Lactobacillus delbrueckii subsp. delbrueckii TUA4408L is able to differentially modulate the innate immune response of porcine intestinal epithelial cells triggered by TLR4 activation. This strain also has a remarkable ability to grow on plant substrates. These two immunological and biotechnological characteristics prompted us to evaluate whether the soymilk by-product okara fermented with the TUA4408L strain can serve as an immunobiotic feed with the ability to beneficially modulate the intestinal immunity of piglets after weaning to improve their productivity. Our in vivo studies demonstrated that the administration of immunobiotic TUA4408L-fermented okara feed significantly increased piglet growth performance and meat quality. These positive effects were associated with the ability of the TUA4408L-fermented okara feed to beneficially modulate both intestinal microbiota and immunity in pigs. The immunobiotic feed improved the abundance of the beneficial bacteria Lactobacillus and Lactococcus in the gut of pigs, reduced blood markers of inflammation, and differentially regulated the expression of inflammatory and regulatory cytokines in the intestinal mucosa. These findings indicate that the immunobiotic TUA4408L-fermented okara feed could be an economical and environmentally friendly option to improve the growth performance and immune health of pigs.

In this article, Ligilactobacillus salivarius FFIG strains, isolated from the intestinal tract of wakame-fed pigs, are characterized according to their potential probiotic properties. Strains were evaluated by studying their interaction with porcine intestinal epithelial (PIE) cells in terms of their ability to regulate toll-like receptor (TLR)-3- or TLR4-mediated innate immune responses, as well as by assessing their adhesion capabilities to porcine epithelial cells and mucins. These functional studies were complemented with comparative genomic evaluations using the complete genome sequences of porcine L. salivarius strains selected from subgroups that demonstrated different “immune” and “adhesion” phenotypes. We found that their immunomodulatory and adhesion capabilities are a strain-dependent characteristic. Our analysis indicated that the differential immunomodulatory and adhesive activities of FFIG strains would be dependent on the combination of several surface structures acting simultaneously, which include peptidoglycan, exopolysaccharides, lipoteichoic acid, and adhesins. Of note, our results indicate that there is no correlation between the immunomodulatory capacity of the strains with their adhesion ability to mucins and epithelial cells. Therefore, in the selection of strains destined to colonize the intestinal mucosa and modulate the immunity of the host, both properties must be adequately evaluated. Interestingly, we showed that L. salivarius FFIG58 functionally modulated the innate immune responses triggered by TLR3 and TLR4 activation in PIE cells and efficiently adhered to these cells. Moreover, the FFIG58 strain was capable of reducing rotavirus replication in PIE cells. Therefore, L. salivarius FFIG58 is a good candidate for further in vivo studying the protective effect of lactobacilli against intestinal infections in the porcine host. We also reported and analyzed, for the first time, the complete genome of several L. salivarius strains that were isolated from the intestine of pigs after the selective pressure of feeding the animals with wakame. Further genomic analysis could be of value to reveal the metabolic characteristics and potential of the FFIG strains in general and of the FFIG58 strain, in particular, relating to wakame by-products assimilation.

Lactiplantibacillus plantarum strains are used in the food industry for their probiotic properties. Some of these bacteria have immunomodulatory effects on the host and are able to improve resistance against different pathogens, including viruses. However, to date, the bacterial genes involved in the immunomodulatory effect are not known. In this work, the complete genomes of L. plantarum MPL16, CRL1506, CRL681 and TL2766 were used to perform comparative genomics with the aim of identifying the genes involved in their differential immunomodulatory effects. L. plantarum WCFS1, a strain with proven probiotic activity, was also used for comparisons. The analysis of the genes involved in the metabolic pathways of the five strains did not reveal differences in the metabolism of amino acids, lipids, nucleotides, cofactors and vitamins, nor in the genes associated with energy metabolism or the biosynthesis of lipoproteins and teichoic acids. However, differences were found between the five strains when considering carbohydrate metabolism pathways, particularly in the presence/absence of glycosylhydrolases and glycosyltransferases. In addition, a great variability was detected in the predicted surface proteins of each L. plantarum strain. These results suggest that the surface molecules expressed in the different strains of L. plantarum could be involved in their differential ability to modulate the innate antiviral immune response.

Lactobacillus delbrueckii subsp. lactis CRL 581 beneficially modulates the intestinal antiviral innate immune response triggered by the Toll-like receptor 3 (TLR3) agonist poly(I:C) in vivo. This study aimed to characterize further the immunomodulatory properties of the technologically relevant starter culture L. delbrueckii subsp. lactis CRL 581 by evaluating its interaction with intestinal epithelial cells and macrophages in the context of innate immune responses triggered by TLR3. Our results showed that the CRL 581 strain was able to adhere to porcine intestinal epithelial (PIE) cells and mucins. The CRL 581 strain also augmented the expression of antiviral factors (IFN-α, IFN-β, Mx1, OAS1, and OAS2) and reduced inflammatory cytokines in PIE cells triggered by TLR3 stimulation. In addition, the influence of L. delbrueckii subsp. lactis CRL 581 on the response of murine RAW macrophages to the activation of TLR3 was evaluated. The CRL 581 strain was capable of enhancing the expression of IFN-α, IFN-β, IFN-γ, Mx1, OAS1, TNF-α, and IL-1β. Of note, the CRL 581 strain also augmented the expression of IL-10 in macrophages. The results of this study show that the high proteolytic strain L. delbrueckii spp. lactis CRL 581 was able to beneficially modulate the intestinal innate antiviral immune response by regulating the response of both epithelial cells and macrophages relative to TLR3 activation.