Chlamydia pneumoniae and Oxidative Stress in Cardiovascular Disease: State of the Art and Prevention Strategies

It is currently unclear what causes the chronic inflammation within atherosclerotic plaques. One emerging paradigm suggests that infection with bacteria and/or viruses can contribute to the pathogenesis of atherosclerosis either via direct infection of vascular cells or via the indirect effects of cytokines or acute phase proteins induced by infection at non-vascular sites. This paradigm has been supported by multiple epidemiological studies that have established positive associations between the risk of cardiovascular disease morbidity and mortality and markers of infection. It has also been supported by experimental studies showing an acceleration of the development of atherosclerosis following infection of hyperlipidaemic animal models. There are now a large number of different infectious agents that have been linked with an increased risk of cardiovascular disease. These include: Chlamydia pneumoniae, Porphyromonas gingivalis, Helicobacter pylori , influenza A virus, hepatitis C virus, cytomegalovirus, and human immunodeficiency virus. However, there are significant differences in the strength of the data supporting their association with cardiovascular disease pathogenesis. In some cases, the infectious agents are found within the plaques and viable organisms can be isolated suggesting a direct effect. In other cases, the association is entirely based on biomarkers. In the following review, we evaluate the strength of the data for individual or groups of pathogens with regard to atherosclerosis pathogenesis and their potential contribution by direct or indirect mechanisms and discuss whether the established associations are supportive of the infectious disease paradigm. We also discuss the failure of antibiotic trials and the question of persistent infection.

Paired sera from 40 male patients with acute myocardial infarction (AMI), 30 male patients with chronic coronary heart disease (CCHD), and 41 controls, matched for sex, age, time, and locality were investigated for antibodies to a novel type of Chlamydia sp, TWAR, and to chlamydial lipopolysaccharide (LPS) group antigen. 27 patients with AMI (68%), and 15 (50%) patients with CCHD had raised IgG (greater than or equal to 128) and/or IgA (greater than or equal to 32) titres in the microimmunofluorescence test with chlamydia TWAR. Both frequencies were significantly higher than in the controls (7, 17%). 26 (68%) of 38 patients with AMI also showed a significant seroconversion in enzyme immunoassay with LPS antigen; this response was absent in all patients with CCHD and all but 1 of the controls. Chronic chlamydial infection could be a factor in the pathogenesis of cardiovascular diseases.