Preliminary Studies on the Indium Slide Immunoassay for Estimation of Human Chorionic Gonadotropin and Antihuman Chorionic Gonadotropin Antibody

Human chorionic gonadotropin (hCG) is synthesized and secreted as early as 170 hr after fertilization and has been used as an index for pregnancy. Neutralization of hCG with a β-subunit hCG vaccine(s) has been proposed as a contraceptive technique. To monitor the duration of effectiveness of the vaccine, it will be necessary to monitor the anti-hCG antibodies, especially those responsible for inhibiting the hCG bioactivity. We report a simple, rapid technique using an indium slide immunoassay for the qualitative estimation of hCG and to monitor a bioeffective anti-hCG antibody. The sensitivity of the indium slide assay to measure hCG ranged from 1 μg/ml to 1 ng/ml, depending on the format of the assay. The indium slide assay also detected anti-hCG antibodies generated against a specific determinant on hCG recognized by a neutralizing monoclonal antibody (P₃W₈₀) in women immunized with a contraceptive vaccine.