Sjögren's syndrome (SS) and Epstein-Barr virus (EBV) reactivation

Epstein-Barr virus as a potentiator of autoimmune diseases

The Epstein-Barr virus (EBV) is epidemiologically associated with development of autoimmune diseases, including systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis and multiple sclerosis. Although there is well-established evidence for this association, the underlying mechanistic basis remains incompletely defined. In this Review, we discuss the role of EBV infection as a potentiator of autoimmune rheumatic diseases. We review the EBV life cycle, viral transcription programmes, serological profiles and lytic reactivation. We discuss the epidemiological and mechanistic associations of EBV with systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis and multiple sclerosis. We describe the potential mechanisms by which EBV might promote autoimmunity, including EBV nuclear antigen 1-mediated molecular mimicry of human autoantigens; EBV-mediated B cell reprogramming, including EBV nuclear antigen 2-mediated dysregulation of autoimmune susceptibility genes; EBV and host genetic factors, including the potential for autoimmunity-promoting strains of EBV; EBV immune evasion and insufficient host responses to control infection; lytic reactivation; and other mechanisms. Finally, we discuss the therapeutic implications and potential therapeutic approaches to targeting EBV for the treatment of autoimmune disease.

Serological Evidence for the Association Between Epstein-Barr Virus Infection and Sjögren's Syndrome

Background

Exposure to Epstein-Barr virus (EBV) infection has been hypothesized to be an important risk factor for multiple rheumatic diseases, but the serological evidence so far for its role in Sjögren’s syndrome (SjS) is not clearly established yet. This study aimed to assess the seroepidemiological associations of antibodies to EBV with SjS.

Methods

A seroepidemiological study containing 119 patients with SjS and 65 healthy controls was first performed, in which the associations of SjS with four commonly studied EBV antibodies including IgM-anti-viral capsid antigen (anti-VCA) antibody, IgG-anti-VCA antibody, IgG-anti-early antigen (anti-EA) antibody, and IgG-anti-EBV nuclear antigen 1 (anti-EBNA1) antibody were evaluated. A systematic review and meta-analysis of eligible seroepidemiological studies was also carried out, and data syntheses were performed using random-effect meta-analysis.

Results

In the case-control study, the patients with SjS had both a significantly higher prevalence of IgG-anti-EA antibody positivity (31.9% vs. 3.1%, P < 0.001) and high titers of IgG-anti-EA antibody (P < 0.001) than healthy controls. The titer of IgG-anti-VCA antibody was significantly increased in the patients with SjS compared with healthy controls (P < 0.001). IgG-anti-EA antibody seropositive patients with SjS had lower levels of both C3 (P = 0.002) and C4 (P = 0.02), and the titer of IgG-anti-EA antibody was inversely related to the levels of both C3 (r = -0.31, P < 0.001) and C4 (r = -0.20, P = 0.03). A total of 14 eligible studies on the serological associations between EBV infection and SjS were finally included into the meta-analysis, which suggested obvious associations of SjS with IgM-anti-VCA antibody [Odds ratio (OR) = 5.77, 95%CI 1.73–19.25, P = 0.004] and IgG-anti-EA antibody (OR = 9.97, 95%CI 4.58-21.67, P < 0.00001).

Conclusions

The findings from this study provide strong serological evidence for the association between EBV infection and SjS. SjS has obvious associations with IgM-anti-VCA antibody and IgG-anti-EA antibody. IgG-anti-EA antibody is linked to low levels of C3 and C4 in the patients with SjS, the significance of which needs to be addressed in further studies.

Environmental factors in the pathogenesis of primary Sjögren's syndrome

Primary Sjögren's syndrome (SS) is a systemic autoimmune disease in which exocrine organs, primarily the salivary and lacrimal glands, are targets of chronic inflammation, leading to severe dryness of eyes and mouth. Fatigue and arthralgia are also common, and extraglandular manifestations involving the respiratory, nervous and vascular systems occur in a subset of patients. Persistent activation of the type I interferon system, and autoreactive B and T cells with production of disease-associated autoantibodies are central to the pathogenesis. Genetic polymorphisms that associate with an increased risk of SS have been described, though the risk-increase contributed by the respective variant is generally low. It is thus becoming increasingly clear that genetics cannot alone account for the development of SS and that other, presumably exogenous, factors must play a critical role. Relatively few studies have investigated exposure to potential risk factors prior to SS disease onset. Rather, many factors have been studied in prevalent cases. In this review, we summarize current literature on exogenous factors in the pathogenesis of SS including infections, hormones, smoking, solvents and additional compounds. We delineate for which factors there is current evidence of increased disease risk, and for which our present knowledge is confined to suggesting their role in SS pathogenesis. Finally, we outline future perspectives in the continued search for environmental risk factors for SS, a research area of great importance considering the possibilities for preventive measures.

New Viral Facets in Oral Diseases: The EBV Paradox

The oral cavity contributes to overall health, psychosocial well-being and quality of human life. Oral inflammatory diseases represent a major global health problem with significant social and economic impact. The development of effective therapies, therefore, requires deeper insights into the etiopathogenesis of oral diseases. Epstein–Barr virus (EBV) infection results in a life-long persistence of the virus in the host and has been associated with numerous oral inflammatory diseases including oral lichen planus (OLP), periodontal disease and Sjogren’s syndrome (SS). There is considerable evidence that the EBV infection is a strong risk factor for the development and progression of these conditions, but is EBV a true pathogen? This long-standing EBV paradox yet needs to be solved. This review discusses novel viral aspects of the etiopathogenesis of non-tumorigenic diseases in the oral cavity, in particular, the contribution of EBV in OLP, periodontitis and SS, the tropism of EBV infection, the major players involved in the etiopathogenic mechanisms and emerging contribution of EBV-pathogenic bacteria bidirectional interaction. It also proposes the involvement of EBV-infected plasma cells in the development and progression of oral inflammatory diseases. A new direction for preventing and treating these conditions may focus on controlling pathogenic EBV with anti-herpetic drugs.

The role of viral infections in the development of autoimmune diseases

The exact aetiology of most autoimmune diseases remains unknown, nonetheless, several factors contributing to the induction or exacerbation of autoimmune reactions have been suggested. These include the genetic profile and lifestyle of the affected individual in addition to environmental triggers such as bacterial, parasitic, fungal and viral infections. Infections caused by viruses usually trigger a potent immune response that is necessary for the containment of the infection; however, in some cases, a failure in the regulation of this immune response may lead to harmful immune reactions directed against the host's antigens. The autoimmune attack can be carried out by different arms and components of the immune system and through different possible mechanisms including molecular mimicry, bystander activation, and epitope spreading among others. In this review, we examine the data available for the involvement of viral infections in triggering or exacerbating autoimmune diseases in addition to discussing the mechanisms by which these viral infections and the immune pathways they trigger possibly contribute to the development of autoimmunity.

Discrepancy of Serological and Molecular Patterns of Circulating Epstein-Barr Virus Reactivation in Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is characterized by B cell hyperactivation, production of autoantibodies and increased risk of B cell lymphomas. Serological profile of Epstein-Barr virus (EBV) reactivation and increase EBV DNA levels in exocrine glands are observed in pSS, but whether these abnormalities are accompanied with disturbed systemic EBV control or have any association with pSS activity remains to be investigated. In this observational study, we initially explored anti-EBV antibodies and cell-free DNA in 395 samples from a cross-sectional plasma collection of pSS patients included in ASSESS French national cohort. Results were assessed in relation with disease activity. Further, to assess cell-associated EBV DNA we organized a case-control study including 20 blood samples from pSS patients followed in University Hospital Center of Montpellier. Results were compared with matched controls. Robust response against EBV early antigen (EA) was observed in pSS patients with anti-SSA/B (Sjögren's syndrome A and B) and anti-SSA autoantibodies compared to anti-SSA/B negatives (P < 0.01 and P = 0.01, respectively). Increased beta-2 microglobulin, kappa and lambda light chains, and immunoglobulin G levels were more frequently observed in anti-EA seropositive pSS subjects compared to anti-EA negative subjects (P < 0.001; P = 0.001; P = 0.003, respectively). Beta-2 microglobulin was independently associated with anti-EA positivity in multivariate analysis (P < 0.001). Plasma cell-free EBV DNA and EBV cellular reservoir was not different between pSS patients and controls. We conclude that serological evidence of EBV reactivation was more frequently observed and more strongly associated with anti-SSA/B status and B cell activation markers in pSS. However, serological profile of EBV reactivation was not accompanied by molecular evidence of systemic EBV reactivation. Our data indicated that EBV infection remains efficiently controlled in the blood of pSS patients.

Autoimmunity and the gut

Autoimmune diseases have increased dramatically worldwide since World War II. This is coincidental with the increased production and use of chemicals both in industrial countries and agriculture, as well as the ease of travel from region to region and continent to continent, making the transfer of a pathogen or pathogens from one part of the world to another much easier than ever before. In this review, triggers of autoimmunity are examined, principally environmental. The number of possible environmental triggers is vast and includes chemicals, bacteria, viruses, and molds. Examples of these triggers are given and include the mechanism of action and method by which they bring about autoimmunity.

Epstein-Barr virus in systemic autoimmune diseases

Systemic autoimmune diseases (SADs) are a group of connective tissue diseases with diverse, yet overlapping, symptoms and autoantibody development. The etiology behind SADs is not fully elucidated, but a number of genetic and environmental factors are known to influence the incidence of SADs. Recent findings link dysregulation of Epstein-Barr virus (EBV) with SAD development. EBV causes a persistent infection with a tight latency programme in memory B-cells, which enables evasion of the immune defence. A number of immune escape mechanisms and immune-modulating proteins have been described for EBV. These immune modulating functions make EBV a good candidate for initiation of autoimmune diseases and exacerbation of disease progression. This review focuses on systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and Sjögren's syndrome (SS) and sum up the existing data linking EBV with these diseases including elevated titres of EBV antibodies, reduced T-cell defence against EBV, and elevated EBV viral load. Together, these data suggest that uncontrolled EBV infection can develop diverse autoreactivities in genetic susceptible individuals with different manifestations depending on the genetic background and the site of reactivation.