Suppression of diabetes in nonobese diabetic mice by oral administration of porcine insulin

A cholera toxoid-insulin conjugate as an oral vaccine against spontaneous autoimmune diabetes

Mucosally induced immunological tolerance is an attractive strategy for preventing or treating illnesses resulting from untoward inflammatory immune reactions against self- or non-self-antigens. Oral administration of relevant autoantigens and allergens has been reported to delay or suppress onset of clinical disease in a number of experimental autoimmune and allergic disorders. However, the approach often requires repeated feeding of large amounts of tolerogens over long periods and is only partly effective in animals already systemically sensitized to the ingested antigen such as in animals already harboring autoreactive T cells, and thus presumably also in humans with an autoimmune disease. We have recently shown that oral administration of microgram amounts of antigen coupled to cholera toxin B subunit (CTB), can effectively suppress systemic T cell reactivity in naive as well as in immune animals. We now report that feeding small amounts (2-20 microg) of human insulin conjugated to CTB can effectively suppress beta cell destruction and clinical diabetes in adult nonobese diabetic (NOD) mice. The protective effect could be transferred by T cells from CTB-insulin-treated animals and was associated with reduced lesions of insulitis. Furthermore, adoptive co-transfer experiments involving injection of Thy-1,2 recipients with diabetogenic T cells from syngeneic mice and T cells from congenic Thy-1,1 mice fed with CTB-insulin demonstrated a selective recruitment of Thy-1,1 donor cells in the peripancreatic lymph nodes concomitant with reduced islet cell infiltration. These results suggest that protection against autoimmune diabetes can be achieved by feeding minute amounts of a pancreas islet cell autoantigen linked to CTB and appears to involve the selective migration and retention of protective T cells into lymphoid tissues draining the site of organ injury.

Autoimmunity and type I diabetes

Insulin-dependent diabetes mellitus (IDDM) is a T-cell-mediated autoimmune disease. The effector mechanisms essentially involve cytokine-mediated inflammation ultimately leading to beta-cell destruction. Several candidate autoantigens have been delineated for both the pathogenic T-cell response and the nonpathogenic antibody response used for disease prediction. Because of antigen spreading, it is not yet clear which of these antigens are involved in the triggering of the autoimmune response. In any case, this TH1 autoimmune response is amplified and perpetuated by an immune dysregulation involving TH2 cells. Both effector and regulatory mechanisms are placed under the tight control of major histocompatibility complex (MHC) and non-MHC genes. (Trends Endocrinol Metab 1997; 8:71-74). (c) 1997, Elsevier Science Inc.

Temporal discontinuities in progression of NOD autoimmune diabetes

Consideration of the pathophysiology of insulin-dependent diabetes mellitus in the nonobese diabetic (NOD) mouse can be viewed from a temporal perspective. We argue that there are discontinuous phases and each phase may reflect a phenotype educed by a particular set of genetic and epigenetic events. Therefore, temporal dissection may be a useful platform for causal dissection and we have set out this article as follows: 1. Introduction. 2. "Pre-time." a. Genetics. b. Parental effects. 3. Development of insulitis. a. Development of autoimmunity vs waning of or failure to establish tolerance. b. Importance of beta cell mass. c. Homing. 4. Onset of beta cell destruction. 5. Further Discussion.

Oral tolerance for the treatment of autoimmune diseases

Orally administered autoantigens suppress autoimmunity in animal models, including experimental allergic encephalomyelitis, collagen and adjuvant-induced arthritis, uveitis, and diabetes in the non-obese diabetic mouse. Low doses of oral antigen induce antigen-specific regulatory T-cells in the gut, which act by releasing inhibitory cytokines such as transforming growth factor-beta, interleukin-4, and interleukin-10 at the target organ. Thus, one can suppress inflammation at a target organ by orally administering an antigen derived from the site of inflammation, even if it is not the target of the autoimmune response. Initial human trials of orally administered antigen have shown positive findings in patients with multiple sclerosis and rheumatoid arthritis. A double-blind, placebo-controlled, phase III multi-center trial of oral myelin in 515 relapsing-remitting multiple sclerosis patients is in progress, as are phase II clinical trials investigating the oral administration of type II collagen in rheumatoid arthritis, S-antigen in uveitis, and insulin in type I diabetes.

Recent advances in the management of diabetes mellitus

The Diabetes Control and Complications Trial (DCCT) demonstrated that the improved control of blood glucose levels could delay or prevent long-term complications in patients with insulin dependent diabetes mellitus (IDDM). However, there are questions as to whether this degree of tight control is realistic in community settings. This review will cover new strategies for the management and prevention of IDDM.

Induction of autoimmune diabetes by oral administration of autoantigen

An antigen administered orally can induce immunological tolerance to a subsequent challenge with the same antigen. Evidence has been provided for the efficacy of this approach in the treatment of human autoimmune diseases such as rheumatoid arthritis and multiple sclerosis. However, oral administration of autoantigen in mice was found to induce a cytotoxic T lymphocyte response that could lead to the onset of autoimmune diabetes. Thus, feeding autoantigen can cause autoimmunity, which suggests that caution should be used when applying this approach to the treatment of human autoimmune diseases.

Aerosol insulin induces regulatory CD8 gamma delta T cells that prevent murine insulin-dependent diabetes

Cellular immune hyporesponsiveness can be induced by the presentation of soluble protein antigens to mucosal surfaces. Most studies of mucosa-mediated tolerance have used the oral route of antigen delivery and few have examined autoantigens in natural models of autoimmune disease. Insulin is an autoantigen in humans and nonobese diabetic (NOD) mice with insulin-dependent diabetes mellitus (IDDM). When we administered insulin aerosol to NOD mice after the onset of subclinical disease, pancreatic islet pathology and diabetes incidence were both significantly reduced. Insulin-treated mice had increased circulating antibodies to insulin, absent splenocyte proliferation to the major epitope, insulin B chain amino acids 9-23, which was associated with increased IL-4 and particularly IL-10 secretion, and reduced proliferation to glutamic acid decarboxylase, another islet autoantigen. The ability of splenocytes from insulin-treated mice to suppress the adoptive transfer of diabetes to nondiabetic mice by T cells of diabetic mice was shown to be caused by small numbers of CD8 gamma delta T cells. These findings reveal a novel mechanism for suppressing cell-mediated autoimmune disease. Induction of regulatory CD8 gamma delta T cells by aerosol insulin is a therapeutic strategy with implications for the prevention of human IDDM.

Experimental autoimmune uveitis: molecular mimicry and oral tolerance

Intraocular inflammatory disease or uveitis, which affects the uveal tract and the retina of the eyes in human, is the major cause of visual impairment. Experimental autoimmune uveitis (EAU) is a T-cell-mediated autoimmune disease directed against retinal proteins and has been studied in several mammalian species including subhuman primates as a model for human posterior uveitis. Autoimmune responses provoked by molecular mimicry occur when the nonself and host determinants are similar enough to cross-react yet different enough to break immunological tolerance, and is one of the proposed mechanisms for induction of autoimmune diseases. Therapeutic immunomodulatory strategies have been used to induce antigen-specific peripheral immune tolerance in animal models of T-cell-mediated autoimmune diseases by oral administration of autoantigens. Oral tolerance leads to unique mechanisms of tissue and disease-specific immunosuppression, which would circumvent the immunotherapeutic problem of multiple target tissue autoreactivity. Several groups have investigated the effects of delivering autoantigens across gastric mucosal surfaces. This review briefly discusses molecular mimicry and the mechanism of induction of oral tolerance with respect to immunopathogenesis of T-cell-mediated autoimmune disease in general and EAU in particular.

The presence of insulin-degrading enzyme in human ileal and colonic mucosal cells

The aim of this research is to characterize the presence of insulin-degrading enzyme in human colon and ileal mucosal cells. Biochemical studies, including the activity-pH profiles, the effects of enzyme inhibitors, immunoprecipitation and western blots, were conducted. The majority of insulin-degrading activity in colon mucosal cells was localized in the cytosol. In both colon and ileum, cytosolic insulin-degrading activities had a pH optimum at pH 7.5, and were extensively inhibited by each of N-ethylmaleimide, p-chloromercuribenzoate, and 1,10-phenanthroline, but were very weakly affected by each of leupeptin, chymostatin, diisopropyl phosphofluoridate and soybean trypsin inhibitor. In the colon and ileum, more than 93% and 96%, respectively, of cytosolic insulin-degrading activities were removed by the mouse monoclonal antibody to human RBC insulin-degrading enzyme, as compared with less than 20% by the normal mouse IgG for both tissues. Further, a western blot analysis revealed that a cytosolic protein of 110 kD, in both human colon and ileum, reacted with the monoclonal antibody to insulin-degrading enzyme. It is concluded that insulin-degrading enzyme is present in the cytosol of human colon and ileal mucosal cells.

Orally induced, peptide-specific gamma/delta TCR+ cells suppress experimental autoimmune uveitis

We investigated the role of gamma/delta TCR+ T cells in induction and suppression of the T cell-mediated disease experimental autoimmune uveitis. Disease induction was studied in Lewis rats perinatally depleted of alpha/beta or gamma/delta TCR+ subpopulations. Depletion of alpha/beta TCR+ cells completely abrogated disease, whereas treatment with anti-gamma/delta antibodies had no influence on onset or intensity of uveitis. However, adoptively transferred gamma/delta+ cells from orally tolerized rats could mediate suppression of uveitis in an antigen-specific fashion. Uveitis induced by a peptide derived from the uveitogenic retinal soluble antigen (S-Ag) was suppressed by gamma/delta+ cells from rats orally tolerized with the same peptide as well as HLA peptide B27PD. This disease ameliorating effect could also be observed when rats were fed with the HLA peptide before immunization with S-Ag peptide. Transfer of alpha/beta+ T cells from the same donors as well as gamma/delta+ or alpha/beta+ cells from animals fed with control peptide had no ameliorating effect.

A diet enriched in protein accelerates diabetes manifestation in NOD mice

Diet modifies the development of insulin-dependent diabetes mellitus in animals and in humans. We examined female non-obese-diabetic (NOD) mice, a diabetes-prone mouse strain with 70% spontaneous diabetes incidence and metabolic abnormalities in non-overtly diabetic litters. They were fed a diet containing 55% (n = 27) or 15% (n = 26) protein, respectively, after weaning. At an age of 30 weeks, non-diabetic NOD mice were submitted to an intravenous glucose tolerance test (0.5 g/kg body weight; blood samples were taken after 2, 4, 8, 10, 15, 20 and 30 min) and to perfusion of the pancreas (stimulation media were Krebs-Ringer-Hepes buffer with 5 mmol/l glucose, 30 mmol/l glucose and 5 mmol/l glucose plus 19 mmol/l arginine). Diabetic mice were removed from the experiment. Serum glucose concentration and body weight were monitored weekly. Food ingestion was checked at an age of 11 weeks. On average, the onset of diabetes was diagnosed in mice on a high-protein diet (19.7 +/- 1.3 weeks) 4 weeks earlier than in mice on a low-protein diet (23.5 +/- 1.1 weeks; P < 0.05). Non-diabetic NOD mice on a high-protein diet showed significantly better glucose tolerance (as determined by the glucose disappearance rate) and mean insulin secretion (at 30 mmol/l glucose). No difference in the serum glucose concentration between non-diabetic mice on the low-protein diet or high-protein diet could be proved. In non-diabetic mice on the high-protein diet the body weight and food ingestion exceeded those of mice on the low-protein diet (P < 0.05). High insulin secretion and glucose tolerance in non-diabetic mice may reflect the capacity of beta-cells to adapt; however, beta-cells tend to be destroyed under such circumstances. Thus, a high-protein diet promoted the onset of diabetes, but it did not increase significantly the incidence of the disease.

Using transgenic mouse models to dissect the pathogenesis of virus-induced autoimmune disorders of the islets of Langerhans and the central nervous system

Viruses have often been associated with autoimmune diseases. One mechanism by which self-destruction can be triggered is molecular mimicry. Many examples of cross-reactive immune responses between pathogens and self-antigens have been described. This review presents two transgenic models of autoimmune disease induced by a virus through activation of anti-self lymphocytes. Viral antigens are expressed as transgenes either in beta-cells of the pancreas or in the oligodendrocytes of the CNS. Infection by a virus encoding the same gene activated autoreactive T cells that cleared the viral infection, and as a consequence of transgene expression resulted in organ-specific autoimmune disease. In both transgenic mouse models, autoreactive lymphocytes that escaped thymic negative selection were present in the periphery. Several factors are described that play a role in the regulation of the self-reactive process precipitated by a viral infection. These include the quantity of activated autoreactive T cells, the affinity of these T cells, the number of memory T cells generated following primary infection, costimulation by accessory molecules, and the types and locations of cytokines produced. In addition, unique barriers exist in target tissues that prevent or suppress autoreactive responses and define to a large extent the outcome of disease. Restimulation of autoreactive memory lymphocytes may be required to bypass these barriers and enhance autoimmune disease. Therapy directed at modifying these factors can reduce and even prevent autoimmune disease after it has been initiated.

Induction of circulating myelin basic protein and proteolipid protein-specific transforming growth factor-beta1-secreting Th3 T cells by oral administration of myelin in multiple sclerosis patients

Oral administration of antigen is a long recognized method of inducing systemic immune tolerance. In animals with experimental autoimmune disease, a major mechanism of oral tolerance triggered by oral administration of antigen involves the induction of regulatory T cells that mediate active suppression by secreting the cytokine TGF-beta 1. Multiple sclerosis (MS) is a presumed T cell-mediated Th1 type autoimmune disease. Here, we investigated whether in MS patients oral myelin treatment, containing both myelin basic protein (MBP) and proteolipid protein (PLP), induced antigen specific MBP or PLP reactive T cells that either secreted IL4, TGF-beta1, or alternatively did Th1 type sensitization occur as measured by IFN-gamma secretion. Specifically, 4,860 short-term T cell lines were generated to either MBP, PLP, or tetanus toxoid (TT) from 34 relapsing-remitting MS patients: 17 orally treated with bovine myelin daily for a minimum of 2 yr as compared to 17 nontreated patients. We found a marked increase in the relative frequencies of both MBP and PLP specific TGF-beta1-secreting T cell lines in the myelin treated MS patients as compared to non-treated MS patients (MBP P < 0.001, PLP P < 0.003). In contrast, no change in the frequency of MBP or PLP specific IFN-gamma or TT specific TGF-beta1 secreting T cells were observed. These results suggest that the oral administration of antigens generates antigen specific TGF-beta1 secreting Th3 cells of presumed mucosal origin that represent a distinct lineage of T cells. Since antigen-specific TGF-beta1 secreting cells localize to the target organ and then suppress inflammation in the local microenvironment, oral tolerization with self antigens may provide a therapeutic approach for the treatment of cell-mediated autoimmune disease which does not depend upon knowledge of the antigen specificity of the original T cell clone triggering the autoimmune cascade.

Experimental granulomatous colitis in mice is abrogated by induction of TGF-beta-mediated oral tolerance

In previous studies we showed that a chronic colitis associated with a Th1 T cell response can be induced by the rectal administration of the haptenizing reagent 2,4,6-trinitrobenzene sulfonic acid (TNBS). We report here that oral administration of haptenized colonic proteins (HCP) before rectal administration of TNBS effectively suppresses the ability of the latter to induce colitis. This suppression (oral tolerance) appears to be due to the generation of mucosal T cells producing TGF-beta and Th2-type cytokines after oral HCP administration. Peyer's patch and lamina propria CD4+ T cells from HCP-fed animals stimulated with anti-CD3/anti-CD28 had a 5-10-fold increase in their production of TGF-beta and secreted increased amounts of IL-4 and IL-10 but lower levels of IFN-gamma in comparison to T cells from ovalbumin-fed control animals. In addition, the colons of HCP-fed mice showed strikingly increased TGF-beta but decreased IL-12 expression by immunohistochemical studies and isolated mononuclear cells from HCP-fed animals secreted less IL-12 heterodimer. Finally, and most importantly, the suppressive effect of orally administered HCP was abrogated by the concomitant systemic administration of anti-TGF-beta or rIL-12 suggesting a reciprocal relationship between IL-12 and TGF-beta on tolerance induction in TNBS-induced colitis. In parallel studies we demonstrated that TNBS-induced colitis can be transferred to naive recipient animals with purified CD4+ T cells from the colon of TNBS-treated animals and that such animals develop lethal pancolitis when exposed to very low doses of TNBS. Feeding of HCP suppressed this sensitivity to TNBS, indicating that oral feeding can suppress the response of pre-committed T cells in vivo. These studies suggest for the first time that TGF-beta production can abrogate experimental granulomatous colitis even after such colitis is established, and thus, that regulation of TGF-beta levels may have relevance to the treatment of human inflammatory bowel disease.

Prevention of antigen-induced arthritis in rats by oral administration of the inducing antigen

We investigated the effect of oral administration of methylated bovine serum albumin (mBSA) on antigen-induced arthritis (AIA) in rats that was induced by immunization with mBSA followed by the intra-articular injection of the same antigen. The results showed that the development of AIA was suppressed in a dose-dependent manner by orally given mBSA. The suppression of AIA was associated with decreases in the delayed type hypersensitivity to mBSA and also in the proliferative response of inguinal lymph node cells to the antigen in mBSA-fed animals. These results indicate that oral administration of an antigen is an effective way to suppress arthritis induced by the antigen and that oral tolerance to the antigen appears to be critically involved in the suppression of arthritis.

A pilot trial of oral type II collagen in the treatment of juvenile rheumatoid arthritis

OBJECTIVE

To evaluate the efficacy of oral chicken type II collagen (CCII) in the treatment of juvenile rheumatoid arthritis (JRA).

METHODS

Ten patients with active JRA were treated with CCII for 12 weeks. Efficacy parameters, which included swollen and tender joint count and score, grip strength, 50-foot walking time, duration of morning stiffness, and patient and physician global scores of disease severity, were assessed monthly.

RESULTS

All patients completed the full course of therapy. Eight patients had reductions in both swollen and tender joint counts after 3 months of CCII. The mean changes from baseline in swollen and tender joint counts for the 8 responders at the end of the study were -61% and -54%, respectively. Mean values for other efficacy parameters also showed improvement from baseline. There were no adverse events that were considered to be treatment related.

CONCLUSION

Oral CCII may be a safe and effective therapy for JRA, and its use in this disease warrants further investigation.

The effect of oral immunization on corneal allograft survival

The present study examined the potential of orally induced tolerance for preventing immunological rejection of corneal allografts. Orthotopic corneal allografts were transplanted from either C3H (MHC + multiple minor H-mismatched) or NZB (multiple minor H-mismatched only) donors to CB6F1 recipients on day 0. Tissue cultured corneal epithelial and endothelial cells from relevant donor strains were administered orally from day -14 to day -4 on a daily basis, The incidence of graft rejection, graft mean survival time (MST), and alloimmune responses, and the antigen specificity of induced tolerance were studied. Oral immunization induced a remarkable tolerance such that only 55% of the orally immunized hosts rejected their fully allogeneic corneal grafts (MST = 43 days) compared with 100% rejection (MST = 18 days) in normal controls. Likewise, rejection of MHC-matched, multiple minor H-mismatched corneal grafts fell from 80% in untreated controls to 36% in orally immunized hosts. Oral immunization was effective in desensitizing previously immunized hosts. Rejection of MHC-matched, multiple H minor-mismatched corneal allografts fell from 93% in preimmune, unfed hosts to 36% in preimmune, orally tolerized mice. Thus, oral immunization is a safe and effective method for desensitizing high-risk, preimmune hosts and promoting corneal allograft survival.

Viruses, cytokines, antigens, and autoimmunity

To explain the pathogenesis of autoimmunity, we hypothesize that following an infection the immune response spreads to tissue-specific autoantigens in genetically predisposed individuals eventually determining progression to disease. Molecular mimicry between viral and self antigens could, in some instances, initiate autoimmunity. Local elicitation of inflammatory cytokines following infection probably plays a pivotal role in determining loss of functional tolerance to self autoantigens and the destructive activation of autoreactive cells. We also describe the potential role of interleukin 10, a powerful B-cell activator, in increasing the efficiency of epitope recognition, that could well be crucial to the progression toward disease.

Strategies for preventing type I diabetes mellitus

Type I diabetes mellitus is a chronic autoimmune disease in which there is T cell-mediated destruction of the pancreatic beta cells. Susceptibility to the disease is determined by several genes, with HLA genes having the strongest effect. The onset of the disease is predictable, at least in the relatives of affected persons, using a combination of autoantibody measurements, intravenous glucose tolerance testing, and genetic typing. The disease may be preventable, and several large clinical trials are now underway to test whether interventions such as administering low-dose insulin or the use of nicotinamide can prevent the onset of diabetes in at-risk relatives.

Active suppression of diabetes after oral administration of insulin is determined by antigen dosage

We have previously demonstrated that feeding six-week-old female mice with 20 units of human insulin every 2 - 3 days for 15 or 30 days induced an active mechanism of suppression through the generation of regulatory T cells that reduced the number of successful diabetic transfers in irradiated NOD recipients. In the present study, we analyzed the effects of antigen dosage and the critical period of cell injection to obtain protection. The effects of the dose of insulin feeding were therefore compared during cotransfer experiments of 5 x 10(6) T cells from diabetic mice and 5 x 10(6) T cells from the spleen of mice receiving 10 units, 20 units, or 40 units of insulin or saline every 2 - 3 days for 15 days. Only T lymphocytes from mice fed with 20 units conferred active cellular protection during adoptive transfer with a significant delay in diabetes onset (p = 0.002). No significant difference was noticed during histological analysis of pancreatic glands, indicating tha insulitis was not prevented. However, mice receiving T lymphocytes from the 20 units of insulin-fed animals had a milder form of inflammation, with a significantly lower percentage of severely infiltrated islets. Injecting regulatory T cells 7 days and 14 days after iv injection of diabetogenic T cells did not modify the incidence curves of diabetes in the recipients, suggesting that cellular interactions and delay in cell trafficking were determinants. These results may have important clinical implications in humans. In conclusion, this study indicates the importance but also the limits of antigen therapy in type I diabetes. Antigen dosage is a critical element for active suppression. Such analysis is important to perform in humans before the initiation of a large-scale prevention trial in prediabetic individuals.

Protection of nonobese diabetic mice from diabetes by intranasal or subcutaneous administration of insulin peptide B-(9-23)

The observation that overt type I diabetes is often preceded by the appearance of insulin autoantibodies and the reports that prophylactic administration of insulin to biobreeding diabetes-prone (BB-DP) rats, nonobese diabetic (NOD) mice, and human subjects results in protection from diabetes suggest that an immune response to insulin is involved in the process of beta cell destruction. We have recently reported that islet-infiltrating cells isolated from NOD mice are enriched for insulin-specific T cells, that insulin-specific T cell clones are capable of adoptive transfer of diabetes, and that epitopes present on residues 9-23 of the B chain appear to be dominant in this spontaneous response. In the experiments described in this report, the epitope specificity of 312 independently isolated insulin-specific T cell clones was determined and B-(9-23) was found to be dominant, with 93% of the clones exhibiting specificity toward this peptide and the remainder to an epitope on residues 7-21 of the A chain. On the basis of these observations, the effect of either subcutaneous or intranasal administration of B-(9-23) on the incidence of diabetes in NOD mice was determined. The results presented here indicate that both subcutaneous and intranasal administration of B-(9-23) resulted in a marked delay in the onset and a decrease in the incidence of diabetes relative to mice given the control peptide, tetanus toxin-(830-843). This protective effect is associated with reduced T-cell proliferative response to B-(9-23) in B-(9-23)-treated mice.

Recombinant human transforming growth factor beta does not inhibit the effects of interleukin-1 beta on pancreatic islet cells

The macrophage-derived cytokine, interleukin-1 beta (IL-1 beta), has been implicated to play an important role in the autoimmune beta cell lesion of insulin-dependent diabetes mellitus (IDDM) because of its inhibition of insulin secretion, direct cytotoxicity, and alteration of islet cell antigen expression. Because transforming growth factor beta (TGF-beta) has been reported to inhibit IL-1 receptor expression in several lymphoid and progenitor cell lines, to induce IL-1 receptor antagonist protein (IRAP) production in human peripheral blood monocytes, and to antagonize several effects of inflammatory cytokines and because oral tolerance may be mediated in part by TGF-beta released by regulatory T lymphocytes, we investigated whether TGF-beta counteracted the effects of IL-1 beta on islet cells. Islets isolated from Sprague-Dawley rats were cultured with or without recombinant human IL-1 beta and TGF-beta. Accumulated insulin secretion, cytokine-induced cytotoxicity, and islet cell expression of glutamic acid decarboxylase 65 (GAD-65) and heat-shock protein 70 (HSP-70) were measured in this study. We found that (1) IL-1 beta at 50 and 100 pg/ml inhibited insulin secretion by 41.9 +/- 14.8 and 52.6 +/- 3.5% and induced cytotoxicity by 46.5 +/- 17.3 and 54.1 +/- 6.1%, respectively. IL-1 beta at 1000 pg/ml significantly increased HSP-70 expression and decreased GAD-65 expression. (2) TGF-beta at 0.1, 1, 10, and 40 ng/ml had no significant effect on insulin secretion and did not induce cytotoxicity, TGF-beta at 40 ng/ml had no effect on the expression of either HSP-70 or GAD-65. (3) In combination, TGF-beta at 1, 10, and 40 ng/ml did not antagonize the IL-1 beta (50 and 100 pg/ml)-induced inhibition of insulin secretion or cytotoxicity; TGF-beta (40 ng/ml) did not block the effects of IL-1 beta (1000 pg/ml) on HSP-70 or GAD-65 expression. In conclusion, recombinant human TGF-beta does not counteract these effects of recombinant human IL-1 beta on rat pancreatic islet cells.

Development of immune response to cow's milk proteins in infants receiving cow's milk or hydrolyzed formula

BACKGROUND

Development of humoral and cellular immune responses to orally administered antigens in human beings is poorly understood, although antigen administration has been suggested as a treatment for hypersensitivity disorders and autoimmune diseases.

OBJECTIVE

The purpose of the study was to investigate the development of systemic immune response in infants fed with formula containing whole cow's milk proteins or hydrolyzed formula containing casein peptides.

METHODS

In a double-blind trial, 10 infants received cow's milk-based formula, and 10 infants received a casein hydrolysate formula until the age of 9 months. Blood samples were taken at the ages of 6, 9, and 12 months. Cellular responses were assessed by proliferation assay of peripheral blood mononuclear cells to cow's milk proteins (beta-lactoglobulin, bovine serum albumin, and alpha-casein). Humoral responses to the same proteins were measured by ELISA for IgG antibodies.

RESULTS

Feeding infants with cow's milk-based formula induced systemic humoral and cellular responses to cow's milk proteins. T-cell response later declined, supporting the concept of oral tolerization. Exposure to cow's milk proteins after the age of 9 months resulted in depressed cellular and humoral responsiveness to these proteins.

CONCLUSION

Our results support the view that induction of oral tolerance in human beings is an age-dependent phenomenon.

Suppression of insulitis in non-obese diabetic (NOD) mice by oral insulin administration is associated with selective expression of interleukin-4 and -10, transforming growth factor-beta, and prostaglandin-E

Oral administration of autoantigens suppresses development of autoimmunity in several animal models, and is being tested in clinical trials in patients with autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. Non-obese diabetic (NOD) mice spontaneously develop insulin-dependent diabetes mellitus at 15 to 20 weeks of age, after mononuclear cell (MNC) infiltration of the pancreatic islets of Langerhans and destruction of insulin-producing beta cells. We have previously shown that oral administration of insulin suppresses insulitis and development of diabetes in the NOD mouse. Oral insulin has no metabolic effect on blood glucose. Oral insulin mediates its effect through a T cell-dependent mechanism as shown by adoptive transfer and T cell depletion experiments, but the mechanisms responsible have not been fully explored. We now report a serial analysis of the cells and cytokines associated with development of diabetes in NOD mice, and contrast this with the findings in animals fed equine insulin or a control protein (ovalbumin). Animals were fed 1 mg twice a week for 5 weeks, beginning at 5 weeks of age. Marked insulitis in naive or ovalbumin-fed NOD mice occurred at 10 weeks, at which time a dense peri-islet and intra-islet MNC infiltration was observed. Immunohistological studies using monoclonal antibodies showed that infiltrating MNC consisted mainly of CD4+ T cells ( > 75% of leukocytes) plus smaller numbers of macrophages and CD8+ T cells. These cells displayed evidence of immune activation with expression of receptors for interleukin-2 (IL-2R) plus Th1 cytokines; dense labeling for IFN-gamma and tumor necrosis factor-alpha, plus lesser amounts of IL-2, was observed. MNC lacked labeling for IL-4, IL-10, prostaglandin-E, or transforming growth factor-beta. By contrast, at 10 weeks, pancreatic tissues from NOD mice fed insulin showed considerably less insulitis, and the residual MNC, although still largely CD4+ T cells plus macrophages, showed dense labeling for IL-4, IL-10, prostaglandin-E, and transforming growth factor-beta and an absence of IL-2, IFN-gamma or tumor necrosis factor-alpha Taken together with our previous findings, these data indicate that oral administration of insulin affects the development of diabetes in NOD mice through the generation of cells that elaborate immunoregulatory cytokines within the target organ and shift the balance from a Th1 to a Th2 pattern of cytokine expression.

Analysis of transforming growth factor beta and other cytokines in autoimmune exocrinopathy (Sjögren's syndrome)

Cytokines play a major role in tissue destruction caused by autoimmune dysregulation. In Sjögren's syndrome (SS) patients, salivary glands are the target organs for autoimmune tissue damage. In the present study, reverse transcriptase-polymerase chain reaction (RT-PCR) was used to look for cytokine mRNA expressed in SS salivary glands. Focus score was used to determine the severity of the lesions. Cytokine production in supernatants of the salivary gland cell culture was measured by enzyme-linked immunosorbent assay (ELISA). Immunohistochemical staining was used to identify the local presence of transforming growth factor beta (TGF-beta). Interleukin (IL)-2, IL-6, and IL-10 mRNA were expressed in moderate to severe SS salivary gland lesions. TGF-beta mRNA was constitutively expressed in normal and SS salivary glands. In SS salivary gland cell cultures, IL-6 and IL-10 proteins were produced. TGF-beta production was reduced in high focus score SS glands. Normal and minimally involved SS salivary gland ductal epithelium and acinar cells were found to produce TGF-beta by immunostaining. In conclusion, an excess production of IL-2, IL-6, and IL-10 and a reduced production of the immunosuppressive cytokine, TGF-beta, may be responsible for the progression of the salivary gland lesion in SS. Specific immunotherapy can now be designed based on mechanisms to correct this cytokine imbalance and benefit patients with autoimmune diseases, such as SS.

Modulation of Antigen-Induced Arthritis in Rats by Oral Administration of Type I Interferon

We investigated the effect of oral administration of type I interferon (IFN) on antigen-induced arthritis (AIA) in rats that was induced by immunization with methylated bovine serum albumin (mBSA) followed by intraarticular injection of the antigen. When IFN was orally given before immunization, the severity of AIA was significantly suppressed. Oral IFN also downregulated both delayed type hypersensitivity and in vitro proliferative responses to mBSA. The serum from IFN-fed rats decreased joint inflammation as well as proliferation to mBSA. In contrast, in rats fed IFN after the onset of AIA, neither joint swelling nor the proliferation of T cells to mBSA was affected. Feeding IFN before, but not after immunization with mBSA was effective in suppressing the production of IL-2 by lymph node cells. These data suggest that IFN may be active by the oral route and have a preventive effect on antigen-driven inflammatory diseases that appears to be due the suppression of IL-2 production resulting in the downregulatin of the T cell activation.

Suppression of antigen-induced arthritis in Lewis rats by oral administration of type II collagen

OBJECTIVE

To assess the effect of orally administered type II collagen (CII) in antigen-induced arthritis (AIA).

METHODS

Arthritis was induced in Lewis rats by immunization with methylated bovine serum albumin (mBSA) in Freund's complete adjuvant, followed by an intraarticular injection of mBSA 2 weeks later. Different doses of CII, mBSA, and an unrelated control protein, keyhole limpet hemocyanin (KLH), were orally administered 5 times over several days prior to the induction of arthritis. Ankle joint swelling and delayed-type hypersensitivity (DTH) responses were measured.

RESULTS

Joint swelling was significantly reduced at a dose of 3 micrograms and 30 micrograms of CII, but not at 300 micrograms. The most prominent suppression of AIA was observed when rats were fed 10 mg of mBSA, whereas oral KLH had no effect. DTH responses were significantly reduced in the mBSA-fed rats, but not in rats that were fed CII or KLH.

CONCLUSION

Oral CII can suppress arthritis in an animal model in which immunity to collagen does not play a role. The effect is dose dependent and occurs at lower doses of CII. These results demonstrate the biologic relevance of bystander suppression associated with oral tolerance, and the potential use of this approach to treat human inflammatory joint disease.

Peripheral deletion of antigen-reactive T cells in oral tolerance

Oral administration of antigen is used to induce antigen-specific peripheral immune tolerance. As well as preventing systemic immune responses to ingested proteins, oral tolerance to autoantigens has also been used to suppress autoimmune diseases in animals and humans. Both active suppression and clonal anergy are suggested to be mechanisms of oral tolerance, depending on the dose of antigen fed. Here we report that oral antigen can delete antigen-reactive T cells in Peyer's patches, in mice transgenic for the ovalbumin-specific T-cell receptor genes. The deletion was mediated by apoptosis, and was dependent on dosage and frequency of feeding. At lower doses deletion was not observed; instead there was induction of antigen-specific cells that produced transforming growth factor (TGF)-beta and interleukin (IL)-4 and IL-10 cytokines. At higher doses, both Th1 and Th2 cells were deleted following their initial activation, whereas cells which secrete TGF-beta were resistant to deletion. These findings demonstrate that orally administered antigen can induce tolerance not only by active suppression and clonal anergy but by extrathymic deletion of antigen-reactive Th1 and Th2 cells.

Isohormonal therapy of endocrine autoimmunity

For most autoimmune disorders, the site (if any) of chronic immunization required for perpetuation of autoimmunity is unknown. However, one possible site is the target organ itself. If this were the case, feedback regulation of target cell activity might influence autoimmunity. Here, Nanette Schloot and George Eisenbarth review several recent studies suggesting that therapies that inhibit hormonal secretion of target endocrine organs, and/or modulate immunity by therapy with the isohormone, are associated with disease suppression.

Orally induced bystander suppression in experimental autoimmune uveoretinitis occurs only in the periphery and not in the eye

Oral administration of retinal soluble antigen (S-Ag) suppresses the induction of S-Ag-mediated experimental autoimmune uveitis (EAU) in Lewis rats. EAU induced with interphotoreceptor retinoid-binding protein (IRBP), another retinal autoantigen, can also be suppressed by oral administration of IRBP. It has been speculated that feeding with one retinal autoantigen could suppress induction of uveitis with the other retinal protein by means of bystander suppression. Both uveitogenic effector and suppressor cells should find their antigens within the retina, where the suppressor cells would be expected to act on the effector cells. However, reciprocal combinations of antigens used for induction and suppression of uveitis failed to prevent onset of disease, demonstrating that bystander suppression obviously does not occur in the eye. To investigate further the localization of suppressor mechanisms, we fed Lewis rats either with retinal S-Ag or with ovalbumin (OVA) and then immunized the animals either with a mixture of S-Ag and OVA or with each antigen separately, injected into contralateral hind legs. Feeding of S-Ag prior to immunization led to suppression of uveitis, whereas feeding of OVA had no tolerizing effect when S-Ag and OVA were injected into different legs. Nevertheless, immunizing rats with a mixture of S-Ag and OVA after OVA feeding suppressed uveitis to a high degree. These findings suggest that orally induced bystander suppression might not occur in the target organ, but rather peripherally at the site of induction of the autoimmune T cells.

Tolerance induction as a therapeutic strategy for the control of autoimmune endocrine disease in mouse models

This chapter aims to describe ways in which autoimmunity can be prevented or reversed and 'self-tolerance' re-established. To this end we have largely restricted our overview to the two main autoimmune disease models with which we are involved, i.e. IDDM in NOD mice and EAT in H-2k mice although, where appropriate and to demonstrate a particular point, other models are mentioned. The chapter has been divided into sections covering protection afforded by 1) transgenes, 2) autoantigen and 3) by reagents targetting T-cell surface molecules. Where established, the mechanism by which protection or tolerance is achieved is described but where, as in most cases, it is unknown the possibilities are discussed. Investigations using T-cell lines and clones and on islet regeneration which are currently being followed as part of a comprehensive approach to the study of autoimmunity are included as separate sections and their relevance discussed.

Anti-IL-10 treatment does not block either the induction or the maintenance of orally induced tolerance to OVA

Herein, the role of IL-10 in the induction and maintenance of oral tolerance was evaluated. The results show that: (1) mice treated with MoAb anti-IL-10 are permissive to the induction of oral tolerance to OVA; (2) anti-IL-10 treatment did not reverse the in vitro blocking of T cell proliferative response found in orally-tolerized mice; and (3) orally-induced tolerance could not be broken by anti-IL-10 treatment. Taken together, these results suggest that IL-10 is not a fundamental cytokine for the establishment and maintenance of oral tolerance.

Neonatal treatment of BB rats with sulphatide delays development of diabetes but does not change incidence

Sulphatide is a newly described autoantigen in insulin-dependent diabetes mellitus; it is present in the islets of Langerhans, and anti-sulphatide antibodies are found in diabetic patients and in spontaneously diabetic BB rats. The aim of the study was to treat neonatal BB rats with sulphatide in order to induce tolerance and thereby possibly influence later diabetes development. One hundred and twelve newborn BB rats, divided into three groups, were treated once daily during the first 6 days of life with intrathymic injections of sulphatide, galactosyl-ceramide (which is similar to sulphatide but without sulphate) or phosphate buffer alone. Although the results showed no difference in diabetes incidence among the three groups, there was a delayed onset of diabetes in the sulphatide-treated group, which developed diabetes on average at 77 +/- 1 days of age, compared to 70 +/- 2 days (p < 0.02) for the galactosyl-ceramide-treated group and 70 +/- 1 days (p < 0.01) for the buffer-treated group. The degree of insulitis and the size of islets of Langerhans were studied histologically for the diabetic animals in all three groups; there were no significant differences although the sulphatide-treated group tended to have a more normal histology. The blood glucose levels for the diabetic BB rats were similar in all three groups. Thus, neonatal treatment with the diabetic autoantigen sulphatide at the chosen dosage does not influence the incidence of diabetes, but delays the onset of disease.

Baclofen, a gamma-aminobutyric acid-b receptor agonist, delays diabetes onset in the non-obese diabetic mouse

Glutamic acid decarboxylase (GAD) is the enzyme responsible for the synthesis of gamma-aminobutyric acid (GABA). GAD has been identified as a 64-kDa antigen expressed in pancreatic beta-cells, to which autoantibodies are generated prior to the onset of type 1 (insulin-dependent) diabetes mellitus. GAD may therefore be an initiating factor in beta-cell destruction. We administered baclofen, a GABA-B receptor agonist, to non-obese diabetic (NOD) mice in an attempt to down-regulate GAD expression and thereby reduce the incidence of diabetes. Twenty-four female NOD mice were given baclofen in their drinking water at a final dose of 50 mg/kg body weight daily from weaning to 30 weeks of age. Twenty-four sex- and litter-matched mice were used as controls. At 30 weeks there was no difference in the incidence of diabetes in the treated group compared with the controls. However, there was a significant delay in the onset of diabetes in the treated group (P < 0.001, parallelism test). The degree of insulitis and the GAD activity in the pancreas per mg of protein were unchanged by baclofen treatment with respect to controls. These results suggest that baclofen may be effective in delaying diabetes onset in NOD mice by stimulating GABA activity, as this neurotransmitter, localised in the islets, may modulate insulin secretion and the antigen expression associated with it.

A review of the mechanisms of oral tolerance and immunotherapy

The induction of oral tolerance by oral immunization has been well recognized. Accumulated evidence shows that oral tolerance can be mediated by orally activated humoral and cellular factors. In animal models, the development of several T cell-mediated autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis, uveitis and diabetes type 1 can be inhibited by oral immunization of the respective antigens. In allergy, oral administration of certain allergens can prevent and reduce both contact and atopic dermatitis. Oral tolerance to alloantigen also reduces graft rejection. In spite of these encouraging results, the usefulness of this approach for an alternative immunotherapy in humans needs to be investigated further.

Therapeutic advances in immunosuppression

Immunosuppressive therapy is appropriate for the prevention or reversal of allograft rejection, and for the treatment of autoimmune disorders and allergic disease. Recent advances in our understanding of the cellular and molecular mechanisms that regulate immune responses have paralleled elucidation of the modes of action of a variety of therapeutic immunosuppressive agents, both 'old' and new. These developments have identified potential targets for more refined and specific intervention strategies that are now being tested in the clinic.