DETECTION OF OXIDATIVE DNA-DAMAGE BY A MONOCLONAL-ANTIBODY - ROLE OF LYSYL RESIDUES IN ANTIGEN-BINDING

Hydroxyl radical, a prominent entity of reactive oxygen species, is kn own to modify cellular DNA and has been implicated in several human di seases. A previously described monoclonal antibody (Mab) against react ive oxygen species-modified DNA (ROS-DNA), which preferentially recogn izes ROS-modified epitopes on DNA, was used in this study. The E-amino groups of lysine of the Mab were modified to study the role of these residues in Mab binding to ROS-DNA. The results demonstrate that modif ication of lysyl residues paralleled loss in Mab binding to ROS-DNA to the extent of 73%, suggesting the probable role of these positively c harged amino acid residues in the complementarily determining regions of the Mab, The Mab was also used as an immunochemical probe to detect oxidative DNA damage in vivo in SLE. The Mab distinctly recognized fi ve DNA samples out of eight from SLE patients and gave maximum inhibit ions of 57, 58, 63, 64 and 70% in inhibition assay, while not reacting with DNA from normal, healthy population which served as negative con trol. High recognition of DNA isolates from SLE patients by the Mab ha ving preferential binding to ROS-modified epitopes indicates increased oxidative stress in these patients leading to DNA damage which may co ntribute to the induction of antibodies cross-reacting with native DNA (nDNA). (C) 1998 Elsevier Science B.V. All rights reserved.