Probiotics and immunology: separating the wheat from the chaff

Lactococcus lactis subsp. cremoris YRC3780 modifies function of mesenteric lymph node dendritic cells to modulate the balance of T cell differentiation inducing regulatory T cells

Introduction

The intestinal immune system plays a pivotal role in the induction of immune responses against food. In the case of T cell response, dendritic cells (DCs) are especially important. However, the regulation of immune responses to food by intestinal DCs has been poorly described. In this study, we analyzed the effect of Lactococcus lactis subsp. cremoris YRC3780, a lactic acid bacterial strain isolated from kefir, a traditional fermented milk product, on the immune responses induced by antigen presentation by intestinal DCs to T cells as well as the mechanism of action of these immunomodulatory effects. It has been shown that L. cremoris YRC3780 ameliorates the symptoms of pollinosis in both animal and human studies.

Methods

CD11c+ cells from mesenteric lymph nodes (MLNs) of BALB/c mice were cultured as MLN DCs with L. cremoris YRC3780 and expression of genes inducing regulatory T cells (Tregs) was examined by qPCR. In addition, MLN DCs were cocultured with CD4+ T cells from DO11.10 transgenic mice expressing an ovalbumin (OVA)-specific TCR and the OVA antigen peptide and L. cremoris YRC3780. Induction of Tregs was examined by flow cytometry, gene expression was analyzed by DNA microarray and qPCR, and the production of cytokines was measured by ELISA. MLN DCs from TLR2-deficient mice and components of L. cremoris YRC3780 were used to examine the recognition of YRC3780 by MLN DCs.

Results

L. cremoris YRC3780 enhanced the expression of genes involved in Treg induction in MLN DCs and induced Foxp3+CD4+T cells in an MLN DC and CD4+ T-cell co-culture system. The effect on MLN DCs was likely mediated by receptors other than TLR2. Together with microarray analyses of CD4+ T cell gene expression and cytokine ELISA, it was demonstrated that L. cremoris YRC3780 promoted the induction of Th1 and Tregs, and regulated the balance of Th1/Th2 and Treg/Th17 cells involving multiple genes via the antigen-presentation of MLN DCs.

Discussion

Our findings provide insights into the modulation of intestinal immune responses mediated by DCs and the antiallergic effects of lactic acid bacteria.

L. plantarum and L. lactis as a promising agent in treatment of inflammatory bowel disease and colorectal cancer

It has been understood for nearly a century that patients with intestinal inflammatory disease (IBD) have a higher risk of developing colorectal cancer (CRC). Recently, two species of lactic acid bacteria, Lactobacillus plantarum and Lactococcus lactis, have been investigated as therapeutic agents for IBD. These bacteria have been shown to survive gastric transit, to adhere and colonize in the intestinal tract of humans and modulate the intestinal microbiota and immune response. L. plantarum and L. lactis might be used as multifunctional drugs for the treatment of IBD and the prevention or treatment of CRC. This article summarizes current knowledge of L. plantarum and L. lactis as therapeutic and preventative agents for IBD and CRC, respectively.

Potential role of gut microbiota in prostate cancer: immunity, metabolites, pathways of action?

The gut microbiota helps to reveal the relationship between diseases, but the role of gut microbiota in prostate cancer (PCa) is still unclear. Recent studies have found that the composition and abundance of specific gut microbiota are significantly different between PCa and non-PCa, and the gut microbiota may have common and unique characteristics between different diseases. Intestinal microorganisms are affected by various factors and interact with the host in a variety of ways. In the complex interaction model, the regulation of intestinal microbial metabolites and the host immune system is particularly important, and they play a key role in maintaining the ecological balance of intestinal microorganisms and metabolites. However, specific changes in the composition of intestinal microflora may promote intestinal mucosal immune imbalance, leading to the formation of tumors. Therefore, this review analyzes the immune regulation of intestinal flora and the production of metabolites, as well as their effects and mechanisms on tumors, and briefly summarizes that specific intestinal flora can play an indirect role in PCa through their metabolites, genes, immunity, and pharmacology, and directly participate in the occurrence, development, and treatment of tumors through bacterial and toxin translocation. We also discussed markers of high risk PCa for intestinal microbiota screening and the possibility of probiotic ingestion and fecal microbiota transplantation, in order to provide better treatment options for clinic patients. Finally, after summarizing a number of studies, we found that changes in immunity, metabolites.

The role of the gut microbiota and probiotics associated with microbial metabolisms in cancer prevention and therapy

Cancer is the second leading cause of elevated mortality worldwide. Thus, the development of drugs and treatments is needed to enhance the survival rate of the cancer-affected population. Recently, gut microbiota research in the healthy development of the human body has garnered widespread attention. Many reports indicate that changes in the gut microbiota are strongly associated with chronic inflammation-related diseases, including colitis, liver disease, and cancer within the intestine and the extraintestinal tract. Different gut bacteria are vital in the occurrence and development of tumors within the gut and extraintestinal tract. The human gut microbiome has significant implications for human physiology, including metabolism, nutrient absorption, and immune function. Moreover, diet and lifestyle habits are involved in the evolution of the human microbiome throughout the lifetime of the host and are involved in drug metabolism. Probiotics are a functional food with a protective role in cancer development in animal models. Probiotics alter the gut microbiota in the host; thus, beneficial bacterial activity is stimulated, and detrimental activity is inhibited. Clinical applications have revealed that some probiotic strains could reduce the occurrence of postoperative inflammation among cancer patients. An association network was constructed by analyzing the previous literature to explore the role of probiotics from the anti-tumor perspective. Therefore, it provides direction and insights for research on tumor treatment.

In vivo evidence of the prevents DSS-induced colitis of Lactiplantibacillus plantarum L15

Ulcerative colitis (UC) is challenging to treat and severely impacts patients and families. A previous study reported immunomodulatory and reduction of pro-inflammatory properties for the Lactiplantibacillus plantarum L15. This study aimed to analyze the preventive properties and mechanistic actions in an in vivo colitis model. The histopathological alteration, inflammation cytokines, and intestinal barrier function were analyzed. Subsequently, the cecal gut microbiota contents and products from different groups were detected. Finally, gene expressions related to the NF-κB signaling process were evaluated. L. plantarum L15 significantly decreased disease activity index (DAI), myeloperoxidase activity (MPO), pro-inflammatory cytokine (TNF-α, IL-1β, and IL-6) level, and increased weight change, colon length, and production of inflammation-suppressing cytokines. Furthermore, this strain supplementation substantially increased ZO-1, Occludin, and Claudin-1, and MUC2 mRNA expression levels with a corresponding decrease in serum lipopolysaccharide and D-lactic acid contents. In addition, L. plantarum L15 improved gut microbiota composition and increased short-chain fatty acid (SCFAs) in the colon content, which significantly reduced the transfer of NF-κB p65 to the nucleus. Our findings provide a theoretical basis for L. plantarum L15 as a preventive candidate for UC.

Antiviral Effects and Underlying Mechanisms of Probiotics as Promising Antivirals

Probiotics exert a variety of beneficial effects, including maintaining homeostasis and the balance of intestinal microorganisms, activating the immune system, and regulating immune responses. Due to the beneficial effects of probiotics, a wide range of probiotics have been developed as probiotic agents for animal and human health. Viral diseases cause serious economic losses to the livestock every year and remain a great challenge for animals. Moreover, strategies for the prevention and control of viral diseases are limited. Viruses enter the host through the skin and mucosal surface, in which are colonized by hundreds of millions of microorganisms. The antiviral effects of probiotics have been proved, including modulation of chemical, microbial, physical, and immune barriers through various probiotics, probiotic metabolites, and host signaling pathways. It is of great significance yet far from enough to elucidate the antiviral mechanisms of probiotics. The major interest of this review is to discuss the antiviral effects and underlying mechanisms of probiotics and to provide targets for the development of novel antivirals.

Postbiotics Enhance NK Cell Activation in Stress-Induced Mice through Gut Microbiome Regulation

Recent studies have revealed that probiotics and their metabolites are present under various conditions; however, the role of probiotic metabolites (i.e., postbiotics in pathological states) is controversial. Natural killer (NK) cells play a key role in innate and adaptive immunity. In this study, we examined NK cell activation influenced by a postbiotics mixture in response to gut microbiome modulation in stress-induced mice. In vivo activation of NK cells increased in the postbiotics mixture treatment group in accordance with Th1/Th2 expression level. Meanwhile, the Red Ginseng treatment group, a reference group, showed very little expression of NK cell activation. Moreover, the postbiotics mixture treatment group in particular changed the gut microbiome composition. Although the exact role of the postbiotics mixture in regulating the immune system of stress-induced mice remains unclear, the postbiotics mixture-induced NK cell activation might have affected gut microbiome modulation.

Benefit of Dietary Supplementation with Bacillus subtilis BYS2 on Growth Performance, Immune Response, and Disease Resistance of Broilers

A strain of Bacillus subtilis (B. subtilis) BYS2 was previously isolated from Mount Tai, which is located in Tai'an City in the Shandong Province of China. The strain was then stored in the Environmental Microbiology Laboratory at Shandong Agricultural University. To evaluate the effect of the bacterium preparation in broiler production, we fed the bacterium (10⁶ CFU/g) to 1-day-old broilers and continued this feeding for 6 weeks to analyze its effect on growth and immune performance. We found that the average weight of the bacterium-fed group increased by 17.19% at weeks 5 compared to the control group (P < 0.05). The height of the villi in the duodenum and jejunum and the ratio of villi to crypt were significantly increased in the bacterium-fed group at weeks 5 (P < 0.05). Also, the IgG in the serum of broilers in the experimental group increased by 31.60% (P < 0.05) and IgM 30.52% (P < 0.05) compared with those in the control group. The expressions of the major pattern recognition receptors (PRRs), antiviral proteins, pro-inflammatory cytokines, and β-defensins were significantly higher than those in the control group (P < 0.05). Meanwhile, the bursa immune organ indices of broilers in the experimental group were significantly higher than those in the control group (P < 0.05). Also, after 5 weeks of continuous feeding, when infected with Escherichia coli (E. coli) O1K1 and Newcastle disease virus (NDV) F48E8, the content of bacteria and virus in tissues and organs of the experimental group decreased significantly, and the survival rate of infected chickens increased by 31.1% and 17.7%, respectively (P < 0.05). These results show that the anti-infective B. subtilis BYS2 could, to some extent, replace antibiotics to promote growth, improve innate immunity, and enhance disease resistance in broilers.

A Potential Prophylactic Probiotic for Inflammatory Bowel Disease: The Overall Investigation of Clostridium tyrobutyricum ATCC25755 Attenuates LPS-Induced Inflammation via Regulating Intestinal Immune Cells

SCOPE

This study aims to roundly investigate whether Clostridium tyrobutyricum (Ct) alleviates inflammation via regulating immune cells in the small intestines.

METHODS AND RESULTS

Mice are pre-treated with different concentrations of Ct follow by LPS stimulation. Ct maintains the mice body weight under inflammation. In response to LPS, 10⁷ CFU mL^-1 Ct decreases the mRNA expression of inflammatory cytokines in the duodenum, while 10⁸ CFU mL^-1 Ct reduces inflammatory cytokines expression in both duodenum and ileum and protected intestinal morphology. The small intestinal immune cells are analyzed using flow cytometry. Ct decreases the numbers of macrophages and mast cells in the intestines in response to LPS. In the duodenum, Ct enhances dentritic cells (DCs), regulatory T cells (Tregs), and T helper cell 17 (Th17) proportions. Ct decreases DCs and Tregs proportions, while enhances Th17 numbers in the ileum. The underlying mechanism of Ct in preventing inflammation may rely on the physiological immune cell composition of the intestines. In response to LPS, Ct may mainly stimulate Tregs via activating DCs in the duodenum while trigger Th17 cells in the ileum, thereby maintaining the intestinal homeostasis.

CONCLUSION

Ct alleviates the LPS-induce inflammation via regulating different immune cell types in the small intestines, highlighting that Ct is a potential prophylactic probiotic in intestinal diseases.

Interleukin-8 gene expression and apoptosis induced by Salmonella Typhimurium in the presence of Bacillus probiotics in the epithelial cell

AIMS

This study aimed to evaluate the effects of three Bacillus probiotics on Salmonella Typhimurium, and interleukin-8 (IL-8) gene expression in the co-culture of the Bacillus and the pathogen in vitro.

METHODS AND RESULTS

Bacillus subtilis, Bacillus indicus and Bacillus coagulans were initially turned to spore and heat-inactivated forms. The cellular damages of the probiotics on the HT-29 cells were investigated individually and in combination with S. Typhimurium using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and fluorescence assays. To extract cell free supernatants (CFS) of the probiotics, they were cultured in selective media. The inhibitory activity of CFSs were then assayed against the pathogen. The gene expression of IL-8 of the HT-29 cells was evaluated by real-time PCR in all the groups. The results showed that the CFSs of three probiotics could inhibit the growth of S. Typhimurium by more than 50%. Inhibitory effects of B. indicus and B. subtilis CFSs were related to the production of pepsin-sensitive compounds, except B. coagulans in which the high inhibitory effect was due to organic acids. The spores of the three probiotics and the heat-inactivated forms of B. subtilis and B. coagulans could reduce the cytotoxicity of S. Typhimurium. The cell viability also increased applying both forms probiotics against the pathogen. In all co-culture groups, the IL-8 gene expression induced by S. Typhimurium was reduced.

CONCLUSIONS

The three Bacillus probiotics can be considered as proper candidates for the prevention and treatment of S. Typhimurium food poisoning.

SIGNIFICANCE AND IMPACT OF THE STUDY

Applying probiotics as live bacteria is universally noted in foods. This study tried to discover the effects of Bacillus probiotics in the form of spore or even heat-killed bacteria against S. Typhimurium and evaluate ratio of IL-8 gene expression in cell culture. The most effective Bacillus probiotic will be recommended. This approach will help to use probiotics as nonvegetative cells in foods to fight gastrointestinal pathogens.

The immunomodulatory effects of probiotics on respiratory viral infections: A hint for COVID-19 treatment?

Respiratory virus infections are among the most prevalent diseases in humans and contribute to morbidity and mortality in all age groups. Moreover, since they can evolve fast and cross the species barrier, some of these viruses, such as influenza A and coronaviruses, have sometimes caused epidemics or pandemics and were associated with more serious clinical diseases and even mortality. The recently identified Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a Public Health Emergency of International concern and has been associated with rapidly progressive pneumonia. To ensure protection against emerging respiratory tract infections, the development of new strategies based on modulating the immune responses is essential. The use of probiotic components has substantially increased due to their effects on immune responses, in particular on those that occur in the upper/lower respiratory tract. Superinduction of inflammatory reaction, known as a cytokine storm, has been correlated directly with viral pneumonia and serious complications of respiratory infections. In this review, probiotics, as potential immunomodulatory agents, have been proposed to improve the host's response to respiratory viral infections. In addition, the effects of probiotics on different aspects of immune responses and their antiviral properties in both pre-clinical and clinical contexts have been described in detail.

Potential Immunomodulatory Activity of a Selected Strain Bifidobacterium bifidum H3-R2 as Evidenced in vitro and in Immunosuppressed Mice

The microbiota is directly involved in the development and modulation of the intestinal immune system. In particular, members of the genus Bifidobacterium play a primary role in immune regulation. In the present study, Bifidobacterium bifidum H3-R2 was screened from 15 bifidobacterium strains by in vitro experiment, showing a positive tolerance to digestive tract conditions, adhesion ability to intestinal epithelial cells and a regulatory effect on immune cell activity. Immunostimulatory activity of B. bifidum H3-R2 was also elucidated in vivo in cytoxan (CTX)-treated mice. The results showed that the administration of B. bifidum H3-R2 ameliorated the CTX-induced bodyweight loss and imbalanced expression of inflammatory cytokines, enhanced the production of secretory immunoglobulin A (SIgA), and promoted splenic lymphocyte proliferation, natural killer (NK) cell activity and phagocytosis of macrophages in immunosuppressed mice. In addition, B. bifidum H3-R2 restored injured intestinal mucosal, and increased the villus length and crypt depth in CTX-treated mice. The results could be helpful for understanding the functions of B. bifidum H3-R2, supporting its potential as a novel probiotic for immunoregulation.

Immune Responses Raised in an Experimental Colon Carcinoma Model Following Oral Administration of Lactobacillus casei

The role of dietary probiotic strains on host anticancer immune responses against experimental colon carcinoma was investigated. We have previously shown that Lactobacillus casei administration led to tumor growth suppression in an experimental colon cancer model. Here, we investigated the underlying immune mechanisms involved in this tumorgrowth inhibitory effect. BALB/c mice received daily live lactobacilli per os prior to the establishment of a syngeneic subcutaneous CT26 tumor. Tumor volume, cytokine production, T cell differentiation and migration, as well as tumor cell apoptosis were examined to outline potential immunomodulatory effects following L. casei oral intake. Probiotic administration in mice resulted in a significant increase in interferon gamma (IFNγ), Granzyme B and chemokine production in the tumor tissue as well as enhanced CD8⁺ T cell infiltration, accompanied by a suppression of tumor growth. Cytotoxic activity against cancer cells was enhanced in probioticfed compared to control mice, as evidenced by the elevation of apoptotic markers, such as cleaved caspase 3 and poly (ADPribose) polymerase 1 (PARP1), in tumor tissue. Oral administration of Lactobacillus casei induced potent Th1 immune responses and cytotoxic T cell infiltration in the tumor tissue of tumorbearing mice, resulting in tumor growth inhibition. Thus, the microorganism may hold promise as a novel dietary immunoadjuvant in raising protective anticancer immune responses.

Biosurfactants from probiotic bacteria: A review

Among microorganisms, bacteria are the main group of biosurfactant-producing organisms. Different types of bacteria including Pseudomonas sp., Acinetobacter sp., Bacillus sp., and Arthrobacter sp. are among the most commonly studied bacteria in the realm of scientific research. However, due to the pathogenic nature of the producing organisms, the application of these compounds is restricted, therefore, not suitable for use in food-related industries. Given that probiotic bacteria impact human health, applying probiotics as nonpathogenic and safe organisms have gained much attention for the production of biosurfactants in recent years. Most biosurfactants obtained from probiotic bacteria are related to a number of lactic acid bacteria (LAB). These types of biosurfactants are classified based on their structures as protein-carbohydrate complexes, lipids, or fatty acids. The present paper seeks to provide comprehensive and useful information about the production of various kinds of biosurfactants by different probiotic bacteria. In addition, we have extensively reviewed their potential for possible future applications.

Probiotic Cell-Free Supernatants Exhibited Anti-Inflammatory and Antioxidant Activity on Human Gut Epithelial Cells and Macrophages Stimulated with LPS

The incidence of inflammatory bowel disease is increasing all over the world, especially in industrialized countries. The aim of the present work was to verify the anti-inflammatory activity of metabolites. In particular, cell-free supernatants of Lactobacillus acidophilus, Lactobacillus casei, Lactococcus lactis, Lactobacillus reuteri, and Saccharomyces boulardii have been investigated. Metabolites produced by these probiotics were able to downregulate the expression of PGE-2 and IL-8 in human colon epithelial HT-29 cells. Moreover, probiotic supernatants can differently modulate IL-1β, IL-6, TNF-α, and IL-10 production by human macrophages, suggesting a peculiar anti-inflammatory activity. Furthermore, supernatants showed a significant dose-dependent radical scavenging activity. This study suggests one of the mechanisms by which probiotics exert their anti-inflammatory activity affecting directly the intestinal epithelial cells and the underlying macrophages. This study provides a further evidence to support the possible use of probiotic metabolites in preventing and downregulating intestinal inflammation as adjuvant in anti-inflammatory therapy.

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.

Daily intake of fermented milk with Lactobacillus casei strain Shirota reduces the incidence and duration of upper respiratory tract infections in healthy middle-aged office workers

PURPOSE

Although several studies have demonstrated the efficacy of probiotics for preventing upper respiratory tract infections (URTIs) in at-risk populations, including children and the elderly, few studies have investigated the efficacy of probiotics in healthy adults living normal, everyday lives. Thus, we tried to evaluate the effects of Lactobacillus casei strain Shirota-fermented milk (LcS-FM) on the incidence of URTIs in healthy middle-aged office workers.

METHODS

In a randomized controlled trial, 96 eligible male workers aged 30-49 years consumed LcS-FM containing 1.0 × 1011 viable LcS cells or control milk (CM) once daily for 12 weeks during the winter season. URTI episodes were evaluated by a physician via a questionnaire of URTI symptoms.

RESULTS

The incidence of URTIs during the intervention period was significantly lower in the LcS-FM group than in the CM group (22.4 vs. 53.2 %, P = 0.002). The time-to-event analysis showed that the LcS-FM group had a significantly higher URTI-free rate than the CM group over the test period (log-rank test: χ 2 11.25, P = 0.0008). The cumulative number of URTI episodes and cumulative days with URTI symptoms per person was lower in the LcS-FM group, and the duration per episode was shorter. Inhibition of both reductions in NK cell activity in peripheral blood mononuclear cells and increases in salivary cortisol levels was observed in the LcS-FM group.

CONCLUSION

The results suggest that the daily intake of fermented milk with LcS may reduce the risk of URTIs in healthy middle-aged office workers, probably through modulation of the immune system.

Visualization of Probiotic-Mediated Ca2+ Signaling in Intestinal Epithelial Cells In Vivo

Probiotics, such as lactic acid bacteria (LAB) and Bacillus subtilis var. natto, have been shown to modulate immune responses. It is important to understand how probiotic bacteria impact intestinal epithelial cells (IECs), because IECs are the first line of defense at the mucosal surface barrier and their activities substantially affect the gut microenvironment and immunity. However, to date, their precise mechanism remains unknown due to a lack of analytical systems available for live animal models. Recently, we generated a conditional Ca²⁺ biosensor Yellow Cameleon (YC3.60) transgenic mouse line and established 5D (x, y, z, time, and Ca²⁺) intravital imaging systems of lymphoid tissues including those in Peyer’s patches and bone marrow. In the present study, we further advance our intravital imaging system for intestinal tracts to visualize IEC responses against orally administrated food compounds in real time. Using this system, heat-killed B. subtilis natto, a probiotic TTCC012 strain, is shown to directly induce Ca²⁺ signaling in IECs in mice housed under specific pathogen-free conditions. In contrast, this activation is not observed in the Lactococcus lactis strain C60; however, when we generate germ-free YC3.60 mice and observe the LAB stimulation of IECs in the absence of gut microbiota, C60 is capable of inducing Ca²⁺ signaling. This is the first study to successfully visualize the direct effect of probiotics on IECs in live animals. These data strongly suggest that probiotic strains stimulate IECs under physiological conditions and that their activity is affected by the microenvironment of the small intestine, such as commensal bacteria.

Taxa of the Nasal Microbiome Are Associated with Influenza-Specific IgA Response to Live Attenuated Influenza Vaccine

Live attenuated influenza vaccine (LAIV) has demonstrated varying levels of efficacy against seasonal influenza; however, LAIV may be used as a tool to measure interactions between the human microbiome and a live, replicating virus. To increase our knowledge of this interaction, we measured changes to the nasal microbiome in subjects who received LAIV to determine if associations between influenza-specific IgA production and the nasal microbiome exist after immunization with a live virus vaccine. The anterior nares of 47 healthy subjects were swabbed pre- (Day 0) and post- (Days 7 and 28) LAIV administration, and nasal washes were conducted on Days 0 and 28. We performed next-generation sequencing on amplified 16s rRNA genes and measured mucosal influenza-specific IgA titers via enzyme-linked immunosorbent assay (ELISA). A significant increase in alpha diversity was identified (Observed, CHAO, and ACE) between Days 7 vs 0 (p-values = 0.017, 0.005, 0.005, respectively) and between Days 28 vs 0 (p-values = 0.054, 0.030, 0.050, respectively). Several significant associations between the presence of different microbial species, including Lactobacillus helveticus, Prevotella melaninogenica, Streptococcus infantis, Veillonella dispar, and Bacteroides ovatus, and influenza-specific H1 and H3 IgA antibody response were demonstrated. These data suggest that LAIV alters the nasal microbiome, allowing several less-abundant OTUs to establish a community niche. Additionally, specific alterations in the nasal microbiome are significantly associated with variations in influenza-specific IgA antibody production and could be clinically relevant.

Immune responses and stress resistance in red sea bream, Pagrus major, after oral administration of heat-killed Lactobacillus plantarum and vitamin C

The present study evaluated the interactive benefits of dietary administration of heat-killed Lactobacillus plantarum (LP) and vitamin C (VC) on the growth, oxidative status and immune response of red sea bream (Pagrus major). A diet without LP and VC supplements was employed as a control diet. Four other test diets with 0 or 1 g LP kg(-1) combined with 0.5 or 1 g VC kg(-1) (2 × 2 factorial design) were fed to red sea bream (2 ± 0.01 g) for 56 days. A significant interaction was found between LP and VC on final body weight (FNW), weight gain (WG), hematocrit (HCT), serum bactericidal (BA) and lysozyme (LZY) activities, mucus LZY and peroxidase (PA) activities, nitro blue tetrazolium (NBT), catalase, mucus secretion and tolerance against low salinity stress test (LT50) (P < 0.05). In addition, FNW, WG, specific growth rate, feed and protein efficiency ratio, serum (BA, LZY, PA and NBT), mucus (LZY and PA), superoxide dismutase, malondialdehyde and mucus secretion were significantly affected by either LP or VC (P < 0.05). Furthermore, only LP was a significant factor on survival, plasma total cholesterol, mucus BA and alternative complement pathway (P < 0.05). However, VC supplementation affected on HCT and LT50. Interestingly, fish fed with both LP at 1 g kg(-1) diet with VC at 0.5 or 1 g kg(-1) diet showed higher growth, humoral and mucosal immune responses, anti-oxidative status, mucus secretion and LT50 as well as decreased plasma, triglyceride and total cholesterol levels than the fish fed control diet (P < 0.05). These results demonstrated that dietary LP and VC had a significant interaction for red sea bream with the capability of improving growth performance and enhancing stress resistance by immunomodulation.

Effects of dietary supplementation of Lactobacillus rhamnosus or/and Lactococcus lactis on the growth, gut microbiota and immune responses of red sea bream, Pagrus major

Pagrus major fingerlings (3·29 ± 0·02 g) were fed with basal diet (control) supplemented with Lactobacillus rhamnosus (LR), Lactococcus lactis (LL), and L. rhamnosus + L. lactis (LR + LL) at 10(6) cell g(-1) feed for 56 days. Feeding a mixture of LR and LL significantly increased feed utilization (FER and PER), intestine lactic acid bacteria (LAB) count, plasma total protein, alternative complement pathway (ACP), peroxidase, and mucus secretion compared with the other groups (P < 0.05). Serum lysozyme activity (LZY) significantly increased in LR + LL when compared with the control group. Additionally, fish fed the LR + LL diet showed a higher growth performance (Fn wt, WG, and SGR) and protein digestibility than the groups fed an individual LR or the control diet. Superoxide dismutase (SOD) significantly increased in LR and LR + LL groups when compared with the other groups. Moreover, the fish fed LR or LL had better improvement (P < 0.05) in growth, feed utilization, body protein and lipid contents, digestibility coefficients (dry matter, protein, and lipid), protease activity, total intestine and LAB counts, hematocrit, total plasma protein, biological antioxidant potential, ACP, serum and mucus LZY and bactericidal activities, peroxidase, SOD, and mucus secretion than the control group. Interestingly, fish fed diets with LR + LL showed significantly lower total cholesterol and triglycerides when compared with the other groups (P < 0.05). These data strongly suggest that a mixture of LR and LL probiotics may serve as a healthy immunostimulating feed additive in red sea bream aquaculture.

Efficacy of Lactobacillus casei Shirota for patients with irritable bowel syndrome

BACKGROUND AND AIMS

Meta-analyses point to a modest but significant effect of probiotics on symptoms in irritable bowel syndrome (IBS). We aimed to assess the effect of the probiotic Lactobacillus casei Shirota (LcS) on symptoms and quality of life in IBS patients in a randomized, double-blind, placebo-controlled intervention study.

MATERIALS AND METHODS

IBS patients (Rome II) between 18 and 65 years of age were included. The study consisted of an 8-week intervention period in which the participants received probiotic (LcS) or placebo twice daily, followed by an 8-week follow-up period. Symptom diaries and quality of life were scored at weeks 0, 8 and 16. The primary outcome parameter was a decrease of at least 30% in a composite mean symptom score (MSS) at week 8 on the basis of an intention-to-treat analysis.

RESULTS

Thirty-nine individuals (67% women) were included in the probiotic group and 41 individuals (71% women) were included in the placebo group. After the intervention period, the mean relative improvement did not reach 30% for MSS or any individual symptom score. After follow-up (week 16), a mean improvement of at least 30% was achieved for MSS in the probiotic group, but no significant difference was found between both treatment groups (mean±SD: 34±7%; 13±8%, P=0.06).

CONCLUSION

After probiotic treatment with LcS, no improvement of 30% in MSS was observed after 8 weeks.

Interaction effects of dietary supplementation of heat-killed Lactobacillus plantarum and β-glucan on growth performance, digestibility and immune response of juvenile red sea bream, Pagrus major

Both heat-killed Lactobacillus plantarum (HK-LP) and β-glucan (BG) play important roles in growth performance, feed utilization and health status of fish. Therefore, a feeding trial was conducted to determine the interactive effects of dietary HK-LP and BG on growth performance, digestibility, oxidative status and immune response of red sea bream for 56 days. A significant interaction was found between HK-LP and BG on final body weight, total plasma protein, glucose, serum bactericidal activity (BA), total serum protein, serum alternative complement pathway (ACP) activity, protein and dry matter digestibility coefficients (P < 0.05). In addition, body weight gain, specific growth rate, feed intake, protein efficiency ratio as well as serum lysozyme activity, ACP activity and mucus secretion were significantly affected by either HK-LP or BG (P < 0.05). Further, feeding 0.025% HK-LP combined with 0.1% BG significantly increased serum peroxidase activity compared with the other groups (P < 0.05). However, protein body content, somatic parameters, total bilirubin, blood urea nitrogen, glutamyl oxaloacetic transaminase (GOT), glutamic-pyruvate transaminase (GPT), triglycerides and mucus BA were not significantly altered by supplementations (P > 0.05). Interestingly, fish fed with both HK-LP at (0.025 and 0.1%) in combination with BG at (0 and 0.1%) showed higher oxidative stress resistance. Under the experimental conditions, dietary HK-LP and BG had a significant interaction on enhancing the growth, digestibility and immune responses of red sea bream.

Divergent signaling pathways regulate IL-12 production induced by different species of Lactobacilli in human dendritic cells

Recent studies have indicated that different strains of Lactobacilli differ in their ability to regulate IL-12 production by dendritic cells (DCs), as some strains are stronger inducer of IL-12 while other are not and can even inhibit IL-12 production stimulated by IL-12-inducer Lactobacilli. In this report we demonstrate that Lactobacillus reuteri 5289, as previously described for other strains of L. reuteri, can inhibit DC production of IL-12 induced by Lactobacilllus acidophilus NCFM. Remarkably, L. reuteri 5289 was able to inhibit IL-12 production induced not only by Lactobacilli, as so far reported, but also by bacteria of different genera, including pathogens. We investigated in human DCs the signal transduction pathways involved in the inhibition of IL-12 production induced by L. reuteri 5289, showing that this potential anti-inflammatory activity, which is also accompanied by an elevated IL-10 production, is associated to a prolonged phosphorilation of ERK1/2 MAP kinase pathway. Improved understanding of the immune regulatory mechanisms exerted by Lactobacilli is crucial for a more precise employment of these commensal bacteria as probiotics in human immune-mediated pathologies, such as allergies or inflammatory bowel diseases.

Impact of kefir derived Lactobacillus kefiri on the mucosal immune response and gut microbiota

The evaluation of the impact of probiotics on host health could help to understand how they can be used in the prevention of diseases. On the basis of our previous studies and in vitro assays on PBMC and Caco-2 ccl20:luc reporter system presented in this work, the strain Lactobacillus kefiri CIDCA 8348 was selected and administrated to healthy Swiss mice daily for 21 days. The probiotic treatment increased IgA in feces and reduced expression of proinflammatory mediators in Peyer Patches and mesenteric lymph nodes, where it also increased IL-10. In ileum IL-10, CXCL-1 and mucin 6 genes were upregulated; meanwhile in colon mucin 4 was induced whereas IFN-γ, GM-CSF, and IL-1β genes were downregulated. Moreover, ileum and colon explants showed the anti-inflammatory effect of L. kefiri since the LPS-induced increment of IL-6 and GM-CSF levels in control mice was significantly attenuated in L. kefiri treated mice. Regarding fecal microbiota, DGGE profiles allowed differentiation of experimental groups in two separated clusters. Quantitative PCR analysis of different bacterial groups revealed only significant changes in Lactobacillus population. In conclusion, L. kefiri is a good candidate to be used in gut inflammatory disorders.

Role of Lactobacillus pentosus Strain b240 and the Toll-like receptor 2 axis in Peyer's patch dendritic cell-mediated immunoglobulin A enhancement

Lactic acid bacteria are well known to possess immune-modulating effects, but the mechanisms underlying their modulation of the gut immune system are not fully understood. Here, we examined the localization of heat-killed Lactobacillus pentosus strain b240 (b240) in intestinal tissues and the effect of b240 on adaptive immune cascades in the gut. Histological analysis showed that b240 co-localized with dendritic cells (DCs) in the subepithelial dome region of Peyer's patches (PPs). In a PP cell culture system, b240 promoted the production of immunoglobulin A (IgA), interleukin (IL)-6, IL-10, interferon (IFN)-γ, and tumor necrosis factor, but not IL-4, IL-5, B-cell activating factors, IFN-α, IFN-β, and transforming growth factor-β1. The enhanced IgA production by b240 was attenuated by neutralizing IL-6, a potent IgA-enhancing cytokine. b240 stimulated DCs to produce an elevated amount of IL-6 in a Toll-like receptor (TLR) 2-, but not TLR4- or TLR9-dependent manner. Finally, we demonstrated that TLR2-mediated IL-6 production from PP DCs in response to b240 activated B cells to produce a large amount of IgA in a DC-B cell co-culture system. Our findings open up the possibility that the heat-killed form of Lactobacillus pentosus strain b240 can be used as a TLR2-mediated DC-activating biologic for enhancing IgA production in the intestine.

Transposon mutagenesis of probiotic Lactobacillus casei identifies asnH, an asparagine synthetase gene involved in its immune-activating capacity

Lactobacillus casei ATCC 27139 enhances host innate immunity, and the J1 phage-resistant mutants of this strain lose the activity. A transposon insertion mutant library of L. casei ATCC 27139 was constructed, and nine J1 phage-resistant mutants out of them were obtained. Cloning and sequencing analyses identified three independent genes that were disrupted by insertion of the transposon element: asnH, encoding asparagine synthetase, and dnaJ and dnaK, encoding the molecular chaperones DnaJ and DnaK, respectively. Using an in vivo mouse model of Listeria infection, only asnH mutant showed deficiency in their ability to enhance host innate immunity, and complementation of the mutation by introduction of the wild-type asnH in the mutant strain recovered the immuno-augmenting activity. AsnH protein exhibited asparagine synthetase activity when the lysozyme-treated cell wall extracts of L. casei ATCC 27139 was added as substrate. The asnH mutants lost the thick and rigid peptidoglycan features that are characteristic to the wild-type cells, indicating that AsnH of L. casei is involved in peptidoglycan biosynthesis. These results indicate that asnH is required for the construction of the peptidoglycan composition involved in the immune-activating capacity of L. casei ATCC 27139.

Ageing, immunity and influenza: a role for probiotics?

Influenza is a major cause of death in the over 65s. Increased susceptibility to infection and reduced response to vaccination are due to immunosenscence in combination with medical history and lifestyle factors. Age-related alterations in the composition of the gut microbiota have a direct impact on the immune system and it is proposed that modulation of the gut microbiota using pre- and probiotics could offer an opportunity to improve immune responses to infections and vaccination in older people. There is growing evidence that probiotics have immunomodulatory properties, which to some extent are strain-dependent, and are strongly influenced by ageing. Randomised controlled trials suggest that probiotics may reduce the incidence and/or severity of respiratory infections, although there is limited data on older people. A small number of studies have examined the potential adjuvant effects of selected probiotics for vaccination against influenza; however, the data is inconsistent, particularly in older people. This review describes the impact of age-related changes in the gut on the immune response to respiratory infections and evaluates whether restoration of gut microbial homoeostasis by probiotics offers an opportunity to modulate the outcome of respiratory infections and vaccination against influenza in older people. Although there is promising evidence for effects of probiotics on human health, there is a lack of consistent data, perhaps partly due to strain-specific differences and an influence of the age of the host. Further research is critical in evaluating the potential use of probiotics in respiratory infections and vaccination in the ageing population.

A potential role of probiotics in colorectal cancer prevention: review of possible mechanisms of action

A number of investigations, mainly using in vitro and animal models, have demonstrated a wide range of possible mechanisms, by which probiotics may play a role in colorectal cancer (CRC) prevention. In this context, the most well studied probiotics are certain strains from the genera of lactobacilli and bifidobacteria. The reported anti-CRC mechanisms of probiotics encompass intraluminal, systemic, and direct effects on intestinal mucosa. Intraluminal effects detailed in this review include competitive exclusion of pathogenic intestinal flora, alteration of intestinal microflora enzyme activity, reduction of carcinogenic secondary bile acids, binding of carcinogens and mutagens, and increasing short chain fatty acids production. Reduction of DNA damage and suppression of aberrant crypt foci formation have been well demonstrated as direct anti-CRC effects of probiotics on intestinal mucosa. Existing evidence clearly support a multifaceted immunomodulatory role of probiotics in CRC, particularly its ability to modulate intestinal inflammation, a well known risk factor for CRC. The effectiveness of probiotics in CRC prevention is dependent on the strain of the microorganism, while viability may not be a prerequisite for certain probiotic anticancer mechanisms, as indicated by several studies. Emerging data suggest synbiotic as a more effective approach than either prebiotics or probiotics alone. More in vivo especially human studies are warranted to further elucidate and confirm the potential role of probiotics (viable and non-viable), prebiotics and synbiotics in CRC chemoprevention.

Oral supplementation with Lactobacillus delbrueckii subsp. bulgaricus 8481 enhances systemic immunity in elderly subjects

Throughout life, there is an aging of the immune system that causes impairment of its defense capability. Prevention or delay of this deterioration is considered crucial to maintain general health and increase longevity. We evaluated whether dietary supplementation with Lactobacillus delbrueckii subsp. bulgaricus 8481 could enhance the immune response in the elderly. This multi-center, double-blind, and placebo controlled study enrolled 61 elderly volunteers who were randomly assigned to receive either placebo or probiotics. Each capsule of probiotics contained at least 3 × 10(7)  L. delbrueckii subsp. bulgaricus 8481. Individuals in the study were administered three capsules per day for 6 months. Blood samples were obtained at baseline (time 0), end of month 3, and month 6. We characterized cell subpopulations, measured cytokines by flow cytometry, quantified T cell receptor excision circle (TREC) by real-time PCR (RT-PCR), and determined human β-defensin-2 (hBD-2) concentrations and human cytomegalovirus (CMV) titers by enzyme-linked immunosorbent assay (ELISA). Elderly responded to the intake of probiotic with an increase in the percentage of NK cells, an improvement in the parameters defining the immune risk profile (IRP), and an increase in the T cell subsets that are less differentiated. The probiotic group also showed decreased concentrations of the pro-inflammatory cytokine IL-8 but increased antimicrobial peptide hBD-2. These effects disappeared within 6 months of stopping the probiotic intake. Immunomodulation induced by L. delbrueckii subsp. bulgaricus 8481 could favor the maintenance of an adequate immune response, mainly by slowing the aging of the T cell subpopulations and increasing the number of immature T cells which are potential responders to new antigens.

Can enterocins affect phagocytosis and glutathione-peroxidase in rabbits?

The gastrointestinal microbiota in rabbits play an important role in protection against potential pathogens via the development of the mucosal immune system. The gut health, including the microbial and immunological stability, is often influenced by exogenous factors, mainly around the weaning period. Therefore, alternative strategies are required to improve the animal’s health. In this study, the diet of rabbits was supplemented with the semi-purified enterocins Ent 2019, Ent M and Ent 4231, produced by bacteriocinogenic strains with probiotic properties, rabbit-derived Enterococcus faecium CCM7420 and non rabbit-derived E. faecium strains AL41 and CCM4231. The phagocytic activity, index of phagocytic activity and the gluthatione-peroxidase enzyme activity in blood were determined during the Ents consumption and also 3 weeks after their cessation. At 21 days into the experiment the highest phagocytic activity was observed in rabbits receiving Ent M. A significant increase in phagocytosis was noted in rabbits with Ent 2019 over the entire experiment. Moreover, a lower gluthatione-peroxidase activity was measured in rabbits receiving Ent M and Ent 2019. No effect of Ent 4231 application on the tested parameters was recorded. The Ent M and Ent 2019 improved the digestive immunity and the host’s defense capacities by stimulating leucocyte phagocytosis, without oxidative stress induction in rabbits.

Probiotics can generate FoxP3 T-cell responses in the small intestine and simultaneously inducing CD4 and CD8 T cell activation in the large intestine

Most studies on probiotics aim to restore intestinal homeostasis to reduce immune-pathology in disease. Of equal importance are studies on how probiotics might prevent or delay disease in healthy individuals. However, knowledge on mechanisms of probiotic actions in healthy individuals is scarce. To gain more insight in how different bacterial strains may modulate the healthy intestinal immune system, we investigated the effect of the food derived bacterial strains L. plantarum WCFS1, L. salivarius UCC118, and L. lactis MG1363, on the intestinal regulatory immune phenotype in healthy mice. All three bacterial strains induced an upregulation of activity and numbers of CD11c⁺ MHCII⁺ DCs in the immune-sampling Peyer’s Patches. Only L. salivarius UCC118 skewed towards an immune regulatory phenotype in the small intestinal lamina propria (SILP). The effects were different in the large intestine lamina propria. L. salivarius UCC118 induced activation in both CD4 and CD8 positive T-cells while L. plantarum WCFS1 induced a more regulatory phenotype. Moreover, L. plantarum WCFS1 decreased the Th1/Th2 ratio in the SILP. Also L. lactis MG1363 had immunomodulatory effects. L. lactis MG1363 decreased the expression of the GATA-3 and T-bet in the SILP. As our data show that contradictory effects may occur in different parts of the gut, it is recommended to study effects of probiotic in different sites in the intestine. Our strain-specific results suggest that unspecified application of probiotics may not be very effective. Our data also indicate that selection of specific probiotic strain activities on the basis of responses in healthy mice may be a promising strategy to specifically stimulate or suppress immunity in specific parts of the intestine.

Double-stranded RNA of intestinal commensal but not pathogenic bacteria triggers production of protective interferon-β

The small intestine harbors a substantial number of commensal bacteria and is sporadically invaded by pathogens, but the response to these microorganisms is fundamentally different. We identified a discriminatory sensor by using Toll-like receptor 3 (TLR3). Double-stranded RNA (dsRNA) of one major commensal species, lactic acid bacteria (LAB), triggered interferon-β (IFN-β) production, which protected mice from experimental colitis. The LAB-induced IFN-β response was diminished by dsRNA digestion and treatment with endosomal inhibitors. Pathogenic bacteria contained less dsRNA and induced much less IFN-β than LAB, and dsRNA was not involved in pathogen-induced IFN-β induction. These results identify TLR3 as a sensor to small intestinal commensal bacteria and suggest that dsRNA in commensal bacteria contributes to anti-inflammatory and protective immune responses.

Mucosal immunology and probiotics

The cross-talk between the mucosa-associated immune system and microbiota is critical in mucosal tissue homeostasis as well as in protection against infectious and inflammatory diseases occurring at mucosal sites. This recent evidence has paved the way to therapeutic approaches aimed at modulating the mucosa-associated immune system using probiotics. Different strains of probiotics possess the ability to finely regulate dendritic cell (DC) activation, polarizing the subsequent T cell activity toward Th1 (e.g. Lactobacillus (Lb) acidophilus), Th2 (Lb.reuteri and Bifidobacterium bifidum) or, as more recently demonstrated, Th17 responses induced by specific strains such as Lb.rhamnosus GG and Lac23a, the latter isolated in our laboratory. Here, we review some recent advances in our understanding of probiotics effects on mucosal immunology, particularly on cells of the innate immunity such as DCs. We also highlight our own experiences in modulating DC functions by commensal bacteria and discuss the relevance of probiotics administration in the treatment of human immunopathologies.

Gut microbiota, host health, and polysaccharides

The intestinal microbiota is a complicated ecosystem that influences many aspects of host physiology (i.e. diet, disease development, drug metabolism, and regulation of the immune system). It also exhibits spatial patterning and temporal dynamics. In this review, the effects of internal and external (environmental) factors on intestinal microbiota are discussed. We describe the roles of the gut microbiota in maintaining intestinal and immune system homeostasis and the relationship between gut microbiota and diseases. In particular, the contributions of polysaccharides, as the most abundant diet components in intestinal microbiota and host health are presented. Finally, perspectives for research avenues relating to gut microbiota are also discussed.

Probiotic Bifidobacterium breve induces IL-10-producing Tr1 cells in the colon

Specific intestinal microbiota has been shown to induce Foxp3(+) regulatory T cell development. However, it remains unclear how development of another regulatory T cell subset, Tr1 cells, is regulated in the intestine. Here, we analyzed the role of two probiotic strains of intestinal bacteria, Lactobacillus casei and Bifidobacterium breve in T cell development in the intestine. B. breve, but not L. casei, induced development of IL-10-producing Tr1 cells that express cMaf, IL-21, and Ahr in the large intestine. Intestinal CD103(+) dendritic cells (DCs) mediated B. breve-induced development of IL-10-producing T cells. CD103(+) DCs from Il10(-/-), Tlr2(-/-), and Myd88(-/-) mice showed defective B. breve-induced Tr1 cell development. B. breve-treated CD103(+) DCs failed to induce IL-10 production from co-cultured Il27ra(-/-) T cells. B. breve treatment of Tlr2(-/-) mice did not increase IL-10-producing T cells in the colonic lamina propria. Thus, B. breve activates intestinal CD103(+) DCs to produce IL-10 and IL-27 via the TLR2/MyD88 pathway thereby inducing IL-10-producing Tr1 cells in the large intestine. Oral B. breve administration ameliorated colitis in immunocompromised mice given naïve CD4(+) T cells from wild-type mice, but not Il10(-/-) mice. These findings demonstrate that B. breve prevents intestinal inflammation through the induction of intestinal IL-10-producing Tr1 cells.

Health impact of probiotics - vision and opportunities

Our understanding of the role of the microbiota in our gut and other sites in our body is rapidly emerging and could lead to many new and innovative approaches for health care. The promise of the potential role of probiotics for the prevention and treatment of enteric and other infections as an effective solution needs to be realized. The meeting report summarizes the insights and learning from a recent symposium, "Health Impact of Probiotics - Vision and Opportunities" conducted in Mumbai by the Yakult India Microbiota and Probiotic Science Foundation and P.D. Hinduja National Hospital, Mumbai. The symposium reflected its objective of unraveling the potential role of probiotics for health benefits through presentations and discussions. Experts clearly highlighted the role of probiotics in improving various aspects of health and in immune modulation. The report also captures the debate and discussions on the challenges that are likely to be encountered for the use of probiotics in the country.

Identification of Immunopotentiating Lactic Acid Bacteria that Induce Antibody Production by in vitro Stimulated Human Peripheral Blood Mononuclear Cells

L-leucyl-L-leucine methyl ester (LLME) is known to remove lysosome-rich cells from human peripheral blood mononuclear cells (PBMCs). To evaluate the immunopotentiating ability of lactic acid bacteria (LAB), we adopted the in vitro stimulation protocol of LLME-treated PBMCs as a model assay system and monitored the level of antibody produced by stimulated PBMCs. The results indicated that several LAB strains have immunopotentiating ability against PBMCs, as evidenced by the enhanced antibody production and increased number of antigen-specific B cells. Next, we identified T cells as the direct target cells of the immunopotentiating LAB strain L32, suggesting that L32 induced antibody production by PBMCs through T-cell activation. Finally, we tested the immunopotentiating ability of ligands for Toll-like receptor 2 (TLR2), which is known to mediate the LAB signal, and observed that both L32 and one of the TLR2 ligands, LTA-BS, induced antigen-specific antibody production by in vitro stimulated PBMC. This suggests that L32 and LTA-BS can be used as an adjuvant for stimulating immune reaction in PBMCs.

Probiotic lactic acid bacteria in the gastro-intestinal tract: health benefits, safety and mode of action

Lactic acid bacteria (LAB) have received considerable attention as probiotics over the past few years. This concept has grown from traditional dairy products to a profitable market of probiotic health supplements and functional foods. Extensive research is done on novel potential probiotic strains, with specific emphasis on their health benefits and mode of action. Criteria for the selection of probiotic strains have only recently been formulated by the Food and Agriculture Organization of the United Nations and the World Health Organization (FAO/WHO). Several in vitro techniques have been developed to evaluate the probiotic properties of strains. In many cases, this is followed by in vivo tests. Safety studies are also obligatory, as a few cases of bacteremia caused by LAB have been reported. This review focuses on the health benefits and safety of LAB probiotics, the criteria used to select a probiotic, mode of action and the impact these organisms have on natural microbiota in the gastro-intestinal tract.

Probiotic upregulation of peripheral IL-17 responses does not exacerbate neurological symptoms in experimental autoimmune encephalomyelitis mouse models

CONTEXT

It is of great importance to evaluate the safety of probiotics in dysregulated immune conditions, as probiotics can possibly modulate immune functions in the host.

OBJECTIVE

We tried to confirm the safety of using Lactobacillus casei strain Shirota (LcS) to help prevent autoimmunity in the central nervous system.

METHODS

We used two chronic experimental autoimmune encephalomyelitis (EAE) models, a relapse and remission type EAE model in SJL/J mice and a durable type model in C57BL/6 mice. LcS was administered from 1 week before antigen sensitization until the end of the experiments, and neurological symptoms and histopathological changes of the spinal cord were observed. Immunological parameters were also examined in the SJL/J mouse model.

RESULTS

LcS administration did not exacerbate neurological symptoms or histopathological changes of the spinal cord in either model but instead tended to improve neurological symptoms in the SJL/J mouse EAE model. LcS administration transiently upregulated IL-17 production by antigen-stimulated lymphocytes of draining lymph nodes 7 days after sensitization. Enhanced production of IL-10 and an increase in the percentage of CD4(+)CD25(+) T regulatory cells were also observed at the same sites. Strong expression of IL-17 mRNA was detected in the spinal cord of mice that displayed severe neurological symptoms on day 12, but this expression was not enhanced by LcS administration.

CONCLUSION

These results demonstrate that LcS does not exacerbate, but instead may improve EAE depending on the immunization conditions, and that IL-17 responses at peripheral sites may not always result in a worsening of autoimmune diseases.

Protective effect of probiotics on intestinal barrier function in malnourished rats after liver transplantation

BACKGROUND

Most patients waiting for liver transplantation have end-stage liver diseases with malnutrition, which is prone to induce intestinal barrier dysfunction after liver transplantation. We aimed to study the effect of probiotics on intestinal barrier function in malnourished rats following liver transplantation with long-term antibiotics.

METHODS

Twelve Lewis rats were selected as donors. Twelve BN rats, which served as recipients, were subjected to malnutrition by semi-starvation for 4-5 weeks. They were randomly divided into two groups: a control group which received phosphate-buffered saline and a probiotics group which received Bifidobacterium and Lactobacillus. All recipients were injected with intramuscular imipenem and subcutaneous cyclosporine A. Furthermore, six normal BN rats without any drugs or operations served as a normal group. Eight days after operation, all rats were sacrificed for examination of the following parameters: serum levels of endotoxin and TNF-alpha, bacterial translocation, intestinal microflora, ileocecal sIgA, lymphocyte numbers, and phenotypes (CD4, CD8, alphabetaTCR, gammadeltaTCR) of Peyer's patches.

RESULTS

In recipients subjected to malnutrition, weight decreased by 20% and they survived until 8 days after operation. Compared with the normal group, all recipients on postoperative day 8 showed increased levels of serum endotoxin and TNF-alpha as well as increased counts of translocated bacteria. Meanwhile, there were decreases in counts of Bifidobacterium and Lactobacillus in the ileocecum, sIgA concentration, and lymphocytes of Peyer's patches. Moreover, partial alteration in lymphocyte phenotypes was evidenced by elevated ratios of CD8+ and gammadeltaTCR+ lymphocytes. In contrast, compared to the control group, supplementation with probiotics reduced the levels of serum endotoxin, TNF-alpha and bacterial translocation, increased the counts of Bifidobacterium and Lactobacillus, the concentration of sIgA and lymphocytes of Peyer's patches, and also slightly restored the alteration of lymphocyte phenotypes.

CONCLUSION

Supplementation with probiotics including Bifidobac-terium and Lactobacillus promoted partial restoration of intestinal microflora and improved intestinal barrier function in malnourished rats after liver transplantation with long-term use of antibiotics.