Neonatal colonization of germ-free mice with Bifidobacterium longum prevents allergic sensitization to major birch pollen allergen Bet v 1

Polysaccharide BAP1 of Bifidobacterium adolescentis CCDM 368 is a biologically active molecule with immunomodulatory properties

Bifidobacteria are among the most common bacteria used for their probiotic properties and their impact on the maturation and function of the immune system has been well-described. Recently, scientific interest is shifting from live bacteria to defined bacteria-derived biologically active molecules. Their greatest advantage over probiotics is the defined structure and the effect independent of the viability status of the bacteria. Here, we aim to characterize Bifidobacterium adolescentis CCDM 368 surface antigens that include polysaccharides (PSs), lipoteichoic acids (LTAs), and peptidoglycan (PG). Among them, Bad368.1 PS was observed to modulate OVA-induced cytokine production in cells isolated from OVA-sensitized mice by increasing the production of Th1-related IFN-γ and inhibition of Th2-related IL-5 and IL-13 cytokines (in vitro). Moreover, Bad368.1 PS (BAP1) is efficiently engulfed and transferred between epithelial and dendritic cells. Therefore, we propose that the Bad368.1 PS (BAP1) can be used for the modulation of allergic diseases in humans. Structural studies revealed that Bad368.1 PS has an average molecular mass of approximately 9,99 × 10⁶ Da and it consists of glucose, galactose, and rhamnose residues that are creating the following repeating unit: →2)-β-D-Glcp-1→3-β-L-Rhap-1→4-β-D-Glcp-1→3-α-L-Rhap-1→4-β-D-Glcp-1→3-α-D-Galp-(1→_n.

The modulation and mechanism of probiotic-derived polysaccharide capsules on the immune response in allergic diseases

Allergic diseases, derived from the dysregulation of immune tolerance mechanisms, have been rising in the last two decades. Recently, increasing evidence has shown that probiotic-derived polysaccharide capsules exhibit a protective effect against allergic diseases, involving regulation of Th1/Th2 balance, induction of differentiation of T regulatory cells and activation of dendritic cells (DCs). DCs have a central role in controlling the immune response through their interaction with gut microbiota via their pattern recognition receptors, including Toll-like receptors and C-type-lectin receptors. This review discusses the effects and critical mechanism of probiotic-derived polysaccharide capsules in regulating the immune system to alleviate allergic diseases. We first describe the development of immune response in allergic diseases and recent relevant findings. Particular emphasis is placed on the effects of probiotic-derived polysaccharide capsules on allergic immune response. Then, we discuss the underlying mechanism of the impact of probiotic-derived polysaccharide capsules on DCs-mediated immune tolerance induction.

The Efficacy of Fecal Transplantation and Bifidobacterium Supplementation in Ameliorating Propionic Acid-Induced Behavioral and Biochemical Autistic Features in Juvenile Male Rats

Gut microbiota plays a major role in neurological disorders, including autism. Modulation of the gut microbiota through fecal microbiota transplantation (FMT) or probiotic administration, such as Bifidobacteria, is suggested to alleviate autistic symptoms; however, their effects on the brain are not fully examined. We tested both approaches in a propionic acid (PPA) rodent model of autism as treatment strategies. Autism was induced in Sprague-Dawley rats by administering PPA orally (250 mg/kg) for 3 days. Animals were later treated with either saline, FMT, or Bifidobacteria for 22 days. Control animals were treated with saline throughout the study. Social behavior and selected brain biochemical markers related to stress hormones, inflammation, and oxidative stress were assessed. PPA treatment induced social impairments, which was rescued by the treatments. In the brain, Bifidobacteria treatment increased oxytocin relative to control and PPA groups. Moreover, Bifidobacteria treatment rescued the PPA-induced increase in IFN-γ levels. Both treatments increased GST levels, which was diminished by the PPA treatment. These findings indicate the potential of gut microbiota-targeted therapeutics in ameliorating behavioral deficit and underlying neural biochemistry.

Role of Bifidobacteria on Infant Health

Bifidobacteria are among the predominant microorganisms during infancy, being a dominant microbial group in the healthy breastfed infant and playing a crucial role in newborns and infant development. Not only the levels of the Bifidobacterium genus but also the profile and quantity of the different bifidobacterial species have been demonstrated to be of relevance to infant health. Although no definitive proof is available on the causal association, reduced levels of bifidobacteria are perhaps the most frequently observed alteration of the intestinal microbiota in infant diseases. Moreover, Bifidobacterium strains have been extensively studied by their probiotic attributes. This review compiles the available information about bifidobacterial composition and function since the beginning of life, describing different perinatal factors affecting them, and their implications on different health alterations in infancy. In addition, this review gathers exhaustive information about pre-clinical and clinical studies with Bifidobacterium strains as probiotics in neonates.

Viability Status-Dependent Effect of Bifidobacterium longum ssp. longum CCM 7952 on Prevention of Allergic Inflammation in Mouse Model

The classical definition of probiotics states that bacteria must be alive to be beneficial for human organism. However, recent reports show that inactivated bacteria or their effector molecules can also possess such properties. In this study, we investigated the physical and immunomodulatory properties of four Bifidobacterium strains in the heat-treated (HT) and untreated (UN) forms. We showed that temperature treatment of bacteria changes their size and charge, which affects their interaction with epithelial and immune cells. Based on the in vitro assays, we observed that all tested strains reduced the level of OVA-induced IL-4, IL-5, and IL-13 in the spleen culture of OVA-sensitized mice. We selected Bifidobacterium longum ssp. longum CCM 7952 (Bl 7952) for further analysis. In vivo experiments confirmed that untreated Bl 7952 exhibited allergy-reducing properties when administered intranasally to OVA-sensitized mice, which manifested in significant suppression of airway inflammation. Untreated Bl 7952 decreased local and systemic levels of Th2 related cytokines, OVA-specific IgE antibodies and simultaneously inhibited airway eosinophilia. In contrast, heat-treated Bl 7952 was only able to reduce IL-4 levels in the lungs and eosinophils in bronchoalveolar lavage, but increased neutrophil and macrophage numbers. We demonstrated that the viability status of Bl 7952 is a prerequisite for the beneficial effects of bacteria, and that heat treatment reduces but does not completely abolish these properties. Further research on bacterial effector molecules to elucidate the beneficial effects of probiotics in the prevention of allergic diseases is warranted.

Pre- and Neonatal Imprinting on Immunological Homeostasis and Epithelial Barrier Integrity by Escherichia coli Nissle 1917 Prevents Allergic Poly-Sensitization in Mice

A steady rise in the number of poly-sensitized patients has increased the demand for effective prophylactic strategies against multi-sensitivities. Probiotic bacteria have been successfully used in clinics and experimental models to prevent allergic mono-sensitization. In the present study, we have investigated whether probiotic bacteria could prevent poly-sensitization by imprinting on the immune system early in life. We used two recombinant variants of probiotic Escherichia coli Nissle 1917 (EcN): i) EcN expressing birch and grass pollen, poly-allergen chimera construct (EcN-Chim), and ii) an “empty” EcN without allergen expression (EcN-Ctrl). Conventional mice (CV) were treated with either EcN-Chim or EcN-Ctrl in the last week of the gestation and lactation period. Gnotobiotic mice received one oral dose of either EcN-Chim or EcN-Ctrl before mating. The offspring from both models underwent systemic allergic poly-sensitization and intranasal challenge with recombinant birch and grass pollen allergens (rBet v 1, rPhl p 1, and rPhl p 5). In the CV setting, the colonization of offspring via treatment of mothers reduced allergic airway inflammation (AAI) in offspring compared to poly-sensitized controls. Similarly, in a gnotobiotic model, AAI was reduced in EcN-Chim and EcN-Ctrl mono-colonized offspring. However, allergy prevention was more pronounced in the EcN-Ctrl mono-colonized offspring as compared to EcN-Chim. Mono-colonization with EcN-Ctrl was associated with a shift toward mixed Th1/Treg immune responses, increased expression of TLR2 and TLR4 in the lung, and maintained levels of zonulin-1 in lung epithelial cells as compared to GF poly-sensitized and EcN-Chim mono-colonized mice. This study is the first one to establish the model of allergic poly-sensitization in gnotobiotic mice. Using two different settings, gnotobiotic and conventional mice, we demonstrated that an early life intervention with the EcN without expressing an allergen is a powerful strategy to prevent poly-sensitization later in life.

The Relationship between the Infant Gut Microbiota and Allergy. The Role of Bifidobacterium breve and Prebiotic Oligosaccharides in the Activation of Anti-Allergic Mechanisms in Early Life

The increase in allergy prevalence observed in recent decades may be a consequence of early intestinal dysbiosis. The intestinal microbiota is formed in the first 1000 days of life, when it is particularly sensitive to various factors, such as the composition of the mother’s microbiota, type of delivery, infant’s diet, number of siblings, contact with animals, and antibiotic therapy. Breastfeeding and vaginal birth favorably affect the formation of an infant’s intestinal microbiota and protect against allergy development. The intestinal microbiota of these infants is characterized by an early dominance of Bifidobacterium, which may have a significant impact on the development of immune tolerance. Bifidobacterium breve is a species commonly isolated from the intestines of healthy breastfed infants and from human milk. This review outlines the most important environmental factors affecting microbiota formation and the importance of Bifidobacterium species (with a particular emphasis on Bifidobacterium breve) in microbiota modulation towards anti-allergic processes. In addition, we present the concept, which assumes that infant formulas containing specific probiotic Bifidobacterium breve strains and prebiotic oligosaccharides may be useful in allergy management in non-breastfed infants.

Bacterial species to be considered in quality assurance of mice and rats

Bacteria are relevant in rodent quality assurance programmes if (a) the animals are at risk and (b) presence in the animals makes a difference for animal research or welfare, for example because the agent regulates clinical disease progression or impacts its host in other ways. Furthermore, zoonoses are relevant. Some bacterial species internationally recommended for the health monitoring of rats and mice, that is, Citrobacter rodentium, Corynebacterium kutscheri, Salmonella spp. and Streptococcus pneumonia, are no longer found in either laboratory or pet shop rats or mice, while there is still a real risk of impact on animal research and welfare from Filobacterium rodentium, Clostridium piliforme, Mycoplasma spp., Helicobacter spp. and Rodentibacter spp., while Streptobacillus moniliformis may be considered a serious zoonotic agent in spite of a very low risk. Modern molecular techniques have revealed that there may, depending on the research type, be equally good reasons for knowing the colony status of some commensal bacteria that are essential for the induction of specific rodent models, such as Alistipes spp., Akkermansia muciniphila, Bifidobacterium spp., Bacteroides fragilis, Bacteroides vulgatus, Faecalibacterium prausnitzii, Prevotella copri and segmented filamentous bacteria. In future, research groups should therefore consider the presence or absence of a short list of defined bacterial species relevant for their models. This list can be tested by cost-effective sequencing or even a simple multiple polymerase chain reaction approach, which is likely to be cost-neutral compared to more traditional screening methods.

Germ-Free Mice Exhibit Mast Cells With Impaired Functionality and Gut Homing and Do Not Develop Food Allergy

Background: Mucosal mast cells (MC) are key players in IgE-mediated food allergy (FA). The evidence on the interaction between gut microbiota, MC and susceptibility to FA is contradictory.

Objective: We tested the hypothesis that commensal bacteria are essential for MC migration to the gut and their maturation impacting the susceptibility to FA.

Methods: The development and severity of FA symptoms was studied in sensitized germ-free (GF), conventional (CV), and mice mono-colonized with L. plantarum WCFS1 or co-housed with CV mice. MC were phenotypically and functionally characterized.

Results: Systemic sensitization and oral challenge of GF mice with ovalbumin led to increased levels of specific IgE in serum compared to CV mice. Remarkably, despite the high levels of sensitization, GF mice did not develop diarrhea or anaphylactic hypothermia, common symptoms of FA. In the gut, GF mice expressed low levels of the MC tissue-homing markers CXCL1 and CXCL2, and harbored fewer MC which exhibited lower levels of MC protease-1 after challenge. Additionally, MC in GF mice were less mature as confirmed by flow-cytometry and their functionality was impaired as shown by reduced edema formation after injection of degranulation-provoking compound 48/80. Co-housing of GF mice with CV mice fully restored their susceptibility to develop FA. However, this did not occur when mice were mono-colonized with L. plantarum.

Conclusion: Our results demonstrate that microbiota-induced maturation and gut-homing of MC is a critical step for the development of symptoms of experimental FA. This new mechanistic insight into microbiota-MC-FA axis can be exploited in the prevention and treatment of FA in humans.

Commensal microbiota induces colonic barrier structure and functions that contribute to homeostasis

The intestinal barrier encompasses structural, permeability and immune aspects of the gut mucosa that, when disrupted, may contribute to chronic inflammation. Although gnotobiotic studies have demonstrated the effects of microbiota on mucosal and systemic immunity, as well as intestinal barrier architecture and innate immune characteristics, its impact on barrier function remains unclear. We compared germ-free and conventional mice, as well as mice colonized with human fecal microbiota that were followed for 21 days post-colonization. Colonic barrier structure was investigated by immunohistochemistry, molecular and electron microscopy techniques. Permeability was assessed in colon tissue by Ussing chambers, and by serum LPS and MDP detection using TLR4- and NOD2-NFκB reporter assays. Microbiota profile was determined by Illumina 16S rRNA gene sequencing. Low dose dextran sodium sulfate was administered to assess microbiota-induced barrier changes on resistance to colonic injury. Permeability to paracellular probes and mucus layer structure resembled that of conventional mice by day 7 post-colonization, coinciding with reduced claudin-1 expression and transient IL-18 production by intestinal epithelial cells. These post-colonization adaptations were associated with decreased systemic bacterial antigen exposure and reduced susceptibility to intestinal injury. In conclusion, commensal colonization promotes physiological barrier structural and functional adaptations that contribute to intestinal homeostasis.

Probiotics against airway allergy: host factors to consider

The worldwide prevalence of allergic diseases has drastically increased in the past decades. Recent studies underline the importance of microbial exposure for the development of a balanced immune system. Consequently, probiotic bacteria are emerging as a safe and natural strategy for allergy prevention and treatment. However, clinical probiotic intervention studies have so far yielded conflicting results. There is increasing awareness about the importance of host-associated factors that determine whether an individual will respond to a specific probiotic treatment, and it is therefore crucial to promote a knowledge-based instead of an empirical selection of promising probiotic strains and their administration regimen.In this Review, we summarize the insights from animal model studies of allergic disease, which reveal how host-related factors - such as genetic makeup, sex, age and microbiological status - can impact the outcomes of preventive or curative probiotic treatment. We explore why and how these factors can influence the results of probiotic studies and negatively impact the reproducibility in animal experiments. These same factors might profoundly influence the outcomes of human clinical trials, and can potentially explain the conflicting results from probiotic intervention studies. Therefore, we also link these host-related factors to human probiotic study outcomes in the context of airway allergies.

Immune-modulatory genomic properties differentiate gut microbiota of infants with and without eczema

Gut microbiota play an important role in human immunological processes, potentially affecting allergic diseases such as eczema. The diversity and structure of gut microbiota in infants with eczema have been previously documented. This study aims to evaluate by comparative metagenomics differences in genetic content in gut microbiota of infants with eczema and their matched controls. Stools were collected at the age of one month old from twelve infants from an at risk birth cohort in a case control manner. Clinical follow up for atopic outcomes were carried out at the age of 12 and 24 months. Microbial genomic DNA were extracted from stool samples and used for shotgun sequencing. Comparative metagenomic analysis showed that immune-regulatory TCAAGCTTGA motifs were significantly enriched in the six healthy controls (C) communities compared to the six eczema subjects (E), with many encoded by Bifidobacterium (38% of the total motifs in the C communities). Draft genomes of five Bifidobacterium species populations (B. longum, B. bifidum, B. breve, B. dentium, and B. pseudocatenulatum) were recovered from metagenomic datasets. The B. longum BFN-121-2 genome encoded more TCAAGCTTGA motifs (4.2 copies per one million genome sequence) than other Bifidobacterium genomes. Additionally, the communities in the stool of controls (C) were also significantly enriched in functions associated with tetrapyrrole biosynthesis compared to those of eczema (E). Our results show distinct immune-modulatory genomic properties of gut microbiota in infants associated with eczema and provide new insights into potential role of gut microbiota in affecting human immune homeostasis.

Murine models for mucosal tolerance in allergy

Immunity is established by a fine balance to discriminate between self and non-self. In addition, mucosal surfaces have the unique ability to establish and maintain a state of tolerance also against non-self constituents such as those represented by the large numbers of commensals populating mucosal surfaces and food-derived or air-borne antigens. Recent years have seen a dramatic expansion in our understanding of the basic mechanisms and the involved cellular and molecular players orchestrating mucosal tolerance. As a direct outgrowth, promising prophylactic and therapeutic models for mucosal tolerance induction against usually innocuous antigens (derived from food and aeroallergen sources) have been developed. A major theme in the past years was the introduction of improved formulations and novel adjuvants into such allergy vaccines. This review article describes basic mechanisms of mucosal tolerance induction and contrasts the peculiarities but also the interdependence of the gut and respiratory tract associated lymphoid tissues in that context. Particular emphasis is put on delineating the current prophylactic and therapeutic strategies to study and improve mucosal tolerance induction in allergy.

Bifidobacterium longum affects the methylation level of forkhead box P3 promoter in 2, 4, 6-trinitrobenzenesulphonic acid induced colitis in rats

Bifidobacterium longum (B. Longum) is a common probiotic colonized in the human gut and against the development of chronic inflammation including inflammatory bowel disease (IBD). But the underlying mechanism remains unknown. The aim of this study was to evaluate the affection of B. longum on the methylation levels of forkhead box P3 (Foxp3) promoter. 2, 4, 6-trinitrobenzenesulphonic acid (TNBS)-induced colitis rat models were treated with B. longum or medium, respectively. The genomic DNA of spleen peripheral blood mononuclear cells (PBMC) cells was extracted. After bisulphite treatment and pyrosequencing, the methylation levels of each CpG sites in the promoter of forkhead box protein P3 (Foxp3) were analyzed. B. Longum treatment changes the methylation level in Foxp3 promoter in TNBS-treated colitis rats, and significantly demethylates several CpG sites in Foxp3 promoter. The demethylation of Foxp3 promoter might be involved in the effectiveness of B. Longum treatment for IBD. Further research remains necessary to investigate the role of B. Longum in Foxp3 demethylation. Using B. Longum or its metabolic products is an option for further investigations on potential treatments for IBD.

Neonatal mono-colonization of germ-free mice with Lactobacillus casei enhances casein immunogenicity after oral sensitization to cow's milk

SCOPE

Food allergy is an increasing global health problem and perinatal administration of probiotic bacteria is currently under investigation in order to prevent the development of allergic diseases. Here, we investigated the impact of neonatal mono-colonization of mice with Lactobacillus casei BL23 on an oral sensitization to cow's milk.

METHODS AND RESULTS

Mono-colonized (LC) mice were obtained by inoculating L. casei to germ-free (GF) parents. Nine-week-old GF, LC, and conventional (CV) mice were orally sensitized to cow's milk with cholera toxin as adjuvant. Compared to GF and CV mice, LC mice developed higher casein-specific IgG responses. In contrast, no significant differences between GF and LC mice were observed for the humoral responses against whey proteins. Immunoblotting experiments performed on αS1-casein hydrolysates revealed the presence of small peptides immunoreactive with sera from LC mice but not from GF mice. After in vitro reactivation of splenocytes, secretion of IL-17 was higher in LC mice than in GF and CV mice.

CONCLUSION

Neonatal mono-colonization by L. casei BL23 modulated the allergic sensitization toward food antigens. Furthermore, our data suggest that casein-specific humoral responses in LC mice were enhanced because of casein hydrolysis by L. casei into immunogenic peptides.

Polysaccharides L900/2 and L900/3 isolated from Lactobacillus rhamnosus LOCK 0900 modulate allergic sensitization to ovalbumin in a mouse model

Here, we compared the abilities of polysaccharides L900/2 and L900/3, which were previously isolated from Lactobacillus rhamnosus LOCK 0900, to modulate the immune response to bystander antigens in a mouse model of ovalbumin (OVA) sensitization. In vivo, both polysaccharides reduced the levels of OVA‐specific IgE, IgE‐dependent basophil degranulation and IgG2a antibodies, but had no effect on the levels of OVA‐specific IgA or IgG1. Interestingly, both polysaccharides triggered recall cellular responses with distinct properties. L900/3 significantly suppressed the OVA‐induced upregulations of IL‐4, IL‐5, IL‐10 and IL‐13 in re‐stimulated spleen cells and mesenteric lymph nodes. Our findings support and expand on our previous in vitro studies by demonstrating that polymer L900/3 might modulate the Th1/Th2 balance and could be a promising candidate molecule for preventing allergic sensitization.

Diet Matters: Endotoxin in the Diet Impacts the Level of Allergic Sensitization in Germ-Free Mice

Germ-free animals have been used to define the vital role of commensal bacteria on the maturation of the host immune system. However, the role of bacterial residues in diet in this setting is poorly understood. Here we investigated the effect of bacterial contamination in sterile diet on the level of allergic sensitization in germ-free mice. Sterile grain-based diets ST1 and R03 were tested for the level of bacterial contamination. ST1 contained higher amount of bacterial DNA, approximately ten times more endotoxin, and induced higher, TLR4-dependent, cytokine production in dendritic cells compared to R03. In a germ-free mouse model of sensitization to the major birch pollen allergen Bet v 1, feeding on ST1 for at least two generations was associated with decreased production of allergen-specific IgE and IgG1 antibodies in sera in comparison to R03. Furthermore, reduced levels of allergen-specific and ConA-induced cytokines IL-4, IL-5 and IL-13 accompanied by increased levels of IFN-γ were detected in splenocytes cultures of these mice. Our results show that contamination of experimental diet with bacterial residues, such as endotoxin, significantly affects the development of allergic sensitization in germ-free mice. Therefore, careful selection of sterile food is critical for the outcomes of germ-free or gnotobiotic experimental models of immune-deviated diseases.

The Use of Adjuvants for Enhancing Allergen Immunotherapy Efficacy

One key approach to increase the efficacy and the safety of immunotherapy is the use of adjuvants. However, many of the adjuvants currently in use can cause adverse events, raising concerns regarding their clinical use, and are geared toward productive immune responses but not necessarily tolerogenic responses. Thus, novel adjuvants for immunotherapy are needed and are being developed. Essential is their potential to boost appropriate tolerogenic adaptive immune responses to allergens while limiting side effects. This review provides an overview of adjuvants currently in clinical use or under development and discusses their therapeutic effect in enhancing allergen-induced tolerance.

A Review of Applied Aspects of Dealing with Gut Microbiota Impact on Rodent Models

The gut microbiota (GM) affects numerous human diseases, as well as rodent models for these. We will review this impact and summarize ways to handle this challenge in animal research. The GM is complex, with the largest fractions being the gram-positive phylum Firmicutes and the gram-negative phylum Bacteroidetes. Other important phyla are the gram-negative phyla Proteobacteria and Verrucomicrobia, and the gram-positive phylum Actinobacteria. GM members influence models for diseases, such as inflammatory bowel diseases, allergies, autoimmunity, cancer, and neuropsychiatric diseases. GM characterization of all individual animals and incorporation of their GM composition in data evaluation may therefore be considered in future protocols. Germfree isolator-housed rodents or rodents made virtually germ free by antibiotic cocktails can be used to study diverse microbial influences on disease expression. Through subsequent inoculation with selected strains or cocktails of microbes, new "defined flora" models can yield valuable knowledge on the impact of the GM, and of specific GM members and their interactions, on important disease phenotypes and mechanisms. Rodent husbandry and microbial quality assurance practices will be important to ensure and confirm appropriate and research relevant GM.

Bosom Buddies: The Symbiotic Relationship Between Infants and Bifidobacterium longum ssp. longum and ssp. infantis. Genetic and Probiotic Features

The intestinal microbiota is a complex community that plays an important role in human health from the initial steps of its establishment. Its microbial composition has been suggested to result from selective pressures imposed by the host and is modulated by competition among its members. Bifidobacterium longum is one of the most abundant species of the Bifidobacterium genus in the gut microbiota of healthy breast-fed infants and adults. The recent advancements of 'omics techniques have facilitated the genetic and functional studies of different gut microbiota members. They have revealed the complex genetic pathways used to metabolize different compounds that likely contribute to the competitiveness and persistence of B. longum in the colon. The discovery of a genomic island in B. longum ssp. infantis that encodes specific enzymes for the metabolism of human milk oligosaccharides suggests a specific ecological adaptation. Moreover, B. longum is widely used as probiotic, and beneficial effects in infant health have been reported in several studies.

Bifidobacterium longum BBMN68-specific modulated dendritic cells alleviate allergic responses to bovine β-lactoglobulin in mice

AIMS

This study was designed to demonstrate the protective effects of Bifidobacterium longum BBMN68-specific modulated dendritic cells (DCs) on allergic inflammation in β-lactoglobulin (BLG)-sensitized mice.

METHODS AND RESULTS

BALB/c mice were sensitized to BLG in accordance with a model of food allergy protocol and given oral BBMN68 daily. BBMN68 was found to significantly reduce BLG-specific hypersensitivity reactions by suppressing the aberrant balance of Th1/Th2 responses with increasing the number of CD4+CD25+Foxp3+ Treg cells in mesenteric lymph nodes (MLN) by 48·1%. The level of CD103+DCs was up-regulated by 136·7 and 56·2% in payer's patches and MLN, respectively, in response to the lower expression levels of cell-surface molecules (CD86 and MHC-II) induced by BBMN68 supplementation. The CD11c+DCs isolated from BBMN68 mice showed 45·6% more Foxp3+ expression in vitro.

CONCLUSIONS

These data suggest that BBMN68-specific induction of CD11c+CD103+DCs and semi-mature DCs reduce BLG allergic reactions.

SIGNIFICANCE AND IMPACT OF THE STUDY

These data confirm that BBMN68 may be a suitable therapeutic approach to the alleviation of food allergies, and BBMN68-specific induction of CD11c+CD103+DCs and semi-mature DCs are associated with this protection.

Allergen immunotherapy for birch pollen-allergic patients: recent advances

As of today, allergen immunotherapy is performed with aqueous natural allergen extracts. Recombinant allergen vaccines are not yet commercially available, although they could provide patients with well-defined and highly consistent drug substances. As Bet v 1 is the major allergen involved in birch pollen allergy, with more than 95% of patients sensitized to this allergen, pharmaceutical-grade recombinant Bet v 1-based vaccines were produced and clinically tested. Herein, we compare the clinical results and modes of action of treatments based on either a birch pollen extract or recombinant Bet v 1 expressed as hypoallergenic or natural-like molecules. We also discuss the future of allergen immunotherapy with improved drugs intended for birch pollen-allergic patients suffering from rhinoconjunctivitis.

Bifidobacterium longum CCM 7952 Promotes Epithelial Barrier Function and Prevents Acute DSS-Induced Colitis in Strictly Strain-Specific Manner

BACKGROUND

Reduced microbial diversity has been associated with inflammatory bowel disease (IBD) and probiotic bacteria have been proposed for its prevention and/or treatment. Nevertheless, comparative studies of strains of the same subspecies for specific health benefits are scarce. Here we compared two Bifidobacterium longum ssp. longum strains for their capacity to prevent experimental colitis.

METHODS

Immunomodulatory properties of nine probiotic bifidobacteria were assessed by stimulation of murine splenocytes. The immune responses to B. longum ssp. longum CCM 7952 (Bl 7952) and CCDM 372 (Bl 372) were further characterized by stimulation of bone marrow-derived dendritic cell, HEK293/TLR2 or HEK293/NOD2 cells. A mouse model of dextran sulphate sodium (DSS)-induced colitis was used to compare their beneficial effects in vivo.

RESULTS

The nine bifidobacteria exhibited strain-specific abilities to induce cytokine production. Bl 372 induced higher levels of both pro- and anti-inflammatory cytokines in spleen and dendritic cell cultures compared to Bl 7952. Both strains engaged TLR2 and contain ligands for NOD2. In a mouse model of DSS-induced colitis, Bl 7952, but not Bl 372, reduced clinical symptoms and preserved expression of tight junction proteins. Importantly, Bl 7952 improved intestinal barrier function as demonstrated by reduced FITC-dextran levels in serum.

CONCLUSIONS

We have shown that Bl 7952, but not Bl 372, protected mice from the development of experimental colitis. Our data suggest that although some immunomodulatory properties might be widespread among the genus Bifidobacterium, others may be rare and characteristic only for a specific strain. Therefore, careful selection might be crucial in providing beneficial outcome in clinical trials with probiotics in IBD.

Colonization of germ-free mice with a mixture of three lactobacillus strains enhances the integrity of gut mucosa and ameliorates allergic sensitization

Increasing numbers of clinical trials and animal experiments have shown that probiotic bacteria are promising tools for allergy prevention. Here, we analyzed the immunomodulatory properties of three selected lactobacillus strains and the impact of their mixture on allergic sensitization to Bet v 1 using a gnotobiotic mouse model. We showed that Lactobacillus (L.) rhamnosus LOCK0900, L. rhamnosus LOCK0908 and L. casei LOCK0919 are recognized via Toll-like receptor 2 (TLR2) and nucleotide-binding oligomerization domain-containing protein 2 (NOD2) receptors and stimulate bone marrow-derived dendritic cells to produce cytokines in species- and strain-dependent manners. Colonization of germ-free (GF) mice with a mixture of all three strains (Lmix) improved the intestinal barrier by strengthening the apical junctional complexes of enterocytes and restoring the structures of microfilaments extending into the terminal web. Mice colonized with Lmix and sensitized to the Bet v 1 allergen showed significantly lower levels of allergen-specific IgE, IgG1 and IgG2a and an elevated total IgA level in the sera and intestinal lavages as well as an increased transforming growth factor (TGF)-β level compared with the sensitized GF mice. Splenocytes and mesenteric lymph node cells from the Lmix-colonized mice showed the significant upregulation of TGF-β after in vitro stimulation with Bet v 1. Our results show that Lmix colonization improved the gut epithelial barrier and reduced allergic sensitization to Bet v 1. Furthermore, these findings were accompanied by the increased production of circulating and secretory IgA and the regulatory cytokine TGF-β. Thus, this mixture of three lactobacillus strains shows potential for use in the prevention of increased gut permeability and the onset of allergies in humans.

Trek1 contributes to maintaining nasal epithelial barrier integrity

Epithelial barrier integrity is critical to maintain the homeostasis in the body. The regulatory mechanism of the epithelial barrier function has not been fully understood. This study aims to elucidate the role of the TWIK-related potassium channel-1 (Trek1) in the regulation of the epithelial barrier function of the nasal mucosa. In this study, the levels of Trek1 were assessed by real time RT-PCR and Western blotting. The epithelial barrier function of the rat nasal epithelia was evaluated by the Ussing chamber system. The results showed that Trek1 was detected in the human and rat nasal epithelia, which were significantly lower in patients and rats with allergic rhinitis than that in healthy controls. Exposure to the signature T helper 2 cytokine, interleukin (IL)-4, markedly suppressed the expression of Trek1 in the nasal mucosa via up regulating the expression of the histone deacetylase (HDAC)1. The IL-4-induced rat nasal epithelial barrier dysfunction could be blocked by HDAC1 inhibitor (Trichostatin A), or sodium butyrate, or administration of Clostridium Butyricum. We conclude that Trek1 is critical to maintain the nasal epithelial barrier function.

Impact of the gut microbiota on rodent models of human disease

Traditionally bacteria have been considered as either pathogens, commensals or symbionts. The mammal gut harbors 10¹⁴ organisms dispersed on approximately 1000 different species. Today, diagnostics, in contrast to previous cultivation techniques, allow the identification of close to 100% of bacterial species. This has revealed that a range of animal models within different research areas, such as diabetes, obesity, cancer, allergy, behavior and colitis, are affected by their gut microbiota. Correlation studies may for some diseases show correlation between gut microbiota composition and disease parameters higher than 70%. Some disease phenotypes may be transferred when recolonizing germ free mice. The mechanistic aspects are not clear, but some examples on how gut bacteria stimulate receptors, metabolism, and immune responses are discussed. A more deeper understanding of the impact of microbiota has its origin in the overall composition of the microbiota and in some newly recognized species, such as Akkermansia muciniphila, Segmented filamentous bacteria and Faecalibacterium prausnitzii, which seem to have an impact on more or less severe disease in specific models. Thus, the impact of the microbiota on animal models is of a magnitude that cannot be ignored in future research. Therefore, either models with specific microbiota must be developed, or the microbiota must be characterized in individual studies and incorporated into data evaluation.

Microorganisms with claimed probiotic properties: an overview of recent literature

Probiotics are defined as live microorganisms, which when administered in adequate amounts, confer a health benefit on the host. Health benefits have mainly been demonstrated for specific probiotic strains of the following genera: Lactobacillus, Bifidobacterium, Saccharomyces, Enterococcus, Streptococcus, Pediococcus, Leuconostoc, Bacillus, Escherichia coli. The human microbiota is getting a lot of attention today and research has already demonstrated that alteration of this microbiota may have far-reaching consequences. One of the possible routes for correcting dysbiosis is by consuming probiotics. The credibility of specific health claims of probiotics and their safety must be established through science-based clinical studies. This overview summarizes the most commonly used probiotic microorganisms and their demonstrated health claims. As probiotic properties have been shown to be strain specific, accurate identification of particular strains is also very important. On the other hand, it is also demonstrated that the use of various probiotics for immunocompromised patients or patients with a leaky gut has also yielded infections, sepsis, fungemia, bacteraemia. Although the vast majority of probiotics that are used today are generally regarded as safe and beneficial for healthy individuals, caution in selecting and monitoring of probiotics for patients is needed and complete consideration of risk-benefit ratio before prescribing is recommended.