Antibody response to chlamydial heat shock protein 60 is strongly associated with acute coronary syndromes.

BACKGROUND Heat shock proteins (HSPs) are a family of proteins with immunogenic and proinflammatory properties. Human and Chlamydia pneumoniae (Cp) HSP60 were found in patients with stable coronary disease. METHODS AND RESULTS We measured the levels of anti-Cp-HSP60 and anti-Cp immunoglobulin G (IgG) in 179 patients with unstable angina, 40 with acute myocardial infarction, and 40 with stable angina (SA), as well as 100 control subjects. Forty-one patients with acute coronary syndromes (ACS) were also studied at follow-up. We also measured plasma levels of high-sensitivity C-reactive protein (hs-CRP) and troponin T (TnT). Seropositivity to Cp-HSP60 was found in 99% of ACS patients but in only 20% of SA patients and none of the control subjects. Seropositivity to Cp was detected in 67% of ACS patients, 60% of SA patients, and 30% of the control subjects. No differences in Cp-HSP60 IgG and in Cp IgG were observed between patients with myocardial infarction and patients with unstable angina. No correlation was found between Cp-HSP60 IgG, TnT, and hs-CRP or between IgG against Cp and hs-CRP. In ACS patients at follow-up, Cp-HSP60 IgG decreased from 0.88+/-0.25 to 0.45+/-0.14 arbitrary units (P<0.0001), becoming negative in 12 patients. CONCLUSIONS Seropositivity for Cp-HSP60 appears to be a very sensitive and specific marker of ACS, unrelated to Cp IgG antibody titers or hs-CRP and TnT levels. Its causal involvement in instability and its diagnostic role in ACS deserve further study.