Human apolipoprotein C-II quantitation by sandwich enzyme-linked immunosorbent assay

A specific, sensitive and accurate, non competitive enzyme-linked immunosorbent assay was developed for the quantitation of human apolipoprotein C-II. Using apolipoprotein C-II and apolipoprotein C-III immunosorbent columns, monospecific anti-apolipoprotein C-II antibodies were prepared for coating and for the preparation of a peroxidase-antibody conjugate. The assay is sensitive down to 0.25 ng apolipoprotein C-II per assay and precise, with mean intra- and inter-assay coefficients of variation of 3.1% and 7.9% respectively. The apolipoprotein C-II concentrations in normolipaemic and hyperlipaemic plasma were not affected by delipidation, and increased only slightly after treatment with detergents or urea. The mean plasma apolipoprotein C-II concentration in a group of 30 normolipaemic subjects, was 33.1 +/- 7.5 mg/l. All hypertriglyceridaemic subjects had significantly elevated apolipoprotein C-II plasma concentrations, which were most pronounced in Fredrickson type III and type V patients. The apolipoprotein C-II profiles, obtained by column fractionation of 6 normolipaemic and 11 hypertriglyceridaemic plasmas, demonstrated a shift of apolipoprotein C-II towards the triglyceride-rich lipoproteins in hypertriglyceridaemic subjects.