Promotion of atherosclerosis in high cholesterol diet-fed rabbits by immunization with the P277 peptide

Previous evidence has proved the ability of immunization with heat shock protein (HSP) 60/65 to induce atherosclerosis. P277, a 24-residue peptide of human HSP60, is a promising peptide vaccine against autoimmune diabetes. But as a fragment of HSP60, its potential ability of promoting atherosclerosis has never been investigated yet. In the present study, the rabbits fed with normal standard diet or high cholesterol diet were immunized with P277 or PBS emulsified in incomplete Freund's adjuvant 4 times at 4-week intervals. Atherosclerotic lesions of the rabbits receiving P277 treatment and fed with high cholesterol diet increased significantly compared with those of the rabbits receiving PBS treatment and the same diet. However, no obvious lesions were found in the two groups of rabbits fed with the normal standard diet. Significant expression of P277 was detected in the high cholesterol diet-induced atherosclerotic lesions and heat-stressed endothelial cells. Surface exposure of P277 was also observed in the stressed cells. In the subsequent assay of endothelial cells in vitro, the purified anti-P277 antibodies mediated a noticeable cytotoxicity to the stressed cells with the participation of complement. In conclusion, subcutaneous immunization with P277 emulsified in IFA can aggravate the atherosclerosis in high cholesterol diet-fed rabbits. Surface expression of P277 was observed on stressed endothelial cells, and were suggested to mediate the autoimmune attack and promote the disease.