Immunization with bacillus Calmette–Guerin vaccine increases aortic atherosclerosis in the cholesterol-fed rabbit Original Research Article

New Zealand White rabbits were injected subcutaneously with either a human dose of bacillus Calmette–Guerin (BCG) vaccine (n=7) or saline (n=7). A further half dose of BCG or saline was injected after a further 4 weeks. The animals were subsequently fed a 0.25-1% cholesterol diet for 10 weeks, 8 weeks after the first injection. The rabbits were killed and perfusion fixed with 4% paraformaldehyde. The integrated plasma cholesterol levels did not differ significantly between the groups (P>0.05). Plasma levels of anti-mycobacterial antibodies rose following BCG immunization, reaching a peak after 8 weeks (P<0.05) compared to basal titers and the control group. BCG immunization was also associated with increased peripheral lymphocyte and monocyte activation, as evidenced by increased surface expression of IL-2 receptor (CD25) (P<0.02) and MAC-1 (CD11b) (P<0.05), respectively. Significantly more mononuclear cells bound to the aortic endothelium of BCG immunized, cholesterol-fed rabbits (1.93±0.77 mononuclear cells/1000 endothelial cells) than to that of saline immunized rabbits (0.08±0.08 mononuclear cells/1000 endothelial cells; P<0.01). The aortic intimal:medial ratio was greater in the BCG immunized rabbits (0.19±0.08) than those treated with saline (0.04±0.03; P<0.05). This suggests that BCG immunization enhances peripheral leucocyte activation, aortic monocyte recruitment and atherogenesis in the cholesterol-fed rabbit.