Antibody-nucleic acid complexes. Antigenic domains within nucleosides as defined by solid-phase immunoassay.

The usefulness of solid-phase immunoassays for the characterization of anti-nucleoside antibodies was investigated. Antibodies specific for guanosine (G), 7-methyl-guanosine (m7G), and cytidine (C) were obtained from the serum of rabbits immunized with nucleoside-KLH (keyhole limpet hemocyanin) conjugates. Solid-phase assays consisted of measuring the ability of these antibodies to be retained by microtiter wells containing immobilized nucleoside-BSA (bovine serum albumin) conjugates. Nucleosides employed as haptens included adenosine (A), N6-methyl-A (m6A), guanosine (G), N2,N2-dimethyl-G (m22G), 1-methyl-G (m1G), O6-methyl-G (m6G), 7-methyl-G (m7G), cytidine (C), 5-methyl-C (m5C), uridine (U), and ribothymidine (T). Spectral analysis of these conjugates revealed that 15-20 nucleosides were coupled to each BSA molecule. Quantitative information regarding the various reactions associated with these assays was obtained by employing antigen and antibody (IgG) preparations radiochemically labeled via reductive methylation using NaB3H4 and formaldehyde (specific activities 0.6-2.1 X 10(6) cpm/micrograms). Data obtained with 3H-labeled antigens indicated that the adsorption of all nucleoside-BSA conjugates was uniform and irreversible with respect to the assay conditions used. Assays designed to measure antibody binding in the presence of excess antigen revealed that (i) nonspecific binding to immobilized BSA was negligible, (ii) as little as 0.5 ng of bound antibody could be detected, (iii) antibody retention was directly proportional to antibody concentration, and (iv) each anti-nucleoside antibody cross-reacted to a considerable extent with nonhomologous haptens.(ABSTRACT TRUNCATED AT 250 WORDS)