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.