Evaluation of methods for quantitation of aflatoxin-albumin adducts and their application to human exposure assessment.

Abstract

Aflatoxin (AF) albumin adducts are found in peripheral blood after exposure to aflatoxin B1 (AFB1) and the measurement of these adducts is potentially a useful tool in the epidemiological study of the role of AFB1 in the etiology of liver cancer. Three complementary approaches to the quantitation of AF-albumin adducts are described: (a) enzyme-linked immunosorbent assay (ELISA) performed directly on intact albumin (direct ELISA); (b) ELISA performed on an albumin hydrolysate (hydrolysis ELISA); (c) high-performance liquid chromatographic fluorescence detection of AF-lysine adduct after albumin hydrolysis and immunoaffinity purification. These techniques have been validated by direct comparison with rat albumin samples modified to a known extent. Detection limits of approximately 100, 5.0, and 5.0 pg AF/mg human albumin were determined for the three methods, respectively. Samples obtained from individuals from Thailand, The Gambia, Kenya, and France have been used to validate the measurement of AF-albumin adducts by these three methods. Levels of 7 to 338 pg AF/mg albumin were observed in the former two countries while no adducts were detected in samples from France. The relative properties of the three assays, with special regard to their application in epidemiological studies, are considered. A combination of the hydrolysis ELISA for large scale screening followed by confirmatory analyses in positive samples by high-performance liquid chromatographic fluorescence is suggested as an optimum methodology.