Low avidity antibodies to double stranded DNA in systemic lupus erythematosus: a longitudinal study of their clinical significance.

In a longitudinal study the relevance of the detection of low avidity antibodies to double stranded DNA (dsDNA) as measured by the polyethylene glycol (PEG) assay in patients with systemic lupus erythematosus (SLE) was evaluated. It was found that 35 patients positive in the PEG assay only--that is, having only low avidity anti-dsDNA in their circulation, had a mild course of their SLE with absence of renal involvement. The PEG assay had little predictive value but a high specificity (90.2%) for clinical exacerbations; furthermore, a change in avidity of anti-dsDNA in such patients was seldom observed. In 14 patients positive in both Farr and PEG assays--that is, with a relative preponderance of high avidity anti-dsDNA, there was a clear correlation between rises in Farr assay and major exacerbations, while the PEG assay on its own was not helpful in predicting disease manifestations; disease manifestations were often heralded by a change in the Farr/PEG ratio, with renal and cerebral exacerbations associated with the greatest increase in the Farr/PEG ratio (more than 10 times the previous value).     

The clinical significance of measuring different anti-dsDNA antibodies by using the Farr assay, an enzyme immunoassay and a Crithidia luciliae immunofluorescence test.

Anti-double-stranded DNA (dsDNA) antibodies are highly specific for the diagnosis of systemic lupus erythematosus (SLE) but are heterogeneous in respect to, for example, avidity, class and cross-reactivity. Sera from 2061 patients were measured by three methods: an enzyme-linked immunosorbent assay (ELISA), an indirect immunofluorescence test with Crithidia luciliae as substrate (CLIF), and the Farr assay, a radioimmunological method based on the ammonium sulfate precipitation of immune complexes. The different anti-dsDNA antibody determinations were evaluated by analysis of patient records. The reason for a reactive Farr assay in 14 patients was predominantly the measurement of antibodies of the IgM class, which are not detected by the ELISA. The detection of additional antibodies to dsDNA of the IgA class, to single-stranded DNA or to histones plays a minor role. In comparison with the Farr assay, we found more positive results with the ELISA, which additionally detects anti-dsDNA antibodies of low avidity. The ELISA might also yield positive values in conditions such as chronic liver diseases, various infections and connective tissue diseases other than SLE. Avoiding the disadvantages of radioactivity, the ELISA is well suited as a screening test for dsDNA antibodies. However, positive results should be confirmed by the CLIF test or preferably by the Farr assay, thus combining sensitivity with specificity.     

Detection of anti-dsDNA as diagnostic tool.

The diagnostic significance of anti-dsDNA determinations was evaluated in 2 different groups of patients. When the immunofluorescence technique (IFT) with Crithidia luciliae and the Farr assay with 3H-labelled-PM2 DNA were applied to a selected panel of 536 sera from patients with various well-defined autoimmune diseases, positive results were obtained only with serum samples from patients with systemic lupus erythematosus (SLE). On the other hand when we screened 4431 sera sent to our laboratory for diagnostic reasons, we observed a high incidence of antibodies to dsDNA in patients who did not fulfil the preliminary American Rheumatism Association's criteria for SLE and did not have the diagnosis SLE. Furthermore, a significant number of the positive sera showed peculiar behaviour in that they were positive only in the IFT on Crithidia luciliae and not in the Farr assay.     

Low avidity antibodies to dsDNA as a diagnostic tool.

An evaluation of the diagnostic value of low avidity antibodies to double stranded DNA (dsDNA) measured by the polyethylene glycol (PEG) assay was undertaken. By routine screening low avidity anti-dsDNA were detected in the serum samples of 106 hitherto unknown patients. Clinical data of these patients were collected and when only low avidity anti-dsDNA was present (n = 92) a varied disease spectrum was observed. A diagnosis of systemic lupus erythematosus (SLE) was established in 48/92 (52%), lupus-like disease in 21/92 (23%), autoimmune hepatitis in 9/92 (10%), rheumatoid arthritis in 8/92 (9%), and mixed connective tissue disease in 2/92 (2%) of all patients. Patients with definite SLE were all older than 45 years and predominantly female (46/48, 96%). They showed a remarkably low incidence of renal disease (2/69, 3%). When high avidity antibodies to dsDNA as measured by the Farr assay were present as well (n = 14) a diagnosis of SLE could be established in 12/14 (86%) of all patients, indicating the secondary importance of low avidity anti-dsDNA in these patients.     

Prognostic value of anti-dsDNA in SLE.

In a prospective longitudinal study 130 patients with systemic lupus erythematosus (SLE) were studied at least monthly for a relationship between the anti-dsDNA levels and disease activity. We observed 13 patients who developed 15 periods of exacerbations of their disease. All 15 exacerbations were preceded by a continuous increase of the anti-dsDNA levels. In 13 of the 15 exacerbations studied the exacerbation was preceded by an increase of anti-dsDNA with a doubling time (T2) of less than 6 weeks; in 4 of the 5 other exacerbations the T2 was less than 10 weeks. Four other patients with an increase of the anti-dsDNA levels showed no exacerbation. In these 4 patients the T2 was larger than 10 weeks. The other 113 patients did not show an increase of anti-dsDNA over the 2 years of monitoring and showed no signs of serious disease activity (no major symptoms). These observations suggest that an SLE patient who is followed up frequently and who shows a continuous increase of anti-dsDNA witha T2 shorter than 10 weeks is bound to develop an exacerbation.     

Anti-dsDNA: choice of assay in relation to clinical value

Summary Antibodies to DNA are quite specific for systemic lupus erythematosus (SLE) and occur in the majority of SLE patients. Therefore, their detection is an important diagnostic aid to the clinician. Detection of anti-dsDNA may precede the diagnosis of SLE by more than a year. Fluctuations in the level of anti-dsDNA in an individual patient may give important information on the clinical status of the patient. Four of the most important methods developed for the measurement of anti-dsDNA antibodies will be discussed in this paper: the Farr assay, the PEG assay, the indirect immunofluorescence test on Crithidia luciliae and the ELISA. They will also be compared with one commercially available (Farr) assay, the Amersham anti-dsDNA kit. Each method, detects a part of the spectrum of anti-dsDNA antibodies produced by a patient. The Farr assay is the most specific for SLE; however, milder forms of the disease in which patients have only low avidity anti-dsDNA may easily be missed by this technique. Clinically, high avidity anti-dsDNA is related more frequently to the occurrence of nephritis, whereas low avidity anti-dsDNA antibodies are found more often in patients with central nervous system involvement. Traditionally, SLE is considered an immune-complex disease, in which inflammatory processes are initiated by local deposition of DNA/anti-dsDNA complexes. More recently, a major role was thought to be played by crossreactions of anti-dsDNA with tissue constituents. Our current view, however, is that such a crossreactivity plays only a minor role; we postulate that binding to glomerular constituents is caused by anti-dsDNA antibodies complexed with DNA and histones.     

The performance of different anti-dsDNA autoantibodies assays in Chinese systemic lupus erythematosus patients

To compare the performance of different commercial anti-dsDNA autoantibody assays, including multiplex-based immunoassay (Bio-Plex), Farr radioimmunoassay (Farr), ELISA, chemiluminescent immunoassay (CLIA), and Crithidia Luciliae indirect immunofluorescence test (CLIFT) in Chinese patients with systemic lupus erythematosus (SLE). SLE patients (n = 119) as well as healthy controls (n = 200) and disease controls (n = 100) were recruited, and serum anti-dsDNA autoantibodies were detected by Bio-Plex, Farr, two ELISA assays (Medical & Biological Laboratories-ELISA, EUROIMMU-ELISA), CLIA, and a standard CLIFT. The correlation of anti-dsDNA autoantibody levels to SLE disease activity was calculated, and the specificity and sensitivity of these methods were measured by receiver-operator characteristic (ROC) curve analysis. In ROC curve analysis, Bio-Plex showed the largest area under the curve (AUC) over other assays. Cutoff adjustment according to ROC enhanced the performance of all quantitative assays. Overall, Bio-Plex and CLIFT have higher specificity (>90.00%). ELISA and CLIA results are correlated with disease activity, and Bio-Plex results have the strongest correlation with SLEDAI score and active renal involvement. Bio-Plex assay has better overall performance in anti-dsDNA detection over Farr, ELISA, and CLIA methods in Chinese SLE patients.     

Clinical significance of anti-dsDNA antibody isotypes: IgG/IgM ratio of anti-dsDNA antibodies as a prognostic marker for lupus nephritis

The objective of this paper is to investigate the association between patterns of anti-dsDNA antibody isotypes and specific clinical manifestations (categorized in renal, musculoskeletal, cutaneous, hematological, pulmonary, neurological and cardiac). Sera of 202 systemic lupus erythematosus (SLE) patients, 33 patients suffering from other autoimmune diseases and 115 healthy blood donors were analysed for anti-dsDNA antibodies by IgG-, IgA- and IgM-specific ELISA, Farr-assay and CLIF. A subset of 24 SLE patients was investigated in a longitudinal study over a period of one to six years. Disease activity of 105 SLE patients was measured according to the ECLAM score. In the cohort of SLE patients 63% were positive for the IgG class, 40% for the IgA and 57% for the IgM class specific anti-dsDNA ELISA. Sensitivity (79%) and specificity (99%) for the diagnosis of SLE appeared to be highest for the ELISA measuring all isotypes of anti-dsDNA antibodies. The concentrations of anti-dsDNA isotypes showed a strong correlation with disease activity. Analysing the relationship between IgG, IgA and IgM anti-dsDNA antibody isotypes and clinical manifestation, we found a significant association of the IgM isotype with cutaneous involvement and of the IgG isotype with lupus nephritis. The IgG/IgM ratio of anti-dsDNA antibodies represented a significant parameter to distinguish patients with lupus nephritis from those without renal involvement. In the longitudinal study, a continuous ratio under 0.8 was associated with absence of renal involvement throughout the investigated period. In conclusion, the evaluation of anti-dsDNA isotypes provides a diagnostic tool to define subsets within SLE patients with different clinical manifestations. In particular, the IgG/IgM ratio of anti-dsDNA antibodies could be used as a prognostic marker for lupus nephritis during the course of the disease.     

The predictive value of fluctuations in IgM and IgG class anti-dsDNA antibodies for relapses in systemic lupus erythematosus. A prospective long term observation

OBJECTIVE—This study investigated the predictive value of rises in IgM class antibodies against double stranded DNA (anti-dsDNA) for ensuing relapses in systemic lupus erythematosus (SLE) in comparison with rises in IgG class antibodies. In addition, it was analysed whether rises in IgM class anti-dsDNA were associated with specific clinical manifestations of SLE.
METHODS—Thirty four of a cohort of 72 SLE patients who were positive for IgM class anti-dsDNA at the start of the study or at the time of a relapse were analysed monthly for class specific anti-dsDNA levels during a median observation period of 19.6 months. Disease activity was scored according to the SLE Disease Activity Index. Anti-dsDNA were measured by IgM and IgG class enzyme linked immunosorbent assay (ELISA) and by Farr assay.
RESULTS—During the study 18 of 34 patients experienced 26 relapses. Twenty two (85%) of the relapses were accompanied by a positive test for IgM class anti-dsDNA by ELISA, 23 (89%) were positive for IgG class anti-dsDNA by ELISA, and 25 (96%) were positive by Farr assay. Patients with rises in IgG class anti-dsDNA by ELISA or in anti-dsDNA by Farr assay had a significantly higher cumulative risk for relapses than patients without those increases (p=0.04 and p=0.03, respectively). This was not the case for rises in IgM class anti-dsDNA (p=0.16). Moreover, a rise in IgM class anti-dsDNA before a relapse was not associated, expressed in terms of odds ratios, with specific clinical manifestations of SLE.
CONCLUSION—Relapses of SLE are frequently accompanied by IgM class anti-dsDNA. Rises of IgM class anti-dsDNA, in contrast with rises in IgG class anti-dsDNA, are not a sensitive tool for predicting a relapse and are not associated with specific clinical manifestations of SLE.

     

Clinical disease activity and titers of anti-dsDNA antibodies measured by an automated immunofluorescence assay in patients with systemic lupus erythematosus

Autoantibodies specific for double stranded DNA (anti-dsDNA Abs) are a serological biomarker of systemic lupus erythematosus (SLE) and constitute useful tools for monitoring many SLE patients. A new automated immunofluorescence and quantitative assay (EliA dsDNA) has recently become available. Its performance has been demonstrated to be equivalent to the Farr and Crithidia luciliae fluorescence (CLIFT) tests. The aim of the present work was to assess the utility of this new assay to monitor clinical activity in a large cohort of SLE patients. To this end, 1020 sera from 181 SLE patients were evaluated by the two methods. Results showed a higher frequency of positive results of anti-dsDNA Abs during lupus flares measured by EliA dsDNA than by CLIFT. Likewise, titers of those Abs were significantly increased in active SLE in comparison with inactive SLE when measured by EliA dsDNA but not by CLIFT. Serum titers of anti-dsDNA Abs by both assays showed a significant negative association with concentrations of C3 and C4. In summary, this retrospective study on a large cohort of patients demonstrated that EliA dsDNA was at least as useful as CLIFT as monitoring tool in the follow-up of SLE patients, but with the advantages of being automated, quick and quantitative.     

Enzyme immunoassays for the detection of IgG and IgM anti-dsDNA antibodies: clinical significance and specificity

A solid phase Enzyme-Linked Immunosorbent Assay (ELISA) was developed for the measurement of IgG and IgM antibodies to double-stranded DNA (anti-dsDNA). This method is sensitive, specific, relatively simple and suitable for routine use. Thus, we evaluated sera from 224 Greek patients with the following autoimmune rheumatic diseases: 54 patients with classical rheumatoid arthritis (RA), 50 patients with primary Sj?gren's syndrome (SS), 41 patients with systemic lupus erythematosus (SLE), 30 patients with scleroderma, 20 patients with idiopathic Raynaud's phenomenon (IRP) and 29 patients with juvenile rheumatoid arthritis (JRA). Sera from 119 age- and sex-matched healthy blood donors were tested as normal controls. The presence of both IgG and IgM anti-dsDNA highly correlated with SLE. However, IgM anti-dsDNA levels were significantly lower. Serum complement C3 and C4 levels correlated negatively with anti-dsDNA levels in the SLE group. Finally, in sequential sera from five SLE patients, the anti-dsDNA activity proved to be a relatively sensitive marker of SLE activity.     

The significance of discrepant Farr and Crithidia luciliae tests

The most specific serological test for systemic lupus erythematosus (SLE) is the detection of anti-dsDNA antibodies by the Farr or Crithidia luciliae (CL) assay. Serological interpretation is difficult when these assays give discrepant results (i.e., one is positive and the other negative). In the present study 34 patients with discrepant results (18 CL positive Farr negative; 16 CL negative Farr positive) were reviewed to determine whether they fulfilled ARA criteria for SLE at presentation or at follow up 1-50 months (mean 15.8 months) later. Only 2 patients had SLE, both of whom fulfilled ARA criteria at presentation. Discrepant CL and Farr assays are associated with SLE uncommonly and rarely precede the development of clinical lupus.     

First clinical trials of a new heteropolymer technology agent in normal healthy volunteers and patients with systemic lupus erythematosus: safety and proof of principle of the antigen-heteropolymer ETI-104

BACKGROUND: The heteropolymer technology was developed to remove pathogens from the circulation. OBJECTIVES: To evaluate the safety and tolerability of a single administration and to establish proof of principle for ETI-104 in normal healthy volunteers (NHV) and patients with systemic lupus erythematosus (SLE) METHODS: The drug was given intravenously to 11 NHV and six patients with SLE. Over 28 days, vital signs were noted, a haematological and chemical analysis of blood and urine was carried out, and adverse events were recorded. CR1 receptor numbers, the ability of antigen based heteropolymers to bind to red blood cells (RBCs), and the clearance of high avidity and total anti-dsDNA antibodies were measured by Farr assays and FACS analysis. RESULTS: No safety measure differed significantly from normal in both groups; no drug related serious adverse events occurred. ETI-104 rapidly bound to RBCs in NHV and patients with SLE. Binding of the drug to RBCs of patients with SLE also caused a rapid reduction of circulating anti-dsDNA antibodies in the plasma 15 minutes after administration, with a maximum reduction of 55% (range 43-62). At 28 days statistically significant decreases were maintained in three patients, while in the other three the values had returned to baseline levels. CONCLUSION: These clinical trials established the safety and the proof of principle of the new immunoconjugate ETI-104. This provides the basis for further development of this technology for numerous indications-for example, therapeutic options for autoimmune diseases or viral and bacterial infections.     

A longitudinal study of high and low avidity antibodies to double-stranded DNA in systemic lupus erythematosus

The role of avidity in the pathogenicity of double-stranded DNA/anti-double-stranded DNA immune complexes in systemic lupus erythematosus (SLE) has been controversial. We used polyethylene glycol to identify low avidity antibodies and the standard Farr assay to detect high avidity antibodies against double-stranded DNA in a longitudinal study of sera from 19 patients with SLE. We found that high and low avidity antibodies to double-stranded DNA did not move independently, but instead, rose and fell in a parallel and relatively fixed manner in these patients. The mechanisms responsible for the changes in titer of anti-double-stranded DNA antibody appeared nondiscriminatory in regard to avidity. In addition, the humoral immune response in SLE depicted by these antibody measurements appeared atypical, lacking maturational features.     

Complement fixation by anti-dsDNA antibodies in SLE: measurement by radioimmunoassay and relationship with disease activity.

We have developed a sensitive, solid phase radioimmunoassay (RIA) to quantify the amount of complement (C') fixation by anti-double-stranded DNA (anti-dsDNA) antibodies and have studied sera from 48 patients with systemic lupus erythematosus (SLE). 46% of the patients were positive in this assay. There was no correlation with serum C' levels, and only weak correlation with anti-dsDNA activity as measured by a solid phase RIA. An association was shown between positive values for C' fixation by anti-dsDNA antibodies and the presence of active lupus (p less than 0.01); there was a similar association with the presence of active renal disease in those patients with raised DNA binding (p less than 0.01). Our results suggest that quantitative measurement of C' fixation by anti-dsDNA antibodies may provide information about the pathogenicity of such antibodies in patients with SLE and be a better guide to potential end organ damage than the conventional measurement of DNA binding.     

Dyslipoproteinemia during the active course of systemic lupus erythematosus in association with anti-double-stranded DNA (anti-dsDNA) antibodies

Dyslipoproteinemia is common in lupus patients. In this study, we investigated the pattern of dyslipoproteinemia in the course of active systemic lupus erythematosus (SLE) in possible association with anti-double-stranded DNA (anti-dsDNA) antibodies. Forty-six lupus patients under 45 years old who fulfilled the American College of Rheumatology revised criteria for the classification of SLE were selected. The exclusion criteria were renal failure, nephrotic syndrome, thyroid or liver disease, diabetes mellitus, obesity, pregnancy and taking drugs that induce dyslipidemia. Disease activity was measured by Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Comparison of the lipid profiles, between active and inactive groups determined high levels of serum TG and VLDL and low levels of serum HDL in active group in comparison with inactive group (P < 0.05). The results indicated that the levels of TG and VLDL were significantly elevated in the patients with positive anti-dsDNA (P < 0.05). Although, the mean of serum HDL levels was also lower in patients with positive anti-dsDNA, the difference was not significant. This pattern of dyslipoproteinemia in active SLE may be associated with the autoimmune mechanisms especially in relation to the presence of anti-dsDNA antibodies.     

Predictive value of complement profiles and anti-dsDNA in systemic lupus erythematosus.

In a prospective study of 143 patients with systemic lupus erythematosus (SLE) the relation between clinical exacerbations, anti-dsDNA levels, and serum levels of complement components, C1q, C4, C3, C5, and C9 was investigated. In 33 out of these 143 patients a major clinical exacerbation of the disease developed. Evaluation of anti-dsDNA levels in relation to disease activity confirmed our earlier finding that anti-dsDNA levels rose before a major exacerbation and decreased after it. In the remaining 110 SLE patients a nearly constant anti-dsDNA level was seen, but none of these patients experienced a major exacerbation. In the 21 SLE patients who developed deterioration in renal function a decrease of C4 followed by decreases of C1q and C3 levels was seen first, starting about 25 to 20 weeks before the first signs of renal involvement. In the 12 SLE patients who developed an exacerbation without renal involvement an inconsistent profile of the complement components C4, C1q, and C3 was observed. C5 levels were hardly affected at all, while C9 levels were in general higher than normal during the exacerbation, irrespective of the type of exacerbation. These results show that, by following the complement and anti-dsDNA profiles, not only can exacerbations be predicted but also a pointer can be obtained about the pattern of disease well before the first clinical signs of an exacerbation appear.     

Digital ulcers/gangrene and immunoglobulin classes/complement fixation of anti-dsDNA in systemic lupus erythematosus patients

The immunoglobulin classes/complement fixation of anti-dsDNA were studied in sera obtained from 17 systemic lupus erythematosus (SLE) patients with digital ulcers and/or gangrene (Group A); 13 SLE patients with leg ulcer, peripheral neuropathy or livedo (Group B); 24 SLE patients with Raynaud's phenomenon (Group C); and 18 SLE patients with active lupus nephritis (Group D). Antibodies to dsDNA of IgG and IgA classes were commonly present (often in high titers) in Groups A and D. However, complement fixation of anti-dsDNA was more common in Group D than in any of the other 3 groups.     

Idiotypic vaccination with a murine anti-dsDNA antibody: phase I study in patients with nonactive systemic lupus erythematosus with nephritis

OBJECTIVE: To determine the safety and immunogenicity of an idiotypic anti-dsDNA vaccine in patients with nonactive systemic lupus erythematosus (SLE) and stable lupus nephritis. METHODS: Patients with SLE with a history of nephritis were randomized for vaccination with the murine anti-dsDNA monoclonal antibody (Mab) 3E10 in a dose ranging, double blind, placebo controlled study (phase I). RESULTS: Of the 9 patients injected with Mab 3E10, 5 showed a human anti-mouse antibody (HAMA) response, in large part antiidiotypic, which developed within the first 3 months in 3 strong HAMA responders, and more than one year after immunization in an initially weak HAMA responder. All but one nonresponder were receiving low dose prednisone. No adverse events, in particular no evidence of lupus flares, and no untoward laboratory findings were reported over a followup of 2 years. CONCLUSION: In patients with stable lupus nephritis, immunization with Mab 3E10 appears safe and can generate a significant antiidiotypic response. Idiotypic vaccination may be an approach to specific immunotherapy of autoimmune lupus nephritis.     

Anti-dsDNA antibody assay: high specificity and sensitivity with a filtration radioassay in comparison to low specificity with the standard ELISA

OBJECTIVE: To evaluate whether a new fluid-phase filtration radioassay possesses both high sensitivity and specificity compared with the currently used ELISA and Farr assays. METHODS: Sequential sera (25 samples) from 9 patients with systemic lupus erythematosus (SLE), sera from 20 patients with SLE possessing anti-dsDNA antibodies by the Crithidia assay, 75 patients with rheumatoid arthritis possessing rheumatoid factors, 50 healthy control subjects, 767 from patients with type 1 diabetes, and a commercial standard serum sample were tested for anti-dsDNA antibodies with the 3 different assays. RESULTS: Of serial dilutions of a standard anti-dsDNA antibody sample, only the highest positive sample (50 IU/ml) in the ELISA and the highest 2 positive samples (50 and 25 IU/ml) in the Farr assay were above the normal range. In contrast, all dilutions (to 2.5 IU/ml) of the standard anti-dsDNA antibody sample were above the normal range in the filtration radioassay. Using the values of 50 healthy control subjects in each assay to define the normal range, all 25 sequential sera from 9 patients with SLE were positive. In addition, 20/20 of the SLE individual sera, 2/75 (2.7%) of the RA sera, and 12/767 (1.6%) of the diabetes sera were positive (signal above normal range) in the filtration radioassay. The SLE sera were further examined in 2 additional assays, ELISA and Farr assay, and both assays were less sensitive and specific compared with the filtration radioassay. CONCLUSION: The fluid-phase filtration radioassay demonstrated high sensitivity and specificity for the detection of anti-dsDNA antibodies in SLE, with the standard ELISA exhibiting lower specificity. We suggest that testing for anti-dsDNA antibodies can be improved using a fluid-phase filtration radioassay in comparison to commercial assays.