Immunomodulating and anti-infective effects of a novel strain of Lactobacillus paracasei that strongly induces interleukin-12

Role of the intestinal microbiota in host defense against respiratory viral infections

Viral infections, including those affecting the respiratory tract, can alter the composition of the intestinal microbiota, which, in turn, can significantly influence both innate and adaptive immune responses, resulting in either enhanced pathogen clearance or exacerbation of the infection, possibly leading to inflammatory complications. A deeper understanding of the interplay between the intestinal microbiota and host immune responses in the context of respiratory viral infections (i.e. the gut-lung axis) is necessary to develop new treatments. This review highlights key mechanisms by which the intestinal microbiota, including its metabolites, can act locally or at distant organs to combat respiratory viruses. Therapeutics aimed at harnessing the microbiota to prevent and/or help treat respiratory viral infections represent a promising avenue for future investigation.

High-protein compound yogurt with quinoa improved clinical features and metabolism of high-fat diet-induced nonalcoholic fatty liver disease in mice

Gut microbiota dysbiosis plays a crucial role in the occurrence and progression of nonalcoholic fatty liver disease (NAFLD), which may be influenced by nutritional supplementation. Quinoa, a type of pseudocereal, has gained prominence due to its high nutritional value and diverse applications. This study aimed to determine whether yogurt containing quinoa can ameliorate NAFLD and alleviate metabolic disorders by protecting against the divergence of gut microbiota. Our findings suggested that quinoa yogurt could significantly reduce the body weight gain and fat tissue weight of high-fat diet (HFD)-fed obese mice. In addition, quinoa yogurt significantly reduced liver steatosis and enhanced glucose homeostasis and insulin sensitivity. Additional research indicates that quinoa yogurt can reduce the levels of proinflammatory cytokines (i.e., tumor necrosis factor α, IL-1β, and IL-6) and inhibit endotoxemia and systemic inflammation. The characteristics of the gut microbiota were then determined by analyzing 16S rRNA. In addition, we discovered that the gut microbiota was disturbed by HFD consumption. Particularly, intestinal probiotics and beneficial intestinal secretions were increased, leading to the expression of glucagon-like peptide-1 in the colon, contributing to NAFLD. Furthermore, endotoxemia and systemic inflammation in HFD-fed mice were restored to the level of control mice when they were fed yogurt and quinoa. Therefore, yogurt containing quinoa can effectively alleviate NAFLD symptoms and may exert its effects via microbiome-gut-liver axis mechanisms. According to some research, the role of the enteric-liver axis may also influence metabolic disorders to reduce the development of NAFLD.

Characterization of Lactic Acid Bacteria from Fermented Fish (pla-paeng-daeng) and Their Cholesterol-lowering and Immunomodulatory Effects

The cholesterol-lowering and immunomodulatory effects and probiotic properties of 25 lactic acid bacteria (LAB) isolated from fermented fish (pla-paeng-daeng) in Thailand were examined in the present study. Based on their phenotypic and genetic characteristics, LAB were identified as Lactiplantibacillus pentosus (Group I, 6 isolates), Lactiplantibacillus argentoratensis (Group II, 1 isolate), Limosilactobacillus fermentum (Group III, 2 isolates), Companilactobacillus pabuli (Group IV, 4 isolates), Companilactobacillus farciminis (Group V, 5 isolates), Companilactobacillus futsaii (Group VI, 6 isolates), and Enterococcus lactis (Group VII, 1 isolate). Lactiplantibacillus pentosus PD3-1 and PD9-2 and Enterococcus lactis PD3-2 exhibited bile salt hydrolase (BSH) activities. The percentage of cholesterol assimilated by all isolates ranged between 21.40 and 54.07%. Bile salt hydrolase-producing isolates tolerated acidic and bile conditions and possessed adhesion properties. They also exerted immunomodulatory effects that affected the production of interleukin-12 (IL-12), interferon-γ (IFN-γ), human β-defensin-2 (hBD-2), and nitric oxide (NO). These isolates meet standard probiotic requirements and exert beneficial effects.

Distribution, cholesterol-lowering and immunomodulation effects of lactic acid bacteria from fermented mussel (Hoi-dong)

Forty-eight lactic acid bacteria (LAB) isolated from fermented mussels in Thailand were evaluated for their probiotic properties, bile salt hydrolase (BSH), cholesterol assimilation and immunomodulatory effects. They were identified as Companilactobacillus formosensis (Group I, 10 isolates), Lentilactobacillus buchneri (Group II, 8 isolates), Lactiplantibacillus plantarum subsp. plantarum (Group III, 16 isolates), Lacticaseibacillus rhamnosus (Group IV, 1 isolate), Pediococcus pentosaceus (Group V, 5 isolates) and P. acidilactici (Group V, 1 isolate), Enterococcus thailandicus (Group VI, 2 isolates), En. hirae (Group VII, 1 isolate), En. durans (Group VI, 1 isolate), Lactococcus lactis subsp. lactis (Group VII, 1 isolate), Lc. lactis subsp. hordinae (Group VII, 1 isolate), and Leuconostoc lactis (Group VIII, 1 isolate), based on their phenotypic and genetic characteristics. Seven isolates, L. plantarum subsp. plantarum LM6-1, LM6-2, LM7-2-2B, LM12-1, LM14-1, LM15-1P and LM15-2 expressed bile salt hydrolase activity. All isolates assimilated cholesterol ranging from 20.73 to 79.40%. BSH-producing isolates were tolerant to acidic and bile conditions and showed the adhesion ability to Caco-2 cells. The BSH-producing and selected isolates showed the immunomodulatory effects to stimulate interleukin-12 (IL-12), interferon-gamma (IFN-γ), human beta defensin-2 (hBD-2) and nitric oxide (NO) production at various levels. Therefore, these results indicated that the isolates meet the standard probiotic criteria and beneficial effects.

Modulation of gut microbiota protects against viral respiratory tract infections: a systematic review of animal and clinical studies

BACKGROUND

Earlier studies suggest that probiotics have protective effects in the prevention of respiratory tract infections (RTIs). Whether such benefits apply to RTIs of viral origin and mechanisms supporting the effect remain unclear.

AIM

To determine the role of gut microbiota modulation on clinical and laboratory outcomes of viral RTIs.

METHODS

We conducted a systematic review of articles published in Embase and MEDLINE through 20 April 2020 to identify studies reporting the effect of gut microbiota modulation on viral RTIs in clinical studies and animal models. The incidence of viral RTIs, clinical manifestations, viral load and immunological outcomes was evaluated.

RESULTS

We included 58 studies (9 randomized controlled trials; 49 animal studies). Six of eight clinical trials consisting of 726 patients showed that probiotics administration was associated with a reduced risk of viral RTIs. Most commonly used probiotics were Lactobacillus followed by Bifidobacterium and Lactococcus. In animal models, treatment with probiotics before viral challenge had beneficial effects against influenza virus infection by improving infection-induced survival (20/22 studies), mitigating symptoms (21/21 studies) and decreasing viral load (23/25 studies). Probiotics and commensal gut microbiota exerted their beneficial effects through strengthening host immunity.

CONCLUSION

Modulation of gut microbiota represents a promising approach against viral RTIs via host innate and adaptive immunity regulation. Further research should focus on next generation probiotics specific to viral types in prevention and treatment of emerging viral RTIs.

Anti-Influenza virus effects of Enterococcus faecalis KH2 and Lactobacillus plantarum SNK12 RNA

Bacterial RNA has recently emerged as an immune-stimulating factor during viral infection. The immune response in an organism is directly related to the progression of virus infections. Lactic acid bacteria in particular have anticancer, bioprotective, and antiallergic effects by modulating immunity. Here, we aimed to demonstrate the effect of bacterial RNA on in vitro production of IL-12, a proinflammatory cytokine, and on in vivo activity against influenza A virus (IFV) infection. Oral administration of heat-killed Enterococcus faecalis KH2 (KH2) or Lactobacillus plantarum SNK12 (SNK) in IFV-infected mice suppressed viral replication and stimulated production of virus-specific antibodies. However, ribonuclease-treated KH2 or SNK abrogated the effect, reducing IL-12 production in vitro and anti-IFV effects in vivo. Taken together, KH2 or SNK showed antiviral effects in vivo when administered orally, and the RNAs of KH2 and SNK play a part in these effects, despite the phylogenetic differences between the bacteria.

Probiotics in Treatment of Viral Respiratory Infections and Neuroinflammatory Disorders

Inflammation is a biological response to the activation of the immune system by various infectious or non-infectious agents, which may lead to tissue damage and various diseases. Gut commensal bacteria maintain a symbiotic relationship with the host and display a critical function in the homeostasis of the host immune system. Disturbance to the gut microbiota leads to immune dysfunction both locally and at distant sites, which causes inflammatory conditions not only in the intestine but also in the other organs such as lungs and brain, and may induce a disease state. Probiotics are well known to reinforce immunity and counteract inflammation by restoring symbiosis within the gut microbiota. As a result, probiotics protect against various diseases, including respiratory infections and neuroinflammatory disorders. A growing body of research supports the beneficial role of probiotics in lung and mental health through modulating the gut-lung and gut-brain axes. In the current paper, we discuss the potential role of probiotics in the treatment of viral respiratory infections, including the COVID-19 disease, as major public health crisis in 2020, and influenza virus infection, as well as treatment of neurological disorders like multiple sclerosis and other mental illnesses.

Exclusive use of digital PCR allows an absolute assay of heat-killed Lactobacilli in foods targeting multiple copies of 16S rDNA

The real-time PCR (qPCR) and digital PCR (dPCR) to amplify a single-copy of house-keeping genes (i.e., hsp60, pheS or tuf) are used for the assay of limited microbial species. In general, with a single-copy gene, there are obviously varied DNA sequences for even the same microbial species, which could cause difficulties with design of primers and probes for PCR when targeting various single copy genes. In general, for identification by dPCR (as a representative case: Lactobacillus paracasei), accumulated DNA sequence information of 16S rDNA, which is much more frequently used, should be targeted. In contrast, next-generation sequencing revealed that there are five copies of 16S rDNA in a live L. paracasei MCC1849. Therefore, we aimed to reveal, if heat-killed L. paracasei supplemented in nutritional foods that aid the host immune system have the relevant five copies per chromosomal DNA, and if the relevant copies remain unchanged on the same chromosomal DNA or remain to be different chromosomal DNA fragments. So, we revealed the actual distribution of the potential original five copies of 16S rDNA using our innovative dPCR, in which both 16S rDNA and hsp60 genes were simultaneously elongated. The molecular ratios of 16S rDNA/hsp60 dispersed in the dPCR chip were then estimated. The 16S rDNA/hsp60 molecular ratios of the heat-killed L. paracasei in foods, resultantly ranged from 5.0 to 7.2, being the same or higher than that of the five copies determined by next-generation sequencing. The 16S rDNA copy number/ratio indicated the chromosomal DNA molecular number and the associated cell number. As significance, different nutritional foods could potentially cause the loss of chromosomal DNA of supplemented beneficial microbes to a much greater degree. Our absolute dPCR does not require standard correlative samples for the estimation of final products. The estimation principle of the ratio of 16S rDNA/a house-keeping single-copy gene by our absolute dPCR could lead to a useful and accurate assay for various nutritional foods.

Effects of probiotic supplementation on natural killer cell function in healthy elderly individuals: a meta-analysis of randomized controlled trials

To evaluate evidence for the role of probiotic supplementation in enhancing natural killer (NK) cell function in healthy elderly individuals. Five electronic databases were searched, and references of included articles and eligible reviews up to December 2019, with English language and human subject restrictions, were examined. Two independent reviewers identified randomized control trials (RCTs) of probiotic supplementation influencing NK cell function in healthy elderly individuals, assessed the quality of every article, and extracted data for subsequent meta-analysis. We identified six eligible trials including 364 healthy elderly subjects. Trials were heterogeneous in study design and probiotic supplementation (including genus, strain, dose, and duration). Five trials used Lactobacillus interventions alone or in combination with Bifidobacterium. Only one trial focused on Bacillus coagulans. The duration of supplementation ranged from 3 to 12 weeks, and the doses, from 1 × 10⁹ to 4 × 10¹⁰ colony-forming units. Pooling data of eligible trials showed that probiotics significantly (P < 0.05) increased NK cell activity in healthy elderly individuals (standardized mean difference = 0.777, 95% confidence interval: 0.187‒1.366, P = 0.01, I² = 84.6%). Although we obtained a significant outcome, the data do not provide convincing evidence for associations between probiotic supplementation and enhancement of NK cell function, given the small final number and very large heterogeneity. More RCTs with sufficient sample sizes and long-term follow-up are needed to focus on optimal probiotic dose, species, and duration of supplementation for healthy elderly individuals.

Galectin-9 Induced by Dietary Probiotic Mixture Regulates Immune Balance to Reduce Atopic Dermatitis Symptoms in Mice

Probiotics can be an effective treatment for atopic dermatitis (AD), while their mechanism of action is still unclear. Here, we induced AD in mice with 2,4-dinitrochlorobenzene and administrated YK4, a probiotic mixture consisting of Lactobacillus acidophilus CBT LA1, L. plantarum CBT LP3, Bifidobacterium breve CBT BR3, and B. lactis CBT BL3. Then, we have validated the underlying mechanism for the alleviation of AD by YK4 from the intestinal and systematic immunological perspectives. Administration of YK4 in AD mice alleviated the symptoms of AD by suppressing the expression of skin thymic stromal lymphopoietin and serum immunoglobulin E eliciting excessive T-helper (Th) 2 cell-mediated responses. YK4 inhibited Th2 cell population through induce the proportion of Th1 cells in spleen and Treg cells in Peyer's patches and mesenteric lymph node (mLN). CD103⁺ dendritic cells (DCs) in mLN and the spleen were significantly increased in AD mice administered with YK4 when compared to AD mice. Furthermore, galectin-9 was significantly increased in the gut of AD mice administered with YK4. In vitro experiments were performed using bone marrow-derived DCs (BMDC) and CD4⁺ T cells to confirm the immune mechanisms of YK4 and galectin-9. The expression of CD44, a receptor of galectin-9, together with programmed death-ligand 1 was significantly upregulated in BMDCs following treatment with YK4. IL-10 and IL-12 were upregulated when BMDCs were treated with YK4. Cytokines together with co-receptors from DCs play a major role in the differentiation and activation of CD4⁺ T cells. Proliferation of Tregs and Th1 cell activation were enhanced when CD4⁺T cells were co-cultured with YK4-treated BMDCs. Galectin-9 appeared to contribute at least partially to the proliferation of Tregs. The results further suggested that DCs treated with YK4 induced the differentiation of naïve T cells toward Th1 and Tregs. At the same time, YK4 alleviated AD symptoms by inhibiting Th2 response. Thus, the present study suggested a potential role of YK4 as an effective immunomodulatory agent in AD patients.

Orally administered heat-killed Lactobacillus paracasei MCC1849 enhances antigen-specific IgA secretion and induces follicular helper T cells in mice

Antigen-specific immunoglobulin (Ig) A plays a major role in host defense against infections in gut mucosal tissue. Follicular helper T (Tfh) cells are located in germinal centers and promote IgA production via interactions with germinal center B cells. Several studies have demonstrated that some lactic acid bacteria (LAB) strains activate the host’s acquired immune system, inducing IgA secretion in the intestine. However, the precise molecular mechanisms underlying the effects of LAB on IgA production and Tfh cells are not fully resolved. Lactobacillus paracasei MCC1849 is a probiotic strain isolated from the intestine of a healthy adult. In this study, we investigated the effects of orally administered heat-killed MCC1849 on IgA production in the intestine and on Tfh cell induction in vivo. We found that orally administered MCC1849 induced antigen-specific IgA production in the small intestine, serum and lungs. We also observed that MCC1849 increased the proportion of IgA⁺ B cells and Tfh cells in Peyer’s patches (PPs). In addition, MCC1849 increased the gene expression of IL-12p40, IL-10, IL-21, STAT4 and Bcl-6 associated with Tfh cell differentiation. These results suggest that orally administered MCC1849 enhances antigen-specific IgA production and likely affects Tfh cell differentiation in PPs.

Role of the intestinal microbiota in the immunomodulation of influenza virus infection

Prevention and treatment measures against influenza virus infection remain limited, and alternative host protection strategies are badly needed. In this review, we discuss the regulatory role of intestinal microbiota in influenza infections, and present the latest evidence for strategies seeking to harness gut microbiota for the management of influenza infections.

RNA and a cell wall component of Enterococcus faecalis IC-1 are required for phagocytosis and interleukin 12 production by the mouse macrophage cell line J774.1

Enterococcus faecalis is a resident lactic acid bacterium in the human intestine. Its immunostimulatory action was reported to be enhanced by heat sterilization. To investigate its beneficial actions, we evaluated the ability of 10 E. faecalis strains to induce interleukin-12 (IL-12) production in a mouse macrophage cell line, J774.1 and found that the strain, E. faecalis IC-1, had a potent IL-12-inducing ability. Furthermore, we investigated the underlying mechanism by treating IC-1 cells with RNase or lysozyme. Its activity almost disappeared and an antagonist of Toll-like receptor (TLR) 7 inhibited this activity. Moreover, lysozyme-treated IC-1 bacteria were not phagocytized by J774.1 cells, and did not induce IL-12 production. Based on our results, we propose that macrophages recognize the cell wall components of IC-1, leading to phagocytosis. The IC-1 RNA is then recognized by TLR7, which induces the production of IL-12.

Immune Response of Healthy Adults to the Ingested Probiotic Lactobacillus casei Shirota

Daily ingestion of a probiotic drink containing Lactobacillus casei Shirota (LcS; 1.3 × 10¹⁰ live cells) by healthy adults for (1) 4-week LcS, (2) 6-week discontinuation of LcS and (3) a final 4 weeks of LcS was investigated. There was a significant increase in expression of the T cell activation marker CD3⁺ CD69⁺ in ex vivo unstimulated blood cells at weeks 10 and 14, and there was a significant increase in the NK cell marker CD3⁺ CD16/56⁺ in ex vivo unstimulated blood cells at weeks 4, 10 and 14. Expression of the NK cell activation marker CD16/56⁺ CD69⁺ in ex vivo unstimulated blood cells was 62% higher at week 10 and 74% higher at week 14. Intracellular staining of IL-4 in ex vivo unstimulated and PMA-/ionomycin-stimulated CD3⁺ β7⁺ integrin blood cells was significantly lower at weeks 10 and 14. Intracellular staining of IL-12 in ex vivo unstimulated and LPS-stimulated CD14⁺ blood cells was significantly lower at weeks 4, 10 and 14. Intracellular staining of TNF-α in LPS-stimulated CD14⁺ blood cells was significantly lower at weeks 4, 10 and 14. Mucosal salivary IFN-γ, IgA1 and IgA2 concentrations were significantly higher at week 14, but LcS did not affect systemic circulating influenza A-specific IgA or IgG and tetanus-specific IgG antibody levels. In addition to the decrease in CD3⁺ β7⁺ integrin cell IL-4 and a reduced CD14⁺ cell pro-inflammatory cytokine profile, at week 14 increased expression of activation markers on circulating T cells and NK cells and higher mucosal salivary IgA1 and IgA2 concentration indicated a secondary boosting effect of LcS.

Lactococcus lactis subsp. lactis JCM 5805 activates natural killer cells via dendritic cells

Lactococcus lactis subsp. lactis JCM 5805 (JCM5805) has been shown to stimulate plasmacytoid dendritic cells (pDC). Here, we investigated the effect of JCM5805 on NK cells. In vitro studies suggested that JCM5805 activated natural killer (NK) cells via dendritic cells including pDC. Furthermore, the oral administration of JCM5805 enhanced the cytotoxic activity of NK cells.

Mechanisms and therapeutic effectiveness of lactobacilli

The gut microbiome is not a silent ecosystem but exerts several physiological and immunological functions. For many decades, lactobacilli have been used as an effective therapy for treatment of several pathological conditions displaying an overall positive safety profile. This review summarises the mechanisms and clinical evidence supporting therapeutic efficacy of lactobacilli. We searched Pubmed/Medline using the keyword ‘Lactobacillus’. Selected papers from 1950 to 2015 were chosen on the basis of their content. Relevant clinical and experimental articles using lactobacilli as therapeutic agents have been included. Applications of lactobacilli include kidney support for renal insufficiency, pancreas health, management of metabolic imbalance, and cancer treatment and prevention. In vitro and in vivo investigations have shown that prolonged lactobacilli administration induces qualitative and quantitative modifications in the human gastrointestinal microbial ecosystem with encouraging perspectives in counteracting pathology-associated physiological and immunological changes. Few studies have highlighted the risk of translocation with subsequent sepsis and bacteraemia following probiotic administration but there is still a lack of investigations on the dose effect of these compounds. Great care is thus required in the choice of the proper Lactobacillus species, their genetic stability and the translocation risk, mainly related to inflammatory disease-induced gut mucosa enhanced permeability. Finally, we need to determine the adequate amount of bacteria to be delivered in order to achieve the best clinical efficacy decreasing the risk of side effects.