Immunological detection of aflatoxin B1-DNA adducts formed in vivo.

Two monoclonal antibodies (6A10 and 12F5) were obtained after fusion of mouse P3X63-AG.8.653 myeloma cells with spleen cells isolated from BALB/c mice immunized with imidazole ring-opened aflatoxin B1 (AFB1)-DNA and characterized by competitive enzyme-linked immunosorbent assays. Both antibodies are highly specific for imidazole ring opened AFB1-DNA and show some cross-reactivity with AFB1-DNA and no cross-reactivity with 8,9-dihydro-8-(7-guanyl)-9-hydroxy-AFB1, AFB1 conjugated with bovine serum albumin, aflatoxin M1 conjugated with bovine serum albumin, AFB1, or aflatoxin G1. Antibody 6A10 was further characterized and showed no cross-reactivity with DNA modified by several other carcinogens. It could detect adducts with 4-fold higher sensitivity in highly modified DNA (2.5 adducts/100 nucleotides) than in low modified DNA (4 adducts/10(5) nucleotides). With low modified DNA the limit of sensitivity is 5 adducts/10(7) nucleotides. Antibody 6A10 reliably detected adducts formed in vivo in rats and mice treated with AFB1. In a pilot study, AFB1 adducts were detected in liver tissues from individuals living in areas with suspected exposure to AFB1. Monitoring adduct levels in human tissue may provide information not only on carcinogen exposure but also on the relationship among infection with hepatitis B virus, dietary exposure to aflatoxin B1, and liver cancer.