Epstein-Barr virus and molecular mimicry in systemic lupus erythematosus

Systemic lupus erythematosus (SLE or lupus) is a complex disease with a multifactoral etiology, with genetic, hormonal, and environmental influences. Molecular mimicry as a result of viral infection may contribute to the development of lupus. The pattern of autoantibody development in lupus is consistent with initiation through molecular mimicry, as the initial autoantigenic epitopes that have been observed are limited and cross-reactive with viral proteins. Autoantibody specificity may then later diversify to other autoantigens through B-cell epitope spreading. Epstein-Barr virus (EBV) is an excellent candidate to be involved in molecular mimicry in lupus. EBV infection has been associated with lupus through serological and DNA studies. Infection with EBV results in the production of the viral protein Epstein-Barr virus nuclear antigen-1 (EBNA-1), antibodies against which cross-react with lupus-associated autoantigens, including Ro, Sm B/B', and Sm D1, in lupus patients. The immune response against EBV, and EBNA-1 in particular, differs among lupus patients and healthy controls, with controls maintaining a limited humoral response and failing to produce long-standing cross-reactive antibodies. We hypothesize that the humoral immune response to EBNA-1 in susceptible individuals leads to the generation of cross-reactive antibodies. Through the process of epitope spreading, these cross-reactive antibodies target additional, non-cross reactive autoepitopes, spread to additional autoantigens, and become pathogenic, leading eventually to clinical lupus. This paper reviews some of the current literature supporting roles for EBV exposure and epitope spreading in SLE.     

Accessory cell activity of monocytes in anti-DNA antibody production in systemic lupus erythematosus.

Depletion of monocytes from peripheral blood mononuclear cells of patients with systemic lupus erythematosus (SLE) resulted in a decreased anti-DNA antibody synthesis in vitro. The addition of monocytes restored the response by lymphocytes and the maximum response in the presence of 2.5-8% of monocytes, whereas greater than 15% of monocytes caused rather decreased antibody responses. In order to further evaluate the role of monocytes on an anti-DNA antibody synthesis, we designated an accessory cell index, based on reconstitution experiments using isologous SLE lymphocytes, and compared it in active or inactive SLE and controls. The studies revealed that active SLE monocytes enhanced spontaneously occurring anti-DNA antibody synthesis by SLE lymphocytes. These results indicate that SLE monocytes actively participate in spontaneously occurring anti-DNA autoantibody synthesis in humans.     

C-type virus expression in systemic lupus erythematosus.

Kidneys from patients with lupus nephropathy, non-lupus immune-complex glomerulonephritis and other renal diseases were examined by indirect immunofluorescence for antigens related to a C-type virus from human cells (HEL-12 virus). All 11 specimens of lupus nephropathy contained HEL-12 virus antigens deposited in the same pattern as the immune complexes. The intensity of immunofluorescence with anti-HEL-12 virus serum correlated with the extent of immune-complex deposition. In contrast, nine renal lesions other than lupus nephropathy and seven normal tissues did not react with anti-HEL-12 virus serum. Antibody eluted from one kidney with lupus nephropathy reacted by indirect immunofluorescence with human and dog cells infected with HEL-12 virus but not with uninfected control cells. These findings demonstrate a specific association of lupus nephropathy with a C-type viral antigen that is deposited as antigen-antiviral antibody complex.     

An autopsied case of chronic active Epstein-Barr virus infection complicated in systemic lupus erythematosus and antiphospholipid antibody syndrome]

We have experienced a case of chronic active Epstein-Barr virus infection (CAEBV) complicated in systemic lupus erythematosus (SLE) and antiphospholipid antibody syndrome (APS). A 35-year-old woman was admitted to our hospital with complaints of fever and dyspnea on exertion. She was diagnosed as having SLE on the basis of arthritis, oropharyngeal ulcer, lymphopenia, and positive autoantibodies against DNA, RNP and SSA. The diagnosis of APS was also made because of positive anti-cardiolipin IgG antibodies and the existence of multiple pulmonary infarction with pulmonary hypertension. The administration of 30 mg/day of prednisolone and anti-coagulation significantly improved clinical symptoms. However, she was again admitted to the hospital four months later because of progressive liver damage and pancytopenia. Increment of prednisolone did not improve the clinical situation and she expired because of pulmonary hemorrhage. At autopsy, there were a significant increase of histiocytes with hemophagocytosis and a dense infiltration of atypical lymphocytes in the liver, spleen, lymph nodes and bone marrow. Infiltrated lymphocytes were positive for CD 3 and EBER 1 in immunohistochemical staining and EBVmRNA was detected by in situ hybridization. Final pathological diagnosis was CAEBV with hemophagocytic syndrome in association with lupus nephritis, pulmonary hemorrhage and pulmonary infarction.     

Anti-thyroid peroxidase antibody activity in sera of patients with systemic lupus erythematosus.

Although patients with SLE have autoantibodies to thyroid peroxidase (TPO), IgG from sera of SLE patients does not inhibit TPO activities, in contrast with IgG from sera of patients with thyroid disorders. This finding suggests that the specificities of anti-TPO autoantibodies in SLE are different from those in cases of thyroid disorders. These autoantibodies to TPO should be considered when searching for associations between SLE and autoimmune thyroid disorders.     

Detecting Epstein-Barr virus DNA from peripheral blood mononuclear cells in adult patients with systemic lupus erythematosus in Taiwan

Epstein-Barr virus (EBV) has been found by many serology studies to be associated with systemic lupus erythematosus (SLE). However, the results of DNA studies have been conflicting. Therefore, instead of antibody to EBV, we studied the association between EBV DNA and SLE. In this case-control study in Taiwan, we enrolled 87 SLE patients and 174 age- and sex-matched controls. Peripheral blood mononuclear cells of SLE patients and matched controls were tested for EBV DNA by polymerase chain reaction (PCR) and Southern blot. Of the 87 SLE patients, 71 (81.6%) were found to be positive for EBV DNA, while 85 (48.9%) of the 174 controls (odds ratio 4.64, 95% confidence interval 2.50–8.62, P<0.0001) were positive. While the EBV DNA-positive rate did not decline with age in SLE patients (P>0.05), it did decline with age in controls (P<0.05). Furthermore, based on a real-time quantitative PCR study, we have found a significant difference between EBV viral load in SLE and controls (P=0.008). Therefore, in our molecular study of DNA level, we found evidence for the association of EBV infection and SLE, suggesting that EBV contributes, if not to the development of SLE, then to disease perpetuation.     

Detection of antibodies to the Epstein-Barr virus nuclear antigens in the sera from patients with systemic lupus erythematosus

The sera from 65 patients with systemic lupus erythematosus (SLE) were examined by the immunoblotting method to detect antibodies to Epstein-Barr virus (EBV)-associated antigens, especially EBV nuclear antigens (EBNA), and compared with the sera from 66 healthy subjects roughly age- and sex-matched to the patients. Most sera from patients with SLE defined three major EBV-associated antigens with molecular weights (MW) of 70,000 (70K), 90K and 140K in Raji cells, which must correspond to the EBNA-1, 2, and 3, respectively. Approximately 70% of the sera from SLE patients demonstrated the antibodies to the 90K and 140K antigens, whereas the positive rates of these two antibodies were less than 10% in the sera from healthy subjects. The differences of these positive rates of the antibodies between SLE patients and healthy subjects were statistically highly significant. Antibody to EBNA-1 was conspicuously detected in the sera from both SLE patients and healthy subjects, although the difference between the two groups was still significant. The possible role of EBV infection was discussed on the basis of the pathogenesis of SLE.     

CD4 antibody therapy in systemic lupus erythematosus

The emergence of monoclonal antibody technology has fostered new therapeutic strategies for people with autoimmune diseases. One of the most promising of these strategies involves the use of CD4 monoclonal antibodies, which are effective in animal models for systemic lupus erythematosus, diabetes mellitus, rheumatoid arthritis, myasthenia gravis, and multiple sclerosis. The appeal of CD4 antibodies is enhanced by several factors: (1) their effectiveness does not depend on depletion of target cells; (2) they may block the host immune response to therapy, and (3) they have been well-tolerated in preliminary human trials. The principal obstacle to the use of CD4 monoclonal antibodies stems from their adverse effects on normal immune function.     

The prevalence of antiphospholipid antibody syndrome among systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is an autoimmune disease characterised by excess autoantibody production. It typically affects women of childbearing age. Antiphospholipid antibody syndrome (APLAs) is associated with serious co-morbidity to mother and child characterized by recurrent vascular thrombosis and/or pregnancy associated morbidity. We reviewed SLE patients attending a specialist connective tissue disease clinic both to assess the occurrence of APLAs and its clinical presentations and to audit the effectiveness of screening for APL antibodies in a specialist clinic. 204 patients attended the newly established connective tissue disease outpatient clinic over a twenty-seven month period; 42 (34 female, 8 male) with a diagnosis of SLE. Ten patients (24%), eight female and 2 male with a median age of 38.5 years (range 20 to 64 years) fulfilled the ACR criteria for secondary APLAs (Table 2). The commonest clinical presentation was pulmonary embolus (five patients). Overall 37 patients (88%) with SLE were screened for APLAs during the study period: 94% of females and 62.5% of males were screened (for anticardiolipin antibodies, lupus anticoagulant or both), 27% had evidence of APLAs, 24% had positive antibodies but were asymptomatic. There is a significant occurrence of APLAs among SLE patients. Given the important clinical implications of this disorder including substantial risk of fetal loss and patient morbidity or mortality, routine screening of all SLE patients for APL antibodies is recommended.     

High IgM antibody to human T-lymphotropic virus type I in systemic lupus erythematosus

Twenty-six percent of 53 systemic lupus erythematosus sera had high levels of IgM antibody to human T-lymphotropic virus Type I, significantly more than the 5% of normal controls. Neither IgG antibodies to Type I virus nor IgM or IgG antibodies to Type II virus were increased in lupus. Further analysis using competition immunoassay and Western blot techniques also suggested that the IgM Type I antibodies in lupus sera were directed against viral antigens but did not completely exclude a nonviral reaction. Other studies also have not found IgG antibodies to the Type I virus but have not tested for IgM antibodies. Our study suggests that human T-lymphotropic virus Type I or a related virus may be involved in the pathogenesis of some cases of systemic lupus erythematosus.     

Kinetics of specific anti-influenza antibody production by cultured lymphocytes from patients with systemic lupus erythematosus following influenza immunization.

Specific antibody responses to influenza viral antigens produced by cultured peripheral blood mononuclear leucocytes stimulated with influenza virus or pokeweed mitogen (PWM) have been measured in seven patients with systemic lupus erythematosus (SLE) before and at time intervals after influenza immunization. Cells from two patients stimulated with influenza virus in vitro produced high levels of specific antibody 7 days after immunization. Cells from a third patient produced small amounts of specific antibody at day 14. No antibody was produced by cells from the remaining four patients. Responses were of short duration and were not detectable 1 month after immunization. Specific anti-influenza antibody was induced by PWM only from cells of those patients who responded to virus antigen although absolute levels of antibody produced were not as high. In six patients serum haemagglutination inhibiting antibody to influenza virus was measured, and all six had a greater than four-fold increase. The disparity between in vitro antibody production by peripheral blood mononuclear leucocytes and changes in serum antibody suggests that in patients with systemic lupus erythematosus, in vitro functions of peripheral blood lymphocytes do not reflect the immune system as a whole.     

Abnormal production of B cell growth factor in patients with systemic lupus erythematosus.

In order to clarify the role of B cell growth factor (BCGF) in the pathogenesis of systemic lupus erythematosus (SLE), BCGF production by peripheral blood mononuclear cells (PBMC) and T cells was studied using a new bioassay for BCGF activity. For this purpose, we established an Epstein-Barr (EB) virus-transformed B cell line KS-3.F10 that proliferates only in response to two B cell-specific BCGF, low-mol. wt BCGF (LMW-BCGF) and high-mol. wt BCGF (HMW-BCGF). PBMC from active SLE patients produced less BCGF when stimulated with phytohaemagglutinin (PHA) compared with controls. The decreased BCGF production by PHA-stimulated PBMC from active SLE reverted to control values when SLE became inactive. However, PHA-stimulated T cells from active SLE patients produced more BCGF compared with controls, whereas those from inactive SLE showed normal BCGF production. Spontaneous BCGF production by T cells was not observed in active SLE patients. These findings suggest that decreased BCGF production by SLE PBMC is due to excessive BCGF consumption by B cells in vitro and that SLE T cells produce large amounts of BCGF with appropriate immune stimuli in vivo to promote polyclonal B cell activation.     

Platelet-associated DNA and anti-DNA antibody in systemic lupus erythematosus with nephritis.

We report DNA and specific anti-dsDNA antibody (dsDNAb) in excess of controls, associated with platelets from 35 patients with systemic lupus erythematosus (SLE). Deoxyribonuclease (DNase) treatment of intact platelets resulted not only in a drop in platelet-associated DNA, but also a dramatic fall in platelet-associated dsDNAb. This suggests that at least some DNA and virtually all the dsDNAb is bound to the platelet surface, probably in the form of an immune complex. The quantity of platelet-associated DNA did not correlate with amounts of platelet-associated anti-dsDNA antibody (PAdsDNAb); perhaps because platelets also have receptors for DNA itself. Total platelet-associated IgG was elevated in only six patients with normal PAdsDNab.     

Tuberculosis in patients with systemic lupus erythematosus

In a retrospective analysis of 146 systemic lupus erythematosus (SLE) patients seen over a 5 year period, 17 patients of tuberculosis (TB) were identified yielding a prevalence rate of 11.6%. The median duration of SLE was 12 months (range 2-96 months) and 12/17 patients had disease activity score of more than five. The median duration of steroid treatment was 12 months (range 0-96 months) and the median cummulative dose of steroid was 7.75 gms (range 0-22.1 gms). Pulmonary TB (miliary-5, nonmiliary infiltrates-7 and pleural effusion-2) was the commonest type and there was an average diagnostic delay of approximately 1 month. While, majority of the patients responded adequately to treatment, 1 patient had a relapse and 1 expired due to a combination of active lupus and disseminated TB. Only 1 patient had received prophylactic isoniazid.     

Allogeneic suppression of polyclonal immunoglobulin production in normals and patients with systemic lupus erythematosus.

T lymphocytes suppressing in vitro polyclonal immunoglobulin production can be activated by allogeneic stimuli or concanavalin A (Con A). These cells are deficient in systemic lupus erythematosus (SLE). In order to investigate the cellular requirements for this effect, we studied IgM and IgG biosynthesis by (a) normal and SLE lymphocytes cultured with pokeweed mitogen (PWM) and mitomycin C-blocked allogeneic normal or SLE lymphocytes, and (b) by normal and irradiated lymphocytes cultured with PWM and with Con A-pretreated normal and irradiated allogeneic and autochthonous blocked lymphocytes. Results showed that blocked allogeneic normal cells or blocked Con A-pretreated, normal or irradiated, autochthonous or allogeneic cells served as potent stimuli for suppression of immunoglobulin biosynthesis by normal responder cells, but not by SLE responder cells. This suggests that Con A stimulates a radioresistant suppressor inducer cell which in turn activates a radiosensitive, proliferation-dependent suppressor effector cell; the latter can also be activated by allogeneic stimulation and is deficient in SLE.     

Levamisole in systemic lupus erythematosus.

Two patients with systemic lupus erythematosus complicated with lupus nephritis were treated with levamisole, an immunomodulator. Clinical features, including urinary protein excretion and creatine clearance, were restored in one patient, also immunoparameters such as ANA, Ig-bearing cell number and PHA-skin test. The other patient did not respond to levamisole but did respond to cyclophosphamide.