Neonatal exposure to staphylococcal superantigen improves induction of oral tolerance in a mouse model of airway allergy

Oral tolerance to prevent anti-drug antibody formation in protein replacement therapies

Protein based therapeutics have successfully improved the quality of life for patients of monogenic disorders like hemophilia, Pompe and Fabry disease. However, a significant proportion of patients develop immune responses towards intravenously infused therapeutic protein, which can complicate or neutralize treatment and compromise patient safety. Strategies aimed at circumventing immune responses following therapeutic protein infusion can greatly improve therapeutic efficacy. In recent years, antigen-based oral tolerance induction has shown promising results in the prevention and treatment of autoimmune diseases, food allergies and can prevent anti-drug antibody formation to protein replacement therapies. Oral tolerance exploits regulatory mechanisms that are initiated in the gut associated lymphoid tissue (GALT) to promote active suppression of orally ingested antigen. In this review, we outline general perceptions and current knowledge about the mechanisms of oral tolerance, including tissue specific sites of tolerance induction and the cells involved, with emphasis on antigen presenting cells and regulatory T cells. We define several factors, such as cytokines and metabolites that impact the stability and expansion potential of these immune modulatory cells. We highlight preclinical studies that have been performed to induce oral tolerance to therapeutic proteins or enzymes for single gene disorders, such as hemophilia or Pompe disease. These studies mainly utilize a transgenic plant-based system for oral delivery of antigen in conjugation with fusion protein technology that favors the prevention of antigen degradation in the stomach while enhancing uptake in the small intestine by antigen presenting cells and regulatory T cell induction, thereby promoting antigen specific systemic tolerance.

Appendectomy, tonsillectomy, and risk for sarcoidosis - A hospital-based case-control study in Japan

BACKGROUND

The role of surgery in the onset of sarcoidosis is unclear. We investigated whether surgery is an internal environmental factor for sarcoidosis onset within the Japanese population.

METHODS

We enrolled 222 patients diagnosed with sarcoidosis (78 men, 144 women) who were admitted to our department between 1984 and 2012. We also enrolled 529 control subjects (251 men, 278 women), who were matched for sex, age at admission, and year of admission. Surgical history, family history, and smoking status were evaluated.

RESULTS

Multivariate analysis correlated history of appendectomy (OR, 1.55; 95% CI, 1.05-2.29) and tonsillectomy (OR, 2.79; 95% CI, 0.91-8.56) with the occurrence of sarcoidosis; other surgical procedures had no correlation. In women, appendectomy had a stronger association with sarcoidosis (OR, 1.69; 95% CI, 1.05-2.73), as opposed to that in men (OR, 1.39; 95% CI, 0.68-2.85). This association was greater in women aged ≥45 years than in those aged <45 years. There was a stronger correlation between tonsillectomy and sarcoidosis in women (OR, 3.30; 95% CI, 0.88-12.39), than in men (OR, 1.26; 95% CI, 0.10-16.52). ORs for sarcoidosis were 5.55 (95% CI, 2.02-15.27) and 0.97 (95% CI, 0.52-1.84) in women aged ≥45 years with a history of appendectomy at <20 years and ≥20 years, respectively, with the former being statistically significant.

CONCLUSIONS

Appendix and tonsil removal was associated with sarcoidosis onset, suggesting their potential protective role against sarcoidosis development. Further studies are needed to minimize possible confounding factors.

Functions of Exosomes and Microbial Extracellular Vesicles in Allergy and Contact and Delayed-Type Hypersensitivity

Extracellular vesicles, such as exosomes, are newly recognized intercellular conveyors of functional molecular mechanisms. Notably, they transfer RNAs and proteins between different cells that can then participate in the complex pathogenesis of allergic and related hypersensitivity responses and disease mechanisms, as described herein. This review highlights this important new appreciation of the in vivo participation of such extracellular vesicles in the interactions between allergy-mediating cells. We take into account paracrine epigenetic exchanges mediated by surrounding stromal cells and the endocrine receipt of exosomes from distant cells via the circulation. Exosomes are natural ancient nanoparticles of life. They are made by all cells and in some form by all species down to fungi and bacteria, and are present in all fluids. Besides a new focus on their role in the transmission of genetic regulation, exosome transfer of allergens was recently shown to induce allergic inflammation. Importantly, regulatory and tolerogenic exosomes can potently inhibit allergy and hypersensitivity responses, usually acting nonspecifically, but can also proceed in an antigen-specific manner due to the coating of the exosome surface with antibodies. Deep analysis of processes mediated by exosomes should result in the development of early diagnostic biomarkers, as well as allergen-specific, preventive and therapeutic strategies. These will likely significantly diminish the risks of current allergen-specific parenteral desensitization procedures, and of the use of systemic immunosuppressive drugs. Since extracellular vesicles are physiological, they can be fashioned for the specific delivery of therapeutic molecular instructions through easily tolerated, noninvasive routes, such as oral ingestion, nasal administration, and perhaps even inhalation.

TGF-β-mediated airway tolerance to allergens induced by peptide-based immunomodulatory mucosal vaccination

We sought to modulate mucosal immune responses using neonatal vaccination to avert the development of allergic airways disease (AAD). Pulmonary pathology in AAD is driven by T helper (TH)2 cytokines, in particular interleukin (IL)4 and IL13, the expression and actions of which are regulated by the transcription factor STAT6. We developed a peptide homolog of STAT6, STAT6-IP. Neonatal mice given, intranasally, STAT6-IP, in an effort to modulate de novo airways immune responses, developed tolerance following subsequent allergen sensitization, with either ovalbumin or ragweed allergens, as demonstrated by reduced TH2 cytokines and specific immunoglobulin (Ig)E and the significant increases in the latency-associated peptide (LAP)(+) T-regulatory (Treg) cell subset and expression of transforming growth factor (TGF)-β. This regulatory phenotype was transferrable by CD4(+) T cells or CD11c(+) dendritic cells (DCs) derived from STAT6-IP-vaccinated mice. Anti-TGF-β treatment during allergen sensitization, however, re-established the pro-inflammatory TH2 response. Thus, neonatal STAT6-IP vaccination induces prospective TGF-β-dependent tolerance to allergen and constitutes a novel highly effective immunomodulatory allergy prevention strategy.

Staphylococcal enterotoxins in the etiopathogenesis of mucosal autoimmunity within the gastrointestinal tract

The staphylococcal enterotoxins (SEs) are the products of Staphylococcus aureus and are recognized as the causative agents of classical food poisoning in humans following the consumption of contaminated food. While illness evoked by ingestion of the SE or its producer organism in tainted food are often self-limited, our current understanding regarding the evolution of S. aureus provokes the utmost concern. The organism and its associated toxins, has been implicated in a wide variety of disease states including infections of the skin, heart, sinuses, inflammatory gastrointestinal disease, toxic shock, and Sudden Infant Death Syndrome. The intricate relationship between the various subsets of immunocompetent T cells and accessory cells and the ingested material found within the gastrointestinal tract present daunting challenges to the maintenance of immunologic homeostasis. Dysregulation of the intricate balances within this environment has the potential for extreme consequences within the host, some of which are long-lived. The focus of this review is to evaluate the relevance of staphylococcal enterotoxin in the context of mucosal immunity, and the underlying mechanisms that contribute to the pathogenesis of gastrointestinal autoimmune disease.

The role of Staphylococcal enterotoxin A in achieving oral tolerance to myelin basic protein in adult mice

BACKGROUND

Oral tolerance is the biological process explaining the non-responsiveness of gut lymphoid tissue to intestinal content. Our study tested a new approach for the enhancement of oral tolerance to a multiple sclerosis-triggering auto-antigen-myelin basic protein, by its oral administration with the Staphylococcal enterotoxin A.

METHODS

Immune tolerance thus stimulated was assessed in adult BALB/c mice, by measuring different cytokines from the supernatant of mesenteric lymph nodes cells (IFN-γ, IL-4, IL-10, IL-17, and TGF-β), and in a SJL/E mouse model of experimental autoimmune encephalomyelitis, by evaluating the development of regulatory T cells in mesenteric lymph nodes and the clinical outcome of the intervention.

RESULTS

We obtained a significant rise in the levels of IL-10 and TGF-β compared with control and a significant decrease of IFN-γ, IL-4 (p < 0.05). Regulatory T cells were increased compared with control (p < 0.05). These results were attributable both to myelin basic protein and to Staphylococcal enterotoxin A. The clinical outcome of experimental autoimmune encephalomyelitis was influenced only by the administration of myelin basic protein.

CONCLUSION

In our experiment, Staphylococcal enterotoxin A enhanced the immune tolerance to myelin basic protein in the gut mucosa, but had no impact on the clinical evolution of experimental autoimmune encephalomyelitis.

Neonatal mucosal immune stimulation by microbial superantigen improves the tolerogenic capacity of CD103(+) dendritic cells

Food allergy represents failure to develop tolerance to dietary proteins. Food allergy has increased in prevalence in parallel with decreased exposure to microbes during infancy. In mice, neonatal peroral exposure to the strongly T cell stimulating superantigen staphylococcal enterotoxin A (SEA), enhances the capacity to develop oral tolerance to a novel antigen encountered in adult life. A population of antigen-presenting cells in the gut, the CD103(+) dendritic cells (DCs), is thought to be involved in oral tolerance development, as they convert naïve T cells into FoxP3(+) regulatory T cells (Treg). This function depends on their capacity to convert vitamin A to retinoic acid, carried out by the retinal aldehyde dehydrogenase (RALDH) enzyme. Here, newborn mice were treated with superantigen and DC function and tolerogenic capacity was examined at six weeks of age. We observed that, in mice fed superantigen neonatally, the CD11c(+) DCs had increased expression of RALDH and in vitro more efficiently induced expression Foxp3 expression to stimulated T cells. Further, these mice showed an accumulation of FoxP3(+) T cells in the small intestinal lamina propria and had a more Ag-specific FoxP3(+) T cells after oral tolerance induction in vivo. Moreover, the improved oral tolerance, as shown by increased protection from food allergy, was eradicated if the Vitamin A metabolism was inhibited. These observations contribute to the understanding of how a strong immune stimulation during the neonatal period influences the maturation of the immune system and suggests that such stimulation may reduce the risk of later allergy development.

Oral tolerance

The gut-associated lymphoid tissue is the largest immune organ in the body and is the primary route by which we are exposed to antigens. Tolerance induction is the default immune pathway in the gut, and the type of tolerance induced relates to the dose of antigen fed: anergy/deletion (high dose) or regulatory T-cell (Treg) induction (low dose). Conditioning of gut dendritic cells (DCs) by gut epithelial cells and the gut flora, which itself has a major influence on gut immunity, induces CD103(+) retinoic acid-dependent DC that induces Tregs. A number of Tregs are induced at mucosal surfaces. Th3 type Tregs are transforming growth factor-β dependent and express latency-associated peptide (LAP) on their surface and were discovered in the context of oral tolerance. Tr1 type Tregs (interleukin-10 dependent) are induced by nasal antigen and forkhead box protein 3(+) iTregs are induced by oral antigen and by oral administration of aryl hydrocarbon receptor ligands. Oral or nasal antigen ameliorates autoimmune and inflammatory diseases in animal models by inducing Tregs. Furthermore, anti-CD3 monoclonal antibody is active at mucosal surfaces and oral or nasal anti-CD3 monoclonal antibody induces LAP(+) Tregs that suppresses animal models (experimental autoimmune encephalitis, type 1 and type 2 diabetes, lupus, arthritis, atherosclerosis) and is being tested in humans. Although there is a large literature on treatment of animal models by mucosal tolerance and some positive results in humans, this approach has yet to be translated to the clinic. The successful translation will require defining responsive patient populations, validating biomarkers to measure immunologic effects, and using combination therapy and immune adjuvants to enhance Treg induction. A major avenue being investigated for the treatment of autoimmunity is the induction of Tregs and mucosal tolerance represents a non-toxic, physiologic approach to reach this goal.

The role of gut microbiota (commensal bacteria) and the mucosal barrier in the pathogenesis of inflammatory and autoimmune diseases and cancer: contribution of germ-free and gnotobiotic animal models of human diseases

Metagenomic approaches are currently being used to decipher the genome of the microbiota (microbiome), and, in parallel, functional studies are being performed to analyze the effects of the microbiota on the host. Gnotobiological methods are an indispensable tool for studying the consequences of bacterial colonization. Animals used as models of human diseases can be maintained in sterile conditions (isolators used for germ-free rearing) and specifically colonized with defined microbes (including non-cultivable commensal bacteria). The effects of the germ-free state or the effects of colonization on disease initiation and maintenance can be observed in these models. Using this approach we demonstrated direct involvement of components of the microbiota in chronic intestinal inflammation and development of colonic neoplasia (i.e., using models of human inflammatory bowel disease and colorectal carcinoma). In contrast, a protective effect of microbiota colonization was demonstrated for the development of autoimmune diabetes in non-obese diabetic (NOD) mice. Interestingly, the development of atherosclerosis in germ-free apolipoprotein E (ApoE)-deficient mice fed by a standard low-cholesterol diet is accelerated compared with conventionally reared animals. Mucosal induction of tolerance to allergen Bet v1 was not influenced by the presence or absence of microbiota. Identification of components of the microbiota and elucidation of the molecular mechanisms of their action in inducing pathological changes or exerting beneficial, disease-protective activities could aid in our ability to influence the composition of the microbiota and to find bacterial strains and components (e.g., probiotics and prebiotics) whose administration may aid in disease prevention and treatment.

Staphylococcal enterotoxin A: a candidate for the amplification of physiological immunoregulatory responses in the gut

Staphylococcal enterotoxin A (SEA) is one of the bacterial products tested for modulation of unwanted immune responses. Of all the staphylococcal enterotoxins, SEA is the most potent stimulator of T cells. When administered orally, SEA acts as a superantigen (SA), producing unspecific stimulation of intra-epithelial lymphocytes (IELs) in the intestinal mucosa. This stimulation results in amplification of the normal local immunologic responses, which are mainly regulatory. This amplification is based on increased local production of IFN-γ by IELs, which acts on the nearby enterocytes. As a result, the enterocytes produce large amounts of tolerosomes, cellular corpuscles which detach themselves from the basal poles of the enterocytes and contain antigenic peptides that are conditioned to be interpreted as tolerogenic by the gut immune system. Tolerosomes are physiologically produced as a response to dietary peptides; it is already known that enterocytes posses the molecular mechanisms for processing peptides in a similar manner to lymphocytes. The fate of tolerosomes is not precisely known, but it seems that they merge with intestinal dendritic cells, conveying to them the information that orally administered peptides must be interpreted as tolerogens. SEA can stimulate this mechanism, thus favoring the development of tolerance to peptides/proteins administered subsequently via the oral route. This characteristic of SEA might be useful in therapy for regulating immune responses. The present paper reviews the current status of research regarding the impact of SEA on the enteric immune system and its potential use in the treatment of allergic and autoimmune diseases.

Neonatal tolerance under breastfeeding influence

Diseases due to defect in tolerance induction such as allergy, celiac disease, or Type 1 Diabetes develop mostly in childhood indicating the necessity of early intervention for primary prevention. Epidemiological studies report that breastfeeding could protect from these diseases. However, data are controversial and the mechanisms unclear. Experimental data suggest that breastfeeding-induced protection might rely on tolerance induction as long as some criteria are fulfilled. Thus, the tolerogenic potential of breast milk would depend on maternal exposure to common environmental and dietary antigens and the efficiency of antigen transfer across mammary epithelium. Induction of tolerance upon breast milk-mediated antigen transfer will also depend on the presence of immunomodulatory factors in breast milk and of its impact on neonatal gut and immune system maturation. The better understanding of maternal influence on tolerance induction through breastfeeding should allow the development of new strategies to prevent immune-mediated diseases.

The systemic and pulmonary immune response to staphylococcal enterotoxins

In response to environmental cues the human pathogen Staphylococcus aureus synthesizes and releases proteinaceous enterotoxins. These enterotoxins are natural etiologic entities of severe food poisoning, toxic shock syndrome, and acute diseases. Staphylococcal enterotoxins are currently listed as Category B Bioterrorism Agents by the Center for Disease Control and Prevention. They are associated with respiratory illnesses, and may contribute to exacerbation of pulmonary disease. This likely stems from the ability of Staphylococcal enterotoxins to elicit powerful episodes of T cell stimulation resulting in release of pro-inflammatory cytokines. Here, we discuss the role of the immune system and potential mechanisms of disease initiation and progression.

Oral tolerance

Multiple mechanisms of tolerance are induced by oral antigen. Low doses favor active suppression, whereas higher doses favor clonal anergy/deletion. Oral antigen induces T-helper 2 [interleukin (IL)-4/IL-10] and Th3 [transforming growth factor (TGF)-beta] T cells plus CD4+CD25+ regulatory cells and latency-associated peptide+ T cells. Induction of oral tolerance is enhanced by IL-4, IL-10, anti-IL-12, TGF-beta, cholera toxin B subunit, Flt-3 ligand, and anti-CD40 ligand. Oral (and nasal) antigen administration suppresses animal models of autoimmune diseases including experimental autoimmune encephalitis, uveitis, thyroiditis, myasthenia, arthritis, and diabetes in the non-obese diabetic (NOD) mouse, plus non-autoimmune diseases such as asthma, atherosclerosis, graft rejection, allergy, colitis, stroke, and models of Alzheimer's disease. Oral tolerance has been tested in human autoimmune diseases including multiple sclerosis (MS), arthritis, uveitis, and diabetes and in allergy, contact sensitivity to dinitrochlorobenzene (DNCB), and nickel allergy. Although positive results have been observed in phase II trials, no effect was observed in phase III trials of CII in rheumatoid arthritis or oral myelin and glatiramer acetate (GA) in MS. Large placebo effects were observed, and new trials of oral GA are underway. Oral insulin has recently been shown to delay onset of diabetes in at-risk populations, and confirmatory trials of oral insulin are being planned. Mucosal tolerance is an attractive approach for treatment of autoimmune and inflammatory diseases because of lack of toxicity, ease of administration over time, and antigen-specific mechanisms of action. The successful application of oral tolerance for the treatment of human diseases will depend on dose, developing immune markers to assess immunologic effects, route (nasal versus oral), formulation, mucosal adjuvants, combination therapy, and early therapy.