Previously, we isolated potentially probiotic Ligilactobacillus salivarius strains from the intestines of wakame-fed pigs. The strains were characterized based on their ability to modulate the innate immune responses triggered by the activation of Toll-like receptor (TLR)-3 or TLR4 signaling pathways in intestinal mucosa. In this work, we aimed to evaluate whether nasally administered L. salivarius strains are capable of modulating the innate immune response in the respiratory tract and conferring long-term protection against the respiratory pathogen Streptococcus pneumoniae. Infant mice (3-weeks-old) were nasally primed with L. salivarius strains and then stimulated with the TLR3 agonist poly(I:C). Five or thirty days after the last poly(I:C) administration mice were infected with pneumococci. Among the strains evaluated, L. salivarius FFIG58 had a remarkable ability to enhance the protection against the secondary pneumococcal infection by modulating the respiratory immune response. L. salivarius FFIG58 improved the ability of alveolar macrophages to produce interleukin (IL)-6, interferon (IFN)-γ, IFN-β, tumor necrosis factor (TNF)-α, IL-27, chemokine C-C motif ligand 2 (CCL2), chemokine C-X-C motif ligand 2 (CXCL2), and CXCL10 in response to pneumococcal challenge. Furthermore, results showed that the nasal priming of infant mice with the FFIG58 strain protected the animals against secondary infection until 30 days after stimulation with poly(I:C), raising the possibility of using nasally administered immunobiotics to stimulate trained immunity in the respiratory tract.

The beneficial effect of milk kefir on respiratory heath has been previously demonstrated; however, water kefir and kefiran in the context of respiratory viral infections have not been investigated. Water kefir and kefiran could be alternatives to milk kefir for their application in persons with lactose intolerance or milk allergy and could be incorporated into vegan diets. Using mice models, this work demonstrated that the oral administration of water kefir or kefiran can modulate the respiratory Toll-like receptor (TLR3)-mediated innate antiviral immunity and improve the resistance to respiratory syncytial virus (RSV) infection. The treatment of mice with water kefir or kefiran for 6 days improved the production of interferons (IFN-β and IFN-γ) and antiviral factors (Mx2, OAS1, RNAseL, and IFITM3) in the respiratory tract after the activation of the TLR3 signaling pathway, differentially modulated the balance of pro- and anti-inflammatory cytokines, reduced RSV replication, and diminished lung tissue damage. Maintaining a proper balance between anti-inflammatory and pro-inflammatory mediators is vital for ensuring an effective and safe antiviral immune response, and the results of this work show that water kefir and kefiran would help to maintain that balance promoting a controlled inflammatory response that defends against infection while minimizing tissue damage.

This study evaluated whether the combined Lactiplantibacillus plantarum CRL1506 and MPL16 nasal priming more effectively modulated the Toll-like receptor (TLR)-3- and respiratory syncytial virus (RSV)-mediated respiratory immune responses in mice than single strains. The interaction of single and combined strains with porcine alveolar macrophages (AMs) and porcine respiratory epithelial cells (PBE cells) in the context of TLR3 activation and porcine reproductive and respiratory syndrome virus (PRRSV) was also evaluated. The in vivo studies in mice revealed that the CRL1506 + MPL16 combination was more effective than the individual strains at reducing RSV replication, protecting the lung from TLR3-mediated inflammatory injury and modulating innate antiviral responses, particularly in AMs. In vitro, lactobacilli treatment also increased the resistance of porcine AMs to PRRSV infection. Notably, the CRL1506 + MPL16 combination was not more effective than the single strains in modulating AMs antiviral immunity. Complementary assays in PBE cells revealed that L. plantarum CRL1506 induced higher production of IFN-λ than the MPL16 strain in response to TLR3 activation. Thus, the superior in vivo protection against RSV seen with the L. plantarum CRL1506–MPL16 combination likely reflects complementary actions of lactobacilli: MPL16 would efficiently modulate AMs, whereas CRL1506 would be more effective to target respiratory epithelial cells driving greater IFN-λ production that further boosts AM antiviral activity. The results from the animal models of this work furnish the scientific basis for proposing future human trials to assess the efficacy of the CRL1506 + MPL16 combination in improving respiratory antiviral immunity.

Lacticaseibacillus rhamnosus CRL1505 beneficially modulates the inflammation-coagulation response during respiratory viral infections. This study evaluated the capacity of the peptidoglycan obtained from the CRL1505 strain (PG-Lr1505) to modulate the immuno-coagulative response triggered by the viral pathogen-associated molecular pattern poly(I:C) in the respiratory tract. Adult BALB/c mice were nasally treated with PG-Lr1505 for two days. Treated and untreated control mice were then nasally challenged with poly(I:C). Mice received three doses of poly(I:C) with a 24 h rest period between each administration. The immuno-coagulative response was studied after the last administration of poly(I:C). The challenge with poly(I:C) significantly increased blood and respiratory pro-inflammatory mediators, decreased prothrombin activity (PT), and increased von Willebrand factor (vWF) levels in plasma. Furthermore, tissue factor (TF), tissue factor pathway inhibitor (TFPI), and thrombomodulin (TM) expressions were increased in the lungs. PG-Lr1505-treated mice showed significant modulation of hemostatic parameters in plasma (PT in %, Control = 71.3 ± 3.8, PG-Lr1505 = 94.0 ± 4.0, p < 0.01) and lungs. Moreover, PG-Lr1505-treated mice demonstrated reduced TF in F4/80 cells from lungs, higher pro-inflammatory mediators, and increased IL-10 compared to poly(I:C) control mice (IL-10 in pg/mL, Control = 379.1 ± 12.1, PG-Lr1505 = 483.9 ± 11.3, p < 0.0001). These changes induced by PG-Lr1505 correlated with a significant reduction in lung tissue damage. Complementary in vitro studies using Raw 264.7 cells confirmed the beneficial effect of PG-Lr1505 on poly(I:C)-induced inflammation, since increased IL-10 expression, as well as reduced damage, production of inflammatory mediators, and hemostatic parameter expressions were observed. In addition, protease-activated receptor-1 (PAR1) activation in lungs and Raw 264.7 cells was observed after TLR3 stimulation, which was differentially modulated by PG-Lr1505. The peptidoglycan from L. rhamnosus CRL1505 is able to regulate inflammation, the procoagulant state, and PAR1 activation in mice and macrophages in the context of the activation of TLR3 signaling pathways, contributing to a beneficial modulation of inflammation-hemostasis crosstalk.

Respiratory viral infections remain a major health concern, highlighting the need for strategies that enhance host antiviral defenses. Lacticaseibacillus rhamnosus CRL1505 has demonstrated beneficial immunomodulatory effects in the respiratory tract; however, its direct effects on distinct respiratory cell populations remain incompletely characterized. Here, we evaluated the capacity of live and HK 1505 to modulate antiviral immunity in porcine bronchial epithelial (PBE) cells challenged with SIV and porcine alveolar macrophage (PAM) cells infected with PRRSV. Pretreatment with either live or HK 1505 significantly reduced infectious SIV titers in PBE cells and decreased PRRSV ORF5 expression and viral antigen detection in PAM cells, accompanied by enhanced expression of interferons and antiviral factors in both models. CRL1505 also differentially modulated inflammatory responses according to the cell type. In PAM cells, both treatments enhanced proinflammatory and regulatory cytokines, whereas in PBE cells they selectively increased IL-1β and IL-6 while reducing TNF-α, IL-8, and MCP-1. Negative regulators of innate immune signaling were also differentially modulated in both cell types. Importantly, HK 1505 retained significant antiviral and immunomodulatory activities, inducing responses that were generally similar to those observed with the viable preparation under the experimental conditions evaluated. These findings demonstrate that L. rhamnosus CRL1505 enhances antiviral responses in two distinct respiratory cell models, with differences in immunomodulatory profiles that may reflect the combined influence of cellular and viral contexts.