Oral tolerance: therapeutic implications for autoimmune diseases

The influence of gut-derived CD39 regulatory T cells in CNS demyelinating disease

There is considerable interest in trying to understand the importance of the gut microbiome in human diseases. The association between dysbiosis, an altered microbial composition, as related to human disease is being explored in the context of different autoimmune conditions, including multiple sclerosis (MS). Recent studies suggest that MS affects the composition of the gut microbiota by altering the relative abundances of specific bacteria and archaea species. Remarkably, some of the bacterial species shown reduced in the gut of MS patients are known to promote immunosuppressive regulatory T cells (Tregs). In MS, the function of a phenotype of Tregs that express CD39, an ectoenzyme involved in the catabolism of adenosine triphosphate as immunomodulatory cells, appears to be reduced. In this review, we discuss the involvement of the gut microbiota in the regulation of experimental models of central nervous system inflammatory demyelination and review the evidence that link the gut microbiome with MS. Further, we hypothesize that the gut microbiome is an essential organ for the control of tolerance in MS patients and a potential source for safer novel therapeutics.

IL-6 Inhibits Upregulation of Membrane-Bound TGF-β 1 on CD4+ T Cells and Blocking IL-6 Enhances Oral Tolerance

Oral administration of Ag induces regulatory T cells that express latent membrane-bound TGF-β (latency-associated peptide [LAP]) and have been shown to play an important role in the induction of oral tolerance. We developed an in vitro model to study modulation of LAP⁺ on CD4⁺ T cells. The combination of anti-CD3 mAb, anti-CD28 mAb, and recombinant IL-2 induced expression of LAP on naive CD4⁺ T cells, independent of Foxp3 or exogenous TGF-β. In vitro generated CD4⁺LAP⁺Foxp3^- T cells were suppressive in vitro, inhibiting proliferation of naive CD4⁺ T cells and IL-17A secretion by Th17 cells. Assessing the impact of different cytokines and neutralizing Abs against cytokines, we found that LAP induction was decreased in the presence of IL-6 and IL-21, and to a lesser extent by IL-4 and TNF-α. IL-6 abrogated the in vitro induction of CD4⁺LAP⁺ T cells by STAT3-dependent inhibition of Lrrc32 (glycoprotein A repetitions predominant [GARP]), the adapter protein that tethers TGF-β to the membrane. Oral tolerance induction was enhanced in mice lacking expression of IL-6R by CD4⁺ T cells and by treatment of wild-type mice with neutralizing anti-IL-6 mAb. These results suggest that proinflammatory cytokines interfere with oral tolerance induction and that blocking the IL-6 pathway is a potential strategy for enhancing oral tolerance in the setting of autoimmune and inflammatory diseases.

The epithelial barrier and immunoglobulin A system in allergy

Airway and intestinal epithelial layers represent first-line physical barriers, playing a key role in mucosal immunity. Barrier dysfunction, characterized by alterations such as disruption of cell-cell apical junctions and aberrant epithelial responses, probably constitutes early and key events for chronic immune responses to environmental antigens in the skin and in the gut. For instance, barrier dysfunction drives Th2 responses in atopic disorders or eosinophilic esophagitis. Such epithelial impairment is also a salient feature of allergic asthma and growing evidence indicates that barrier alterations probably play a driving role in this disease. IgA has been identified as the most abundant immunoglobulin in mucosa, where it acts as an active barrier through immune exclusion of inhaled or ingested antigens or pathogens. Historically, it has been thought to represent the serum factor underlying reaginic activity before IgE was discovered. Despite several studies about regulation and major functions of IgA at mucosal surfaces, its role in allergy remains largely unclear. This review aims at summarizing findings about epithelial functions and IgA biology that are relevant to allergy, and to integrate the emerging concepts and the recent developments in mucosal immunology, and how these could translate to clinical observations in allergy.

Inhibition of CDK9 as a therapeutic strategy for inflammatory arthritis

Rheumatoid arthritis is characterised by synovial inflammation and proliferation of fibroblast-like synoviocytes. The induction of apoptosis has long been proposed as a target for proliferative autoimmune diseases, and has further been shown to act as a successful treatment of experimental models of arthritis, such as collagen-induced arthritis. Here we examined the effects of specific oral small-molecule inhibitors of the transcription regulating cyclin-dependent kinase 9 on the development and progression of collagen-induced arthritis. DBA/1 mice were immunised with bovine collagen type II and treated orally with specific CDK9 inhibitors. The effects of CDK9 inhibition on RNA levels and protein expression, apoptosis induction, caspase activation and lymphocyte phenotype were further analysed. Mice showed a significant delay in disease onset and a reduction in disease severity following treatment with CDK9 inhibitors. Inhibiting CDK9 activity in peripheral blood mononuclear cells resulted in the loss of Mcl-1 expression at both the protein and RNA levels, along with a subsequent increase in apoptosis. CDK9 specific inhibitors may be a potential alternative treatment not only of cancer, but also for autoimmune- and inflammatory diseases. Taken together, these results show that transient inhibition of CDK9 induces apoptosis in leukocyte subsets and modulates the immune response.

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

Food allergy is a serious problem for infants and young children. Induction of antigen-specific oral tolerance is one therapeutic strategy. Enhancement of oral tolerance induction by diet is a promising strategy to prevent food allergy in infants. Thus, in this study, we evaluate the effect of probiotic Lactobacillus gasseri OLL2809 (LG2809) on oral tolerance induction in a mouse model. The degree of oral tolerance induction was evaluated by measuring the proliferation and level of IL-2 production of splenic CD4⁺ T cells from DO11.10 mice fed ovalbumin (OVA) alone or OVA with LG2809. Oral administration of LG2809 significantly decreased the rate of proliferation and IL-2 production by CD4⁺ T cells from OVA-fed mice. LG2809 increased a ratio of CD4⁺ T-cell population, producing high levels of IL-10 and having strong suppressive activity. Moreover, LG2809 increased a ratio of plasmacytoid dendritic cells (pDCs) among the lamina propria (LP) in small intestine. When used as antigen presenting cells to naïve CD4⁺ T cells from DO11.10 mice, LP cells from BALB/c mice fed LG2809 induced higher IL-10 production and stronger suppressive activity than those from non-treated mice. These results suggest that oral administration of LG2809 increases the population of pDCs in the LP, resulting in the enhancement of oral tolerance induction by increasing the ratio of effector regulatory T cells. LG2809 could, therefore, act as a potent immunomodulator to prevent food allergies by promoting oral tolerance.

Further understanding of the immunopathology of multiple sclerosis: impact on future treatments

INTRODUCTION

The understanding of the immunopathogenesis of multiple sclerosis (MS) has expanded with more research into T-cell subtypes, cytokine contributors, B-cell participation, mitochondrial dysfunction, and more. Treatment options have rapidly expanded with three relatively recent oral therapy alternatives entering the arena.

AREAS COVERED

In the following review, we discuss current mechanisms of immune dysregulation in MS, how they relate to current treatments, and the impact these findings will have on the future of therapy. Expert commentary: The efficacy of these medications and understanding their mechanisms of actions validates the immunopathogenic mechanisms thought to underlie MS. Further research has exposed new targets, while new promising therapies have shed light on new aspects into the pathophysiology of MS.

Oral Tolerance Induction in Experimental Autoimmune Encephalomyelitis with Candida utilis Expressing the Immunogenic MOG35-55 Peptide

Multiple sclerosis (MS) is an autoimmune disease that attacks myelinated axons in the central nervous system. Induction of oral tolerance is a potent mechanism to prevent autoimmunity. The food yeast Candida utilis was used to test the therapeutic potential of oral tolerance induction in an animal model of human multiple sclerosis (MS). We constructed a C. utilis strain, which displays a fusion peptide composed of the encephalitogenic MOG35-55 peptide and the C. utilis Gas1 cell wall protein on its surface.By immunizing mice with MOG35-55 peptide experimental autoimmune encephalomyelitis (EAE) was induced in a mouse model. Feeding of mice with C. utilis that expresses MOG35-55 peptide on its surface was started seven days prior to immunization and was continued for ten days. Control animals were treated with wild-type fungus or left untreated. Untreated mice developed first clinical symptoms ten days post immunization (p. i.) with an ascending paralysis reaching maximal clinical disability at day 18 to 20 p. i.. Treatment with the wild-type strain demonstrated comparable clinical symptoms. In contrast, oral gavage of MOG35-55-presenting fungus ameliorated the development of EAE. In addition, incidence as well as maximal clinical disease severity were significantly reduced. Interestingly, reduction of disease severity also occurred in animals treated with heat-inactivated C. utilis cells indicating that tolerance induction was independent of fungal viability. Better disease outcome correlated with reduced demyelination and cellular inflammation in the spinal cord, lower T cell proliferation against rechallenge with MOG35-55 and more regulatory T cells in the lymph nodes. Our data demonstrate successful that using the food approved fungus C. utilis presenting the immunogenic MOG35-55 peptide on its surface induced an oral tolerance against this epitope in EAE. Further studies will reveal the nature and extent of an anti-inflammatory environment established by the treatment that prevents the development of an autoimmune disorder affecting the CNS.

Feeding transgenic plants that express a tolerogenic fusion protein effectively protects against arthritis

Although much explored, oral tolerance for treatment of autoimmune diseases still awaits the establishment of novel and effective vectors. We investigated whether the tolerogenic CTA1(R7K)-COL-DD fusion protein can be expressed in edible plants, to induce oral tolerance and protect against arthritis. The fusion protein was recombinantly expressed in Arabidopsis thaliana plants, which were fed to H-2(q) -restricted DBA/1 mice to assess the preventive effect on collagen-induced arthritis (CIA). The treatment resulted in fewer mice exhibiting disease and arthritis scores were significantly reduced. Immune suppression was evident in treated mice, and serum biomarkers for inflammation as well as anticollagen IgG responses were reduced. In spleen and draining lymph nodes, CD4(+) T-cell responses were reduced. Concomitant with a reduced effector T-cell activity with lower IFNγ, IL-13 and IL-17A production, we observed an increase in IL-10 production to recall antigen stimulation in vitro, suggesting reduced Th1, Th2 and Th17 activity subsequent to up-regulated IL-10 and regulatory T-cell (Treg) functions. This study shows that edible plants expressing a tolerogen were effective at stimulating CD4 T-cell tolerance and in protecting against CIA disease. Our study conveys optimism as to the potential of using edible plants for oral treatment of rheumatoid arthritis.

Vitamin A Deficiency Impairs Induction of Oral Tolerance in Mice

Oral tolerance is a phenomenon of induction of systemic unresponsiveness to antigens ingested by the oral route and loss of immune response. Studies have shown the importance of vitamin A in oral tolerance in vitro but not in an in vivo experimental model. Therefore, we carried out experiments to determine how vitamin A deficiency affects tolerance induction and the ability of mesenteric lymph node (MLN) CD11c(+) cells to induce regulatory T cells (Tregs). Immunological tolerance was induced by oral ovalbumin (OVA) administration in vitamin A-sufficient mice. OVA-specific antibody and cytokine production were significantly reduced. On the other hand, in vitamin A-deficient mice, both OVA-specific antibody and cytokine production were not suppressed by oral OVA administration. Regarding induction of Tregs, the conversion rate of Foxp3(+) cells from naïve CD4(+) cell by CD11c(+) cells was decreased in vitamin A-deficient mice. Our study indicates that vitamin A deficiency causes the breakdown of oral tolerance in vivo.

Oral immune therapy: targeting the systemic immune system via the gut immune system for the treatment of inflammatory bowel disease

Inflammatory bowel diseases (IBD) are associated with an altered systemic immune response leading to inflammation-mediated damage to the gut and other organs. Oral immune therapy is a method of systemic immune modulation via alteration of the gut immune system. It uses the inherit ability of the innate system of the gut to redirect the systemic innate and adaptive immune responses. Oral immune therapy is an attractive clinical approach to treat autoimmune and inflammatory disorders. It can induce immune modulation without immune suppression, has minimal toxicity and is easily administered. Targeting the systemic immune system via the gut immune system can serve as an attractive novel therapeutic method for IBD. This review summarizes the current data and discusses several examples of oral immune therapeutic methods for using the gut immune system to generate signals to reset systemic immunity as a treatment for IBD.

The gut microbiome as a target for regulatory T cell-based immunotherapy: induction of regulatory lymphocytes by oral administration of anti-LPS enriched colostrum alleviates immune mediated colitis

Background

Gut-derived bacterial endotoxin is an important cofactor in the pathogenesis of IBD. Regulatory T cells (Tregs) are essential for maintenance of peripheral tolerance and can prevent and alleviate IBD. To determine the immune modulatory effect of anti-LPS enriched hyperimmune colostrum, its ability to induce Tregs and alleviate immune mediated colitis.

Methods

Immune-mediated colitis was induced in mice by intra-colonic instillation of Trinitrobenzene Sulfonate (TNBS). Four groups of mice were orally administered with two dosages of IgG-enriched colostrum fractions. The fractions were harvested from cows immunized against LPS derived from intestinal Escherichia coli bacteria (Imm124E). Control mice received non-immunized colostrum or vehicle (PBS). Treatment was administered one day following sensitization and four additional days following the administration of TNBS. The following parameters in the mice were tracked: body weight, bowel histology, serum cytokine levels and regulatory T cells.

Results

Oral administration of Imm124E hyperimmune colostrum ameliorated immune-mediated colitis. Significant amelioration of weight reduction was noted in treated mice. Oral administration of Imm124E improved bowel histology. Both the extent of the disease, inflammation score, and colitis damage and regeneration scores decreased in Imm-124E treated animals. These effects were associated with an increase in serum IL10 anti inflammatory cytokine levels, and an increase in CD4 + CD25+ and CD4 + Foxp3+ Tregs.

Conclusions

Oral administration of Imm124E promoted Tregs and alleviated bowel inflammation in immune mediated colitis. The present data suggests that the microbiome may serve as a target for Tregs-based immunotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-015-0388-x) contains supplementary material, which is available to authorized users.

Emerging immunopharmacological targets in multiple sclerosis

Inflammatory demyelination of the central nervous system (CNS) is the hallmark of multiple sclerosis (MS), a chronic debilitating disease that affects more than 2.5 million individuals worldwide. It has been widely accepted, although not proven, that the major pathogenic mechanism of MS involves myelin-reactive T cell activation in the periphery and migration into the CNS, which subsequently triggers an inflammatory cascade that leads to demyelination and axonal damage. Virtually all MS medications now in use target the immune system and prevent tissue damage by modulating neuroinflammatory processes. Although current therapies such as commonly prescribed disease-modifying medications decrease the relapse rate in relapsing-remitting MS (RRMS), the prevention of long-term accumulation of deficits remains a challenge. Medications used for progressive forms of MS also have limited efficacy. The need for therapies that are effective against disease progression continues to drive the search for novel pharmacological targets. In recent years, due to a better understanding of MS immunopathogenesis, new approaches have been introduced that more specifically target autoreactive immune cells and their products, thus increasing specificity and efficacy, while reducing potential side effects such as global immunosuppression. In this review we describe several immunopharmacological targets that are currently being explored for MS therapy.

Breast Milk and Solid Food Shaping Intestinal Immunity

After birth, the intestinal immune system enters a critical developmental stage, in which tolerogenic and pro-inflammatory cells emerge to contribute to the overall health of the host. The neonatal health is continuously challenged by microbial colonization and food intake, first in the form of breast milk or formula and later in the form of solid food. The microbiota and dietary compounds shape the newborn immune system, which acquires the ability to induce tolerance against innocuous antigens or induce pro-inflammatory immune responses against pathogens. Disruption of these homeostatic mechanisms might lead to undesired immune reactions, such as food allergies and inflammatory bowel disease. Hence, a proper education and maturation of the intestinal immune system is likely important to maintain life-long intestinal homeostasis. In this review, the most recent literature regarding the effects of dietary compounds in the development of the intestinal immune system are discussed.

Inflammatory Bowel Disease: An Overview of Immune Mechanisms and Biological Treatments

Inflammatory bowel diseases (IBD) are characterized by chronic inflammation of the intestinal tract associated with an imbalance of the intestinal microbiota. Crohn's disease (CD) and ulcerative colitis (UC) are the most widely known types of IBD and have been the focus of attention due to their increasing incidence. Recent studies have pointed out genes associated with IBD susceptibility that, together with environment factors, may contribute to the outcome of the disease. In ulcerative colitis, there are several therapies available, depending on the stage of the disease. Aminosalicylates, corticosteroids, and cyclosporine are used to treat mild, moderate, and severe disease, respectively. In Crohn's disease, drug choices are dependent on both location and behavior of the disease. Nowadays, advances in treatments for IBD have included biological therapies, based mainly on monoclonal antibodies or fusion proteins, such as anti-TNF drugs. Notwithstanding the high cost involved, these biological therapies show a high index of remission, enabling a significant reduction in cases of surgery and hospitalization. Furthermore, migration inhibitors and new cytokine blockers are also a promising alternative for treating patients with IBD. In this review, an analysis of literature data on biological treatments for IBD is approached, with the main focus on therapies based on emerging recombinant biomolecules.

Oral mixture of autologous colon-extracted proteins for the Crohn’s disease: A double-blind trial

AIM: To evaluate the safety and efficacy of oral administration of Alequel™, an autologous protein-containing colon extract.

METHODS: A total of 43 patients were enrolled in a randomized, placebo-controlled, double-blind trial. Patients were orally administered with autologous protein-containing colon extract three doses of autologous study drug per week for 15 wk, for a total of 45 doses. Patients were followed for safety parameters. Remission was defined as a Crohn’s disease activity index (CDAI) score of less than or equal to 150. All patients were followed for changes in subsets of T cells by fluorescence-activated cell sorting analysis.

RESULTS: Analysis was performed on a total number of evaluable patients of 14 in the study drug group and 15 in the placebo group. Treatment was well tolerated by all patients. No major treatment-related adverse events were reported or observed in any of the treated patients during the feeding or follow-up periods. Between weeks 6 and 9 of the study, six of the 14 (43%) evaluable subjects who received the study drug achieved a CDAI of 150 or lower. In contrast, five of the 15 (33%) evaluable subjects in the placebo group achieved remission. Between weeks 9 and 12, the remission rates were 50% and 33% for the drug group and placebo group, respectively. Among the drug-treated subjects who achieved remission, the effect of the drug was judged as stable in eight of the 14 subjects as measured by at least two CDAI scores indicating remission in the 15-wk treatment period. A decreased percentage of peripheral natural killer T regulatory cells (a decrease of 28% vs an increase of 16%) and an increased ratio of CD4⁺/CD8⁺ T lymphocytes (an increase of 11% vs a decrease of 9%) were noted in subjects with a significant clinical response.

CONCLUSION: Oral administration of the autologous colonic extract could be a safe and effective for the treatment of patients with moderate to severe Crohn’s disease.

The gut microbiome in autoimmunity: Sex matters

Autoimmune diseases like rheumatoid arthritis are multifactorial in nature, requiring both genetic and environmental factors for onset. Increased predisposition of females to a wide range of autoimmune diseases points to a gender bias in the multifactorial etiology of these disorders. However, the existing evidence to date has not provided any conclusive mechanism of gender-bias beyond the role of hormones and sex chromosomes. The gut microbiome, which impacts the innate and adaptive branches of immunity, not only influences the development of autoimmune disorders but may interact with sex-hormones to modulate disease progression and sex-bias. Here, we review the current information on gender bias in autoimmunity and discuss the potential of microbiome-derived biomarkers to help unravel the complex interplay between genes, environment and hormones in rheumatoid arthritis.

Tolerogenic modulation of the immune response by oligoglycerol- and polyglycerol-peptide conjugates

Peptide-based therapy is a promising strategy for antigen-specific immunosuppression to treat or even heal autoimmune diseases with significantly reduced adverse effects compared to conventional therapies. However, there has been no major success due to the drawbacks of native peptides, i.e., limited bioavailability. Considering the importance and limitations of peptide-based therapies for treatment of autoimmune diseases, we designed and constructed oligoglycerol (OG)- and polyglycerol (PG)-based peptide conjugates. They were evaluated for their biological activity (in vitro and in vivo), bioavailability, and tolerogenic potential. Among the OG- and PG-peptide constructs, PG-peptide constructs exhibited an extended bioavailability compared to OG-peptide constructs and unconjugated peptide. Interestingly, size, structure, and linker chemistry played a critical role for the tolerogenic capacity of the constructs. The PG-peptide construct bound via an ester linkage was the most tolerogenic conjugate, while the PG-peptide construct bound via an amide induced stronger proliferation, but also higher TNF production and lower frequencies of Foxp3(+) regulatory T-cells. Therefore, we conclude that PG-peptide conjugates bound via an ester linkage are not only promising candidates for tolerogenic vaccination, but also open a new avenue toward the application of peptides for the treatment of autoimmune diseases.

Epicutaneous Immunization with Collagen Induces TCRαβ Suppressor T Cells That Inhibit Collagen-Induced Arthritis

BACKGROUND

We have shown previously, in an animal model of multiple sclerosis and in TNBS-induced colitis, that epicutaneous (EC) immunization with protein antigen induces T suppressor cells that strongly inhibit the inflammatory response in contact hypersensitivity reactions.

METHODS

EC immunization was performed by applying to the shaved skin of the mouse dorsum a gauze patch soaked with a solution containing various amounts of type II collagen (COLL II) in a volume of 100 µl of PBS on days 0 and 4. On day 7 the patches were removed and mice were intradermally (i.d.) immunized with COLL II to induce collagen-induced arthritis (CIA).

RESULTS

Our study shows that EC immunization with 100 or 30 μg of COLL II reduces disease severity, whereas lower doses (10 or 3 μg) do not affect CIA. Decreased disease severity observed after EC immunization with COLL II correlates with reduced myeloperoxidase activity in joint tissue and with reduced production of anti-citrullinated protein and anti-COLL II IgG2a antibodies. Transfer experiments show that EC immunization with COLL II induces suppressor cells that belong to the population of TCRαβ lymphocytes and that EC-induced suppression declines with time. Both in vitro and in vivo experiments show that IL-17A plays an important role in EC-induced suppression of CIA. EC application of COLL II at the first signs of CIA also results in disease suppression.

CONCLUSIONS

The suppression of inflammatory responses by T suppressor cells induced through EC immunization of a protein antigen may become an attractive noninvasive therapeutic method for a variety of clinical situations.

Antigen administration by continuous feeding enhances oral tolerance and leads to long-lasting effects

The ability to avoid inflammatory responses to dietary components and microbiota antigens in the gut mucosa is achieved by a mechanism termed oral tolerance. This phenomenon is crucial to maintain the physiological immune activity in the gut and to prevent inflammatory disorders such as food allergy and inflammatory bowel diseases. Moreover, orally administered antigens induce regulatory cells that control systemic inflammatory responses as well. Given its specific, systemic and long-lasting effects, oral tolerance represents a promising approach for immunotherapies that aim to modulate inflammatory and autoimmune diseases. However, there are different protocols of feeding for induction of oral tolerance, and they have an impact in tolerance efficiency and length. Herein, we present and discuss different experimental feeding protocols and how they influence the outcome of oral administration of antigens.

Eggshell membrane hydrolyzates activate NF-κB in vitro: possible implications for in vivo efficacy

PURPOSE

Eggshell membrane (ESM) has been shown to contain naturally occurring bioactive components, and biological activities such as reducing proinflammatory cytokines, liver fibrosis, and joint pain in osteoarthritis sufferers have also been reported for ESM matrix as a whole. Nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) is a signaling protein found in the cytoplasm of nearly all human and animal cell types and is a primary regulator of immune function. The studies reported herein were designed to investigate the possible role that NF-κB activity might play in the reported biological activities of ESM.

METHODS

Three ESM hydrolyzates produced via fermentation, enzymatic, or chemical hydrolysis were evaluated in vitro in either human peripheral blood mononuclear cell or THP-1 (human leukemic monocyte) cell cultures for NF-κB activity following 4-hour exposure. The hydrolyzates were compared with untreated control cells or cells incubated with lipopolysaccharide or ascorbic acid. The source of ESM activity was also evaluated.

RESULTS

NF-κB levels were increased above levels found in untreated cells at all three dilutions (1:100, 1:1,000, and 1:10,000) for the fermentation hydrolyzate of ESM (ESM-FH) (P=0.021, P=0.020, P=0.009, respectively) in peripheral blood mononuclear cells. The enzymatic hydrolyzate of ESM (ESM-EH) also produced statistically significant levels of activated NF-κB at the 1:100 and 1:1,000 dilutions (P=0.004, P=0.006, respectively) but fell just shy of significance at the 1:10,000 dilution (P=0.073). Similarly, ESM-FH (P=0.021, P=0.002) and ESM-EH (P=0.007, P=0.007) activated NF-κB in THP-1 cells at 1:1,000 and 1:10,000 dilutions, respectively. The chemical hydrolyzate of ESM (ESM-CH) showed statistically significant levels of activation at the 1:1,000 dilution (P=0.005) but failed to differ from untreated cells at the 1:10,000 dilution (P=0.193) in THP-1 cells.

CONCLUSION

Results from our studies provide evidence that ESM hydrolyzates significantly activate NF-κB, and the source of this activity was investigated to confirm that it is inherent to ESM and not derived from bacterial contamination. Based on our findings, we propose a plausible hypothesis as to how increased NF-κB activity might translate into the in vivo efficacy that has been observed with ESM via an "oral tolerance" mechanism.

Intestinal mucosal tolerance and impact of gut microbiota to mucosal tolerance

The mucosal barriers are very sensitive to pathogenic infection, thereby assuming the capacity of the mucosal immune system to induce protective immunity to harmful antigens and tolerance against harmless substances. This review provides current information about mechanisms of induction of mucosal tolerance and about impact of gut microbiota to mucosal tolerance.

Immunological considerations in in utero hematopoetic stem cell transplantation (IUHCT)

In utero hematopoietic stem cell transplantation (IUHCT) is an attractive approach and a potentially curative surgery for several congenital hematopoietic diseases. In practice, this application has succeeded only in the context of Severe Combined Immunodeficiency Disorders. Here, we review potential immunological hurdles for the long-term establishment of chimerism and discuss relevant models and findings from both postnatal hematopoietic stem cell transplantation and IUHCT.

Gut microbiome and the risk factors in central nervous system autoimmunity

Humans are colonized after birth by microbial organisms that form a heterogeneous community, collectively termed microbiota. The genomic pool of this macro-community is named microbiome. The gut microbiota is essential for the complete development of the immune system, representing a binary network in which the microbiota interact with the host providing important immune and physiologic function and conversely the bacteria protect themselves from host immune defense. Alterations in the balance of the gut microbiome due to a combination of environmental and genetic factors can now be associated with detrimental or protective effects in experimental autoimmune diseases. These gut microbiome alterations can unbalance the gastrointestinal immune responses and influence distal effector sites leading to CNS disease including both demyelination and affective disorders. The current range of risk factors for MS includes genetic makeup and environmental elements. Of interest to this review is the consistency between this range of MS risk factors and the gut microbiome. We postulate that the gut microbiome serves as the niche where different MS risk factors merge, thereby influencing the disease process.

Thymic stromal lymphopoietin-mediated epicutaneous inflammation promotes acute diarrhea and anaphylaxis

Atopic dermatitis (AD) and food allergy are closely linked; however, the mechanisms that guide the progression of AD to allergic inflammatory responses at other mucosal surfaces, including the gastrointestinal tract, are not well understood. Here, we determined that exposure of mice that have been epicutaneously sensitized with thymic stromal lymphopoietin (TSLP) and antigen to repeated oral doses of the same antigen induced acute diarrhea and anaphylaxis. In this model, loss of TSLP signaling specifically in DCs led to loss of induced allergic diarrhea through lack of sensitization. While TSLP responses were not required during oral allergen challenge, CD4(+) T cells were required and transferred disease when introduced into naive hosts. In addition, oral exposure to the antigen prior to skin sensitization blocked development of allergic disease. Finally, mice lacking the receptor for IL-25 failed to develop acute diarrhea and anaphylaxis, highlighting a role for IL-25 in the initiation of type 2 immunity in the intestine. These results demonstrate a role for TSLP and IL-25 in the atopic march from skin sensitization to food allergic responses and provide a model system for the generation of potential therapeutic interventions.

Antigen-specific immunotherapeutic vaccine for experimental autoimmune myasthenia gravis

Myasthenia gravis (MG) and experimental autoimmune myasthenia gravis (EAMG) are caused by Ab-mediated autoimmune responses to muscle nicotinic acetylcholine receptors (AChRs) that impair neuromuscular transmission, thereby causing muscle weakness. Previously, we discovered that i.p. injection of a therapeutic vaccine consisting of bacterially expressed cytoplasmic domains of human AChR subunits reduced the development of chronic EAMG in rats. In this article, we show that immunization with the therapeutic vaccine in adjuvants does not induce EAMG and, thus, is safe. The potency and efficacy of the therapeutic vaccine were greatly increased by s.c. administration of repeated low doses in IFA. Onset of chronic EAMG could be prevented. Established chronic EAMG could be rapidly reversed, modeling therapy of chronic MG. Therapy reduced pathological Abs assayed by immune precipitation of a main immunogenic region chimera. Successfully treated rats exhibited long-term resistance to reinduction of EAMG, suggesting a lasting cure of MG. A long-term effect of therapy was to change the isotype of the pathogenic Ab response from IgG2b, which fixes complement, to IgG1, which does not. Prevention and reversal of chronic EAMG was not caused by the isotype switch, but the isotype switch may contribute to resistance to reinduction of EAMG. Immunization with AChR cytoplasmic domains in adjuvant is promising as a safe, Ag-specific, potent, effective, rapidly acting, and long-lasting therapeutic approach to MG.

Expression of regulatory T cells in jejunum, colon, and cervical and mesenteric lymph nodes of dogs naturally infected with Leishmania infantum

Using flow cytometry, we evaluated the frequencies of CD4(+) and CD8(+) T cells and Foxp3(+) regulatory T cells (Tregs) in mononuclear cells in the jejunum, colon, and cervical and mesenteric lymph nodes of dogs naturally infected with Leishmania infantum and in uninfected controls. All infected dogs showed chronic lymphadenitis and enteritis. Despite persistent parasite loads, no erosion or ulcers were evident in the epithelial mucosa. The colon harbored more parasites than the jejunum. Frequencies of total CD4(+), total Foxp3, and CD4(+) Foxp3(+) cells were higher in the jejunum than in the colon. Despite negative enzyme-linked immunosorbent assay (ELISA) serum results for cytokines, levels of interleukin-10 (IL-10), gamma interferon (IFN-γ), transforming growth factor beta (TGF-β), and tumor necrosis factor alpha (TNF-α) were higher in the jejunum than in the colon for infected dogs. However, IL-4 levels were higher in the colon than in the jejunum for infected dogs. There was no observed correlation between clinical signs and histopathological changes or immunological and parasitological findings in the gastrointestinal tract (GIT) of canines with visceral leishmaniasis. However, distinct segments of the GIT presented different immunological and parasitological responses. The jejunum showed a lower parasite load, with increased frequencies and expression of CD4, Foxp3, and CD8 receptors and IL-10, TGF-β, IFN-γ, and TNF-α cytokines. The colon showed a higher parasite load, with increasing expression of IL-4. Leishmania infantum infection increased expression of CD4, Foxp3, IL-10, TGF-β, IFN-γ, and TNF-α and reduced CD8 and IL-4 expression in both the jejunum and the colon.

Treatment of neuromyelitis optica: state-of-the-art and emerging therapies

Neuromyelitis optica (NMO) is an autoimmune disease of the CNS that is characterized by inflammatory demyelinating lesions in the spinal cord and optic nerve, potentially leading to paralysis and blindness. NMO can usually be distinguished from multiple sclerosis (MS) on the basis of seropositivity for IgG antibodies against the astrocytic water channel aquaporin-4 (AQP4). Differentiation from MS is crucial, because some MS treatments can exacerbate NMO. NMO pathogenesis involves AQP4-IgG antibody binding to astrocytic AQP4, which causes complement-dependent cytotoxicity and secondary inflammation with granulocyte and macrophage infiltration, blood-brain barrier disruption and oligodendrocyte injury. Current NMO treatments include general immunosuppressive agents, B-cell depletion, and plasma exchange. Therapeutic strategies targeting complement proteins, the IL-6 receptor, neutrophils, eosinophils and CD19--all initially developed for other indications--are under clinical evaluation for repurposing for NMO. Therapies in the preclinical phase include AQP4-blocking antibodies and AQP4-IgG enzymatic inactivation. Additional, albeit currently theoretical, treatment options include reduction of AQP4 expression, disruption of AQP4 orthogonal arrays, enhancement of complement inhibitor expression, restoration of the blood-brain barrier, and induction of immune tolerance. Despite the many therapeutic options in NMO, no controlled clinical trials in patients with this condition have been conducted to date.

Lung transplantation: chronic allograft dysfunction and establishing immune tolerance

Despite significant medical advances since the advent of lung transplantation, improvements in long-term survival have been largely unrealized. Chronic lung allograft dysfunction, in particular obliterative bronchiolitis, is the primary limiting factor. The predominant etiology of obliterative bronchiolitis involves the recipient's innate and adaptive immune response to the transplanted allograft. Current therapeutic strategies have failed to provide a definitive treatment paradigm to improve long-term outcomes. Inducing immune tolerance is an emerging therapeutic strategy that abrogates allograft rejection, avoids immunosuppression, and improves long-term graft function. The aim of this review is to discuss the key immunologic components of obliterative bronchiolitis, describe the state of establishing immune tolerance in transplantation, and highlight those strategies being evaluated in lung transplantation.

Towards a liquid self: how time, geography, and life experiences reshape the biological identity

The conceptualization of immunological self is amongst the most important theories of modern biology, representing a sort of theoretical guideline for experimental immunologists, in order to understand how host constituents are ignored by the immune system (IS). A consistent advancement in this field has been represented by the danger/damage theory and its subsequent refinements, which at present represents the most comprehensive conceptualization of immunological self. Here, we present the new hypothesis of "liquid self," which integrates and extends the danger/damage theory. The main novelty of the liquid self hypothesis lies in the full integration of the immune response mechanisms into the host body's ecosystems, i.e., in adding the temporal, as well as the geographical/evolutionary and environmental, dimensions, which we suggested to call "immunological biography." Our hypothesis takes into account the important biological changes occurring with time (age) in the IS (including immunosenescence and inflammaging), as well as changes in the organismal context related to nutrition, lifestyle, and geography (populations). We argue that such temporal and geographical dimensions impinge upon, and continuously reshape, the antigenicity of physical entities (molecules, cells, bacteria, viruses), making them switching between "self" and "non-self" states in a dynamical, "liquid" fashion. Particular attention is devoted to oral tolerance and gut microbiota, as well as to a new potential source of unexpected self epitopes produced by proteasome splicing. Finally, our framework allows the set up of a variety of testable predictions, the most straightforward suggesting that the immune responses to defined molecules representing potentials antigens will be quantitatively and qualitatively quite different according to the immuno-biographical background of the host.

Regulatory T-cell vaccination independent of auto-antigen

To date, efforts to treat autoimmune diseases have primarily focused on the disease symptoms rather than on the cause of the disease. In large part, this is attributed to not knowing the responsible auto-antigens (auto-Ags) for driving the self-reactivity coupled with the poor success of treating autoimmune diseases using oral tolerance methods. Nonetheless, if tolerogenic approaches or methods that stimulate regulatory T (T_reg) cells can be devised, these could subdue autoimmune diseases. To forward such efforts, our approach with colonization factor antigen I (CFA/I) fimbriae is to establish bystander immunity to ultimately drive the development of auto-Ag-specific T_reg cells. Using an attenuated Salmonella vaccine expressing CFA/I fimbriae, fimbriae-specific T_reg cells were induced without compromising the vaccine's capacity to protect against travelers' diarrhea or salmonellosis. By adapting the vaccine's anti-inflammatory properties, it was found that it could also dampen experimental inflammatory diseases resembling multiple sclerosis (MS) and rheumatoid arthritis. Because of this bystander effect, disease-specific T_reg cells are eventually induced to resolve disease. Interestingly, this same vaccine could elicit the required T_reg cell subset for each disease. For MS-like disease, conventional CD25⁺ T_reg cells are stimulated, but for arthritis CD39⁺ T_reg cells are induced instead. This review article will examine the potential of treating autoimmune diseases without having previous knowledge of the auto-Ag using an innocuous antigen to stimulate T_reg cells via the production of transforming growth factor-β and interleukin-10.

Oral combined therapy with probiotics and alloantigen induces B cell-dependent long-lasting specific tolerance

Allogeneic hematopietic stem cell transplantation (aHSCT) is widely used for the treatment of hematologic malignancies. Although aHSCT provides a good response against the malignant cells (graft-versus-leukemia [GVL]), it also leads to the development of graft-versus-host disease (GVHD), a severe disease with high mortality and morbidity rates. Therapy for GVHD is commonly based on nonspecific immunosupression of the transplanted recipient, resulting in the concomitant inhibition of the GVL effect. In this study, we propose an alternative approach to specifically suppress GVHD while sparing the GVL, based on oral treatment of transplant donors with recipient Ags, associated with the intake of probiotic Lactococcus lactis as tolerogenic adjuvant (combined therapy). We show that treatment of C57BL/6 donor mice with combined therapy before the transplant protects the recipients F1 (C57BL/6 × BAL/c) mice from clinical and pathological manifestations of disease, resulting in 100% survival rate. Importantly, the animals keep the immunological competence maintaining the GVL response as well as the response to third-party Ags. The protection is specific, long lasting and dependent on donor IL-10-sufficient B cells activity, which induces regulatory T cells in the host. These data suggest that combined therapy is a promising strategy for prevention of GVHD with preservation of GVL, opening new possibilities to treat human patients subjected to transplantation.

Cholera toxin breakdowns oral tolerance via activation of canonical NF-κB

The mechanisms of mucosal immunogenicity and adjuvanticity of bacterial exotoxins remains unknown. In this study, we investigated the role of the transcription factor nuclear factor-κB (NF-κB) in cholera toxin (CT)-induced alteration of oral tolerance. Feeding CT abrogated ovalbumin (OVA)-induced oral tolerance, as evaluated by OVA-specific serum antibody responses, and CD4(+) T cell proliferation. CT feeding activated canonical NF-κB (one heterodimer type, p50-p65) and mRNA expression of NF-κB-dependent proinflammatory cytokines in mesenteric lymph node (MLN) and Peyer's patch (PP) cells. CT no longer showed abrogation of oral tolerance in mice pretreated with p50 small interfering RNAs (siRNAs). ADP-ribosylation inhibitors inhibited CT-induced NF-κB activation. These data suggest that CT induces canonical NF-κB activation in intestinal lymphoid cells, which plays a key role in mucosal immunogenicity and adjuvanticity.

Modulation of the effects of lung immune response on bone marrow by oral antigen exposure

Allergic airway inflammation is attenuated by oral tolerization (oral exposure to allergen, followed by conventional sensitization and challenge with homologous antigen), which decreases airway allergen challenge-induced eosinophilic infiltration of the lungs and bone marrow eosinophilia. We examined its effects on bone marrow eosinophil and neutrophil production. Mice of wild type (BP-2, BALB/c, and C57BL/6) and mutant strains (lacking iNOS or CD95L) were given ovalbumin (OVA) or water (vehicle) orally and subsequently sensitized and challenged with OVA (OVA/OVA/OVA and H₂O/OVA/OVA groups, resp.). Anti-OVA IgG and IgE, bone marrow eosinophil and neutrophil numbers, and eosinophil and neutrophil production ex vivo were evaluated. T lymphocytes from OVA/OVA/OVA or control H₂O/OVA/OVA donors were transferred into naïve syngeneic recipients, which were subsequently sensitized/challenged with OVA. Alternatively, T lymphocytes were cocultured with bone marrow eosinophil precursors from histocompatible sensitized/challenged mice. OVA/OVA/OVA mice of the BP-2 and BALB/c strains showed, relative to H₂O/OVA/OVA controls, significantly decreased bone marrow eosinophil counts and ex vivo eosinopoiesis/neutropoiesis. Full effectiveness in vivo required sequential oral/subcutaneous/intranasal exposures to the same allergen. Transfer of splenic T lymphocytes from OVA/OVA/OVA donors to naive recipients prevented bone marrow eosinophilia and eosinopoiesis in response to recipient sensitization/challenge and supressed eosinopoiesis upon coculture with syngeneic bone marrow precursors from sensitized/challenged donors.

Regulatory T cell in stroke: a new paradigm for immune regulation

Stroke is a common, debilitating trauma that has an incompletely elucidated pathophysiology and lacks an effective therapy. FoxP3⁺CD25⁺CD4⁺ regulatory T cells (Tregs) suppress a variety of normal physiological and pathological immune responses via several pathways, such as inhibitory cytokine secretion, direct cytolysis induction, and antigen-presenting cell functional modulation. FoxP3⁺CD25⁺CD4⁺ Tregs are involved in a variety of central nervous system diseases and injuries, including axonal injury, neurodegenerative diseases, and stroke. Specifically, FoxP3⁺CD25⁺CD4⁺ Tregs exert neuroprotective effects in acute experimental stroke models. These beneficial effects, however, are difficult to elucidate. In this review, we summarized evidence of FoxP3⁺CD25⁺CD4⁺ Tregs as potentially important immunomodulators in stroke pathogenesis and highlight further investigations for possible immunotherapeutic strategies by modulating the quantity and/or functional effects of FoxP3⁺CD25⁺CD4⁺ Tregs in stroke patients.

Food components and the immune system: from tonic agents to allergens

The intestinal mucosa is the major site of contact with antigens, and it houses the largest lymphoid tissue in the body. In physiological conditions, microbiota and dietary antigens are the natural sources of stimulation for the gut-associated lymphoid tissues (GALT) and for the immune system as a whole. Germ-free models have provided some insights on the immunological role of gut antigens. However, most of the GALT is not located in the large intestine, where gut microbiota is prominent. It is concentrated in the small intestine where protein absorption takes place. In this review, we will address the involvement of food components in the development and the function of the immune system. Studies in mice have already shown that dietary proteins are critical elements for the developmental shift of the immature neonatal immune profile into a fully developed immune system. The immunological effects of other food components (such as vitamins and lipids) will also be addressed. Most of the cells in the GALT are activated and local pro-inflammatory mediators are abundant. Regulatory elements are known to provide a delicate yet robust balance that maintains gut homeostasis. Usually antigenic contact in the gut induces two major immune responses, oral tolerance and production of secretory IgA. However, under pathological conditions mucosal homeostasis is disturbed resulting in inflammatory reactions such as food hypersensitivity. Food allergy development depends on many factors such as genetic predisposition, biochemical features of allergens, and a growing array of environmental elements. Neuroimmune interactions are also implicated in food allergy and they are examples of the high complexity of the phenomenon. Recent findings on the gut circuits triggered by food components will be reviewed to show that, far beyond their role as nutrients, they are critical players in the operation of the immune system in health and disease.

Regulating the regulators in cancer-immunosuppression in multiple myeloma (MM)

An effective immune response requires a prompt but measured action against the pathological insult, to prevent over-zealous inflammatory-mediated tissue destruction. In cancer, defective or incompetent immune responses may paradoxically result in disease progression despite an immune attempt at elimination. Tumour-induced immunosuppression may not only result from soluble factors and altered antigenicity, but also from cellular-mediated tumour-induced immune evasion. Multiple myeloma (MM) is associated with both cellular and humoral immune deficiencies and increased T(Reg) cells. In vitro modelling has indicated that the tumour cells directly induce functional T(Reg) cells. In light of this recent evidence, it now seems that the most promising and synergistic approaches for cancer immunotherapy would involve specific anti-tumour immunity and simultaneous reduction of tumour-induced immune-regulation. This review sets out the basic understanding of the human immune response, its dysregulation in cancer and proposes how this knowledge may influence future treatment strategies to maximise the anti-tumour immune response.

Gut immune system and oral tolerance

Gut mucosal surfaces separate the external environment from the internal sterile environment and so represent a first line of defence system. This barrier faces environments rich in pathogens that have developed effective mechanisms for colonisation of epithelial surfaces and invasion of mucosal tissues, but also harmless antigens such as food, airborne antigens or commensal bacterial flora. The latter represent the vast majority of the encountered antigens and require an appropriate response characterised by either ignorance or active suppression. However, for the former, a robust immune response is needed. Mucosae have developed a complex immune system that is capable of mounting an immune response against pathogenic antigens, while maintaining the required ignorance or active suppression against non-pathogenic antigens. Taking advantage of this knowledge, strategies have been devised to induce oral tolerance to antigens involved in experimental autoimmune disease or human conditions. It is now known that oral tolerance induces the up-regulation and activation of T cells with regulatory properties, a subtype of CD4⁺ T cells whose function is to regulate functions of other T lymphocytes to avoid excessive immune activation. Amongst them, the Th3 cells (cells that express the latency-associated peptide on the surface and secrete transforming growth factor β, a cytokine with immunoregulatory properties) are especially relevant in the induction of oral tolerance. Orally fed antigens seek to generate these types of cells in the treatment of autoimmune diseases in experimental animals or human subjects.

Immune therapy for nonalcoholic steatohepatitis: are we there yet?

Metabolic syndrome, obesity, and nonalcoholic steatohepatitis are associated with a state of chronic inflammation. The immune system and the inflammatory cascade can be involved in the development of any of the above common conditions. This association raises the question of whether immune therapy can be used for the treatment of nonalcoholic steatohepatitis. Although immune therapy is not yet feasible for clinical use, here, we review some of the recent data on the potential role of the various arms of the immune system in the development of nonalcoholic steatohepatitis and several potential therapeutic targets.

Post-stroke immunodeficiency: effects of sensitization and tolerization to brain antigens

Acute onset of cerebrovascular diseases seems to be related to a number of immunological alternations. After the initial pro-inflammatory response to brain ischemia accompanied by systemic inflammatory response syndrome, stroke interferes with function of the innate and the adaptive immune cells, resulting in systemic immunosuppression. Although post-stroke immunodeficiency could predispose patients to life-threatening infections, it could potentially protect brain via reducing autoimmune reaction to the brain antigens. In this paper, we review current knowledge on the immunological alterations after brain ischemia, particularly effects of infection for stimulation of autoimmune response against brain antigens.

Antigen-based vs. systemic immunomodulation in type 1 diabetes: the pros and cons

In type 1 diabetic patients insulin-producing pancreatic β-cells are destroyed by an orchestrated immune process involving self-reactive auto-antigen-specific CD4⁺ and CD8⁺ T cells. Efforts to reverse or prevent this destructive immunological cascade have led to promising results in animal models, however, the transition to the clinic has yet been unsuccessful. In addition, current clinical studies lack reliable biomarkers to circumscribe end-point parameters and define therapeutic success. Here, we give a current overview of both antigen-specific and non-specific systemic immunomodulatory approaches with a focus on the therapies verified or under evaluation in a clinical setting. While both approaches have their advantages and disadvantages, rationally designed combination therapies may yield the highest therapeutic efficacy. In order for future strategies to be effective, new well-defined biomarkers need to be developed and the extrapolation process of dose, timing and frequency from in vivo models to patients needs to be carefully reconsidered.