Is there a role for Chlamydia pneumoniae infection in systemic lupus erythematosus and in the associated atherosclerotic cardiovascular disease?

Objective. To search for molecular evidence of Chlamydial infection in systemic lupus erythematosus (SLE) subjects and to assess if there is an association of this infectious agent with coronary artery calcification (CAC) a marker of total atherosclerotic burden. Methods. 28 SLE subjects had blood samples drawn and DNA extracted from peripheral blood mononuclear cells (PBMC) and an electron beam computed tomography (EBCT) scan. Polymerase chain reaction (PCR) analysis was performed for Chlamydia trachomatis 16srRNA and major outer membrane protein (MOMP) and for C. pneumoniae 16srRNA, MOMP as well as nested PCR for MOMP. Results. Four of 28 subjects (14.2%) had evidence of C. pneumoniae nucleic acid in PBMC The 16srRNA primers detected C. pneumoniae in one patient (3.57%) and the nested PCR MOMP primers in 3 subjects (10.71%). None were positive for Chlamydia trachomatis. Two of the 4 subjects with C. pneumoniae DNA had abnormal EBCT scans and 2/11 (18.3%) subjects with abnormal EBCT were positive for C. pneumoniae. There were significant associations of C. pneumoniae DNA with smoking (OR = 3) and corticosteroid use. The odds ratio for subjects with abnormal CAC and detectable C. pneumoniae was 1.67. Conclusion. This pilot study demonstrates for the first time that C. pneumoniae DNA can be identified in the PBMC of some SLE subjects and there may be an association with CAC Smoking may be an additional risk factor for infection in this population. Determination of pathogenicity of this organism in atherosclerotic coronary vascular disease in SLE will require further study.