A cyclic peptide significantly improves thyroid function, thyrotropin-receptor antibodies and orbital mucine /collagen content in a long-term Graves' disease mouse model.

BACKGROUND: BALB/c mice which received long-term immunizations of adenovirus (Ad) expressing thyrotropin receptor A-subunits (TSHR) developed stable Graves' disease (GD). TSHR-derived cyclic peptide 19 (P19) was identified as effective therapy in this model. METHODS: In Ad-TSHR mice, we investigated shorter disease intervals up to 4 months for histological alterations of the orbits, fine tuning of anti-TSHR antibodies (Ab) and free thyroxine (fT4) hormone levels by using novel detection methods in an independent laboratory. Therapy (0.3 mg/kg P19 or vehicle) was given intravenously after the fourth Ad-TSHR immunization (week 11) and continued until week 19. RESULTS: Thyrotropin binding inhibitory immunoglobulins (TBII, bridge immunoassay), blocking (TBAb) and stimulating (TSAb) TSHR-Ab (both cell-based bioassays) and serum levels of fT4 were significantly elevated at week 11 in Ad-TSHR-immunized mice versus none in control mice. For the first time, TSAb, TBAb, and thyroperoxidase-Ab were detected in 17 of 19, 12/19 and 6/19 Ad-TSHR immunized mice, respectively at week 21. Also, for the first time, this study showed that P19 treatment markedly reduced serum TBII (p < 0.0001), serum fT4 (p = 0.02), and acidic mucins and collagen content in the orbital tissue of Ad-TSHR-immunized mice. CONCLUSION: P19 significantly improved thyroid function, confirming previous results in an independent second laboratory. A relevant shift of anti-TSHR antibody subpopulations in response to P19 therapy may help explain its immunological effects. Moreover, P19 exerted a beneficial effect on mucine and collagen content of orbital tissue. Hence, P19 offers a potential novel therapeutic approach for GD and associated orbitopathy.

Low regulatory T cell and high IL-17 mRNA expression in a mouse Graves' disease model.

PURPOSE: Graves' disease (GD) is an autoimmune thyroid disease, and the most important characteristic of it is the presence of the thyroid-stimulating antibody (TSAb). The mechanisms of the TSAb elevation are still uncertain. Recent studies have suggested that the dysregulation of regulatory T cell (Treg) and T helper 17 (Th17) might stimulate the production of TSAb and be a pathogenesis of GD. However, the role of Treg and Th17 cells in the pathogenesis of GD is still debated. Our aim is to assess changes of Treg and Th17 cells in the spleen of a mouse in an in vivo GD model and try to explain the pathogenesis of GD. METHODS: We used an adenovirus expressing the autoantigen thyroid-stimulating hormone receptor (Ad-TSHR289) to immunise mice in order to induce GD in the model. Flow cytometry was used to measure the frequencies of splenic Treg and Th17 cells and real-time PCR to analyse the mRNA expression of forkhead box P3(Foxp3) and interleukin-17(IL-17). RESULTS: Compared with the Ad-Control group, the frequencies of CD4+CD25+Foxp3+ Treg cells were significantly decreased (p = 0.007) and gene expression of Foxp3 was down-regulated (p = 0.001) in the Ad-TSHR289 group. Though there was no significant difference in CD4+IL-17+ T cell subpopulation between the two groups (p = 0.336), the IL-17 mRNA expression was significantly up-regulated in the Ad-TSHR289 group (p = 0.001). CONCLUSIONS: The pathogenesis of GD may be associated with reduced Treg cells and increased IL-17 gene expression. The increased IL-17 mRNA needs to be explained by other mechanisms but not Th17 cells.

Immunoglobulins of untreated Graves' patients with or without thyrotropin receptor antibody (determined by porcine thyrocytes) universally elicit potent thyroid hormone-releasing activity in cultured human thyroid follicles.

Thyrotropin receptor antibody (TRAb), comprising thyrotropin binding inhibitor immunoglobulin (TBII) and thyroid-stimulating antibody (TSAb), both of which are conventionally determined using porcine thyrocytes in Japan, is not always positive in patients with untreated Graves' disease. To elucidate whether immunoglobulin G (IgG) obtained from TBII/TSAb-positive (+) or negative (-) Graves' disease patients are responsible for hyperthyroidism, we investigated the thyroid hormone-releasing activity (THRA) of these IgGs in human thyroid follicles in suspension culture, in which bovine thyrotropin (bTSH) is detectable even at 0.1 microU/mL. Human thyroid follicles, obtained from Graves' disease patients by subtotal thyroidectomy, were cultured in serum-free F-12/RPMI-1640 medium supplemented with bTSH or purified Graves' IgGs. After preculturing for 3 days, 125I was added, and after an additional 3 days of culture, 1251 incorporated into the thyroid follicles and organic 125I released into the culture medium (mainly 1251 -T4 + 125I-T3) were counted. Seventy TBII(+)/TSAb( + )-, 3 TBII( + )/TSAb( - )-, and 3 TBII( - )/TSAb( + )- patients with untreated Graves' disease were all positive for THRA, which became undetectable in spontaneous remission obtained after several years of medical treatment. The THRA was equivalent to 0.8-230 microU/mL bTSH. Furthermore, 2 TBII(-)/TSAb(-) patients were significantly positive for THRA. This TBII(-)/TSAb(-)IgG stimulated human thyrocytes to produce cyclic adenosine monophosphate (cAMP), and this was partially inhibited by antihuman IgG antibody. The THRA induced by TBII(+)/TSAb(+) IgGs as well as TBII(-)/TSAb(-) IgG was inhibited by blocking-type TRAb obtained from TBII(+) patients with myxedema. There was a significant correlation between THRA and TSAb. These in vitro findings suggest that all IgGs obtained from untreated Graves' patients (n = 78) elicit potent THRA in human thyroid follicles in suspension culture. Because the TBII(-)/TSAb(-) IgGs can stimulate cAMP production in human but not in porcine thyrocytes, they probably recognize epitope(s) of TSH-binding sites specific to the human thyrotropin (hTSH) receptor. Furthermore, we have demonstrated that the thyroid gland of hyperthyroid Graves' patients is stimulated by IgG(s) equivalent to at least 0.8 microU/mL bTSH (about 5 microU/mL hTSH) in vitro.

Hyperthyroid monkeys: a nonhuman primate model of experimental Graves' disease.

Graves' disease (GD) is a common organ-specific autoimmune disease with the prevalence between 0.5 and 2% in women. Several lines of evidence indicate that the shed A-subunit rather than the full-length thyrotropin receptor (TSHR) is the autoantigen that triggers autoimmunity and leads to hyperthyroidism. We have for the first time induced GD in female rhesus monkeys, which exhibit greater similarity to patients with GD than previous rodent models. After final immunization, the monkeys injected with adenovirus expressing the A-subunit of TSHR (A-sub-Ad) showed some characteristics of GD. When compared with controls, all the test monkeys had significantly higher TSHR antibody levels, half of them had increased total thyroxine (T4) and free T4, and 50% developed goiter. To better understand the underlying mechanisms, quantitative studies on subpopulations of CD4+T helper cells were carried out. The data indicated that this GD model involved a mixed Th1 and Th2 response. Declined Treg proportions and increased Th17:Treg ratio are also observed. Our rhesus monkey model successfully mimicked GD in humans in many aspects. It would be a useful tool for furthering our understanding of the pathogenesis of GD and would potentially shorten the distance toward the prevention and treatment of this disease in human.

Immune response of mice transgenic for human histocompatibility leukocyte Antigen-DR to human thyrotropin receptor-extracellular domain.

BACKGROUND: Hyperthyroidism of Graves' disease is caused by auto-antibodies to human thyrotropin receptor (hTSH-R). To elucidate important T-cell epitopes in TSH-R, we studied three models of immunity to TSH-R in mice. METHODS: Mice transgenic for histocompatibility leukocyte antigen DR3 or DR2 were immunized with cDNA for hTSH-R-extracellular domain (hTSH-R-ECD), or hTSH-R-ECD protein, or hTSH-R peptide epitopes. Proliferative responses of immunized splenocytes to epitopes derived from the hTSH-ECD sequence, anti-TSH-R antibody responses, serum thyroxine and TSH, and thyroid histology were recorded. RESULTS: DR3 mice responded to genomic immunization with proliferative responses to several epitopes, which increased in intensity and spread to include more epitopes, during a 6-week immunization program. DR2 transgenic mice developed weak proliferative responses. Both types of mice developed anti-TSH-R antibodies measured by enzyme-linked immunosorbent assay or TSH-binding inhibition assay in 16-60% of animals. There was evidence of weak thyroid stimulation in one group of animals. Immunization of DR3 transgenic mice to hTSH-R-ECD protein induced a striking response to an epitope with sequence ISRIYVSIDVTLQQLES (aa78-94). Immunization to peptides derived from the TSH-R-ECD sequence (including aa78-94) caused strong responses to the epitopes, and development of immune responses to several other nonoverlapping epitopes within the hTSH sequence (epitope spreading) and antibodies reacting with hTSH-R. This implies that immunization with hTSH-R epitopes produced immunity to mouse TSH-R. CONCLUSION: T-cell and B-cell responses to genetic immunization differ in DR3 and DR2 transgenic mice, and there is less genetic control of antibody than of T-cell responses. During both genomic and peptide epitope immunization there was evidence of epitope spreading during the immunization. Several functionally important epitopes are evident, especially aa78-94. However, if similar progressive epitope recruitment occurs in human disease, epitope-based therapy will be difficult to achieve.

Enhancement of experimental Graves' disease by intranasal administration of a T cell epitope of the thyrotropin receptor.

We previously showed that immunization of mice with murine fibroblasts transfected with the thyrotropin receptor (TSHR) and a murine major histocompatibility complex (MHC) class II molecule induces immune thyroid disease with the humoral and histological features of human Graves' disease in about 20% of mice. In this model, based on the proliferative response of T cells from hyperthyroid mice to a panel of overlapping TSHR peptides, we now demonstrate that TSHR 121-140 peptide contains an immunodominant T cell epitope. Supporting this conclusion, spleen cells from mice immunized with TSHR 121-140 peptide showed a strong proliferative response to fibroblasts transfected with the TSHR and a murine I-A(k) molecule, but not either alone. Also, intranasal administration of 100 mug of TSHR 121-140 peptide led to suppressed proliferative response of lymph node cells to the peptide. Interestingly, however, administration of this peptide enhanced, rather than suppressed, the frequency and severity of Graves' disease induced by the immunization of the fibroblasts transfected with the TSHR and a murine I-A(k) molecule. Spleen cells from hyperthyroid mice that were pretreated with intranasal peptide tended to produce lesser amounts of IL-4, IL-10 and IFN-gamma than those from normothyroid control mice. Although precise mechanisms of this enhancement remain to be determined, the results suggest that attempts to treat Graves' disease by intranasal administration of an immunodominant TSHR T cell epitope may aggravate, not prevent, the disease.

Adjuvant effects of cholera toxin b subunit on immune response to recombinant thyrotropin receptor in mice.

We had previously shown that BALB/c mice immunized with the extracellular domain of human thyrotropin receptor (ETSHR) developed moderate hyperthyroxinemia. The antibody responses in these mice were predominantly of the IgG1 subclass. Since cholera toxin B subunit (CT-B) has direct effects on the thyroid, and is known to activate B lymphocytes and cause enhanced IgG1 production, we tested the ability of CT-B to modulate the antibody response to ETSHR. CT-B is unique in that it not only elicits a strong immune response to itself, but more importantly, when given with other antigens acts as a potent adjuvant. In the present study, BALB/c mice given ETSHR with CFA or CT-B via ip route showed higher titers of antibodies to ETSHR when compared to mice similarly immunized with ETSHR alone, or with IFA. Antibodies in ETSHR+CT-B immunized mice were mostly of the IgG1 subclass and reacted predominantly with ETSHR peptides 1 (aa 22-41), 21 (aa 322-341), and 23 (352-371). In contrast, animals immunized with ETSHR+CFA showed IgG1, IgG2a and IgG2b responses and reacted with peptides 1 and 21. Furthermore, mice immunized with ETSHR along with CT-B showed significantly higher levels of thyrotropin (TSH) binding inhibitory immunoglobulins (TBII) compared to those that did not receive CT-B. None of the mice immunized with a control antigen showed antibody response to ETSHR. These results suggested that CT-B could enhance and modulate immune response to ETSHR.

Induction of experimental autoimmune Graves' disease in BALB/c mice.

We immunized BALB/c mice with M12 cells (H-2d) expressing either mouse (mM12 cells) or human thyrotropin receptor (TSHR) (hM12 cells). Immunized mice developed autoantibodies to native TSHR by day 90 and, by day 180, showed considerable stimulatory Ab activity as measured by their ability to enhance cAMP production (ranging from 6. 52 to 20.83 pmol/ml in different treatment groups relative to 1.83 pmol/ml for controls) by TSHR-expressing Chinese hamster ovary cells. These mice developed severe hyperthyroidism with significant elevations in both tetraiodothyronine and triiodothyronine hormones. Tetraiodothyronine levels in different experimental groups ranged from a mean of 8.66-12.4 microg/dl, relative to 4.8 microg/dl in controls. Similarly, mean triiodothyronine values ranged from 156.18 to 195.13 ng/dl, relative to 34.99 ng/dl for controls. Next, we immunized BALB/c mice with a soluble extracellular domain of human TSHR (TBP), or TBP expressed on human embryonic kidney cells (293 cells) (293-TBP cells). These mice showed severe hyperthyroidism in a manner very similar to that described above for mice immunized with the mouse TSHR or human TSHR, and exhibited significant weight loss, with average weight for treatment groups ranging from 20.6 to 21.67 g, while controls weighed 24.2 g. Early after onset of the disease, histopathological examination of thyroids showed enlargement of colloids and thinning of epithelial cells without inflammation. However, later during disease, focal necrosis and lymphocytic infiltration were apparent. Our results showed that conformationally intact ectodomain of TSHR is sufficient for disease induction. Availability of a reproducible model in which 100% of the animals develop disease should facilitate studies aimed at understanding the molecular pathogenesis of Graves' disease.

A novel murine model of Graves' hyperthyroidism with intramuscular injection of adenovirus expressing the thyrotropin receptor.

In this work we report a novel method to efficiently induce a murine model of Graves' hyperthyroidism. Inbred mice of different strains were immunized by i.m. injection with adenovirus expressing thyrotropin receptor (TSHR) or beta-galactosidase (1 x 10(11) particles/mouse, three times at 3-wk intervals) and followed up to 8 wk after the third immunization. Fifty-five percent of female and 33% of male BALB/c (H-2(d)) and 25% of female C57BL/6 (H-2(b)) mice developed Graves'-like hyperthyroidism with elevated serum thyroxine (T(4)) levels and positive anti-TSHR autoantibodies with thyroid-stimulating Ig (TSI) and TSH-binding inhibiting Ig (TBII) activities. In contrast, none of female CBA/J (H-2(k)), DBA/1J (H-2(q)), or SJL/J (H-2(s)) mice developed Graves' hyperthyroidism or anti-TSHR autoantibodies except SJL/J, which showed strong TBII activities. There was a significant positive correlation between TSI values and T(4) levels, but the correlations between T(4) and TBII and between TSI and TBII were very weak. TSI activities in sera from hyperthyroid mice measured with some chimeric TSH/lutropin receptors suggested that their epitope(s) on TSHR appeared similar to those in patients with Graves' disease. The thyroid glands from hyperthyroid mice displayed diffuse enlargement with hypertrophy and hypercellularity of follicular epithelia with occasional protrusion into the follicular lumen, characteristics of Graves' hyperthyroidism. Decreased amounts of colloid were also observed. However, there was no inflammatory cell infiltration. Furthermore, extraocular muscles from hyperthyroid mice were normal. Thus, the highly efficient means that we now report to induce Graves' hyperthyroidism in mice will be very useful for studying the pathogenesis of autoimmunity in Graves' disease.

Cytokines, IgG subclasses and costimulation in a mouse model of thyroid autoimmunity induced by injection of fibroblasts co-expressing MHC class II and thyroid autoantigens.

AKR/N mice injected with fibroblasts expressing MHC class II (RT4.15HP cells) and the TSH receptor (TSHR) develop antibodies similar to those in Graves' disease. We were unable to analyse the subclass of these antibodies because of unexpectedly high non-specific binding by ELISA or flow cytometry. The non-specific binding reflected generalized immune activation which occurred even when the fibroblasts did not express the TSHR. However, the IgG subclasses were determined for thyroid peroxidase (TPO) antibodies induced using TPO-expressing RT4.14HP cells and found to be IgG2a > IgG1. This Thl pattern is consistent with spontaneous secretion of interferon-gamma (but not IL-4 or IL-10) by splenocytes from injected mice. The Th1 bias was related to fibroblast injection because conventional immunization of the same mouse strain with purified TPO and adjuvant induced a Th2 response (IgG1 >> IgG2a). Further, untransfected fibroblasts themselves induced powerful, non-specific proliferative responses when used as antigen-presenting cells (APC) in vitro. Flow cytometry revealed that the RT4.15HP fibroblasts (and TSHR- and TPO-transfected derivatives) expressed B7-1. Unexpected constitutive expression of this key molecule may bypass the requirement for up-regulation of other costimulatory molecules involved in T cell stimulation. Our data support the concept that RT4.15HP fibroblasts present the TSHR (or TPO), at least for initiating the immune response. However, the accompanying generalized immune stimulation creates difficulties for analysis of TSHR-specific T and B lymphocytes. On the other hand, extension of the model to TPO, an easier antigen to study, will facilitate analysis of murine T cell responses likely to resemble those in human thyroid autoimmunity.

Prevention of autoantibody-mediated Graves'-like hyperthyroidism in mice with IL-4, a Th2 cytokine.

Graves' hyperthyroidism has long been considered to be a Th2-type autoimmune disease because it is directly mediated by autoantibodies against the thyrotropin receptor (TSHR). However, several lines of evidence have recently challenged this concept. The present study evaluated the Th1/Th2 paradigm in Graves' disease using a recently established murine model involving injection of adenovirus expressing the TSHR (AdCMVTSHR). Coinjection with adenovirus expressing IL-4 (AdRGDCMVIL-4) decreased the ratio of Th1/Th2-type anti-TSHR Ab subclasses (IgG2a/IgG1) and suppressed the production of IFN-gamma by splenocytes in response to TSHR Ag. Importantly, immune deviation toward Th2 was accompanied by significant inhibition of thyroid-stimulating Ab production and reduction in hyperthyroidism. However, in a therapeutic setting, injection of AdRGDCMVIL-4 alone or in combination with AdCMVTSHR into hyperthyroid mice had no beneficial effect. In contrast, coinjection of adenoviruses expressing IL-12 and the TSHR promoted the differentiation of Th1-type anti-TSHR immune responses as demonstrated by augmented Ag-specific IFN-gamma secretion from splenocytes without changing disease incidence. Coinjection of adenoviral vectors expressing IL-4 or IL-12 had no effect on the titers of anti-TSHR Abs determined by ELISA or thyroid-stimulating hormone-binding inhibiting Ig assays, suggesting that Ab quality, not quantity, is responsible for disease induction. Our observations demonstrate the critical role of Th1 immune responses in a murine model of Graves' hyperthyroidism. These data may raise a cautionary note for therapeutic strategies aimed at reversing Th2-mediated autoimmune responses in Graves' disease in humans.