Quantitation of human serum apolipoprotein B by enzyme immunoassay in excess antigen

A solid phase enzyme-linked immunoassay based on the 'sandwich' principle was developed for quantitative measurement of apolipoprotein B (Apo B) in human normal or hyperlipoproteinemic sera. The solid phase (polypropylene multi-finned sticks) coated with an excess of sheep anti-Apo B immunoglobulins was incubated with antigen (standards and unknown specimens) and affinity-purified anti-Apo B antibodies conjugated with horseradish peroxidase. In this principle, antigen and conjugate were in excess and fixed amount respectively. A part of antigen was fixed on multi-finned sticks, bound or not to conjugate. Unbound materials were removed by washing. Solid phases were next incubated with the enzyme substrate solution to develop a color which is inversely related to the amount of Apo B. The best technical conditions for the assay were determined. The method was characterized according to precision, sensitivity and accuracy. It yielded values that compared favorably with those obtained by another enzyme-linked immunoassay and by electroimmunoassay.