Blockade of interleukin-12 function by protein vaccination attenuates atherosclerosis

Background-Interleukin-12 (IL-12) has been identified as a key inducer of a type 1 T-helper cell cytokine pattern, which is thought to contribute to the development of atherosclerosis. We sought to study the role of IL-12 in atherosclerosis by inhibition of IL-12 using a newly developed vaccination technique that fully blocks the action of IL-12. Methods and Results-LDL receptor-deficient (LDLr-/-) mice were vaccinated against IL-12 by 5 intramuscular injections of IL-12-PADRE complex in combination with adjuvant oil-in-water emulsion ( low dose)/MPL/QS21 every 2 weeks. Two weeks thereafter, atherogenesis was initiated in the carotid artery by perivascular placement of silicone elastomer collars. IL-12 vaccination resulted in the induction of anti-IL-12 antibodies that functionally blocked the action of IL-12 as determined in an IL-12 bioassay. Blockade of IL-12 by vaccination of LDLr-/- mice resulted in significantly reduced (68.5%; P < 0.01) atherogenesis compared with control mice without a change in serum cholesterol levels. IL-12 vaccination also resulted in a significant decrease in intima/media ratios (66.7%; P < 0.01) and in the degree of stenosis (57.8%; P < 0.01). On IL-12 vaccination, smooth muscle cell and collagen content in the neointima increased 2.8-fold (P < 0.01) and 4.2-fold (P < 0.01), respectively. Conclusions-Functional blockade of endogenous IL-12 by vaccination resulted in a significant 68.5% reduction in atherogenesis in LDLr-/- mice. Vaccination against IL-12 also improved plaque stability, from which we conclude that the blockade of IL-12 by vaccination may be considered a promising new strategy in the treatment of atherosclerosis.