Apolipoprotein E (APOE), a member of the apolipoprotein family, is a plasma protein that plays a key role in lipid metabolism and cholesterol transport. It binds and transports cholesterol and triglycerides, helping these lipid molecules move steadily through the blood. In addition, the combination of APOE and APOB can promote the binding of lipoprotein particles to cell surface receptors, so that cholesterol and triglycerides in lipoprotein particles can be absorbed by cells, thereby clearing lipids in the blood. Thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human APOE and recombinant pig APOB. Briefly, biotin-linked APOE were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to APOB-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µl stop solution to the wells and read at 450 nm immediately. The binding activity of recombinant human APOE and recombinant pig APOB was shown in Figure 1, and this effect was in a dose dependent manner.