The Mucus Binding Factor Is Not Necessary for Lacticaseibacillus rhamnosus CRL1505 to Exert Its Immunomodulatory Activities in Local and Distal Mucosal Sites

Abstract

Both viable and non-viable orally administered Lacticaseibacillus rhamnosus CRL1505 modulate immunity in local (intestine) and distal (respiratory) mucosal sites. So, intestinal adhesion and colonization are not necessary for this probiotic strain to exert its immunomodulatory effects. In this work, a mucus-binding factor knockout CRL1505 strain (ΔmbfCRL1505) was obtained and the lack of binding ability to both intestinal epithelial cells and mucin was demonstrated in vitro. In addition, two sets of in vivo experiments in 6-week-old Balb/c mice were performed to evaluate ΔmbfCRL1505 immunomodulatory activities. (A) Orally administered ΔmbfCRL1505 prior to intraperitoneal injection of the Toll-like receptor 3 (TLR3) agonist poly(I:C) significantly reduced intraepithelial lymphocytes (CD3+NK1.1+CD8αα+) and pro-inflammatory mediators (TNF-α, IL-6 and IL-15) in the intestinal mucosa. (B) Orally administered ΔmbfCRL1505 prior to nasal stimulation with poly(I:C) significantly decreased the levels of the biochemical markers of lung tissue damage. In addition, reduced recruitment of neutrophils and levels of pro-inflammatory mediators (TNF-α, IL-6 and IL-8) as well as increased IFN-β and IFN-γ in the respiratory mucosa were observed in ΔmbfCRL1505-treated mice when compared to untreated control mice. The immunological changes induced by the ΔmbfCRL1505 strain were not different from those observed for the wild-type CRL1505 strain. Although it is generally accepted that the expression of adhesion factors is necessary for immunobiotics to induce their beneficial effects, it was demonstrated here that the mbf protein is not required for L. rhamnosus CRL1505 to exert its immunomodulatory activities in local and distal mucosal sites. These results are a step forward towards understanding the mechanisms involved in the immunomodulatory capabilities of L. rhamnosus CRL1505.

The Mucus-Binding Factor Mediates Lacticaseibacillus rhamnosus CRL1505 Adhesion but Not Immunomodulation in the Respiratory Tract

“…CRL1050 Mbf is highly homologous to Mbf of L. rhamnosus GG [ 21 ]. Recently, we showed that the Mbf protein of L. rhamnosus CRL1505 contributed to adhesion to the extracellular matrix and to porcine intestinal cells [ 16 ]. These previous works clearly demonstrated the role of the Mbf protein in adhesion of lactobacilli to the intestinal mucosa, although its involvement in the adhesion to the respiratory tract was not investigated before.…”

“…L. rhamnosus CRL1505 and Lactiplantibacillus plantarum CRL1506 were obtained from the CERELA culture collection (Tucumán, Argentina). L. rhamnosus Δmbf CRL1505 is a mucus-binding protein knock-out that was constructed and phenotypically checked by Tomotsune et al [ 16 ]. The L. plantarum MPL16 and L. salivarius FFIG58 strains were obtained from the Food and Feed Immunology Group–Tohoku University culture collection (Sendai, Japan).…”

“…Recently, we showed that the L. rhamnosus CRL1505 mbf knock-out mutant ( Δmbf CRL1505) preserved its immunomodulatory functions and was still able to adhere to both mucins and porcine intestinal epithelial (PIE) cells. However, the adhesive abilities of the Δmbf CRL1505 strain were lower than those of the wild type (WT) [ 16 ]. The role of Mbf-containing proteins has been studied in lactobacilli whose natural habitat is the gastrointestinal tract, but the involvement of these proteins in the adhesion of lactobacilli to the respiratory mucosa has not been studied.…”