The Epstein-Barr virus in autoimmunity

The epidemiology, pathology and pathogenesis of MS: Therapeutic implications

Multiple sclerosis (MS) is a chronic, and potentially disabling, inflammatory disease of the central nervous system (CNS). MS is generally characterized by recurrent, and self-limited, episodes of neurological dysfunction, which occur unpredictably and often result in multifocal tissue injury within the CNS. Currently, women are affected two to three times as often as men although this may not have been the case during earlier Time-Periods. The pathogenesis of MS is known to involve both critical genetic and environmental mechanisms. Nevertheless, in addition to these two mechanisms, disease-pathogenesis also involves a "truly" random event. Indeed, it is this random mechanism, which is responsible for the currently-observed (and increasing) excess of women among patients with MS. This review summarizes the current state of knowledge regarding the pathogenesis of MS (includong its epidemiology, pathology, and genetics) and considers the therapeutic implications that these pathogenetic mechanisms have both for our currently available therapies as well as for the possible therapeutic approaches to the management of this potentially disabling condition in the future.

Clonal landscape of autoantibody-secreting plasmablasts in COVID-19 patients

Whereas severe COVID-19 is often associated with elevated autoantibody titers, the underlying mechanism behind their generation has remained unclear. Here we report clonal composition and diversity of autoantibodies in humoral response to SARS-CoV-2. Immunoglobulin repertoire analysis and characterization of plasmablast-derived monoclonal antibodies uncovered clonal expansion of plasmablasts producing cardiolipin (CL)-reactive autoantibodies. Half of the expanded CL-reactive clones exhibited strong binding to SARS-CoV-2 antigens. One such clone, CoV1804, was reactive to both CL and viral nucleocapsid (N), and further showed anti-nucleolar activity in human cells. Notably, antibodies sharing genetic features with CoV1804 were identified in COVID-19 patient-derived immunoglobulins, thereby constituting a novel public antibody. These public autoantibodies had numerous mutations that unambiguously enhanced anti-N reactivity, when causing fluctuations in anti-CL reactivity along with the acquisition of additional self-reactivities, such as anti-nucleolar activity, in the progeny. Thus, potentially CL-reactive precursors may have developed multiple self-reactivities through clonal selection, expansion, and somatic hypermutation driven by viral antigens. Our results revealed the nature of autoantibody production during COVID-19 and provided novel insights into the origin of virus-induced autoantibodies.

The epidemiology of multiple sclerosis: insights to a causal cascade

MS-pathogenesis involves both genetic-susceptibility and environmental determinants. Three (or more) sequential environmental-factors are implicated. The first acts near birth, the second acts during childhood/adolescence, and the third acts subsequently. Two candidate factors (vitamin D deficiency and Epstein-Barr viral infection) seem particularly well-suited to the first two environmental-events but other factors (e.g., obesity and smoking behavior) seem also to be involved in the causal scheme. MS-pathogenesis can be modeled by incorporating both the environmental and genetic-factors into a causal scheme, which can then help to explain some of the changes in MS-epidemiology (e.g., increasing disease-prevalence, changing sex-ratio, and regional-variations in monozygotic-twin-concordance-rates), which have been taking place recently. This model suggests that genetic-susceptibility is overwhelmingly the most important determinant of MS and that, at least, 92.5% of individuals (and likely much more) are, essentially, incapable of developing MS, regardless of their specific environmental-exposures. Nevertheless, the genetics is complex and the contribution of any specific gene to MS-susceptibility seems to be quite modest. Thus, even for the DRB1*1501 allele (the strongest known MS-susceptibility marker), most carriers are not in the genetically-susceptible group. Moreover, 45-50% of individuals with MS lack this allele entirely and some of the haplotypes that carry this allele don't also confer any disease-risk. Finally, because the prevalence of genetic-susceptibility seems to be so similar throughout North America and Europe, and despite the crucial importance of a person's genetic make-up to disease pathogenesis, it is the environmental-factors, which largely responsible for the observed regional variations in disease-characteristics. Thus, despite MS being more common in women, men are more likely to be genetically-susceptible. This apparent paradox seems to relate to the fact that women are much more responsive than men to the recent changes in environmental-exposure (whatever these have been). These gender-differences may help to explain changes in the sex-ratio and the increasing disease-prevalence, which have both been observed recently. The potential importance of these conclusions regarding the role of environment in MS-pathogenesis is that they open the door to the possibility of pursuing strategies for primary primary disease prevention in the future.

The epidemiology of multiple sclerosis: insights to disease pathogenesis

The purpose of studying the epidemiology of multiple sclerosis (MS) is twofold. First, it is important to understand clearly the natural history of the illness in order to assist patients in making decisions about their future with respect to issues such as family planning, the importance of securing lifelong healthcare, their ability to get and maintain employment, and making appropriate choices of therapy for their particular circumstances. This is not to suggest that, even with the best possible information, the ultimate prognosis for any individual can be predicted with absolute accuracy. It cannot. Nevertheless, accurate information can be very helpful both to reassure patients that many individuals with MS do remarkably well in the long term (perhaps, especially, with current and future therapies) and also to empower individuals with respect to their ability to make their own life choices. Second, and arguably the more important purpose for studying the epidemiology of MS, is to gain insights to the underlying causes of the disease. Indeed, if the principal mechanisms of disease pathogenesis were to be understood clearly, then it might be possible to entertain notions of either a cure for existing disease or the primary prevention of future disease. Much of our current understanding of disease pathogenesis, as discussed in other chapters of this volume, has been derived from basic science investigations of animal models of MS such as experimental autoimmune encephalomyelitis (EAE), and these models have provided considerable insight both to the complexity of the mammalian immune system and to the mechanisms underlying its dysfunction in inflammatory autoimmune conditions. Nevertheless, MS is a disease of humans without any known, naturally occurring, counterpart in any nonhuman species. For this reason, the clues to disease pathogenesis provided by a study of basic epidemiologic facts regarding MS (and by a systematic consideration of their implications) are essential to a comprehensive understanding of the human illness we call MS.

Multiple sclerosis: autoimmune disease or autoimmune reaction?

Multiple sclerosis (MS) is traditionally considered an autoimmune inflammatory demyelinating disease of the central nervous system (CNS) with much knowledge available to support this view. However, this characterization implies that the primary event is an aberrant immune response directed at CNS antigens, promoting inflammation and later driving progressive axo-glial degeneration. Trials with potent anti-inflammatory agents and detailed neuropathological studies raise questions about this sequence of events. This hypothetical paper argues that MS may be primarily a "cytodegenerative" disease, possibly first involving the oligodendrocyte/myelin unit. Liberation of autoantigens secondarily recruits an immune response, the force of which heavily depends on the host's immune predisposition. Thus, the spectrum of MS from highly aggressive Marburg type, to primary progressive disease with little inflammatory burden, is governed by a "convolution" between the underlying cytodegeneration and the host's immune predilection. Clinical heterogeneity may be a reflection of a variable immune response, whereas in reality, the "real MS" may be a homogeneous degenerative process analogous to well known primary neurodegenerative diseases.

Association analysis of anti-Epstein-Barr nuclear antigen-1 antibodies, anti-cyclic citrullinated peptide antibodies, the shared epitope and smoking status in Brazilian patients with rheumatoid arthritis

INTRODUCTION

Epstein-Barr virus exposure appears to be an environmental trigger for rheumatoid arthritis that interacts with other risk factors. Relationships among anti-cyclic citrullinated peptide antibodies, the shared epitope, and smoking status have been observed in patients with rheumatoid arthritis from different populations.

OBJECTIVE

To perform an association analysis of anti-Epstein-Barr nuclear antigen-1 antibodies, anti-cyclic citrullinated peptide antibodies, the shared epitope, and smoking status in Brazilian patients with rheumatoid arthritis.

METHODS

In a case-control study, 140 rheumatoid arthritis patients and 143 healthy volunteers who were matched for age, sex, and ethnicity were recruited. Anti-Epstein-Barr nuclear antigen-1 antibodies and anti-cyclic citrullinated peptide antibodies were examined using an enzyme-linked immunosorbent assay, and shared epitope alleles were identified by genotyping. Smoking information was collected from all subjects. A comparative analysis of anti-Epstein-Barr nuclear antigen-1 antibodies, anti-cyclic citrullinated peptide antibodies, the shared epitope, and smoking status was performed in the patient group. Logistic regression analysis models were used to analyze the risk of rheumatoid arthritis.

RESULTS

Anti-Epstein-Barr nuclear antigen-1 antibodies were not associated with anti-cyclic citrullinated peptide antibodies, shared epitope alleles, or smoking status. Anti-cyclic citrullinated peptide antibody positivity was significantly higher in smoking patients with shared epitope alleles (OR = 3.82). In a multivariate logistic regression analysis using stepwise selection, only anti-cyclic citrullinated peptide antibodies were found to be independently associated with rheumatoid arthritis (OR = 247.9).

CONCLUSION

Anti-Epstein-Barr nuclear antigen-1 antibodies did not increase the risk of rheumatoid arthritis and were not associated with the rheumatoid arthritis risk factors studied. Smoking and shared epitope alleles were correlated with anti-cyclic citrullinated peptide-antibody-positive rheumatoid arthritis. Of the risk factors, only anticyclic citrullinated peptides antibodies were independently associated with rheumatoid arthritis susceptibility.

The causal cascade to multiple sclerosis: a model for MS pathogenesis

BACKGROUND

MS pathogenesis seems to involve both genetic susceptibility and environmental risk factors. Three sequential factors are implicated in the environmental risk. The first acts near birth, the second acts during childhood, and the third acts long thereafter. Two candidate factors (vitamin D deficiency and Epstein-Barr viral infection) seem well suited to the first two environmental events.

METHODOLOGY/PRINCIPAL FINDINGS

A mathematical Model for MS pathogenesis is developed, incorporating these environmental and genetic factors into a causal scheme that can explain some of the recent changes in MS-epidemiology (e.g., increasing disease prevalence, a changing sex-ratio, and regional variations in monozygotic twin concordance rates).

CONCLUSIONS/SIGNIFICANCE

This Model suggests that genetic susceptibility is overwhelmingly the most important determinant of MS pathogenesis. Indeed, over 99% of individuals seem genetically incapable of developing MS, regardless of what environmental exposures they experience. Nevertheless, the contribution of specific genes to MS-susceptibility seems only modest. Thus, despite HLA DRB1*1501 being the most consistently identified genetic marker of MS-susceptibility (being present in over 50% of northern MS patient populations), only about 1% of individuals with this allele are even genetically susceptible to getting MS. Moreover, because genetic susceptibility seems so similar throughout North America and Europe, environmental differences principally determine the regional variations in disease characteristics. Additionally, despite 75% of MS-patients being women, men are 60% more likely to be genetically-susceptible than women. Also, men develop MS at lower levels of environmental exposure than women. Nevertheless, women are more responsive to the recent changes in environmental-exposure (whatever these have been). This explains both the changing sex-ratio and the increasing disease prevalence (which has increased by a minimum of 32% in Canada over the past 35 years). As noted, environmental risk seems to result from three sequential components of environmental exposure. The potential importance of this Model for MS pathogenesis is that, if correct, a therapeutic strategy, designed to interrupt one or more of these sequential factors, has the potential to markedly reduce or eliminate disease prevalence in the future.

Pathophysiological links between rheumatoid arthritis and the Epstein–Barr virus: An update

Numerous associations have been documented between the Epstein-Barr virus (EBV) and rheumatoid arthritis (RA). Thus, anti-EBV antibody titers are higher in RA patients than in healthy controls. Lymphocytes from RA patients show impaired responses to EBV. Several EBV antigens share similarities with self antigens; more specifically, the glycine/alanine repeats in EBNA-1 resemble synovial proteins and the EBV gp110 glycoprotein contains a copy of the shared epitope. Cell-mediated responses to EBV replicative cycle proteins and to gp110 have been documented in joint fluid from RA patients. In situ hybridization and PCR techniques have identified EBV antigens and genetic material within the rheumatoid synovium, albeit with variable yields. The EBV burden in peripheral blood mononuclear cells is higher in RA patients than in controls. EBNA-1 can undergo citrullination, and the EBV can induce antibodies to citrullinated peptides. RA patients are at increased risk for lymphoma, including EBV-associated lymphoma. Despite these multiple and complex links between EBV and RA, proof of a causal association is lacking. EBV infection may contribute indirectly to the pathophysiology of RA by impairing immune control of EBV replication, causing increased exposure to EBV antigens and, thereby, chronic inflammation. The effect of biotherapies for RA on EBV-host relations needs to be investigated.

Murine γ-Herpesvirus 68 Limits Naturally Occurring CD4+CD25+T Regulatory Cell Activity following Infection

During microbial infections, naturally occurring CD4+CD25+ T regulatory cells can suppress protective host responses or they can limit pathogen-induced inflammatory responses. The particular role played by these cells seems to depend upon the infectious agent being investigated. Gamma-herpesviruses are efficacious pathogens which are well-known for their ability to induce lymphoproliferative disease and to establish latency in the host. However, no studies have investigated the importance of naturally occurring CD4+CD25+ T regulatory cells during infection with these viruses. Using the murine model of gamma-herpesvirus infection, murine gamma-herpesvirus 68 (gammaHV-68), we were surprised to find that levels of the CD4+CD25+ T regulatory cell transcript, FoxP3, continued to decrease as viral latency increased and as the leukocytosis phase of the disease progressed. Consistent with these results, the decrease in FoxP3 protein expression followed similar kinetics. Along with the reduced expression of this regulatory T cell marker, we also observed diminished CD4+CD25+ T regulatory cell activity in these cells isolated from gammaHV-68-infected animals. Dendritic cells infected in vitro with gammaHV-68 did not alter the ability of normal CD4+CD25+ regulatory T cells to limit the proliferation of CD4+ Th cells following stimulation. Taken together, these studies demonstrate a decreased presence and activity of CD4+CD25+ T regulatory cells during the mononucleosis-like phase of this viral infection. These alterations in naturally occurring T regulatory cell function may help to explain the dysregulation of the host's immune response which allows the uncontrolled expansion of leukocytes as viral latency is established.

A Mouse Herpesvirus Induces Relapse of Experimental Autoimmune Arthritis by Infection of the Inflammatory Target Tissue

It is not known what is required for successive relapses in autoimmune diseases or evolution to a progressive chronic disease. Autoimmune arthritis caused by passive transfer of autoantibodies against glucose 6-phosphate isomerase is transient and therefore lends itself well to test for what might extend the disease. Herpesviruses have long been suspected of contributing to human autoimmune disease. We infected mice with a murine gamma-herpesvirus (MHV-68). In immunodeficient mice, transient arthritis was followed by a relapse. This was due to lytic viral infection of synovial tissues demonstrated by PCR, immunohistochemistry, and electron microscopy. Latent infection could be reactivated in the synovium of normal mice when treated with Cytoxan and this was associated with increased clinical arthritis. We conclude that herpesviruses may play an ancillary pathogenic role in autoimmune arthritis by infection of the inflammatory target tissue.

Patients with systemic lupus erythematosus have abnormally elevated Epstein-Barr virus load in blood

Various genetic and environmental factors appear to be involved in systemic lupus erythematosus (SLE). Epstein–Barr virus (EBV) is among the environmental factors that are suspected of predisposing to SLE, based on the characteristics of EBV itself and on sequence homologies between autoantigens and EBV antigens. In addition, higher titers of anti-EBV antibodies and increased EBV seroconversion rates have been observed in SLE patients as compared with healthy control individuals. Serologic responses do not directly reflect EBV status within the body. Clarification of the precise status of EBV infection in SLE patients would help to improve our understanding of the role played by EBV in this disease. In the present study we determined EBV types in SLE patients (n = 66) and normal control individual (n = 63) by direct PCR analysis of mouthwash samples. We also compared EBV load in blood between SLE patients (n = 24) and healthy control individuals (n = 29) using semiquantitative PCR assay. The number of infections and EBV type distribution were similar between adult SLE patients and healthy control individuals (98.5% versus 94%). Interestingly, the EBV burden in peripheral blood mononuclear cells (PBMCs) was over 15-fold greater in SLE patients than in healthy control individuals (mean ± standard deviation: 463 ± 570 EBV genome copies/3 μg PBMC DNA versus 30 ± 29 EBV genome copies/3 μg PBMC DNA; P = 0.001), suggesting that EBV infection is abnormally regulated in SLE. The abnormally increased proportion of EBV-infected B cells in the SLE patients may contribute to enhanced autoantibody production in this disease.

EBV-encoded latent membrane protein 1 cooperates with BAFF/BLyS and APRIL to induce T cell-independent Ig heavy chain class switching

By substituting the H chain C region of IgM with that of IgG, IgA, or IgE, class switching enables Abs to acquire new effector functions that are crucial for the neutralization of invading pathogens. Class switching occurs through class switch DNA recombination (CSR) and usually requires engagement of CD40 on B cells by CD40 ligand on Ag-activated CD4(+) T cells. CSR must be tightly regulated because abnormal IgG and IgA production favors the onset of autoimmunity, whereas increased switching to IgE leads to atopy. These inflammatory disorders can be triggered or exacerbated by EBV infection. In this study, we show that EBV induces CD40-independent CSR from C( micro ) to multiple downstream C(gamma), C(alpha), and C(epsilon) genes through latent membrane protein 1 (LMP1), a CD40-like viral protein that signals in a ligand-independent fashion. LMP1-induced CSR is associated with transcriptional activation of germline C(gamma), C(alpha), and C(epsilon) genes and triggers the up-regulation of activation-induced cytidine deaminase, a crucial component of the CSR machinery. In addition, LMP1 induces B cells to express B cell-activating factor of the TNF family and a proliferation-inducing ligand, two molecules that mediate B cell survival and T cell-independent Ab production. B cell-activating factor of the TNF family and a proliferation-inducing ligand cooperate with LMP1 to induce Ig class switching because their neutralization by appropriate soluble decoy receptors attenuates CSR in LMP1-expressing B cells. By showing that LMP1 triggers T cell-independent CSR, our findings suggest that EBV could play an important role in the pathogenesis of disorders with aberrant IgG, IgA, and/or IgE production.

Virus-induced immune dysregulation as a triggering factor for the development of drug rashes and autoimmune diseases: with emphasis on EB virus, human herpesvirus 6 and hepatitis C virus

There are a considerable amount of empirical and theoretic medical literature regarding the possible role of viruses in the development of drug rashes and autoimmune diseases: under these conditions, interactions of viruses with the immune system would serve as an accelerating factor of disease pathogenesis. Recent reports have provided evidence to indicate that immune responses against infections with Epstein Barr (EB) virus and human herpesvirus 6 (HHV-6), which are lymphotropic members of the herpes virus group, not only aid the direct elimination of the virus but also contribute to a favorable milieu for the initiation or acceleration of drug rashes. Viruses that can persist for the lifetime of the host despite strong immune responses against them, such as EB virus and hepatitis C virus (HCV), would be also relevant to the pathogenesis of autoimmune diseases. HCV has been reportedly associated with a wide variety of dermatoses that, in common, show histologically the lichenoid tissue reaction. Although porokeratosis that manifests lichenoid histopathological features had long been regarded as being associated with immunosuppression, we found that HCV could act as trigger for the development of porokeratosis during states of immunosuppression. Thus, the main purpose of this review is to describe recent work on the etiology of drug rashes and autoimmune disease with special reference to viral infections.

Epstein-Barr virus and multiple sclerosis

It has been suggested that the Epstein-Barr virus (EBV) plays a role in the etiology of multiple sclerosis (MS), but individual epidemiologic studies have been inconclusive, in part because of the high prevalence of previous infection among individuals without MS. We conducted a systematic review of case-control studies comparing EBV serology in MS patients and controls. Eight published investigations were identified, including a total of 1,005 cases and 1,060 controls. The summary odds ratio of MS comparing EBV seropositive individuals with EBV seronegative individuals was 13.5 (95% CI = 6.3-31.4). The strength and consistency of this association and the high sensitivity and specificity of EBV serology suggest that these results are not readily explained by an aspecific immune activation among MS patients. These findings support a role of EBV in the etiology of MS.

Rheumatoid arthritis sera react with a phage-displayed peptide selected by a monoclonal antibody to type II collagen that has homology to EBNA-1

Antibodies to type II collagen, and to Epstein Barr virus nuclear antigen-1 (EBNA-1) have been associated with rheumatoid arthritis (RA). In studies involving probing of phage-displayed random peptide libraries with an antibody to type II collagen, CII-C1, we observed that among 17 phagotopes selected 5 expressed peptides with homology with the sequence of EBNA-1. The residues in common were RLPFG. Hence we tested sera from 50 patients with RA, of whom 26 had antibodies to native type II collagen, and 43 healthy controls, for reactivity by ELISA with a phagotope selected 4 times, which expressed the peptide RRLPFGSQM. Eight RA sera (16%) but no normal sera reacted with the phagotope (p = 0.025). This reactivity could not be correlated with reactivity of RA sera with EBNA-1 by semi-quantitative western blot, with which reactivity occurred in 78% of RA patients and 81% of controls. Evidence for molecular mimicry was not found insofar as the phagotope did not inhibit reactivity of RA sera with EBNA-1 and CII-C1 was not reactive with EBNA-1. We conclude that the reactivity of the RA sera with the phagotope is most likely due to the phagotope being a mimic of an epitope of type II collagen for a proportion of RA sera.

Epstein-Barr virus strain characterization

The Epstein-Barr virus (EBV), a ubiquitous human herpesvirus originally described in cultured lymphoblasts from African Burkitt's lymphoma, is the causative agent of infectious mononucleosis, but appears to be involved in the pathogenesis of a variety of diseases. EBV has the ability to establish lifelong persistent infection, where only a restricted pattern of the viral proteins is expressed. Periodic reactivation of EBV occurs, where mature EBV particles are produced. Strain variation is potentially important in the biology and epidemiology of EBV, and in attempts to relate EBV to associated diseases. Analysis of the EBV genomes isolated from patients with EBV-associated diseases and from various parts of the world has so far failed to identify conclusive disease-specific viral subtypes. This review focuses on the different strategies which have been used for strain characterization or subtyping of EBV.

An increased prevalence of Epstein-Barr virus infection in young patients suggests a possible etiology for systemic lupus erythematosus

An unknown environmental agent has been suspected to induce systemic lupus erythematosus (lupus) in man. Prompted by our recent immunochemical findings, we sought evidence for an association between Epstein-Barr virus infection and lupus. Because the vast majority of adults have been infected with Epstein-Barr virus, we chose to study children and young adults. Virtually all (116 of 117, or 99%) of these young patients had seroconverted against Epstein-Barr virus, as compared with only 70% (107 of 153) of their controls (odds ratio 49.9, 95% confidence interval 9.3-1025, P < 0. 00000000001). The difference in the rate of Epstein-Barr virus seroconversion could not be explained by serum IgG level or by cross-reacting anti-Sm/nRNP autoantibodies. No similar difference was found in the seroconversion rates against four other herpes viruses. An assay for Epstein-Barr viral DNA in peripheral blood lymphocytes established Epstein-Barr virus infection in the peripheral blood of all 32 of the lupus patients tested, while only 23 of the 32 matched controls were infected (odds ratio > 10, 95% confidence interval 2.53-infinity, P < 0.002). When considered with other evidence supporting a relationship between Epstein-Barr virus and lupus, these data are consistent with, but do not in themselves establish, Epstein-Barr virus infection as an etiologic factor in lupus.

The p542 gene encodes an autoantigen that cross-reacts with EBNA-1 of the Epstein Barr virus and which may be a heterogeneous nuclear ribonucleoprotein

In infectious mononucleosis (IM), anti-EBNA-1 antibodies are produced which cross-react with multiple normal human proteins. The cross-reactions can be inhibited with synthetic peptides representing the glycine/alanine repeat in EBNA-1, which implies that the cross-reactivity is due to anti-gly/ala antibodies that cross-react with host proteins containing configurations like those in the EBNA-1 repeat. Here we report the isolation of five gene fragments from a Raji B lymphocyte cDNA library encoding peptides reactive with autoantibodies in an IM serum. One of these, p542, encodes a glycine rich 28-mer which constitutes its cross-reactive epitope, as shown elsewhere. By Northern blots, p542 was identifiable in three B lymphocyte lines, a T cell line, and an epithelial cell line. In a search of the GenBank for proteins with sequence similarity to p542, we found a high degree of identity with the mid- and 3' terminal regions of the recently published mouse gene, Raly, which encodes a protein with the structure of a heterogeneous nuclear ribonuclear protein (hnRNP). We confirmed by anchored RT-PCR our presumption that the 5' sequences of p542 also have a high degree of identity with Raly, including presence of RNA binding motifs characteristic of hnRNPs. There was also sequence homology with human hnRNP C2. From these observations and our previous studies, we conclude that the autoantigen for one of the cross-reactive autoantibodies generated during immune responses to the Epstein Barr virus, anti-p542, is probably an hnRNP.