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

Comparative study of Oral versus Subcutaneous B:9-23 insulin peptide in Balb/c mice as an experimental model for Autoimmune Diabetes

Insulin peptide B:9-23 (amino acids 9 to 23 of the B chain) can induce immune targeting of insulin and islets in normal Balb/c mice. The insulin autoantibodies induced react with insulin and not the immunizing peptide. Oral administration of insulin as well as subcutaneous insulin can sensitize to insulin.

Oral Insulin Therapy to Prevent Progression of Immune-Mediated (Type 1) Diabetes

Repeated ingestion of insulin has been suggested as an immune tolerization therapy to prevent immune-mediated (type 1) diabetes. We performed a placebo-controlled, two-dose, oral insulin tolerance trial in newly diagnosed (< 2 years) diabetic patients who had required insulin replacement for less than 4 weeks and were found to have cytoplasmic islet cell autoantibodies (ICAs). No oral hypoglycemic agents were permitted during the trial. Endogenous insulin reserves were estimated at six-month intervals by plasma C-peptide responses to a mixed meal. Positive ICAs were found in 262 (31%) of the 846 patients screened. Of the 197 who agreed to participate, 187 could be followed for 6 to 36 months. Endogenous insulin retention was dependent upon initial stimulated C-peptide response, age at diabetes onset, and numbers of specific islet cell autoantibodies found. Oral insulin improved plasma C-peptide responses in patients diagnosed at ages greater than 20 years, best seen at the low (1 mg/day) over the high (10 mg/day) insulin dose (P = .003 and P = .01, respectively). In patients diagnosed before age 20 years, the 1 mg dose was ineffective, whereas the 10 mg dose actually accelerated C-peptide loss (P = .003). There were no adverse effects. If confirmed, these findings suggest that diabetic patients over age 20 years with ICA evidence of late-onset immune-mediated diabetes should be considered for oral insulin at 1 mg/day to better retain endogenous insulin secretion.

Mucosal tolerance to prevent type 1 diabetes: can the outcome be improved in humans?

The results of trials in which autoantigens have been fed to individuals affected by autoimmune diseases - multiple sclerosis, rheumatoid arthritis and type 1 diabetes - have been disappointing in terms of clinical improvement. This is in striking contrast to the results in experimental rodent models of these diseases. The outcome of the recent DPT-1 trial testing oral insulin in individuals at risk of type 1 diabetes was also disappointing, in contrast to the effects of oral insulin in the non-obese diabetic (NOD) mouse model of type 1 diabetes. However, it is premature to conclude that mucosal tolerance works only in in-bred rodents and not in humans with autoimmune disease. Except for oral insulin in DPT-1, the human trials were performed in individuals with end-stage disease when this form of immune regulation might not be expected to be effective. Importantly, in no trial was an immune response to the autoantigen documented, to demonstrate that the dose was at least bioavailable. Furthermore, mucosal autoantigen administration is a 'double-edged sword' and in rodents can lead not only to regulatory and protective immunity but also to pathogenic, tissue-destructive immunity and exacerbation of autoimmune disease. When suppression of autoimmune disease is observed it may be because autoantigen was administered under conditions which minimize induction of pathogenic immunity. Thus, clinical protocols for mucosal autoantigen administration may need to be modified to favor induction of regulatory immunity. In this short review, we discuss recent studies in autoimmune diabetes-prone NOD mice indicating that with novel modifications mucosal autoantigen administration could be harnessed to prevent type 1 diabetes in humans.

Specific antigen vaccination to treat autoimmune disease

Specific antigen vaccination by administration of the target antigen in aqueous solution has resulted in significant decreases of disease severity in animal models of experimental allergic encephalomyelitis, type I diabetes, and several forms of antigen-induced arthritis, even if administered after the initiation of symptoms. However, in experimental autoimmune encephalomyelitis (EAE) and type I diabetes in nonobese diabetic (NOD) mice, repeated administration of peptide fragments of target antigens in incomplete Freund's adjuvant has resulted in severe anaphylactic reactions. Although these methods of administration are known to potentiate CD4 T helper 2 (Th2) responses, which is the goal of specific antigen vaccination, the risk of anaphylaxis raises a red flag concerning use of this therapy for diseases such as type I diabetes, where the survival time after onset is quite long. It is clear that specific antigen vaccination is effective in preventing several animal models of autoimmune disease, and in treating these diseases once the symptoms are overt. However, the risks of this therapy require serious consideration of alternative methods for down-regulation of the autoimmune process.

Recessive tolerance to preproinsulin 2 reduces but does not abolish type 1 diabetes

Although autoimmune diseases can be initiated by immunization with a single antigen, it is not clear whether a single self antigen is essential for the initiation and, perhaps, the perpetuation of spontaneous autoimmunity. Some studies have suggested that insulin may represent an essential autoantigen in type 1 diabetes. Here we show that unlike tolerance to glutamic acid decarboxylase, tolerance to transgenically overexpressed preproinsulin 2 substantially reduced the onset and severity of type 1 diabetes in nonobese diabetic mice. However, some mice still developed type 1 diabetes, suggesting that insulin is a key, but not absolutely essential, autoantigen. The results are consistent with the idea that the human IDDM2 locus controls susceptibility to type 1 diabetes by regulating intrathymic preproinsulin expression.

Regulatory T cells and type 1 diabetes

A resurgent interest in T cells with regulatory activity has prompted many recent investigations into their potential role in pathogenesis and prevention of type 1 diabetes. While some studies have suggested that regulatory T cells participate in the preservation of active tolerance to autoantigens, findings obtained in multiple animal models for type 1 diabetes have documented the therapeutic induction of protective regulatory T cells. A review of the proposed mechanisms operative in regulatory T cell-mediated diabetes prevention indicates a common theme of localized regulatory T cell activation and subsequent suppression of pathogenic T cell trafficking, differentiation, and/or effector function. However, adaptation of experimental protocols for regulatory T cell induction to clinical applications faces several challenges. Immunization with self-antigens carries obvious risks especially in the face of multiple variables that can affect generation, trafficking, and regulatory activity of autoantigen-specific T cells. We also emphasize that the frequent use of lymphopenic recipients of adoptively transferred pathogenic and regulatory T cells constitutes a potentially confounding variable that further complicates translation into clinical settings. The therapeutic induction of regulatory T cells in prediabetic individuals carries great potential but is currently limited by the risks associated with deliberate generation of autoimmune responses that may exacerbate rather than ameliorate the autoimmune process. However, in vitro amplification and autologous regulatory T cell therapy might soon become a clinical reality.

Autoimmune diabetes: ongoing development of immunological intervention strategies targeted directly against autoreactive T cells

It is well known that autoimmunity associated with the onset of insulin-dependent diabetes mellitus (IDDM) involves the generation of autoreactive T and B cells. The findings that diabetics mount humoral and cellular immune responses against islet cell antigens (ICAs) have led to the testing of ICAs and their analogs as candidates for therapeutic agents for better treatment of IDDM at its prediabetic and diabetic stages. Apart from this type of approach, various immunological intervention strategies aimed at direct targeting of the autoreactive T cells have also been investigated. The present review covers the ongoing aspects of these developments focusing on the preclinical findings made in NOD (nonobese diabetic) mice which have been commonly used as a disease model for human autoimmune diabetes. Other types of approaches involving the mobilization of regulatory T cells to indirectly control or modulate the pathological activity of autoreactive T cells will not be discussed within this scope.

Induction of oral tolerance to prevent diabetes with transgenic plants requires glutamic acid decarboxylase (GAD) and IL-4

Induction of specific immunological unresponsiveness by feeding protein antigens is termed oral tolerance and may be a potential therapy for autoimmune diseases. Whereas oral tolerance therapy may be both simple and effective, the requirement for large amounts of protein will limit clinical testing of autoantigens, which are difficult to produce. We have previously demonstrated transgenic plant production and direct oral delivery of a beta cell autoantigen murine GAD67 to prevent autoimmune diabetes in nonobese diabetic mice. Mucosal adjuvants such as cholera toxin B subunit may lower the level of autoantigen required, but the development of neutralizing mucosal antibody responses may limit usefulness in enhancing long-term oral tolerance. IL-4, being an endogenous protein, would avoid this result and possibly enhance oral tolerance but has not been tested as a mucosal adjuvant. In this study, human GAD65 (hGAD65), as well as murine IL-4, was expressed in transgenic plants for feeding trials. Both IL-4 and hGAD65 plant tissue were required to protect nonobese diabetic mice from diabetes, and no benefit was found if either was used alone. Combined therapy enhanced levels of IgG1 anti-GAD antibodies, increased splenocyte IL-4/IFN-gamma cytokine responses, and produced protective regulatory T cells. These results demonstrate that orally administered plant IL-4 remains biologically active and is synergistic when given with hGAD65 in inducing robust oral immune tolerance. Using transgenic plants expressing IL-4 and GAD65 may be a novel clinical approach to the prevention of human type 1 diabetes by oral tolerance.

T-cell epitopes in type 1 diabetes

Type 1 diabetes (TID) results from T-cell-mediated destruction of pancreatic b cells in genetically predisposed individuals. Autoreactive CD4(+) T helper cells and CD8(+) cytotoxic T lymphocytes (CTLs) recognize b-cell-derived peptides in the context of major histocompatibility complex class II and I molecules, respectively, in a process that terminates in b-cell death. Many peptide epitopes derived from b-cell proteins have been described for both humans and the nonobese diabetic (NOD) mouse, but their relative importance in disease pathogenesis is unclear. The significance of identifying key b-cell epitopes is underscored by a study showing that in the NOD mouse monitoring of a single population of b-cell-specific CTLs in the peripheral blood using a high-avidity analogue of the endogenous peptide may be used to accurately predict diabetes occurrence. Future studies focused on the discovery of immunodominant b-cell epitopes and their high-avidity analogues should have considerable implications for prediction and immunotherapy of TID.

Systemic administration of IL-18 promotes diabetes development in young nonobese diabetic mice

IL-18 is now identified as a pleiotropic cytokine that acts as a cofactor for both Th1 and Th2 cell development. Type 1 diabetes is considered a Th1-type autoimmune disease, and to date, the suppressive effect of exogenous IL-18 on the development of diabetes has been reported in 10-wk-old nonobese diabetic (NOD) mice. In the present study we administered exogenous IL-18 systemically in 4-wk-old NOD mice using i.m. injection of the IL-18 expression plasmid DNA (pCAGGS-IL-18) with electroporation. Contrary to previous reports, the incidence of diabetes development was significantly increased in NOD mice injected with pCAGGS-IL-18 compared with that in control mice. Systemic and pancreatic cytokine profiles deviated to a Th1-dominant state, and the the frequency of glutamic acid decarboxylase-reactive IFN-gamma-producing CD4(+) cells was also high in the IL-18 group. Moreover, it was suggested that the promoting effect of IL-18 might be associated with increased peripheral IL-12, CD86, and pancreatic IFN-inducible protein-10 mRNA expression levels. In conclusion, we demonstrate here that IL-18 plays a promoting role as an enhancer of Th1-type immune responses in diabetes development early in the spontaneous disease process, which may contribute to elucidating the pathogenesis of type 1 diabetes.

Absence of the T-bet gene coding for the Th1-related transcription factor does not affect diabetes-associated phenotypes in Balb/c mice

The T-box expressed in T cells gene (T-bet) is a member of the T-box family of transcription factors. T-bet-deficient mice show normal lymphoid development, but exhibit profound defects in their Th1-mediated immune responses. As the balance between Th1- and Th2-mediated immune responses plays a role in autoimmune-prone diseases, we have investigated the diabetes-related insulin autoantibody (IAA) and cellular immune responses (insulitis), in the absence of Th1 lineage commitment, in T-bet KO Balb/c mice, after immunization with the B9-23 insulin peptide. We have therefore investigated whether absence of the T-bet gene influences diabetes-related phenotypes in Balb/c T-bet KO mice.

Multicenter prevention trial of slowly progressive type 1 diabetes with small dose of insulin (the Tokyo study): preliminary report

In 1996, we designed a randomized multicenter study to assess the effects of small doses of insulin on beta cell failure in slowly progressive type 1 diabetes (the Tokyo Study). We report here the preliminary results of this study. Glutamic acid decarboxylase 65 antibody (GADA)-positive patients were randomly divided into 2 groups: one group received insulin (Ins group), the other a sulfonylurea (SU group). Fifty-four patients (24 Ins group, 30 SU group) were analyzed at the end of a 4-year period. All patients underwent a 75 g oral-glucose test (O-GTT) every 6-12 months. The insulin-dependent stage was defined based on an integrated value of serum C-peptide levels on O-GTT ( summation operator CPR; sum of CPR at 0, 30, 60, 90, and 120 min) below 4.0 ng/mL. The summation operator CPR in the SU group decreased progressively from 22.0 +/- 10.6 to 11.3 +/- 7.5 ng/mL over the 48-month period (p < 0.001 vs. baseline). The summation operator CPR in the Ins group was unchanged. Among the SU group, 30% of subjects (9/30) progressed to IDDM, while 8.3% of Ins group subjects (2/24) progressed to IDDM (p = 0.087). With regard to the subjects who had a preserved C-peptide response ( summation operator CPR >/= 10 ng/mL), the proportion of SU group subjects who progressed to IDDM was significantly higher than that of the Ins group (7/28, 25% vs. 0/21, 0%, p = 0.015). Among subjects with a high GADA titer (>/=0 U/mL), 9/14 (64.3%) of the SU group, but only 2/16 (12.5%) of the Ins group, developed IDDM (p = 0.0068). As to those with a high GADA titer and a preserved C-peptide response, SU group subjects progressed to IDDM (7/12, 58.3%) more frequently than Ins group subjects (0/14, 0%) (p = 0.0012). In summary, our results suggest that small doses of insulin effectively prevent beta cell failure in slowly progressive type 1 diabetes. We recommend avoiding SU treatment and instead administering insulin to NIDDM patients with high GADA titer.

Coupling of oral human or porcine insulin to the B subunit of cholera toxin (CTB) overcomes critical antigenic differences for prevention of type I diabetes

Our earlier investigations have demonstrated a critical difference in the efficacy of orally administered porcine compared to human or mouse insulin (no effect) in preventing type I diabetes in two distinct experimental models. Based on these findings one has to assume that certain insulins might not be suitable for the induction of oral 'tolerance'/bystander suppression, which might be one cause for recent failures in human oral antigen trials. Here we demonstrate that coupling to the non-toxic subunit of cholera toxin (CTB) can abolish these differences in efficacy between human and porcine insulin. As expected, an added benefit was the much smaller oral antigen dose required to induce CD4+ insulin-B specific regulatory cells that bystander-suppress autoaggressive responses. Mechanistically we found that uptake or transport of insulin-CTB conjugates in the gut occurs at least partially via binding to GM-1, which would explain the enhanced clinical efficacy. Both B chains bound well to major histocompatibility complex (MHC) class II, indicating comparable immunological potential once uptake and processing has occurred. Thus, our findings delineate a pathway to overcome issues in oral antigen choice for prevention of type I diabetes.

Improved in planta expression of the human islet autoantigen glutamic acid decarboxylase (GAD65)

The smaller isoform of the enzyme glutamic acid decarboxylase (GAD65) is a major islet autoantigen in autoimmune type 1 diabetes mellitus (T1DM). Transgenic plants expressing human GAD65 (hGAD65) are a potential means of direct oral administration of the islet autoantigen in order to induce tolerance and prevent clinical onset of disease. We have previously reported the successful generation of transgenic tobacco and carrot that express immunoreactive, full-length hGAD65. In the present study, we tested the hypothesis that the expression levels of recombinant hGAD65 in transgenic plants can be increased by targeting the enzyme to the plant cell cytosol and by mediating expression through the potato virus X (PVX) vector. By substituting the NH2-terminal region of hGAD65 with a homologous region of rat GAD67, a chimeric GAD67(1-87)/GAD65(88-585) molecule was expressed in transgenic tobacco plants. Immunolocalization analysis showed that immunoreactive GAD67/65 was found in the plant cell cytosol. By using a radio-immuno assay with human serum from a GAD65 autoantibody-positive T1DM patient, the highest expression level of the recombinant GAD67/65 protein was estimated to be 0.19% of the total soluble protein, compared to only 0.04% of wild-type hGAD65. Transient expression of wild-type, full-length hGAD65 in N. benthamiana mediated by PVX infection was associated with expression levels of immunoreactive protein as high as 2.2% of total soluble protein. This substantial improvement of the expression of hGAD65 in plants paves the way for immunoprevention studies of oral administration of GAD65-containing transgenic plant material in animal models of spontaneous autoimmune diabetes.

Coxsackievirus immunization delays onset of diabetes in non-obese diabetic mice

Enteroviruses may be involved in the pathogenesis of Type 1 diabetes through different mechanisms including triggering of autoimmunity. The effect of immunization with coxsackievirus B4-E2 on diabetes incidence was studied in the non-obese diabetic mice, an animal model for human autoimmune insulin-dependent diabetes mellitus. The immunization delayed the onset of diabetes in the mice, and the effect was mediated at least partially by virus immunization-activated splenocytes as demonstrated by adoptive transfer experiments. Immunization resulted in a strong humoral immune response against the immunizing virus, formalin-inactivated coxsackievirus B4-E2. Cell-mediated immune response to virus antigen was characterised by interferon gamma and interleukin 10 secretion. The immunization also resulted in increased antibody levels against several beta-cell autoantigens. By using epitope mapping we were able to show that in addition to reactivity with the known epitopes of viral proteins and tyrosine phosphatase IA-2 or heat shock protein 60, responses to some other regions of autoantigens were enhanced. In preproinsulin, the response was restricted against an antigenic region earlier identified as DR4-dependent epitope. This reactivity can not be explained by homologous amino acid sequences and it is possible that enterovirus immunization might change the autoantigen specific TH1/TH2 balance in non-obese diabetic mice. In conclusion, our results suggest that coxsackievirus immunization increased humoral immune response to beta cell autoantigens and this was associated with a less destructive pathology for spontaneous diabetes in non-obese diabetic mice.

Antigen-induced regulatory T cells in autoimmunity

The ultimate goal of any treatment for autoimmune diseases is antigen- and/or site-specific suppression of pathology. Autoaggressive lymphocytes need to be eliminated or controlled to prevent tissue damage and halt the progression of clinical disease. Strong evidence is emerging that the induction of regulatory T (T(Reg)) cells by autoantigens can suppress disease, even if the primary, initiating autoantigens are unknown and if inflammation is progressive. An advantage of these autoreactive T(Reg) cells is their ability to act as bystander suppressors and dampen inflammation in a site-specific manner in response to cognate antigen expressed locally by affected tissues. In this review, we consider the nature and function of such antigen-specific T(Reg) cells, and strategies for their therapeutic induction are discussed.

Characterization of antibody responses to endogenous and exogenous antigen in the nonobese diabetic mouse

It is suggested that a T-helper cell 2 (Th2) shift and Th2 spreading of autoimmunity following immunization with beta-cell antigen causes diabetes protection. To address this, antibody titer and subclass to insulin, glutamic acid decarboxylase (GAD)65, IA-2, and IA-2beta proteins were measured by radiobinding assays in untreated or immunized female nonobese diabetic mice. Untreated nonobese diabetic mice developed autoantibodies to insulin (IAA), but not GAD or IA-2/IA-2beta, and IAA-positive mice had increased diabetes risk (P < 0.001). IAA were IgG1 and IgG2b. In immunized mice, IgG1 and lesser IgG2b insulin antibodies were promoted by subcutaneous injection of insulin plus incomplete Freund's adjuvant, insulin plus Montanide ISA 720, and glucagon plus incomplete Freund's adjuvant, but not by incomplete Freund's adjuvant plus GAD65, IA-2beta, or phenylethanolamine N-methyltransferase, or adjuvant alone. Diabetes incidence was significantly reduced in immunized groups with elevated insulin antibody (IA) responses. Spreading of antibody responses to GAD or IA-2/IA-2beta following immunization was rare, and antibody epitope spreading was only detected in IA-2beta immunized mice. Humoral autoimmunity in nonobese diabetic mice is, therefore, limited to IAA with Th2 subclass phenotype and is associated with increased diabetes risk. This contrasts the diabetes protection provided by immunization protocols that promote this response and suggests that Th2 immunity may not be the principal regulator of beta-cell destruction in autoimmune diabetes.

Development of new strategies to prevent type 1 diabetes: the role of animal models

Type 1 diabetes is an immune-mediated disease typically preceded by a long preclinical stage during which a growing number of islet-cell-specific autoantibodies appear in the serum. Although antigen-specific T lymphocytes and cytokines rather than these autoantibodies are the likely executors of beta-cell-destruction, these autoantibodies reflect the existence of autoimmunity that targets islet beta-cells. Abrogation of this autoimmunity during the preclinical stage would be the key to the prevention of type 1 diabetes. However, the quest of protecting islet-cells from the immune attack requires detailed knowledge of mechanisms that control islet-inflammation and beta-cell-destruction, and of mechanisms that control immune tolerance to peripheral self-antigens in general. This knowledge can only be obtained through further innovative research in experimental animal models. In this review, we will first examine how research in non-obese diabetic mice has already led to promising new strategies of diabetes prevention now being tested in human clinical trials. Thereafter, we will discuss how recent advances in understanding the mechanisms that control immune response to peripheral self-antigens such as beta-cell antigens may help to develop even more selective and effective strategies to prevent diabetes in the future.

Resistance to alopecia areata in C3H/HeJ mice is associated with increased expression of regulatory cytokines and a failure to recruit CD4+ and CD8+ cells

Grafting alopecia areata affected C3H/HeJ mouse skin to littermates induces alopecia areata, but high dietary soy oil reduces alopecia areata susceptibility. Alopecia areata affected and resistant mice were characterized to evaluate possible mechanisms involved in alopecia areata resistance. Of 44 mice that received alopecia areata affected skin grafts but failed to develop alopecia areata, only two of 22 receiving further alopecia areata affected skin grafts developed alopecia areata, whereas 39 of 44 controls developed alopecia areata. Alopecia areata affected skin contained increased numbers of CD4+ and CD8+ cells, increases in pro inflammatory T helper 1 and T helper 2 type cytokines, and upregulation of CD28, CD40L, and their ligands. In draining lymph nodes, a relatively high number of antigen-presenting cells was recovered, whereas several CD44v variants were downregulated. In contrast, alopecia areata resistant mouse skin did not display increased numbers of CD4+ and CD8+ cells, whereas counter-regulatory cytokines interleukins 4 and 10 were upregulated. High expression of CD28, CD80, CD86, CD40, CTLA4, CD44v variants, and FasL occurred in alopecia areata resistant mouse spleens. In vitro, lymph node cells of susceptible and resistant mice responded equally to a mitogenic stimulus, but only lymph node cells from alopecia areata affected mice displayed an increased response with T cell receptor stimulation via anti-CD3 cross-linking. These results suggest alopecia areata is a cell-mediated autoimmune disease, but alopecia areata affected skin graft hosts may resist alopecia areata onset through active counter-regulatory mechanisms. Because alopecia areata resistant mice showed unimpaired responsiveness and a transient inflammatory response towards the graft, it is suggested that alopecia areata develops as a consequence of an inappropriate immune response regulation.

alpha4 integrins and L-selectin differently orchestrate T-cell activity during diabetes prevention following oral administration of CTB-insulin

Oral administration of insulin conjugated to the B chain of cholera toxin (CTB-insulin) in non-obese diabetic (NOD) mice results in diabetes prevention. We investigated the respective contributions of L-selectin (CD62L) and alpha4-integrin pathways during CTB-driven tolerance. Purified CD62L+CD4+ cells from CTB-insulin fed mice significantly reduced the capacity of diabetogenic T cells to transfer diabetes in syngeneic recipients. In vivo antibody blockade of fed animals during adoptive co-transfer experiments indicated that both CD62L and alpha4-integrins pathways were necessary to develop a protective response after oral tolerance induction. In contrast, when antibodies were given to recipient mice, only CD62L was critical for the protection. In vitro stimulated CD62L+CD4+ cells from the spleen of fed animals secreted lower amounts of IL-4 and IL-10 but comparable levels of TGFbeta than CD62L-cells. A reduced IFN-gamma production between the two cell subsets was specifically observed in CTB-insulin fed mice. Furthermore, antibody treatments induced changes in T-cell migration to the spleen, mesenteric and pancreatic lymph nodes. The protective effect was also associated with migration of regulatory T cells into pancreatic islets. Taken together, our results suggest that L-selectin and alpha4-integrin have distinct but complementary roles in the generation and function of regulatory CD4+ T cells following CTB-insulin administration.

Spontaneous peripheral T-cell responses to the IA-2beta (phogrin) autoantigen in young nonobese diabetic mice

Phogrin (IA-2beta), a major autoantigen in type 1 diabetes in man is recognized by peripheral T cells in the nonobese diabetic (NOD) mouse. CD4(+) T-cell clones derived from immunized NOD animals elicit islet destruction in a disease transfer model. Spontaneous proliferative responses to the protein and derived peptide epitopes were detected in peripheral lymph node cells (LNC) of unprimed NOD mice but not BALB/c controls as early as 4 weeks of age at a time point when insulitis in NOD animals is minimal. Responses to irradiated NOD islet cells but not irradiated NOD spleen cells were observed for both male and female NOD animals. Insulin, phogrin and phogrin-peptide 7 (aa 755-777) but not phogrin-peptide 2 (aa 640-659) or tetanus toxin peptide were recognized as antigens. Islet cell-reactive and phogrin peptide 7-specific CD4(+) T-cell lines were generated from splenocytes of unprimed 4-week-old NOD females and shown to secrete Th1-type cytokines. The results show that the phogrin molecule is targeted early in the course of disease in NOD animals at a time when circulating autoantibodies are absent and insulitis is minimal.

Continuous nasal administration of antigen is critical to maintain tolerance in adoptively transferred autoimmune arthritis in SCID mice

Mucosal tolerance is a natural mechanism that prevents immunological reactions to antigens by altering the activity of immune cells of pathogenic clones without modulating the entire immune system. This 'natural immune suppression' can be exploited when antigen(s) of the target organ in an autoimmune disease is used for mucosal treatment. Being inspired by the experimental results in animal models, clinical trials using type II collagen for mucosal treatment have been conducted in rheumatoid arthritis. High-density proteoglycan (aggrecan) is another major macromolecular component in articular cartilage, and may be a candidate autoantigen for provoking immune reactions in patients with rheumatoid arthritis. Indeed, like type II collagen, systemic immunization of genetically susceptible mice with proteoglycan (PG) aggrecan induces progressive autoimmune polyarthritis. Here, we investigated whether intranasally applied PG can be effective in suppressing PG-induced arthritis (PGIA) in BALB/c mice. We found that nasal administration of 100 microg PG exerted a strong suppressive effect on both the incidence and severity of the disease, most probably by reducing responsiveness towards the immunizing PG antigen. When we transferred PGIA into genetically matched but immunodeficient SCID mice, we were able to establish a tolerized state, but only if the recipient SCID mice received lymphocytes from tolerized animals and intranasal treatment with PG was continued. Without nasally administered antigen, the transferred anergic cells recovered and arthritis rapidly developed in a severe form. Intranasal PG treatment of recipient SCID mice was ineffective when cells from non-tolerized arthritic donors were transferred, in which case the regular weekly 'tolerizing' dose of PG made the disease worse. Our results suggest that mucosal treatment in an already existing disease may result in paradoxical outcomes.

Inhibition of adjuvant-induced arthritis by interleukin-10-driven regulatory cells induced via nasal administration of a peptide analog of an arthritis-related heat-shock protein 60 T cell epitope

OBJECTIVE

To prevent and treat experimental arthritis via nasal administration of an altered peptide ligand (APL) from the major arthritogenic epitope in adjuvant-induced arthritis (AIA) and to explore the mechanisms involved.

METHODS

Peptides were administered nasally before and after induction of arthritis. Splenocytes and lymph node cells draining both the site of inflammation and the site of tolerance induction were used for cell transfer and were studied for antigen-specific T cell characteristics. In addition, attempts were made to stop T cell tolerance in vitro, using anticytokine antibodies.

RESULTS

Nasal administration of a modulatory APL of the heat-shock protein 60 (Hsp60) 180-188 T cell epitope, alanine 183, had a suppressive effect in AIA that far exceeded that of the wild-type epitope. In addition to its effectiveness in preventing AIA, alanine 183 may be effective in the treatment of ongoing AIA. The protective effect of alanine 183 can be passively transferred using activated splenocytes. Nasal administration of alanine 183 did not lead to detectable T cell proliferation or interleukin-2 (IL-2) production in mandibular lymph node cells, while transforming growth factor beta (TGF beta), IL-10, and IL-4 were readily produced. Likewise, after nasally induced tolerance, followed by induction of arthritis, inguinal lymph node cells produced IL-4, TGF beta, and IL-10. After neutralizing in vitro the individual cytokines with anticytokine antibodies, only blocking of IL-10 production led to reversal of tolerance, at the site of tolerance induction and the site of inflammation.

CONCLUSION

Nasal administration of an APL of Hsp60 180-188 induces highly effective protection against AIA through generation of regulatory cells that produce IL-4, TGF beta, and IL-10, whereas the induced tolerance is driven mainly by production of IL-10.

Immunomodulatory vaccination in autoimmune disease

The development of vaccines is arguably the most significant achievement in medicine to date. The practice of innoculation with the fluid from a sore to protect from a disease actually dates back to ancient China; however, with the introduction of Jenner's smallpox vaccine, and greater understanding of the immune system, vaccines have become specific and systematic. Traditional vaccines have used killed pathogens (hepatitis A and the Salk polio vaccines), immunogenic subunits of a given pathogen (hepatitis B subunit vaccine), or live attenuated pathogens (measles, mumps, rubella, Sabin polio vaccines) to generate protective immunity. Currently, a new generation of vaccines that use the genetic material of a pathogen to elicit protective immunity are being developed. Although the most widespread and successful use of vaccines today remains in the arena of infectious diseases, manipulations of immune responses to protect against cancers, neurologic diseases, and autoimmunity are being explored rigorously.

Genetic fusion of human insulin B-chain to the B-subunit of cholera toxin enhances in vitro antigen presentation and induction of bystander suppression in vivo

The pentameric B-subunit of cholera toxin (CTB) can be used as an efficient mucosal carrier of either immunogenic or tolerogenic T-cell epitopes. In this study a series of fusions was constructed between the genes encoding CTB and the B-chain of human insulin (InsB). The resulting fusion proteins were expressed in Escherichia coli and isolated as cytoplasmic inclusion bodies that were then dissolved and assembled in vitro. GM1 enzyme-linked immunosorbent assay (ELISA), sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analyses showed that the protein construct in which InsB was fused to the C-terminus of a CTB monomer (CI) assembled into structures that both bound to the receptor GM1 ganglioside and reacted with monoclonal antibodies to CTB and insulin. Fusion of InsB to the N-terminus of CTB resulted in protein that could not assemble into pentameric CTB. In vitro assays showed that the CI fusion protein was 300-fold more potent than native insulin at inducing interleukin-2 (IL-2) production by an insulin-specific T-cell hybridoma. When administered orally, the CI fusion protein induced efficient immunological suppression of ovalbumin-specific T-cell responses in mice co-immunized parenterally with insulin and ovalbumin. These results demonstrate the stability, GM1 receptor-binding activity and antigenic authenticity of the CI fusion protein as well as its ability to elicit insulin-specific T-cell responses in vitro. In addition, we demonstrate that the CI fusion protein induces efficient immunosuppression after oral administration, raising the possibility of using such constructs in the treatment of type-1 diabetes.

Vaccination to prevent type 1 diabetes

Immune-based interventions to treat or prevent autoimmune disorders are opening up entirely novel therapeutic avenues. Presently, systemic immune modulators such as antibodies to cytokines or cell-surface molecules (i.e., costimulators) are undergoing clinical testing or are already in use. The next generation of interventions will function in an antigen-specific way. These strategies are more difficult to design, because successful immunization or vaccination has to be monitored on an individual basis and dose/route/timing considerations play an essential role. Both will be discussed in this chapter and suitable combinatorial approaches will be suggested.

Induction and acceleration of insulitis/diabetes in mice with a viral mimic (polyinosinic-polycytidylic acid) and an insulin self-peptide

Polyinosinic-polycytidylic acid (PolyIC), a "mimic" of double-stranded viral RNA, can induce diabetes when administered to rats with RT1(u), and immunization of normal H-2(d) mice (e.g., BALB/c) with insulin B:9-23 peptide (but not H-2(b)) results in the rapid induction of insulin autoantibodies. Because a mouse model of PolyIC/antigen-induced diabetes is lacking, we sought to produce insulitis and diabetes with either PolyIC and/or B:9-23 peptide immunization. Simultaneous administration of PolyIC and B:9-23 peptide to BALB/c mice (but with neither alone) induced insulitis. CD4 T lymphocytes predominated within islets, and the mice did not progress to hyperglycemia. Islets with transgene-induced expression of the costimulatory B7-1 molecule have enhanced diabetes susceptibility. Diabetes was frequently induced in B7-1 transgenic mice with H-2(d) in contrast to H-2(b) mice after PolyIC administration. Disease induction was accelerated by adding B:9-23 immunization to PolyIC. These studies demonstrate that "normal" mice have autoreactive T lymphocytes able to rapidly target islets and insulin given appropriate MHC alleles and that a peripherally administered insulin peptide (an altered peptide ligand of which is in clinical trials) can enhance specific anti-islet autoimmunity. These first PolyIC/insulin-induced murine models should provide an important tool to study the pathogenesis of type 1 diabetes with experimental autoimmune diabetes.

Suppression of collagen-induced arthritis by single administration of poly(lactic-co-glycolic acid) nanoparticles entrapping type II collagen: a novel treatment strategy for induction of oral tolerance

OBJECTIVE

Poly(lactic-co-glycolic acid) (PLGA), a biodegradable polymer, is a carrier for drug delivery systems. This study was undertaken to investigate the tolerogenic effect of single administration of PLGA entrapping type II collagen (CII) on the development of collagen-induced arthritis (CIA).

METHODS

The biophysical properties of PLGA nanoparticles entrapping CII (PLGA-CII) were investigated by in vitro release testing of CII, immunohistochemistry analysis, and electron microscopy. PLGA-CII was fed singly to animals 14 days before immunization, and the effect on joint inflammation was assessed. Circulating IgG anti-CII antibodies and T cell responses to CII in draining lymph nodes were assayed by enzyme-linked immunosorbent assay and (3)H-thymidine incorporation assay, respectively. The expression of messenger RNA (mRNA) for transforming growth factor beta (TGFbeta) and tumor necrosis factor alpha (TNFalpha) was determined by reverse transcriptase-polymerase chain reaction.

RESULTS

The in vitro release test showed that CII was slowly discharged from PLGA-CII over a period of a month. After single administration of PLGA-CII, numerous particles approximately 300 nm in size were detectable in Peyer's patches, by electron microscopy and immunohistochemical staining for CII, 14 days after the original feeding. Mice fed a single dose of PLGA containing 40 microg of CII had significantly reduced values for incidence and severity of arthritis, serum IgG anti-CII antibodies, and CII-specific T cell proliferation as compared with mice fed solvent alone, those fed 6 doses of 20 microg CII alone, and those fed a single dose of PLGA alone. PLGA-CII was also able to suppress CIA after disease onset. Moreover, PLGA-CII-fed mice showed a higher level of TGFbeta mRNA expression in Peyer's patches, but a lower level of TNFalpha mRNA expression in draining lymph nodes, compared with the other groups of mice.

CONCLUSION

Our data show that PLGA may serve as a powerful vehicle to promote the tolerance effect of oral CII and that single administration of PLGA-CII may hold promise as a new treatment strategy in rheumatoid arthritis.

A new model for analyzing immunomodulation of T cell responses induced by oral administration of islet cell antigens

Based on the coimmunization of BALB/c mice with insulin and ovalbumin, we here describe a feasible efficacy model for analyzing the tolerogenic effect of the oral administration of sequestered antigens-for example, islet-specific proteins such as insulin and GAD65.

The gut immune system and type 1 diabetes

Accumulating data suggest that the gut immune system plays a role in the development of autoimmune diabetes: (1) Diet modifies the incidence of autoimmune diabetes and the phenotype of the islet-infiltrating T cells in the animal models of human type 1 diabetes; (2) gut-associated homing receptor beta7-integrin is found on the islet-infiltrating T cells in both human type 1 diabetes and in the animal models of autoimmune diabetes; (3) mesenterial lymphocytes from young NOD mice are able to transfer diabetes to healthy recipients; (4) autoantigen feeding modifies the disease development in the animal models (prevents or accelerates autoimmune diabetes). In humans, a link between the gut immune system and type 1 diabetes has also been suggested. Early introduction of cow milk formulas in infancy may increase the risk of type 1 diabetes. We have demonstrated that primary immunization to a beta cell-specific autoantigen, insulin, occurs in the gut by exposure to cow milk formulas, which contain immunogenic bovine insulin. The induced antibody and T cell responses to bovine insulin cross-react with human insulin. In children at genetic risk who developed beta cell autoimmunity, bovine insulin-binding antibodies increased during follow-up in contrast to autoantibody-negative children. This suggests that insulin-specific immune response induced by dietary insulin may not be controlled in children prone to beta cell autoimmunity. The gut immune system has a key role in controlling insulin-specific immunity induced by dietary insulin. Indeed, indications for aberrant function of the gut immune system have been reported in type 1 diabetes, such as intestinal immune activation and increased intestinal permeability. Research on the gut immune system in human type 1 diabetes is needed to reveal the role of oral immunity in this disease.

Feeding NOD mice with pig splenocytes induces transferable mechanisms that modulate cellular and humoral xenogeneic reactions against pig spleen or islet cells

We have reported previously that oral administration of pig cells to NOD mice modified xenogeneic cellular response against pig islet cells (PICs), and hypothesized that it may have induced active suppression. This preliminary report evaluated only the effect of feeding pig cells by 'primary' proliferation, i.e. when splenocytes from fed mice are confronted with pig cells in vitro. The present study also considered 'secondary' proliferation and cytokine production after feeding and subsequent in vivo graft of pig cells. Additionally, serum IgM and IgG isotypes were quantified by ELISA using pig target cells. Induction of active mechanism by feeding was hypothetical, which led us here to transfer splenocytes from mice fed pig spleen cells (PSC) and evaluate 'primary' (after transfer) and 'secondary' (after transfer and subsequent graft of pig cells) proliferations and cytokine secretions in recipient mice. We also determined whether the effects of feeding pig cells persisted after depression of suppressor mechanisms by cyclophosphamide. Mice fed with PSC displayed increased 'primary' splenocyte proliferation to PSC or PIC (P < 0.0001), while 'secondary' responses were decreased (P < 0.03) in those fed PSC and subsequently grafted with PSC. The increased 'primary' and decreased 'secondary' proliferations were reduced (P < 0.04) by pretreatment with cyclophosphamide. The IL-10/ and IL-4/IFNgamma ratios produced in response to PSC increased (P < 0.04) in mice fed and grafted with PSC compared to those grafted only with PSC. IgM and IgG levels against pig cells were, respectively, increased (P < 0.04) and decreased (P < 0.04) in mice fed and grafted with PSC. IgG2a and IgG2b, but not IgG1, levels were lower (P < 0.01). These effects of feeding PSC on 'secondary' proliferation, cytokine and antibody productions, were not detected when mice were fed PSC only after graft with PSC. Transfer with splenocytes from mice fed PSC increased 'primary' proliferation of splenocytes from recipient mice in response to PSC (P < 0.02) or PIC (P < 0.05). After transfer with splenocytes from PSC-fed mice and graft with PSC, 'secondary' proliferation to pig cells were reduced (P < 0.04), and the IL-10/IFNgamma ratio produced in response to PSC was increased fourfold. Thus, oral administration of PSC induces active transferable mechanisms, characterized by a biphasic pattern with early increased 'primary' xenogeneic cellular reactions to both PSC and PIC, followed by decreased 'secondary' responsiveness and a concomitant shift of the Th1/Th2 balance towards greater Th2 influence. Decreased responsiveness may be due to active suppression, even though induction of anergy or deletion cannot be excluded.

Endogenous expression levels of autoantigens influence success or failure of DNA immunizations to prevent type 1 diabetes: addition of IL-4 increases safety

Administration of autoantigens through DNA immunizations or via the oral route can prevent progression of islet destruction and lower the incidence of type 1 diabetes in animal models. This beneficial effect is mediated by autoreactive regulatory CD4 lymphocytes, and it is known that their induction depends on the precise dose and route of antigen administration. However, it is not clear which endogenous factors determine when such immunizations lead to activation of regulatory versus aggressive autoreactive lymphocytes and how a deleterious outcome can be avoided. Here we describe novel observations made in an animal model for virally induced type 1 diabetes, showing that the endogenous expression levels of the islet antigens and glutamic acid decarboxylase determine whether immunization with these antigens is beneficial or detrimental. Lower expression levels in beta-cells support immune regulation resulting in induction of autoreactive, regulatory cells characterized by increased IL-4 production (Th2-like), whereas higher levels favor Th1-like autoaggressive responses characterized by augmented IFN-gamma generation. Co-immunization with an IL-4-expressing plasmid reduces the risk of augmenting autoaggression and in this way increases the safety margin of this immune-based therapy. Our findings will be of importance for designing safe antigen-specific interventions for human type 1 diabetes.

Immunotherapy of type 1 diabetes: lessons for other autoimmune diseases

The nonobese diabetic (NOD) mouse is a well-recognised animal model of spontaneous autoimmune insulin-dependent diabetes mellitus. The disease is T-cell mediated, involving both CD4 and CD8 cells. Its progress is controlled by a variety of regulatory T cells. An unprecedented number of immunological treatments have been assessed in this mouse strain. This chapter systematically reviews most of these therapeutic manoeuvres, discussing them in the context of their significance with regard to the underlying mechanisms and the potential clinical applications. The contrast between the surprisingly high rate of success found for a multitude of treatments (more than 160) administered early in the natural history of the disease and the few treatments active at a late stage is discussed in depth. Most of the concepts and strategies derived from this model apply to other autoimmune diseases, for which no such diversified data are available.

Oral exposure to diabetes-promoting food or immunomodulators in neonates alters gut cytokines and diabetes

Disease development in diabetes-prone BB rats is modified by the type of diet fed after weaning. The aim of this investigation was to determine whether exposure during the first week of life to antigens from a known diabetes-promoting diet (NIH-07) could modify diabetes incidence and, if so, to what extent this occurs via alterations in systemic T-cell reactivity, gut cytokines, or islet infiltration. Diabetes-prone BB (BBdp) rats were hand-fed twice daily between age 4 and 7 days with vehicle, a hydrolyzed casein (HC)-based infant formula, Pregestimil (PG), PG + cereal-based NIH-07 diet, PG + lipopolysaccharides (LPS) or PG + LPS + silica. After weaning, they were fed either an NIH-07 diet or a semipurified HC (diabetes-retardant) diet until 150 days. In separate studies, 5-day-old BBdp rat pups were administered the aforementioned treatments, and expression of intestinal mRNA for gamma-interferon (IFN-gamma) or transforming growth factor-beta (TGF-beta) was quantified using reverse transcriptase-polymerase chain reaction. The effect of early oral treatment with NIH-07 or PG on systemic T-cell reactivity was evaluated using footpad swelling delayed-type hypersensitivity (DTH) and the popliteal lymph node assay. Oral exposure of neonates to a complex mixture of antigens from the diabetes-promoting diet delayed onset of diabetes (79 vs. 88 days) and prevented disease in approximately one-third of animals. A similar protective effect was seen for neonatal exposure to wheat gluten in animals subsequently weaned onto a semipurified wheat gluten diet. By contrast, LPS-treated neonates displayed more severe insulitis and developed diabetes at an increased rate, which was significantly suppressed by co-administration of silica particles. The protective effect of early exposure to diabetogenic diets was not associated with significant reduction of islet infiltration, and there was no impact on the DTH response to food antigens. However, whereas diabetes-resistant BBc rats developed systemic tolerance to NIH-07 antigens fed chronically, BBdp rats did not. The lack of effect of the early oral antigen regimen on the DTH reaction in the footpad, a classic Th1-mediated reaction, suggests little effect on systemic T-cell reactivity. However, local effects were observed in the small intestine. Oral exposure to diabetes-promoting food antigens or LPS downregulated the Th1 cytokine IFN-gamma and decreased the IFN-gamma/TGF-beta ratio. Thus, oral exposure to diabetes-promoting food antigens and immune modulators in neonates can modify diabetes expression in association with changes in local cytokine balance in the gut.

Insulin-specific tolerance in diabetes

At present it is possible to predict the development of type 1A diabetes (immune-mediated diabetes) in man and prevent the disorder in animals. Studies of immunity to insulin play a prominent role in both disease prediction and disease prevention. For both man and the NOD mouse, insulin autoantibodies usually precede the development of diabetes and can be utilized to assist in disease prediction. T cells clones recognizing insulin, both CD4 and CD8, can transfer disease to young mice or immunodeficient animals. Specific insulin peptides reacting with these clones have been identified, their crystal structure when bound to a human "diabetogenic" MHC allele has been determined, and specific peptides can be used either to induce or to prevent disease. Clinical trials of both insulin and an altered peptide ligand of insulin to prevent islet beta-cell destruction are underway. Insulin is one of a number of islet autoantigens, but it is likely that immune responses to insulin will be central to both pathogenesis and immunologic protection.

Insulin in human milk and the prevention of type 1 diabetes

Although controversial, exclusive breast milk feeding was shown to exert a protective effect in preventing type 1 diabetes. In contrast, an early introduction of cow's milk-based formula in young infants may enhance the risk of disease, especially in genetically susceptible children, presumably by an increase of intestinal permeability to macromolecules such as bovine serum albumin and beta-casein, which may arouse autoimmunity. We have shown that human milk contains insulin in substantial concentrations, while insulin is barely detectable (if at all) in infant formulas. Orally administered insulin was demonstrated to promote gut maturation and to reduce intestinal permeability to macromolecules. Furthermore, oral insulin may induce tolerance to insulin and protect against the development of type 1 diabetes. We herewith raise a hypothesis that human milk is protective against the development of type 1 diabetes by virtue of the effects of its substantial content of insulin.

Evidence that a peptide spanning the B-C junction of proinsulin is an early Autoantigen epitope in the pathogenesis of type 1 diabetes

The expression of pro(insulin) in the thymus may lead to the negative selection of pro(insulin) autoreactive T cells and peripheral tolerance to this autoantigen in type 1 diabetes (T1D). We investigated whether proinsulin is expressed in the thymus of young nonobese diabetic (NOD) mice, whether T cells from naive NOD female mice at weaning are reactive to mouse proinsulin, and the role of proinsulin as a pathogenic autoantigen in T1D. Proinsulin II mRNA transcripts were detected in the thymus of 2-wk-old NOD mice at similar levels to other control strains. Despite this expression, proinsulin autoreactive T cells were detected in the periphery of 2- to 3-wk-old naive NOD mice. Peripheral T cells reactive to the insulin, glutamic acid decarboxylase 65 (GAD65), GAD67, and islet cell Ag p69 autoantigens were also detected in these mice, indicating that NOD mice are not tolerant to any of these islet autoantigens at this young age. T cell reactivities to proinsulin and islet cell Ag p69 exceeded those to GAD67, and T cell reactivity to proinsulin in the spleen and pancreatic lymph nodes was directed mainly against a p24-33 epitope that spans the B chain/C peptide junction. Intraperitoneal immunization with proinsulin perinatally beginning at 18 days of age delayed the onset and reduced the incidence of T1D. However, s.c. immunization with proinsulin initiated at 5 wk of age accelerated diabetes in female NOD mice. Our findings support the notion that proinsulin p24-33 may be a primary autoantigen epitope in the pathogenesis of T1D in NOD mice.

Immunotherapy of insulin-dependent diabetes mellitus

Immunotherapy of diabetes is now focusing on induction of tolerance to beta cell antigens using either soluble antigens or monoclonal anti-T-cell antibodies. These approaches have reached the clinical arena. At the experimental level, strategies are being developed that use or target cytokines (with gene therapy) or stimulate regulatory T cells.

Production of a recombinant hybrid molecule of cholera toxin-B-subunit and proteolipid-protein-peptide for the treatment of experimental encephalomyelitis

Mucosal administration of experimental autoimmune encephalomyelitis (EAE)-specific autoantigens can reduce the onset of disease. To examine whether cholera toxin-B-subunit (CTB)-conjugated EAE-specific T-cell epitope can reduce development of the autoimmune disease in mice, we produced a recombinant hybrid molecule of CTB fusion protein linked with proteolipid-protein (PLP)-peptide139-151(C140S) at levels up to 0.1 gram per liter culture media in Bacillus brevis as a secretion-expression system. Amino acid sequencing and GM1-receptor binding assay showed that this expression system produced a uniformed recombinant hybrid protein. EAE was induced in SJL/J mice by systemic administration with the PLP-peptide. When nasally immunized 5 times with 70 microg rCTB PLP-peptide hybrid protein, mice showed a significantly suppressed development of ongoing EAE and an inhibition of both the PLP-peptide-specific delayed-type hypersensitivity (DTH) responses and leukocyte infiltration into the spinal cord. In contrast, all mice given the PLP-peptide alone or the PLP-peptide with the free form of CTB did not suppress the development of EAE and DTH responses. These results suggest that nasal treatment with the recombinant B. brevis-derived hybrid protein of CTB and autoantigen peptide could prove useful in the control of multiple sclerosis.

Pathophysiology of immune-mediated (type 1) diabetes mellitus: potential for immunotherapy

Type 1 diabetes mellitus is a chronic T cell-mediated disease resulting from autoimmune destruction of pancreatic beta-cells. This process leads to progressive and irreversible failure of insulin secretion. Development of the disease involves both genetic and environmental factors. Genetic predisposition is mainly connected with the human leucocyte antigen (HLA) region, which encodes structures responsible for antigen presentation. A comprehensive molecular understanding of the pathogenesis of the disease is essential for the design of rational and well tolerated means of prevention. This paper describes recent experimental and clinical findings and elucidates the current possibilities for immunotherapy of type 1 diabetes. The nature of breakdown of self-tolerance and the mechanisms involved in its recovery are discussed.

Tolerance to islet autoantigens in type 1 diabetes

Tolerance to beta cell autoantigens represents a fragile equilibrium. Autoreactive T cells specific to these autoantigens are present in most normal individuals but are kept under control by a number of peripheral tolerance mechanisms, among which CD4(+) CD25(+) CD62L(+) T cell-mediated regulation probably plays a central role. The equilibrium may be disrupted by inappropriate activation of autoantigen-specific T cells, notably following to local inflammation that enhances the expression of the various molecules contributing to antigen recognition by T cells. Even when T cell activation finally overrides regulation, stimulation of regulatory cells by CD3 antibodies may reset the control of autoimmunity. Other procedures may also lead to disease prevention. These procedures are essentially focused on Th2 cytokines, whether used systemically or produced by Th2 cells after specific stimulation by autoantigens. Protection can also be obtained by NK T cell stimulation. Administration of beta cell antigens or CD3 antibodies is now being tested in clinical trials in prediabetics and/or recently diagnosed diabetes.

Prediction and prevention of type 1 diabetes

The incidence of type 1 diabetes continues to increase worldwide. Despite major strides in the daily care of patients with the disease, the patients' contribution to overall morbidity and mortality statistics and health care economic burden to society is disproportionately large because of the high rate of microvascular and macrovascular complications. The quest for prevention of type 1 diabetes has been made feasible by the unraveling of the immunogenetics of the disease and the identification of at-risk subjects by an enhanced understanding of the natural history of the prediabetic period. A combination of immunologic, metabolic, and genetic markers can be used to accurately predict the disease in higher-risk relatives and the general population. This has enabled initiation of worldwide trials (Diabetes Prevention Trial-Type 1, European Nicotinamide Diabetes Intervention Trial, and Trial to Prevent Diabetes in Genetically at Risk) aimed at the prevention of the disease. Various promising agents are being considered for use in different at-risk populations in the near future.

Oral administration of collagen conjugated with cholera toxin induces tolerance to type II collagen and suppresses chondritis in an animal model of autoimmune ear disease

B10.RIII (H-2r) mice were orally administered cyanogen bromide peptide 11 (CB11) or cholera toxin B (CTB)-conjugated CB11 to induce tolerance in collagen-induced autoimmune ear disease. Oral administration of a high dosage of CB11 provided partial protection from chondritis. However, administration of a tiny amount of CTB-CB11 conjugate effectively suppressed chondritis. Oral administration of CTB-CB11 conjugate did not alter the stimulation of T cells in vitro or the fine specificities of B cells. The oral administration of CTB-CB11 caused a higher level of type II collagen-specific IgG and its subclass. Interestingly, increases of TH1 cytokine (interferon-gamma) in Peyer's patches and of TH1/TH2 cytokines (interleukin-2 and interleukin-4) in lymph nodes were detected in mice that had been fed CTB-CB11. An increase of CD8+ T cells in the Peyer's patches with a decrease of CD8+ T cells in lymph nodes was seen in mice that had been fed CTB-CB11. These results suggest that protection from chondritis by oral administration of minute amounts of CTB-CB11 conjugate can be achieved by a mechanism distinct from that of conventional oral tolerance induction.