Immunoblotting analysis of abdominal aortic aneurysms using antibodies against Chlamydia pneumoniae recombinant MOMP

Objectives: antibodies against Chlamydia pneumoniae have been associated with atherosclerosis and with expansion of abdominal aortic aneurysms (AAA). C. pneumoniae has been demonstrated in coronary arteries, AAA and the carotid arteries by use of polymerase chain reactions (PCR), immunohistochemical procedures and electron microscopy. However, the correlation between demonstrating C. pneumoniae DNA or antigen in tissue from plaque material or aneurysms and the antibody titres in serum is controversial. The specificity of immunohistochemical procedures is unknown. The aim of this study was to assess the possibility of potential non-specific findings for methods based on immunostaining. Materials and methods: twenty patients undergoing infrarenal AAA repair were studied, Full AAA thickness tissue was collected from the anterior wall of the aneurysm. Analysis was performed using polyacrylamide gelelectrophoresis, immunoblotting and mass spectrometric protein identification. Results: C. pneumoniae antigen was not demonstrated in any of the AAA samples, whereas a major cross-reacting protein was present in all AAA samples. The protein was identified as the human haemoglobin beta chain. Conclusion: we were not able to find C. pneumoniae antigens reacting with an anti C. pneumoniae major older membrane protein (MOMP). Direct detection of C. pneumoniae by immunohistostaining procedures should be interpreted with caution due to potential crossreaction with non chlamydial proteins.