Deoxyribonucleic acid strandedness. Partial characterization of the antigenic regions binding antibodies in lupus erythematosus serum

Structural modification of DNA--a therapeutic option in SLE?

Systemic lupus erythematosus (SLE) is an autoimmune disease that affects multiple organs, with glomerulonephritis representing a frequent and serious manifestation. SLE is characterized by the presence of various autoantibodies, including anti-DNA antibodies that occur in approximately 70% of patients with SLE and which contribute to disease pathogenesis. Consequently, immunosuppressive therapies are applied in the treatment of SLE to reduce autoantibody levels. However, increasing evidence suggests that DNA--especially double--stranded DNA-constitutes an important pathogenic factor that is able to activate inflammatory responses by itself in autoimmune diseases. Therefore, modifying the structure of DNA to reduce its pathogenicity might be a more targeted approach for the treatment of SLE than immunosuppression. This article presents information in support of this strategy, and discusses the potential methods of DNA structure manipulation--in light of data obtained from mouse models of SLE--including topoisomerase I inhibition, administration of DNase I, or modification of histones using heparin or histone deacetylase inhibitors.

The fine specificity of IgG antiguanosine antibodies in systemic lupus erythematosus

The antigen specificity, isotype, and subclass of antinuclear antibodies may be related to their pathogenicity in systemic lupus erythematosus (SLE). Our laboratory found that IgG antibodies that bound the nucleoside, guanosine, occurred frequently in SLE patients. In contrast, sera from healthy subjects contained IgM but not IgG antiguanosine antibodies. The present studies were designed to characterized the fine specificity of IgG antiguanosine antibodies in SLE and compare them with IgM antiguanosine antibodies in normal sera. Serum antinuclear antibodies from six healthy subjects and six SLE patients were isolated by affinity binding to guanosine and measured by an enzyme-linked immunosorbent assay (ELISA). IgM in normal sera, and both IgM and IgG in SLE sera bound guanosine. IgM antiguanosine antibodies in normal sera were polyspecific and bound other nucleosides and 1-methylguanosine but not denatured DNA (ssDNA). In contrast, IgG antiguanosine antibodies from the SLE patients bound guanosine and ssDNA but not other nucleosides or 1-methylguanosine. SLE IgM antiguanosine antibodies had the same fine specificity and bound guanosine and ssDNA but not any of the other nucleosides. These results suggest that SLE IgG and IgM antiguanosine antibodies have fine specificity in contrast to the polyspecific IgM antibodies in normal sera. In addition, subclass analysis indicated that all SLE patients had either IgG1 or IgG3 subclass of antiguanosine antibodies that bind complement. Characterizing the isotype, subclass, and fine antigen specificity of antiguanosine antibodies should assist in evaluating their potential pathogenicity in SLE.

Effect of corticosteroids on serum antinuclear antibodies in man

The effect of prednisone on serum levels of IgG antibodies to viral and bacterial antigens was measured and compared to its effect on IgG antibodies to nuclear antigens in 8 patients with systemic lupus erythematosus. Prednisone at 15-80 mg/day (mean 55 mg/day) for 14-30 days (mean 19 days) lowered the serum IgG by an average of 22% (p less than 0.005). An even greater reduction in IgG antinuclear antibodies occurred (mean 43%, p less than 0.001) including responses to double stranded DNA, single stranded DNA, and the nucleosides, adenosine, guanosine, cytidine and thymine riboside. In contrast, there was no alteration in serum IgG antibody levels to influenza virus vaccine and pneumococcal vaccine antigens. These results suggest that prednisone has a selective effect on the expression of autoimmunity which may, in part, be responsible for its clinical efficacy in systemic lupus erythematosus.

Specificity of anti-nucleoside antibodies in systemic lupus erythematosus

The titer of IgG antinucleoside antibodies in the sera of 162 individuals was determined by an enzyme-linked immunosorbent assay. The nucleosides used in the assay were adenosine, cytidine, guanosine, and thymine-riboside conjugated to human serum albumin. The specificity of IgG antinucleoside antibodies was indicated by appropriate reduction in antibody binding after solid-phase adsorptions of antibody with specific immobilized nucleoside conjugates. Disease-associated increases in serum IgG antibodies to cytidine and guanosine but not to adenosine or thymine-riboside occurred in patients with systemic lupus erythematosus (SLE). The epitope density of nucleosides in the conjugates and differences in the sensitivity of each nucleoside assay were not responsible for disease-associated IgG antinucleoside antibody responses. These findings support a possible pathogenic role for cytidine and guanosine as antigens or crossreactive antigenic determinants in some patients with SLE.

Antibodies to native DNA and serum complement (C3) levels. Application to diagnosis and classification of systemic lupus erythematosus

The sensitivity and specificity of the presence of antibodies to native DNA and low serum C3 levels were investigated in a prospective study in 98 patients with systemic lupus erythematosus who were followed for a mean of 38.4 months. Hospitalized patients, patients with other connective tissue diseases, and subjects without any disease served as the control group. Seventy-two percent of the patients with systemic lupus erythematosus had a high DNA-binding value (more than 33 percent) initially, and an additional 20 percent had a high DNA-binding value later in the course of the illness. Similarly, C3 levels were low (less than 81 mg/100 ml) in 38 percent of the patients with systemic lupus erythematosus initially and in 66 percent of the patients at any time during the study. High DNA-binding and low C3 levels each showed extremely high predictive value (94 percent) for the diagnosis of systemic lupus erythematosus when applied in a patient population in which that diagnosis was considered. The presence of both abnormalities was 100 percent correct in predicting the diagnosis os systemic lupus erythematosus. Both tests should be included in future criteria for the diagnosis and classification of systemic lupus erythematosus.

Antibodies to single-stranded DNA in patients with discoid lupus erythematosus

Sera from 31 patients with discoid lupus erythematosus were examined for the presence of antibodies to single-stranded and native DNA. None of these sera had antibodies to native DNA. When rabbit anti-human IgM was used, 6 of 28 patients had elevated binding, whereas only 1 of 29 patients had abnormal binding when antiIgG was used. The IgM nature of this response was confirmed when we demonstrated the binding activity in heavy fractions from gel filtration. We concluded that at least one-fifth of patients with discoid lupus erythematosus have IgM antibodies to single-stranded DNA.

The clinical significance of the antinuclear antibody test as a screening procedure for DNA antibodies in SLE

During the two-year period (1st October 1974-30th September 1976), 2979 sera were tested for DNA antibodies by the Farr test. One thousand six hundred and ninety-five of these were tested because they had high ANA titres (1/256 or greater). In this group 285 sera were found to have raised DNA binding capacities (DNA-bc), 86 of which were found in patients having diagnoses other than SLE. When the diagnoses were reviewed following the finding of a raised DNA-bc, 55 of these patients were found to be suffering from SLE. Of the 1284 sera tested for DNA antibodies without the prior ANA screening procedures, 288 were positive, 36 of which came from patients not considered to have SLE; 30 of these patients were subsequently shown to have SLE. Thus the DNA-bc test is an important tool in the diagnosis of SLE, and the ANA test appears to be a valuable screening procedure. The level of DNA-bc was not of any diagnostic value.

Restricted subpopulations of DNA antibodies in kidneys of mice with systemic lupus. Comparison of antibodies in serum and renal eluates

Sera from MRL/1, BXSB, and NZB/NZW mice, which develop IgG antibodies to DNA and glomerular deposits of DNA-antiDNA immune complexes, were studied by isoelectric focusing. A large array of IgG antibodies with isoelectric points ranging from pH 5.5--9.0 were found to bind double-stranded DNA. Antibodies with isoelectric points from 8.0--8.5 were significantly more frequent than antibodies focusing in all other pH ranges. In contrast, glomerular eluates from MRL/1 and NZB/NZW mice contained a restricted number of DNA-binding bands, all of which focused at pH 8.0--9.0. Anti-DNA with isoelectric points from pH 8.0--9.0 may be more pathogenic for the kidney than other subpopulations.

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.

Measurement of anti-double-stranded DNA antibodies in major immunoglobulin classes

A solid-phase radioimmunoassay for quantitating anti-double-stranded deoxyribonucleic acid antibodies (anti-dsDNA) in IgG, IgM and IgA classes has been devised. A distinct feature of the method is an application of polystyrene tubes coated with poly-L-lysine, through which dsDNA could be bound firmly to a solid phase. Studies on patients' sea as well as normal sera revealed that anti-dsDNA was not qualitatively but quantitatively characteristic of systemic lupus erythematosus (SLE) and that IgG anti-dsDNA levels correlated well with the disease activity.

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.

Diagnostic significance of antibody to native deoxyribonucleic acid in children with juvenile rheumatoid arthritis and other connective tissue diseases

Sera of children with juvenile rheumatoid arthritis and other connective tissue diseases were tested for antibodies to native DNA by a radiolabeled-binding assay. Normal values were obtained in 130 children with JRA, including 28 with uveitis and 14 with selective IgA deficiency. Normal values were also found in sera from children with dermatomyositis, scleroderma, polyarteritis, ankylosing spondylitis, and a variety of other nonconnective tissue diseases. The only sera with elevated DNA-binding assays were from children with systemic lupus erythematosus. On the basis of these data, increased levels of antibodies to native DNA distinguished patients with active SLE from children with JRA.

Analysis of DNA structure by hydroxyapatite columns and ethidium bromide fluorescence techniques. A comparative study and effect on DNA binding

Seven duplex DNA preparations have been structurally analyzed by hydroxyapatite column chromatography and an ethidium bromide fluorescence technique. Significant contamination of one preparation with single-stranded DNA was detected by hydroxyapatite column chromatography. Five of the other six preparations were found to contain significant single-stranded regions by the ethidium bromide fluorescence technique. Synthetic poly dAT was found to be duplex in structure. The presence of single-stranded regions considerably influenced DNA binding results in a radioimmunoassay.

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.

Central nervous system involvement in SLE. Diagnostic profile and clinical features

The clinical course and diagnostic profile of 13 patients with central nervous system involvement and systemic lupus erythematosus (CNS-SLE) are presented. The diagnostic yield for each procedure was measured as the precent abnormal: CSF total protein was 38%; increased CSF IgG 69%; decreased CSF hemolytic C4 10%; increased CSF anti-DNA 64%; electroencephalogram 80%; flow brain scan 50%; and static brain scan 0%. No single procedure was consistently abnormal, but the battery of tests provided a useful and specific CNS-SLE diagnostic profile.

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.

Pathways of complement activation in chronic discoid lupus: serologic and immunofluorescence studies

To assess the relative roles of the classic and alternative pathways of complement activation in chronic discoid lupus erythematosus (CDLE), serum levels of properdin, C3, and C4, and deposition of these proteins in the dermal-epidermal junction (DEJ) of 20 CDLE patients were compared to the findings in patients with clinically active and inactive SLE. Properdin was demonstrated in the DEJ of 10 of 14 (71%) histologically typical skin lesions from patients with CDLE, usually in association with deposits of immunoglobulin, C3, and C4. Properdin levels in CDLE patients were significantly increased (137 +/- 34%) (P less than 0.05) when compared to normal controls (101 +/- 18%) or to patients with clinically active SLE (89 +/- 32%). C3, C4, DNA-binding, and antinuclear antibody tests in CDLE were indistinguishable from those in normals, but significantly different from patients with active SLE (P less than 0.05). The complement profiles of patients with clinically inactive SLE resembled those of CDLE patients more closely than those of active SLE patients.

Antinuclear antibodies (ANA): immunologic and clinical significance

The methods currently used for the detection of ANA have been analyzed, with emphasis on their practical application to the diagnosis of the CTD. The use of the indirect IF-ANA test was recommended as a screening procedure to detect ANA. The need to standardize the technique using a single substrate and fluorescent conjugates with uniform F/P ratios was stressed. Most importantly, the value of titrating ANA for the diagnosis of the CTD was discussed. ANA titers higher than 1/500 are usually very significant clinically, often found in spontaneous or drug-induced SLE and few other CTD. The immunologic aspects of ANA and their potential value as aids in the diagnosis and management of the CTD were discussed. Anti-nDNA antibodies have been found to have a high degree of specificity for SLE and high titers of these antibodies correlate well with low levels of serum complement and severity of kidney involvement. The spectrum of ANA in the sera from patients with SLE has been expanded with the finding of anti-Sm antibodies which, when detected by gel precipitation with prototype serum, have been found so far only in SLE. Some of these antibodies have been found to have prognostic significance. Patients with MCTD and a group of patients with SLE have high titers of serum ANA with specificity for an RNase-sensitive component of ENA. The group of SLE patients defined by the presence of these antibodies (anti-Mo) have a better prognosis and in general develop only mild nephritis or have no kidney involvement at all. High titers of pure antinucleolar antibodies probably are found almost exclusively in the sera of patients with scleroderma. Some ANA have organ specificity, and GS-ANA have been found in all patients with Felty's syndrome and in a large proportion of patients with RA. One of the great advances in the field has been the recognition that ANA can be induced in the human and in experimental animals by the use of a number of therapeutic agents. Some of these agents can also induce a clinical picture resembling spontaneous SLE, though kidney involvement does not occur or is extremely mild. It is interesting that the whole spectrum of ANA can be found in drug-induced LE except anti-nDNA antibodies which have been associated to the pathogenesis of immune complex nephritis in spontaneous SLE. There is no doubt that research on ANA has contributed a great deal to the understanding of the CTD and will continue to be a valuable tool for the clinician and the investigator.

Double-stranded DNA-binding capacity of serum in acute and chronic liver disease

Serum antibodies to double-stranded 'native' DNA have been measured in acute and chronic liver diseases using the Farr technique. Elevated levels of DNA binding were found in all groups of patients, with the highest levels in acute viral hepatitis and lowest in primary biliary cirrhosis. All patients with hepatitis B surface antigen-positive chronic active hepatitis had elevated levels, hence persistent elevation of DNA binding after acute type B hepatitis might be an unfavourable prognostic marker indicating progression to chronic active hepatitis, DNA antibody levels will not offer diagnostic help in liver diseases, or help to follow the response of patients with 'lupoid' hepatitis to corticosteroid therapy. Production of DNA antibody may be a response to release of DNA from damaged hepatocytes.

In vitro demonstration of a particular affinity of glomerular basement membrane and collagen for DNA. A possible basis for a local formation of DNA-anti-DNA complexes in systemic lupus erythematosus

In vitro, collagen and collagen-like material in GBM, were demonstrated to have a particular high affinity for any DNA tested (mammalian, bacterial, viral, and plant). GBM fixed DNA 40-80 times more than HGG and BSA and 10-40 times more than bacterial LPS. GBM has a higher affinity for SSDNA than for DSDNA. This binding was inhibited at low pH, low ionic strength, and in the presence of anionic detergents, indicating that the highly negatively charged DNA may interact with the basic site on collagen or GBM by electrostatic forces. This interaction was competitively interfered with by DNA-binding proteins such as Clq. Complexes formed of DNA and anti-DNA antibodies did not exhibit the same binding property as free DNA. However, DNA which was already bound to GBM or to collagen could very efficiently bind anti-DNA antibodies and form immune complexes which would remain on these structures. The biological significance of the binding of DNA to GBM or to collagen should be particularly considered in relation to the pathogenesis of SLE. It is possible that DNA released from disrupted or degenerating cells would bind to surrounding collagen fibers or to basement membranes and then act as an immunoabsorbant for circulating anti-DNA antibodies. Some evidence for an in vivo binding of SSDNA to renal structures was obtained in mice treated with bacterial LPS 2 days before the injection of SSDNA.

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

Virtually all preparations of DNA used to detect antibody to native DNA (nDNA) by binding assays have been found to be subtly contaminated by single stranded DNA. Because recent DNA binding data have directly challenged the unique role previously attributed to these antibodies in systemic lupus erythematosus (SLE), resolution of the consequent ambiguity is of theoretical and practical importance. It is proposed that a synthetic nDNA molecule (dAT) might circumvent this difficulty by being antigenically equivalent to nDNA while, on theoretical grounds, lacking significant contamination with single stranded DNA or other cellular antigens. These expectations were generally confirmed by biochemical and immunological analyses. In clinical studies, sera from 124 pateints with SLE and from controls were examined for their ability to bind dAT. In contrast to results with KB binding, patients with non-SLE rheumatologic disorders were indistinguishable from normals by dAT binding. dAT binding was elevated in 85% of sera from SLE patients with clinically-judged active nephritis but in only 9% of those with inactive renal disease. Active non-renal disease, including cerebritis, was not associated with increased dAT binding. Individual non-lupus sera which bound increased amounts of KB DNA, failed to bind dAT. It is suggested that such binding resulted from contaminating non-nDNA antigens. When elevated, dAT binding, like KB binding, varied with disease activity and might thus be useful as a parameter thereof. In several patients elevated dAT binding led to the finding, on biopsy, of clinically silent, active, diffuse proliferative nephritis. It is concluded that use of synthetic nDNA antigens such as dAT may offer theoretical and practical advantages over naturally-derived preparations in detecting anti-nDNA, both clinically and for investigational purposes. Also, caution is urged in interpreting DNA binding data derived from incompletely characterized systems, particularly with regard to the occurrence of anti-nDNA antibodies in serum.