Ultrasensitive enzymatic radioimmunoassay (USERIA) detects femtomoles of acetylaminofluorene-DNA adducts.

USERIA is a modification of radioimmunoassay and enzyme-liked immunosorbent assay. When compared to these assays, USERIA is 60- and 10-fold, respectively, more sensitive for the detection of adducts in DNA modified by the chemical carcinogen, 2-acetylaminofluorene (AAF). The specific antigen-antibody reaction is enzymatically amplified by an anti-IgG alkaline phosphatase conjugate which converts the substrate, [3H]adenosine-5'-monophosphate, to [3H]adenosine. As few as 2 fmol of AAF-DNA adducts can be detected by a competitive USERIA assay and less than 3 fmol of the specific adduct, N-(deoxyguanosine-8-yl)-AAF, can be detected using a non-competitive USERIA approach. The sensitivity of USERIA should aid efforts to measure carcinogen-DNA adducts in biological specimen samples from humans and experimental animals.