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, AFB₁conjugated with bovine serum albumin, aflatoxin M₁conjugated 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^s nucleotides). With low modified DNA the limit of sensitivity is 5 adducts/10⁷ nucleotides. Antibody 6A10 reliably detected adducts formed in vivo in rats and mice treated with AFB₁. In a pilot study, AFB₁adducts 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.