Immunization With Homologous Oxidized Low Density Lipoprotein Reduces Neointimal Formation After Balloon Injury in Hypercholesterolemic Rabbits

Objectives. In this study we tested the hypothesis that immunization with homologous oxidized low density lipoprotein (oxLDL) would inhibit the neointimal response to balloon injury in hypercholesterolemic rabbits. Background. Immunization with homologous oxLDL has been shown to markedly reduce aortic atherosclerosis in LDL receptor-deficient as well as cholesterol-fed rabbits; however, the effect of this strategy on the balloon injury-induced neointimal lesion is unknown. Methods. New Zealand White rabbits were immunized with 280 μg of homologous native LDL (n = 5), copper-oxidized LDL (n = 5) or phosphate buffer as control (n = 5) and fed 1% cholesterol diet. Rabbits were reimmunized after 3 weeks, and balloon injury of the right ileofemoral artery was performed 1 week later. Four weeks after balloon injury, rabbits were killed, and the neointimal lesion are was measured by computerized morphometry after perfusion fixation of the arteries. Circulating antibodies against oxLDL were measured by enzyme-linked immunosorbent assay. Results. In comparison with the control animals, those immunized with oxLDL had 58% reduction in the neointimal are (0.53 ± 0.13 vs. 1.27 ± 0.26 mm2; p = 0.01). The group immunized with native LDL had 19% reduction in the neointimal are compared with the control group (p = NS). Circulating cholesterol levels and antibody titers against oxLDL were comparable in the three groups. There was trend toward reduced immunoreactivity for T cells and oxLDL in the neointim of oxLDL-immunized animals. Conclusions. Hypercholesterolemic rabbits immunized with homologous oxLDL have markedly reduced neointimal are after balloon injury despite severe hypercholesterolemia. Together with previous work, these dat suggest that an immunization strategy (vaccination) against atherosclerosis and restenosis warrants further investigation.