AN ENZYME-LINKED-IMMUNOSORBENT-ASSAY METHOD TO MEASURE HUMAN APOLIPOPROTEIN-E LEVELS USING COMMERCIALLY AVAILABLE REAGENTS - EFFECT OF APOLIPOPROTEIN-E POLYMORPHISM ON SERUM APOLIPOPROTEIN-E CONCENTRATION

A sensitive and specific enzyme-linked immunosorbent assay (ELISA) for human apolipoprotein E (ape E) quantification using commercially avai lable reagents is described. The assay is a noncompetitive, sandwich E LISA in which the wells were coated with a monoclonal EO1 antibody ant i-human ape E and detected with a polyclonal antibody-peroxidase conju gate anti-apo E. The mean ape E concentration in 168 middle-aged subje cts randomly selected from general population was 51.7 +/- 12.4 mg/lit er. Apo E levels were highly correlated with ape E phenotypes. Apo E p olymorphism, which shows a modulating effect in the catabolism of ape E containing lipoproteins, may explain a large fraction, 18.5%, of the variability of serum ape E levels in middle-aged population. Isoforms apo E2 and apo E4 have an opposite effect on the regulation of serum ape E concentrations. Individuals that express ape E2 isoform present higher ape E levels (65.5 mg/liter for ape E2/E3), whereas the average of individuals with ape E4 is lower (42.8 mg/liter for ape E4/E3) tha n general population. (C) 1994 Academic Press, Inc.