Enzyme-immunoassay of human alpha-fetoprotein

An enzyme-immunoassay for the quantitation of human alpha-fetoprotein was developed employing the so-called sandwich method using filter paper discs as a solid-phase. Filter paper discs were activated with cyanogen bromide and the specific antibody to alpha-fetoprotein was covalently bound to the discs. The enzyme-labeled antibody was prepared by coupling the antibody to alkaline phosphatase with the aid of glutaraldehyde. The antibody-coated filter paper discs were incubated with the samples containing alpha-fetoprotein, which was bound to the discs, then the discs were incubated with the enzyme-labeled antibody solution. The enzyme activity bound on the discs was then measured, and was found to be proportional to the amount of alpha-fetoprotein in the sample. The present method provided an accurate measurement for human alpha-fetoprotein in test serum in a range of 40 approximately 1,000 ng/ml. The sensitivity was almost comparable to that of radioimmunoassay. alpha-Fetoprotein levels in the normal and patient sera tested with this method were in good agreement with the values obtained by the radioimmunoassay technique.