the understanding of the cellular mechanisms involved in the antiviral capabilities of immunobiotic strains.