Human spumaretrovirus-related sequences in the DNA of leukocytes from patients with Graves disease

Graves' disease: Epidemiology, genetic and environmental risk factors and viruses

Graves' disease (GD) is the most common cause of hyperthyroidism in developed Countries. It is more common between 30 and 60 years; 5-10 times more frequent in women. The genetic predisposition accounts for 79% of the risk for GD, while environmental factors for 21%. About 70% of genes associated with autoimmune thyroid disorders (AITD) are implicated in T-cell function. Among GD endogenous factors, estrogens, X-inactivation and microchimerism are important. Among environmental risk factors, smoking, iodine excess, selenium and vitamin D deficiency, and the occupational exposure to Agent Orange have been associated with GD. Many studies showed that HCV is associated with thyroid autoimmunity and hypothyroidism, in patients with chronic HCV hepatitis (CHC); a significant link has been shown also between HCV-related mixed cryoglobulinemia and risk for GD. Moreover, IFN-α-treated CHC patients develop GD more frequently. Novel studies are needed about possible risk factors to reduce the occurence of GD in West Countries.

Current concepts in the molecular pathogenesis of thyroid-associated ophthalmopathy

Graves' disease (GD) is a common autoimmune condition. At its core, stimulatory autoantibodies are directed at the thyroid-stimulating hormone receptor (TSHR), resulting in dysregulated thyroid gland activity and growth. Closely associated with GD is the ocular condition known as thyroid-associated ophthalmopathy (TAO). The pathogenesis of TAO remains enigmatic as do the connections between the thyroid and orbit. This review highlights the putative molecular mechanisms involved in TAO and suggests how these insights provide future directions for identifying therapeutic targets. Genetic, epigenetic, and environmental factors have been suggested as contributory to the development of GD and TAO. Thyroid-stimulating hormone receptor and insulin-like growth factor receptor (IGF-1R) are expressed at higher levels in the orbital connective tissue from individuals with TAO than in healthy tissues. Together, they form a functional complex and appear to promote signaling relevant to GD and TAO. Orbital fibroblasts display an array of cell surface receptors and generate a host of inflammatory molecules that may participate in T and B cell infiltration. Recently, a population of orbital fibroblasts has been putatively traced to bone marrow-derived progenitor cells, known as fibrocytes, as they express CD45, CD34, CXCR4, collagen I, functional TSHR, and thyroglobulin (Tg). Fibrocytes become more numerous in GD and we believe traffic to the orbit in TAO. Numerous attempts at developing complete animal models of GD have been largely unsuccessful, because they lack fidelity with the ocular manifestations seen in TAO. Better understanding of the pathogenesis of TAO and development of improved animal models should greatly accelerate the identification of medical therapy for this vexing medical problem.

Viruses and thyroiditis: an update

Viral infections are frequently cited as a major environmental factor involved in subacute thyroiditis and autoimmune thyroid diseases This review examines the data related to the role of viruses in the development of thyroiditis.

Our research has been focused on human data. We have reviewed virological data for each type of thyroiditis at different levels of evidence; epidemiological data, serological data or research on circulating viruses, direct evidence of thyroid tissue infection. Interpretation of epidemiological and serological data must be cautious as they don't prove that this pathogen is responsible for the disease. However, direct evidence of the presence of viruses or their components in the organ are available for retroviruses (HFV) and mumps in subacute thyroiditis, for retroviruses (HTLV-1, HFV, HIV and SV40) in Graves's disease and for HTLV-1, enterovirus, rubella, mumps virus, HSV, EBV and parvovirus in Hashimoto's thyroiditis. However, it remains to determine whether they are responsible for thyroid diseases or whether they are just innocent bystanders. Further studies are needed to clarify the relationship between viruses and thyroid diseases, in order to develop new strategies for prevention and/or treatment.

Establishment of an indicator cell line to quantify bovine foamy virus infection

A cell line derived from baby hamster kidney (BHK-21) cells was transfected with the enhanced green fluorescent protein gene driven by the bovine foamy virus (BFV) long terminal repeat (LTR) to establish a BFV indicator cell line (BICL). Among 48 clones, one clone was chosen for its little constitutive enhanced green fluorescent protein (EGFP) expression and high level of EGFP expression after activation by BFV infection. By detecting the EGFP expression of the BFV indicator cell line, the titers of BFV were quantified by the end point method. As a result, the titer determined by the EGFP based assay 5-6 days post infection (d.p.i.) was 100 fold higher than traditional assays measuring cytopathic effects 8-9 d.p.i.. Moreover, the EGFP based assay was also used to determine the titer of those cells infected by BFV without inducing cytopathic effects. Using this simple and rapid assay, we examined the in vitro host range of BFV. It was found that BFV can productively infect various cell lines derived from bovine, human, rat and monkey.

Human RNA "rumor" viruses: the search for novel human retroviruses in chronic disease

Retroviruses are an important group of pathogens that cause a variety of diseases in humans and animals. Four human retroviruses are currently known, including human immunodeficiency virus type 1, which causes AIDS, and human T-lymphotropic virus type 1, which causes cancer and inflammatory disease. For many years, there have been sporadic reports of additional human retroviral infections, particularly in cancer and other chronic diseases. Unfortunately, many of these putative viruses remain unproven and controversial, and some retrovirologists have dismissed them as merely "human rumor viruses." Work in this field was last reviewed in depth in 1984, and since then, the molecular techniques available for identifying and characterizing retroviruses have improved enormously in sensitivity. The advent of PCR in particular has dramatically enhanced our ability to detect novel viral sequences in human tissues. However, DNA amplification techniques have also increased the potential for false-positive detection due to contamination. In addition, the presence of many families of human endogenous retroviruses (HERVs) within our DNA can obstruct attempts to identify and validate novel human retroviruses. Here, we aim to bring together the data on "novel" retroviral infections in humans by critically examining the evidence for those putative viruses that have been linked with disease and the likelihood that they represent genuine human infections. We provide a background to the field and a discussion of potential confounding factors along with some technical guidelines. In addition, some of the difficulties associated with obtaining formal proof of causation for common or ubiquitous agents such as HERVs are discussed.

Myasthenia gravis accompanied by thymomas not related to foamy virus genome in Belarusian's patients

The spectrum and features of neurological disorders have been changed due to the Chernobyl catastrophe in the Republic of Belarus. More recently neurologists in Belarus have noted a significant increase in the frequency of myasthenia gravis (MG) with concomitant rise in the thymomas. There is some evidence suggesting that retroviruses play a key role in the development and pathogenesis of autoimmune diseases. This study analyzed thymomas from 45 MG patients from the Republic of Belarus by using PCR and primers for two regions of FV--gag and bel-2 genes. The results showed that none of the varied thymuses from the 45 MG patients contained FV genome. No relationship can be confirmed between FV and this disease and the results suggest that no pathological link between FV and MG exists.

Human foamy virus bel1 sequence in patients with autoimmune rheumatic diseases

Since the association between human foamy virus (HFV) with rheumatic autoimmune diseases remains controversial, this study was designed to determine the relationship between HFV and systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), or progressive systemic sclerosis (PSS). The bel1 and Pol sequences of HFV were measured by reverse transcriptase-polymerase chain reaction (RT-PCR) in plasma and by PCR in peripheral blood mononuclear cells (PBMC) from patients with SLE, RA, and PSS. Antibodies against Bel1 and Pol were assessed by enzyme-linked immunosorbent assay. Active HFV infections were detected by a Bel1-responsive indicator cell line. The bel1 sequence was detected in the plasma (SLE 59, RA 32, and PSS 63%) and PBMC (SLE 54, RA 71, and PSS 57%). However, active HFV infection existed only in patients with the bel1 sequence in both plasma and PBMC. In SLE patients, antibodies against Bel1 (7.1%) and Pol (4.5%) were also detected. The results suggest a possible association between HFV infection and these autoimmune rheumatic diseases.

Seroreactivity to A-type retrovirus proteins in a subset of cats with hyperthyroidism

The thyroid gland is afflicted in several endocrine, autoimmune, and malignant diseases. Previous studies detected immunoreactivity against proteins of a human intracisternal A-type retroviral particle type-I (HIAP-I) in serum samples from the majority of patients with Graves' disease, an autoimmune disease of the thyroid that can also affect other organs, most prominently the eyes. To determine whether hyperthyroid animals might provide a model for the retroviral involvement in thyroid autoimmunity, serum samples from 32 cats (21 hyperthyroid and 11 controls) and 10 hypothyroid dogs were examined for immunoreactivity with HIAP-I using a Western blot technique. Of the 21 hyperthyroid cats 15 (71.4%) were HIAP-I positive, while only 2 of 11 (11.8%) control animals without endocrine pathology were positive. No significant correlations were seen between HIAP seroreactivity and serum thyroid hormone levels (T3 and T4), age, gender, treatment history, vaccination status, or weight. No seroreactivity to HIAP-I was detected in hypothyroid dogs. An examination of HIAP-I reactivity in feline leukemia virus (FeLV)-seroconverting cats found that 7/9 (78%) animals viremic for FeLV-A showed an alteration in HIAP serology, whereas only 1/7 (14%) nonviremic animals showed a change in HIAP-I serology. These results suggest that it may be possible to develop an animal (feline) model for the role of retroviruses in thyroid autoimmune diseases.

Human T cell leukemia virus type I-infected patients with Hashimoto's thyroiditis and Graves' disease

CONTEXT

Autoimmune thyroid diseases have been reported to be associated with human T cell leukemia virus type I (HTLV-I) infection. HTLV-I proviral load is related to the development of HTLV-I-associated myelopathy/tropical spastic paraparesis and has also been shown to be elevated in the peripheral blood of HTLV-I-infected patients with uveitis, arthritis, and connective tissue disease.

OBJECTIVE

The objective of the study was to evaluate the proviral load in HTLV-I-infected patients with Hashimoto's thyroiditis (HT) or Graves' disease (GD) and ascertain the ability of HTLV-I to infect thyroid cells.

PATIENTS AND METHODS

A quantitative real-time PCR assay was developed to measure the proviral load of HTLV-I in peripheral blood mononuclear cells from 26 HTLV-I-infected patients with HT, eight HTLV-I-infected patients with GD, or 38 asymptomatic HTLV-I carriers. Rat FRTL-5 thyroid cells were cocultured with HTLV-I-infected T cell line MT-2 or uninfected T cell line CCRF-CEM. After coculture with T cell lines, changes in Tax and cytokine mRNA expression were studied by RT-PCR.

RESULTS

HTLV-I proviral load was significantly higher in the peripheral blood of patients with HT and GD than asymptomatic HTLV-I carriers. In the peripheral blood from HTLV-I-infected patients with HT, HTLV-I proviral load did not correlate with the thyroid peroxidase antibody or thyroglobulin antibody titer. After coculture with MT-2 cells, FRTL-5 cells expressed HTLV-I-specific Tax mRNA. These cocultured FRTL-5 cells with MT-2 cells expressed IL-6 mRNA and proliferated more actively than those cocultured with CCRF-CEM cells.

CONCLUSION

Our findings suggest the role of the retrovirus in the development of autoimmune thyroid diseases in HTLV-I-infected patients.

Involvement of human intracisternal A-type retroviral particles in autoimmunity

Prior studies have linked retroviruses to various arthropathies and autoimmune diseases. Sjögren's syndrome (SS), a systemic autoimmune disease, is characterized by aggressive infiltration of lymphocytes into the salivary and lacrimal glands, resulting in destruction of the glands and dry mouth and eyes (sicca syndrome). The infiltrating lymphocytes in SS may become overtly malignant, and thus, the incidence of lymphoma is greatly increased in SS patients. A human intracisternal A-type retroviral particle type I (HIAP-I) has been isolated from persons with SS. HIAP-I shares a limited number of antigenic epitopes with human immunodeficiency virus (HIV), but is distinguishable from HIV by morphological, physical, and biochemical criteria. A substantial majority of patients with SS or systemic lupus erythematosus (SLE) have serum antibodies to the proteins of this human retrovirus. Fewer than 3% of the normal blood donor population have antibodies to any HIAP-associated proteins. A second type of a human intracisternal A-type retrovirus, HIAP-II, was detected in a subset of patients with idiopathic CD4 lymphocytopenia (ICL), an AIDS-like immunodeficiency disease. Most HIAP-II positive ICL patients were also antinuclear antibody positive. Reviewed here are additional studies from several laboratories suggesting that HIAP or related viruses may be involved in SLE and other autoimmune conditions. Additionally, results of comprehensive surveys of autoimmune patients to determine seroreactivity to HIAP, and other human retroviruses, including HIV and human T-lymphotropic virus type I, are reported.

Self-recognition and the role of fetal microchimerism

The course and severity of the autoimmune thyroid diseases (AITD) is known to be influenced by pregnancy as evidenced by disease suppression during pregnancy and initiation, or exacerbation, of disease postpartum. AITD is also known to affect both fertility and pregnancy outcome as evidenced by increased fetal loss. However, the precise mechanisms of this influence have not been fully understood. Here we have reviewed the mechanisms of self-recognition thought to be active in AITD and we have included recent information on the potential role of fetal microchimerism (exposure of paternal antigen to the mother during and after pregnancy).

FIP: a novel approach to vaccination. Proceedings from the 2nd International FCoV/FIP Symposium, Glasgow, 4-7 August 2002

Feline infectious peritonitis (FIP) is a fatal disease of cats. Early attempts at vaccination have been unsuccessful, some even serving to exacerbate the disease through antibody-dependent enhancement. Replication-incompetent feline foamy virus (FFV) transducing vectors are being developed as potential vaccine agents, into which immunogenic fragments of feline coronavirus (FCoV) proteins will be inserted. To use a recombinant viral vector to express FCoV proteins, the agent chosen should be apathogenic and replication incompetent within the host following gene delivery. Spumaviruses confer several advantages over the more traditionally explored retroviral vectors. Stable helper cell line clones have been established by transfection of CRFK cells with FFV tas and assessed using beta-galactosidase assays, PCR, immunofluorescence and western blotting. The generation of infectious virions using these cell lines has been investigated using tas-deleted FFV vectors containing the enhanced green fluorescent protein (eGFP) cassette.

Transient foamy virus vector production by adenovirus vectors

The genome of the prototype foamy virus (PFV) has been introduced into an adenoviral/PFV hybrid vector and tested for stable in vitro gene transfer. Three different adenoviruses are used to encode: (i) the PFV structural genes gag and pol (Ad-GagPolDeltaPacI); (ii) the PFV structural gene env (Ad-Env); and (iii) the PFV vector genome (Ad-MD9) encoding the transgene (the enhanced green fluorescent protein (eGFP) gene). Following cotransduction by the three adenoviruses, the target cells become transient PFV vector-producing cells, resulting in the in situ release of recombinant PFV at a titre of up to 10(3) vector particles/ml, which can then infect surrounding cells, leading to stable integration of the expression cassette. Stable eGFP expression, observed for up to 60 days (11 passages) in cells transduced with all three adenoviral vectors, was shown by PCR to be the result of PFV integration. In contrast, cells transduced with only the adenovirus encoding the PFV vector genome showed a marked decrease in eGFP expression by passage 2 (16 days post-transduction) and did not contain integrated PFV vector. In short, this paper describes the production of a hybrid vector capable of high in vitro transduction and stable transgene expression using adenovirus and PFV vectors.

Potential of zoonotic transmission of non-primate foamy viruses to humans

The zoonotic introduction of an animal pathogen into the human population and the subsequent extension or alteration of its host range leading to the successful maintenance of the corresponding pathogen by human‐to‐human transmission pose a serious risk for world‐wide health care. Such a scenario occurred for instance by the introduction of simian immunodeficiency viruses into the human population resulting in the human immunodeficiency viruses (HIV) and the subsequent AIDS pandemic or the proposed recent host range switch of the SARS coronavirus from a presently unknown animal species to humans. The occurrence of zoonotic transmissions of animal viruses to humans is a permanent threat to human health and is even increased by changes in the human lifestyle. In this review, the potential of the zoonotic transmission of bovine, feline and equine foamy retroviruses will be discussed in the light of well‐documented cases of zoonotic transmissions of different simian foamy viruses to humans.

Human infection with foamy viruses

Virtually all nonhuman primate species investigated thus far including prosimians, New World and Old World monkeys and apes all harbor distinct and species-specific clades of simian foamy virus (SFV). However, evidence supporting the existence of a human-specific foamy virus (FV) is not yet available. Early reports describing widespread infection of healthy and sick humans with FV could not be confirmed. In contrast, all FV infections documented in humans are of zoonotic origin and are identified in persons occupationally exposed to nonhuman primates. The introduction of SFV into humans raises several public health questions regarding disease outcomes and potential for human-to-human transmissibility. The available data from a very limited number of SFV-infected humans suggest that these infections are nonpathogenic and are not easily transmissible. Additional studies are needed to better define the prevalence and natural history of SFV in humans.

Simian foamy virus infection in a blood donor

BACKGROUND

Infections with simian foamy virus (SFV) are widely prevalent in nonhuman primates. SFV infection was confirmed in a worker, occupationally exposed to nonhuman primates, who donated blood after the retrospectively documented date of infection. Human-to-human transmission of SFV through transfusion and its pathogenicity have not been studied.

STUDY DESIGN AND METHODS

Recipients of blood from this donor were identified and blood samples from such recipients were tested for SFV infection by Western blot and PCR assay.

RESULTS

One recipient of RBCs and another recipient of FFP had died; retroviral infections were not implicated. One platelet recipient could not be tested. Recipients of RBCs (two), a WBC-reduced RBC unit (one), and a platelet unit (one) tested SFV-negative 19 months to 7 years after transfusion. Tested recipients had transfusions 3 to 35 days after blood donation. Samples of one lot of albumin and three lots of plasma protein fraction (manufactured from recovered plasma from two donations) tested negative both for antibodies and for viral RNA.

CONCLUSION

SFV transmission through transfusion was not identified among four recipients of cellular blood components from one SFV-infected donor. Derivatives containing plasma from that donor tested negative for SFV.

Lack of detection of retroviral particles (HIAP-1) in the H9 T cell line co-cultured with thyrocytes of Graves' disease

Evidence for a possible aetiopathogenetic role of endogenous and/or exogenous retroviruses (RVs) in organ- and non-organ-specific autoimmune diseases is circumstantial in both humans and animal models. Intracisternal A type particles, antigenically related to HIV, have been reported in H9 cells co-cultured with homogenates of salivary glands obtained from patients with Sjögren syndrome and with synovial fluid of patients with rheumatoid arthritis. In order to identify a possible transfer of a putative 'infective RV agent' involved in the pathogenesis of human thyroid autoimmune disease, the H9 T cell line was co-cultured not only with thyroid homogenates, but also with viable thyrocytes, both prepared from glands of patients with Graves' disease. At the end of a prolonged co-culture period (24 weeks), no RV particles could be detected by electron microscopy in the H9 cells co-cultured with both thyroid preparations. These data seem to exclude the involvement of HIAP-1 in the aetiopathogenesis of human autoimmune thyroid disease.

A quantitative assay for measuring human foamy virus using an established indicator cell line

In order to improve the accuracy for detecting human foamy virus (HFV), an indicator cell line was established by co-transfecting baby hamster kidney-21 cells with two plasmids: one containing a G418 antibiotic resistance marker and the other including the luc gene which was placed downstream of the inducible HFV long terminal repeat promoter (from -533 to +20). Among 11 independent subclones, IdB14 was found to be stable with a low basal level of luciferase activity. Although the changes in luciferase activity in infected clones showed time-dependency and peaked at day 8, it is possible to differentiate infected and uninfected cells on day 2. The sensitivity of the foamy virus activated luciferase (FAL) assay was 400 times higher than the end-point syncytium formation by TCID(50). The HFV LTR promoter in the IdB14 cell line was specific for this virus. Moreover, a linear relationship was found between the MOI and the activated intensity of luciferase expression. These findings suggest that the FAL assay using the IdB14 indicator cell line is a simple and useful technique for rapid diagnosis and quantitation of active HFV infection.

Historical perspective of foamy virus epidemiology and infection

Foamy viruses (FV) are complex retroviruses which are widespread in many species. Despite being discovered over 40 years ago, FV are among the least well characterized retroviruses. The replication of these viruses is different in many interesting respects from that of all other retroviruses. Infection of natural hosts by FV leads to a lifelong persistent infection, without any evidence of pathology. A large number of studies have looked at the prevalence of primate foamy viruses in the human population. Many of these studies have suggested that FV infections are prevalent in some human populations and are associated with specific diseases. More recent data, using more rigorous criteria for the presence of viruses, have not confirmed these studies. Thus, while FV are ubiquitous in all nonhuman primates, they are only acquired as rare zoonotic infections in humans. In this communication, we briefly discuss the current status of FV research and review the history of FV epidemiology, as well as the lack of pathogenicity in natural, experimental, and zoonotic infections.

Human retroviral sequences associated with extracellular particles in autoimmune diseases: epiphenomenon or possible role in aetiopathogenesis?

Publications describing retroviral sequences associated with extracellular particles in Sjögren's syndrome or systemic lupus erythematosus, multiple sclerosis, and type I diabetes present novel arguments and raise complex questions about eventual relationships between retroviruses and autoimmunity. They are presented and discussed in the present review, preceded by an overview of the biology of retroviral elements.

Prevalence of human foamy virus-related sequences in the Korean population

The possible association of human foamy virus (HFV) with human thyroid disorders such as Graves' disease (GD) has been a topic of controversy due to the inconsistent results reported by several groups of investigators. Here we report the investigation of the presence of HFV-related sequences in the Korean population. DNA was obtained from peripheral blood lymphocytes from 24 GD patients and 23 healthy blood donors and subjected to PCR amplification using three sets of nested primers derived from gag, env, and LTR regions of the HFV genome. Contrary to previously reported studies, our analysis identified HFV-related sequences in the genomes of both healthy individuals and the GD patients. However, the nature of the HFV genome present in each group appeared to be different. We detected all 3 regions of HFV-related sequences in 29% of the HFV-positive GD patients, while no samples in the control group amplified all three regions. This suggests that the LTR may be used as a tool for screening for HFV in GD patients. Our data favor the hypothesis of a relationship between GD and the presence of HFV-related sequences, though in a complex way.

TSH receptor antibody-associated thyroid dysfunction following subacute thyroiditis

OBJECTIVE

Autoimmunity plays an important role in the development of thyrotrophin (TSH) receptor antibodies and the pathogenesis of Graves' disease and Hashimoto's thyroiditis. On the other hand, subacute thyroiditis is a self-limited inflammatory disease of presumed viral aetiology. The aim of this study was to examine whether subacute thyroiditis triggers TSH receptor antibody-associated thyroid disorders.

PATIENTS

We reviewed 1,697 patients with subacute thyroiditis seen between 1985 and 1995.

DESIGN AND MEASUREMENTS

We measured antibodies which inhibit the TSH binding to the TSH receptor (TBIAb), thyroid stimulating antibodies (TSAb) and antibodies that block TSH action (TBAb). Other thyroid autoantibodies were also determined.

RESULTS

TBIAb became positive in 38 patients following subacute thyroiditis. Thyroid function after the development of TBIAb appeared to be influenced by the bioactivity of the antibody. Hyperthyroidism developed in the presence of TSAb, and so did hypothyroidism in the presence of TBAb, although 21 patients did not have thyroid dysfunction despite high titres of TBIAb. Fifteen out of 17 patients recovered from hyperthyroidism or hypothyroidism after the disappearance of TBIAb sometimes even without medication. TBIAb-positive patients had a high incidence of a family history of thyroid disease and positive anti-thyroid microsomal antibodies. An ophthalmopathy similar to Graves' disease was also observed in 3 patients.

CONCLUSIONS

Subacute thyroiditis may trigger autoreactive B cells to produce TSH receptor antibodies, resulting in TSH receptor antibody-associated thyroid dysfunction in some patients.

Degeneration of the cerebellar granule cell layer in transgenic mice expressing genes of human foamy virus

Transgenic mice expressing various combinations of structural and regulatory genes of human foamy virus (HFV) develop a neurodegenerative syndrome. delta gpe transgenic mice (which express the auxiliary bel-1 and bet genes along with truncated forms of gag, pol, and env) develop a severe neurological syndrome consisting mainly of spastic tetraparesis and blindness, and show neuronal loss in the hippocampus and cerebral cortex. In addition, mice in two of eight delta gpe lines developed an ataxic gait. Here we studied the phenotype of these two lines, and show that these mice exhibit progressive degeneration of their cerebellar granule cells beginning at 4-8 weeks of age. Transgenic mRNA and HFV proteins accumulate in cerebellar granule cells immediately before the onset of degeneration. The Purkinje cell layer is largely unaffected by this pathological process. Probably due to the loss of granule cell processes, the cerebellar molecular layer is narrowed in the late stages of the disease. These findings indicate that HFV gene products can be neurotoxic for cerebellar granule cells.

Regulation of major histocompatibility complex class I gene expression in thyroid cells. Role of the cAMP response element-like sequence

The major histocompatibility complex (MHC) class I gene cAMP response element (CRE)-like site, -107 to -100 base pairs, is a critical component of a previously unrecognized silencer, -127 to -90 bp, important for thyrotropin (TSH)/cAMP-mediated repression in thyrocytes. TSH/cAMP induced-silencer activity is associated with the formation of novel complexes with the 38-base pair silencer, whose appearance requires the CRE and involves ubiquitous and thyroid-specific proteins as follows: the CRE-binding protein, a Y-box protein termed thyrotropin receptor (TSHR) suppressor element protein-1 (TSEP-1); thyroid transcription factor-1 (TTF-1); and Pax-8. TTF-1 is an enhancer of class I promoter activity; Pax-8 and TSEP-1 are suppressors. TSH/cAMP decreases TTF-1 complex formation with the silencer, thereby decreasing maximal class I expression; TSH/cAMP enhance TSEP-1 and Pax-8 complex formation in association with their repressive actions. Oligonucleotides that bind TSEP-1, not Pax-8, prevent formation of the TSH/cAMP-induced complexes associated with TSH-induced class I suppression, i.e. TSEP-1 appears to be the dominant repressor factor associated with TSH/cAMP-decreased class I activity and formation of the novel complexes. TSEP-1, TTF-1, and/or Pax-8 are involved in TSH/cAMP-induced negative regulation of the TSH receptor gene in thyrocytes, suppression of MHC class II, and up-regulation of thyroglobulin. TSH/cAMP coordinate regulation of common transcription factors may, therefore, be the basis for self-tolerance and the absence of autoimmunity in the face of TSHR-mediated increases in gene products that are important for thyroid growth and function but are able to act as autoantigens.

Long terminal repeat U3 length polymorphism of human foamy virus

Size determination of the long terminal repeat (LTR) of an early (1985) and a more recent (1993) passage of wild-type human foamy virus (HFV) revealed that the virus has undergone substantial deletions in the U3 region upon replication in tissue culture. Two LTR deletion variants (HSRV1 and 2) have been characterized in the past and used to construct molecular clones which are replication competent in cell culture. We now report the molecular cloning, sequencing, and biological characterization of an HFV genome with full-length LTR (pHFV2). Sequence analysis revealed that the deletions in HSRV1 and 2 are nonrandom and probably occurred by misalignment during reverse transcription. The comparative analysis of HFV2 and the variant with the largest U3 deletion, HSRV2, revealed a differential ability to replicate in human cell cultures. While HSRV2 replicated faster in diploid human fibroblasts, cells which have been used extensively for amplification of HFV in the past, replication of HFV2 was faster in a lymphoblastoid cell line. Reporter gene assays indicated that the cell-type specific ability of the LTRs to respond to the viral transcriptional transactivator may be a likely, reason for the different growth properties of both viruses and for the occurrence of the HFV U3 deletions. In foamy virus-infected chimpanzees only the full-length type of LTR was observed; however, the HSRV1 deletion variant was detected as the dominating virus in an accidentally HFV-infected human.

Protein composition and morphology of human foamy virus intracellular cores and extracellular particles

Characterization of human foamy virus (HFV) gag-encoded precursors and the search for a Gag-Pol polyprotein and mature proteins derived from proteolytic processing were carried out in HFV-infected cells and with purified preassembled cores and extracellular virus by Western blotting and radioimmunoprecipitation using antisera against synthetic peptides corresponding to putative Gag and protease proteins. Precursor proteins, Pr78gag/74gag and Pr135pol, were found in the nucleus of epithelial and fibroblast cells 3-4 days after HFV infection. Kinetic analysis of HFV Pr78gag and Pr74gag indicated that Pr78gag is a precursor to Pr74gag. South-Western blot analysis indicated that Pr78gag and Pr74gag have properties associated with nucleic acid binding protein although they lack the typical zinc-finger motifs found in retroviral nucleocapsid proteins. Western blot analyses of preassembled HFV cores isolated from the cytoplasm of infected cells and purified by sucrose gradient centrifugation demonstrated the presence of Pr78gag/74gag and Pr135pol, but no proteolytically processed Gag proteins were observed. The majority of extracellular HFV particles were found to have pentagon-shaped cores, as observed intracellularly, and are believed to be the immature extracellular form of the virus. The highest concentration of extracellular particles, estimated by EM, Western blot, and reverse transcriptase assays were found in sucrose gradient fractions having a density of 1.21-1.24 g/cm3. Western blot analysis revealed that Pr78gag/74gag and Pr135pol were the major viral proteins associated with these extracellular particles, as only small amounts of putative proteolytically cleaved capsid (p32) were observed. Our results support the notion that Pol is translated independent of Gag in HFV-infected cells.

Analysis of west African hunters for foamy virus infections

Foamy viruses are a genus of complex retroviruses that infect a wide variety of mammals. However, a clear association with any disease process has yet to be proven for these viruses. A higher human seroprevalence was reported in African populations, perhaps due to exposure to simian foamy viruses (SFV) endemic in primates. However, the earlier serologic surveys were not confirmed by studies employing nucleic acid amplification. Foamy virus infections of humans clearly do occur as rare zoonoses among primate center or laboratory workers exposed to captive primates or their blood. We sought to detect foamy virus infections in a cohort of humans also presumed to be exposed to SFV, i.e., West African hunters. We constructed recombinant vaccinia viruses that expressed human foamy virus (HFV) Gag or Env polyproteins in mammalian cells. The sera from 17 monkey hunters or several controls were tested in radioimmunoprecipitation assays (RIPAs) against the recombinant HFV proteins. Chimpanzee sera or HFV-positive human sera immunoprecipitated gp130, the HFV Env precursor, as well as p74, the HFV Gag polyprotein. None of the hunters' sera recognized both of these recombinant proteins. We then employed a nested polymerase chain reaction (PCR) analysis of the hunters' DNA but also failed to detect foamy virus infections. Therefore, by utilizing a recombinant RIPA and a nested PCR assay, we have not identified foamy virus infections occurring naturally in hunters exposed to wild monkeys in West Africa.

Inhibition of the in vitro infectivity and cytopathic effect of human foamy virus by dideoxynucleosides

Human foamy virus (HFV) is a human retrovirus that has not been clearly associated with human disease. In this study, we tested the capacity of nucleoside derivatives to inhibit the infectivity and cytopathic effect of HFV in T-lymphoblastoid cells in vitro. H9 cells showed a dramatic cytopathic effect 3 weeks after exposure to HFV. At this time, viral infection was demonstrated by detection of viral antigens by immunofluorescence staining, release of reverse transcriptase activity (RT) in the supernatant, detection of typical viral particles by electron microscopy, and presence of proviral DNA by Southern blot analysis. H9 cells were pretreated with dideoxycytidine (ddC), dideoxyinosine (ddI), or azidothymidine (AZT) at various concentrations before HFV infection. ddC could not completely suppress viral replication at low concentrations, and inhibited cell proliferation at higher concentrations. ddI partially inhibited the formation of giant cells at 10 microM, with 95% inhibition of RT in the supernatant. AZT induced a complete inhibition of cytopathic effect at concentrations > or = 1 microM, with more than 95% inhibition of RT in the supernatant. Moreover, the synthesis of proviral DNA was completely suppressed by 10 microM AZT. These results show that AZT and ddI can inhibit HFV replication in vitro.

The potential roles of endogenous retroviruses in autoimmunity

Endogenous retroviruses (ERVs) are estimated to comprise up to 1% of human DNA. While the genome of many ERVs is interrupted by termination codons, deletions or frame shift mutations, some ERVs are transcriptionally active and recent studies reveal protein expression or particle formation by human ERVs. ERVs have been implicated as aetiological agents of autoimmune disease, because of their structural and sequence similarities to exogenous retroviruses associated with immune dysregulation and their tissue-specific or differentiation-dependent expression. In fact, retrovirus-like particles distinct from those of known exogenous retroviruses and immune responses to ERV proteins have been observed in autoimmune disease. Quantitatively or structurally aberrant expression of normally cryptic ERVs, induced by environmental or endogenous factors, could initiate autoimmunity through direct or indirect mechanisms. ERVs may lead to immune dysregulation as insertional mutagens or cis-regulatory elements of cellular genes involved in immune function. ERVs may also encode elements like tax in human T-lymphotrophic virus type I (HTLV-I) or tat in human immunodeficiency virus-I (HIV-I) that are capable of transactivating cellular genes. More directly, human ERV gene products themselves may be immunologically active, by analogy with the superantigen activity in the long terminal repeat (LTR) of mouse mammary tumour viruses (MMTV) and the non-specific immunosuppressive activity in mammalian type C retrovirus env protein. Alternatively, increased expression of an ERV protein, or expression of a novel ERV protein not expressed in the thymus during acquisition of immune tolerance, may lead to its perception as a neoantigen. Paraneoplastic syndromes raise the possibility that novel ERV-encoded epitopes expressed by a tumour elicit immunity to cross-reactive epitopes in normal tissues. Recombination events between different but related ERVs, to whose products the host is immunologically tolerant, may also generate new antigenic determinants. Frequently reported humoral immunity to exogenous retrovirus proteins in autoimmune disease could be elicited by cross-reactive ERV proteins. A review of the evidence implicating ERVs in immune dysfunction leads to the conclusion that direct molecular studies are likely to establish a pathogenic role for ERVs in autoimmune disease.

Productive persistent infection of hematopoietic cells by human foamy virus

Human foamy virus can establish persistent infections in human hematopoietic cell lines, such as H92.1.7 (erythroblastoid cells), Jurkat (CD4+ T cells), and U937 (myeloid-monocytic cells). The infection is characterized by constant production of infectious viruses (for > 2 1/2 years) with no cytopathic effects on the host cells. Electron microscopy of the infected cells showed a viral morphology similar to that observed for particles produced after acute infection. We have detected, in addition to the full-length form of bel1, a previously described deletion in the bel1 gene of the proviral DNA in these cells. RNA containing this 301-bp deletion, which mapped to the splice donor and acceptor sites of the intron of the bet gene, was also found in encapsidated virion RNA. However, the presence of this defective provirus harboring the deletion in bel1 does not prevent productive persistence in these chronically infected cells, since the virus titer does not decrease during cultivation.

Cell tropism of the simian foamy virus type 1 (SFV-1)

Several cell lines representing different species and cell types were tested for simian foamy virus type 1 (SFV-1) infection. SFV-1 infections were monitored by polymerase chain reaction, reverse transcriptase, cytopathology, and immunofluorescent assays. All cells tested were permissive for SFV-1, demonstrating that SFV-1 has a broad host range with respect to species and cell types. Infected fibroblasts, epithelial cells, and neural cells all showed extensive cytopathology that is characteristic of foamy virus infection. No cytopathology was induced in T cell-derived Jurkats and Hut-78 cell lines. The cytopathic effects in B and macrophage originated cells were delayed by several days. Cytopathology in these cell lines was not as dramatic as seen in the infected fibroblast and epithelial cells. The reverse transcriptase values in the SFV-1 infected lymphoid and macrophage cell lines were severalfold lower than that of the fibroblasts and epithelial cells. Therefore, SFV-1 appears to establish a low level persistent infection in lymphoid and macrophage cell lines.

A serological survey of bovine syncytial virus in Ontario: associations with bovine leukemia and immunodeficiency-like viruses, production records, and management practices

Of the 920 cows tested, 56.7% showed antiretroviral serological reactivity. Prevalence rates (95% confidence interval) of antiretroviral antibodies among individual dairy cows in Ontario were: BIV 5.5% (4.0-7.0), BLV 25.7% (22.9-28.6), and BSV 39.6% (36.4-42.8). The following percentages of cows showed serological reactivity against the specified retroviruses: BIV 2.3%, BLV 14.0%, BSV 27.5%, BIV and BSV 1.3%, BIV and BLV 0.9%, BLV and BSV 9.9%, BIV and BLV and BSV 0.9%. These rates of sero-positivity are similar to those found in other countries. Serological test results were not adjusted for sensitivity and specificity. The prevalence rates of antibodies to the three retroviruses (BIV, BLV, and BSV) were significantly different, but no associations were observed between specific retroviral serological test results among individual cows. The prevalence rates of BIV and BSV seropositivity were constant across Ontario, whereas, there was a significant trend for the prevalence rate of BLV seropositivity to decrease going from southwestern to eastern Ontario; cows in eastern Ontario had approximately half the prevalence rate of those in southwestern Ontario. Cows that were seropositive for BSV were significantly older than BSV seronegative cows. There was no association between culling rate and BSV serology. Significant negative associations were found with winter or summer housing of calves separate from adults and summer outdoor exercise for dry cows. The use of calf hutches in the summer had a significant positive association with BSV seropositivity. Regression analyses were done to assess the association of retroviral (BIV, BLV, and BSV) seropositivity on calving interval, milk somatic cell count, and milk production. Serological test results for BIV, BLV, and BSV were entered into all models and all models were adjusted for intra-cluster (intraherd) correlation. Herd size and age were found to be important confounding variables. BIV seropositivity was not associated with any changes in production using this approach, however when considered in isolation BIV seropositivity remained associated with decreased milk production. BLV seropositivity was significantly associated with longer calving intervals and higher somatic cell counts in older cows. As well, in older cows, BSV seropositivity was significantly associated with higher milk production.

Absence of association between human spumaretrovirus and Graves' disease

Graves' disease (GD) is an autoimmune thyroid disease. The etiology of GD is still not clear. Both genetic and environmental factors, such as infectious agents, are believed to be involved in its pathogenesis. Recent findings suggest a role for human spumaretrovirus (HSRV) in the pathogenesis of GD. To test this hypothesis, we looked for the HSRV gag region sequence in DNA extracted from the peripheral blood leukocytes and thyroid tissue of patients with GD, and controls. Genomic DNA was subjected to a highly sensitive nested polymerase chain reaction, followed by dot-blot hybridization with an internal probe. HSRV gag region DNA fragments were detected in the peripheral blood leukocytes of patients with GD and controls to a similar extent; 5.3% (2/38) of Caucasian patients with GD, 4.7% (2/43) of Caucasian controls, 4.7% (2/43) of African-American patients with GD, and 6.5% of (3/46) African-American controls. Similar values were obtained for the samples of thyroid tissues; 5.5% (1/18) of Caucasian patients with GD and 5.0% (1/20) of controls. The differences in all these comparisons were not statistically significant. These results do not support a role for HSRV in the pathogenesis of GD.

Na+, K+ ATPase activity in red cells predicts the recurrence of hyperthyroidism in patients with Graves' disease

Graves' disease is an autoimmune disorder characterized by a course of remission and relapse. Several parameters have been evaluated for their abilities to predict the clinical course of Graves' disease in patients treated with antithyroid drugs. We recently demonstrated in patients with hyperthyroidism dependent by Graves' disease, an impaired Na+, K+ ATPase activity in red cells and a correlation between ATPase and free T3. With the aim to clarify the relationship between the course of hyperthyroidism and the Na+, K+ ATPase activity during and after discontinuing the antithyroid therapy, we followed up 24 patients for two years. In our previous work by restoring a normal level of free T3, we obtained a normalization of Na+, K+ ATPase activity in the red cells of all the patients. However, in eight subjects after a period of 150 days following the suspension of therapy, we observed a new reduction of ATPase activity in a clinical condition of euthyroidism. The same subjects, newly evaluated after 150 days, developed a clinical and biochemical relapse of hyperthyroidism. We believe that the determination of Na+, K+ ATPase activity is able to predict the recurrence of hyperthyroidism in patients with Graves' disease.

Presence of human T-lymphotropic virus type II-related genes in DNA of peripheral leukocytes from patients with autoimmune thyroid diseases

No etiologic role of human T-lymphotropic virus type II (HTLV-II) in any disease is yet known. The present study showed a high incidence of HTLV-II proviral DNA fragments in DNA of peripheral blood leukocytes from patients with autoimmune thyroid diseases. Using primers for the pol and tax regions of HTLV-II proviral DNA, amplified DNA fragments were demonstrated in 51.5% of the patients with Hashimoto's thyroiditis and in 11.8% of those with Graves' disease examined, but in only 1.9% of the disease controls and 1.0% of healthy individuals. These amplified DNA fragments hybridized with each of the inner probes. The nucleotide sequences of the DNA fragments of the pol and tax regions showed high homology with those of the prototype of HTLV-II. No antibodies for HTLV-II could, however, be detected in the patients examined. Because of the absence of its antibody, HTLV-II infection was not confirmed in these patients, but the presence of HTLV-II proviral DNA or its related DNA at high frequency suggests a relationship of HTLV-II with the development of autoimmune thyroid diseases.

Evidence for a retroviral trigger in Graves' disease

An apparently high frequency of Graves' disease encountered in New Orleans, Louisiana, prompted an investigation for a possible infectious agent that might be triggering the disease in genetically susceptible individuals. We studied 40 patients with Graves' disease, and compared them to the following groups of controls: age and gender matched healthy subjects; patients with multinodular goiter (non-autoimmune thyroid controls); patients with chronic lymphocytic thyroiditis (autoimmune thyroid disease controls) and additional organ or tissue specific autoimmune controls exclusive of thyroid autoimmunity, including patients with Type I diabetes and other endocrine autoimmune complex disorders. Serum antibodies against a prototypic strain of a human intracisternal A-type retroviral particle type 1 (HIAP-1) were detected by a sensitive and specific immunoblotting assay. In 87.5% (35/40) of the Graves' disease patients there was a positive reaction against several HIAP-1-associated proteins, predominantly 97 Kd and 80 Kd, with only 5 showing no reactivity to any. In contrast, 2% (2/105) of sera from normal controls showed positive reactivity. Furthermore, only 10% (1/10) of sera from multinodular goiter control patients and 10% (1/10) of Hashimoto's patients showed reactivity (p < 0.0005). Sera from 3 of 20 (15%) of Type I diabetic patients none of whom had Graves' disease, showed reactivity but there was no reactivity in 9 other patients with one or more of the endocrine autoimmune complex disorders, including Addison's disease, vitiligo, myasthenia gravis and pernicious anemia. In addition we studied two individuals with Graves' disease from each of two families residing outside Louisiana, all of whom were positive for these antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Markers of foamy virus infections in monkeys, apes, and accidentally infected humans: appropriate testing fails to confirm suspected foamy virus prevalence in humans

Foamy viruses (FVs) persist in healthy individuals of various mammalian species, including nonhuman primates. Laboratory markers of FV infection are (1) virus in throat epithelium or peripheral blood lymphocytes (PBLs), (2) proviral DNA sequences in PBLs and various solid organs, and (3) antibodies reactive to viral antigens on Western blots, in radioimmunoprecipitation tests, and in immunofluorescence assays. Using PCR and serological tests, we readily detected FV markers in naturally infected African green monkeys, rhesus monkeys, and chimpanzees, as well as in accidentally infected humans. Transmission of simian foamy viruses to humans (by bite or inadvertent laboratory infection) leads to viral markers, without affecting the recipient. Reports on FV-associated clinical disorders (e.g., thyroid or neurological) have remained controversial. In this study we failed to detect, by PCR, viral sequences in the samples from 223 patients, including 16 HIV-infected Africans, 46 Graves' disease patients, and 28 patients with the de Quervain's thyroiditis. Evaluation of 2688 sera from suspected high-risk areas (e.g., Central and East Africa, or high-risk groups such as HIV-infected individuals and patients with AIDS, thyroid, and neurological disorders) did not reveal FV-specific antibodies in a single case. Previously reported FV seroprevalence in various populations has never been verified by appropriate confirmatory tests. The strain of "human foamy virus" has remained a unique isolate. In conclusion, FVs are unlikely--at present--to circulate in human populations.

Isolation of a new foamy retrovirus from orangutans

We have isolated a new foamy virus from blood samples taken from two apparently healthy orangutans (Pongo pygmaeus). The older orangutan has since died with encephalopathy after a brief acute illness, while the younger one, his grandson, remains well. These animals and 12 other orangutans had specific antibodies to foamy virus as measured by immunofluorescence. The new foamy virus and the antisera showed strong and specific neutralization, with only weak cross-reaction with other simian foamy virus strains. Southern blotting with gag and env probes of human foamy virus and PCR amplification showed that the new foamy virus, designated SFV-11, is related to, yet distinct from, previously characterized strains from humans, chimpanzees, and monkeys.

Lymphocytic traffic and homing into target tissue and the generation of endocrine autoimmunity

Endocrine autoimmunity is known to be characterized by the presence of specific autoantibodies and from the histopathological point of view by lymphocytic infiltration in the target tissue. The presence of mononuclear cell infiltrates is the pathological hallmark of most endocrine diseases characterized by an autoimmune process directed against antigens expressed on endocrine cells. Infiltrating cells can usually be detected by biopsy or by using other, non-invasive, techniques. However, in endocrine tissue such as the islets of Langerhans and the adrenal glands it is difficult to perform biopsies and diagnosis of the autoimmune process is dependent mainly upon detection of specific autoantibodies. A crucial aspect of endocrine autoimmunity and of all processes of organ specific autoimmunity is why and how lymphocytes migrate from primary lymphoid tissue to their specific targets. This occurs mainly through contact with specific adhesion molecules which enable lymphocytes to adhere to the endothelial vessels in close proximity to the target tissue. In this review we discuss the homing of peripheral mononuclear cells into target endocrine tissues and the mediating role of adhesion molecules.

Phylogenesis and genetic complexity of the nonhuman primate retroviridae

The three known groups of nonhuman primate retroviruses (simian immunodeficiency virus, simian T cell lymphotropic/leukemic virus type I, and simian foamy virus) are thought to have equivalent human counterparts. This is clearly the case with human immunodeficiency virus types 1 and 2, the causative agents of acquired immunodeficiency syndrome, and with human T cell lymphotropic/leukemia virus type I (HTLV-I), which causes T cell leukemia and a progressive form of myelopathy (tropical spastic paraparesis/HTLV-I-associated myelopathy), and HTLV-II. However, the presence of spumaviruses (foamy viruses) in humans remains uncertain. Data accumulated in the last 5 years suggest the possibility that the human retroviruses are indeed the result of transmission of simian retroviruses to humans. In this article we attempt to parallel the genetic features of the simian retroviridae with their human counterparts and argue for the possibility of horizontal transmission of these viruses from monkeys to humans.

Absence of foamy virus DNA in Graves' disease

A report on the high prevalence of foamy virus DNA in lymphocytes from French patients with Graves' disease prompted us to investigate a similar cohort of 41 German patients. Using PCR amplification and Southern blot hybridization, we detected foamy virus DNA only in lymphocytes of two accidentally infected humans and five naturally infected monkeys, as well as in DNA samples from four Graves' disease patients investigated in the French study. However, we failed to detect foamy virus DNA in peripheral blood lymphocytes from any of the 41 Graves' disease patients of the German cohort. Thus, a causative role of foamy viruses in this thyroid disease is highly improbable.

Etiopathology of feline toxic nodular goiter

We have discussed the etiopathology of feline toxic nodular goiter in the context of human nodular goiter pathogenesis. We have reviewed thyroid heterogeneity, growth regulation, functional and growth autonomy, nodule and tumor formation, and the evolution of toxic nodular goiter in the human being. By addressing toxic nodular goiter of the cat, the history, morphologic findings, xenotransplantation and cell culture studies, evidence for and against circulating thyroid stimulators and epizootiological studies of the feline disease have been summarized. Due to its structure, the thyroid gland offers some unique possibilities to study the mechanisms that are responsible for cellular heterogeneity, the emergence of autonomous nodular growth and function, and, ultimately, the development of tumors. The demonstration of naturally occurring clones of cells with high intrinsic proliferation potential within the follicular epithelium of the thyroid has fostered promising new concepts on the genesis of nodular growth of benign and possibly malignant endocrine tumors. Hyperthyroid cat goiters contain single or multiple, autonomously (i.e., TSH-independently) functioning and growing nodules. Neither hyperfunction nor growth of these nodules depends on extrathyroidal circulating stimulators. The basic lesion appears to be an excessive intrinsic growth capacity of some thyroid cells. The factors enhancing the transformation of a normal thyroid into a nodular hyperfunctioning goiter over many years are still unknown. Immunological, environmental, and nutritional factors are the focus of ongoing studies, but an infectious agent can not yet be excluded.