2-SITE ENZYME-IMMUNOASSAY OF CHOLESTERYL ESTER TRANSFER PROTEIN WITH MONOCLONAL AND OLIGOCLONAL ANTIBODIES

We developed a sandwich-type enzyme immunoassay to measure cholesteryl ester transfer protein (CETP) mass in human plasma. A specific monocl onal antibody (TP-4) that recognizes an epitope located in the C-termi nal domain was used for antigen capture and an anti-CETP peptide antib ody directed against the 290-306 residue was used for detection. Bound antibodies were revealed with an antibody-peroxidase conjugate specif ic for rabbit IgG. The presence of 10 mL/L Triton X-100 in the incubat ion buffer increased antigen exposure of CETP in plasma. The curves fo r CETP in standard plasma and partially purified CETP were parallel. T his technique is rapid (results within 6 h), accurate, precise (mean i ntra- and interassay CVs 3.6% and 8.4%, respectively), and simple to p erform. Assay sensitivity is at microgram concentrations, with a worki ng range of 20-200 mu g/L. In 40 normolipidemic healthy subjects, the mean CETP concentration in plasma was 1.1 +/- 0.4 mg/L. A strong corre lation between CETP concentration and CETP activity (r = 0.91, n = 42) was observed. In plasma, the bulk of CETP was found in high-density l ipoprotein fractions. Therefore, this assay may be a useful tool for i nvestigations of CETP and its significance in relevant diseases.