Immune Modulation by Probiotics

A Novel Probiotic Bacillus subtilis Strain Confers Cytoprotection to Host Pig Intestinal Epithelial Cells during Enterotoxic Escherichia coli Infection

Enteric infections caused by enterotoxic Escherichia coli (ETEC) negatively impact the growth performance of piglets during weaning, resulting in significant economic losses for the producers. With the ban on antibiotic usage in livestock production, probiotics have gained a lot of attention as a potential alternative. However, strain specificity and limited knowledge on the host-specific targets limit their efficacy in preventing ETEC-related postweaning enteric infections. We recently isolated and characterized a novel probiotic Bacillus subtilis bacterium (CP9) that demonstrated antimicrobial activity. Here, we report anti-ETEC properties of CP9 and its impact on metabolic activity of swine intestinal epithelial (IPEC-J2) cells. Our results showed that pre- or coincubation with CP9 protected IPEC-J2 cells from ETEC-induced cytotoxicity. CP9 significantly attenuated ETEC-induced inflammatory response by reducing ETEC-induced nitric oxide production and relative mRNA expression of the Toll-like receptors (TLRs; TLR2, TLR4, and TLR9), proinflammatory tumor necrosis factor alpha, interleukins (ILs; IL-6 and IL-8), augmenting anti-inflammatory granulocyte-macrophage colony-stimulating factor and host defense peptide mucin 1 (MUC1) mRNA levels. We also show that CP9 significantly (P < 0.05) reduced caspase-3 activity, reinstated cell proliferation and increased relative expression of tight junction genes, claudin-1, occludin, and zona occludens-1 in ETEC-infected cells. Finally, metabolomic analysis revealed that CP9 exposure induced metabolic modulation in IPEC J2 cells with the greatest impact seen in alanine, aspartate, and glutamate metabolism; pyrimidine metabolism; nicotinate and nicotinamide metabolism; glutathione metabolism; the citrate cycle (TCA cycle); and arginine and proline metabolism. Our study shows that CP9 incubation attenuated ETEC-induced cytotoxicity in IPEC-J2 cells and offers insight into potential application of this probiotic for ETEC infection control. IMPORTANCE ETEC remains one of the leading causes of postweaning diarrhea and mortality in swine production. Due to the rising concerns with the antibiotic use in livestock, alternative interventions need to be developed. In this study, we analyzed the cytoprotective effect of a novel probiotic strain in combating ETEC infection in swine intestinal cells, along with assessing its mechanism of action. To our knowledge, this is also the first study to analyze the metabolic impact of a probiotic on intestinal cells. Results from this study should provide effective cues in developing a probiotic intervention for ameliorating ETEC infection and improving overall gut health in swine production.

Role of probiotics in prevention and treatment of enteric infections: a comprehensive review

Microorganisms that inhabits human digestive tract affect global health and enteric disorders. Previous studies have documented the effectiveness and mode of action of probiotics and classified as human-friendly biota and a competitor to enteric pathogens. Statistical studies reported more than 1.5 billion cases of gastrointestinal infections caused by enteric pathogens and their long-term exposure can lead to mental retardation, temporary or permanent physical weakness, and leaving the patient susceptible for opportunistic pathogens, which can cause fatality. We reviewed previous literature providing evidence about therapeutic approaches regarding probiotics to cure enteric infections efficiently by producing inhibitory substances, immune system modulation, improved barrier function. The therapeutic effects of probiotics have shown success against many foodborne pathogens and their therapeutic effectiveness has been exponentially increased using genetically engineered probiotics. The bioengineered probiotic strains are expected to provide a better and alternative approach than traditional antibiotic therapy against enteric pathogens, but the novelty of these strains also raise doubts about the possible untapped side effects, for which there is a need for further studies to eliminate the concerns relating to the use and safety of probiotics. Many such developments and optimization of the classical techniques will revolutionize the treatments for enteric infections.

Lactobacillus rhamnosus 2016SWU.05.0601 regulates immune balance in ovalbumin-sensitized mice by modulating expression of the immune-related transcription factors and gut microbiota

BACKGROUND

Probiotics regulate host immune balance, which may reduce immune-related diseases. The effects and mechanisms of Lactobacillus rhamnosus 2016SWU.05.0601 (Lr-0601) on the immune response in ovalbumin (OVA)-sensitized mice were explored.

RESULTS

Lr-0601 reduced serum immunoglobulin (Ig)E and OVA-IgE and attenuated the alteration in lung pathology in OVA-sensitized mice. Lr-0601 blocked OVA-induced up-regulation in serum T helper (Th) 2 and Th17 cytokines but increased the serum levels of Th1 and regulatory T (Treg) cytokines in OVA-sensitized mice. OVA also markedly reduced the protein levels of spleen T-box transcription factor and forkhead/winged helix transcription factor p3, leading to the reduced mRNA expression of interferon-γ and interleukin (IL)-10. By contrast, OVA markedly increased the protein expression of spleen GATA-binding protein 3 and retinoid-related orphan receptor γt, as well as the mRNA expression of spleen IL-4 and IL-17. These changes induced by OVA were reversed by Lr-0601. Moreover, Lr-0601 helped alleviate OVA-induced intestinal microbiota dysbiosis. A correlation was found between specific genera and immune-associated cytokines.

CONCLUSION

The combined results indicate that Lr-0601 modulated the balance of Th1/Th2 and Treg/Th17 in OVA-sensitized mice, which was associated with the regulation of immune-related transcription factors and gut microbiota. Lr-0601 can potentially be used as a probiotic for preventing immune-related diseases. © 2020 Society of Chemical Industry.