BackgroundVariation in induced models of autoimmunity has been attributed to the housing environment and its effect on the gut microbiota. In Graves’ disease (GD), autoantibodies to the thyrotropin receptor (TSHR) cause autoimmune hyperthyroidism. Many GD patients develop Graves’ orbitopathy or ophthalmopathy (GO) characterized by orbital tissue remodeling including adipogenesis. Murine models of GD/GO would help delineate pathogenetic mechanisms, and although several have been reported, most lack reproducibility. A model comprising immunization of female BALBc mice with a TSHR expression plasmid using in vivo electroporation was reproduced in two independent laboratories. Similar orbital disease was induced in both centers, but differences were apparent (e.g., hyperthyroidism in Center 1 but not Center 2). We hypothesized a role for the gut microbiota influencing the outcome and reproducibility of induced GO.ResultsWe combined metataxonomics (16S rRNA gene sequencing) and traditional microbial culture of the intestinal contents from the GO murine model, to analyze the gut microbiota in the two centers. We observed significant differences in alpha and beta diversity and in the taxonomic profiles, e.g., operational taxonomic units (OTUs) from the genus Lactobacillus were more abundant in Center 2, and Bacteroides and Bifidobacterium counts were more abundant in Center 1 where we also observed a negative correlation between the OTUs of the genus Intestinimonas and TSHR autoantibodies. Traditional microbiology largely confirmed the metataxonomics data and indicated significantly higher yeast counts in Center 1 TSHR-immunized mice. We also compared the gut microbiota between immunization groups within Center 2, comprising the TSHR- or βgal control-immunized mice and naïve untreated mice. We observed a shift of the TSHR-immunized mice bacterial communities described by the beta diversity weighted Unifrac. Furthermore, we observed a significant positive correlation between the presence of Firmicutes and orbital-adipogenesis specifically in TSHR-immunized mice.ConclusionsThe significant differences observed in microbiota composition from BALBc mice undergoing the same immunization protocol in comparable specific-pathogen-free (SPF) units in different centers support a role for the gut microbiota in modulating the induced response. The gut microbiota might also contribute to the heterogeneity of induced response since we report potential disease-associated microbial taxonomies and correlation with ocular disease.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0478-4) contains supplementary material, which is available to authorized users.

Graves' disease (GD) is an autoimmune condition with the appearance of anti-TSH receptor (TSHR) autoantibodies in the serum. The consequence is the development of hyperthyroidism in most of the patients. In addition, in the most severe cases, patients can develop orbitopathy (GO), achropachy and dermopathy. The central role of the TSHR for the disease pathology has been well accepted. Therefore immunization against the TSHR is pivotal for the creation of in vivo models for the disease. However, TSHR is well preserved among the species and therefore the immune system is highly tolerant. Many differing attempts have been performed to break tolerance and to create a proper animal model in the last decades. The most successful have been achieved by introducing the human TSHR extracellular domain into the body, either by injection of plasmid or adenoviruses. Currently available models develop the whole spectrum of Graves' disease-autoimmune thyroid disease and orbitopathy and are suitable to study disease pathogenesis and to perform treatment studies. In recent publications new immunomodulatory therapies have been assessed and also diseaseprevention by inducing tolerance using small cyclic peptides from the antigenic region of the extracellular subunit of the TSHR.