Thymine and guanine base specificity of human myeloma proteins with anti-DNA activity

Detection of autoimmune antibodies in localized scleroderma by synthetic oligonucleotide antigens

In this study, we developed a series of synthetic oligonucleotides that allowed us to investigate the details on the antigen recognition by autoimmune antibodies in localized scleroderma subjects. Besides dramatically improved analytical specificity of the assay, our data suggests a potential linking for antibodies to DNA to the biological status of disease state in localized scleroderma. Moreover, introducing chemical modifications into short synthetic deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) molecules completely changed the binding titers of corresponding antibodies and their clinical relevance. The strongest observed effect was registered for the localized scleroderma skin damage index (LoSDI) on the IgG antibodies to TC dinucleotide-rich double-stranded antigen (p < 0.001). In addition to providing valuable tools for diagnosis of clinically relevant biomarkers, we believe that this work opens up new opportunities for research on antibodies to nucleic acids in localized scleroderma and other autoimmune diseases.

Effects of intravenous immunoglobulin on alpha synuclein aggregation and neurotoxicity

α-Synuclein is thought to contribute to the pathogenesis of Parkinson's disease (PD). It is the main protein in Lewy bodies, the pathognomonic inclusion bodies in the PD substantia nigra, and mutations which increase its aggregation and/or expression are associated with familial early-onset parkinsonism. Soluble oligomers are considered to be α-synuclein's most neurotoxic conformation. We previously reported that intravenous immunoglobulin (IVIG) products contain specific antibodies to α-synuclein which do not prevent development of four-day α-synuclein oligomers. The objective of this study was to further examine IVIG's effects on α-synuclein's aggregation and neurotoxicity. The IVIG product Gammagard (Baxter Healthcare) did not prevent the development of nine-day α-synuclein oligomers, nor did it degrade preformed oligomers, as shown by western blots performed on gels run under reducing/denaturing conditions and native gels. In western blots of native gels, an additional low molecular weight band (~22 kDa) was detected in α-synuclein incubated for four days in Gammagard, but not in Gammagard alone. No significant differences were found for Thioflavin-T reactivity between α-synuclein amorphous aggregates grown in Gammagard vs. those grown in phosphate-buffered saline. Gammagard partially protected SK-N-BE(2)M17 human neuroblastoma cells against α-synuclein oligomer toxicity (p = 0.007 vs. protective effects of normal human IgG). These findings suggest that although IVIG does not prevent α-synuclein aggregation, it still may reduce α-synuclein neurotoxicity through an unknown mechanism.

Polydeoxyribonucleotide C photoconjugated with lysine or arginine present unique epitopes for human anti-DNA autoantibodies

Studies have been carried out to synthesize and characterize the photoconjugates between positively charged amino acids (lysine and arginine) and the polydeoxyribonucleotide C [poly(dC)]. Poly(dC) was covalently crosslinked with lysine or arginine under ultraviolet light. Both lysine and arginine were found covalently photoconjugated to poly(dC), resulting in the formation of photoadduct. Photoaddition of lysine or arginine to poly(dC) rendered them thermodynamically more stable than their native form. A strong recognition of photoadducts was observed with anti-DNA autoantobodies found in the sera of systemic lupus erythematosus (SLE) patients. Poly(dC)-lysine was recognized more strongly than poly(dC)-argine photoadduct. Poly(dC)-lysine photoadduct appears to provide an immunodominant epitope for SLE autoantibody recognition. The result suggests for the possible involvement of these photoadducts as a potential trigger for anti-DNA autoantibody production.

Hydroxyl radical modification of polyguanylic acid: role of modified guanine in circulating SLE anti-DNA autoantibodies

The hydroxyl radical generated by UV irradiation of hydrogen peroxide cause an extensive damage to guanine residues of ribohomopolymer, polyguanylic acid, poly (G) as investigated by spectrophotometric measurements, agarose gel electrophoresis, Sephadex G-200 gel filtration and DEAE Sephadex A-25 column chromatography. Native and ROS-poly (G) were highly immunogenic inducing high titre antibodies in rabbits. The antibodies showed wide range of cross reactivity with various synthetic polynucleotides exhibiting B-, A-, and allied conformations. The diverse antigen binding characteristics of the induced antibodies resembles to those of naturally occurring lupus anti-DNA autoantibodies. Sera from various SLE patients showed preferential binding to ROS-poly (G) than native poly (G), indicating that oxidatively modified guanine residues are better recognised. The significance of these findings in the induction of SLE anti-DNA autoantibodies by oxygen free radicals modified guanine residues in DNA has been discussed.

Antigenicity of poly(I) and ROS-poly(I) and their recognition of human anti-DNA autoantibodies

The effect of hydroxyl radicals on polyinosinic acid [poly(I)] was studied. Strand breaks, base alteration and a decrease in absorbance at 248 nm (lambda max) were observed upon *OH modification of poly(I). The broad antigen specificity of the induced anti-poly(I) and anti-ROS-poly(I) antibodies showed diverse antigen binding characteristics similar to those of SLE autoantibodies. Recognition of both poly(I) and ROS-poly(I) by human SLE anti-DNA autoantibodies was observed. The possible significance of these findings in the etiology of SLE has been discussed.

Cationic myeloma M-components frequently show cross-reacting anti-DNA, Anti-F(ab')2 and anti-nucleosome specificities

134 cationic human IgG myeloma proteins were studied for expression of anti-DNA Idiotypic markers. 64 were studied for 16/6, F4, 3I, and 8.12, and 70 for expression of F4 and 3I. 31.3% showed at least one anti-DNA Id marker and many cationic myelomas were also positive for anti-DNA ELISA reactivity as well as anti-F(ab')2. Five M-components showed anti-nucleosome reactivity and one without detectable anti-DNA Id markers showed very strong anti-nucleosome antibody which was also inhibited by DNA and Sm antigens. Anti-idiotypic antisera produced either against Id(+) anti-DNA reactive M components or F(ab')2 fragments of affinity purified SLE IgG anti-DNA showed preferential cross-reactive idiotype reactivity between Id(+) anti-DNA reactive M components. Our findings indicate that human IgG monoclonal proteins positive for several common anti-DNA Ids and possessing anti-DNA ELISA reactivity, can serve as models for SLE Id marker antigens and as a source to prepare anti-Ids from IVIG.

Epitope complementarity and idiotypic interactions: a study of idiotypic-like interactions between anti-cytidine and anti-guanosine A/J mouse monoclonal antibodies--I. Characterization of these interactions

Idiotypic-like interactions between mAbs directed against cytidine (Cyd) or guanosine (Guo) nucleosides were characterized. These mAbs, Cyd-1 (IgG2b, kappa), Guo-1 (IgG1, kappa) and Guo-2 (IgG1, kappa) were derived from splenocytes of A/J mice immunized with Cyd-KLH or Guo-KLH and recognized the nucleoside base moieties involved in hydrogen bonding. The interactions between Guo-1 or Guo-2 and Cyd-1 involved cross-reactive or distinct-but-neighboring paratope-associated idiotopes. These interactions were characterized by KD values of 4.6 x 10(-6) and 1.8 x 10(-6)M, respectively. The three anti-nucleoside mAbs exhibited Ab2 beta properties and manifested epibody (Ab2 epsilon) activity towards ssDNA. We compared these idiotypic-like reactivities with the anti-idiotypic activity of an intentionally induced IgG1, kappa anti-idiotype mAb prepared with splenocytes from A/J mice immunized with Cyd-1. This Ab2 antibody which bound to Cyd-1 with a KD of 1.1 x 10(-9) M, manifested an Ab2 gamma activity, i.e. it recognized a paratope-associated idiotope on Cyd-1 without exhibiting Ab2 beta properties. In addition, the anti-(Cyd-1) completely inhibited (Cyd-1)-(Guo-1) and (Cyd-1)-(Guo-2) interactions.

Recognition of oxidized DNA bases by sera of patients with inflammatory diseases

Chronic inflammatory conditions result from or contribute to many diseases. Prominent among them is systemic lupus erythematosus (SLE). Sera of SLE patients contain an array of various auto-antibodies (Ab), including antinuclear Ab of unknown etiologies. The most puzzling is formation of Ab directed against autologous DNA. Our hypothesis was that increased oxidant production causes oxidation of DNA bases, which provide antigenic determinants that elicit antioxidized DNA Ab. To test this hypothesis, we used oxidized DNA nucleoside (5-hydroxymethyl-2'-deoxyuridine [HMdU]) conjugated to bovine serum albumin (HMdU-BSA) as the antigen. The results of the enzyme-linked immunosorbent assay showed that these Abs are sensitively detectable in SLE sera and sera of various other inflammatory autoimmune diseases. The titers of anti-HMdU Ab were significantly higher (p < .01) than those present in the control sera. Anti-HMdU Ab were predominantly of the IgM isotype, with low levels of IgG and no IgA. Anti-HMdU Ab bound to the HMdU-BSA-coated wells in a concentration- and time-dependent manner. That binding was inhibited by HMdU-BSA and to a lesser extent by thymidine-BSA, a normal nucleoside conjugate. The specific binding appears to be inversely related to the age of the patients, but no significant differences were observed between the sexes of the same age.

Enhanced antibody titers to an oxidized DNA base in inflammatory and neoplastic diseases

Reactive oxygen species (ROS) produced by phagocytic cells induce oxidative stress during chronic inflammation. ROS play a role in the pathogenesis of a broad range of diseases including autoimmune, cardiac and neoplastic abnormalities. We found that sera of patients with a variety of inflammatory dermatoses contain elevated levels of antibodies (Ab) binding to an oxidized DNA base derivative, 5-hydroxymethyl-2'deoxyuridine (HMdU) coupled to bovine serum albumin, as determined by the enzyme-linked immunosorbent assay. Patients with immune complex diseases and a history of neoplasm elaborated the highest titers of anti-HMdU Ab. Titers from sera of psoriatic subjects were lower than from the aforementioned groups but were still significantly elevated (p < 0.001) above those of healthy controls. Treatment of inflammatory dermatoses with systemic antiinflammatory and cytotoxic drugs significantly lowered the titers [p < 0.005 (immune complex) or p < 0.001 (psoriasis and neoplastic) diseases], suggesting that this assay may be of value in monitoring the response to therapy in these diseases.

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.

Immunologic tolerance to DNA in B cell lines from both normal and autoimmune mice

We examine whether B cell lines enriched for DNA specificity from either autoimmune (BWF1) or normal mice (Balb/c) can be rendered unresponsive to autoantigen in terms of the specific suppression of direct antibody-forming cells to DNA. These B cell lines were both Lyt-1 positive and negative. Preincubation with oligonucleotide, covalently linked to mouse gamma-globulin, specifically suppressed the antigen-driven response elicited by DNA horse red blood cells in B cell lines from both strains of mice. There is a 5-fold difference in susceptibility to DNA-specific tolerance induction between B cell lines of BWF1 and Balb/c mice. Thus, B cells from autoimmune mice do not appear to have an inherent absolute defect in being rendered tolerant to autoantigen, but are relatively less susceptible to DNA-specific tolerance than nonautoimmune cell lines.

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.

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.