Possible role of chronic infection with Chlamydia pneumoniae in Japanese patients with acute myocardial infarction

Chlamydia pneumoniae, a common human respiratory pathogen, has been implica ted in the pathogenesis of coronary heart diseases (CHD) in several seroepi demiological studies. The present case-control study investigated the relat ion between serologic evidence of C. pneumoniae infection and CHD in a Japa nese population. Two groups of cases were enrolled: 26 patients with acute myocardial infarction (AMI) and 46 patients with effort angina pectoris (e- AP). Their data were compared with 58 age-matched healthy controls and also compared with 53 patients with vasospastic angina (VSA) as pathological co ntrol subjects, Anti-C. pneumoniae specific IgA and IgG antibody titers wer e measured by enzyme-linked immunosorbent assay (ELISA). The mean indices o f IgG-type antibody in AMI and e-AP were not significantly different from t hose in either the normal controls or VSA group. On the other hand, the mea n indices of IgA-type antibody in AMI were significantly higher than in the normal controls (1.39+/-0.83 in AMI vs 0.84+/-0.58 in controls, p<0.001) a nd VSA (1.39+/-0.83 in AMI vs 1.05+/-0.61 in VSA, p<0.05) group. However, t he differences in the IgA titers in the e-AP group compared with the normal controls did not reach a significant level. The odds ratio associated with the seropositivity of IgA for AMI against the normal controls was 3.89 (95 % confidence interval (CI): 1.16-13.10) and that against VSA was 6.90 (95% CI: 1.73-27.52) after adjustment for risk factors for CHD and/or age, sex a nd smoking status. In 6 patients the elevated IgA titers were sustained eve n at 3 months after the episode of AMI. These results suggest that seroposi tivity for IgA-type antibody against C. pneumoniae may be a significant ris k factor for the development of AMI. The possible mechanisms include chroni c inflammation in the coronary artery due to persistent C. pneumoniae infec tion.