A delayed-addition enzyme immunoassay for the relative cholesteryl ester transfer protein mass in patients with deficient plasma cholesteryl ester transfer activity

The biochemical basis for the apparent deficiency of cholesteryl ester (CE) transfer activity was investigated in two unrelated subjects with markedly elevated high density lipoprotein-cholesterol (Atherosclerosis 1988; 70:7-12). Essentially no CE or triglyceride transfer activity was detected in the patients' plasma, utilizing four different lipid transfer assays. Using polyclonal antibodies raised against human plasma cholesteryl ester transfer protein (CETP), a delayed-addition enzyme immunoassay was developed to determine plasma CETP mass. CETP could not be detected with this assay in the plasma of the two subjects with transfer activity deficiency, indicating that the CE transfer activity deficiency in these subjects is due to the absence of plasma CETP. In addition, three hyperalphalipoproteinemic subjects with a partial deficiency of CE transfer activity had a reduced level of CETP mass. There was a good correlation between plasma CETP activity and mass levels. The principles of this immunoassay may be applicable to measure the mass levels of other proteins with catalytic activities.