Relationship of Chlamydia pneumoniae infection to severity of human coronary atherosclerosis

Background-Infection with Chlamydia pneumoniae has been postulated to play a pathogenic role in atherosclerosis. We examined the role of infection wit h C pneumoniae in relation to the extent of coronary atherosclerosis. Methods and Results-Coronary atherosclerosis was graded microscopically on a postmortem basis in a blinded fashion in 60 subjects as mild (n=18) or se vere (n=42) atherosclerosis. Serum antibodies to C pneumoniae were measured by microimmunofluorescence test. Paraffin-embedded coronary artery specime ns were examined for the presence of chlamydia by use of a genus-specific d irect immunofluorescence monoclonal antibody. Frozen coronary artery specim ens were examined by immunoperoxidase for the presence of C pneumoniae by u se of a specific monoclonal antibody RR-402. Direct immunofluorescence was reactive in 86% of cases with severe atherosclerosis but in only 6% of case s with mild atherosclerosis (P<0.01), whereas immunoperoxidase staining was reactive in 80% and 38% of cases with seven and mild atherosclerosis, resp ectively (P<0.01). Elevated IgG and IgA levels against C pneumoniae were no t different in cases with severe and mild atherosclerosis (61% and 30% for severe atherosclerosis and 67% and 42% for mild atherosclerosis, respective ly). Conclusions This Study supports the hypothesis that intracellular infection with C pneumoniae may relate to the severity of atherosclerosis in some su bjects. Serum antibody titers against C pneumoniae do not differentiate bet ween seven and mild atherosclerosis.