Specificity of anti-nucleoside antibodies in systemic lupus erythematosus

Impact of anti-peroxynitrite-damaged-thymidine-monophosphate antibodies on disease activity in patients with systemic lupus erythematosus

Present study probes the role of peroxynitrite (ONOO(-))-modified thymidine-5'-monophosphate (TMP) in SLE patients with different disease activity scores according to the SLE Disease Activity Index (SLEDAI). Serum analysis showed significant increased number of subjects positive for anti-ONOO(-)-TMP-protein antibodies in SLE patients with different SLEDAI scores. Interestingly, the levels of these antibodies were significantly higher among SLE patients, whose SLEDAI scores were ≥20. In addition, a significant correlation was observed between the levels of anti-ONOO(-)-TMP-protein antibodies and the SLEDAI score (r = 0.595, p < 0.0001). In short, this study shows a positive association between anti-ONOO(-)-TMP-protein antibodies and SLEDAI. The stronger response observed in patients with higher SLEDAI scores suggests that anti-ONOO(-)-TMP-protein antibodies may be useful in evaluating the progression of SLE and in elucidating the mechanisms of disease pathogenesis.

Preferential recognition of peroxynitrite damaged thymidine-monophosphate by anti-DNA autoantibodies in systemic lupus erythematosus

This study was undertaken to investigate the role of peroxynitrite (ONOO(-)) modified thymine-5'-monophosphate (TMP) in the generation of anti-DNA autoantibodies in patients with systemic lupus erythematosus (SLE). TMP was exposed to ONOO(-) in vitro and challenged in vivo. TMP and ONOO(-)-modified-TMP were found to be nonimmunogenic in rabbits. TMP-linked-BSA and ONOO(-)-modified-TMP-BSA induced high titer antibodies. Induced antibodies against ONOO(-)-TMP-BSA show crossreactions with nucleic acids conformers. A high degree of specific binding by SLE autoantibodies with ONOO(-)-TMP-BSA was observed. Our novel results provide an important insight into the immunological basis of anti-DNA autoantibodies generation in SLE.

Serum antiguanosine antibodies as a marker for SLE disease activity and pathogen potential

BACKGROUND

This article reviews research conducted on the immunogenicity of the nucleosides of DNA, especially guanosine, the most immunologically active nucleoside. Discussed is the relationship between circulating antibodies to guanosine, their potential role in SLE disease activity, the binding properties of monoclonal antiguanosine antibody (4H2) compared to polyclonal antiguanosine antibodies in humans with SLE, cell membrane penetration by these antibodies and their interference with signal transduction possibly related to their binding to mitochondria and their apparent GTPase activity.

METHODS

Enzyme-linked immunosorbent assay methodology was used to show clinical relationships between antiguanosine antibody levels and disease activity in SLE. These results are discussed along with methods of detecting cell penetration by this antibody using special staining techniques, laser-scanning microscope detection of mitochondrial localization, and interference of cAMP and pKA production/activation. Additionally, there is some discussion regarding the assay used to detect enzymatic activity of antiguanosine antibodies.

RESULTS

Enhanced circulating levels of antiguanosine antibodies in patients with SLE correlate closely with SLE disease activity. Other factors are discussed that support the pathogenic potential of these antibodies, including their ability to penetrate lymphocytes, bind to mitochondria, inactivate mitochondrial function, interfere with signal transduction, and their potential enzymatically activity.

CONCLUSIONS

Antiguanosine antibodies correlate with SLE disease activity and may be pathogenically important in SLE by interfering with signal transduction, inactivating mitochondrial and cell function in patients with SLE.

Circulating antibodies to guanosine in systemic lupus erythematosus: correlation with nephritis and polyserositis by acute and longitudinal analyses

Systemic lupus erythematosus (SLE) is characterized by autoantibodies, including antibodies to the nucleosides of DNA. Guanosine is the most immunogenic nucleoside. In this study serum antiguanosine antibody levels were compared with disease activity, determined by their SLEDI score, in 86 patients with SLE. Sera from these patients were tested, by ELISA, for autoantibodies to guanosine, single-stranded DNA (ssDNA), and double-stranded DNA (dsDNA). Anti-double-stranded DNA levels were also measured by RIA. Resultant values from these assays were correlated with SLE disease activity, and compared with specific features of SLE. The strongest correlation was higher levels of antiguanosine antibodies in patients with active lupus nephritis and polyserositis compared to patients with inactive disease (P < 0.0001). Antiguanosine levels also correlated with arthritis (P < 0.006), CNS lupus (P < 0.005), and hematologic manifestations of SLE (P < 0.002). To test the validity of this association in chronic SLE, serum antiguanosine antibodies were measured in patients with SLE at various phases of disease activity. Twelve patients with SLE had serum samples drawn at active, active-improved, and inactive phases over a 3-7 y period. Differences were significant for serum antiguanosine antibodies in the active group compared to the inactive group (P < 0.05) and the active vs the active-improved group (P < 0.02), unlike those for dsDNA and ssDNA by ELISA or RIA. Antiguanosine antibodies correlated more closely with disease activity in SLE patients in this longitudinal study than either anti-dsDNA or ssDNA antibodies. Thus, antibodies to guanosine correlated as well or better with disease activity than the other anti-DNA antibodies measured and should be considered to contribute to the pathology of SLE, especially lupus nephritis.

Apheresis enhances the selective removal of antinuclear antibodies in systemic lupus erythematosus

Apheresis suppresses clinical manifestations of lupus and reduces levels of antinuclear antibodies implicated in the pathogenesis of systemic lupus erythematosus (SLE). It is not known, however, if reduced levels of antinuclear antibodies are due to nonspecific removal, or specific mechanisms associated with decreased production, or enhanced clearance from the circulation. In order to distinguish between specific and nonspecific effects of apheresis on antinuclear antibodies in SLE, we compared plasma levels of IgG antibodies to DNA and IgG antibodies to microbial antigens in 13 SLE patients before and after apheresis. Although apheresis lowered plasma levels of IgG (21% mean reduction), there was a disproportionate reduction in IgG antibodies to DNA (42% mean reduction, p less than 0.13). In marked contrast, reduction in antibodies to microbial antigens did not exceed those of plasma IgG. A rapid rebound of serum anti-DNA antibodies following apheresis in certain SLE patients suggests that the selective reduction in anti-DNA antibodies is due to enhanced clearance from the circulation rather than decreased production. These results indicate that apheresis enhances selective removal of antinuclear antibodies in some patients with SLE.

Enhanced binding of lupus sera to the polyamine-induced left-handed Z-DNA form of polynucleotides

The natural polyamines putrescine, spermidine, and spermine are small polyvalent cations present in all living cells. Spermidine and spermine are excellent promoters of left-handed Z-DNA, an immunogenic form of DNA that binds readily with anti-DNA antibodies in the sera of patients with systemic lupus erythematosus (SLE). We studied the binding of a panel of 16 SLE sera to poly(dA-dC).poly(dG-dT) and poly(dG-m5dC).poly(dG-m5dC) in the presence and absence of spermidine and spermine using an enzyme-linked immunosorbent assay. The majority of SLE sera showed a 50-150% mean increase in optical density values when incubated with the polynucleotides and either 0.25 mM spermidine or 0.025 mM spermine than when incubated with the polynucleotides alone. Under these conditions, the polynucleotides assumed the Z-DNA form. Since polyamines are ubiquitous cellular components and since potential Z-DNA-forming alternating purine-pyrimidine sequences are widely dispersed in native DNA, the increased binding of SLE sera to polyamine-induced Z-DNA suggests a pathogenic role for these compounds in SLE.

Antibody-nucleic acid complexes. Oligo(dG)n and -(dT)n specificities associated with anti-DNA antibodies from autoimmune MRL mice

The specificity of anti-DNA antibodies in the sera of unimmunized autoimmune MRL mice was initially assessed via an enzyme-linked immunosorbent assay (ELISA). Antibody binding profiles to a panel of immobilized antigens (AMP-, GMP-, CMP-, UMP-, and TMP-BSA, ss- and dsDNA) demonstrated high levels of immunoglobulins reacting with GMP and ssDNA and intermediate levels with AMP, TMP, and dsDNA. Fractionation of serum anti-DNA antibodies into subsets on the basis of their binding to GMP- and TMP-agarose indicated that the resulting GMP- or TMP-reactive antibodies bound to their homologous nucleotides and ssDNA. Competition-inhibition studies with soluble mono-, oligo-, and polynucleotides revealed that GMP- and TMP-reactive antibodies were highly specific for oligo(dG)n and -(dT)n sequences, respectively. Whereas the relative affinity of TMP-reactive autoantibodies to oligo(dT)n increased with oligonucleotide length (n = 2, 4, 6, 8, 10, 15), GMP-reactive antibodies preferentially recognized oligo(dG)10 (Ka congruent to 1 x 10(7) M-1). While neither antibody recognized oligo(dA)8 and -(dC)8 competitors, mixed-base oligonucleotides were inhibitory at concentrations approximately 10-fold greater than similarly sized oligo(dG)n and -(dT)n sequences. Similar characterizations of both pooled and individual MRL sera indicated that anti-DNA antibodies represent 8-10% of the total serum IgG. More importantly, GMP-reactive autoantibodies predominated and accounted for 60-70% of the entire unbound anti-DNA antibody population.

TMP-reactive autoantibodies in human SLE sera demonstrate thymine-dependent oligonucleotide specificity

Autoantibodies present in the sera of lupus patients and specific for single-stranded (ss) DNA were fractionated into subsets based upon their reactivity towards 5' nucleotide haptens. As evaluated by ELISA testing, antibodies retained by TMP-agarose bound to TMP-BSA and ssDNA but not to other nucleotide-BSA conjugates or to double-stranded (ds) DNA. Competition-inhibition studies further revealed that TMP-enriched oligo- and polynucleotides were the preferred antigens for these affinity purified antibodies. Similar assays with sequence- or size- defined oligonucleotides further implied that those oligonucleotides comprised entirely of TMP residues were most antigenic and that antigenicity increased with size (length). These results document the existence of a TMP-dependent oligonucleotide specificity among a diverse population of autoanti-ssDNA antibodies.

Drug-induced rheumatic syndromes. Diagnosis, clinical features and management

In order to avoid inappropriate therapy and prolonged morbidity, it is important to recognise when a patient's rheumatic complaints are due to drugs. However, this is often difficult because of the large number of drugs that have been implicated and the diversity of clinical presentations. Arthropathy may be seen with several different syndromes, including drug-induced lupus erythematosus (DILE), serum sickness and gout. The most widely reported of these is DILE, which usually develops after some months or even years of drug therapy. While many authors do not specifically require their presence for the diagnosis of DILE, antinuclear antibodies have been detected in the great majority of reported patients with DILE, whatever the causative drug. In contrast, patients who develop arthropathy soon after commencing a drug rarely have antinuclear antibodies and appear to be distinct from patients with DILE. Apart from arthropathy, a number of other syndromes that appear to have an immunological basis may be induced by drugs. Cutaneous vasculitis is not uncommon and drugs are frequently considered to be the aetiological factor. Whether drugs may cause larger vessel systemic vasculitis is less certain. Rarely, polymyositis and scleroderma-like syndromes have been associated with drug therapy. Corticosteroid-induced osteoporosis is a complication of all the corticosteroid preparations that are widely used at present. However, the development of deflazacort, a so-called 'bone-sparing' steroid, has raised the possibility that the effect of corticosteroids on bone may be separable, at least in part, from the other actions of these drugs. Data have been conflicting with regard to whether there is a 'safe' dose of corticosteroid. Similarly, it is unclear whether prophylactic therapy with agents such as calcium, fluoride and vitamin D is beneficial. Nonetheless, recent findings suggest that approaches will be developed to minimise the risk of osteoporosis in patients who require corticosteroids. There are a number of other ways in which drugs may affect bones. Osteomalacia is a well-known but uncommon complication of treatment with anticonvulsants and occasionally other drugs. The mechanism probably relates to the induction of hepatic enzymes and the consequent increased metabolism of vitamin D in patients with borderline levels initially. Osteosclerosis may also result from drug therapy; usually with fluoride or retinol (vitamin A) and its analogues. With continued research, the true spectrum of drug-induced rheumatic syndromes should become more clearly defined.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunochemistry of DNA

Since the first reports of anti-DNA antibodies in sera of patients with systemic lupus erythematosus (SLE) in 1957, studies of nucleic acid immunochemistry have grown in two directions. One has been the analysis of the specificity, the nature and the origins of these autoantibodies. The second has been exploration of anti-nucleic acid antibodies that can be induced experimentally, their specificities, and their application as biochemical reagents. Although the properties of autoantibodies and experimentally induced antibodies differ in certain respects, these two lines of research are complementary and provide important information for each other. For example, the production of autoantibodies by adjuvant-stimulated B cells yields a background that has to be considered in evaluating the specificity of weak responses to experimental nucleic acid immunogens: in turn, the possibilities and limitations of experimental immunization should be considered in evaluating possible stimuli for autoantibody production. Several aspects of nucleic acid immunochemistry have been described and evaluated in previous reviews. Following some general statements of historical perspective, this review will emphasize questions addressed and findings of about the last five years.

DNA is a potent immunogen for spleen cells and for guanosine-binding B lymphocytes

The production of antibodies to nucleic acids, and in particular to DNA, has been implicated in the pathogenesis of autoimmune diseases such as systemic lupus erythematosus (SLE). However, little is known about the conditions under which DNA is immunogenic, particularly in well-characterized in vitro systems. Therefore, we examined whether a source of cytokines, in conjunction with D-DNA, permitted a polyclonal or antigen-specific B-cell response. Spleen cells from MRL +/+ SLE-prone mice were incubated with supernatant from concanavalin A-stimulated spleen cells (Con A SN, a source of cytokines) and D-DNA. A potent antibody response developed to guanosine (GU) and D-DNA but not to fluorescein (FL), using as little as 10 ng D-DNA in conjunction with Con A SN. In order to further examine the cellular requirements for D-DNA to be immunogenic, populations of B cells which bound GU (an immunodominant epitope of DNA) or an irrelevant FL-binding population were purified and incubated with DNA and Con A SN. Interestingly, GU-binding, but not FL-binding B cells could be triggered by D-DNA derived from calf thymus, a result suggesting that DNA was not acting simply as a polyclonal B-cell activator. D-DNA optimally triggered GU+ B cells within a narrow dose range similar to many thymus-independent Type II antigens with repetitive determinants. If DNA were truly an autoantigen, then DNA derived from the MRL +/+ mouse should be capable of triggering GU-binding B cells. When this hypothesis was tested, D-DNA, but not N-DNA, functioned as a potent immunogen. These experiments document the ability of DNA to act as a specific immunogen and suggest that, under appropriate conditions, nucleic acid may induce autoantibody production in vivo.

A method for the isolation of autoreactive B cells

A technique was developed to isolate a population of autoreactive B cells from both normal and autoimmune-prone mice. Modifications of the procedure of Haas and Layton (1975) permitted coupling the nucleoside guanosine (GU) to gelatin and subsequently coating this matrix onto tissue culture dishes. After incubation on GU-gelatin, B lymphocytes specific for GU could be isolated. Specificity was demonstrated by rosetting techniques as well as by inhibition of binding to GU-gelatin by GU-containing conjugates. Isolated GU+ B cells were triggerable with GU-Brucella abortus antigen as well as LPS, to secrete anti-GU antibody in a direct plaque assay. The DNA-binding activity of the antibody was assessed using hapten inhibition of anti-GU PFC. Both native (N) DNA as well as denatured (D) DNA inhibited plaque formation. DNA-binding ability of secreted anti-GU antibody was also demonstrated by plaque formation using D-DNA-coated erythrocytes as target cells. Isolated GU+ B cells that are triggerable with antigen will be important in investigating growth, triggering and tolerance defects in a specific population of autoreactive B cells. In addition autoreactive B cells can now be compared to nonautoreactive hapten-specific lymphocytes. These properties as well as others can now be studied in controlled systems free from the regulatory effects of murine T or accessory cells.

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.

Detection of human autoantibodies specific for 5'-m7GMP and m7G(5')ppp(5')N

An enzyme-linked immunosorbent assay was utilized for the detection of spontaneously occurring antibodies with apparent specificities for m7G, 5'-m7GMP, and m7G(5')ppp(5')C. From the sera of 50 patients containing anti-nuclear antibodies, 48 (96%) possessed antibodies which bound to one or more immobilized nucleoside-BSA antigens (A-, G-, C-, U-, and T-BSA). Additionally, 8 (16%) of these sera contained immunoglobulins that reacted with m7G-BSA antigen. In these latter sera, soluble competitors such as m7G, 5'm7GMP, and m7G(5')ppp(5')C (but not 5'-AMP, -GMP, -CMP, -UMP, and -TMP or m1G and m22G) effectively inhibited antibody-binding to immobilized m7G-BSA. These results indicate the existence of spontaneously occurring anti-m7G antibodies in autoimmune diseases which are distinct from anti-G antibody populations.

Origins of anti-DNA autoantibodies

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Antibodies to guanylic acid: fractionation and specificities

Guanylic-acid-specific antibodies were elicited in rabbits, using as immunogen pG linked through 5'-phosphate to thyroglobulin. Specificity and affinity of antibodies to nucleotides, nucleosides, DNA, and RNA were studied by their binding to radioactive ligands and competition experiments. Guanylic-acid-specific antibodies do not bind to deoxyguanylic acid and have an average association constant of 10(7) M-1 at 4 degrees C. Binding of the antibodies to 3H-RNA is G-specific. The antibodies do not bind to 32P-ssDNA or 32P-dsDNA. The pG-specific antibodies could be separated into different fractions by affinity chromatography. These fractions, though specific to pG, differ in their cross-reactivities to nucleosides and nucleotides.

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.