Human fetal and tumor alpha-fetoproteins differ in conformationally dependent epitope variants expression

Expression of two conformationally dependent epitopes (cdes) designated as cdeD and cde106 of human alpha-fetoprotein (hAFP) was studied in hAFP of fetal and tumor origin. This was done by immunoaffinity electrochromatography on nitrocellulose membrane and by ELISA. Using anti-cdeD and anti-cde106 monoclonal antibodies (MoAbs), the relationship between the cde-positive and cde-negative hAFP fractions was evaluated in 75 samples with the above techniques. It was shown that hAFP consists of cde-positive and -negative variants irrespective of its tissue origin. In all the tested AFP samples, cde-negative variants were found to be predominant, while certain quantitative differences in the content of cde-positive variants were observed. Thus, in the amniotic fluid hAFP (irrespective of normal or pathological fetal development), the level of the cde-positive molecules was higher than in hAFP of other origin (cord blood serum, patients' sera with hepatocellular carcinoma, germ cell tumors, and the other hAFP-positive tumor cases). In all the tested samples, cdeD- and cde106-positive variants were revealed practically in parallel with each other.