Possible effect of infection with liver fluke (Opisthorchis viverrini) on the monitoring of urine by enzyme-linked immunosorbent assay for human exposure to aflatoxins.

Several laboratories have initiated studies to assess human exposure to aflatoxin at an individual level by measuring aflatoxin metabolites in the urine by immunoassay. The fact that the antibodies recognize a variety of metabolites, albeit with differing affinities, means that any environmental factor that modifies the pattern of urinary metabolites associated with a given exposure could affect quantification in immunoassay. We have examined two such possible effects: (i) the pattern of metabolites after a dose of 14C-aflatoxin B1 in rats and (ii) the pattern of metabolites in hamsters and humans with and without exposure to liver flukes. We found no dose-related effect on the pattern of urinary metabolites over a 250-fold range, but there was a significant increase in the proportion of water-soluble aflatoxin metabolites in hamsters infected with liver fluke over that in uninfected animals. In human urine samples, there also appeared to be a difference in the metabolites in individuals infected with liver fluke from those in uninfected persons. These observations are relevant to both mechanistic and monitoring aspects of research into aflatoxins.