title: Serum antibodies against Chlamydia pneumoniae outer membrane protein cross-react with the heavy chain of immunoglobulin in the wall of abdominal aortic aneurysms.
abstract: BACKGROUND
  Chlamydia pneumoniae (Cp) has been demonstrated in arteries and abdominal aortic aneurysms (AAAs). However, the validity of the methods used is questioned, and antibiotic treatment trials have thus far shown disappointing results. Nevertheless, antibodies against the Cp outer membrane proteins (OMPs) have been associated with progression of atherosclerosis and AAAs. The aim of this study was to detect Cp OMPs in the wall of AAA patients by use of purified serum antibodies directed against Cp OMP and to assess potential cross-reacting proteins in AAA walls.
  
  
  RESULTS
  Seventeen patients undergoing infrarenal AAA repair were studied. Full AAA thickness tissue was collected from the anterior wall of the aneurysm. Anti-OMP was extracted from seropositive AAA patients by use of an ELISA kit (Labsystems). Analysis was performed by use of 2D polyacrylamide gel electrophoresis, immunoblotting, and mass spectrometric protein identification. OMP antigens were not detected in 16 of 17 AAA walls. However, 3 major AAA proteins cross-reacted with anti-OMP. The proteins were all identified as heavy chains of human immunoglobulin.
  
  
  CONCLUSIONS
  We could not find evidence of Cp OMP in 16 of 17 AAA walls, but instead, all samples showed a strong cross-reaction between Cp OMP antibodies and human immunoglobulin. This might indicate that AAA is an autoimmune disease, perhaps triggered by an initial Cp infection.
authors.affiliation: Department of Vascular Surgery, Viborg Hospital, Postbox 130, 8800 Viborg, Denmark. jslindholt@mail.tele.dk
authors.forename: Jes S
authors.initials: JS
authors.lastname: Lindholt
authors.forename: Jette
authors.initials: J
authors.lastname: Støvring
authors.forename: Lars
authors.initials: L
authors.lastname: Østergaard
authors.forename: Sigitas
authors.initials: S
authors.lastname: Urbonavicius
authors.forename: Eskild W
authors.initials: EW
authors.lastname: Henneberg
authors.forename: Bent
authors.initials: B
authors.lastname: Honoré
authors.forename: Henrik
authors.initials: H
authors.lastname: Vorum
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000276:immunology*; D000915:Antibody Affinity; D000918:Antibody Specificity; D000942:Antigens, Bacterial / Q000276:immunology*; D017544:Aortic Aneurysm, Abdominal / Q000276:immunology* / Q000473:pathology; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology*; D016993:Chlamydophila pneumoniae / Q000276:immunology*; D002846:Chromatography, Affinity; D003429:Cross Reactions; D015180:Electrophoresis, Gel, Two-Dimensional; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D016622:Silver Staining
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D007070:Immunoglobulin A; D007075:Immunoglobulin M