Understanding the Neurotrophic Virus Mechanisms and Their Potential Effect on Systemic Lupus Erythematosus Development

Central nervous system (CNS) pathologies are a public health concern, with viral infections one of their principal causes. These viruses are known as neurotropic pathogens, characterized by their ability to infiltrate the CNS and thus interact with various cell populations, inducing several diseases. The immune response elicited by neurotropic viruses in the CNS is commanded mainly by microglia, which, together with other local cells, can secrete inflammatory cytokines to fight the infection. The most relevant neurotropic viruses are adenovirus (AdV), cytomegalovirus (CMV), enterovirus (EV), Epstein-Barr Virus (EBV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2), lymphocytic choriomeningitis virus (LCMV), and the newly discovered SARS-CoV-2. Several studies have associated a viral infection with systemic lupus erythematosus (SLE) and neuropsychiatric lupus (NPSLE) manifestations. This article will review the knowledge about viral infections, CNS pathologies, and the immune response against them. Also, it allows us to understand the relevance of the different viral proteins in developing neuronal pathologies, SLE and NPSLE.

Rheumatoid arthritis and systemic lupus erythematosus: Pathophysiological mechanisms related to innate immune system

Rheumatoid arthritis and systemic lupus erythematosus are two highly prevalent autoimmune diseases that generate disability and low quality of life. The innate immune system, a long-forgotten issue in autoimmune diseases, is becoming increasingly important and represents a new focus for the treatment of these entities. This review highlights the role that innate immune system plays in the pathophysiology of rheumatoid arthritis and systemic lupus erythematosus. The role of the innate immune system in rheumatoid arthritis and systemic lupus erythematosus pathophysiology is not only important in early stages but is essential to maintain the immune response and to allow disease progression. In rheumatoid arthritis, genetic and environmental factors are involved in the initial stimulation of the innate immune response in which macrophages are the main participants, as well as fibroblast-like synoviocytes. In systemic lupus erythematosus, all the cells contribute to the inflammatory response, but the complement system is the major effector of the inflammatory process. Detecting alterations in the normal function of these cells, besides its contribution to the understanding of the pathophysiology of autoimmune diseases, could help to establish new treatment strategies for these diseases.

The role of infections in neuropsychiatric lupus

Opportunistic infections can cause manifestations that resemble neuropsychiatric systemic lupus erythematosus and they can also trigger lupus flares. Therefore, central nervous system infections as differential diagnosis in neuropsychiatric systemic lupus erythematosus may be difficult, leading to delayed diagnosis and specific treatment. Central nervous system infection in systemic lupus erythematosus is not common but, if left misdiagnosed and not treated promptly, can be fatal. Complementary diagnosis tests are generally non-specific and disappointing. Caution with immunosuppressive drug treatment should be emphasized while an opportunistic infection cannot be ruled out. In this review, we discuss the various types of central nervous system infections reported in systemic lupus erythematosus patients, highlighting the importance of their early recognition in order to improve morbidity and mortality. Prevention with vaccination is a recommended approach.

Prevalence of celiac disease in latin america: a systematic review and meta-regression

BACKGROUND

Celiac disease (CD) is an immune-mediated enteropathy triggered by the ingestion of gluten in susceptible individuals, and its prevalence varies depending on the studied population. Given that information on CD in Latin America is scarce, we aimed to investigate the prevalence of CD in this region of the world through a systematic review and meta-analysis.

METHODS AND FINDINGS

This was a two-phase study. First, a cross-sectional analysis from 981 individuals of the Colombian population was made. Second, a systematic review and meta-regression analysis were performed following the Preferred Reporting Items for Systematic Meta- Analyses (PRISMA) guidelines. Our results disclosed a lack of celiac autoimmunity in the studied Colombian population (i.e., anti-tissue transglutaminase (tTG) and IgA anti-endomysium (EMA)). In the systematic review, 72 studies were considered. The estimated prevalence of CD in Latin Americans ranged between 0.46% and 0.64%. The prevalence of CD in first-degree relatives of CD probands was 5.5%. The coexistence of CD and type 1 diabetes mellitus varied from 4.6% to 8.7%, depending on the diagnosis methods (i.e., autoantibodies and/or biopsies).

CONCLUSIONS

Although CD seems to be a rare condition in Colombians; the general prevalence of the disease in Latin Americans seemingly corresponds to a similar scenario observed in Europeans.

Acute longitudinal myelitis following Cryptococcus laurentii pneumonia in a patient with systemic lupus erythematosus

Central nervous system (CNS) involvement in systemic lupus erythematosus (SLE) is reported in about 50% of patients. Among the neuropsychiatric features of SLE, myelopathy, including acute transverse myelitis (ATM) or acute longitudinal myelitis (ALM), represents an uncommon event. A possible vascular aetiology of SLE myelopathies has been hypothesized and it seems to be much more associated to SLE-associated antiphospholipid syndrome (APS). Furthermore, a possible infectious cause of ATM or ALM in healthy subjects has been described. SLE patients are susceptible to infection due to the disease itself or to the immunosuppressive therapy. Cryptococci non-neoformans have been rarely associated to infections in humans. Here we describe the case of a 47-year-old woman with SLE and Sjögren Syndrome who developed an ALM concurrently with a Cryptococcus laurentii pneumonia. The patient was treated with antimycotics, high doses of glucocorticoids and intravenous immunoglobulins with a significant clinical and radiological improvement. As far as we know, this is the first case of Cryptococcus laurentii infection and ALM in a patient with SLE who later developed a seronegative APS. Even though myelopathy may be considered primarily associated to SLE, a possible role of the infection in ALM development cannot be excluded.

Infections and systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that presents a protean spectrum of clinical manifestations, and may affect any organ. The typical course of SLE is insidious, slow, and progressive, with potential exacerbations and remissions, and even dramatically acute and rapidly fatal outcomes. Recently, infections have been shown to be highly associated with the onset and/or exacerbations of SLE, and their possible causative and/or protective role has been largely emphasized in the medical literature. However, the etiopathogenesis of SLE is still obscure and far from being completely elucidated. Among infections, particularly Epstein-Barr virus (EBV), parvovirus B19, retrovirus, and cytomegalovirus (CMV) infections might play a pivotal pathogenetic role. The multifaceted interactions between infections and autoimmunity reveal many possibilities for either causative or protective associations. Indeed, some infections, primarily protozoan infections, might confer protection from autoimmune processes, depending on the unique interaction between the microorganism and host. Further studies are needed in order to demonstrate that infectious agents might, indeed, be causative of SLE, and to address the potential clinical sequelae of infections in the field of autoimmunity.

The impact of rural residency on the expression and outcome of systemic lupus erythematosus: data from a multiethnic Latin American cohort

OBJECTIVE

The objective of this paper is to examine the role of place of residency in the expression and outcomes of systemic lupus erythematosus (SLE) in a multi-ethnic Latin American cohort.

PATIENTS AND METHODS

SLE patients (< two years of diagnosis) from 34 centers constitute this cohort. Residency was dichotomized into rural and urban, cut-off: 10,000 inhabitants. Socio-demographic, clinical/laboratory and mortality rates were compared between them using descriptive tests. The influence of place of residency on disease activity at diagnosis and renal disease was examined by multivariable regression analyses.

RESULTS

Of 1426 patients, 122 (8.6%) were rural residents. Their median ages (onset, diagnosis) were 23.5 and 25.5 years; 85 (69.7%) patients were Mestizos, 28 (22.9%) Caucasians and 9 (7.4%) were African-Latin Americans. Rural residents were more frequently younger at diagnosis, Mestizo and uninsured; they also had fewer years of education and lower socioeconomic status, exhibited hypertension and renal disease more frequently, and had higher levels of disease activity at diagnosis; they used methotrexate, cyclophosphamide pulses and hemodialysis more frequently than urban patients. Disease activity over time, renal damage, overall damage and the proportion of deceased patients were comparable in rural and urban patients. In multivariable analyses, rural residency was associated with high levels of disease activity at diagnosis (OR 1.65, 95% CI 1.06-2.57) and renal disease occurrence (OR 1.77, 95% CI 1.00-3.11).

CONCLUSIONS

Rural residency associates with Mestizo ethnicity, lower socioeconomic status and renal disease occurrence. It also plays a role in disease activity at diagnosis and kidney involvement but not on the other end-points examined.

Environment and lupus-related diseases

Clinical manifestations of lupus are encountered in a variety of disease entities, including isolated cutaneous lupus, undifferentiated connective tissue disease, mixed connective tissue disease, drug-induced lupus, overlap syndrome, and systemic lupus erythematosus (SLE). While each entity has been recognized as a specific disease with its own diverse clinical and serological pattern, one could argue that many findings are common. Could it be that all of these entities actually represent a spectrum of one disease? Could it be that rather than the genetic predisposition and hence controlled factors that govern this spectrum of diseases, that environmental factors associated with SLE could also play a role in the different entities of this spectrum? The traditional environmental triggers in SLE include sunlight and ultraviolet (UV) light, infections, smoking, and medications including biologics such as tumor necrosis factor alpha (TNF-a) blockers. In this review, we update and further substantiate these traditional factors in the various lupus-related syndromes. We will also discuss the association with vaccine exposure, industrial estrogens, and other factors.

Autoimmune bullous diseases the spectrum of infectious agent antibodies and review of the literature

Pemphigus and bullous pemphigoid are two autoimmune diseases that have a similar pathogenesis. Both have a genetic predisposition which promotes the production of auto-antibodies targeted against different components of the epidermal desmosome and hemidesmosome. Environmental factors play an important role in the pathogenesis of this autoimmune disease. Among these, the role of infectious agents was debated as a causative factor. We sought to determine a possible connection between various infectious agents and autoimmune bullous disease (ABD). A cohort of 148 serum samples of patients with pemphigus, bullous pemphigoid and controls was screened for evidence of a prior infection with HBV, HCV, EBV, CMV, Helicobacter pylori, Toxoplasma gondii and Treponema pallidum, utilizing the Bio-Rad BioPlex 2200 system as well as ELISA assays to complete the panel. HBV, HCV, H. pylori, T. gondii and CMV were demonstrated to have significantly higher prevalence of antibodies in patients with pemphigus and bullous pemphigoid in comparison to controls. Among them, we found a novel association between H. pylori and ABD. Our study suggests a contributing role for HBV, HCV, H. pylori, T. gondii and CMV in inducing ABD in the genetically susceptible host.

The pathogenesis of oligoarticular/polyarticular vs systemic juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) has had a long and difficult problem with classification. It is clearly a heterogeneous and multi-factorial autoimmune disease but all too often the distinctions among subtypes were unclear. In fact, there is now increasing evidence of a distinct pathogenesis of oligo/polyarticular JIA compared to systemic JIA. Oligo/polyarticular JIA is an antigen-driven lymphocyte-mediated autoimmune disease with abnormality in the adaptive immune system. Cartilage-derived auto-antigens activate autoreactive T cells including Th1 and Th17 cells with production of pro-inflammatory cytokines IFN-γ and IL-17. On the other hand, the inhibition of regulatory T (Treg) cells including natural Foxp3(+) Treg and self-heat shock protein-induced Treg cells with decreased anti-inflammatory cytokine IL-10 results in the loss of immune tolerance. Imbalance between autoreactive Th1/Th17 and Treg cells leads to the failure of T cell tolerance to self-antigens, which contributes to the synovial inflammation of oligo/polyarticular JIA. By contrast, systemic JIA is an autoinflammatory disease with abnormality in the innate immune system. A loss of control of the alternative secretory pathway leading to aberrant activation of phagocytes including monocytes, macrophages and neutrophils seems to be involved in the release of pro-inflammatory cytokines IL-1, IL-6, IL-18 and pro-inflammatory S100-proteins, which contribute to the multisystem inflammation of systemic JIA. Markedly distinct pathogenesis of oligo/polyarticular JIA and systemic JIA implies that they might need different treatment strategies.

Geoepidemiology of autoimmune rheumatic diseases

The accumulative global burden of autoimmune and inflammatory rheumatic diseases is substantial. Studying the distribution of these conditions across various global regions and ethnic groups by means of geoepidemiology might readily provide epidemiological data and also advance our understanding of their genetic and environmental underpinnings. In order to depict the geoepidemiology of autoimmune and inflammatory rheumatic diseases, namely rheumatoid arthritis, juvenile rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, ankylosing spondylitis and Sjögren's syndrome, we present a comprehensive collection of epidemiological reports from various world regions, including the prevalence of each of these conditions. The accumulated data show that the reviewed rheumatic diseases are global phenomena, and, with some variance, seem to be relatively evenly distributed. This finding is in contrast with the obviously uneven distribution of some major nonrheumatic autoimmune conditions. In addition, geoepidemiology demonstrates that ethnogenetic susceptibility interacts with lifestyle and environmental factors, which include socioeconomic status, infectious agents (triggering or protective agents), environmental pollutants, and vitamin D (dependent on sunlight exposure), in determining the risk of developing rheumatic autoimmunity.

Infectious antibodies in systemic lupus erythematosus patients

Infections can act as environmental triggers that induce or promote systemic lupus erythematosus (SLE) in genetically predisposed individuals. New technologies, developed recently, enable simultaneous assessment of multiple antibodies. Antibodies to specific infectious agents may shed light into the mechanisms of induction of SLE. The aim of this study was to investigate the prevalence of seropositivity and the titers of antibodies to bacterial, viral, and parasitic agents in SLE patients compared with non-autoimmune controls. Sera from 260 individuals (120 SLE patients and 140 controls) were tested by the BioPlex 2200 Multiplexed Immunoassay method (BioRad) for the prevalence and titers of antibodies to eight infectious agents (Epstein-Barr virus: early antigen IgG, nuclear antigen IgG, viral capsid antigen IgG and IgM, heterophile IgM; cytomegalovirus IgG and IgM; Toxoplasma gondii IgG and IgM; rubella IgG and IgM; Treponema pallidum TPr15G, TPr17G, TPr47G; herpes simplex virus type 1 and 2 IgG; hepatitis C virus and hepatitis B core antibodies. Cytomegalovirus IgM and Epstein-Barr virus early antigen IgG (but not other Epstein-Barr virus antigens) were significantly more prevalent in SLE patients than in controls. Conversely, positive titers of hepatitis B core and rubella IgG antibodies were less prevalent in the SLE patients than in controls. Other differences in titer positivity prevalence were not detected between patients and controls. The titers of the cytomegalovirus IgM, Toxoplasma IgG, Epstein-Barr virus early antigen, and viral capsid antigen IgG antibodies were significantly higher in SLE compared with controls. Our data suggest the importance of previous exposure to infectious agents in the induction and the prevention of SLE.

Parasitic infection and autoimmunity

Systemic lupus erythematosus is the prototypic multi-system autoimmune disease characterized by the production of multiple autoantibodies. The development of disease depends on a genetic predisposition and exposure to environmental factors including UV light, drugs, and infections. The association of parasitic infection and the development of autoimmune disease in general and lupus in particular remains elusive. In this paper, we review the recent evidence for protection from autoimmunity by parasites, models of parasite-related autoimmunity, molecular mimicry, the impact of parasitic molecules on the immune response and the association between parasitic load and the degree of autoimmunity.

A comprehensive evaluation of serum autoantibodies in primary biliary cirrhosis

In primary biliary cirrhosis (PBC) serum markers other than anti-mitochondrial antibodies (AMA) are promising in terms of disease severity and comorbidities, as well represented by anti-nuclear antibodies (ANA). The aim of the present study was thus to evaluate the prevalence and clinical significance of a large profile of serum autoantibodies in PBC sera. We utilized 69 sera from European patients with PBC (including 20 AMA-negative) and 297 sera from geographically and sex-matched healthy controls. All sera were tested for the presence of ANA and autoantibodies associated with thrombophilia, vasculitis, and gastrointestinal disease. Autoantibodies other than AMA were detected in 53/69 (76%) PBC sera vs. 105/297 (35%) among controls. The prevalence of ANA (targeting dsDNA, Sm, chromatin, ribosomal-P, RNP, SmRNP, SSA, SSB, and centromere) and thrombophilia-associated autoantibodies (i.e. anti-beta2GPI, phosphatydilserine, prothrombin) was common among patients with PBC. When clinical features were compared, the presence of anti-prothrombin IgM was associated with a worse prognosis as represented by a higher Mayo score. We demonstrate an increased prevalence of ANA and thrombophilia-associated autoantibodies in PBC sera and an association between the latter autoantibodies and PBC stage. The role of thrombophilia-associated antibodies will warrant further studies, based in particular on the incidence of portal hypertension at early stages of PBC.

Infectious serologies and autoantibodies in Wegener's granulomatosis and other vasculitides: novel associations disclosed using the Rad BioPlex 2200

In this study we assess the presence of antibodies against infectious agents as well as for a variety of autoantibodies in an attempt to establish associations between various vasculitides and infections in order to shed light on the etiopathogenesis of these diseases and perhaps implicate a potential cure. Sera from patients with Wegener's granulomatosis (WG), polyarteritis nodosa, microscopic polyangiitis, Churg Strauss, and giant cell arteritis were compared to healthy control sera. Serum samples were assessed, using the Bio-Rad BioPlex 2200, for the presence of Toxoplama gondii, cytomegalovirus (CMV), Epstein-Barr virus (EBV), Treponema pallidum, and Saccharomyces cerevisiae. Hepatitis B virus (HBV), hepatitis C virus (HCV), and anti-Helicobacter pylori antibodies were assessed by ELISA. In addition, sera were tested for a panel of antibodies associated with thrombophilia as well as various autoantibodies. The prevalence of antibodies toward HCV and H. pylori was significantly higher among patients with WG. IgG antibodies toward T. gondii and IgM antibodies toward CMV were significantly more common among WG patients than among controls. WG patients exhibited more antibodies toward EBV viral capsid antigen IgG and EBV early antigen IgG compared to sera from healthy controls. In WG, positive associations were disclosed between CMV IgG antibodies and the presence of gastrointestinal manifestations and renal involvement, and there was a higher Birmingham vasculitis activity score in association with elevated titers of EBV viral capsid antigen IgG antibodies. Otorhinolaryngeal manifestations were more common in those with positive IgG antibodies for EBV early antigen. Our results unveil novel associations between WG and various infectious agents, including HCV, H. pylori, T. gondii, CMV, and EBV. In addition to putative roles in initiation and exacerbation of the vasculitic process, it seems that these infectious agents also modulate the clinical phenotype of the disease.

Infection, vaccination, and autoantibodies in chronic fatigue syndrome, cause or coincidence?

Chronic fatigue syndrome (CFS) is a heterogeneous syndrome of unknown etiology and physiopathology. CFS patients complain about disabling fatigue, depression, difficulty with memory, and concomitant skeletal and muscular pain. Interestingly enough, there is certain overlap between CFS symptoms, autoimmune rheumatic disease, and infectious diseases. Certain neuroendocrine-immune abnormalities have also been described, and autoantibodies commonly described in some autoimmune diseases have been found in CFS patients as well. An increasing number of autoantibodies, mainly directed against other nuclear cell components, have been illustrated. Likewise, an association between some infectious agents, antibody production, and later CFS onset has been reported. Similarly, vaccination is depicted as playing an important role in CFS onset. Recently, a case report pointed toward a causal association between silicone breast linkage, hepatitis B virus vaccination, and CFS onset in a previous healthy woman. Such findings suggest that there is a likely deregulation of the immune system influenced by specific agents (infections, vaccination, and products, such as silicone). Evidence suggests that CFS is a complex disease in which several risk factors might interact to cause its full expression. Thus, although different alterations have been found in CFS patients, undoubtedly the main feature is central nervous system involvement with immunological alterations. Therefore, a new term neuro-psycho-immunology must be quoted. New studies based on this concept are needed in order to investigate syndromes, such as CFS, in which immunological alterations are thought to be associated with concomitant psychological and health disturbances.

Infectious serologies and autoantibodies in inflammatory bowel disease: insinuations at a true pathogenic role

The aim of this study was to reevaluate the role of infection in inflammatory bowel disease (IBD). Sera from 119 patients with IBD [80 with Crohn's disease (CD); 39 with ulcerative colitis] and 98 healthy controls were assessed using the Bio-Rad BioPlex 2200 for the presence of Toxoplasma gondii, cytomegalovirus, Epstein-Barr virus, Treponema pallidum, and Saccharomyces cerevisiae. Hepatitis B virus, hepatitis C virus (HCV), and anti-Helicobacter pylori antibodies were assessed by ELISA. In addition, sera were tested for a panel of antibodies associated with thrombophilia as well as various autoantibodies. Titers of antibodies toward HCV and T. gondii, and S. cerevisiae were higher in IBD patients than in controls, while the H. pylori autoantibodies were less prevalent among the patient population. Several thrombophilia-associated antibodies were more common in CD patients, and a single patient had a thromboembolic event. Our results show an excess of anti-HCV and anti-T. gondii antibodies among patients with IBD compared to healthy controls. Whereas the former may be the result of immunosuppression from the inflammatory disease itself or from the medications used to treat it, the latter association suggests that T. gondii is involved in the etiopathogenesis of IBD, and especially CD, in humans, as has been shown in the murine model. However, our findings also reiterate the positive association between CD and anti-S. cerevisiae antibodies as well as the negative association with H. pylori infections. These, in turn, lend indirect support to the "hygiene hypothesis" in IBD as well as the newly proposed role of commensal bacteria in the initiation of the disease process.

Anti-infectious antibodies and autoimmune-associated autoantibodies in patients with type I diabetes mellitus and their close family members

Type 1 diabetes mellitus (T1DM) is an autoimmune disease with complex interactions between genetic and environmental factors. We compared antibody levels to various infectious agents and of autoimmune-associated autoantibodies between Colombian T1DM patients, their close family members and healthy controls. Significantly lower levels of antibodies against several infectious agents were detected in the T1DM patients. These included Helicobacter pylori (P = 0.01), cytomegalovirus (P = 0.001), Epstein-Barr virus (P = 0.02) and Toxoplasma (P = 0.001). T1DM patients had significantly higher levels of IgG-anti-gliadin antibodies (P = 0.001) and IgG-antitissue transglutaminase antibodies (P = 0.03), and a borderline association with anticentromere antibodies (P = 0.06). The lower level of antibodies against infectious agents in T1DM patients may be related to their younger ages, but may also point to a protective role of those infections in T1DM development in susceptible individuals. Our results confirm the association between T1DM and celiac disease. A possible association with anticentromere antibody needs further studies.

Exposure to Epstein-Barr virus infection is associated with mild systemic lupus erythematosus disease

Infections may act as environmental triggers for the induction of systemic lupus erythematosus (SLE). In this study, we determine the relationship between disease manifestations of SLE patients and the titers of five Epstein-Barr virus (EBV) Abs. We evaluated the titers of early antigen IgG (EAG), nuclear antigen IgG, viral capsid antigen (VCA) IgG and IgM, and heterophile IgM, using the BioPlex 2200 multiplexed immunoassay method in 260 sera (120 SLE patients and 140 controls). EAG titers were significantly elevated (P < 0.024) in patients with cutaneous symptoms and increased anti-Ro antibody titers (P < 0.005). VCA IgG titers were significantly elevated (P < 0.003) in patients with joint involvement. None of the titers differed by central nervous system or renal involvement or antiphospholipid syndrome. We conclude that exposure to EBV infection may predict a disease phenotype of mild SLE disease with cutaneous and joint manifestations and elevated titers of anti-Ro Abs.

Helicobacters and extragastric diseases

For two decades, Helicobacter pylori has been considered as the culprit in many extragastric manifestations. However, for several of these supposed associations the hypothesis of an etiological role has not yet been fully investigated. This may be due to a series of factors linked to the epidemiological features of the studies and to the diseases investigated. This review attempts to highlight the main reported associations of H. pylori with extragastric manifestations during the last year. The most convincing data arise in the field of idiopathic thrombocytopenic purpura (ITP) and sideropenic anemia. Long-term follow-up studies have shown that 50% of subjects with ITP maintain a hematological response after H. pylori eradication. There is also growing evidence of the role of H. pylori in other diseases, including ischemic heart disease even though results are not conclusive.

Pathophysiology and clinical spectrum of infections in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an inflammatory and multisystemic autoimmune disorder characterized by an uncontrolled autoreactivity of B and T lymphocytes leading to the production of autoantibodies against self-directed antigens and tissue destruction. Environmental factors, such as infections, which are an important cause of morbidity and mortality, are potential triggers of the disease. This article discusses bacterial, viral, and opportunistic microorganism infections in SLE, and the role of immunosuppressive therapy and immunodeficiencies in the disease.

Infections and autoimmunity--friends or foes?

Autoimmunity can be triggered by many environmental factors, among which infectious agents are pivotal. Here, we summarize current knowledge of the relationship between infection and autoimmunity. An autoimmune disease can be induced or triggered by infectious agents, which can also determine its clinical manifestations. Most infectious agents, such as viruses, bacteria and parasites, can induce autoimmunity via different mechanisms. In many cases, it is not a single infection but rather the 'burden of infections' from childhood that is responsible for the induction of autoimmunity. The development of an autoimmune disease after infection tends to occur in genetically susceptible individuals. By contrast, some infections can protect individuals from specific autoimmune diseases (i.e. the hygiene hypothesis).

Prevalence of hepatitis C serum antibody in autoimmune diseases

OBJECTIVE

To evaluate the prevalence of serum antibodies against hepatitis C virus and other infectious agents in a large cohort of well-characterized patients with autoimmune diseases (AID).

METHODS

We utilized 1322 sera from patients with 18 different AID and 236 sera from healthy controls from the same countries and with similar age and sex distribution. All sera were tested for the presence of serum anti-hepatitis C virus (HCV) antibodies as well as antibodies directed at other infectious agents and autoantibodies.

RESULTS

Anti-HCV antibody was detected in 115/1322 (8.7%) of patients with AID and 0.4% of matched healthy controls (P < 0.0001). The prevalence of anti-HCV antibody was significantly higher in 7/18 different AID (i.e. cryoglobulinemia, mixed cryoglobulinemia pemphigus vulgaris, vasculitis, secondary anti-phospholipid syndrome, Hashimoto's thyroiditis, and inflammatory bowel disease) compared to controls. Patients with AID and serum anti-HCV positivity had an increased prevalence of antibodies against hepatitis B virus, Toxoplasma gondii and Cytomegalovirus as opposed to a lower frequency of serum autoantibodies.

CONCLUSIONS

The enhanced prevalence of anti-HCV serum antibodies in AID may suggest a role for HCV in tolerance to breakdown, similarly to its established role in mixed cryoglobulinemia. This immune mediated effect does not rule out the role of other infectious agents.