Lactobacillus and Lactobacillus cell-free culture supernatants modulate chicken macrophage activities

Lactobacillus salivarius ameliorates Mycoplasma gallisepticum-induced inflammation via the JAK/STAT signaling pathway involving respiratory microbiota and metabolites

Mycoplasma gallisepticum (MG) can cause chronic respiratory disease (CRD) in chickens, which has a significant negative economic impact on the global poultry sector. Respiratory flora is the guardian of respiratory health, and its disorder is closely related to respiratory immunity and respiratory diseases. As a common probiotic in the chicken respiratory tract, Lactobacillus salivarius (L. salivarius) has potential antioxidant, growth performance enhancing, and anti-immunosuppressive properties. However, the specific mechanism through which L. salivarius protects against MG infection has not yet been thoroughly examined. This study intends to investigate whether L. salivarius could reduce MG-induced tracheal inflammation by modulating the respiratory microbiota and metabolites. The results indicated that L. salivarius reduced MG colonization significantly and alleviated the anomalous morphological changes by using the MG-infection model. L. salivarius also reduced the level of Th1 cell cytokines, increased the level of Th2 cell cytokines, and ameliorated immune imbalance during MG infection. In addition, L. salivarius improved the mucosal barrier, heightened immune function, and suppressed the Janus kinase/Signal transducer, and activator of transcription (JAK/STAT) signaling pathway. Notably, MG infection changed the composition of the respiratory microbiota and metabolites, and L. salivarius therapy partially reversed the aberrant respiratory microbiota and metabolite composition. Our results highlighted that these findings demonstrated that L. salivarius played a role in MG-mediated inflammatory damage and demonstrated that L. salivarius, by altering the respiratory microbiota and metabolites, could successfully prevent MG-induced inflammatory injury in chicken trachea.

Proof of concept in utilizing the peptidoglycan skeleton of pathogenic bacteria as antigen delivery platform for enhanced immune response

Subunit vaccines are becoming increasingly important because of their safety and effectiveness. However, subunit vaccines often exhibit limited immunogenicity, necessitating the use of suitable adjuvants to elicit robust immune responses. In this study, we demonstrated for the first time that pathogenic bacteria can be prepared into a purified peptidoglycan skeleton without nucleic acids and proteins, presenting bacterium-like particles (pBLP). Our results showed that the peptidoglycan skeletons screened from four pathogens could activate Toll-like receptor1/2 receptors better than bacterium-like particles from Lactococcus lactis in macrophages. We observed that pBLP was safe in mouse models of multiple ages. Furthermore, pBLP improved the performance of two commercial vaccines in vivo. We confirmed that pBLP successfully loaded antigens onto the surface and proved to be an effective antigen delivery platform with enhanced antibody titers, antibody avidity, balanced subclass distribution, and mucosal immunity. These results indicate that the peptidoglycan skeleton of pathogenic bacteria represents a new strategy for developing subunit vaccine delivery systems.

Effect of the polysaccharide capsule and its heptose on the resistance of Campylobacter jejuni to innate immune defenses

Campylobacter jejuni is a commensal in many animals but causes diarrhea in humans. Its polysaccharide capsule contributes to host colonization and virulence in a strain- and model-specific manner. We investigated if the capsule and its heptose are important for interactions of strain NCTC 11168 with various hosts and their innate immune defenses. We determined that they support bacterial survival in Drosophila melanogaster and enhance virulence in Galleria mellonella. We showed that the capsule had limited antiphagocytic activity in human and chicken macrophages, decreased adherence to chicken macrophages, and decreased intracellular survival in both macrophages. In contrast, the heptose increased uptake by chicken macrophages and supported adherence to human macrophages and survival within them. While the capsule triggered nitric oxide production in chicken macrophages, the heptose mitigated this and protected against nitrosative assault. Finally, the C. jejuni strain NCTC 11168 elicited strong cytokine production in both macrophages but quenched ROS production independently from capsule and heptose, and while the capsule and heptose did not protect against oxidative assault, they favored growth in biofilms under oxidative stress. This study shows that the wild-type capsule with its heptose is optimized to resist innate defenses in strain NCTC 11168 often via antagonistic effects of the capsule and its heptose.

Effect of Lactobacillus salivarius SNK-6 on egg quality, intestinal morphology, and cecal microbial community of laying hens

The objective of this study was to investigate the effect of Lactobacillus salivarius (L. salivarius) SNK-6 supple-mentation on the laying performance, egg quality, blood parameters, intestinal morphology, and cecal microbial community of laying hens. A total of 432 healthy 30-wk-age laying hens were randomly divided into 3 groups with 6 replicates under the same husbandry and dietary regimes: control (CON); 2.0 × 108 CFU/kg L. salivarius supplementation (T1); 2.0 × 109 CFU/kg L. salivarius supplementation (T2). The experiment lasted for 10 wk. The results indicated that the supplementation resulted in a significant reduction in the broken egg and unqualified egg ratios, and a significant increase in the eggshell strength, eggshell relative weight, albumen height, and Haugh units (P < 0.05). The L. salivarius-treated hens exhibited significantly reduced serum malondialdehyde levels (P < 0.05); significantly increased total protein, phosphorus, calcitonin, and immunoglobulin M (P < 0.05); significantly increased cecal secretory immunoglobulin A concentration (P < 0.05); significantly improved villus height (VH) in the duodenum and VH to crypt depth ratio in the jejunum (P < 0.05). The serum globulin and interleukin-1β, immunoglobulin G concentrations, and catalase activity significantly increased in T2 (P < 0.05). Furthermore, the serum interferon-α level in T1 was significantly higher than that of the CON (P < 0.05). The intestinal barrier-related mRNA gene ZO-1, CLDN1, and MUC2 expression in the jejunum was significantly upregulated in the T1 and T2 groups (P < 0.05). The Firmicutes/Bacteroidetes ratio was higher and the relative abundances of Flavonifractor and Clostridiales_noname were significantly higher in the T1 group (P < 0.05). In conclusion, dietary supplementation with L. salivarius SNK-6 may improve hen egg quality, serum antioxidant capacity, immune function, and intestinal health.

STAT4 Phosphorylation of T-helper Cells predicts surgical outcomes in Refractory Chronic Rhinosinusitis

Objective

Chronic rhinosinusitis (CRS) impacts an estimated 5% to 15% of people worldwide, incurring significant economic healthcare burden. There is a urgent need for the discovery of predictive biomarkers to improve treatment strategies and outcomes for CRS patients.

Study design

Cohort study of CRS patients and healthy controls using blood samples.

Setting

Out-patient clinics.

Methods

Whole blood samples were collected for flow cytometric analysis. Mechanistic studies involved the transfection of human primary T cells and Jurkat cells.

Results

Our analysis began with a 63-69 year-old female patient diagnosed with refractory CRS,. Despite undergoing multiple surgeries, she continually faced sinus infections. Whole exome sequencing pinpointed a heterozygous IL-12Rb1 mutation situated in the linker region adjacent to the cytokine binding domain. When subjected to IL-12 stimulation, the patient's CD4 T-cells exhibited diminished STAT4 phosphorylation. However, computer modeling or T-cell lines harboring the same IL-12 receptor mutation did not corroborate the hypothesis that IL-12Rb could be responsible for the reduced phosphorylation of STAT4 by IL-12 stimulation. Upon expanding our investigation to a broader CRS patient group using the pSTAT4 assay, we discerned a subset of refractory CRS patients with abnormally low STAT4 phosphorylation. The deficiency showed improvement both in-vitro and in-vivo after exposure to Latilactobacillus sakei (aka Lactobacillus sakei), an effect at least partially dependent on IL-12.

Conclusion

In refractory CRS patients, an identified STAT4 defect correlates with poor clinical outcomes after sinus surgery, which can be therapeutically targeted by Latilactobacillus sakei treatment. Prospective double-blind placebo-controlled trials are needed to validate our findings.

Contribution of Lactobacilli on Intestinal Mucosal Barrier and Diseases: Perspectives and Challenges of Lactobacillus casei

The intestine barrier, the front line of normal body defense, relies on its structural integrity, microbial composition and barrier immunity. The intestinal mucosal surface is continuously exposed to a complex and dynamic community of microorganisms. Although it occupies a relatively small proportion of the intestinal microbiota, Lactobacilli has been discovered to have a significant impact on the intestine tract in previous studies. It is undeniable that some Lactobacillus strains present probiotic properties through maintaining the micro-ecological balance via different mechanisms, such as mucosal barrier function and barrier immunity, to prevent infection and even to solve some neurology issues by microbiota-gut-brain/liver/lung axis communication. Notably, not only living cells but also Lactobacillus derivatives (postbiotics: soluble secreted products and para-probiotics: cell structural components) may exert antipathogenic effects and beneficial functions for the gut mucosal barrier. However, substantial research on specific effects, safety and action mechanisms in vivo should be done. In clinical application of humans and animals, there are still doubts about the precise evaluation of Lactobacilli's safety, therapeutic effect, dosage and other aspects. Therefore, we provide an overview of central issues on the impacts of Lactobacillus casei (L. casei) and their products on the intestinal mucosal barrier and some diseases and highlight the urgent need for further studies.

Lactobacillus salivarius SNK-6 Activates Intestinal Mucosal Immune System by Regulating Cecal Microbial Community Structure in Laying Hens

The production performance and disease resistance of laying hens decrease obviously with age. This study aimed to investigate the effects of supplementary Lactobacillus salivarius (L. salivarius) SNK-6 on laying performance, the immune-related gene expression in cecal tonsil, and the cecal microbial composition of laying hens. Here, 384 Xinyang black commercial hens (55 weeks old) were randomly allocated to three groups under the same husbandry and dietary regimes: basal diet (Con), the low L. salivarius SNK-6 group (T1: 1.0 × 106 CFU/g), and the high L. salivarius SNK-6 group (T2: 1.0 × 107 CFU/g). The results showed that the feed intake and broken-egg rate in the T1 group were significantly higher than the Con group (p < 0.05). Meanwhile, expressions of intestinal mucosal immune-related genes were significantly upregulated. The 16S rRNA gene sequencing indicated that supplementary L. salivarius SNK-6 had no significant difference in α -diversity and only displayed a trend difference in the β-diversity of cecal microbiota (p = 0.07). LEfSe and random forest were further used to identify bacteria family Enterobacteriaceae, order RF39, genera Ochrobactrum, and Eubacterium as biomarkers between the Con and T1 groups. Genera Ochrobactrum, which had high relative abundance and nodal degree in the T1 and T2 groups, showed a significant positive correlation with the expression of TLR-6, IL-10, MHC-II, and CD40 in cecal tonsils and might play a critical role in activating the host intestinal mucosal immune responses. Overall, dietary supplementary L. salivarius SNK-6 can display an immunomodulatory function, possibly by regulating cecal microbial composition. However, the changes in immune responses may be at the expenditure of corresponding production performance, which needs to be weighed up in practical application.

Ex Vivo Differential Responsiveness to Clostridium perfringens and Lactococcus lactis by Avian Small Intestine Macrophages and T Cells

Tissue resident immune system cells in the chicken intestine play a significant role in the protection against pathogens. However, very little is known about these cells. The current study was conducted to further characterize chicken intestinal immune system cells. Furthermore, this study aimed to assess the immune modulatory action of a highly virulent Clostridium perfringens, a commonly found chicken intestinal microbe, in comparison with a non-commensal, Lactococcus lactis, on intestine-derived immune system cells. The results demonstrated varying distribution of innate and adaptive immune cells along the avian gut-associated lymphoid tissue (GALT) in the duodenum, jejunum, ileum, and cecal tonsils. In addition, steady-state and tissue-specific presence of CD25+ cells among αβ and γδ T-cell subsets was assessed along the intestine. Ex vivo stimulation with C. perfringens or L. lactis resulted in a significant increase in the frequency of CD25+ T cells (γδ and αβ T cells). In addition, significantly more cell death was observed in ex vivo stimulation with C. perfringens, which was indirectly correlated with a decrease in macrophage activation based on nitric oxide (NO) production with no effect on lymphoid cell responsiveness as per intracellular interferon (IFN)-gamma (γ) staining. Ex vivo stimulation with L. lactis activated γδ T cells and αβ T cells, based on intracellular IFN-γ staining, while it had limited effect on macrophages. However, the ability of γδ and αβ T cells to produce IFN-γ and the ability of macrophages production of NO was rescued in the presence of L. lactis. These results demonstrate the potential application of L. lactis, as a probiotic, against virulent C. perfringens infection in chicken.

Probiotics: an Antibiotic Replacement Strategy for Healthy Broilers and Productive Rearing

Pathogens develop resistance to antibiotics at a rate much faster than the discovery of new antimicrobial compounds. Reports of multidrug-resistant bacteria isolated from broilers, and the possibility that these strains may spread diseases amongst humans, prompted many European countries to ban the inclusion of antibiotics in feed. Probiotics added to broiler feed controlled a number of bacterial infections. A combination of Enterococcus faecium, Pediococcus acidilactici, Bacillus animalis, Lactobacillus salivarius and Lactobacillus reuteri decreased the colonisation of Campylobacter jejuni and Salmonella Enteritidis in the gastro-intestinal tract (GIT) of broilers, whereas Bacillus subtilis improved feed conversion, intestinal morphology, stimulated the immune system and inhibited the colonisation of Campylobacter jejuni, Escherichia coli and Salmonella Minnesota. Lactobacillus salivarius and Pediococcus parvulus improved weight gain, bone characteristics, intestinal morphology and immune response, and decreased the colonisation of S. Enteritidis. Lactobacillus crispatus, L. salivarius, Lactobacillus gallinarum, Lactobacillus johnsonii, Enterococcus faecalis and Bacillus amyloliquefaciens decreased the Salmonella count and led to an increase in lysozyme and T lymphocytes. Probiotics may also improve feed digestion through production of phytases, lipases, amylases and proteases or stimulate the GIT to secrete digestive enzymes. Some strains increase the nutritional value of feed by production of vitamins, exopolysaccharides and antioxidants. Bacteriocins, if produced, regulate pathogen numbers in the GIT and keep pro-inflammatory and anti-inflammatory reactions in balance.

Exopolysaccharides as Antimicrobial Agents: Mechanism and Spectrum of Activity

Exopolysaccharides (EPSs) are metabolites synthesized and excreted by a variety of microorganisms, including lactic acid bacteria (LAB). EPS serve several biological functions such as interactions between bacteria and their environments, protection against hostile conditions including dehydration, the alleviation of the action of toxic compounds (bile salts, hydrolyzing enzymes, lysozyme, gastric, and pancreatic enzymes, metal ions, antibiotics), and stresses (changing pH, osmolarity), and evasion of the immune response and phage attack. Bacterial EPSs are considered valuable by the food, pharmaceutical, and nutraceutical industries, owing to their health-promoting benefits and rheological impacts. Numerous studies have reported the unusual antimicrobial activities of various EPS against a wide variety of pathogenic microbes (bacteria, virus, and fungi). This review aims to provide a comprehensive examination of the in vitro and in vivo antimicrobial activities of different EPSs, mainly against foodborne bacterial, fungal, and viral pathogens. The mechanism of EPS action against these pathogens as well as the methods used to measure antimicrobial activities are critically reviewed.

Lactobacillus rhamnosus GG defense against Salmonella enterica serovar Typhimurium infection through modulation of M1 macrophage polarization

Lactobacillus rhamnosus GG (LGG), a model probiotic strain, plays an important role in immune regulatory activity to prevent and treat intestinal inflammation or diarrhea. However, the effect of the immune modulation of LGG on macrophages to prevent Salmonella infection has not been thoroughly studied. In this study, C57BL/6 mice were pre-administered LGG for 7 days continuously, and then infected with Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium). The results of the in vivo study indicated that LGG could reduce body weight loss, death rate and intestinal inflammatory response caused by S. Typhimurium. LGG also limited S. Typhimurium dissemination to liver and spleen, and thereby protected against infection. In vitro study, we observed that LGG enhanced the phagocytic and bactericidal ability of macrophages and upregulated M1 macrophage characters (e.g. iNOS, NO and IL-12) against S. Typhimurium. In addition, LGG also elevated IL-10 secretion, which was helpful to ameliorate intestinal inflammatory injury caused by S. Typhimurium. In conclusion, LGG could modulate M1 macrophage polarization and offer protective effects against S. Typhimurium infection.

Pretreatment with probiotics ameliorate gut health and necrotic enteritis in broiler chickens, a substitute to antibiotics

Necrotic enteritis (NE) is being considered as one of the most important intestinal diseases in the recent poultry production systems, which causes huge economic losses globally. NE is caused by Clostridium perfringens, a pathogenic bacterium, and normal resident of the intestinal microflora of healthy broiler chickens. Gastrointestinal tract (GIT) of broiler chicken is considered as the most integral part of pathogen's entrance, their production and disease prevention. Interaction between C. perfringens and other pathogens such as Escherichia coli and Salmonella present in the small intestine may contribute to the development of NE in broiler chickens. The antibiotic therapy was used to treat the NE; however European Union has imposed a strict ban due to the negative implications of drug resistance. Moreover, antibiotic growth promoters cause adverse effects on human health as results of withdrawal of antibiotic residues in the chicken meat. After restriction on use of antibiotics, numerous studies have been carried out to investigate the alternatives to antibiotics for controlling NE. Thus, possible alternatives to prevent NE are bio-therapeutic agents (Probiotics), prebiotics, organic acids and essential oils which help in nutrients digestion, immunity enhancement and overall broiler performance. Recently, probiotics are extensively used alternatives to antibiotics for improving host health status and making them efficient in production. The aim of review is to describe a replacement to antibiotics by using different microbial strains as probiotics such as bacteria and yeasts etc. having bacteriostatic properties which inhibit growth of pathogens and neutralize the toxins by different modes of action.

Isolation of a Leuconostoc mesenteroides Strain With Anti-Porcine Epidemic Diarrhea Virus Activities From Kefir Grains

Swine grown under commercial conditions are vulnerable to environmental exposure to several viruses, which may cause infectious diseases and spread easily and rapidly, resulting in significant economic losses in animal husbandry. Previous studies have suggested that probiotics seem to be a new and promising alternative to vaccinations to protect animals against potential viral infections. In this study, we used the Vero cell culture model of infection to study porcine epidemic diarrhea virus (PEDV). We screened lactic acid bacteria (LAB) with anti-PEDV potential from kefir grains, which are starter cultures used to ferment milk into kefir. Twenty-nine LAB strains were isolated and identified as Enterococcus durans, Lactobacillus kefiri, Lactococcus lactis, and Leuconostoc mesenteroides, according to 16S ribosomal RNA (rRNA) and rpoA gene sequence analyses. The anti-PEDV activities of the LAB intracellular extracts were compared, and the intracellular extracts of Ln. mesenteroides showed higher anti-PEDV activities than that of the other species. Among the Ln. mesenteroides strains, a strain designated YPK30 showed a higher growth rate than that of the other strains and was further evaluated for its anti-PEDV activity. The results showed that the intracellular extracts of Ln. mesenteroides YPK30 possessed in vitro prophylactic, therapeutic, and direct-inhibitory effects against PEDV in the Vero cell model. The expression levels of Type 1 interferon (IFN)-dependent genes, including Myxovirus resistance 1 (MX1) and interferon-stimulated gene 15 (ISG15), were significantly increased after treatment with intracellular extracts of Ln. mesenteroides YPK30 for 24 h. Such expression suggests that the anti-PEDV activity of Ln. mesenteroides YPK30 could be attributed to its up-regulatory effect on the expression of MX1 and ISG15 genes. These results suggested that Ln. mesenteroides YPK30 has the potential to provide some levels of host protection against PEDV infections.

Immune-Inflammation in Atherosclerosis: A New Twist in an Old Tale

Background and Objective:

Atherosclerosis, a chronic and progressive inflammatory disease, is triggered by the activation of endothelial cells followed by infiltration of innate and adaptive immune cells including monocytes and T cells in arterial walls. Major populations of T cells found in human atherosclerotic lesions are antigen-specific activated CD4+ effectors and/or memory T cells from Th1, Th17, Th2 and Treg subsets. In this review, we will discuss the significance of T cell orchestrated immune inflammation in the development and progression of atherosclerosis.

Discussion:

Pathogen/oxidative stress/lipid induced primary endothelial wound cannot develop to a full-blown atherosclerotic lesion in the absence of chronically induced inflammation. While the primary inflammatory response might be viewed as a lone innate response, the persistence of such a profound response over time must be (and is) associated with diverse local and systemic T cell responses. The interplay between T cells and innate cells contributes to a phenomenon called immuneinflammation and has an impact on the progression and outcome of the lesion. In recent years immuneinflammation, an old term, has had a comeback in connecting the puzzle pieces of chronic inflammatory diseases.

Conclusion:

Taking one-step back and looking from afar at the players of immune-inflammation may help us provide a broader perspective of these complicated interactions. This may lead to the identification of new drug targets and the development of new therapies as well as preventative measures.

In vitro assessment of immunomodulatory and anti-Campylobacter activities of probiotic lactobacilli

The present study was undertaken to assess the antimicrobial activity of Lactobacillus spp. (L. salivarius, L. johnsonii, L. reuteri, L. crispatus, and L. gasseri) against Campylobacter jejuni as well as their immunomodulatory capabilities. The results demonstrated that lactobacilli exhibit differential antagonistic effects against C. jejuni and vary in their ability to elicit innate responses in chicken macrophages. All lactobacilli exerted inhibitory effects on C. jejuni growth, abrogated the production of the quorum sensing molecule autoinducer-2 (AI-2) by C. jejuni and inhibited the invasion of C. jejuni in human intestinal epithelial cells. Additionally, all lactobacilli, except L. reuteri, significantly reduced the expression of virulence-related genes in C. jejuni, including genes responsible for motility (flaA, flaB, and flhA), invasion (ciaB), and AI-2 production (luxS). All lactobacilli enhanced C. jejuni phagocytosis by macrophages and increased the expression of interferon (IFN)-γ, interleukin (IL)-1β, IL-12p40, IL-10, and chemokine (CXCLi2) in macrophages. Furthermore, L. salivarius, L. reuteri, L. crispatus, and a mixture of all lactobacilli significantly increased expression of the co-stimulatory molecules CD40, CD80, and CD86 in macrophages. In conclusion, these findings demonstrate that lactobacilli possess anti-Campylobacter and immunomodulatory activities. Further studies are needed to assess their protective efficacy against intestinal colonization by C. jejuni in broiler chickens.

Extracellular Membrane Vesicles from Lactobacilli Dampen IFN-γ Responses in a Monocyte-Dependent Manner

Secreted factors derived from Lactobacillus are able to dampen pro-inflammatory cytokine responses. Still, the nature of these components and the underlying mechanisms remain elusive. Here, we aimed to identify the components and the mechanism involved in the Lactobacillus-mediated modulation of immune cell activation. PBMC were stimulated in the presence of the cell free supernatants (CFS) of cultured Lactobacillus rhamnosus GG and Lactobacillus reuteri DSM 17938, followed by evaluation of cytokine responses. We show that lactobacilli-CFS effectively dampen induced IFN-γ and IL-17A responses from T- and NK cells in a monocyte dependent manner by a soluble factor. A proteomic array analysis highlighted Lactobacillus-induced IL-1 receptor antagonist (ra) as a potential candidate responsible for the IFN-γ dampening activity. Indeed, addition of recombinant IL-1ra to stimulated PBMC resulted in reduced IFN-γ production. Further characterization of the lactobacilli-CFS revealed the presence of extracellular membrane vesicles with a similar immune regulatory activity to that observed with the lactobacilli-CFS. In conclusion, we have shown that lactobacilli produce extracellular MVs, which are able to dampen pro-inflammatory cytokine responses in a monocyte-dependent manner.

Lactobacillus reuteri protects mice against Salmonella typhimurium challenge by activating macrophages to produce nitric oxide

Lactobacillus reuteri, a typical intestinal symbiotic bacterium, plays an important role in maintaining intestinal flora stability and host health. However, the effect of Lactobacillus reuteri on peritoneal macrophages has not been thoroughly studied. Our study indicated that Lactobacillus reuteri could activate macrophages and that macrophages treated with Lactobacillus reuteri have an enhanced ability to phagocytose and to kill intracellular Salmonella typhimurium. Lactobacillus reuteri may reduce the inflammatory response caused by Salmonella typhimurium by regulating NO, thus effectively protecting mice against Salmonella typhimurium invasion and dissemination to the liver and spleen. Taken together, these data demonstrated the protective effect of Lactobacillus reuteri on macrophages and mice challenged with Salmonella typhimurium through in vitro and in vivo experiments.

Probiotic Bacteria Alter Pattern-Recognition Receptor Expression and Cytokine Profile in a Human Macrophage Model Challenged with Candida albicans and Lipopolysaccharide

Probiotics are live microorganisms that confer benefits to the host health. The infection rate of potentially pathogenic organisms such as Candida albicans, the most common agent associated with mucosal candidiasis, can be reduced by probiotics. However, the mechanisms by which the probiotics interfere with the immune system are largely unknown. We evaluated the effect of probiotic bacteria on C. albicans challenged human macrophages. Macrophages were pretreated with lactobacilli alone (Lactobacillus rhamnosus LR32, Lactobacillus casei L324m, or Lactobacillus acidophilus NCFM) or associated with Escherichia coli lipopolysaccharide (LPS), followed by the challenge with C. albicans or LPS in a co-culture assay. The expression of pattern-recognition receptors genes (CLE7A, TLR2, and TLR4) was determined by RT-qPCR, and dectin-1 reduced levels were confirmed by flow cytometry. The cytokine profile was determined by ELISA using the macrophage cell supernatant. Overall probiotic lactobacilli down-regulated the transcription of CLEC7A (p < 0.05), resulting in the decreased expression of dectin-1 on probiotic pretreated macrophages. The tested Lactobacillus species down-regulated TLR4, and increased TLR2 mRNA levels in macrophages challenged with C. albicans. The cytokines profile of macrophages challenged with C. albicans or LPS were altered by the probiotics, which generally led to increased levels of IL-10 and IL-1β, and reduction of IL-12 production by macrophages (p < 0.05). Our data suggest that probiotic lactobacilli impair the recognition of PAMPs by macrophages, and alter the production of pro/anti-inflammatory cytokines, thus modulating inflammation.

Interactions between lactobacilli and chicken macrophages induce antiviral responses against avian influenza virus

Macrophages are an important cell type of the innate immune system that upon activation, can exert antiviral functions and also can induce virus-specific adaptive immune responses. Macrophage interaction with certain probiotic bacteria such as lactobacilli can enhance antiviral functions of these cells. We have previously shown that administration of lactobacilli to chickens can effectively augment immune response to vaccine antigens. Here, we investigated the effects of representative strains of three Lactobacillus species, L. acidophilus, L. reuteri and L. salivarius used alone or in combination, in enhancing antiviral activity of chicken macrophages against avian influenza virus in an in vitro model using MQ-NCSU cells. Treatment of macrophages with probiotic lactobacilli significantly enhanced the antiviral functions, as determined by the virus titration assay. We also found that lactobacilli stimulation of macrophages induced significantly higher expression of interleukin (IL)-1β, interferon (IFN)- γ and IFN-α cytokine genes as well as interferon regulatory factor-7 (IRF7), 2',5'-oligoadenylate synthetase (OAS) and interferon-inducible transmembrane protein M3 (IFITM3) genes. Furthermore, macrophages that were treated with lactobacilli had significantly enhanced production of nitric oxide (NO) and IFN-γ protein as well as surface expression of the costimulatory molecule CD40. However, the antiviral and immunostimulatory effects of probiotic lactobacilli largely depended on the Lactobacillus species studied. Collectively, the results from our study using an in vitro model showed that certain Lactobacillus species can effectively augment antiviral responses in chicken macrophages.

The regulation of immune cells by Lactobacilli: a potential therapeutic target for anti-atherosclerosis therapy

Atherosclerosis is an inflammatory disease regulated by several immune cells including lymphocytes, macrophages and dendritic cells. Gut probiotic bacteria like Lactobacilli have been shown immunomodificatory effects in the progression of atherogenesis. Some Lactobacillus stains can upregulate the activity of regulatory T-lymphocytes, suppress T-lymphocyte helper (Th) cells Th1, Th17, alter the Th1/Th2 ratio, influence the subsets ratio of M1/M2 macrophages, inhibit foam cell formation by suppressing macrophage phagocytosis of oxidized low-density lipoprotein, block the activation of the immune system with dendritic cells, which are expected to suppress the atherosclerosis-related inflammation. However, various strains can have various effects on inflammation. Some other Lactobacillus strains were found have potential pro-atherogenic effect through promote Th1 cell activity, increase pro-inflammatory cytokines levels as well as decrease anti-inflammatory cytokines levels. Thus, identifying the appropriate strains is essential to the therapeutic potential of Lactobacilli as an anti-atherosclerotic therapy.

Capacity of lactic acid bacteria in immunity enhancement and cancer prevention

Lactic acid bacteria are associated with the human gastrointestinal tract. They are important for maintaining the balance of microflora in the human gut. An increasing number of published research reports in recent years have denoted the importance of producing interferon-gamma and IgA for treatment of disease. These agents can enhance the specific and nonspecific immune systems that are dependent on specific bacterial strains. The mechanisms of these effects were revealed in this investigation, where the cell walls of these bacteria were modulated by the cytokine pathways, while the whole bacterial cell mediated the host cell immune system and regulated the production of tumor necrosis factors and interleukins. A supplement of highly active lactic acid bacteria strains provided significant potential to enhance host's immunity, offering prevention from many diseases including some cancers. This review summarizes the current understanding of the function of lactic acid bacteria immunity enhancement and cancer prevention.