Relationship between thyroid autoimmunity and Yersinia enterocolitica antibodies

Molecular Mechanisms in Autoimmune Thyroid Disease

The most common cause of acquired thyroid dysfunction is autoimmune thyroid disease, which is an organ-specific autoimmune disease with two presentation phenotypes: hyperthyroidism (Graves-Basedow disease) and hypothyroidism (Hashimoto’s thyroiditis). Hashimoto’s thyroiditis is distinguished by the presence of autoantibodies against thyroid peroxidase and thyroglobulin. Meanwhile, autoantibodies against the TSH receptor have been found in Graves-Basedow disease. Numerous susceptibility genes, as well as epigenetic and environmental factors, contribute to the pathogenesis of both diseases. This review summarizes the most common genetic, epigenetic, and environmental mechanisms involved in autoimmune thyroid disease.

Mycobacterium avium subsp. paratuberculosis and Hashimoto’s thyroiditis: Is MAP the trigger?

Hashimoto’s thyroiditis (HT) is an autoimmune disorder of the thyroid gland that can cause hypothyroidism. As HT is a multifactorial disorder, activation of immune responses in genetically predisposed individuals exposed to some environmental factors can contribute to it. Microorganisms, as environmental factors, including Mycobacterium avium ssp. paratuberculosis (MAP) by molecular mimicry, can be important in this autoimmune disorder. This study aimed to investigate the association between MAP and HT. This case–control study included 110 participants consisting of 60 HT patients and 50 healthy controls (HCs). Blood samples were collected. Nested PCR of the IS900 gene determined the presence of MAP DNA. The enzyme-linked immunosorbent assay (ELISA) was designed to identify antibodies (Abs) against the MAP3865c epitope, which has a homologous sequence with ZnT8 in the sera. The demographic information of all participants was recorded. Anti-TG, anti-TPO, TSH, anemia, and ruminant exposure were higer in HT patients than in the HCs (p < 0.05). MAP IS900 was detected significantly more in the patients (46.6% consisting of 30, 8.3, and 8.3% in clinical, subclinical, and unknown) than in the HCs (14%). The sera showed a remarkable frequency of reactivity against MAP3865c in the patients (38.3%) in comparison to the HCs (10%) (p = 0.0001). Furthermore, a significantly higher rate of livestock contact and traditional dairy consumption was found in individuals with MAP or anti-MAP3865c Abs positive result (p < 0.05). This study suggests a possible link between MAP and HT. These findings indicated that MAP frequency was not statistically different in the severity of HT and its shift into the clinical and subclinical forms; therefore, it could be assumed that MAPs are the initiators of the process. The results imply on a possible zoonosis transmission route of MAP from livestock products to humans. Further research is needed to confirm these results in larger groups of HT patients.

Genetics, Epigenetics, Cellular Immunology, and Gut Microbiota: Emerging Links With Graves' Disease

Graves’ disease (GD) is a well-known organ-specific autoimmune disease characterized by hyperthyroidism, goiter, and exophthalmos. The incidence of GD is approximately 2.0–3.0% in China and 0.5–2.0% in Western countries. Due to the complex pathogenesis and etiology of GD, current treatment methods have great side effects that seriously endanger human health. Therefore, it is particularly important to understand the pathogenesis of GD. Various studies have shown that genetics, epigenetics, cellular immunology, and gut microbiota are all involved in the development of GD. Genetically, CD25 gene and VDR gene polymorphisms are involved in the development of GD by increasing the ratio of Th17/Treg cells. Epigenetically, miR-23a-3p and lncRNA-MEG3 lead to Th17/Treg imbalance and participate in the progression of GD. Moreover, commensal microbe deletion can disrupt Th17/Treg balance and participate in the occurrence of GD. The imbalance of Th17/Treg cells induced by genetics, epigenetics, and gut microbiota plays a vital role in the pathogenesis of GD. Therefore, this article reviews the role of genetics, epigenetics, cellular immunology, and gut microbiota in the pathogenic mechanism of GD. This may lead to the development of novel therapeutic strategies and providing promising therapeutic targets.

Granulomatosis with polyangiitis: Possible endocrine manifestations

Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis, is a necrotizing vasculitis of small and medium-sized blood vessels characterized by diffuse inflammation of vascular structures and perivascular and extravascular granulomatosis. In its systemic form, GPA predominantly affects the ear, nose and throat, with lung and kidney involvement with typically rapidly progressive necrotizing glomerulonephritis with extracapillary crescents, while the absence of kidney damage at the time of diagnosis is defined as a limited form of GPA with a more favorable prognosis (1, 2). Antineutrophil cytoplasmic antibodies (c-ANCA) with specificity for proteinase 3 (PR3) represent a biochemical diagnostic criterion. They are detected in 90% of generalized forms and in about 50% of limited forms of granulomatosis with polyangiitis (1, 2). In the absence of treatment, GPA is a disease of progressive evolution. Systemic corticosteroid therapy and immunosuppressive therapy significantly changed the prognostic aspect of the disease. Only a few sporadic observations have been published on endocrine disorders associated with GPA. We present a case of a man, 39 years old, with Wegener's granulomatosis who developed autoimmune thyroiditis 8 years after the initial diagnosis.

Associations of Yersinia Enterocolitica Infection with Autoimmune Thyroid Diseases: A Systematic Review and Meta-Analysis

INTRODUCTION

Yersinia enterocolitica infection is reportedly associated with the development of autoimmune thyroid diseases (AITD). However, evidence that such infection can lead to AITD is controversial. Thus, this study was aimed to investigate the associations of Y. enterocolitica infection with AITD.

METHODS

A meta-analysis was performed using PubMed, Web of Science, Embase and Cochrane library to identify relevant studies. The odds ratios (OR) and associated 95% confidence intervals [CI] were obtained. Data were analyzed by STATA 13.0 (Stata Corporation, College Station, TX, USA).

RESULTS

Of 215 articles identified, 8 studies with a total of 1490 participants met the criteria and were included in the meta-analysis. There was a significant association between Y. enterocolitica positivity and AITD (OR: 4.31 [CI 95%: 1.81-10.07], P-value: 0.00). According to the subgroup analysis, Y. enterocolitica infection statistically increased the risk of Graves' disease (GD) (OR: 6.12, [CI 95%: 3.71-10.10], P-value: 0.00). Likewise, the pooled OR of association between Y. enterocolitica positivity and hashimoto's thyroiditis (HT) was 2.84 (CI 95%: 0.71-11.25, P-value: 0.1).

CONCLUSION

The current studies suggest that Y. enterocolitica may be associated with the development of AITD. Further study is needed to explore the underlying mechanisms.

Microorganisms associated to thyroid autoimmunity

Autoimmune thyroid diseases are a group of diseases characterized by a dysfunction of the immune system concerning the thyroid gland, associated with hypothyroidism or hyperthyroidism. The thyroid gland autoimmunity has been recognized as multifactorial. It has been reported that microorganisms may play a role on the pathogenesis of Hashimoto's thyroiditis and Graves´ disease. These could explain the high incidence of the autoimmune thyroid diseases. Helicobacter Pylori (H. pylori) and Hepatitis C virus (HCV) are the microorganisms in which the association with autoimmune thyroid diseases is clearer. The pathophysiologic mechanisms are still not well defined. For H. pylori, molecular mimicry has been the most accepted mechanism. It has been proposed Hepatitis C virus as the trigger of the thyroid autoimmunity by exacerbating the production of thyroid auto-antibodies, while some mention that the real factor that triggers the thyroid autoimmunity is the treatment with Interferon alpha (IFN-alpha) by upregulating MHC class I and inducing ligation of CD40+ cells to thyrocytes. Other microorganisms such as Toxoplasma gondii, Human Immunodeficiency virus, Herpes virus and others have reported information about their association with thyroid autoimmune diseases There are no proposals on how these last microorganisms induce thyroid autoimmunity. There is still a lack of evidence on this topic. Further research must be done to determine the interaction of these microorganisms and the best way to manage these patients.

Chemically or surgically induced thyroid dysfunction altered gut microbiota in rat models

Thyroid hormones are essential for the regulation of energy homeostasis and metabolic processes. However, the relationship between thyroid function and host gut microbial communities is not properly understood. To determine whether and how gut microbiota is associated with thyroid function, metagenomics analysis of the bacterial population in fecal samples of rat models of hyperthyroidism (induced by levothyroxine) and hypothyroidism (induced by propylthiouracil or thyroidectomy) was conducted through 16S rRNA gene sequencing. Our results revealed that all thyroid dysfunction models were definitely established and gut microbial composition varied according to different thyroid functional status. The relative abundance of Ruminococcus was significantly higher in the hyperthyroidism group (HE) vs both the normal and hypothyroidism groups (HO) while S24-7 was significantly higher in the HO group. The population of Prevotellaceae and Prevotella were significantly lower in the HO group vs the normal. Firmicutes and Oscillospira were significantly higher in the SHO (surgery-induced hypothyroidism) group, while Prevotellaceae and Prevotella showed lower abundance in the SHO group than the SHAM group. Present results suggest that thyroid functions may have the potential to influence the profile of gut microbiota and could be used as foundation to investigate interaction mechanism between thyroid and gut microbiome.

Alterations in the intestinal microbiota of patients with severe and active Graves' orbitopathy: a cross-sectional study

BACKGROUND

The intestinal microbiota was linked to autoimmune diseases. Graves' orbitopathy (GO) is an autoimmune disease that is usually associated with Graves' disease. However, information on the microbiome of GO patients is yet lacking.

OBJECTIVES

To investigate whether GO patients differ from healthy controls in the fecal microbiota.

DESIGN

A cross-sectional study.

SETTING

33 patients with severe and active GO and 32 healthy controls of Han nationality were enrolled between March 2017 and March 2018.

METHODS

The Gut microbial communities of the fecal samples of GO patients and healthy controls were analyzed and compared by 16S rRNA gene sequencing.

RESULTS

Community diversity (Simpson and Shannon) was significantly reduced in fecal samples from patients with GO as compared to controls (p < 0.05). The similarity observed while assessing the community diversity (PCoA) proposed that the microbiota of patients with GO differ significantly from those of controls (p < 0.05). At the phyla levels, the proportion of Bacteroidetes increased significantly in patients with GO (p < 0.05), while at the genus and species levels, significant differences were observed in the bacterial profiles between the two groups (p < 0.05).

LIMITATIONS

Single-centered study design and limited fecal samples.

CONCLUSIONS

The present study indicated distinctive features of the gut microbiota in GO patients. The study provided evidence for further exploration in the field of intestinal microbiota with respect to the diagnosis and treatment of GO patients by modifying the microbiota profile.

Does the Epstein-Barr Virus Play a Role in the Pathogenesis of Graves' Disease?

Graves’ disease (GD) it the most common chronic organ-specific thyroid disorder without a fully recognized etiology. The pathogenesis of the disease accounts for an interaction between genetic, environmental, and immunological factors. The most important environmental factors include viral and bacterial infections. The Epstein-Barr virus (EBV) is one of the most common latent human viruses. Literature has suggested its role in the development of certain allergic and autoimmune diseases. EBV also exhibits oncogenic properties. The aim of the study was to analyze and compare the presence of EBV DNA in peripheral blood mononuclear cells (PBMCs) in patients with newly recognized GD and to find a correlation between EBV infection and the clinical picture of GD. The study included 39 untreated patients with newly diagnosed GD and a control group of 20 healthy volunteers who were gender and age matched. EBV DNA was detected with reverse transcription polymerase chain reaction (RT PCR) assay. The studies showed a significantly higher incidence of EBV copies in PBMCs among GD patients compared to the control group. Whereas, no significant correlations were found between the incidence of EBV copies and the evaluated clinical parameters. Our results suggest a probable role of EBV in GD development. EBV infection does not affect the clinical picture of Graves’ disease.

The microbiota and autoimmunity: Their role in thyroid autoimmune diseases

Since the 1970s, the role of infectious diseases in the pathogenesis of Graves' disease (GD) has been an object of intensive research. The last decade has witnessed many studies on Yersinia enterocolitica, Helicobacter pylori and other bacterial organisms and their potential impact on GD. Retrospective, prospective and molecular binding studies have been performed with contrary outcomes. Until now it is not clear whether bacterial infections can trigger autoimmune thyroid disease. Common risk factors for GD (gender, smoking, stress, and pregnancy) reveal profound changes in the bacterial communities of the gut compared to that of healthy controls but a pathogenetic link between GD and dysbiosis has not yet been fully elucidated. Conventional bacterial culture, in vitro models, next generation and high-throughput DNA sequencing are applicable methods to assess the impact of bacteria in disease onset and development. Further studies on the involvement of bacteria in GD are needed and may contribute to the understanding of pathogenetic processes. This review will examine available evidence on the subject.

Autoimmune Thyroiditis and Glomerulopathies

Autoimmune thyroiditis (AIT) is generally associated with hypothyroidism. It affects ~2% of the female population and 0.2% of the male population. The evidence of thyroid function- and thyroid autoantibody-unrelated microproteinuria in almost half of patients with AIT and sometimes heavy proteinuria as in the nephrotic syndrome point to a link of AIT with renal disease. The most common renal diseases observed in AIT are membranous nephropathy, membranoproliferative glomerulonephritis, minimal change disease, IgA nephropathy, focal segmental glomerulosclerosis, antineutrophil cytoplasmic autoantibody (ANCA) vasculitis, and amyloidosis. Different hypotheses have been put forward regarding the relationship between AIT and glomerulopathies, and several potential mechanisms for this association have been considered. Glomerular deposition of immunocomplexes of thyroglobulin and autoantibodies as well as the impaired immune tolerance for megalin (a thyrotropin-regulated glycoprotein expressed on thyroid cells) are the most probable mechanisms. Cross-reactivity between antigens in the setting of genetic predisposition has been considered as a potential mechanism that links the described association between ANCA vasculitis and AIT.

Tracking microbial colonization in fecal microbiota transplantation experiments via genome-resolved metagenomics

BACKGROUND

Fecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridium difficile infection and shows promise for treating other medical conditions associated with intestinal dysbioses. However, we lack a sufficient understanding of which microbial populations successfully colonize the recipient gut, and the widely used approaches to study the microbial ecology of FMT experiments fail to provide enough resolution to identify populations that are likely responsible for FMT-derived benefits.

METHODS

We used shotgun metagenomics together with assembly and binning strategies to reconstruct metagenome-assembled genomes (MAGs) from fecal samples of a single FMT donor. We then used metagenomic mapping to track the occurrence and distribution patterns of donor MAGs in two FMT recipients.

RESULTS

Our analyses revealed that 22% of the 92 highly complete bacterial MAGs that we identified from the donor successfully colonized and remained abundant in two recipients for at least 8 weeks. Most MAGs with a high colonization rate belonged to the order Bacteroidales. The vast majority of those that lacked evidence of colonization belonged to the order Clostridiales, and colonization success was negatively correlated with the number of genes related to sporulation. Our analysis of 151 publicly available gut metagenomes showed that the donor MAGs that colonized both recipients were prevalent, and the ones that colonized neither were rare across the participants of the Human Microbiome Project. Although our dataset showed a link between taxonomy and the colonization ability of a given MAG, we also identified MAGs that belong to the same taxon with different colonization properties, highlighting the importance of an appropriate level of resolution to explore the functional basis of colonization and to identify targets for cultivation, hypothesis generation, and testing in model systems.

CONCLUSIONS

The analytical strategy adopted in our study can provide genomic insights into bacterial populations that may be critical to the efficacy of FMT due to their success in gut colonization and metabolic properties, and guide cultivation efforts to investigate mechanistic underpinnings of this procedure beyond associations.

Relapse prediction in Graves´ disease: Towards mathematical modeling of clinical, immune and genetic markers

PROBLEM

Graves' disease (GD) is an important and prevalent thyroid autoimmune disorder. Standard therapy for GD consists of antithyroid drugs (ATD) with treatment periods of around 12 months but relapse is frequent. Since predictors for relapse are difficult to identify the individual decision making for optimal treatment is often arbitrary.

METHODS

After reviewing the literature on this topic we summarize important factors involved in GD and with respect to their potential for relapse prediction from markers before and after treatment. This information was used to design a mathematical model integrating thyroid hormone parameters, thyroid size, antibody titers and a complex algorithm encompassing genetic predisposition, environmental exposures and current immune activity in order to arrive at a prognostic index for relapse risk after treatment.

CONCLUSION

In the search for a tool to analyze and predict relapse in GD mathematical modeling is a promising approach. In analogy to mathematical modeling approaches in other diseases such as viral infections, we developed a differential equation model on the basis of published clinical trials in patients with GD. Although our model needs further evaluation to be applicable in a clinical context, it provides a perspective for an important contribution to a final statistical prediction model.

Fecal Microbiota Transplantation and Its Usage in Neuropsychiatric Disorders

Fecal microbiota transplantation has a 1700-year history. This forgotten treatment method has been put into use again during the last 50 years. The interest in microbiota-gut-brain axis and fecal microbiota transplantation is rapidly increasing. New evidence is obtained in the etiopathogenesis of neuropsychiatric disorders. There is a large number of experimental and clinical researches in the field of gut-brain axis. There is limited information on fecal microbiota transplantation. Despite this, initial results are promising. It is commonly used in the treatment of gastrointestinal diseases such as Clostridium difficile infection, Crohn’s disease, ulcerative colitis. It is also experimentally used in the treatment of metabolic and autoimmune diseases. There are case reports that it is effective in the treatment of autism, Parkinson’s disease, multiple sclerosis, chronic fatigue syndrome and irritable bowel syndrome. Its implementation is easy, and it is a cheap and reliable treatment method. However, the long-term risks are unknown. Additionally, standard application protocols have not yet been established. There are a lot of questions to be answered. A university in Turkey has got official permission this year, and started to apply fecal microbiota transplantation. In this review, neuropsychiatric areas of use of fecal microbiota transplantation have been discussed in the light of the current information.

Thyroid nodules and thyroid autoimmunity in the context of environmental pollution

Evidence suggests that in most industrialized countries autoimmune disorders, including chronic lymphocytic thyroiditis, are increasing. This increase parallels the one regarding differentiated thyroid cancer, the increment of which is mainly due to the papillary histotype. A number of studies have pointed to an association between chronic lymphocytic thyroiditis and differentiated thyroid cancer. The upward trend of these two thyroid diseases is sustained by certain environmental factors, such as polluting substances acting as endocrine disrupting chemicals. Herein we will review the experimental and clinical literature that highlights the effects of environmental and occupational exposure to polluting chemicals in the development of autoimmune thyroid disease or differentiated thyroid cancer. Stakeholders, starting from policymarkers, should become more sensitive to the consequences for the thyroid resulting from exposure to EDC. Indeed, the economic burden resulting from such consequences has not been quantified thus far.

Fecal microbiota transplantation broadening its application beyond intestinal disorders

Intestinal dysbiosis is now known to be a complication in a myriad of diseases. Fecal microbiota transplantation (FMT), as a microbiota-target therapy, is arguably very effective for curing Clostridium difficile infection and has good outcomes in other intestinal diseases. New insights have raised an interest in FMT for the management of extra-intestinal disorders associated with gut microbiota. This review shows that it is an exciting time in the burgeoning science of FMT application in previously unexpected areas, including metabolic diseases, neuropsychiatric disorders, autoimmune diseases, allergic disorders, and tumors. A randomized controlled trial was conducted on FMT in metabolic syndrome by infusing microbiota from lean donors or from self-collected feces, with the resultant findings showing that the lean donor feces group displayed increased insulin sensitivity, along with increased levels of butyrate-producing intestinal microbiota. Case reports of FMT have also shown favorable outcomes in Parkinson’s disease, multiple sclerosis, myoclonus dystonia, chronic fatigue syndrome, and idiopathic thrombocytopenic purpura. FMT is a promising approach in the manipulation of the intestinal microbiota and has potential applications in a variety of extra-intestinal conditions associated with intestinal dysbiosis.

Breaking tolerance to thyroid antigens: changing concepts in thyroid autoimmunity

Thyroid autoimmunity involves loss of tolerance to thyroid proteins in genetically susceptible individuals in association with environmental factors. In central tolerance, intrathymic autoantigen presentation deletes immature T cells with high affinity for autoantigen-derived peptides. Regulatory T cells provide an alternative mechanism to silence autoimmune T cells in the periphery. The TSH receptor (TSHR), thyroid peroxidase (TPO), and thyroglobulin (Tg) have unusual properties ("immunogenicity") that contribute to breaking tolerance, including size, abundance, membrane association, glycosylation, and polymorphisms. Insight into loss of tolerance to thyroid proteins comes from spontaneous and induced animal models: 1) intrathymic expression controls self-tolerance to the TSHR, not TPO or Tg; 2) regulatory T cells are not involved in TSHR self-tolerance and instead control the balance between Graves' disease and thyroiditis; 3) breaking TSHR tolerance involves contributions from major histocompatibility complex molecules (humans and induced mouse models), TSHR polymorphism(s) (humans), and alternative splicing (mice); 4) loss of tolerance to Tg before TPO indicates that greater Tg immunogenicity vs TPO dominates central tolerance expectations; 5) tolerance is induced by thyroid autoantigen administration before autoimmunity is established; 6) interferon-α therapy for hepatitis C infection enhances thyroid autoimmunity in patients with intact immunity; Graves' disease developing after T-cell depletion reflects reconstitution autoimmunity; and 7) most environmental factors (including excess iodine) "reveal," but do not induce, thyroid autoimmunity. Micro-organisms likely exert their effects via bystander stimulation. Finally, no single mechanism explains the loss of tolerance to thyroid proteins. The goal of inducing self-tolerance to prevent autoimmune thyroid disease will require accurate prediction of at-risk individuals together with an antigen-specific, not blanket, therapeutic approach.

Associations of Helicobacter pylori infection and cytotoxin-associated gene A status with autoimmune thyroid diseases: a meta-analysis

BACKGROUND

Helicobacter pylori infection is reportedly associated with extradigestive diseases such as immune thrombocytopenic purpura and coronary heart disease. The risk factors for autoimmune thyroid diseases (ATDs) remain largely unknown, and whether H. pylori infection is associated with ATDs is still controversial. The aim of this meta-analysis was to determine the association between H. pylori infection and ATDs.

METHODS

Studies comparing the prevalence rate of H. pylori infection in patients with ATDs and healthy controls, published in English, were identified through a systematic search in MEDLINE and EMBAS up to June 2012. Serological or nonserological tests were used to confirm H. pylori infection and the presence of cytotoxin-associated gene A (CagA) antigens. The odds ratios (OR) and associated 95% confidence intervals [CI] were obtained.

RESULTS

Seven studies involving a total of 862 patients met the inclusion criteria and thus were included in our meta-analysis. Overall, H. pylori infection was associated with ATDs (OR 1.92 [CI 1.41-2.61]); the association was significant for Graves' disease (OR 4.35 [CI 2.48-7.64]) but not for Hashimoto's thyroiditis (OR 1.45 [CI 0.92-2.26], p=0.11). No association was observed in the subanalysis of studies using only enzyme-linked immunosorbent assay to detect H. pylori infection (OR 1.38 [CI 0.86-2.19], p=0.18). Five of the seven articles reported the association of CagA seroprevalence and ATDs. CagA seropositivity significantly increased the risk for ATDs by 2.24-fold [CI 1.06-4.75].

CONCLUSIONS

Both the prevalence of H. pylori infection and the seroprevalence of CagA-positive strains are associated with ATDs. These findings suggest that H. pylori infection potentially plays a part in the development of ATDs.

Prevalence of thyroid autoimmunity in patients with spondyloarthropathies

OBJECTIVE

To evaluate the prevalence of chronic autoimmune thyroiditis or Hashimoto's thyroiditis (HT) in a group of patients with spondyloarthritis (SpA).

METHODS

We evaluated serum levels of thyroid-stimulating hormone, free triiodothyronine, and free thyroxine, and titers of antithyroglobulin and antithyroid peroxidase (anti-TPO) antibodies in 357 consecutive patients with SpA. We also recruited 318 healthy age-matched controls. Ultrasonography of the thyroid gland was performed in all subjects and rheumatic activity was evaluated.

RESULTS

Indices of thyroid autoimmunity were significantly more frequent in patients with SpA than in controls (24.09% vs 10.69%, respectively; p < 0.05). In the SpA group, a higher prevalence of HT was found in patients with an active disease than in those with low-moderate disease levels. Also in the SpA group, patients with a disease duration > 2 years had a higher prevalence of HT and anti-TPO antibodies positivity than patients with a disease duration ≤ 2 years. Ultrasonography detected a significantly higher frequency of thyroid nodules and hypoechoic pattern in patients with SpA than in controls. Among patients with SpA, HT and anti-TPO antibodies positivity were significantly more frequent in patients with peripheral involvement (68.6%) than in patients with axial involvement (31.4%; p < 0.05).

CONCLUSION

Our study shows a significantly higher prevalence of thyroid autoimmunity in patients with SpA as compared to controls. Thyroiditis occurs more frequently in patients with longer disease duration and active rheumatic disease. We suggest that thyroid function tests be part of the clinical evaluation in patients with SpA.

No causal relationship between Yersinia enterocolitica infection and autoimmune thyroid disease: evidence from a prospective study

The objective of this study was to evaluate prospectively the relationship between Yersinia enterocolitica (YE) infection and the development of overt autoimmune hypo- or hyperthyroidism (study A) and the de novo occurrence of thyroid antibodies (study B). This was a prospective cohort study of 790 euthyroid women who were first- or second-degree relatives of autoimmune thyroid disease (AITD) patients. Follow-up was 5 years, with annual assessments. Study A was a nested case-control study in which YE serological status was measured between cases {subjects who developed overt hypothyroidism [thyroid stimulating hormone (TSH) > 5·7 mU/l and free T4 (FT4) < 9·3 pmol/l] or overt hyperthyroidism (TSH < 0·4 mU/l and FT4 > 20·1 pmol/l)} and matched controls. For study B, 388 euthyroid women without thyroid antibodies at baseline were enrolled. The YE serological status was compared between subjects who developed thyroid peroxidase (TPO)-antibodies and/or thyroglobulin (Tg)-antibodies at 4-year follow-up and those who remained negative. For study A, the proportion of subjects positive for Yersinia enterocolitica outer membrane protein (YOP) immunoglobulin (Ig)G or YOP IgA did not differ between cases and controls at baseline. One year before the development of overt hypo- or hyperthyroidism, the proportion of subjects with YOP IgG was not different between cases and controls, but YOP IgA were less prevalent in cases. For study B, de novo occurrence of TPO (or TPO-antibodies and/or Tg-antibodies) did not differ between subjects in whom YOP IgG were positive or negative at baseline. Neither persistence nor emergence of YOP IgG at 4-year follow-up was associated with the occurrence of TPO-antibodies or Tg-antibodies. Similar results were observed with respect to YOP IgA. YE infection does not contribute to an increased risk of thyroid autoimmunity.

Hepatitis C and interferon induced thyroiditis

Autoimmune thyroid diseases (AITDs) are complex diseases that develop as a result of interactions between genetic, epigenetic, and environmental factors. Significant progress has been made in our understanding of the genetic and environmental triggers contributing to AITD. The major environmental triggers of AITD include iodine, smoking, medications, pregnancy, and possibly stress. In this review we will focus on two well-documented environmental triggers of AITD, hepatitis C virus (HCV) infection and interferon alpha (IFNa) therapy. Chronic HCV infection has been shown to be associated with increased incidence of clinical and subclinical autoimmune thyroiditis (i.e. the presence of thyroid antibodies in euthyroid subjects). Moreover, IFNa therapy of chronic HCV infection is associated with subclinical or clinical thyroiditis in up to 40% of cases which can be autoimmune, or non-autoimmune thyroiditis. In some cases interferon induced thyroiditis (IIT) in chronic HCV patients may result in severe symptomatology necessitating discontinuation of therapy. While the epidemiology and clinical presentation of HCV and interferon induced thyroiditis have been well characterized, the mechanisms causing these conditions are still poorly understood.

Identification of outer membrane porin f protein of Yersinia enterocolitica recognized by antithyrotopin receptor antibodies in Graves' disease and determination of its epitope using mass spectrometry and bioinformatics tools

CONTEXT

In addition to genetic susceptibility, Yersinia enterocolitica (YE) infection played an important causative role in the pathogenesis of Graves' disease (GD) through molecular mimicry. However, the specific YE proteins and epitopes recognized by anti-TSH receptor (TSHR) autoantibodies (TRAb) have not been fully clarified, resulting in conflicting results from clinical research.

OBJECTIVE

Our aim was to explore the roles of YE in the pathogenesis of GD and identify the YE proteins and epitopes that are similar to the TSHR and are recognized by TRAb.

DESIGN

Assays of YE antibodies, TRAb, thyroglobulin antibodies, and thyroid microsomal antibodies as well as cross-absorption and two-way immunodiffusion were performed in patients with GD. Using mass spectrometry and the bioinformatics tools of protein structure modeling and epitope prediction, we identified the YE protein and its epitope, which was recognized by TRAb and was similar to TSHR.

RESULTS

Our study demonstrated for the first time that the YE protein outer membrane porin F protein (ompF) shared cross-immunogenicity with a leucine-rich domain of TSHR. The epitope recognized by antihuman TSHR antibody is located within the ompF region of amino acids 190-197, and the polyantibody against ompF protein showed TSAb activity.

CONCLUSIONS

Our results suggest that YE ompF is involved in the production of TRAb and the pathogenesis of GD through molecular mimicry. These findings are potentially important for understanding the role molecular mimicry plays in the disturbance of immune tolerance and the induction of autoimmunity to the TSHR.

Hashimoto's thyroiditis: TGAb, TPOAb, TRAb and recovery from hypothyroidism

Hashimoto described four patients with goiter. The histology of the goiter was characterized by diffuse lymphocytic infiltration, fibrosis and epithelial cell destruction. Thyroglobulin antibody (TGAb) and thyroid peroxidase antibody (TPOAb) have been used to diagnose Hashimoto's thyroiditis. Patients with positive TGAb and/or TPOAb have been assumed to have Hashimoto's thyroiditis. Approximately 10% of those with positive TGAb and/or TPOAb have hypothyroidism. There are two types of autoimmune thyroiditis: goitrous Hashimoto's thyroiditis and atrophic thyroiditis. The latter patients have blocking antibody (thyroid-stimulating hormone [TSH]-stimulation blocking antibody [TSBAb]). TSBAb is a TSH-receptor antibody (TRAb). TSBAb causes thyroid atrophy and hypothyroidism. TGAb and/or TPOAb do not necessarily cause hypothyroidism. Hypothyroid patients with Hashimoto's thyroiditis usually receive life-long l-thyroxine therapy. However, spontaneous recovery from hypothyroidism has been reported. Patients who had Hashimoto's hypothyroidism and then Graves' hyperthyroidism (and vice versa), have also been reported. Hashimoto's hypothyroidism and Graves' hyperthyroidism could be the opposite spectrums of one disease.

The etiology of autoimmune thyroid disease: a story of genes and environment

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and Hashimoto's thyroiditis (HT) are prevalent autoimmune diseases, affecting up to 5% of the general population. Autoimmune thyroid diseases arise due to complex interactions between environmental and genetic factors. Significant progress has been made in our understanding of the genetic and environmental triggers contributing to AITD. However, the interactions between genes and environment are yet to be defined. Among the major AITD susceptibility genes that have been identified and characterized is the HLA-DR gene locus, as well as non-MHC genes including the CTLA-4, CD40, PTPN22, thyroglobulin, and TSH receptor genes. The major environmental triggers of AITD include iodine, medications, infection, smoking, and possibly stress. Recent data on the genetic predisposition to AITD lead to novel putative mechanisms by which the genetic-environmental interactions may lead to the development of thyroid autoimmunity.

Autoimmune thyroid diseases in a large group of Hungarian patients with primary Sjögren's syndrome

BACKGROUND

Previous studies on relatively small populations of patients with primary Sjögren's syndrome (pSS) suggested an association between pSS and Hashimoto's thyroiditis (HT). As some findings in the literature regarding the relationship between pSS and thyroid disease are contradictory, and there is little information on the sequence of pSS and HT, we conducted a study with a population of patients with pSS that was about three times larger than previously studied populations. Our objective was to determine the prevalence of HT and Graves' disease (GD) in patients with pSS and to assess the sequence of pSS and autoimmune thyroid diseases.

METHODS

A total of 479 patients with pSS were retrospectively studied. Thyroid ultrasound and scintigraphy were performed, and serum thyrotropin, free triiodothyronine, free thyroxine, antithyroid peroxidase antibody (TPOAb), and anti-thyroglobulin autoantibody (TgAb) measurements were carried out. Solitary thyroid nodules were investigated by fine-needle aspiration biopsy.

RESULTS

Thyroid dysfunction was found in 95 patients (21.25%). Thirty of these patients had HT and 18 had GD. HT predated pSS in eight patients, developed at approximately the same time in seven patients, and followed pSS in 15 patients. Almost all (90%) patients with HT had persistently elevated serum TgAb or TPOAb titers.

CONCLUSIONS

An association between HT and pSS was found based on the fact that the frequency of HT was greater among pSS patients (6.26%) than in the general population (1-2%). In contrast, no association between GD and pSS was found. We noted that both HT and GD can appear either before or after the onset of pSS. Since most cases of pSS predate the appearance of autoimmune thyroid diseases it is important to determine if pSS is a predisposing factor for the development of autoimmune thyroiditis.

Infections and autoimmunity: a panorama

For more than 2,000 years, it was thought that malignant spirits caused diseases. By the end of nineteenth century, these beliefs were displaced by more modern concepts of disease, namely, the formulation of the “germ theory,” which asserted that bacteria or other microorganisms caused disease. With the emergence of chronic degenerative and of autoimmune diseases in the last century, the causative role of microorganisms has been intensely debated; however, no clear explanatory models have been achieved. In this review, we examine the current available literature regarding the relationships between infections and 16 autoimmune diseases. We critically analyzed clinical, serological, and molecular associations, and reviewed experimental models of induction of and, alternatively, protection from autoimmune diseases by infection. After reviewing several studies and reports, a clinical and experimental pattern emerges: Chronic and multiple infections with viruses, such as Epstein–Barr virus and cytomegalovirus, and bacteria, such as H. pylori, may, in susceptible individuals, play a role in the evolvement of autoimmune diseases. As the vast majority of infections pertain to our resident microbiota and endogenous retroviruses and healthy carriage of infections is the rule, we propose to focus on understanding the mechanisms of this healthy carrier state and what changes its configurations to infectious syndromes, to the restoration of health, or to the sustaining of illness into a chronic state and/or autoimmune disease. It seems that in the development of this healthy carriage state, the infection or colonization in early stages of ontogenesis with key microorganisms, also called ‘old friends’ (lactobacilli, bifidobacteria among others), are important for the healthy living and for the protection from infectious and autoimmune syndromes.

Too early to dismiss Yersinia enterocolitica infection in the aetiology of Graves' disease: evidence from a twin case-control study

BACKGROUND

Yersinia enterocolitica (YE) infection has long been implicated in the pathogenesis of Graves' disease (GD). The association between YE and GD could, however, also be due to common genetic or environmental factors affecting the development of both YE infection and GD. This potential confounding can be minimized by investigation of twin pairs discordant for GD.

AIM

To examine whether YE infection is associated with GD.

DESIGN

We first conducted a classical case-control study of individuals with (61) and without (122) GD, and then a case-control study of twin pairs (36) discordant for GD.

METHODS

Immunoglobulin (Ig)A and IgG antibodies to virulence-associated Yersinia outer membrane proteins (YOPs) were measured.

MAIN OUTCOME MEASURES

The prevalence of YOP IgA and IgG antibodies.

RESULTS

Subjects with GD had a higher prevalence of YOP IgA (49%vs. 34%, P = 0.054) and YPO IgG (51%vs. 35%, P = 0.043) than the external controls. The frequency of chronic YE infection, reflected by the presence of both IgA and IgG YOP antibodies, was also higher among cases than controls (49%vs. 33%, P = 0.042). Similar results were found in twin pairs discordant for GD. In the case-control analysis, individuals with GD had an increased odds ratio (OR) of YE infection: IgA 1.84 (95% CI 0.99-3.45) and IgG 1.90 (95% CI 1.02-3.55). In the co-twin analysis, the twin with GD also had an increased OR of YE infection: IgA 5.5 (95% CI 1.21-24.81) and IgG 5.0 (95% CI 1.10-22.81).

CONCLUSION

The finding of an association between GD and YE in the case-control study and within twin pairs discordant for GD supports the notion that YE infection plays an aetiological role in the occurrence of GD, or vice versa. Future studies should examine the temporal relationship of this association in more depth.

Changed presentation of Hashimoto's thyroiditis in North-Eastern Sicily and Calabria (Southern Italy) based on a 31-year experience

OBJECTIVE

To quantify the yearly prevalence of Hashimoto's thyroiditis at our Division and evaluate changes in its clinical presentation over the period 1975-2005.

DESIGN

We have reviewed retrospectively the clinical records of patients admitted to a university hospital located in Messina, Sicily (Italy), from January 1, 1975, through December 31, 2005. This facility attracts patients from North-Eastern Sicily and most of Calabria, the Italian region across the Straits. HT was diagnosed based on various combinations of clinical, laboratory, and instrumental findings. The study group consisted of 4064 HT patients diagnosed during these 31 years.

MAIN OUTCOME

We evaluated these indexes on a yearly basis: number of new HT diagnoses; age at presentation; male-to-female ratio; functional status; goitrous or nongoitrous variants with or without nodule(s); above-normal titers or levels of serum thyroid autoantibodies (thyroglobulin antibodies and thyroperoxidase antibodies). Several indexes have changed over those 31 years. Particularly, HT has become 10 times more common than it was until the early 1990s and males are relatively more represented. Patients are relatively younger, with a nongoitrous thyroid; the rate of S-Hypo exceeds largely the rate of O-Hypo. Serum thyroid autoantibodies have become less frequently positive, and when positive, they are present at a lower concentration.

CONCLUSIONS

Only environmental changes, as opposed to genetic changes, can account for such alterations in the presentation of HT in our geographical area.

Yersinia enterocolitica infection does not confer an increased risk of thyroid antibodies: evidence from a Danish twin study

Understanding of the aetiological basis of thyroid autoimmunity may be gained by studying the early stages of the disease process. We aimed to (1) investigate the relationship between thyroid antibody status and Yersinia enterocolitica (YE) infection in euthyroid subjects and (2) explore the relative importance of genetic and environmental risk factors in the acquisition of YE infection. The association between thyroid antibody status and YE infection was explored using a case-control design. Furthermore, thyroid antibody-positive twins were compared with their thyroid antibody-negative co-twin. In 468 twins, IgA and IgG antibodies to virulence-associated outer-membrane proteins (YOPs) of YE were measured. Of these, 147 were thyroid antibody-positive (cases). A total of 147 age- and gender-matched twins were chosen as controls. The prevalence of YOP antibodies was lower among thyroid antibody-positive individuals than among controls. Yersinia infection was not associated with a positive thyroid antibody status: the odds ratio (with 95% CI) for YOP IgA-ab was 0.66 (0.42-1.05), P = 0.078 and for YOP IgG-ab it was 0.95 (0.60-1.50), P = 0.816. Within discordant twin pairs, the thyroid antibody-positive twin did not have an increased risk of Yersinia infection compared to the thyroid antibody-negative co-twin [odds ratio: YOP IgA-Ab: 0.94 (0.49-1.83), P = 0.866, and YOP IgG-Ab: 1.35 (0.72-2.53), P = 0.345]; 41% (95% CI 10-67% of the liability of being YOP antibody-positive was due to genetic effects. In conclusion, Yersinia infection does not confer an increased risk of thyroid antibodies. The genetic contribution in the acquisition of Yersinia infection is modest.

Human thyroid autoantigens and proteins of Yersinia and Borrelia share amino acid sequence homology that includes binding motifs to HLA-DR molecules and T-cell receptor

We previously reported that the spirochete Borrelia burgdorferi could trigger autoimmune thyroid diseases (AITD). Subsequently, we showed local amino acid sequence homology between all human thyroid autoantigens (human thyrotropin receptor [hTSH-R], human thyroglobulin [hTg], human thyroperoxidase [hTPO], human sodium iodide symporter [hNIS]) and Borrelia proteins (n = 6,606), and between hTSH-R and Yersinia enterocolitica (n = 1,153). We have now updated our search of homology with Borrelia (n = 11,198 proteins) and extended our search on Yersinia to the entire species (n = 40,964 proteins). We also searched the homologous human and microbial sequences for peptide-binding motifs of HLA-DR molecules, because a number of these class II major histocompatibility complex (MHC) molecules (DR3, DR4, DR5, DR8, and DR9) are associated with AITD. Significant homologies were found for only 16 Borrelia proteins (5 with hTSH-R, 2 with hTg, 3 with hTPO, and 6 with hNIS) and only 19 Yersinia proteins (4 with hTSH-R, 2 with hTg, 2 with hTPO, and 11 with hNIS). Noteworthy, segments of thyroid autoantigens homologous to these microbial proteins are known to be autoantigenic. Also, the hTSH-R homologous region of one Borrelia protein (OspA) contains an immunodominant epitope that others have found to be homologous to hLFA-1. This is of interest, as the hLFA-1/ICAM-1 ligand/receptor pair is aberrantly expressed in the follicular cells of thyroids affected by Hashimoto's thyroiditis. A computer-assisted search detected antigenic peptide binding motifs to the DR molecules implicated in AITD. In conclusion, our in silico data do not directly demonstrate that Borrelia and Yersinia proteins trigger AITD but suggest that a restricted number of them might have the potential to, at least in persons with certain HLA-DR alleles.

Putative association between anti-Borrelia IgG and autoimmune thyroid disease?

An association between borreliosis and autoimmune thyroid disease (AITD) has previously been discussed. We undertook the present analyses to explore associations between anti-Borrelia immunoglobulin G (IgG) and AITD using data from the population-based Study of Health in Pomerania (SHIP), which was conducted in a region with endemic Borreliosis. Data of 4,256 persons were available for the present analyses. IgG antibodies to Borrelia were determined by enzyme-linked immunosorbent assay (ELISA). AITD was defined as the combined presence of a hypoechogenic thyroid pattern in thyroid ultrasound and positive anti-thyroperoxidase levels. An association between anti-Borrelia IgG and AITD was neither present in bivariate nor in multivariate statistical analyses. This result was not affected by using different definitions of the exposure and the end points. There is no association between the exposure to Borrelia as defined by anti-Borrelia IgG and the risk of AITD. It seems unlikely that Borrelia species represent a relevant causal factor for AITD.

Homologies between proteins of Borrelia burgdorferi and thyroid autoantigens

Subclinical exposure to microbic antigens that share amino acid sequence homology with self antigens might trigger autoimmune diseases in genetically predisposed individuals via molecular mimicry. Genetic predisposition to Graves' disease (GD) or Hashimoto's thyroiditis (HT) is conferred by HLA loci DR3 or DR5, respectively. Yersinia enterocolitica (YE) outer proteins (YOPs) are candidate triggers based on the high prevalence of serum antibodies (Ab) against YOPs in autoimmune thyroid diseases (AITD) and reactivity of these Ab with hTSH-R, suggesting homology between YOPs and hTSH-R. We have reported previously that the spirochete Borrelia burgdorferi (Bb) could be another trigger. We have explored further the homology of hTSH-R with YE and Bb. Using the Basic Local Alignment Search Tool (BLAST), we found four matches with YE and five matches with Bb . Residues 22-272, 186-330, 319-363 and 684-749 of hTSH-R matched YopM, Ysp, exopolygalacturonase and SpyA of YE (identity 23-31%, similarity 40-48%). Residues 112-205, 127-150, 141-260, 299-383 and 620-697 of hTSH-R matched outer surface protein A, flagellar motor rotation protein A, two hypothetical proteins (BBG02 and BBJ08) and DNA recombinase/ATP dependent helicase of Borrelia (identity 27-50%, similarity 40-75%). Interestingly, the above hTSH-R regions coincide with (or include) known human T-cell epitopes: aa 52-71, 140-176, 240-270, 340-380 and 441-661. Our data strengthen the hypothesis of Bb and YE as environmental triggers of AITD in genetically predisposed persons through molecular mimicry mechanisms.

Increased prevalence of antibodies to enteropathogenic Yersinia enterocolitica virulence proteins in relatives of patients with autoimmune thyroid disease

Infections have been implicated in the pathogenesis of a number of autoimmune diseases, and Yersinia enterocolitica (YE) might play a role in the development of autoimmune thyroid disease (AITD). Clinical evidence in support of this hypothesis has been inconclusive. We reasoned that looking earlier in the natural course of AITD might enhance chances of finding evidence for YE infection. Consequently, we determined seroreactivity against YE in subjects at risk of developing AITD, i.e. in 803 female relatives of AITD patients in self-proclaimed good health. As a comparison group we used 100 healthy women who participated in a program for reference values. IgG and IgA antibodies to virulence-associated outer membrane proteins (YOPs) of YE were measured by a specific assay. Serum thyroid peroxidase antibodies (TPO-Ab) as indicators of AITD were considered to be positive at levels of> 100 kU/l. The prevalence of YOP IgG-Ab was higher in AITD relatives than in controls (40.1% vs. 24%, P = 0.002), and the same was true for YOP IgA-Ab (22% vs. 13%, P < 0.05). Of the 803 AITD relatives, 44 had an increased or decreased plasma TSH, and 759 were euthyroid as evident from a normal TSH; the prevalence of YOP-Ab did not differ between these three subgroups. TPO-Ab were present in 10% of controls and in 27% of the AITD relatives (P < 0.001). The prevalence of TPO-Ab in the euthyroid AITD relatives was not different between YOP IgG-Ab positive and negative subjects (23.3% vs. 24.7%, NS), nor between YOP IgA-Ab positive and negative subjects (21.2% vs. 24.9%, NS). In conclusion, healthy female relatives of AITD patients have an increased prevalence of YOP antibodies, which, however, is not related to the higher prevalence of TPO antibodies in these subjects. The findings suggest a higher rate of persistent YE infection in AITD relatives. Susceptibility genes for AITD may also confer a risk for YE infection.