Several genetic and environmental factors have been linked to Systemic Lupus Erythematosus (SLE). One environmental trigger that has a strong association with SLE is the Epstein Barr Virus (EBV). Our laboratory previously demonstrated that BALB/c mice expressing the complete EBNA-1 protein can develop antibodies to double stranded DNA (dsDNA). The present study was undertaken to understand why anti-dsDNA antibodies arise during the immune response to EBNA-1.
In this study, we demonstrated that mouse antibodies elicited in response to EBNA-1 cross-react with dsDNA. First, we showed that adsorption of sera reactive with EBNA-1 and dsDNA, on dsDNA cellulose columns, diminished reactivity with EBNA-1. Next, we generated mononclonal antibodies (MAbs) to EBNA-1 and showed, by several methods, that they also reacted with dsDNA. Examination of two cross-reactive MAbs—3D4, generated in this laboratory, and 0211, a commercial MAb—revealed that 3D4 recognizes the carboxyl region of EBNA-1, while 0211 recognizes both the amino and carboxyl regions. In addition, 0211 binds moderately well to the ribonucleoprotein, Sm, which has been reported by others to elicit a cross-reactive response with EBNA-1, while 3D4 binds only weakly to Sm. This suggests that the epitope in the carboxyl region may be more important for cross-reactivity with dsDNA while the epitope in the amino region may be more important for cross-reactivity with Sm.
In conclusion, our results demonstrate that antibodies to the EBNA-1 protein cross-react with dsDNA. This study is significant because it demonstrates a direct link between the viral antigen and the development of anti-dsDNA antibodies, which are the hallmark of SLE. Furthermore, it illustrates the crucial need to identify the epitopes in EBNA-1 responsible for this cross-reactivity so that therapeutic strategies can be designed to mask these regions from the immune system following EBV exposure.
Epstein-Barr virus has been implicated in the etiology of systemic lupus erythematosus (SLE) through serologic and immunologic studies. A potential mechanism for this influence is through molecular mimicry. The EBV nuclear antigen EBNA-1 contains a region, PPPGRRP, with considerable homology to the initial sequence targeted by antibodies in Sm B’ autoimmunity, PPPGMRPP. This study examined whether immunization of rabbits and mice with peptides containing the PPPGRRP sequence from EBNA-1 constructed on a poly-lysine backbone was able to drive the development of autoantibodies against the Smith antigen (Sm) and the related antigenic complex, the U1 nuclear ribonucleoproteins (nRNP). PPPGRRP immunization, and immunization with an EBNA-1 fragment containing PPPGRRP, led to autoantibodies in both rabbits and mice at high frequency (83% of rabbits and 43% of mice). Five out of six immunized rabbits developed either leucopenia or lymphopenia or both. The fine specificity of antibody binding against the lupus-associated autoantigens Sm B’, nRNP A, and nRNP C after immunization with the EBNA-1-derived peptides was very similar to the early antibody binding patterns against these proteins in human SLE. This similarity, as well as the prevalence of autoimmunity after immunization with these peptides, identifies PPPGRRP as a strong candidate for molecular mimicry in SLE etiology.
autoantibodies; molecular mimicry; systemic lupus erythematosus; Epstein-Barr virus
Serologic association, cross-reactivity of select EBV-specific antibodies with SLE autoantigens, SLE-like autoimmunity after immunization with EBV peptides, increased EB viral load in SLE patients, and SLE-specific alterations in EBV humoral and cellular immunity implicate Epstein–Barr virus (EBV) in the development of systemic lupus erythematosus (SLE). To investigate SLE-specific differences in EBV gene expression, levels of eight EBV genes were compared between SLE patients and controls by using both ex vivo-infected and un-manipulated peripheral blood mononuclear cells (PBMCs). Expression levels of mRNA were significantly greater by Wilcoxen signed rank test in the ex vivo-infected SLE patient-derived cells for 4 of 8 EBV genes, including BLLF1, 3.2-fold (p<0.004); LMP-2, 1.7-fold (p<0.008); EBNA-1, 1.7-fold (p<0.01); and BcRF1, a proposed DNA binding protein, 1.7-fold (p<0.02). The frequency of LMP-1 gene expression was significantly greater by Chi square analysis in the peripheral blood from SLE patients than controls (44% of patients, 10% of controls p<0.05). PBMCs from SLE patients had greater expression of latent genes as well as increased expression of both latent and lytic genes after infection, suggesting that EBV may participate in SLE etiology through several mechanisms. Such altered infection patterns may contribute to the increased levels of EBV and the molecular mimicry seen in sera from SLE patients.
Systemic lupus erythematosus; Epstein–Barr virus; Gene expression; Latency
Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus. Toll-like receptor 7 (TLR7) is involved in host innate immunity against pathogens, and its aberrant activation is linked to the development of systemic lupus erythematosus (SLE, also called “lupus”). Type I interferons (IFN) are apparently driving forces for lupus pathogenesis. Previously, we found that EBV latent membrane protein 1 (LMP1) primes cells for IFN production. In this report, the relationship among EBV LMP1, TLRs, and IFN production are examined. We find that TLR7 activation increases the expression of EBV LMP1, and IFN regulatory factor 7 (IRF7) is involved in the stimulation process. TLR7 activation did not induce IFNs from EBV-infected cells, but potentiates those cells for IFN production by TLR3 or TLR9 activation. In addition, we find that LMP1 and IFNs are co-expressed in the same cells in some lupus patients. Therefore, the aberrant activation of TLR7 might induce LMP1 expression and LMP1-expression cells may be producing IFNs in lupus patients. These results suggest EBV might be an exacerbating factor in some lupus patients via promoting IFN production.
The processes that govern the generation of pathogenic anti-DNA autoantibodies in human systemic lupus erythematosus (SLE) are largely unknown. Autoantibodies may arise as a consequence of polyclonal B cell activation and/or antigen-driven B cell activation and selection. The role of these processes in humoral autoimmunity may be studied by molecular genetic analysis of immunoglobulin (Ig) variable (V) regions of antibodies that are characteristic of SLE. We have analyzed the gene elements that encode a high affinity, IgG anti-double-stranded DNA autoantibody secreted by a monoclonal Epstein-Barr virus (EBV)- transformed cell line derived from a patient with active SLE. In addition, we have identified, cloned, and sequenced the germline counterparts of the VH and VL genes expressed in this autoantibody. The comparison of both sets of gene elements shows that the autoantibody VH and VL regions harbor numerous somatic mutations characteristic of an antigen-driven immune response. The light chain expressed in this autoantibody is a somatically mutated variant of the kv325 germline gene that is frequently associated with paraproteins having autoantibody activity and with Ig molecules produced by malignant B cells that express the CD5 antigen. Furthermore, the utilized DH segment has been repeatedly found in multireactive, low affinity IgM anti-DNA autoantibodies from SLE patients and healthy individuals. These results suggest that pathogenic IgG anti-DNA autoantibodies in human SLE may arise through antigen-driven selection of somatic mutations in the gene elements that frequently encode multireactive IgM autoantibodies.
Study was undertaken to analyze the frequency of anti-viral citrullinated peptide (anti-VCP) antibodies in sera from patients with early rheumatoid arthritis (ERA).
Materials and Methods:
Viral citrullinated peptide (VCP) and Epstein-Barr nuclear antigen (EBNA-1) peptide were commercially prepared and antibodies to these were determined in 25 patients of ERA, 40 disease control patients constituting 25 rheumatoid arthritis (RA), 7 systemic lupus erythematosus (SLE), 2 scleroderma, 1 spondyloarthritis (SpA), 1 juvenile rheumatoid arthritis (JRA), 1 osteoarthritis (OA), 1 psoriatic arthritis (PsA), 1 undifferentiated arthritis (UA), and 1 gout and 25 healthy controls (HCs) were taken for comparison. In-house ELISA was established for both the antibodies while cyclic citrullinated peptide (CCP) antibody was detected by commercial ELISA kit.
Significant increase in VCP antibody by ERA and disease controls than healthy normal was observed. VCP IgM antibody was significantly increased in RA patients than HC. The presence of VCP antibody signifies a good marker for ERA. We observed significant difference in the VCP IgG and IgM antibody when compared to EBNA-1. In-house ELISA established for EBNA-1 and VCP antibodies showed low sensitivity but 96% specificity.
We observed that sera from early RA patients reacted to the deiminated protein encoded by Epstain Barr Virus (EBV). Thus a possible role of virus in inducing an anti-citrullinated peptide antibody (ACPA) response reveals viral etiology in this disease.
Anti-viral citrullinated peptides/antibodies; ERA; EBNA-1; ELISA
A 62,000-dalton (62K) cell protein reacts with antisera to the 72K polypeptide of the Epstein-Barr virus nuclear antigen (EBNA) in immunoblots. This protein was initially detected in EBNA-negative as well as EBNA-positive cell lines with anti-EBNA-positive human sera. A monoclonal antibody raised against the 72K EBNA and an antiserum from a rabbit immunized with the glycine-alanine domain of EBNA also reacted with the cellular protein. The cellular protein was partially purified from Epstein-Barr virus genome-positive and -negative cell lines. Absorption experiments identified a shared antigenic determinant between the 72K EBNA and 62K cellular protein. A comparison of the 62K protein and EBNA by protease digestion did not reveal similar peptides.
Epstein-Barr virus (EBV) infection has been linked to systemic lupus erythematosus (SLE) as demonstrated by the presence of increased seroprevalence and elevated viral loads, but the mechanism of this linkage has not been elucidated. Increased IFN-α levels and signatures, associated with innate immune responses, have been found in patients with SLE. Plasmacytoid dendritic cells (pDC) are innate immune cells that mediate viral immunity by producing large quantities of interferon alpha (IFN-α), but the role they play during infection with EBV remains unclear. To address this issue, we investigated the ability of EBV to promote IFN-α production by pDC in healthy subjects.
Human pDC were sorted and cultured in the presence of EBV, EBV small RNA (EBER), and EBV double-stranded DNA (dsDNA). IFN-α production by pDC was measured by enzyme-linked immunosorbent assay (ELISA), with activation of these cells measured by flow cytometry.
We demonstrate that EBV DNA and RNA promote IFN-α production by human pDC through engagement of Toll-like receptor (TLR) 9 and TLR7, respectively, with initial viral recognition by pDC mediated by binding to major histocompatibility (MHC) class II molecules.
These data demonstrate that MHC class II-specific engagement by virus and subsequent viral nucleic acid recognition mediates IFN-α production by pDC. Our results suggest that elevated levels of IFN-α found in lupus patients may be a result of aberrantly controlled chronic viral infection.
Epstein Barr virus (EBV) causes lymphomas in immune competent and, at increased frequencies, in immune compromised patients. In the presence of an intact immune system, EBV associated lymphomas express in most cases only three or fewer EBV antigens at the protein level, always including the nuclear antigen 1 of EBV (EBNA1). EBNA1 is a prominent target for EBV specific CD4+ T cell and humoral immune responses in healthy EBV carriers. Here we demonstrate that patients with EBV associated lymphomas, primarily Hodgkin's lymphoma, lack detectable EBNA1 specific CD4+ T cell responses and have slightly altered EBNA1 specific antibody titers at diagnosis. In contrast, the majority of EBV negative lymphoma patients had detectable IFNγ expression and proliferation by CD4+ T cells in response to EBNA1, and carry EBNA1 specific immunoglobulins at levels similar to healthy virus carriers. Other EBV antigens, which were not present in the tumors, were recognized in less EBV positive, than negative lymphoma patients, but detectable responses reached similar CD8+ T cell frequencies in both cohorts. Patients with EBV positive and negative lymphomas did not differ in T cell responses in influenza specific CD4+ T cell proliferation and in antibody titers against tetanus toxoid. These data suggest a selective loss of EBNA1 specific immune control in EBV associated lymphoma patients, which should be targeted for immunotherapy of these malignancies.
EBNA1; CD4+ T cells; Hodgkin's lymphoma
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.
Epstein–Barr virus; Epstein–Barr virus type; systemic lupus erythematosus; virus burden
For decades, scientists have tried to understand the environmental factors involved in the development of systemic lupus erythematosus (SLE), in which viral infections was included. Previous studies have identified Epstein-Barr virus (EBV) to incite SLE. Human herpesvirus 8 (HHV-8), another member of the gammaherpesvirus family, shares a lot in common with EBV. The characteristics of HHV-8 make it a well-suited candidate to trigger SLE.
In the present study, serum samples from patients (n = 108) with diagnosed SLE and matched controls (n = 122) were collected, and the prevalence of HHV-8 was compared by a virus-specific nested PCR and a whole virus enzyme-linked immunoassay (EIA). There was significant difference in the prevalence of HHV-8 DNA between SLE patients and healthy controls (11 of 107 vs 1 of 122, p = 0.001); significant difference was also found in the detection of HHV-8 antibodies (19 of 107 vs 2 of 122, p < 0.001).
We also detected the antibodies to Epstein-Barr virus viral capsid antigen (EBV-VCA) and Epstein-Barr nuclear antigen-1 (EBNA-1). Both patients and controls showed high seroprevalence with no significant difference (106 of 107 vs 119 of 122, p = 0.625).
Our finding indicated that there might be an association between HHV-8 and the development of SLE.
Systemic Lupus Erythematosus (SLE) pathology has long been associated with an increased Epstein-Barr Virus (EBV) seropositivity, viremia and cross-reactive serum antibodies specific for both virus and self. It has therefore been postulated that EBV triggers SLE immunopathology, although the mechanism remains elusive. Here, we investigate whether frequent peaks of EBV viral load in SLE patients are a consequence of dysfunctional anti-EBV CD8+ T cell responses. Both inactive and active SLE patients (n = 76 and 42, respectively), have significantly elevated EBV viral loads (P = 0.003 and 0.002, respectively) compared to age- and sex-matched healthy controls (n = 29). Interestingly, less EBV-specific CD8+ T cells are able to secrete multiple cytokines (IFN-γ, TNF-α, IL-2 and MIP-1β) in inactive and active SLE patients compared to controls (P = 0.0003 and 0.0084, respectively). Moreover, EBV-specific CD8+ T cells are also less cytotoxic in SLE patients than in controls (CD107a expression: P = 0.0009, Granzyme B release: P = 0.0001). Importantly, cytomegalovirus (CMV)-specific responses were not found significantly altered in SLE patients. Furthermore, we demonstrate that EBV-specific CD8+ T cell impairment is a consequence of their Programmed Death 1 (PD-1) receptor up-regulation, as blocking this pathway reverses the dysfunctional phenotype. Finally, prospective monitoring of lupus patients revealed that disease flares precede EBV reactivation. In conclusion, EBV-specific CD8+ T cell responses in SLE patients are functionally impaired, but EBV reactivation appears to be an aggravating consequence rather than a cause of SLE immunopathology. We therefore propose that autoimmune B cell activation during flares drives frequent EBV reactivation, which contributes in a vicious circle to the perpetuation of immune activation in SLE patients.
Systemic Lupus Erythematosus (SLE) has been associated with Epstein-Barr Virus (EBV) infection for decades, however the mechanistic links have remained elusive. Most human adults are infected by EBV and carry the virus for life without clinical symptoms. However, for unknown reasons EBV induces infectious mononucleosis in some individuals, during which cross-reactive antibodies specific for both virus and self have been detected. Interestingly, such cross-reactive antibodies are also frequently found in SLE patients. Since, EBV seropositivity and viremia are more frequent in SLE patients than in healthy individuals, it has been postulated that EBV trigger autoimmunity. Here we show that SLE patients are indeed less capable of controlling EBV viremia, since their EBV-specific CD8+ T cells have diminished capacity to secrete effector molecules (e.g. cytokines and chemokines) and to kill EBV-infected targets as a consequence of their Programmed Death 1 (PD-1) receptor up-regulation. Longitudinal studies further reveal that disease flares precede EBV viremia. Thus, contrary to expectations, EBV reactivation appears to be an aggravating consequence, rather than a cause, of SLE immunopathology. Our results pave the way for immunological interventions that restore the host-EBV balance, which may result in decreased levels of aggravating cross-reactive antibodies and ultimately be beneficial to SLE patients.
A new class of Epstein-Barr virus nuclear antigen (EBNA) was identified by the complement fixation assay. This new species of EBNA is more tightly bound to chromatin and was termed class II EBNA, as opposed to the more weakly associated species, class I EBNA. Preparations of this new antigen(s) specifically reduced absorption with the titer of anti-EBNA antibodies as determined by the anticomplement immunofluorescence assay. Therefore, the complement fixation antigens (class II EBNA) appear to be related to the classical EBNA (class I EBNA). The class I EBNA was found to focus at the same pH (4.6) as the soluble antigen found in the cytosol. The class II EBNA differed from the class I EBNA with regard to its overall charge, molecular size, antigenicity, and affinity for chromatin. The class II EBNA appeared to be a basic protein, based on its apparent pI of 9.2 and its binding to cation-exchange resins. It differed from histones with regard to its molecular size (molecular weight between 60,000 and 70,000) and its elution from hydroxylapatite chromatography. Steps were taken to prevent proteolysis and artifacts in the immunological assays and in the overall charge estimation of the new antigen by nonspecific basic histone protein-acidic protein interactions. Both class I and class II EBNA were identified by radioimmunoelectrophoresis on two-dimensional polyacrylamide gels with pI values of 5.0 and 8.5, respectively, and a molecular weight range of 60,000 to 70,000 for both. A lower-molecular-weight antigen identified by molecular sieve chromatography appeared to be due to interference by histones in the immunoassays since it was not observed by the two-dimensional gel electrophoresis. Further characterization of this class II EBNA is in progress.
Systemic lupus erythematosus is characterized by production of autoantibodies to RNA or DNA–protein complexes such as small nuclear ribonucleoproteins (snRNPs). A role of Epstein–Barr virus in the pathogenesis has been suggested. Similar to Epstein–Barr virus, cytomegalovirus (CMV) infects the majority of individuals at a young age and establishes latency with a potential for reactivation. Homology of CMV glycoprotein B (UL55) with the U1snRNP-70 kDa protein (U1–70 k) has been described; however, the role of CMV infection in production of anti-snRNPs is controversial. We investigated the association of CMV serology and autoantibodies in systemic lupus erythematosus.
Sixty-one Mexican patients with systemic lupus erythematosus were tested for CMV and Epstein–Barr virus serology (viral capsid antigen, IgG, IgM) and autoantibodies by immunoprecipitation and ELISA (IgG and IgM class, U1RNP/Sm, U1–70 k, P peptide, rheumatoid factor, dsDNA, β2-glycoprotein I).
IgG anti-CMV and IgM anti-CMV were positive in 95% (58/61) and 33% (20/61), respectively, and two cases were negative for both. Clinical manifestation and autoantibodies in the IgM anti-CMV(+) group (n = 20) versus the IgM anti-CMV(-)IgG (+) (n = 39) group were compared. Most (19/20) of the IgM anti-CMV(+) cases were IgG anti-CMV(+), consistent with reactivation or reinfection. IgM anti-CMV was unrelated to rheumatoid factor or IgM class autoantibodies and none was positive for IgM anti-Epstein–Barr virus–viral capsid antigen, indicating that this is not simply due to false positive results caused by rheumatoid factor or nonspecific binding by certain IgM. The IgM anti-CMV(+) group has significantly lower levels of IgG anti-U1RNP/Sm and IgG anti-U1–70 k (P = 0.0004 and P = 0.0046, respectively). This finding was also confirmed by immunoprecipitation. Among the IgM anti-CMV(-) subset, anti-Su was associated with anti-U1RNP and anti-Ro (P < 0.05). High levels of IgG anti-CMV were associated with production of lupus-related autoantibodies to RNA or DNA–protein complex (P = 0.0077).
Our findings suggest a potential role of CMV in regulation of autoantibodies to snRNPs and may provide a unique insight to understand the pathogenesis.
Kikuchi-Fujimoto disease (KFD) or histiocytic necrotizing lymphadenitis was first described in Japan in 1972. It is described as a benign syndrome most commonly involving cervical lymphadenopathy, fever, and night sweats. The etiology of KFD is unknown but it is thought to be triggered by an autoimmune or viral process with an exaggerated T-cell-mediated immune response. KFD can mimic other serious conditions such as lymphoma, systemic lupus erythematosus (SLE), herpes simplex, and Epstein Barr virus. Diagnosis is confirmed histopathologically. Kikuchi's disease is typically reported to have a self-limiting course, resolving within several months and with a low recurrence rate between 3% and 4%. There is no specific treatment for KFD but any treatment is generally directed towards symptomatic relief with antipyretics and anti-inflammatory medications. In severe cases corticosteroids have been used. Here we describe a case of a previously healthy 26-year-old female that presented with fever and cervical lymphadenopathy. Malignancy and infections were ruled, and she was diagnosed with KFD histopathologically by lymph node biopsy. Her case is a severe case of KFD that despite treatment with multiple courses of corticosteroids and an immune modulating agent, relapsed.
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.
Systemic lupus erythematosus (SLE) is a severe multi-system autoimmune disease which results from both genetic predisposition and environmental factors. Many lines of investigation support interferon alpha (IFN-α) as a causal agent in human lupus, and high levels of serum IFN-α are a heritable risk factor for SLE. Interferon regulatory factors (IRFs) are a family of transcription factors involved in host defense, which can induce transcription of IFN-α and other immune response genes following activation. In SLE, circulating immune complexes which contain nucleic acid are prevalent. These complexes are recognized by endosomal Toll-like receptors, resulting in activation of downstream IRF proteins. Genetic variants in the IRF5 and IRF7 genes have been associated with SLE susceptibility, and these same variants are associated with increased serum IFN-α in SLE patients. The increase in serum IFN-α related to IRF5 and 7 genotypes is observed only in patients with particular antibody specificities. This suggests that chronic stimulation of the endosomal Toll-like receptors by autoantibody immune complexes is required for IRF SLE-risk variants to cause elevation of circulating IFN-α and subsequent risk of SLE. Recently, genetic variation in the IRF8 gene has been associated with SLE and multiple sclerosis, and studies support an impact of IRF8 genotype on the IFN-α pathway. In summary, the SLE-associated polymorphisms in the IRF family of proteins appear to be gain-of-function variants, and understanding the impact of these variants upon the IFN-α pathway in vivo may guide therapeutic strategies directed at the Toll-like receptor/IRF/IFN-α pathway in SLE.
Interferon Alpha; Genetics; Systemic Lupus Erythematosus; Interferon Regulatory Factor; Autoantibodies; Autoimmunity
The aim of this study was to evaluate an extensive panel of cytokines involved in immune regulation during pregnancy in patients with systemic lupus erythematosus (SLE) and in healthy women.
A total of 47 consecutive successful pregnancies in 46 SLE patients and 56 pregnancies in 56 matched healthy subjects, as controls, were prospectively studied. Serum interleukin (IL)-1-α, IL-1-β, IL-2, IL-6, IL-8, IL-10, IL-12p70, interferon (INF)-γ and tumor necrosis factor (TNF)-α were detected in sera obtained at the first and third trimester of pregnancy by a highly sensitive, multiplexed sandwich ELISA.
Medians (pg/ml) of serum levels of most helper T (Th)1-type cytokines were significantly lower in the third trimester compared with those observed in the first trimester of pregnancy in healthy women: INF-γ 2.0 vs 3.4, TNF-α 10.2 vs 11.5, IL-1-α 0.9 vs 1.1, IL-1-β 0.6 vs 1.0, IL-2 3.0 vs 3.5, and IL-12p70 4.9 vs 5.6 (P-values < 0.02 for all). By contrast, only the IL-1-α serum levels were lower in the third trimester compared with the first trimester in SLE patients (P = 0.006). IFN-γ/IL-6 and IFN-γ/IL-10 ratios were higher in controls than in SLE (P = 0.002, and P = 0.001, respectively); moreover, they were significantly reduced in the third compared to the first trimester of pregnancy in healthy women, but not in SLE.
In SLE patients, Th1/Th2 cytokine serum level ratio does not decrease during pregnancy progression as much as in healthy pregnant women. This could account for the observation of a low frequency of disease flares in the third trimester of gestation.
The replication and stable maintenance of latent Epstein-Barr virus (EBV) DNA episomes in human cells requires only one viral protein, Epstein-Barr nuclear antigen 1 (EBNA1). To gain insight into the mechanisms by which EBNA1 functions, we used a yeast two-hybrid screen to detect human proteins that interact with EBNA1. We describe here the isolation of a protein, EBP2 (EBNA1 binding protein 2), that specifically interacts with EBNA1. EBP2 was also shown to bind to DNA-bound EBNA1 in a one-hybrid system, and the EBP2-EBNA1 interaction was confirmed by coimmunoprecipitation from insect cells expressing these two proteins. EBP2 is a 35-kDa protein that is conserved in a variety of organisms and is predicted to form coiled-coil interactions. We have mapped the region of EBNA1 that binds EBP2 and generated internal deletion mutants of EBNA1 that are deficient in EBP2 interactions. Functional analyses of these EBNA1 mutants show that the ability to bind EBP2 correlates with the ability of EBNA1 to support the long-term maintenance in human cells of a plasmid containing the EBV origin, oriP. An EBNA1 mutant lacking amino acids 325 to 376 was defective for EBP2 binding and long-term oriP plasmid maintenance but supported the transient replication of oriP plasmids at wild-type levels. Thus, our results suggest that the EBNA1-EBP2 interaction is important for the stable segregation of EBV episomes during cell division but not for the replication of the episomes.
Epstein-Barr virus (EBV) efficiently immortalizes human B cells and is associated with several human malignancies. The EBV transcriptional activating protein EBNA2 and the EBNA2 coactivator EBNA-leader protein (EBNA-LP) are important for B cell immortalization. Recent observations from our laboratory indicate that EBNA-LP coactivation function is mediated through interactions with the interferon-inducible gene (ISG) Sp100, resulting in displacement from its normal location in promyelocytic leukemia nuclear bodies (PML NBs) into the nucleoplasm. The EBNA-LP- and interferon-mediated mechanisms that regulate Sp100 subnuclear localization and transcriptional function remain undefined. To clarify these issues, we generated a panel of Sp100 mutant proteins to ascertain whether EBNA-LP induces Sp100 displacement from PML NBs by interfering with Sp100 dimerization or through other domains. In addition, we tested EBNA-LP function in interferon-treated cells. Our results indicate that Sp100 dimerization, PML NB localization, and EBNA-LP interaction domains overlap significantly. We also show that IFN-β does not inhibit EBNA-LP coactivation function. The results suggest that EBNA-LP might play a role in EBV-evasion of IFN-mediated antiviral responses.
Systemic lupus erythematosus (SLE) is a multiphenotypic autoimmune disease. The hallmark of SLE is the production of anti-double-stranded DNA autoantibodies and the deposition of immune complexes in target tissues such as the kidney, skin, and brain. Additional phenotypic traits are the presence of arthritis, anemia, central nervous system involvement, and a variety of autoantibodies. Females of childbearing age are particularly at risk. Recent genetic analysis of murine SLE shows that susceptibility is under complex polygenic control. It is also apparent that environmental factors contribute to the induction and exacerbation of SLE. We describe here the genotypic and phenotypic characterization of a group of recombinant inbred strains of SLE-prone mice that were derived from NZB and NZW progenitors, the parental strains of the classic female F1 hybrid lupus model. Recombination and reassortment of these ancestral genomes resulted in the NZM (New Zealand mixed) strains with strain-specific patterns of renal disease penetrance and other autoimmune traits such as Coombs positive anemia and neurologic deficits. Multiple susceptibility loci of the ancestral strains demonstrate that SLE is inherited as a threshold trait. Because some of these loci co-localize with the susceptibility loci of the insulin-dependent diabetes of nonobese diabetic strain, it is apparent that there are disease-specific as well as autoimmunity-promoting genes. It is proposed that the NZM strains, particularly those with reduced disease penetrance or partial genotypes, provide an improved genetic model for assessment of the effects of environmental agents on SLE and autoimmunity.
Patients with rheumatoid arthritis (RA) are known to have in vitro regulatory T cell abnormalities relating to Epstein-Barr virus (EBV). In this report, we asked whether patients with RA have more circulating EBV-infected B cells than normals. To address this question, we determined the frequency of spontaneously transforming B cells in the peripheral blood of 18 normals, 15 patients with RA, and 8 patients with systemic lupus erythematosus (SLE). The mean frequency of spontaneously transforming B cells in RA patients was 10.1/10(6) B cells, which was significantly greater than that of the normal controls, 2.8/10(6) B cells (P less than 0.005). The group of patients with SLE did not differ from the normals (P greater than 0.4). In further studies undertaken to investigate as to whether RA B cells are more easily transformed by EBV than normal B cells, we determined that the frequencies of transforming B cells in the presence of exogenous EBV were similar in RA patients and normals. Lymphocytes obtained from patients with RA demonstrate a profound T cell defect in their EBV-specific suppression, as measured in vitro; there was no direct correlation, however, between this in vitro T cell abnormality and the number of circulating EBV-infected B cells. Thus, patients with RA, as a group, have abnormally elevated numbers of circulating EBV-infected B cells, and this abnormality most likely derives from a complex dysregulation of the defense mechanisms for infection with EBV.
Transfection of a plasmid encoding the Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) gene confers resistance to the antiproliferative effect of alpha interferon (IFN-alpha) in EBV-negative U968 cells (P. Aman and A. von Gabain, EMBO J. 9:147-152, 1990). We studied the expression of IFN-stimulated genes (ISGs) in two pairs of Burkitt's lymphoma cell lines, differing in the expression of the putative immortalizing gene of EBV, EBNA2. In EBNA2-expressing cells, the induction of four ISGs by IFN-alpha was strongly reduced or, in some cases, abolished. Chloramphenicol acetyltransferase reporter gene constructs containing different IFN-stimulated response elements were transfected into EBNA2-negative and EBNA2-positive cells. Induction of chloramphenicol acetyltransferase activity by IFN was impaired in EBNA2-positive cells. Also, a reporter gene construct driven by an IFN-gamma-sensitive promoter element was affected. However, as revealed by gel shift assays, EBNA2-positive and EBNA2-negative cells exhibited a nearly identical pattern of IFN-stimulated response element-binding proteins. Most important, activation of the factor ISGF-3, which previously has been shown to be required and sufficient for transcriptional activation of IFN-induced genes, was not inhibited in IFN-resistant cells expressing EBNA2. The mechanism of the EBNA2-related IFN resistance seems to be distinct both from the resistance mediated by hepatitis virus and adenovirus gene products and from the IFN resistance in Daudi cell variants. In these three cases, the transcriptional block of IFN-induced genes is due to inhibition of ISGF-3 activation and binding. Our data suggest that the EBNA2-related IFN resistance in Burkitt's lymphoma cells acts downstream of the activation of ISGF-3.
Viral nuclear oncoproteins EBNA3A and EBNA3C are essential for the efficient immortalization of B cells by Epstein–Barr virus (EBV) in vitro and it is assumed that they play an essential role in viral persistence in the human host. In order to identify cellular genes regulated by EBNA3A expression, cDNA encoding EBNA3A was incorporated into a recombinant adenoviral vector. Microarray analysis of human diploid fibroblasts infected with either adenovirus EBNA3A or an empty control adenovirus consistently showed an EBNA3A-specific induction of mRNA corresponding to the chaperones Hsp70 and Hsp70B/B′ and co-chaperones Bag3 and DNAJA1/Hsp40. Analysis of infected fibroblasts by real-time quantitative RT-PCR and Western blotting confirmed that EBNA3A, but not EBNA3C, induced expression of Hsp70, Hsp70B/B′, Bag3 and DNAJA1/Hsp40. This was also confirmed in a stable, inducible expression system. EBNA3A activated transcription from the Hsp70B promoter, but not multimerized heat-shock elements in transient transfection assays, consistent with specific chaperone and co-chaperone upregulation. Co-immunoprecipitation experiments suggest that EBNA3A can form a complex with the chaperone/co-chaperone proteins in both adenovirus-infected cells and EBV-immortalized lymphoblastoid cell lines. Consistent with this, induction of EBNA3A resulted in redistribution of Hsp70 from the cytoplasm to the nucleus. EBNA3A therefore specifically induces (and then interacts with) all of the factors necessary for an active Hsp70 chaperone complex.
HA95, a nuclear protein homologous to AKAP95, has been identified in immune precipitates of the Epstein-Barr virus (EBV) coactivating nuclear protein EBNA-LP from EBV-transformed lymphoblastoid cells (LCLs). We now find that HA95 and EBNA-LP are highly associated in LCLs and in B-lymphoma cells where EBNA-LP is expressed by gene transfer. Binding was also evident in yeast two-hybrid assays. HA95 binds to the EBNA-LP repeat domain that is the principal coactivator of transcription. EBNA-LP localizes with HA95 and causes HA95 to partially relocalize with EBNA-LP in promyelocytic leukemia nuclear bodies. Protein kinase A catalytic subunit α (PKAcsα) is significantly associated with HA95 in the presence or absence of EBNA-LP. Although EBNA-LP is not a PKA substrate, HA95 or PKAcsα expression in B lymphoblasts specifically down-regulates the strong coactivating effects of EBNA-LP. The inhibitory effects of PKAcsα are reversed by coexpression of protein kinase inhibitor. PKAcsα also inhibits EBNA-LP coactivation with the EBNA-2 acidic domain fused to the Gal4 DNA binding domain. Furthermore, EBNA-LP- and EBNA-2-induced expression of the EBV oncogene, LMP1, is down-regulated by PKAcsα or HA95 expression in EBV-infected lymphoblasts. These experiments indicate that HA95 and EBNA-LP localize PKAcsα at nuclear sites where it can affect transcription from specific promoters. The role of HA95 as a scaffold for transcriptional regulation is discussed.