Enhancement of Oral Tolerance Induction in DO11.10 Mice by Lactobacillus gasseri OLL2809 via Increase of Effector Regulatory T Cells

Modulation of Mouse Dendritic Cells In Vitro by Lactobacillus gasseri Postbiotic Proteins

Different lactobacilli are probiotics for their beneficial effects that confer to the host. Recently, some of these effects were associated with released metabolic products/constituents (postbiotics). In the present study, the potential immunomodulatory capacity of the probiotic Lactobacillus gasseri OLL2809 cell-free supernatant (sup) was investigated in murine bone marrow-derived dendritic cells (DCs). Bacteria induced significantly higher expression of all examined cytokines than those induced by the stimulatory lipopolysaccharide (LPS) itself. On the contrary, sup only induced the anti-inflammatory IL-10 similarly to LPS, whereas IL-12 and IL-6 secretions were stimulated at a lower level. Moreover, sup reduced the surface expression of the analyzed co-stimulatory markers CD40, CD80, and CD86. Treatments of sup with different digestive enzymes indicated the proteinaceous nature of these immunomodulatory metabolites. Western blot and immunoadsorption analyzes revealed cross-reactivity of sup with the surface-layer proteins (SLPs) isolated from OLL2809. Therefore, we directly tested the ability of OLL2809 SLPs to stimulate specifically cytokine expression in iDCs. Interestingly, we found that all tested cytokines were induced by SLPs and in a dose-dependent manner. In conclusion, our results highlighted distinct immune properties between L. gasseri OLL2809 and its metabolites, supporting the concept that bacterial viability is not an essential prerequisite to exert immunomodulatory effects.

Update on In Vitro Diagnostic Tools and Treatments for Food Allergies

Food allergy (FA) is an adverse immunological reaction to a specific food that can trigger a wide range of symptoms from mild to life-threatening. This adverse reaction is caused by different immunological mechanisms, such as IgE-mediated, non-IgE-mediated and mixed IgE-mediated reactions. Its epidemiology has had a significant increase in the last decade, more so in developed countries. It is estimated that approximately 2 to 10% of the world's population has FA and this number appears to be increasing and also affecting more children. The diagnosis can be complex and requires the combination of different tests to establish an accurate diagnosis. However, the treatment of FA is based on avoiding the intake of the specific allergenic food, thus being very difficult at times and also controlling the symptoms in case of accidental exposure. Currently, there are other immunomodulatory treatments such as specific allergen immunotherapy or more innovative treatments that can induce a tolerance response. It is important to mention that research in this field is ongoing and clinical trials are underway to assess the safety and efficacy of these different immunotherapy approaches, new treatment pathways are being used to target and promote the tolerance response. In this review, we describe the new in vitro diagnostic tools and therapeutic treatments to show the latest advances in FA management. We conclude that although significant advances have been made to improve therapies and diagnostic tools for FA, there is an urgent need to standardize both so that, in their totality, they help to improve the management of FA.

A Higher Dose of Staphylococcus aureus Enterotoxin B Led to More Th1 and Lower Th2/Th1 Ratio in Th Cells

Exposure to Staphylococcus aureus enterotoxin B (SEB) is one of the causes of food poisoning and is associated with several immune diseases due to its superantigen capability. This study aimed to characterize the differentiations of naïve Th cells stimulated with different doses of SEB. The expression of T-bet, GATA-3, and Foxp3 or secretion of IFN-γ, IL-4, IL-5, IL-13, and IL-10 were evaluated in wild-type (WT) or DO11.10 CD4 T cells co-cultured with bone marrow dendritic cells (BMDCs). We found that the balance of Th1/Th2 could be dominated by the doses of SEB stimulation. A higher SEB dose could induce more Th1 and a lower Th2/Th1 ratio in Th cells co-cultured with BMDCs. This different tendency of Th cell differentiation induced by the SEB complements the existing knowledge about SEB acting as a superantigen to activate Th cells. Additionally, it is also helpful in managing the colonization of S. aureus and food contamination of SEB.

The intriguing possibility of using probiotics in allergen-specific immunotherapy

Allergen immunotherapy (AIT) can be considered the etiological therapy for allergic rhinitis and hymenoptera venom allergy. Its role is increasingly emerging in the context of IgE mediated food allergy, where the achievement of tolerance, or the permanent resolution of an allergy, represents the optimal goal of AIT. AIT treatment, indicated in adults and children with allergic rhinitis, has a preventative effect on the development of asthma and can also be used when asthma is associated to rhinitis; however, it is not the first choice for treatment of isolated asthma. While knowledge on immunological mechanisms, efficacy, and safety of AIT is known, an intriguing line of investigation has arisen on how the action of AIT is modulated by the use of probiotics, starting from awareness that the microbiome is altered in allergic conditions: the use of probiotics in inducing the stimulation of innate immunity via toll-like receptor activation, thus acting as adjuvants in AIT, is hereby examined. Therefore, by analyzing literature on AIT and probiotics, we intend to draw attention to how the role and use of AIT are emerging as being increasingly important for both the short- and long-term management of allergic diseases and how recourse probiotics may represent an additional therapeutic strategy to modulate the effectiveness of AIT. However, further investigations are needed to better identify which probiotics to use, the dosage, and the optimal duration to obtain correct immunomodulation, and how to best customize their use, including a "AIT + probiotics" strategy in the field of precision medicine.

Advances in the Study of Probiotics for Immunomodulation and Intervention in Food Allergy

Food allergies are a serious food safety and public health issue. Soybean, dairy, aquatic, poultry, and nut products are common allergens inducing allergic reactions and adverse symptoms such as atopic dermatitis, allergic eczema, allergic asthma, and allergic rhinitis. Probiotics are assumed as an essential ingredient in maintaining intestinal microorganisms' composition. They have unique physiological roles and therapeutic effects in maintaining the mucosal barrier, immune function, and gastrointestinal tract, inhibiting the invasion of pathogenic bacteria, and preventing diarrhea and food allergies. Multiple pieces of evidence reveal a significant disruptive effect of probiotics on food allergy pathology and progression mechanisms. Thus, this review describes the allergenic proteins as an entry point and briefly describes the application of probiotics in allergenic foods. Then, the role of probiotics in preventing and curing allergic diseases by regulating human immunity through intestinal flora and intestinal barrier, modulating host immune active cells, and improving host amino acid metabolism are described in detail. The anti-allergic role of probiotics in the function and metabolism of the gastrointestinal tract has been comprehensively explored to furnish insights for relieving food allergy symptoms and preventing food allergy.

Probiotics and Postbiotics as the Functional Food Components Affecting the Immune Response

The food market is one of the most innovative segments of the world economy. Recently, among consumers there is a forming trend of a healthier lifestyle and interest in functional foods. Products with positive health properties are a good source of nutrients for consumers' nutritional needs and reduce the risk of metabolic diseases such as diabetes, atherosclerosis, or obesity. They also seem to boost the immune system. One of the types of functional food is "probiotic products", which contain viable microorganisms with beneficial health properties. However, due to some technical difficulties in their development and marketing, a new alternative has started to be sought. Many scientific studies also point to the possibility of positive effects on human health, the so-called "postbiotics", the characteristic metabolites of the microbiome. Both immunobiotics and post-immunobiotics are the food components that affect the immune response in two ways: as inhibition (suppressing allergies and inflammation) or as an enhancement (providing host defenses against infection). This work's aim was to conduct a literature review of the possibilities of using probiotics and postbiotics as the functional food components affecting the immune response, with an emphasis on the most recently published works.

Bacillus subtilis Provides Long-Term Protection in a Murine Model of Allergic Lung Disease by Influencing Bacterial Composition

Probiotics are an attractive target for reducing the incidence of allergic disease. Bacillus subtilis is a gut-associated probiotic bacteria that can suppress allergic lung disease; however, it is not clear for how long this protection lasts. We exposed C57Bl/6 mice to B. subtilis via oral gavage and challenged them with intranasal house-dust mite for up to 8 weeks. We found that B. subtilis treatment was able to provide protection from eosinophil infiltration of the airways for 3 weeks. This loss of protection correlated with an increase in the eosinophil chemoattractant CCL24. Additionally, we demonstrate that B. subtilis treatment altered the bacterial composition by increasing the phylum Bacteroidetes and Verrucomicorbiota. The phylum Verrucomicorbiota was reduced in B. subtilis-treated mice at 8 weeks when protection was lost. These results support B. subtilis as a prophylactic for preventing the production of allergic lung disease and highlights that protection can last up to 3 weeks. This work also expands our understanding of how B. subtilis mediates protection and that in addition to modifying the immune system it is also altering the host microbiota.

Manipulating the microbiome to enhance oral tolerance in food allergy

Loss of oral tolerance (OT) to food antigens results in food allergies. One component of achieving OT is the symbiotic microorganisms living in the gut (microbiota). The composition of the microbiota can drive either pro-tolerogenic or pro-inflammatory responses against dietary antigens though interactions with the local immune cells within the gut. Products from bacterial fermentation, such as butyrate, are one of the main communication molecules involved in this interaction, however, this is released by a subset of bacterial species. Thus, strategies to specifically expand these bacteria with protolerogenic properties have been explored to complement oral immunotherapy in food allergy. These approaches either provide digestible biomolecules to induce beneficial bacteria species (prebiotics) or the direct administration of live bacteria species (probiotics). While this combined therapy has shown positive outcomes in clinical trials for cow's milk allergy, more research is needed to determine if this therapy can be extended to other food allergens.

The Impact of Escherichia coli Probiotic Strain O83:K24:H31 on the Maturation of Dendritic Cells and Immunoregulatory Functions In Vitro and In Vivo

Early postnatal events are important for the development of the neonatal immune system. Harboring the pioneering microorganisms forming the microbiota of the neonatal gastrointestinal tract is important for priming the immune system, as well as inducing appropriate tolerance to the relatively innocuous environmental antigens and compounds of normal healthy microbiota. Early postnatal supplementation of suitable, safe probiotics could accelerate this process. In the current study, the immunomodulatory capacity of the probiotic strain of Escherichia coli O83:K24:H31 (EcO83) was characterized in vitro and in vivo. We compared the capacity of EcO83 with and without hemolytic activity on selected immune characteristics in vitro as determined by flow cytometry and quantitative real-time PCR. Both strains with and without hemolytic activity exerted comparable capacity on the maturation of dendritic cells while preserving the induction of interleukin 10 (Il10) expression in dendritic cells and T cells cocultured with EcO83 primed dendritic cells. Early postnatal supplementation with EcO83 led to massive but transient colonization of the neonatal gastrointestinal tract, as detected by in vivo bioimaging. Early postnatal EcO83 administration promoted gut barrier function by increasing the expression of claudin and occludin and the expression of Il10. Early postnatal EcO83 application promotes maturation of the neonatal immune system and promotes immunoregulatory and gut barrier functions.

Pyruvate enhances oral tolerance via GPR31

CX3CR1 high myeloid cells in the small intestine mediate the induction of oral tolerance by driving regulatory T (Treg) cells. Bacterial metabolites, e.g., pyruvate and lactate, induce a dendrite extension of CX3CR1 high myeloid cells into the intestinal lumen via GPR31. However, it remains unclear whether the pyruvate-GPR31 axis is involved in the induction of oral tolerance. Here, we show that pyruvate enhances oral tolerance in a GPR31-dependent manner. In ovalbumin (OVA)-fed Gpr31-deficient mice, an OVA-induced delayed-type hypersensitivity response was substantially induced, demonstrating the defective induction of oral tolerance in Gpr31-deficient mice. The percentage of RORγt+ Treg cells in the small intestine was reduced in Gpr31-deficient mice. In pyruvate-treated wild-type mice, a low dose of OVA efficiently induced oral tolerance. IL-10 production from intestinal CX3CR1 high myeloid cells was increased by OVA ingestion in wild-type mice, but not in Gpr31-deficient mice. CX3CR1 high myeloid cell-specific IL-10-deficient mice showed a defective induction of oral tolerance to OVA and a decreased accumulation of OVA-specific Treg cells in the small intestine. These findings demonstrate that pyruvate enhances oral tolerance through a GPR31-dependent effect on intestinal CX3CR1 high myeloid cells.

Modulating oxidative stress counteracts specific antigen-induced regulatory T-cell apoptosis in mice

Treg are known to have a central role in orchestrating immune responses, but less is known about the destiny of Treg after being activated by specific Ags. This study aimed to investigate the role of superoxide dismutase, an active molecule in the regulation of oxidative stress in the body, in the prevention of Treg apoptosis induced by specific Ags. Ag-specific Tregs were isolated from the DO11.10 mouse intestine. A food allergy mouse model was developed with ovalbumin as the specific Ag and here, we observed that exposure to specific Ag induced Treg apoptosis through converting the precursor of TGF-β to its mature form inside the Tregs. Oxidative stress was induced in Tregs upon exposure to specific Ags, in which Smad3 bound the latency-associated peptide to induce its degradation, converting the TGF-β precursor to its mature form, TGF-β. Suppressing oxidative stress in Tregs alleviated the specific Ag-induced Treg apoptosis in in vitro experiments and suppressed experimental food allergy by preventing the specific Ag-induced Treg apoptosis in the intestine. In conclusion, exposure to specific Ags induces Treg apoptosis and it can be prevented by upregulating superoxide dismutase or suppressing reactive oxidative species in Tregs.

Role of orally induced regulatory T cells in immunotherapy and tolerance

Oral antigen administration to induce regulatory T cells (Treg) takes advantage of regulatory mechanisms that the gastrointestinal tract utilizes to promote unresponsiveness against food antigens or commensal microorganisms. Recently, antigen-based oral immunotherapies (OITs) have shown efficacy as treatment for food allergy and autoimmune diseases. Similarly, OITs appear to prevent anti-drug antibody responses in replacement therapy for genetic diseases. Intestinal epithelial cells and microbiota possibly condition dendritic cells (DC) toward a tolerogenic phenotype that induces Treg via expression of several mediators, e.g. IL-10, transforming growth factor-β, retinoic acid. Several factors, such as metabolites derived from microbiota or diet, impact the stability and expansion of these induced Treg, which include, but are not limited to, FoxP3⁺ Treg, LAP⁺ Treg, and/or Tr1 cells. Here, we review various orally induced Treg, their plasticity and cooperation between the Treg subsets, as well as underlying mechanisms controlling their induction and role in oral tolerance.

Immune boosting functional foods and their mechanisms: A critical evaluation of probiotics and prebiotics

Comprehensive studies conducted on the link between the gut microbiome and immunity in recent decades have correspondingly led to ever increasing interests in functional foods, especially probiotics and prebiotics. Probiotics and prebiotics play crucial roles in managing the intestinal microbiota in order to improve host health, even though their influence on other body sites are being investigated. Different colonic bacteria metabolize dietary prebiotics to produce beneficial metabolites, especially short chain fatty acids (SCFAs) that improve luminal contents and intestinal performance, while positively affecting overall host physiology. Thus, this review provides a general perspective of the immune system, the gut immune system and its microbiota. The review also evaluates functional foods with critical but comprehensive perspectives into probiotics and prebiotics, their immune boosting and mechanisms of action. It is recommended that further mechanistic and translational studies are conducted to promote health, social life and also empower poverty-stricken communities.

Plasmacytoid dendritic cells in the eye

Plasmacytoid dendritic cells (pDCs) are a unique subpopulation of immune cells, distinct from classical dendritic cells. pDCs are generated in the bone marrow and following development, they typically home to secondary lymphoid tissues. While peripheral tissues are generally devoid of pDCs during steady state, few tissues, including the lung, kidney, vagina, and in particular ocular tissues harbor resident pDCs. pDCs were originally appreciated for their potential to produce large quantities of type I interferons in viral immunity. Subsequent studies have now unraveled their pivotal role in mediating immune responses, in particular in the induction of tolerance. In this review, we summarize our current knowledge on pDCs in ocular tissues in both mice and humans, in particular in the cornea, limbus, conjunctiva, choroid, retina, and lacrimal gland. Further, we will review our current understanding on the significance of pDCs in ameliorating inflammatory responses during herpes simplex virus keratitis, sterile inflammation, and corneal transplantation. Moreover, we describe their novel and pivotal neuroprotective role, their key function in preserving corneal angiogenic privilege, as well as their potential application as a cell-based therapy for ocular diseases.

The Effects of Nutrition on the Gastrointestinal Microbiome of Cats and Dogs: Impact on Health and Disease

The gastrointestinal (GI) microbiome of cats and dogs is increasingly recognized as a metabolically active organ inextricably linked to pet health. Food serves as a substrate for the GI microbiome of cats and dogs and plays a significant role in defining the composition and metabolism of the GI microbiome. The microbiome, in turn, facilitates the host's nutrient digestion and the production of postbiotics, which are bacterially derived compounds that can influence pet health. Consequently, pet owners have a role in shaping the microbiome of cats and dogs through the food they choose to provide. Yet, a clear understanding of the impact these food choices have on the microbiome, and thus on the overall health of the pet, is lacking. Pet foods are formulated to contain the typical nutritional building blocks of carbohydrates, proteins, and fats, but increasingly include microbiome-targeted ingredients, such as prebiotics and probiotics. Each of these categories, as well as their relative proportions in food, can affect the composition and/or function of the microbiome. Accumulating evidence suggests that dietary components may impact not only GI disease, but also allergies, oral health, weight management, diabetes, and kidney disease through changes in the GI microbiome. Until recently, the focus of microbiome research was to characterize alterations in microbiome composition in disease states, while less research effort has been devoted to understanding how changes in nutrition can influence pet health by modifying the microbiome function. This review summarizes the impact of pet food nutritional components on the composition and function of the microbiome and examines evidence for the role of nutrition in impacting host health through the microbiome in a variety of disease states. Understanding how nutrition can modulate GI microbiome composition and function may reveal new avenues for enhancing the health and resilience of cats and dogs.

Secretome Analysis of Mouse Dendritic Cells Interacting with a Probiotic Strain of Lactobacillus gasseri

Probiotics play a key role in the modulation of the gut immune system in health and disease and their action is mediated by molecules exposed on the microorganism surface or secreted probiotic-derived factors. In particular, Lactobacillus gasseri OLL2809, a probiotic microorganism isolated from human feces, has the potential to modulate various immune responses. The dendritic cells (DCs) are considered the main players in orchestrating the immune response, and their contact with intestinal microbiota is crucial for the development and homeostasis of gut immunity. To gain a perspective on the molecular mechanisms involved in the maturation process of DCs and investigate factors that could modulate these processes, a differential proteomic analysis was performed on the secretome of immature DCs, mature DCs (mDCs, induced by lipopolysaccharide (LPS)), and immature DCs challenged with L. gasseri OLL2809 before treatment with LPS (LGmDCs). The maturation process of DCs was associated to profound changes in the protein secretome and probiotic pre-treatment led to a dramatic modulation of several secreted proteins of mDC, not only classical immune mediators (i.e., cytokines, complement factors, T cell Receptor ligands) but also proteins involved in the contractile and desmosome machineries. The latter data highlight a novel mechanism by which L. gasseri can modulate the maturation process of DCs, reinforcing the concept of a protective anti-inflammatory role ascribed to this probiotic strain.

The Role of Plasmacytoid Dendritic Cells in Gut Health

Plasmacytoid dendritic cells (pDCs) are a unique subset of cells with different functional characteristics compared to classical dendritic cells. The pDCs are critical for the production of type I IFN in response to microbial and self-nucleic acids. They have an important role for host defense against viral pathogen infections. In addition, pDCs have been well studied as a critical player for breaking tolerance to self-nucleic acids that induce autoimmune disorders such as systemic lupus erythematosus. However, pDCs have an immunoregulatory role in inducing the immune tolerance by generating Tregs and various regulatory mechanisms in mucosal tissues. Here, we summarize the recent studies of pDCs that focused on the functional characteristics of gut pDCs, including interactions with other immune cells in the gut. Furthermore, the dynamic role of gut pDCs will be investigated with respect to disease status including gut infection, inflammatory bowel disease, and cancers.

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

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

Immunomodulation by food: impact on gut immunity and immune cell function

Recent studies have revealed that various food components affect the immune response. These components act on various immune cells, and their effects are mediated through the intestinal immune system and, in some cases, the intestinal microbiota. In this review, we describe the immunomodulating effects of various food components, including probiotics, prebiotics, polysaccharides, vitamins, minerals, fatty acids, peptides, amino acids and polyphenols. Some of these components enhance immune responses, leading to host defense against infection, whereas others inhibit immune responses, thus suppressing allergy and inflammation.

Outstanding animal studies in allergy II. From atopic barrier and microbiome to allergen-specific immunotherapy

Purpose of review

Animal studies published within the past 18 months were assessed, focusing on innate and specific immunomodulation, providing knowledge of high translational relevance for human atopic and allergic diseases.

Recent findings

Allergic companion animals represent alternative models, but most studies were done in mice. Atopic dermatitis mouse models were refined by the utilization of cytokines like IL-23 and relevant skin allergens or enzymes. A novel IL-6 reporter mouse allows biomonitoring of inflammation. Both skin pH and the (transferable) microflora have a pivotal role in modulating the skin barrier. The microflora of the gastrointestinal mucosa maintains tolerance to dietary compounds and can be disturbed by antiacid drugs. A key mouse study evidenced that dust from Amish households, but not from Hutterites protected mice against asthma. In studies on subcutaneous and sublingual allergen-specific immunotherapy, much focus was given on delivery and adjuvants, using poly-lacto-co-glycolic particles, CpGs, probiotics or Vitamin D3. The epicutaneous and intralymphatic routes showed promising results in mice and horses in terms of prophylactic and therapeutic allergy treatment.

Summary

In atopic dermatitis, food allergies and asthma, environmental factors, together with the resident microflora and barrier status, decide on sensitization versus tolerance. Also allergen-specific immunotherapy operates with immunomodulatory principles.

Lactobacillus paracasei GMNL-32 exerts a therapeutic effect on cardiac abnormalities in NZB/W F1 mice

Systemic lupus erythematosus (SLE) is a disease that mostly affects women. Accelerated atherosclerosis is a high-risk factor associated with SLE patients. SLE associated with cardiovascular disease is one of the most important causes of death. In this study, we demonstrated that Lactobacillus paracasei GMNL-32 (GMNL-32), a probiotic species, exhibits anti-fibrosis and anti-apoptotic effects on the cardiac tissue of NZB/WF1 mice. Female NZB/W F1 mice, a well-known and commonly used lupus-prone mouse strain, were treated with or without GMNL-32 administration for 12 weeks. Oral administration of GMNL-32 to NZB/WF1 mice significantly increased the ventricular thickness when compared to that of NZB/WF1 mice. Administration of GMNL-32 significantly attenuated the cardiac cell apoptosis that was observed in exacerbate levels in the control NZB/WF1 mice. Further, the cellular morphology that was slightly distorted in the NZB/WF1 was effectively alleviated in the treatment group mice. In addition, GMNL-32 reduced the level of Fas death receptor-related pathway of apoptosis signaling and enhanced anti-apoptotic proteins. These results indicate that GMNL-32 exhibit an effective protective effect on cardiac cells of SLE mice. Thus, GMNL-32 may be a potential therapeutic strategy against SLE associated arthrosclerosis.