Characterization of anti-apolipoprotein A-I monoclonal antibodies and their use in the measurement of apolipoprotein A-I by a two-site enzyme immunoassay.

Six monoclonal antibodies raised against pure apo A-I or high density lipoprotein were characterized for epitope specificity by enzyme and radioimmunoassays, immunodiffusion and affinity chromatography. The six antibodies were classified into three groups according to the region of apo A-I they reacted with. The antibody VI10H, from group II, appeared to recognize a region fully exposed on native HDL-apo A-I, whereas group I comprised antibodies specific for a partially masked region. Group III comprised only one antibody. Use of the non-ionic detergent Tween 20 in the immunoassays permitted antibodies from the three groups to react with their respective epitope on native HDL-apo A-I. An antibody from group I (V4F) was chosen as the first antibody and VI10H, the antibody showing the highest affinity, was chosen for the anti-A-I-peroxidase conjugate in a two-site enzyme immunoassay.