Detection of anti-DNA antibody using synthetic antigens. Characterization and clinical significance of binding of poly (deoxyadenylate-deoxythymidylate) by serum

Significance of enzyme linked immunosorbent assay (ELISA) for antibodies to double stranded and single stranded DNA in patients with lupus nephritis: correlation with severity of renal histology

The correlation between renal histology and class specific (IgG and IgM) antibodies to double stranded DNA (dsDNA) and single stranded DNA (ssDNA) was studied by enzyme linked immunosorbent assay (ELISA) in 40 untreated patients with systemic lupus erythematosus (SLE). The levels of IgG antibodies to dsDNA were significantly higher in patients with World Health Organisation class IV nephritis than in those with class I, class II, or class III nephritis. IgG antibodies to ssDNA were higher in patients with class IV than in those with class II nephritis. IgG antibodies to dsDNA showed a close correlation with the histological activity score and the amount of electron dense deposit. IgG antibodies to ssDNA showed only a weak correlation with the renal histological activity score. IgM antibodies to dsDNA and IgM antibodies to ssDNA were not correlated with renal histological features. Patients with moderate to severe nephritis had a lower ratio of IgM antibodies to dsDNA to IgG antibodies to dsDNA than those with mild nephritis. These results indicate that the measurement of IgG antibodies to dsDNA is predictive in evaluating renal histological activity in patients with SLE.

Anti-DNA antibodies induced by BK virus inoculations. Demonstration of the specificities for eukaryotic dsDNA and synthetic polynucleotides

The ability of BK virus to induce anti-DNA antibodies in rabbits, and the ability of these antibodies to bind natural eukaryotic DNA and synthetic polynucleotides have been analysed. The specificity of the binding was assayed by inhibition of anti-dsDNA and -ssDNA ELISA tests with dsDNA, ssDNA, and synthetic single-stranded as well as double-stranded polynucleotides. The anti-dsDNA activity of two rabbit antisera was effectively inhibited by dsDNA and ssDNA and poly(dAdT)-poly(dAdT). The other nucleotide antigens produced relatively less inhibition. The anti-ssDNA binding was most efficiently inhibited by the homologous antigen, whereas inhibition by dsDNA only reached approximately 70% of the maximum as defined by ssDNA as inhibitor. This indicates the existence of a selective anti-ssDNA antibody population and a population recognizing both ssDNA and dsDNA within the sera. Cross-reaction of the induced anti-DNA antibodies with phospholipid antigens, such as cardiolipin, phosphatidylic acid, and bacterial cell surface, could not be demonstrated. We conclude that antibodies resulting from inoculation with BK virus specifically bind to dsDNA and ssDNA and possess a high affinity for the synthetic duplex poly(dAdT). In this way, they have some similarities with anti-DNA antibodies encountered in SLE (systemic lupus erythematosus) in both man and mouse.

Endogenous circulating DNA in systemic lupus erythematosus. Occurrence as multimeric complexes bound to histone

Little is known about endogenous systemic lupus erythematosus (SLE) plasma DNA even though it is the presumed precursor of DNA-containing immune complexes, thought to play a central role in lupus glomerulonephritis. DNA purified from SLE plasma formed discrete bands, corresponding to sizes of about 150-200, 400, 600, and 800 bp, closely resembling the characteristic 200 bp "ladder" found with oligonucleosomal (ON) DNA. By radiolabeling DNA while in whole plasma, the very small amounts present could be further characterized. All of 24 such specimens formed two or more discrete bands on 6% PAGE. Detergent treatment of plasma resulted in a DNA migration pattern similar to that of purified DNA, suggesting disruption of DNA-protein complexes. DNA purified from authentic ON and detergent-treated ON behaved similarly. A significant portion of DNA, labeled in SLE plasma could be specifically immunoprecipitated with monoclonal antihistone antibody as was the case with ON. These immunoprecipitates, when redissolved, exhibited the expected size distribution upon PAGE. It is concluded that DNA in SLE plasma occurs as a series of multimeric complexes, at least a portion of which is noncovalently bound to histone. These results are consistent with an ON-like structure for SLE plasma DNA as had been suggested by theoretical considerations and may have important implications for its immunologic behavior in SLE and perhaps other disorders.

Antibodies raised against denatured DNA bind to double-stranded DNA

Antibodies raised against denatured DNA complexed with methylated bovine serum albumin have been reported to react with ssDNA but not with dsDNA. Using a highly sensitive avidin-biotin microELISA, we report that such antibodies also bind to dsDNA. Antibodies which reacted with ssDNA and dsDNA were found to be of IgG type. The antibodies did not react with tRNA and rRNA. The binding of antibodies to dsDNA was partially inhibited by individual deoxyribonucleotides. ssDNA as well as dsDNA inhibited the binding of antibodies to dsDNA. The binding of these antibodies to supercoiled and relaxed forms of pBR322 DNA was demonstrated by gel retardation assay. The cross-reaction with ssDNA was observed even after affinity purification on native DNA-cellulose. The antibodies were also shown to bind to poly(dA-dT).poly(dA-dT).

Structural requirements of DNA used in the Farr assay to detect antibodies directed against double-stranded DNA

The measurement of antibodies to DNA in SLE requires the use of double-stranded DNA (dsDNA), demonstrably free of single-stranded regions. Such dsDNA preparations can, however, contain other structural components. In this study DNA preparations with defined structure, both secondary (single- and double-stranded and random base-paired) and tertiary (superhelical and open circular), were used in the Farr assay to measure the DNA binding of sera from patients with SLE and related connective-tissue diseases. The presence of true single-stranded DNA regions in denatured DNA, native DNA, and dsDNA containing single-stranded regions increased the DNA binding measured in all sera. DsDNA, whether intact or containing small regions of random base-pairing, was bound by sera from the majority of patients with SLE but not by non-SLE sera. Superhelical dsDNA from bacteriophage PM2 was bound by SLE sera to a greater extent than linear dsDNA was. Inhibition experiments suggested that this difference in binding to DNA according to tertiary, as opposed to secondary, structure is because there are fewer available binding sites on superhelical dsDNA. DNA binding, as measured by the Farr assay, can thus be influenced by both secondary and tertiary DNA structure. Using superhelical DNA, advantage can be taken of the dsDNA form plus tertiary structure to enhance DNA binding of SLE sera beyond the levels achieved using linear dsDNA.

Measurement of serum DNA binding in chronic active hepatitis and systemic lupus erythematosus using the Farr assay

Antibodies to double-stranded DNA (dsDNA), generally regarded as highly specific for systemic lupus erythematosus (SLE), have also been reported in chronic active hepatitis (CAH). Using the Farr assay and E. coli DNA, fractionated by benzoylated-naphthoylated-DEAE cellulose chromatography into dsDNA and dsDNA containing single-stranded regions, we compared the serum DNA binding of CAH and SLE patients. Although CAH sera were found to have dsDNA binding significantly above the normal control group such binding was of low level and we could find no evidence of markedly elevated dsDNA binding in CAH. However 12 of the 20 CAH sera studied did bind preferentially to dsDNA containing single-stranded regions suggesting the presence of anti-single-stranded DNA antibodies. We conclude that the description of elevated anti-dsDNA antibodies, as measured by the Farr assay, in CAH is due to the interaction of anti-single-stranded DNA antibodies or other serum components with single-stranded DNA contaminating dsDNA preparations.

Spontaneous in vitro production of anti-DNA and anti-RNA by systemic lupus erythematosus and normal peripheral blood mononuclear cells

The spontaneous in vitro production of anti-DNA and anti-RNA by peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE) and from normal subjects was evaluated employing sensitive solid-phase assays that are specific for these antibodies. PBMC from SLE patients produced more IgG anti-DNA and anti-RNA than did normal PBMC (P less than 0.01). In vitro production of IgG anti-DNA appeared to correlate with serum DNA bindings (r = 0.72, P less than 0.005). Similar amounts of IgM anti-DNA and anti-RNA were produced by both SLE and normal PBMC. However, IgM anti-DNA antibodies always appeared to be directed against determinants on denatured DNA. Only PBMC from SLE patients produced IgG antibodies to native DNA.

Complexed autoantibodies in patients with juvenile connective tissue diseases, isolated by rate-zonal ultracentrifugation

Selected sera from one patient with systemic lupus erythematosus, two with mixed connective tissue disease, one with dermatomyositis, one with progressive systemic sclerosis and one with juvenile rheumatoid arthritis were investigated for autoantibodies after fractionation by computerized rate-zonal ultracentrifugation. Anti-Smith antibodies sedimented in an area from 6-11 S and anti-ribonucleoprotein from 6-13 S. IgG anti-IgG and IgG antinuclear antibodies (ANA) were present in free or complexed form in the 6-13 S area. IgM ANA occurred as 7 S IgM in patients with systemic lupus erythematosus and mixed connective tissue disease, whereas IgM ANA sedimented in the 19 S area in patients with dermatomyositis and progressive systemic sclerosis. Complexes containing IgG anti-IgG and ANA, positioned in the 6-13 S area are likely to play a significant role in the pathogenesis of systemic lupus erythematosus and mixed connective tissue disease.

Partial purification and characterization of plasma DNA and its relation to disease activity in systemic lupus erythematosus

This study reports the partial isolation and characterization of plasma DNA by phenol extraction and concentration of the extract. DNA, identified by immunologic and chemical methods, was found in plasma from both normal persons and patients with systemic lupus erythematosus in amounts varying from 0.004 to 0.4 micrograms/ml. The DNA was predominantly of low molecular weight, approximating 100 to 200 base pairs. Patients with lupus tended to have higher concentrations of plasma DNA than normal persons, with considerable overlap between the groups. Plasma DNA concentrations correlated inversely with titers of antibody to DNA but not strongly enough for prediction of either variable in individual cases. Many patients had high levels of plasma DNA and its antibody without clinical nephritis. These results indicate the ubiquity of plasma DNA and suggest the necessity of factors other than mere presence of DNA and its antibody for initiation of glomerular damage in systemic lupus erythematosus.

The prevalence of antibodies to histones induced by procainamide in old people, in cancer patients, and in rheumatoid-like disease

Antibodies to histones were found to be most commonly responsible for the positive antinuclear antibody (ANA) test in asymptomatic patients treated with procainamide, in old people, in patients with neoplastic diseases, and in young women affected with a rheumatoid-like disease. Only in a very few patients were antibodies to dDNA and nucleoproteins demonstrated. Antibodies to nDNA were not found. The antibodies to histones were demonstrated by two methods: absorption of ANA-positive sera with a histone solution and subsequent performance of an ANA test; and acid elution of histones from thyroid sections followed by histone reconstitution.

Enzyme immunoassay for antibodies to native DNA. Specificity and quality of antibodies

An enzyme immunoassay was developed to detect antibodies to native DNA; DNA coating conditions that maximized sensitivity, specificity, and reproducibility were selected. Sera of patients with systemic lupus erythematosus (SLE) were positive more frequently by this immunoassay than by the Crithidia luciliae assay or by counterimmunoelectrophoresis. By enzyme immunoassay, 94% of sera with active SLE and 70% of sera from patients with inactive SLE were positive, as were 16% from those suspected of having SLE, and 2.5% of normal persons. Specificity for native DNA was shown for both SLE and normal sera by inhibition studies and by S1 nuclease treatment of polystyrene-bound native DNA. The enzyme immunoassay correlated more with serum hemolytic complement levels that did the other 2 assays, suggesting that it detects biologically more relevant anti-DNA antibodies than do the other 2 tests.

A sensitive solid phase microradioimmunoassay for anti-double stranded DNA antibodies

A sensitive solid phase microradioimmunoassay has been developed for measurement of antidouble stranded DNA (dsDNA) antibodies. In this procedure, advantage has been taken of the capacity of poly-L-lysine (PLL) to facilitate the binding of pure dsDNA to plastic surfaces. In the absence of PLL, binding did not occur. Diluted sera were incubated in PLL-treated dsDNA-coated microtitration trays and anti-dsDNA Ig measured using affinity purified 125I-anti-Ig of high specific activity. The synthetic DNA, poly dA-dT, was used as a model for dsDNA. In initial experiments, specific anti-DNA binding could not be demonstrated because of high background binding of patient Ig to PLL-treated surfaces. This was reduced by diluting test sera and anti-Ig in buffer containing 2% BGG and 1% BSA. Specificity of the assay for DNA was demonstrated by absorbing the anti-DNA activity on DNA-coated plastic. The binding of systemic lupus erythematosus (SLE) patient serum Ig to poly dA-dT coated trays did not diminish after digestion with nuclease S1, suggesting that the synthetic polymer is an appropriate model for dsDNA. Patient and normal sera were screened for anti-dsDNA activity using poly dA-dT as antigen. None of the 38 normal sera, 23 of 35 active SLE sera, 1 of 25 treated SLE, 4 of 35 rheumatoid arthritis, 3 of 35 scleroderma, and 1 of 13 polymyositis sera demonstrated positive anti-dsDNA activity. The anti-dsDNA values obtained in the radioimmunoassay correlated significantly with those obtained in the Crithidia luciliae assay.

Antibodies to polyadenylic acid in patients with myasthenia gravis

Sera from 100 patients with myasthenia gravis and 45 patients with non-myasthenia gravis neuromuscular diseases were studied for antibodies to poly rA, poly rA-rU, native and denatured DNA. All patients with myasthenia gravis had significant anti-acetylcholine receptor antibodies with a mean titre of 1.2 X 10(-7)M. Forty-eight per cent of the myasthenia gravis patients had anti-poly rA antibody levels which were greater than 3 standard deviations from the mean of 65 control patients by Millipore filter radioimmunoassay. The antibody was specific for poly rA and present in a much higher frequency than antibodies to the other nucleic acids tested. Sucrose-gradient ultracentrifugation demonstrated that the antibody was limited to the IgM class alone. Mechanisms relating these findings to a more generalized immunological dysfunction are discussed.

Secondary structure in denatured DNA is responsible for its reaction with antinative DNA antibodies of systemic lupus erythematosus sera

Experiments were designed to determine the basis for the strong competitive reaction of denatured DNA with systemic lupus erythematosus (SLE) antinative DNA antibodies. Secondary structure in denatured DNA was reflected in hyperchromicity upon heating and in multiphase kinetics of its digestion by S1 nuclease. Partial digestion by S1 nuclease completely eliminated the ability of denatured DNA to react with antidenatured DNA antibodies, but not its ability to react with SLE sera. S1 nuclease-resistant cores were isolated from extensively digested denatured DNA. These cores had secondary structure, including some stable fold-back helical regions. The cores, from 20 to several hundred base pairs in size, competed with native DNA for binding by SLE sera. Other experiments measured reactions of denatured DNA under conditions that affected its secondary structure content. Its competitive activity decreased as temperature was increased from 0 degrees to 37 degrees C, whereas the activity of native DNA was not altered in this temperature range. With DNA pieces of 90-110 base pairs, native fragments were much more effective than the denatured fragments, in which stable helical structure is less likely to occur than in high molecular weight denatured DNA. Competitive assays with mononucleotides, oligonucleotides, homopolymers, and RNA-DNA hybrids also indicated that two strands of polydeoxyribonucleotide were required for optimal reactions with these SLE serum antibodies. The antibodies can measure stable helical regions in denatured DNA; they may also stabilize short helical regions that occur in an equilibrium of conformational forms.

Antibody to synthetic poly dAT: correlation with antibody to native DNA and specificity for SLE

Antibodies to synthetic 3H-poly dAT have the advantage over antibody to native DNA in that they have a higher degree of specificity for systemic lupus erythematosus (SLE). This is because poly dAT eliminates the problem of measurement of single stranded antibodies that are not specific for any one condition but which may be detected by native DNA preparations which usually contain single stranded regions. The overall degree of correlation between the two antibodies is good in SLE. Antibodies to poly dAT correlate well with clinical evidence of disease activity but in this study were not particularly associated with the presence of renal disease.

The role of antibodies directed against double-stranded DNA in the manifestations of systemic lupus erythematosus in childhood

The specificity of antibodies directed against dsDNA for SLE in a childhood population was tested by analyzing sera from 62 children with lupus and 283 children with other known or suspected autoimmune diseases. The role of these antibodies in the manifestations of SLE was then examined by correlating dsDNA Ab titer with clinical manifestations in 311 sera from 20 children followed for a mean of 51 months. Antibodies to dsDNA were found to be highly specific for SLE. The presence of antibodies in titers of 1:80 or greater correlated with the presence of active disease, arthritis, and rash, but not with azotemia, proteinuria, or increasing proteinuria; this indicated that their role in the induction of lupus nephritis was different from that in the induction of rash and arthritis. This may be due to a requirement for small immune complex formation during times of antigen excess in the initiation of lupus nephritis.

Immunochemical characteristics of antibodies to DNA in patients with active systemic lupus erythematosus

To investigate the suggestion that qualitative immunochemical characteristics of antibodies to DNA (anti-DNA) may be of importance in the pathogenesis of nephritis in systemic lupus erythematosus (SLE), we used the Crithidia luciliae (CL) immunofluorescence test to determine the titre, immunoglobulin (Ig) class and complement-fixing activity of anti-DNA in thirty-five patients with active SLE. Eighteen of these patients had active lupus nephritis (Group I) and the remaining seventeen had no clinical evidence of renal involvement (Group II). Anti-DNA was detected in twenty-eight patients, and was present more frequently and in higher titre (P less than 0.01) in Group I than in Group II. Anti-DNA of all three Ig classes studied (IgG, IgM and IgA) was present in twenty-three out of twenty-eight cases. The ratio of IgG to IgM anti-DNA did not differ in the two groups of patients. Complement-fixing antibodies were detected in thirteen patients in Group I and five patients in Group II. The titre of complement-fixing activity was strongly correlated with titre of anti-DNA. DNA-binding capacity was also determined in these by a millipore filter (MF) assay. A highly significant correlation between DNA binding by MF and CL was found in Group I patients, while no correlation was found in Group II patients. These findings suggest that (1) anti-DNA with specificity for determinants found in CL, presumably native DNA, are more highly correlated with the presence of active renal lupus than are antibodies directed toward other DNA determinants, and (2) the major characteristic of anti-DNA found to be associated with nephritis was quantity of antibody. Most patients had anti-DNA of all Ig classes regardless of the presence of renal disease. Complement-fixing activity of anti-DNA could not be related to the occurrence of renal disease independently of anti-DNA titre.

Anti-native DNA detection by the Crithidia luciliae method: an improved guide to the diagnosis and clinical management of systemic lupus erythematosus

The clinical value of the Crithidia luciliae (CL) method for detection of antibodies to native DNA (nDNA) was assessed. Significant titers were limited almost exclusively to patients with active systemic lupus erythematosus (SLE). Evaluation of sera from patients at the onset of active lupus demonstrated elevated anti-nDNA levels in 80% of subjects with active disease and in 94% of patients with clinically evident lupus nephritis. In longitudinal studies, rising titers of anti-nDNA were invariably accompanied by exacerbation of lupus activity. These findings suggest that the CL method correlates more closely with active SLE than do other anti-DNA methods in common use and indicate that it will prove highly useful in the diagnosis and management of SLE.

DNA binding activity of serum from patients with systemic lupus erythematosus

The reaction conditions essential for reproducible use of the cellulose ester membrane filter assay for anti-DNA antibody levels in patients with systemic lupus erythematosus are described. A dependence of DNA-binding capacity on serum concentration was observed in the assay, requiring that serum concentrations be comparable in determinations of DNA-binding activity of different sera and when comparing different published studies. The DNA-binding capacity of serum from lupus patients was found to be significantly different from that of healthy controls. However, the binding capacities were not significantly different between lupus patients with and without nephritis. The relative avidity of the anti-DNA antibodies were estimated from plots of 1/DNA bound vs 1/DNA free and these data indicate that the avidities of the antibodies from the two groups of lupus patients are not significantly different. This observation suggests that the tightness of binding between the DNA and the serum anti-DNA antibodies cannot be used to predict immune complex-induced nephritis in lupus patients.

Evaluation of a semiautomated prestandardized immunofluorescence test system for detection of anti-native deoxyribonucleic acid antibodies

An immunofluorescence-native deoxyribonucleic acid (nDNA) antibody test system (Zeus Scientific, Inc.) was compared with a radioimmunoassay procedure (FARR assay) for detecting anti-nDNA antibodies in human serum. Double-blind studies of split samples obtained from 236 patients showed an 80% correlation between the immunofluorescence-nDNA antibody test system and the radioimmunoassay procedure. Studies of sera from patients with known diagnoses showed positive nDNA antibody findings in biopsy-prove n systemic lupus erythematosus only. The immunofluorescence-nDNA antibody test system provides a reliable, simple, and economically feasible alternative method for detecting nDNA antibodies that can be employed in any laboratory equipped with a fluorescence microscope.

The effect of normalization of serum complement and anti-DNA antibody on the course of lupus nephritis: a two year prospective study

A prospective study was carried out in 25 patients with systemic lupus erythematosis (SLE) on the effect of normalizing serum complement (CH50) and anti-DNA antibodies on the course of lupus nephritis. In 16 of the 25 patients, CH50 was maintained within the normal range for two years. Urinary protein excretion increased or remained low in all 16. Repeat renal biopsies were performed in 10 of these 16, and disclosed either stabilization of glomerular disease or diminution. In the nine patients in whom CH50 could not be normalized with tolerated doses of drugs, urinary protein excretion increased or remained increased. Repeat renal biopsies in six of these nine patients were carried out and showed worsening of glomerular disease in five. No clear-cut correlation was found between urinary protein excretion or renal disease and the serum levels of anti-DNA antibody. We conclude from these observations that continuous normalization of CH50 by drug therapy in patients with SLE is associated with stabilization or diminution of lupus nephritis.

Direct evidence for circulating DNA/anti-DNA complexes in systemic lupus erythematosus

Fifteen serum cryoprecipitates from 28 patients with systemic lupus erythematosus (SLE) contained DNA demonstrable by counterimmunoelectrophoresis after exhaustive digestion of cryoimmunoglobulin with pronase. The majority of these cryoprecipitates also exhibited increased DNA binding activity in a modified Farr assay. Both DNA and anti-DNA antibody were enriched in the cryoprecipitates relative to the supernatant serum level. These data provide direct evidence for the presence of DNA/anti-DNA complexes in the circulation of patients with SLE.

Binding of synthetic double-stranded DNA by serum from patients with systemic lupus erythematosus: correlation with renal histology

Detection of antibody to double-stranded DNA by direct binding assays has proved useful in clinical management of patients with systemic lupus erythematosus (SLE). Recent confusion regarding specificity of these antibodies for SLE appears to be due, at least in part, to contamination of natural DNA preparations with nondouble-stranded DNA antigens. Measurement of binding of a synthetic, self-complementary DNA copolymer (dAT) rather than of natural DNA (KB) has been shown to obviate some of these difficulties, apparently because of freedom of dAT from nondouble-stranded DNA antigens. Among the advantages found in this way was a higher degree of specificity of antibodies to double-stranded DNA for clinically-judged active lupus nephritis than had been suspected. Since activity of nephritis is difficult to assess clinically, histologic data were sought to confirm these observations. Thirty-two kidney specimens were examined by light and/or electron microscopy. The degree of histologic activity and the amount and location of glomerular electron-dense deposits were semiquantitated blindly. The binding of both dAT and KB DNA was measured by the ammonium sulfate method. Correlation with the amount of electron-defense deposits was highly significant for dAT binding and somewhat less so for KB DNA binding as determined by both parametric and nonparametric statistical methods. Significant correlation with histologic activity was found for dAT but not KB DNA binding. These results are consistent with previous data and suggest that dAT binding may provide a useful, noninvasive means of clinically assessing both nephritis activity and the intensity of glomerular immune-complex deposition as reflected by the amount of electron-dense deposits. If it can be confirmed that the latter provides long-term prognostic information, then dAT binding (and perhaps its reponse to therapy) may also prove of value in this regard.