A new ELISA for the detection of double-stranded DNA antibodies

The accurate detection of antibodies to double-stranded DNA is important in the diagnosis and management of patients with systemic lupus erythematosus (SLE). We have developed an ELISA in which plasmid dsDNA is biotinylated and bound to streptavidin coated wells. The biotinylated DNA did not lose is antigenicity, and the DNA which bound to the plate remained double-stranded. Only small amounts of DNA were required to coat the plates, and binding was highly reproducible. After defining the normal range of the assay, sera from patients with various conditions were examined; 0 out of 97 controls were positive, 0 out of 36 patients with RA were positive, 0 out of 14 patients with scleroderma, and two out of 18 patients with chronic liver disease were positive. In contrast, 52% of unselected SLE patients were positive, and there was a good correlation between level of DNA antibodies and disease activity. Comparison of this assay with other DNA assays (the Farr, Millipore, filter, and a commercial ELISA) showed a high degree of correlation between this ELISA and each of the other assays. Furthermore, screening of randomly selected ANA positive patients with this assay failed to show a high false positive rate as has been reported with other anti-DNA ELISAs. This assay is simple to perform, requires small amounts of DNA to coat the plate, is highly reproducible, and is specific for IgG antibodies to dsDNA.