Immunochemical detection of circulating oxidized high-density lipoprotein with antioxidized apolipoprotein A-I monoclonal antibody.

The oxidative susceptibility of high-density lipoprotein (HDL) may play a role in its antiatherogenic effects. In an effort to determine circulating levels of oxidized HDL in the bloodstream, we produced a monoclonal antibody (mAb), 3C11, specific to oxidized apolipoprotein A-I and developed an enzyme-linked immunosorbent assay (ELISA) for oxidized HDL that incorporates the mAb. The examination of oxidized forms of several lipoproteins showed that the ELISA had a high specificity for oxidized HDL and did not react appreciably with native, acetylated, or malondialdehyde-modified HDL or with the other lipoproteins and their oxidized forms. Using the ELISA, we detected oxidized HDL in human serum samples and determined serum levels of oxidized HDL in 40 healthy volunteers. The mean serum concentration of oxidized HDL was 4.65 +/- 2.65 U/dL (mean +/- SD; range 1.47-12.81 U/dL). Further analysis showed no correlation between serum concentrations of oxidized HDL and those of six serum markers: HDL, apolipoprotein A-I, oxidized low-density lipoprotein, C-reactive protein, thiobarbituric acid-reactive substances, and serum iron. The ELISA provides a method for measuring oxidized HDL in the circulation, and this determination may elucidate the clinical significance of HDL oxidation in human beings.