Antibodies specific to two deoxyribotrinucleotide sequences

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.

The RNA binding subset of adenosine antibodies

Hapten specific antibodies were elicited against adenosine-BSA conjugate (Ado-BSA) in rats. By radiohapten assay, two major populations of hapten specific antibodies were identified. They were directed against either adenosine trialcohol (Aox-red) or morpholino-adenosine (Morph-Ade). The association constant (Ka) for the 3H-Aox-red binding population was determined to be 1.02 X 10(7) M-1. Majority of the Aox-red specific antibodies were cross-reactive with Morph-Ade, but they did not cross-react at all with adenosine(A) or deoxyadenosine (dA). 3H-A binding subsets were actually Morph-Ade specific and constitute less than 10% of the hapten specific antibodies. The Ka value for the 3H-A binding was determined to be 4.5 X 10(6) M-1. A very minor and highly cross-reactive subset of Morph-Ade specific antibodies participate in RNA binding. Though a larger proportion of Morph-Ade specific antibodies interact with 3H-A, only a fraction of them bind to RNA. The extreme cross-reactivity and hence, the highly adaptive nature of the binding sites of the antibodies interacting with RNA, might be a stringent requirement for recognising adenine residues of nucleic acids in solution.

Purification of antibodies specific to a dinucleotide using the hapten bound to DEAE cellulose as an affinity column

The dinucleotide dpTpA held electrostatically on DEAE cellulose was used as an affinity column for the purification of dpTpA specific antibodies. Chromatography of the gamma-globulin fraction from dpTpA specific antisera on this column resulted in the retention of dpTpA specific antibodies which were later eluted along with the bound dpTpA using 1M NaCl. Dextran coated charcoal was the method of choice for the dissociation and removal of dpTpA bound to the antibodies. This method may extend itself to the purification of antibodies specific for other oligonucleotides.

Antibodies to DNA

Antibodies that recognize specific conformational variations of DNA structure provide sensitive reagents for testing the extent to which such conformational heterogeneity occurs in nature. A most dramatic recent example has been the development and application of antibodies to left-handed Z-DNA. They provided the first identification of Z-DNA in fixed nuclei and chromosomes, and of DNA sequences that form Z-DNA under the influence of supercoiling. Antibodies have also been induced by chemically modified DNA and by synthetic polydeoxyribonucleotides that differ from the average B-DNA structure. These antibodies recognize only the features that differ from native DNA. In most experiments, native DNA itself is not immunogenic. Antibodies that do react with native DNA occur in sera of patients with autoimmune disease, but even monoclonal anti-DNA autoantibodies usually react with other polynucleotides as well. Anti-DNA antibodies, especially those of monoclonal origin, provide a model for the study of protein-nucleic acid recognition.

Base specific binding of deoxyguanylate and deoxycytidylate antibodies to double stranded DNA

Antibodies raised in rabbits against deoxyguanylate and deoxycytidylate bind to 3H-lambda double stranded DNA and the binding is base specific. The concentrations of antibody populations that bind to double stranded DNA are much less than those binding to denatured DNA. Due to their low concentrations, these antibodies were not detected in earlier studies. These antibodies are expected to be useful to probe the conformational flexibilities of double stranded DNAs.

Antibodies elicited by defined oligodeoxyribonucleotide sequences

Antibodies to the oligodeoxyribonucleotides d(pT)3, d(pT)4, d(pT)6 and d(pA-A-T-T) were elicited in rabbits by immunization with electrostatic complexes of the respective haptens with methylated bovine serum albumin (MBSA). The antisera were assayed by complement fixation using denatured DNA's of various sources as antigens. The specificities of the antibodies were determined by estimating the inhibition of the complement fixation reaction by defined oligodeoxyribonucleotides. The antibodies were shown to be specific for the sequence of the oligode-oxyribonucleotides or parts of it.

Formation and characterization of antibody against 2'-(5"-phosphoribosyl)-5' AMP, the monomer form of poly(adenosine diphosphate ribose)

Specific antibody against 2'-(5"-phosphoribosyl)-5'AMP (PR-AMP), a monomer of poly(adenosine diphosphate ribose) (poly(ADP-Rib)), was produced by immunizing a rabbit with PR-AMP coupled to bovine serum albumin (BSA). Antibody against PR-AMP was purified 53-fold from serum by (NH4) 2SO4 precipitation, and BSA-Sepharose 4B, DEAE-cellulose and (PR-AMP)-BSA-Sepharose 4B column chromatographies. Inhibition experiments show that the adenine ring, 5'-phosphate residue and ribose-ribose bond of PR-AMP were essential for the antigenic determinant of PR-AMP. Anti PR-AMP antibody bound, not only with PR-AMP, but also with poly(ADP-Rib) of various chain lengths, while anti poly(ADP-Rib) antibody bound with poly(ADP-Rib) but not with PR-AMP.