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

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.

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.

A novel and major association of HLA-C in Graves' disease that eclipses the classical HLA-DRB1 effect

Association of the major histocompatibility complex (MHC) class II-encoded HLA-DRB1-DQA1-DQB1 haplotype with Graves' disease (GD) has been known for several years. Recent evidence from other autoimmune diseases has suggested that the HLA class I encoded HLA-B/-C molecules could be conferring HLA-DRB1-DQA1-DQB1 independent effects on disease. The aim of this study was to determine the effect of HLA-B and HLA-C in GD in a white ethnic group of 806 patients with GD and 487 control subjects from the UK. Of the five loci (HLA-B, -C, -DRB1, -DQA1, -DQB1), HLA-C demonstrated the strongest association (P = 1.20 x 10(-20)) with HLA-C*07 predisposing [OR = 1.63, 95% CI (1.23-2.17)] and both HLA-C*03 [OR = 0.54, 95% CI (0.38-0.77)], HLA-C*16 [OR = 0.36, 95% CI (0.21-0.61)] protective. The other loci were then tested for HLA-C-independent associations. HLA-B was found to be associated independently of HLA-C (P = 1.54 x 10(-6)) with the other three loci, HLA-DRB1, HLA-DQB1 and HLA-DQA1, also improving the model but with less confidence (P > 10(-5)). This study has for the first time provided evidence of a primary association of HLA-C, and to a lesser extent HLA-B, with GD. Class II loci could still have effects on GD, but they appear smaller than the HLA-C association. A full investigation of the MHC region, including all class I and II loci is now required. Our results point to a primary role for class I-mediated responses in GD, a condition classically assumed to be a straightforward HLA-class II-restricted autoantibody response to the thyroid stimulating hormone receptor.

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.

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.