Purification, crystallization and preliminary crystallographic analysis of Chlamydophila pneumoniae AP endonuclease IV.

Base excision is a crucial DNA repair process mediated by endonuclease IV in nucleotide excision. In Chlamydia pneumoniae, CpendoIV is the exclusive AP endonuclease IV, exhibiting DNA replication error-proofreading capabilities, making it a promising target for anti-chlamydial drug development. Predicting the structure of CpendoIV, molecular docking with DNA was performed, analyzing complex binding sites and protein surface electrostatic potential. Comparative structural studies were conducted with E. coli EndoIV and DNA complex containing AP sites.CpendoIV was cloned, expressed in E. coli, and purified via Ni-NTA chelation and size-exclusion chromatography. Low NaCl concentrations induced aggregation during purification, while high concentrations enhanced purity.CpendoIV recognizes and cleaving AP sites on dsDNA, and Zn2+ influences the activity. Crystallization was achieved under 8% (v/v) Tacsimate pH 5.2, 25% (w/v) polyethylene glycol 3350, and 1.91 Å resolution X-ray diffraction data was obtained at 100 K. This research is significant for provides a deeper understanding of CpendoIV involvement in the base excision repair process, offering insights into Chlamydia pneumoniae.

Immune regulation by oral tolerance induces alternate activation of macrophages and reduces markers of plaque destabilization in Apobtm2Sgy/Ldlrtm1Her/J mice.

Atherosclerosis is the leading cause for cardiovascular mortality. We determined the effect of multi-antigenic construct expressing three peptides AHC (ApoB100, HSP60 and outer membrane protein of chlamydia pneumonia) in stabilizing advanced atherosclerosis in Apobtm2Sgy/Ldlrtm1Her/J mice. Atherosclerosis was induced by feeding high fat diet (HFD) to mice for 10 weeks, followed by five oral dosing with purified AHC or ovalbumin on alternate days and continued on HFD for another 10 weeks. Tolerance was associated with significantly higher numbers of regulatory T cells both in aortic sinus and spleen with higher mRNA expression of CTLA4 (3 fold), Foxp3 (1.4 folds) and TGF-ß (1.62) in aorta. Tregs cells were found to induce alternate activation of macrophages to M2 phenotype, with a reduction in plaque inflammation. AHC treatment showed evidence of plaque stabilization as observed by reduction in plaque necrosis in aortic sinus (35.8%) and in brachiocephalic artery (26%), with reduced expression of Tissue factor and MMP9. Macrophage apoptosis was reduced and collagen content was enhanced by treatment. Our results suggest that tolerance to atherogenic peptides increases regulatory T cells which activate M2 macrophages, prevent T cell proliferation and reduce plaque destabilization and inflammatory markers thus providing evidences for plaque stabilization in mice with advanced atherosclerosis.

Insights into structure and function of 30S Ribosomal Protein S2 (30S2) in Chlamydophila pneumoniae: A potent target of pneumonia.

The gene 30S ribosomal protein S2 (30S2) is identified as a potential drug and vaccine target for Pneumonia. Its structural characterization is an important to understand the mechanism of action for identifying its receptor and/or other binding partners. The comparative genomics and proteomics studies are useful for structural characterization of 30S2 in C. Pneumoniae using different bioinformatics tools and web servers. In this study, the protein 30S2 structure was modelled and validated by Ramachandran plot. It is found that the modelled protein under most favoured "core" region was 88.7% and overall G-factor statistics with average score was -0.20. However, seven sequential motifs have been identified for 30S2 with reference codes (PR0095, PF0038, TIGR01012, PTHR11489, SSF52313 and PTHR11489). In addition, seven structural highly conserved residues have been identified in the large cleft are Lys160, Gly161and Arg162 with volume 1288.83Å3 and average depth of the cleft was 10.75Å. Moreover, biological functions, biochemical process and structural constituents of ribosome are also explored. The study will be helped us to understand the sequential, structural, functional and evolutionary clues of unknown proteins available in C. Pneumoniae.

Systems Biology Approaches for the Prediction of Possible Role of Chlamydia pneumoniae Proteins in the Etiology of Lung Cancer.

Accumulating evidence has recently supported the association of bacterial infection with the growth and development of cancers, particularly in organs that are constantly exposed to bacteria such as the lungs, colon, cervical cancer etc. Our in silico study on the proteome of Chlamydia pneumoniae suggests an unprecedented idea of the etiology of lung cancer and have revealed that the infection of C. pneumoniae is associated with lung cancer development and growth. It is reasonable to assume that C. pneumoniae transports its proteins within host-intracellular organelles during infection, where they may work with host-cell proteome. The current study was performed for the prediction of nuclear targeting protein of C. pneumoniae in the host cell using bioinformatics predictors including ExPASy pI/Mw tool, nuclear localization signal (NLS) mapper, balanced sub cellular localization predictor (BaCeILo), and Hum-mPLoc 2.0. We predicted 47/1112 nuclear-targeting proteins of C. pneumoniae connected with several possible alterations in host replication and transcription during intracellular infection. These nuclear-targeting proteins may direct to competitive interactions of host and C. pneumoniae proteins with the availability of same substrate and may be involved as etiological agents in the growth and development of lung cancer. These novel findings are expected to access in better understanding of lung cancer etiology and identifying molecular targets for therapy.

Enzymatic characterization of Chlamydophila pneumoniae phospholipase D.

Chlamydophila pneumoniae, an aetiological agent of respiratory infection, is also thought to play an immuno-pathogenetic role in atherosclerosis by contributing to inflammation and plaque instability. Phospholipase D (PLD) is an enzyme involved in lipid metabolism and may have a direct or indirect impact on virulence and the inflammatory response. Some aspects of the developmental cycle of C. pneumoniae suggest a direct implication of its PLD (CpPLD) in the pathogenesis, specifically by affecting the regulation of lipid metabolism and lipid exchange between C. pneumoniae and host cells. Our previous studies disclosed a specific anti-CpPLD antibody response in patients with acute coronary syndromes chronically infected with C. pneumoniae, and demonstrated that this antigen is a factor able to drive the inflammatory process in atherosclerosis. Due to the intriguing aspects of the CpPLD, the present study investigated CpPLD enzymatic activity of the protein and the two domains that include one HKD motif each polypeptide. Our results showed that CpPLD was able to synthesize the cardiolipin (CL) but unable to hydrolyze phospholipids. It was also observed that each single HKD motif has an independent CL synthetase activity. This enzymatic activity of CpPLD could be important in the inflammatory process within the atherothrombotic events.

Involvement of Ser94 in RNase HIII from Chlamydophila pneumoniae in the recognition of a single ribonucleotide misincorporated into double-stranded DNA.

We recently provided the first report that RNase HIII can cleave a DNA-rN(1)-DNA/DNA substrate (rN(1), one ribonucleotide) in vitro. In the present study, mutagenesis analyses and molecular dynamics (MD) simulations were performed on RNase HIII from Chlamydophila pneumoniae AR39 (CpRNase HIII). Our results elucidate the mechanism of ribonucleotide recognition employed by CpRNase HIII, indicating that the G95/K96/G97 motif of CpRNase HIII represents the main surface interacting with single ribonucleotides, in a manner similar to that of the GR(K)G motif of RNase HIIs. However, CpRNase HIII lacks the specific tyrosine required for RNase HII to recognize single ribonucleotides in double-stranded DNA (dsDNA). Interestingly, MD shows that Ser94 of CpRNase HIII forms a stable hydrogen bond with the deoxyribonucleotide at the (5')RNA-DNA(3') junction, moving this nucleotide away from the chimeric ribonucleotide. This movement appears to deform the nucleic acid backbone at the RNA-DNA junction and allows the ribonucleotide to interact with the GKG motif. Based on the inferences drawn from MD simulations, biochemical results indicated that Ser94 was necessary for catalytic activity on the DNA-rN(1)-DNA/DNA substrate; mutant S94V could bind this substrate but exhibited no cleavage. Mismatches opposite the single ribonucleotide misincorporated in dsDNA inhibited cleavage by CpRNase HIII to varying degrees but did not interfere with CpRNase/substrate binding. Further MD results implied that mismatches impair the interaction between Ser94 and the deoxyribonucleotide at the RNA-DNA junction. Consequently, recognition of the misincorporated ribonucleotide was disturbed. Our results may help elucidate the distinct substrate-recognition properties of different RNase Hs.

Genomic screening for Chlamydophila pneumoniae-specific antigens using serum samples from patients with primary infection.

Chlamydophila pneumoniae, an obligate intracellular human pathogen, causes respiratory tract infections. The most common techniques used for the serological diagnosis of C. pneumoniae infections are microimmunofluorescence tests and commercial serological ELISA tests; these are based on the detection of antibodies against whole chlamydial elementary bodies and lipopolysaccharide/outer membrane protein, respectively. Identification of more specific and highly immunodominant antigens is essential for the development of new serodiagnostic assays. To identify novel specific antigens from C. pneumoniae, we screened 455 genes with unknown function in the genome of C. pneumoniae J138. Extracts of Saccharomyces cerevisiae cells expressing GFP-tagged C. pneumoniae proteins were subjected to Western blot analysis using serum samples from C. pneumoniae-infected patients as the primary antibodies. From this comprehensive analysis, 58 clones expressing C. pneumoniae open reading frames, including hypothetical proteins, were identified as antigens. These results have provided useful information for the development of new serological tools for the diagnosis for C. pneumoniae infections and for the development of vaccines in future.

Heat shock protein 10 of Chlamydophila pneumoniae induces proinflammatory cytokines through Toll-like receptor (TLR) 2 and TLR4 in human monocytes THP-1.

Inflammatory response is the first line of infection. Previous studies have suggested that Chlamydophila pneumoniae heat shock protein (CHSP) 60 is present in human atheromata, and it plays an important role on the chronic infection elicited by C. pneumoniae. Here, we demonstrated in vitro the impact of heat shock protein 10 (HSP10) of C. pneumoniae on THP-1 cells and the role of Toll-like receptors (TLRs) in the procedures of inflammatory response. The production of proinflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, and IL-1beta were induced by recombinant HSP10 dose-dependently, and the proinflammatory activity of HSP10 was greatly reduced by heating and deproteinization treatment. The expression of TLR4 and TLR2 on the cultured cells were determined by reverse transcriptase-polymerase chain reaction and immunofluorescence. Peritoneal macrophages isolated from wild-type (C3H/HeN) and TLR4-deficient mice (C3H/HeJ) were respectively stimulated with endotoxin-free proteins. Cytokine responses after stimulation were significantly different, depending on the presence of TLR4. The effect on cytokine expression was blocked by anti-TLR2 or anti-TLR4 MAb partially or dramatically. Thus, HSP10 of C. pneumoniae which could elicit inflammatory reactions in human monocytes may contribute to the inflammatory processes in Chlamydophila infection, and the effects were mediated by TLR4 and, to a lesser extent, TLR2.

Scc1 (CP0432) and Scc4 (CP0033) function as a type III secretion chaperone for CopN of Chlamydia pneumoniae.

The Chlamydia pneumoniae CopN protein is a member of the YopN/TyeA/InvE/MxiC family of secreted proteins that function to regulate the secretion of type III secretion system (T3SS) translocator and effector proteins. In this study, the Scc1 (CP0432) and Scc4 (CP0033) proteins of C. pneumoniae AR-39 were demonstrated to function together as a type III secretion chaperone that binds to an N-terminal region of CopN. The Scc1/Scc4 chaperone promoted the efficient secretion of CopN via a heterologous T3SS, whereas, the Scc3 chaperone, which binds to a C-terminal region of CopN, reduced CopN secretion.

Biomarker candidates of Chlamydophila pneumoniae proteins and protein fragments identified by affinity-proteomics using FTICR-MS and LC-MS/MS.

We report here an affinity-proteomics approach that combines 2D-gel electrophoresis and immunoblotting with high performance mass spectrometry to the identification of both full length protein antigens and antigenic fragments of Chlamydophila pneumoniae (C. pneumoniae). The present affinity-mass spectrometry approach effectively utilized high resolution FTICR mass spectrometry and LC-tandem-MS for protein identification, and enabled the identification of several new highly antigenic C. pneumoniae proteins that were not hitherto reported or previously detected only in other Chlamydia species, such as Chlamydia trachomatis. Moreover, high resolution affinity-MS provided the identification of several neo-antigenic protein fragments containing N- and C-terminal, and central domains such as fragments of the membrane protein Pmp21 and the secreted chlamydial proteasome-like factor (Cpaf), representing specific biomarker candidates.

Exploiting antigenic diversity for vaccine design: the chlamydia ArtJ paradigm.

We present an interdisciplinary approach that, by incorporating a range of experimental and computational techniques, allows the identification and characterization of functional/immunogenic domains. This approach has been applied to ArtJ, an arginine-binding protein whose orthologs in Chlamydiae trachomatis (CT ArtJ) and pneumoniae (CPn ArtJ) are shown to have different immunogenic properties despite a high sequence similarity (60% identity). We have solved the crystallographic structures of CT ArtJ and CPn ArtJ, which are found to display a type II transporter fold organized in two α-ß domains with the arginine-binding region at their interface. Although ArtJ is considered to belong to the periplasm, we found that both domains contain regions exposed on the bacterial surface. Moreover, we show that recombinant ArtJ binds to epithelial cells in vitro, suggesting a role for ArtJ in host-cell adhesion during Chlamydia infection. Experimental epitope mapping and computational analysis of physicochemical determinants of antibody recognition revealed that immunogenic epitopes reside mainly in the terminal (D1) domain of both CPn and CT ArtJ, whereas the surface properties of the respective binding-prone regions appear sufficiently different to assume divergent immunogenic behavior. Neutralization assays revealed that sera raised against CPn ArtJ D1 partially reduce both CPn and CT infectivity in vitro, suggesting that functional antibodies directed against this domain may potentially impair chlamydial infectivity. These findings suggest that the approach presented here, combining functional and structure-based analyses of evolutionary-related antigens can be a valuable tool for the identification of cross-species immunogenic epitopes for vaccine development.

Production and purification of low calcium response protein H of Chlamydophila pneumoniae.

Chlamydophila pneumoniae possesses a type III secretion system (TTSS), which allows the bacteria to secrete effector molecules into the inclusion membrane and into the cytosol of the host cell. Low calcium response protein H (LcrH), as a part of the TTSS, is a chaperone protein expressed from the middle to late stages of the chlamydial developmental cycle. Gene of LcrH (CPn0811) in a 6His-tagged form was cloned from C. pneumoniae CWL029, expressed and purified from Escherichia coli using the HIS-select TALON CellThru Resin. The purity was checked with mass spectrometry. The samples were used for immunization of BALB/c mice. The inducible E. coli clone, which over-expresses the chlamydial LcrH, permits the study of the biological properties of this protein.

Chlamydophila pneumoniae HflX belongs to an uncharacterized family of conserved GTPases and associates with the Escherichia coli 50S large ribosomal subunit.

Predicted members of the HflX subfamily of phosphate-binding-loop guanosine triphosphatases (GTPases) are widely distributed in the bacterial kingdom but remain virtually uncharacterized. In an attempt to understand mechanisms used for regulation of growth and development in the chlamydiae, obligate intracellular and developmentally complex bacteria, we have begun investigations into chlamydial GTPases; we report here what appears to be the first analysis of a HflX family GTPase using a predicted homologue from Chlamydophila pneumoniae. In agreement with phylogenetic predictions for members of this GTPase family, purified recombinant Cp. pneumoniae HflX was specific for guanine nucleotides and exhibited a slow intrinsic GTPase activity when incubated with [gamma-(32)P]GTP. Using HflX-specific monoclonal antibodies, HflX could be detected by Western blotting and high-resolution confocal microscopy throughout the vegetative growth cycle of Cp. pneumoniae and, at early time points, appeared to partly localize to the membrane. Ectopic expression of Cp. pneumoniae HflX in Escherichia coli revealed co-sedimentation of HflX with the E. coli 50S large ribosomal subunit. The results of this work open up some intriguing possibilities for the role of GTPases belonging to this previously uncharacterized family of bacterial GTPases. Ribosome association is a feature shared by other important conserved GTPase families and more detailed investigations will be required to delineate the role of HflX in bacterial ribosome function.

Real-time polymerase chain reaction and laser capture microdissection: an efficient combination tool for Chlamydophila pneumoniae DNA quantification and localization of infection in atherosclerotic lesions.

Chlamydophila pneumoniae has been implicated in atherosclerosis, but the role of this obligate intracellular pathogen in the development of the above pathology is still unclear. In particular, its presence and quantitative distribution within lesional areas has not yet been defined. We studied 18 carotid biopsies obtained from patients undergoing endoartherectomy. By laser microdissection (LCM), two different sites (intra-plaque and plaque-adjacent areas) were taken from each lesion, and the presence and quantity of the pathogen DNA were determined by real-time polymerase chain reaction (Real-time PCR). A total of 8 plaques, exclusively from patients with unstable angina, were positive in real-time PCR. The bacterial DNA was detected in both lesional areas of 3 plaques which contained the highest number of DNA copies (1,900 to 2,200 copy numbers), while C. pneumoniae DNA was detected only in the intra-plaque area of the other 5 positive (500 to 1,600 copy numbers). No C. pneumoniae DNA was found in the other 10 plaques of which 6 were from patients with unstable angina and 4 from stable angina patients. No DNA from Helicobacter pylori or Cytomegalovirus was found in any plaque. This is the first report where both the target lesion and an adjacent reference site were evaluated for the presence of C. pneumoniae DNA by the combination of LCM and Real-time PCR assays. The integration of these two methodologies offer an excellent tool for in situ studies and may help to elucidate the putative role of C. pneumoniae in atherosclerosis.

Extreme temperature tolerance of a hyperthermophilic protein coupled to residual structure in the unfolded state.

Understanding the mechanisms that dictate protein stability is of large relevance, for instance, to enable design of temperature-tolerant enzymes with high enzymatic activity over a broad temperature interval. In an effort to identify such mechanisms, we have performed a detailed comparative study of the folding thermodynamics and kinetics of the ribosomal protein S16 isolated from a mesophilic (S16(meso)) and hyperthermophilic (S16(thermo)) bacterium by using a variety of biophysical methods. As basis for the study, the 2.0 A X-ray structure of S16(thermo) was solved using single wavelength anomalous dispersion phasing. Thermal unfolding experiments yielded midpoints of 59 and 111 degrees C with associated changes in heat capacity upon unfolding (DeltaC(p)(0)) of 6.4 and 3.3 kJ mol(-1) K(-1), respectively. A strong linear correlation between DeltaC(p)(0) and melting temperature (T(m)) was observed for the wild-type proteins and mutated variants, suggesting that these variables are intimately connected. Stopped-flow fluorescence spectroscopy shows that S16(meso) folds through an apparent two-state model, whereas S16(thermo) folds through a more complex mechanism with a marked curvature in the refolding limb indicating the presence of a folding intermediate. Time-resolved energy transfer between Trp and N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-yl)methyl iodoacetamide of proteins mutated at selected positions shows that the denatured state ensemble of S16(thermo) is more compact relative to S16(meso). Taken together, our results suggest the presence of residual structure in the denatured state ensemble of S16(thermo) that appears to account for the large difference in quantified DeltaC(p)(0) values and, in turn, parts of the observed extreme thermal stability of S16(thermo). These observations may be of general importance in the design of robust enzymes that are highly active over a wide temperature span.

The intermediate domain defines broad nucleotide selectivity for protein folding in Chlamydophila GroEL1.

The chaperonin GroEL assists protein folding in the presence of ATP and magnesium through substrate protein capsulation in combination with the cofactor GroES. Recent studies have revealed the details of folding cycles of GroEL from Escherichia coli, yet little is known about the GroEL-assisted protein folding mechanisms in other bacterial species. Using three model enzyme assays, we have found that GroEL1 from Chlamydophila pneumoniae, an obligate human pathogen, has a broader selectivity for nucleotides in the refolding reaction. To elucidate structural factors involved in such nucleotide selectivity, GroEL chimeras were constructed by exchanging apical, intermediate, and equatorial domains between E. coli GroEL and C. pneumoniae GroEL1. In vitro folding assays using chimeras revealed that the intermediate domain is the major contributor to the nucleotide selectivity of C. pneumoniae GroEL1. Additional site-directed mutation experiments led to the identification of Gln(400) and Ile(404) in the intermediate domain of C. pneumoniae GroEL1 as residues that play a key role in defining the nucleotide selectivity of the protein refolding reaction.

[Application of the recombinant protein MOMP(VD2-VD3) from Chlamydia pneumoniae in sero diagnosis].

To express the recombinant protein MOMP(VD2-VD3) of Chlamydia pneumoniae, and research on the immunocompetence of the MOMP(VD2-VD3) to support serodiagnosis,PCR and gene recombinant technique was used to clone the targeted DNA fragment from a strain AR-39. The recombinant plasmid was induced in E. coli BL21 after having constructed the prokaryotic expression system, then the immunocompetence of the expression product was analyzed by Western blot and indirected ELISA which is based on the animal experimentation. A group of control sera and 126 sera from patients with coronary heart disease were examined by using ELISAs based on the recombinant protein (MOMP(VD2-VD3), and then the results were evaluated comparing with a commercial ELISAs kit. The results of the Western blot and indirected ELISA showed ompA(VD2-VD3) gene inserted in pET30a could express a recombinant protein with the molecular weight of 24kDa in BL21 and specifically reacted with the antibodies against the MOMP. Specific humoral response was elicited after immune the BALB/c mouse with protein and the specific antibody titer was more than 1:20480. Using a panel of control sera, the participation of the recombinant antigen, the sensitivity and the specificity of the indirected ELISAs were 100% respectively. Comparisons between two methods in detecting 126 sero samples, the concordance of two tests was 96.3%. The results reported here show that the recombinant protein with excellent immunocompetence could benefit the research on the serodiagnosis to Chlamydia pneumoniae.

Characterization of hypothetical proteins Cpn0146, 0147, 0284 & 0285 that are predicted to be in the Chlamydia pneumoniae inclusion membrane.

BACKGROUND: Although more than 100 Chlamydia pneumoniae hypothetical proteins have been predicted to be inclusion membrane proteins, only a few have been experimentally demonstrated to be in the inclusion membrane. Using antibodies raised with fusion proteins, we characterized four such hypothetical proteins encoded by two gene clusters (Cpn0146-147 and Cpn0284-285) in the C. pneumoniae genome. RESULTS: Cpn0146 and 0147 were detected in the inclusion membrane while Cpn0284 and 0285 inside inclusion and mainly associated with reticulate bodies although all four proteins contain an N-terminal bi-lobed hydrophobic region, a signature motif assigned to inclusion membrane proteins. These four hypothetical proteins were only detected in cells infected with C. pneumoniae but not other chlamydial species, with Cpn0147 at 6 hours and Cpn0146, 0284 & 0285 at 24 hours after infection. Cpn0146 & 147 but not Cpn0284 and 285 co-localized with a host cell endoplasmic reticulum marker, a property known to be possessed by some chlamydial inclusion membrane proteins, when expressed in the host cell cytosol via transgenes. However, the endoplasmic reticulum localization of the C. pneumoniae inclusion membrane proteins did not result in inhibition of the subsequent C. pneumoniae infection. CONCLUSION: The hypothetical proteins Cpn0146 & 0147 were localized in the C. pneumoniae inclusion membrane while Cpn0284 & 0285 within the inclusion although all four were predicted to be Inc proteins, suggesting the need to experimentally characterize the predicted Inc proteins.

Characterization of the hypothetical protein Cpn1027, a newly identified inclusion membrane protein unique to Chlamydia pneumoniae.

The hypothetical protein Cpn1027 was detected in the inclusion membrane of Chlamydia pneumoniae-infected cells with antibodies raised with Cpn1027 fusion proteins in an indirect immunofluorescence assay. The inclusion membrane staining by the anti-Cpn1027 antibodies co-localized with the staining of an antibody recognizing a known inclusion membrane protein designated IncA and these membrane stainings were blocked by the corresponding but not irrelevant fusion proteins. Although Cpn1027 was not predicted to be an inclusion membrane protein, it contained a bi-lobed hydrophobic domain region at its N-terminus, a signature secondary structural motif possessed by most chlamydial inclusion membrane proteins. The Cpn1027 protein was detected as early as 12 h after C. pneumoniae infection and remained in the inclusion membrane throughout the rest of the infection cycle. Cytosolic expression of Cpn1027 via a transgene failed to affect the subsequent chlamydial infection. The anti-Cpn1027 polyclonal antisera failed to detect any significant signals in cells infected with chlamydial species other than C. pneumoniae, which is consistent with the sequence analysis result that no significant homologues of Cpn1027 were found in any other species. These experiments together have demonstrated that Cpn1027 is a newly identified inclusion membrane protein unique to C. pneumoniae.

Chlamydial lipopolysaccharide is present in serum during acute coronary syndrome and correlates with CRP levels.

Infections, Chlamydia pneumoniae as a major candidate, have been suggested to participate in inflammatory processes ultimately leading to atherosclerosis. In the present study we measured serum levels of chlamydial lipopolysaccharide (cLPS) and highly sensitive C-reactive protein (hsCRP) in the acute coronary syndrome (ACS) patients (n=145). During ACS, both cLPS and hsCRP were elevated and significant correlation (P=0.003, r=0.25) between them was observed. Both cLPS and hsCRP levels decreased after the event and correlation remained significant during the follow-up period. Our results suggest that cLPS is liberated from the damaged tissue persistently infected with C. pneumoniae during the ACS event. The significant correlation between cLPS and hsCRP levels further point to the possibility that both levels reflect the magnitude of tissue damage.