Hydroxyl radical modification of human serum albumin generated cross reactive antibodies

Abstract

Hydroxyl radical-mediated in vitro modification of human serum albumin (HSA) showed 59.2% hyperchromicity at λ_max, 30% loss of alpha helical structure and 71.4% loss of tryptophan fluorescence. The reactive oxygen species (ROS)-modified HSA was highly immunogenic in rabbits as compare to native HSA. The antibody binding was inhibited to the extent of 97% with the immunogen as inhibitor, indicating the induction of immunogen specific antibodies. Experimentally induced antibodies against modified HSA exhibited diverse antigen binding characteristics. Native plasmid DNA, ROS-modified plasmid DNA and ROS-chromatin were found to be an effective inhibitor of induced antibody–immunogen interaction. Induced antibodies against native HSA showed negligible binding to the above mentioned nucleic acid antigens. Band shift assay reiterated the recognition towards nucleic acid antigens. Thus, the induced antibodies against ^√OH modified HSA resembled the diverse antigen-binding characteristics of naturally occurring systemic lupus erythematosus (SLE) anti-DNA autoantibodies.

• HSA
• oxygen free radicals
• ROS–HSA
• ^√OH radical
• cross-reactive-antibodies
• lupus

Acknowledgements

The authors are grateful to Dr Rizwan Hasan Khan, Interdisciplinary Biotechnology Unit, A.M.U., Aligarh, for providing some laboratory facilities.