The Role of Infection in Atherosclerosis and Coronary Artery Disease: a New Therapeutic Target

There is growing evidence that inflammatory processes may be involved in the development of atherosclerosis and its complications. Viral and bacterial pathogens have been implicated as possible causative factors in the pathogenesis of coronary artery disease (CAD) and restenosis after angioplasty. Antibiotic trials are now in progress to examine whether treatment of infection can prevent the complications of CAD. Atherosclerosis, the primary pathologic process in coronary artery disease (CAD), carotid artery disease, abdominal aortic aneurysm, and peripheral vascular disease, is no longer considered to be an obscure, slowly progressive, degenerative disease. Indeed, recent molecular studies on the atherosclerotic plaque have shown that the initiation, progression, and acute sequelae of atherosclerosis can be explained in part by a low-grade inflammatory process. Studies show that mediators of inflammation can be found at all stages of the life cycle of the atherosclerotic plaque. These include activated macrophages and lymphocytes, cytokines, growth factors, matrix degenerating proteinases, and tissue factor. It is hypothesized that risk factors such as hypertension, smoking, or elevated levels of low-density lipoprotein (LDL) cholesterol result in injury to the endothelial cell of the artery, and this injury initiates the inflammatory process. However, many patients with vascular disease do not have these established risk factors, and this observation has galvanized efforts to find new risk factors. Because inflammation is now considered to be an operative paradigm for atherosclerosis, it is not a major leap to the hypothesis that infectious agents, such as viral or bacterial, may play a role. Certainly this is not a new concept, and with the recent discovery that peptic ulcer disease, heretofore considered a disease of excess acid and reduced mucosal resistance, is caused by the ubiquitous bacterium Helicobacter pylori, interest in finding an infectious etiology for atherosclerosis has increased. Accordingly, the purpose of this discussion is to review in a historical manner the evidence that infectious agents-including herpes simplex virus (HSV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), Enterovirus (adenovirus, Coxsackie virus), Chlamydia pneumoniae, and H. pylori-may play a role in atherosclerosis and its manifestations, especially as they relate to CAD.