Anti-oxidized low-density lipoprotein antibodies in patients with coronary heart disease and normal healthy volunteers

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Abstract
We have developed a solid-phase enzyme immunoassay for anti-oxidized low-density lipoprotein antibodies. Most sera showed some degree of non-specific binding to plates coated with oxidized low-density lipoprotein and the autoantibodies to oxidized low-density lipoprotein often appeared to have a relatively low affinity. To differentiate between specific and non-specific binding each sample was tested untreated and after absorption with oxidized low-density lipoprotein. The optical densities obtained with dilutions of the absorbed sample were considered to reflect non-specific binding and were subtracted from values obtained with identical dilutions of the unabsorbed sample, to yield corrected values from which the concentrations of anti-oxidized low-density lipoprotein antibody were calculated. Similar absorptions with native low-density lipoprotein and oxidized human serum albumin failed to induce a significant reduction in binding to immobilized oxidized low-density lipoprotein proving that the antibodies measured by this assay are primarily specific for oxidized low-density lipoprotein. We studied sera from two groups of individuals: (1) 33 subjects submitted to coronary angiography and split into two subgroups depending on the degree of coronary stenosis and (2) 64 healthy individuals also split into two subgroups according to lipid levels. Anti-oxidized low-density lipoprotein antibodies were detected both in patients and healthy individuals. Higher levels were detected in patients with moderate coronary disease and hyperlipemic healthy individuals, but the differences between patients and healthy volunteers or between their respective subgroups did not reach statistical significance. Our results suggest that autoantibodies to oxidized low-density lipoprotein are relatively frequent in both symptomatic and asymptomatic individuals. The investigation of their potential role as a risk factor will require mass screening and long-term follow-up.