Immunoglobulin heavy chain variable region and major histocompatibility region genes are linked to induced graves' disease in females from two very large families of recombinant inbred mice

A transgenic mouse that spontaneously develops pathogenic TSH receptor antibodies will facilitate study of antigen-specific immunotherapy for human Graves' disease

Graves' hyperthyroidism can be treated but not cured. Antigen-specific immunotherapy would accomplish this goal, for which purpose an animal model is an invaluable tool. Two types of animal models are available. First, pathogenic TSHR antibodies (TSHRAb) can be induced by injecting mice with fibroblasts co-expressing the human TSHR (hTSHR) and MHC class II, or in mammals using plasmid or adenovirus vectors encoding the hTSHR or its A-subunit. Second, a mouse model that spontaneously develops pathogenic TSHRAb resembling those in human disease was recently described. This outcome was accomplished by transgenic intrathyroidal expression of the hTSHR A-subunit in NOD.H2^h4 mice that are genetically predisposed to develop thyroiditis but, without the transgene, do not generate TSHRAb. Recently, novel approaches to antigen-specific immunotherapy have been tested, primarily in the induced model, by injecting TSHR A-subunit protein or cyclic TSHR peptides. T-cell tolerance has also been induced in "humanized" HLA-DR3 mice by injecting synthetic peptides predicted in silico to mimic naturally processed TSHR T-cell epitopes. Indeed, a phase 1 study based on the latter approach has been conducted in humans. In the spontaneous model (hTSHR/NOD.H2^h mice), injection of soluble or nanoparticle-bearing hTSHR A-subunits had the unwanted effect of exacerbating pathogenic TSHRAb levels. A promising avenue for tolerance induction, successful in other conditions and yet to be tested with the TSHR, involves encapsulating the antigen. In conclusion, these studies provide insight into the potential outcome of immunotherapeutic approaches and emphasize the importance of a spontaneous model to test future novel, antigen-specific immunotherapies for Graves' disease.

Thyroid Hemiagenesis in a Thyroiditis Prone Mouse Strain

BACKGROUND

Thyroid hemiagenesis, a rare congenital condition detected by ultrasound screening of the neck, is usually not manifested clinically in humans. This condition has been reported in mice with hypothyroidism associated with induced deficiency in paired box 8 and NK2 homeobox 1, sonic hedgehog, or T-box 1. Unexpectedly, we observed thyroid hemiagenesis in NOD.H2^h4 mice, an unusual strain that spontaneously develops iodide enhanced thyroid autoimmunity but remains euthyroid.

OBJECTIVES AND METHODS

First, to compare mice with thyroid hemiagenesis versus bilobed littermates for serum T4, autoantibodies to thyroglobulin (ELISA) and thyroid peroxidase (TPO; flow cytometry with eukaryotic cells expressing mouse TPO), gross anatomy, and thyroid histology; second, to estimate the percentage of mice with thyroid hemiagenesis in the NOD.H2^h4 mice we have studied over 6 years.

RESULTS

Thyroid hemiagenesis was observed in 3 of 1,025 NOD.H2^h4 mice (2 females, 1 male; 0.3$). Two instances of hemiagenesis were in wild-type females and one in a transgenic male expressing the human TSHR A-subunit in the thyroid. Two mice had very large unilobed glands, as in some human cases with this condition. Thyroid lymphocytic infiltration, serum T4, and the levels of thyroid autoantibodies were similar in mice with thyroid hemiagenesis and bilobed littermates.

CONCLUSIONS

Unlike hypothyroidism associated with hemiagenesis in transcription factor knockout mice, hemiagenesis in euthyroid NOD.H2^h4 mice occurs spontaneously and is phenotypically similar to that occasionally observed in humans.

Genes Outside the Major Histocompatibility Complex Locus Are Linked to the Development of Thyroid Autoantibodies and Thyroiditis in NOD.H2h4 Mice

Thyroiditis and autoantibodies to thyroglobulin (TgAb) and thyroid peroxidase (TPOAb) develop spontaneously in NOD.H2h4 mice, a phenotype enhanced by dietary iodine. NOD.H2h4 mice were derived by introducing the major histocompatibility class (MHC) molecule I-Ak from B10.A(4R) mice to nonobese diabetic (NOD) mice. Apart from I-Ak, the genes responsible for the NOD.H2h4 phenotype are unknown. Extending serendipitous observations from crossing BALB/c to NOD.H2h4 mice, thyroid autoimmunity was investigated in both genders of the F1, F2, and the second-generation backcross of F1 to NOD.H2h4 (N2). Medium-density linkage analysis was performed on thyroid autoimmunity traits in F2 and N2 progeny. TgAb develop before TPOAb and were measured after 8 and 16 weeks of iodide exposure; TPOAb and thyroiditis were studied at 16 weeks. TgAb, TPOAb, and thyroiditis, absent in BALB/c and F1 mice, developed in most NOD.H2h4 and in more N2 than F2 progeny. No linkages were observed in F2 progeny, probably because of the small number of autoantibody-positive mice. In N2 progeny (equal numbers of males and females), a chromosome 17 locus is linked to thyroiditis and TgAb and is suggestively linked to TPOAb. This locus includes MHC region genes from B10.A(4R) mice (such as I-Ak and Tnf, the latter involved in thyrocyte apoptosis) and genes from NOD mice such as Satb1, which most likely plays a role in immune tolerance. In conclusion, MHC and non-MHC genes, encoded within the chromosome 17 locus from both B10.A(4R) and NOD strains, are most likely responsible for the Hashimoto disease-like phenotype of NOD.H2h4 mice.

Certain HLA alleles are associated with stress-triggered Graves' disease and influence its course

There are no studies on HLA analysis in patients in whom Graves' disease (GD) hyperthyroidism has been preceded by ≥1 stressful event. The aim of the present study was to identify predisposing or protecting HLA alleles and their effects on the course of GD in this subset of patients. We performed serological HLA typing in 58 Caucasian patients with stress-related GD and in 130 matched healthy controls (HC). We also performed genomic HLA typing in 20/58 patients and in all HC. Five HLA alleles and three loci were more frequent in patients compared to HC: B8, Cw7, C*07, C*17, DR3, DR4, DRB1*04, and DQ2. In contrast, B14 was less frequent in patients than in HC. Depending on outcome after ATD withdrawal (remission, exacerbation on-ATD, relapse off-ATD), in patients, some alleles/loci were over-represented, while others were under-represented. Age, FT3, and FT4 fold increase over the upper normal limit at onset were different depending on the allele/locus carried. In GD patients with stress-triggered hyperthyroidism, HLA typing may be helpful in predicting the outcome of the disease after ATD withdrawal.

Animal models of Graves' disease and Graves' orbitopathy

PURPOSE OF REVIEW

The purpose of this article is to summarize the recent advances on experimental Graves' hyperthyroidism and orbitopathy as studied in two widely used mouse models, which involve repetitive genetic vaccinations using either adenovirus or in-vivo electroporation of the eukaryotic expression plasmid expressing the thyrotropin receptor (TSHR) as a vector.

RECENT FINDINGS

The models have been improved by using different types of antigens, including the holo receptor, the receptor A-subunit, an alternatively spliced form of variant receptor lacking a single leucine-rich repeat in the codomain, the receptors of human or mouse origin; different mice such as wild-type, TSHR knockout, TSHR transgenic and different inbred mice; and different immunization protocols. They are now useful for elucidating the pathogenic mechanisms of not only Graves' hyperthyroidism but also Graves' orbitopathy.

SUMMARY

This review summarizes the literature of mouse models of Graves' hyperthyroidism and orbitopathy published over the last 3 years.