Chlamydial virulence determinants in atherogenesis: the role of chlamydial lipopolysaccharide and heat shock protein 60 in macrophage-lipoprotein interactions

Abiotrophia defectiva DnaK Promotes Fibronectin-Mediated Adherence to HUVECs and Induces a Proinflammatory Response

Abiotrophia defectiva is a nutritionally variant streptococci that is found in the oral cavity, and it is an etiologic agent of infective endocarditis. We have previously reported the binding activity of A. defectiva to fibronectin and to human umbilical vein endothelial cells (HUVECs). However, the contribution of some adhesion factors on the binding properties has not been well delineated. In this study, we identified DnaK, a chaperon protein, as being one of the binding molecules of A. defectiva to fibronectin. Recombinant DnaK (rDnaK) bound immobilized fibronectin in a concentration-dependent manner, and anti-DnaK antiserum reduced the binding activity of A. defectiva with both fibronectin and HUVECs. Furthermore, DnaK were observed on the cell surfaces via immune-electroscopic analysis with anti-DnaK antiserum. Expression of IL-8, CCL2, ICAM-1, and VCAM-1 was upregulated with the A. defectiva rDnaK treatment in HUVECs. Furthermore, TNF-α secretion of THP-1 macrophages was also upregulated with the rDnaK. We observed these upregulations in rDnaK treated with polymyxin B, but not in the heat-treated rDnaK. The findings show that A. defectiva DnaK functions not only as an adhesin to HUVECs via the binding to fibronectin but also as a proinflammatory agent in the pathogenicity to cause infective endocarditis.

Deep sequencing reveals the skewed B-cell receptor repertoire in plaques and the association between pathogens and atherosclerosis

The immune/inflammatory responses regulated by B cells are the critical determinants of atherosclerosis. B-cell receptor (BCR) plays pivotal roles in regulating B cell function. However, the composition and molecular characteristics of the BCR repertoire in atherosclerotic patients have not been fully elucidated. Herein we analyzed BCR repertoire in circulation and plaques of atherosclerotic patients by sequencing the BCR heavy chain complement determining region 3 (BCRH CDR3). Our data showed that in plaques, BCR repertoire was dramatically skewed and their combinations and diversity were significantly decreased, while the frequency of public and dominant B-cell clones was markedly increased. Additionally, BCRH CDR3 in plaques had higher positive selection pressure than that in the peripheral blood of normal subjects and atherosclerotic patients. Moreover, the BCRH CDR3 of some B cell clones specifically expanded in plaques were similar to that of antibodies which recognized certain pathogens including Influenza A virus, implying the possibility of the association between pathogens and atherosclerosis. The present study contributed to understand the roles of B cells in atherosclerosis. The design of specific antibodies based on the B cell clones specifically expanded in plaques might yield useful tools to reveal the pathogenesis of atherosclerosis, assess or alleviate the progression of atherosclerosis.

Comparative genomic analysis of Myroides odoratimimus isolates

Myroides odoratimimus is an important nosocomial pathogen. Management of M. odoratimimus infection is difficult owing to the multidrug resistance and the unknown pathogenesis mechanisms. Based on our previous genomic sequencing data of M. odoratimimus PR63039 (isolated from a patient with the urinary tract infection), in this study, we further performed comparative genomic analysis for 10 selected Myroides strains. Our results showed that these Myroides genome contexts were very similar and phylogenetically related. Various prophages were identified in the four clinical isolate genomes, which possibly contributed to the genome evolution among the Myroides strains. CRISPR elements were only detected in the two clinical (PR63039 and CCUG10230) isolates and two environmental (CCUG12700 and H1bi) strains. With more stringent cutoff parameters in CARD analysis, the four clinical M. odoratimimus contained roughly equal antibiotic resistance genes, indicating their similar antibiotic resistance profiles. The three clinical (CCUG10230, CCUG12901, CIP101113) and three environmental (CCUG12700, L41, H1bi) M. odoratimimus strains were speculated to carry the indistinguishable virulent factors (VFs), which may involve in the similar pathogenesis mechanism. Moreover, some VFs might confer to the high capacity of dissemination, attacking tissue cells and induction of autoimmune complications. Our results facilitate the research of antibiotic resistance and the development of therapeutic regimens for the M. odoratimimus infections.

Inhibitors of Apoptosis Protein Antagonists (Smac Mimetic Compounds) Control Polarization of Macrophages during Microbial Challenge and Sterile Inflammatory Responses

Apoptosis is a physiological cell death process essential for development, tissue homeostasis, and for immune defense of multicellular animals. Inhibitors of apoptosis proteins (IAPs) regulate apoptosis in response to various cellular assaults. Using both genetic and pharmacological approaches we demonstrate here that the IAPs not only support opportunistic survival of intracellular human pathogens like Chlamydia pneumoniae but also control plasticity of iNOS+ M1 macrophage during the course of infection and render them refractory for immune stimulation. Treatment of Th1 primed macrophages with birinapant (IAP-specific antagonist) inhibited NO generation and relevant proteins involved in innate immune signaling. Accordingly, birinapant promoted hypoxia, angiogenesis, and tumor-induced M2 polarization of iNOS+ M1 macrophages. Interestingly, birinapant-driven changes in immune signaling were accompanied with changes in the expression of various proteins involved in the metabolism, and thus revealing the new role of IAPs in immune metabolic reprogramming in committed macrophages. Taken together, our study reveals the significance of IAP targeting approaches (Smac mimetic compounds) for the management of infectious and inflammatory diseases relying on macrophage plasticity.

Microevolutionary traits and comparative population genomics of the emerging pathogenic fungus Cryptococcus gattii

Emerging fungal pathogens cause an expanding burden of disease across the animal kingdom, including a rise in morbidity and mortality in humans. Yet, we currently have only a limited repertoire of available therapeutic interventions. A greater understanding of the mechanisms of fungal virulence and of the emergence of hypervirulence within species is therefore needed for new treatments and mitigation efforts. For example, over the past decade, an unusual lineage of Cryptococcus gattii, which was first detected on Vancouver Island, has spread to the Canadian mainland and the Pacific Northwest infecting otherwise healthy individuals. The molecular changes that led to the development of this hypervirulent cryptococcal lineage remain unclear. To explore this, we traced the history of similar microevolutionary events that can lead to changes in host range and pathogenicity. Here, we detail fine-resolution mapping of genetic differences between two highly related Cryptococcus gattii VGIIc isolates that differ in their virulence traits (phagocytosis, vomocytosis, macrophage death, mitochondrial tubularization and intracellular proliferation). We identified a small number of single site variants within coding regions that potentially contribute to variations in virulence. We then extended our methods across multiple lineages of C. gattii to study how selection is acting on key virulence genes within different lineages.This article is part of the themed issue 'Tackling emerging fungal threats to animal health, food security and ecosystem resilience'.

Signaling events in pathogen-induced macrophage foam cell formation

Macrophage foam cell formation is a key event in atherosclerosis. Several triggers induce low-density lipoprotein (LDL) uptake by macrophages to create foam cells, including infections with Porphyromonas gingivalis and Chlamydia pneumoniae, two pathogens that have been linked to atherosclerosis. While gene regulation during foam cell formation has been examined, comparative investigations to identify shared and specific pathogen-elicited molecular events relevant to foam cell formation are not well documented. We infected mouse bone marrow-derived macrophages with P. gingivalis or C. pneumoniae in the presence of LDL to induce foam cell formation, and examined gene expression using an atherosclerosis pathway targeted plate array. We found over 30 genes were significantly induced in response to both pathogens, including PPAR family members that are broadly important in atherosclerosis and matrix remodeling genes that may play a role in plaque development and stability. Six genes mainly involved in lipid transport were significantly downregulated. The response overall was remarkably similar and few genes were regulated in a pathogen-specific manner. Despite very divergent lifestyles, P. gingivalis and C. pneumoniae activate similar gene expression profiles during foam cell formation that may ultimately serve as targets for modulating infection-elicited foam cell burden, and progression of atherosclerosis.

Toll-like receptors mediating vascular malfunction: Lessons from receptor subtypes

Toll-like receptors (TLR) are a subfamily of pattern recognition receptors (PRR) implicated in a variety of vascular abnormalities. However, the pathophysiological role and the interplay between different TLR-mediated innate and adaptive immune responses during the development of vascular diseases remain largely unspecified. TLR are widely distributed in both immune and nonimmune cells in the blood vessel wall. The expressions and locations of TLR are dynamically regulated in response to distinct molecular patterns derived from pathogens or damaged host cells. As a result, the outcome of TLR signaling is agonist- and cell type-dependent. A better understanding of discrete TLR signaling pathways in the vasculature will provide unprecedented opportunities for the discovery of novel therapies in many inflammatory vascular diseases. The present brief review discusses the role of individual TLR in controlling cellular functions of the vascular system, by focusing on the inflammatory responses within the blood vessel wall which contribute to the development of hypertension and atherosclerosis.

Distinct gene signatures in aortic tissue from ApoE-/- mice exposed to pathogens or Western diet

Background

Atherosclerosis is a progressive disease characterized by inflammation and accumulation of lipids in vascular tissue. Porphyromonas gingivalis (Pg) and Chlamydia pneumoniae (Cp) are associated with inflammatory atherosclerosis in humans. Similar to endogenous mediators arising from excessive dietary lipids, these Gram-negative pathogens are pro-atherogenic in animal models, although the specific inflammatory/atherogenic pathways induced by these stimuli are not well defined. In this study, we identified gene expression profiles that characterize P. gingivalis, C. pneumoniae, and Western diet (WD) at acute and chronic time points in aortas of Apolipoprotein E (ApoE^-/-) mice.

Results

At the chronic time point, we observed that P. gingivalis was associated with a high number of unique differentially expressed genes compared to C. pneumoniae or WD. For the top 500 differentially expressed genes unique to each group, we observed a high percentage (76%) that exhibited decreased expression in P. gingivalis-treated mice in contrast to a high percentage (96%) that exhibited increased expression in WD mice. C. pneumoniae treatment resulted in approximately equal numbers of genes that exhibited increased and decreased expression. Gene Set Enrichment Analysis (GSEA) revealed distinct stimuli-associated phenotypes, including decreased expression of mitochondrion, glucose metabolism, and PPAR pathways in response to P. gingivalis but increased expression of mitochondrion, lipid metabolism, carbohydrate and amino acid metabolism, and PPAR pathways in response to C. pneumoniae; WD was associated with increased expression of immune and inflammatory pathways. DAVID analysis of gene clusters identified by two-way ANOVA at acute and chronic time points revealed a set of core genes that exhibited altered expression during the natural progression of atherosclerosis in ApoE^-/- mice; these changes were enhanced in P. gingivalis-treated mice but attenuated in C. pneumoniae-treated mice. Notable differences in the expression of genes associated with unstable plaques were also observed among the three pro-atherogenic stimuli.

Conclusions

Despite the common outcome of P. gingivalis, C. pneumoniae, and WD on the induction of vascular inflammation and atherosclerosis, distinct gene signatures and pathways unique to each pro-atherogenic stimulus were identified. Our results suggest that pathogen exposure results in dysregulated cellular responses that may impact plaque progression and regression pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1176) contains supplementary material, which is available to authorized users.

Bacterial virulence in the moonlight: multitasking bacterial moonlighting proteins are virulence determinants in infectious disease

Men may not be able to multitask, but it is emerging that proteins can. This capacity of proteins to exhibit more than one function is termed protein moonlighting, and, surprisingly, many highly conserved proteins involved in metabolic regulation or the cell stress response have a range of additional biological actions which are involved in bacterial virulence. This review highlights the multiple roles exhibited by a range of bacterial proteins, such as glycolytic and other metabolic enzymes and molecular chaperones, and the role that such moonlighting activity plays in the virulence characteristics of a number of important human pathogens, including Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Helicobacter pylori, and Mycobacterium tuberculosis.

Cell resilience in species life spans: a link to inflammation?

Species differences in life span have been attributed to cellular survival during various stressors, designated here as 'cell resilience'. In primary fibroblast cultures, cell resilience during exposure to free radicals, hypoglycemia, hyperthermia, and various toxins has shown generally consistent correlations with the species characteristic life spans of birds and mammals. However, the mechanistic links of cell resilience in fibroblast cultures to different species life spans are poorly understood. We propose that certain experimental stressors are relevant to somatic damage in vivo during inflammatory responses of innate immunity, particularly, resistance to reactive oxygen species (ROS), low glucose, and hyperthermia. According to this hypothesis, somatic cell resilience determines species differences in longevity during repeated infections and traumatic injuries in the natural environment. Infections and injury expose local fibroblasts and other cells to ROS generated by macrophages and to local temperature elevations. Systemically, acute phase immune reactions cause hypoglycemia and hyperthermia. We propose that cell resilience to somatic stressors incurred in inflammation is important in the evolution of longevity and that longer-lived species are specifically more resistant to immune-related stressors. This hypothesis further specifies Kirkwood's disposable soma theory. We suggest expanding the battery of stressors and markers used for comparative studies to additional cell types and additional parameters relevant to host defense and to their ecological specificities.

Chlamydophila pneumoniae Infection and Its Role in Neurological Disorders

Chlamydophila pneumoniae is an intracellular pathogen responsible for a number of different acute and chronic infections. The recent deepening of knowledge on the biology and the use of increasingly more sensitive and specific molecular techniques has allowed demonstration of C. pneumoniae in a large number of persons suffering from different diseases including cardiovascular (atherosclerosis and stroke) and central nervous system (CNS) disorders. Despite this, many important issues remain unanswered with regard to the role that C. pneumoniae may play in initiating atheroma or in the progression of the disease. A growing body of evidence concerns the involvement of this pathogen in chronic neurological disorders and particularly in Alzheimer's disease (AD) and Multiple Sclerosis (MS). Monocytes may traffic C. pneumoniae across the blood-brain-barrier, shed the organism in the CNS and induce neuroinflammation. The demonstration of C. pneumoniae by histopathological, molecular and culture techniques in the late-onset AD dementia has suggested a relationship between CNS infection with C. pneumoniae and the AD neuropathogenesis. In particular subsets of MS patients, C. pneumoniae could induce a chronic persistent brain infection acting as a cofactor in the development of the disease. The role of Chlamydia in the pathogenesis of mental or neurobehavioral disorders including schizophrenia and autism is uncertain and fragmentary and will require further confirmation.

Mycoplasma pneumoniae and/or Chlamydophila pneumoniae inoculation causing different aggravations in cholesterol-induced atherosclerosis in apoE KO male mice

BACKGROUND

Chamydophila pneumoniae (CP) and/or Mycoplasma pneumoniae (MP) are two bacteria detected in vulnerable atheromas. In this study we aimed to analyze whether CP and/or MP aggravates atherosclerosis induced by cholesterol-enriched diet in C57BL/6 apoE KO male mice. Thirty male apoE KO mice aged eight weeks fed by a diet containing 1% cholesterol until 32 weeks of age were divided into four groups: the first was inoculated with CP (n = 7), the second with MP (n = 12), the third with both CP + MP (n = 5), and the fourth with saline (sham n = 6). The animals were re-inoculated at 36 weeks of age, and sacrificed at 40 weeks of age. Two ascending aorta and one aortic arch segments were sampled. In the most severely obstructed segment, vessel diameter, plaque height, percentage of luminal obstruction and the degree of adventitial inflammation were analyzed. The plaque area/intimal surface ratio was obtained by measuring all three segments. The adventitial inflammation was semiquantified (0 absent, 1 mild, 2 moderate, and 3 diffuse).

RESULTS

The mean and standard deviation of plaque height, % luminal obstruction, external diameter, the plaque area/intimal surface ratio and the adventitial inflammation values are the following for each group: MP (0.20 +/- 0.12 mm, 69 +/- 26%, 0.38 +/- 0.11 mm, 0.04 +/- 0.04 and 0.22 +/- 0.67), CP (0.23 +/- 0.08 mm, 90 +/- 26%, 0.37 +/- 0.08 mm, 0.04 +/- 0.03, and 0.44 +/- 0.53), MP + CP (18 +/- 0.08 mm, 84 +/- 4.0%, 0.35 +/- 0.25 mm, 0.03 +/- 0.03 and 1.33 +/- 0.82) and sham (0.08 +/- 0.09 mm, 42 +/- 46%, 0.30 +/- 0.10 mm, 0.02 +/- 0.03 and 0.71 +/- 0.76). A wider area of plaque/intimal surface was observed in MP + CP inoculated groups (p = 0.07 and 0.06) as well as an increased plaque height in CP (p = 0.01) in comparison with sham group. There was also an increased luminal obstruction (p = 0.047) in CP inoculated group in comparison to sham group. Adventitial inflammation in MP + CP inoculated group was higher than MP, CP and the sham groups (p = 0.02).

CONCLUSION

Inoculation of CP, MP or both agents in C57BL/6 apoE KO male mice caused aggravation of experimental atherosclerosis induced by cholesterol-enriched diet, with distinct characteristics. CP inoculation increased the plaque height with positive vessel remodeling and co-inoculation of MP + CP caused the highest adventitial inflammation measures.

Chlamydia pneumoniae infection in patients after kidney transplantation treated with spiramycin

INTRODUCTION

Previous research has pointed to a role of Chlamydia pneumoniae infection in the development of chronic renal allograft dysfunction, chronic liver rejection, and vasculopathy in the transplanted heart. The aim of this study was to evaluate the presence of C. pneumoniae prior to and after kidney transplantation as well as to determine the role of spiramycin therapy among kidney transplant recipients.

MATERIALS AND METHODS

The study group consisted of 50 patients (25 pairs) who received kidney transplants from cadaveric donors. One of the 2 kidneys from a donor was transplanted to a patient randomized to spiramycin (2 x 3 million U/d orally for 3 months; group S) and the other to a patient assigned as control (group C). Markers of infection were assessed on day 1 posttransplantation and 3 months later (average, 94 days). All 50 patients were examined for the presence of bacterial DNA in peripheral blood leukocytes using real-time polymerase chain reaction (PCR) and for titers of serum anti C. pneumoniae immunoglobulin (IgG) and IgA antibodies using microimmunofluorescence (MIF). C. pneumoniae infection was diagnosed by the presence of C. pneumoniae DNA in peripheral blood leukocytes or positive antibodies of both classes.

RESULTS

C. pneumoniae infection was initially diagnosed in 14 patients among group S and 8 patients among group C (P = not significant [ns]) and after 3 months in 12 and 9 patients, respectively (P = ns). Conversion from positive to negative C. pneumoniae status occured in 7 patients among group S and 1 patient among group C (P = .04). Conversion from negative to positive C. pneumoniae status occured in 5 patients from group S and 2 patients from group C (P = ns).

CONCLUSIONS

These results suggest a possible role for spiramycin treatment of C pneumoniae infection in kidney allograft recipients. C. pneumoniae infection diagnosis and treatment should be considered to be routine for every patient awaiting transplantation.

Chlamydia pneumoniae-induced foam cell formation requires MyD88-dependent and -independent signaling and is reciprocally modulated by liver X receptor activation

Chlamydia pneumoniae is detected by macrophages and other APCs via TLRs and can exacerbate developing atherosclerotic lesions, but how that occurs is not known. Liver X receptors (LXRs) centrally control reverse cholesterol transport, but also negatively modulate TLR-mediated inflammatory pathways. We isolated peritoneal macrophages from wild-type, TLR2, TLR3, TLR4, TLR2/4, MyD88, TRIF, MyD88/TRIF, and IFN regulatory factor 3 (IRF3) KO mice, treated them with live or UV-killed C. pneumoniae in the presence or absence of oxidized LDL, then measured foam cell formation. In some experiments, the synthetic LXR agonist GW3965 was added to macrophages infected with C. pneumoniae in the presence of oxidized LDL. Both live and UV-killed C. pneumoniae induced IRF3 activation and promoted foam cell formation in wild-type macrophages, whereas the genetic absence of TLR2, TLR4, MyD88, TRIF, or IRF3, but not TLR3, significantly reduced foam cell formation. C. pneumoniae-induced foam cell formation was significantly reduced by the LXR agonist GW3965, which in turn inhibited C. pneumoniae-induced IRF3 activation, suggesting a bidirectional cross-talk. We conclude that C. pneumoniae facilitates foam cell formation via activation of both MyD88-dependent and MyD88-independent (i.e., TRIF-dependent and IRF3-dependent) pathways downstream of TLR2 and TLR4 signaling and that TLR3 is not involved in this process. This mechanism could at least partly explain why infection with C. pneumoniae accelerates the development of atherosclerotic plaque and lends support to the proposal that LXR agonists might prove clinically useful in suppressing atherogenesis.

Amalgamation of Chlamydia pneumoniae inclusions with lipid droplets in foam cells in human atherosclerotic plaque

Chlamydia pneumoniae (Chlamydophila pneumoniae) infect macrophages and accelerates foam cell formation in in vitro experiments, but whether this might occur in human atherosclerosis is unknown. In the present study, we examined 17 carotid artery segments, obtained by endarterectomy, in which the presence of C. pneumoniae was confirmed by both polymerase chain reaction and immunohistochemistry. Electron microscopy demonstrated the presence of structures with the appearance of elementary, reticulate and aberrant bodies of C. pneumoniae in the cytoplasm of macrophage foam cells. The volume of the cytoplasm that was free from vacuoles and lipid droplets in C. pneumoniae-infected foam cells was dramatically reduced, and a phenomenon of the amalgamation of C. pneumoniae inclusions with lipid droplets was detected. Double immunohistochemistry showed that C. pneumoniae-infected foam cells contained a large number of oxidized low-density lipoproteins. The observations provide support to the hypothesis that C. pneumoniae could affect foam cell formation in human atherosclerosis.

Microbial risk factors of cardiovascular and cerebrovascular diseases: potential therapeutical options

Infection and inflammation may have a crucial role in the pathogenesis of atherosclerosis. This hypothesis is supported by an increasing number of reports on the interaction between chronic infection, inflammation, and atherogenesis. Assessment of serological and inflammatory markers of infection may be useful adjuncts in identifying those patients who are at a higher risk of developing vascular events, and in whom more aggressive treatments might be warranted.

Retinoic acid inhibits the infectivity and growth of Chlamydia pneumoniae in epithelial and endothelial cells through different receptors

Chlamydia pneumoniae is a human respiratory pathogen that has also been associated with cardiovascular disease. C. pneumoniae infection accelerates atherosclerotic plaque development in hyperlipidemic animals and promotes oxidation of low density lipoprotein in vitro. All-trans-retinoic acid (ATRA), an antioxidant, has been shown to inhibit C. pneumoniae infectivity for endothelial cells by preventing binding of the organism to the M6P/IGF2 receptor on the cell surface. This current study investigates whether ATRA similarly affects C. pneumoniae infectivity of epithelial cells, which are the primary site of infection in the respiratory tract, and the effects on intracellular growth in both endothelial and epithelial cells. Because ATRA binds to both the nuclear retinoid acid receptor (RAR) and the M6P/IGF2 receptor, 4-[(E)-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1-propenyl]benzoic acid (TTNPB), an ATRA analog, which binds to the RAR but not the M6P/IGF2 receptor was used to differentiate the receptor mediating the effects of ATRA. The results of this study showed two separate effects of ATRA. The first effect is through interaction with the M6P/IGF2 receptor on the cell surface preventing attachment of the organism (inhibition by ATRA but not TTNPB) in endothelial cells and the second is through the nuclear receptor (inhibition by both ATRA and TTNPB) which inhibits growth in both epithelial and endothelial cells.

Chlamydial Hsp60-2 is iron responsive in Chlamydia trachomatis serovar E-infected human endometrial epithelial cells in vitro

Chlamydial 60-kDa heat shock proteins (cHsp60s) are known to play a prominent role in the immunopathogenesis of disease. It is also known that several stress-inducing growth conditions, such as heat, iron deprivation, or exposure to gamma interferon, result in the development of persistent chlamydial forms that often exhibit enhanced expression of cHsp60. We have shown previously that the expression of cHsp60 is greatly enhanced in Chlamydia trachomatis serovar E propagated in an iron-deficient medium. The objective of this work was to determine which single cHsp60 or combination of the three cHsp60 homologs encoded by this organism responds to iron limitation. Using monospecific polyclonal peptide antisera that recognize only cHsp60-1, cHsp60-2, or cHsp60-3, we found that expression of cHsp60-2 is responsive to iron deprivation. Overall, our studies suggest that the expression of cHsp60 homologs differs among the mechanisms currently known to induce persistence.

Chlamydia pneumoniae--induced macrophage foam cell formation is mediated by Toll-like receptor 2

Chlamydia pneumoniae induces macrophage foam cell formation, a hallmark of early atherosclerosis, in the presence of low-density lipoprotein (LDL). This study examined the role that Toll-like receptor 2 (TLR2) and TLR4 may play in pathogen-induced foam cell formation. Murine macrophage RAW 264.7 cells either infected with C. pneumoniae or treated with the TLR4 ligand E. coli lipopolysaccharide (LPS) or the TLR2 ligand Pam(3)-Cys-Ala-Gly-OH (Pam) became Oil Red O-stained foam cells and showed increased cholesteryl ester (CE) content when cocultured with LDL. In macrophages from TLR2(-/-) mice, foam cells were induced by Escherichia coli LPS but not by C. pneumoniae or Pam. Conversely, C. pneumoniae or Pam, but not E. coli LPS, induced foam cells in the TLR4-deficient GG2EE macrophage cell line, suggesting that C. pneumoniae elicits foam cell formation predominantly via TLR2. Enhancing cholesterol efflux using the liver X receptor (LXR) agonist GW3965 significantly decreased the CE content of cells exposed to each of the three TLR ligands (C. pneumoniae, Pam, and E. coli LPS). Overall, our results suggest that activation of the LXR signaling pathway may affect potentially atherogenic processes modulated by the TLR ligands.

Successful removal of Chlamydia pneumoniae from plateletpheresis products collected using automated leukoreduction hemapheresis techniques

Chlamydia pneumoniae (Cp) is an obligate intracellular pathogen associated with a variety of maladies. Best known for its involvement in community-acquired pneumonia outbreaks; the potential role of Cp in diverse illnesses is a topic of increasing interest and investigation. Previous studies suggested that white blood cells from normal blood donors harboring this agent may be eliminated through leukoreduction by filtration. Here we examine the ability and efficacy of apheresis-related leukoreduction for its effect on the carriage and potential infectivity of these organisms in the preparation of platelet products. Matched pre-apheresis peripheral blood (PB) samples and product samples obtained from healthy plateletpheresis donors were analyzed for the presence and potential infectivity of Cp organisms by direct smear inspection and tissue culture techniques. Antibody seroreactivity directed towards the organism was assessed using a solid phase immunoassay. Forty-eight percent of the donor blood samples exhibited elevated anti-Cp antibody titers (> or =200). Specimens from 31 (27%) and 34 (30%) of 115 plateletpheresis donors were positive for the presence of Cp organisms in their pre-apheresis PB samples when analyzed by direct smear examination and culture, respectively. Examination of the 115 post-leukodepleted plateletpheresis product samples revealed only two (1.7%) and one (0.009%) product(s) to be smear-positive and culture-positive, respectively. Certain plateletpheresis donors may harbor infectious Cp organisms in circulating WBC. Collections from such donors of apheresis platelet products using standard apheresis leukoreduction strategies appear successful in markedly decreasing or eliminating the organisms found in the final products.

Descripción de inmunógenos de Chlamydia pneumoniae reconocidos por el suero de sujetos con enfermedad arterial periférica

BACKGROUND AND OBJECTIVE

The relationship between antibodies to C. pneumoniae and presence of the bacteria was studied in individuals with peripheral arterial disease.

PATIENTS AND METHOD

An observational analytical, case-control study was performed in 118 patients (68 cases, 50 controls) to investigate immunoglobulin (Ig) G and A against C. pneumoniae in serum, using Western-blot (commercial and no commercial methods), ELISA and MIF; DNA of the bacteria in vascular tissue biopsy specimens was studied by polymerase chain reaction.

RESULTS

Using commercial Western-blot, significant presence of IgG anti-39 kDa and anti-54 kDa was found in cases and was related to MIF results and C. pneumoniae DNA findings; IgA anti-LPS, anti-92 kDa and anti-Hsp60 kDa were also found and related to DNA presence. Using no commercial Western-blot, significant presence of 128.8 and 9.2 kDa bands for IgG was detected in cases and associated with DNA presence; 70.8, 58.9, 47.9, 47.5, 18.4, 12.1, 10.6, 8.1, and 7.6 kDa bands for IgG were found in cases; and DNA was present when 54.6 and 1.1 kDa bands for IgG and 79.4, 50.1, and 18.4 kDa bands for IgA were also detected.

CONCLUSIONS

Using Western-blot, a greater serologic response was found against certain proteins of the bacteria in individuals with peripheral arterial disease. This may reflect an initial stage with presence of DNA and specific IgG. Subsequently, even in absence of the bacteria, an immunomediated disease may develop with presence of IgA and IgG.

Diagnostic value of an ELISA using a recombinant 54-kDa species-specific protein from Chlamydia pneumoniae

The aim of this study was to evaluate a 54-kDa recombinant protein encoded by the CPn0980 gene for use in a Chlamydia pneumoniae-specific ELISA. The ability of this affinity-purified protein to detect C. pneumoniae-specific antibodies was evaluated with a panel of 105 serum samples from 62 patients with community-acquired pneumonia. The results of this assay were compared with those obtained with a direct PCR-based detection assay and an outer-membrane complex-based immunoassay. The 54-kDa protein induced specific antibodies following infection of humans, and the recombinant 54-kDa ELISA detected anti-C. pneumoniae IgG and/or IgM antibodies with a sensitivity of 66.7% and a specificity of 79.2% compared with the direct PCR-based detection assay.

Inflammation and Atherosclerosis

PURPOSE

The aim of this article is to discuss the role of inflammation in atherosclerosis.

SUMMARY

An initial chemical, mechanical or immunological insult induces endothelial dysfunction. This triggers a cascade of inflammatory reactions, in which monocytes, macrophages, T lymphocytes and vascular smooth muscle cells participate. Leukocyte adhesion molecules, cytokines, growth factors and metalloproteinases participate in all stages of atherogenesis. Almost all of the traditional risk factors for atherosclerosis are associated with and participate in the inflammatory process. Many infectious agents, mainly Chlamydia pneumoniae, have been proposed as potential triggers of the cascade. The immune system has been implicated in plaque formation, through the activation of cellular and humoral immunity against innate or microbial heat shock protein 60. Methods of detection of systemic or local plaque inflammation have been developed and research is being conducted on the potential use of anti-inflammatory and antibiotic drugs in atherosclerosis.

60-kDa heat shock protein of Chlamydia pneumoniae promotes a T helper type 1 immune response through IL-12/IL-23 production in monocyte-derived dendritic cells

Infection, in particular by Chlamydia pneumoniae (Cp), has been associated with atherosclerosis and coronary heart disease. Immune reactions to heat shock proteins (HSPs) have been advocated to link infection to atherosclerosis and its acute sequelae based on molecular mimicry with host HSPs. We have here evaluated the role played by recombinant Cp-HSP60 and Cp-HSP10 for their ability to induce maturation of human monocyte-derived dendritic cells (MDDC) and T cell polarization. Cp-HSP60, but not Cp-HSP10, induced a strong MDCC maturation, as assessed by the expression of co-stimulatory molecules and other markers. Secretion of regulatory cytokines and enhancement of antigen presenting ability of mature (m)MDDC toward a clear T helper (Th) 1 pattern were also induced by Cp-HSP60. An analysis of the IL-12 cytokine family demonstrated that Cp-HSP60-matured MDDC were able to express p35 and p40 mRNA subunits to form IL-12, and p19 and p40 subunits to form IL-23. Thus, preferential Th1 polarization of immune response induced by Cp-HSP60-matured MDDC appears to be due to the concomitant expression of IL-12 and IL-23. Our data suggest that Cp-HSP60-matured DC may contribute to T-cell mediated immunopathology of atherosclerosis via a chronic stimulation of Th1 immune responses.

Low prevalence of antibodies against heat shock protein 10 of Chlamydophila pneumoniae in patients with coronary heart disease

In this study the prevalence of antibodies against the heat shock protein 10 (HSP10) of Chamydophila pneumoniae (CP) (as assessed by ELISA) in patients with coronary heart disease (CHD) and seropositive or seronegative to CP, as assessed by microimmunofluorescence (MIF), was investigated. The controls were age- and sex-matched healthy subjects. The HSP10 preparation used throughout this study was a 6-his-tagged recombinant protein preliminarily shown to be immunogenic in mice. Low level IgG reactivity against CP-HSP10 was detected in 19 out of 200 and 5 out of 100 CHD patients and controls, respectively. No IgM or IgA isotypes were found. Furthermore, there was no difference in the frequency or level of anti-HSP10 IgG between CP-positive and CP-negative sera either in patients (11/140=7.9% vs. 8/60=13%) or in healthy subjects (3/40=7.5% vs. 2/60=3.3%). Overall, our data indicate that CP-HSP10, at variance with CP-HSP60, to which it is genetically and physiologically linked, should not be regarded as a major expressed immunogen or a marker of infection by CP in CHD patients.

Interactions of oral pathogens with toll-like receptors: possible role in atherosclerosis

Toll-like receptors (TLR) function as important signal transducers that mediate innate immune and inflammatory responses to pathogens through pattern recognition of virulence molecules. Although TLRs mediate protection against infection, it is also likely that they may have a pathophysiologic role in certain inflammatory diseases, such as atherosclerosis. In atherosclerotic lesions, endothelial cells and macrophages have been shown to upregulate TLR expression and may respond to TLR agonists of microbial origin, resulting in detrimental inflammatory reactions. Some of these potential TLR-activating virulence factors may be of oral origin. The detection in atherosclerotic plaques of DNA specific for Porphyromonas gingivalis and other periodontal pathogens suggests that these pathogens disseminate into the systemic circulation and localize in atheromas. The potential of periodontal and some other oral pathogens to activate TLRs in vivo is suggested by findings from cell culture experiments on interactions of selected virulence protein adhesins with TLRs and their coreceptors. Specifically, we have shown that proinflammatory cytokine induction by P. gingivalis fimbriae was inhibited by monoclonal antibodies to TLR2, TLR4, CD14, and beta2 integrins, but not by immunoglobulin isotype controls. Cytokine induction by Bacteroides forsythus protein A depended heavily on CD14 and TLR2. We also found that the ability of Streptococcus mutans protein AgI/II to stimulate cytokine release was partially dependent on CD14 and TLR4. Moreover, P. gingivalis fimbriae induced TLR-dependent activation of nuclear factor-kappaB and upregulation of costimulatory molecules in monocytic cells. These proinflammatory activities have been implicated in the pathogenesis of periodontitis, and similar inflammatory mechanisms could potentially operate in atherosclerosis. Studies by other groups have shown that P. gingivalis is capable of stimulating low-density lipoprotein oxidation, foam cell formation, and rupture of atherosclerotic plaque through induction of matrix metalloproteinases. Interestingly, at least some of these activities can be induced by TLR agonists (lipopolysaccharide and heat-shock protein-60) from Chlamydia pneumoniae, a major risk factor in atherosclerosis. Future research in animal models and in vitro cellular systems with defined mutations in TLRs may implicate TLR participation in oral pathogen-mediated atherosclerotic processes, thereby providing a mechanistic basis for the epidemiological findings linking oral pathogens to atherosclerotic disease.

Identification of Chlamydia pneumoniae within human choroidal neovascular membranes secondary to age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness in the United States, and increasing evidence suggests that it is an inflammatory disease. The prokaryotic obligate intracellular pathogen Chlamydia pneumoniae is emerging as a novel risk factor in cardiovascular disease, and recent sero-epidemiological data suggest that C. pneumoniae infection is also associated with AMD. In this study, we examined choroidal neovascular membrane (CNV) tissue from patients with neovascular AMD for the presence of C. pneumoniae and determined whether the pathogen can dysregulate the function of key cell types in ways that can cause neovascular AMD. Nine CNV removed from patients with neovascular AMD were examined for the presence of C. pneumoniae by immunohistochemistry (IHC) and polymerase chain reaction (PCR); in addition, we performed PCR on nine non-AMD eyes, and IHC on five non-AMD CNV, seven non-AMD eyes, and one internal limiting membrane specimen. Finally, human monocyte-derived macrophages and retinal pigment epithelial (RPE) cells were exposed to C. pneumoniae and assayed in vitro for the production of pro-angiogenic immunomodulators (VEGF, IL-8, and MCP-1). C. pneumoniae was detected in four of nine AMD CNV by IHC and two of nine AMD CNV by PCR, induced VEGF production by human macrophages, and increased production of IL-8 and MCP-1 by RPE cells. In contrast, none of the 22 non-AMD specimens showed evidence for C. pneumoniae. These data indicate that a pathogen capable of inducing chronic inflammation and pro-angiogenic cytokines can be detected in some AMD CNV, and suggest that infection may contribute to the pathogenesis of AMD.

The induction of prostaglandin E synthase and upregulation of cyclooxygenase-2 by 9-cis retinoic acid

9-cis Retinoic acid (9cRA) is a promising lead compound to design the retinoid X receptor (RXR) ligands with the ability to simultaneously activate RXR heterodimers with the selectivity to their nuclear receptor partners. In this study, we investigated the effects of 9cRA on the prostaglandin E2 (PGE2) and thromboxane A2 (TXA2) production. 9cRA increased the PGE2 and TXA2 productions in the presence of lipopolysaccharide (LPS). All-trans retinoic acid, the retinoic acid receptor ligand, also increased their production. We revealed that cyclooxygenase (COX)-2 was clearly induced by 9cRA in the presence of LPS. The induction was not suppressed by indomethacin, which completely inhibited the increase in the LPS-stimulated prostanoid production by 9cRA. The expression levels of the toll-like receptor 4 and CD14, which were components of the LPS receptor complex, were increased by 9cRA in the presence and absence of LPS. PGE synthase was also clearly increased by 9cRA in the presence and absence of LPS. In this study, we noted that 9cRA increased the production of PGE2 and TXA2 by the induction of COX-2 and PGE synthase in the presence of LPS. The induction of the LPS receptor complex by 9cRA is able to upregulate the induction of COX-2 by LPS.

Transmission of Chlamydia pneumoniae infection from blood monocytes to vascular cells in a novel transendothelial migration model

Chlamydia pneumoniae uses blood monocytes (PBMC) for systemic dissemination, persists in atherosclerotic lesions, and has been implicated in the pathogenesis of atherosclerosis. During transmigration in a newly developed transendothelial migration model (TEM) C. pneumoniae-infected PBMC spread their infection to endothelial cells. Transmigrated PBMC retained their infectivity and transmitted the pathogen to smooth muscle cells in the lower chamber of the TEM. Detection of chlamydial HSP60 mRNA proved pathogen viability and virulence. We conclude that PBMC can spread chlamydial infection to vascular wall cells and we suggest the TEM as a novel tool to analyze host-pathogen interactions in vascular chlamydial infections.

Heat Shock Proteins in Vascular Disease—A Review

INTRODUCTION

There is growing evidence that heat shock proteins (HSPs), a family of stress-inducible proteins may be involved in the pathogenesis of atherosclerotic vascular diseases. Here, we systematically review the evidence behind this notion.

METHODS

A detailed literature search and extensive bibliographic review of literature relating to HSPs and atherosclerotic vascular disease.

RESULTS

Atherosclerotic vascular disease is classified into four main areas of presentation: carotid, coronary, aortic and peripheral vascular disease, for consideration in this review. In each of these vascular diseases, the evidence linking HSPs and atherosclerosis is outlined in a systematic manner. Current evidence suggests that components of the immune system may be involved in the pathogenesis of atherosclerosis, with HSPs acting as auto-antigens in the immune response. HSPs are detected in atherosclerotic lesions and antibodies to HSPs are increased in patients with vascular disease; the rise often correlating with the severity of atherosclerosis. The levels of anti-HSP antibodies have been shown to be independent predictors of risk and have prognostic value.

CONCLUSION

There is a strong link between heat shock protein expression and the principal manifestations of atherosclerotic vascular diseases. A better understanding of this involvement could lead to the development of new and improved treatment strategies.

Bile acids in physico-chemical host defence

The discovery of the physico-chemical host defence is closely connected with the endotoxin research. It is well known that the toxic effects of endotoxins under experimental conditions can be induced only when they are administered parenterally. However, in naturally occurring entero-endotoxemic diseases (e.g. septic and various shocks, etc.), the endotoxin is absorbed from the intestinal tract. The cause and mode of translocation have been unknown. The generally used experimental shock models differ from natural diseases only in the mode by which endotoxin enters the blood circulation. If the common bile duct of rats was chronically canulated (bile-deprived animals) orally administered endotoxin was absorbed from the intestinal tract into blood circulation and provoked endotoxin shock. This translocation of endotoxins and the consequent shock can be prevented by sodium deoxycholate or natural biles. The bile acids split the endotoxin macromolecule into atoxic fragments. A similar detoxifying detergent action plays a significant role in host defence against infectious agents with outer lipoprotein structure (e.g. so-called 'big' viruses). This defence mechanism of macroorganisms based on the detergent activity of bile acids (end-products of the cholesterol metabolism) is called as physico-chemical defence system. Therefore, bile deficiency and the consequent endotoxemia are important components in the pathogenesis of certain diseases (e.g. sepsis, intestinal syndrome of radiation disease, hepato-renal syndrome, parvovirus infection, herpes, psoriasis, atherosclerosis, etc.). Bile acids may be used for the prevention and/or therapy of the above mentioned clinical conditions.

Chlamydophila pneumoniae induces p44/p42 mitogen-activated protein kinase activation in human fibroblasts through Toll-like receptor 4

Chlamydophila pneumoniae, an obligately intracellular Gram-negative bacterium and a common causative agent of respiratory tract infections, has been implicated in the induction and progression of atherosclerosis and coronary artery disease. In this study, the signalling mechanism of C. pneumoniae in human fibroblasts, a prominent cell population in chronic inflammation and persistent infection, contributing to plaque formation, was investigated. C. pneumoniae elementary bodies were demonstrated to up-regulate the phosphorylation of p44/p42 mitogen-activated protein kinase (MAPK) in human fibroblasts. The effect was independent of the chlamydial lipopolysaccharide and was likely to be mediated by a heat-labile chlamydial protein. Furthermore, an anti-Toll-like receptor 4 (TLR4) antibody was shown to abolish C. pneumoniae-induced cell activation, whereas an anti-TLR2 antibody had no effect, indicating the role of TLR4 in p44/p42 MAPK activation. Ca2+/calmodulin-dependent protein kinase inhibitor KN-62 and phosphodiesterase 4 (PDE 4) inhibitor Rolipram enhanced C. pneumoniae-induced MAPK phosphorylation and attenuated C. pneumoniae infectivity in vitro. Together the results indicate that C. pneumoniae triggers rapid TLR4-mediated p44/p42 MAPK activation in human fibroblasts and chemical enhancement of MAPK phosphorylation modulates in vitro infection at the molecular level.

DETECTION OF CHLAMYDIA PNEUMONIAE IN LIVER TRANSPLANT PATIENTS WITH CHRONIC ALLOGRAFT REJECTION

BACKGROUND

Chlamydia pneumoniae is one of the possible pathogenetic factors of atherosclerotic processes. Foam cell arteriopathy is a generally accepted pathologic feature of chronic liver allograft rejection and has several similarities to the early lesions of atherosclerosis. The aim of the authors' study was to show any existing correlation between the occurrence of Chlamydia pneumoniae and the presence of foam cell arteriopathy in transplanted livers with chronic rejection.

METHODS

Ten liver samples from patients with chronic liver rejection including foam cell arteriopathy and 10 liver samples from healthy individuals were analyzed for the presence of Chlamydia pneumoniae by specific immunohistochemistry and polymerase chain reaction (PCR). Liver samples from two transplant patients with chronic liver rejection without any evidence of foam cell arteriopathy and nine patients with acute liver allograft rejection were also investigated by PCR.

RESULTS

In all 10 rejected liver samples, Chlamydia pneumoniae was detected by PCR, whereas only one of the healthy control samples and one of the samples with acute rejection were found to be positive. Immunohistochemistry showed similar results. The positive signals of Chlamydia pneumoniae were localized mainly in the hepatocytes, sinusoidal and perisinusoidal cells, and the cells of portal tracts, whereas most of the altered hepatic arteries showed no or very weak positivity.

CONCLUSIONS

The results strongly suggest an association between the occurrence of Chlamydia pneumoniae and the presence of foam cell arteriopathy in transplanted livers.

Chlamydia pneumoniae--an infectious risk factor for atherosclerosis?

Cardiovascular disease, of which atherosclerosis is an important component, is the leading cause of death in the western world. Although there are well-defined risk factors for atherosclerosis, these factors do not account for all incidences of the disease. Because atherosclerotic processes are typified by chronic inflammatory responses, which are similar to those that are elicited by chronic infection, the role of infection in promoting or accelerating atherosclerosis has received renewed attention. This review focuses on the accumulating evidence that chronic infection with Chlamydia pneumoniae, a ubiquitous human respiratory pathogen, might contribute to atherosclerotic lesion progression.

Chlamydia pneumoniae and atherosclerosis

Exposure to Chlamydia pneumoniae is extremely common, and respiratory infections occur repeatedly among most people. Strong associations exist between C. pneumoniae infection and atherosclerosis as demonstrated by: (i) sero-epidemiological studies showing that patients with cardiovascular disease have higher titres of anti-C. pneumoniae antibodies compared with control patients; (ii) detection of the organism within atherosclerotic lesions, but not in adjacent normal tissue by immunohistochemistry, polymerase chain reaction and electron microscopy and by culturing the organism from lesions; and (iii) showing that C. pneumoniae can either initiate lesion development or cause exacerbation of lesions in rabbit and mouse animal models respectively. The association of this organism with atherosclerosis has also provided sufficient impetus to conduct a variety of human secondary prevention antibiotic treatment trials. The results of these studies have been mixed and, thus far, no clear long-lasting benefit has emerged from these types of investigations. Studies of C. pneumoniae pathogenesis have shown that the organism can infect many cell types associated with both respiratory and cardiovascular sites, including lung epithelium and resident alveolar macrophages, circulating monocytes, arterial smooth muscle cells and vascular endothelium. Infected cells have been shown to exhibit characteristics associated with the development of cardiovascular disease (e.g. secretion of proinflammatory cytokines and procoagulants by infected endothelial cells and foam cell formation by infected macrophages). More detailed analysis of C. pneumoniae pathogenesis has been aided by the availability of genomic sequence information. Genomic and proteomic analyses of C. pneumoniae infections in relevant cell types will help to define the pathogenic potential of the organism in both respiratory and cardiovascular disease.

Follicular fluid antibodies to Chlamydia trachomatis and human heat shock protein-60 kDa and infertility in women

BACKGROUND

The objective of this study was to establish the relationship between presence of anti-Chlamydia trachomatis and anti-HSP60 antibodies in serum and follicular fluid of infertile women.

METHODS

Serum IgG and follicular fluid IgA to Chlamydia trachomatis and human heat shock protein 60 (HSP60) were determined in 41 women undergoing in vitro fertilization (IVF).

RESULTS

A significant association was found between presence of bacterial antibodies in serum and IgA anti-HSP60 in follicular fluid.

CONCLUSIONS

Chlamydia trachomatis infection might be triggering an autoimmune process that could negatively affect the success of IVF.

Germline antibody recognition of distinct carbohydrate epitopes

High-resolution structures reveal how a germline antibody can recognize a range of clinically relevant carbohydrate epitopes. The germline response to a carbohydrate immunogen can be critical to survivability, with selection for antibody gene segments that both confer protection against common pathogens and retain the flexibility to adapt to new disease organisms. We show here that antibody S25-2 binds several distinct inner-core epitopes of bacterial lipopolysaccharides (LPSs) by linking an inherited monosaccharide residue binding site with a subset of complementarity-determining regions (CDRs) of limited flexibility positioned to recognize the remainder of an array of different epitopes. This strategy allows germline antibodies to adapt to different epitopes while minimizing entropic penalties associated with the immobilization of labile CDRs upon binding of antigen, and provides insight into the link between the genetic origin of individual CDRs and their respective roles in antigen recognition.

Antibody response to chlamydial heat shock protein 60 is strongly associated with acute coronary syndromes

BACKGROUND

Heat shock proteins (HSPs) are a family of proteins with immunogenic and proinflammatory properties. Human and Chlamydia pneumoniae (Cp) HSP60 were found in patients with stable coronary disease.

METHODS AND RESULTS

We measured the levels of anti-Cp-HSP60 and anti-Cp immunoglobulin G (IgG) in 179 patients with unstable angina, 40 with acute myocardial infarction, and 40 with stable angina (SA), as well as 100 control subjects. Forty-one patients with acute coronary syndromes (ACS) were also studied at follow-up. We also measured plasma levels of high-sensitivity C-reactive protein (hs-CRP) and troponin T (TnT). Seropositivity to Cp-HSP60 was found in 99% of ACS patients but in only 20% of SA patients and none of the control subjects. Seropositivity to Cp was detected in 67% of ACS patients, 60% of SA patients, and 30% of the control subjects. No differences in Cp-HSP60 IgG and in Cp IgG were observed between patients with myocardial infarction and patients with unstable angina. No correlation was found between Cp-HSP60 IgG, TnT, and hs-CRP or between IgG against Cp and hs-CRP. In ACS patients at follow-up, Cp-HSP60 IgG decreased from 0.88+/-0.25 to 0.45+/-0.14 arbitrary units (P<0.0001), becoming negative in 12 patients.

CONCLUSIONS

Seropositivity for Cp-HSP60 appears to be a very sensitive and specific marker of ACS, unrelated to Cp IgG antibody titers or hs-CRP and TnT levels. Its causal involvement in instability and its diagnostic role in ACS deserve further study.

Chlamydia pneumoniae induces tissue factor expression in mouse macrophages via activation of Egr-1 and the MEK-ERK1/2 pathway

Recent studies have suggested that infection with Chlamydia pneumoniae (C pneumoniae) may contribute to the instability of atherosclerotic plaques and thrombosis and is associated with acute coronary events. Tissue factor (TF), a potent prothrombotic molecule, is expressed by macrophages and other cell types within atherosclerotic lesions and plays an essential role in thrombus formation after plaque rupture. Therefore the effects of C pneumoniae on induction of TF expression in macrophages were investigated. Infection of RAW mouse macrophages with C pneumoniae induced a time-dependent increase in procoagulant activity, expression of TF protein, and TF mRNA. C pneumoniae infection stimulated increased binding of nuclear proteins to the consensus DNA sequence for Egr-1, a key response element within the TF promoter, and increased the expression of Egr-1 protein. Transient transfections of RAW cells with mutated TF promoter constructs showed that the Egr-1 binding region is an important transcriptional regulator of C pneumoniae-induced TF expression. Furthermore, C pneumoniae-stimulated phosphorylation of ERK1/2 and Elk-1 and pharmacological inhibition of mitogen-activated protein kinase activity reduced the expression of TF and Egr-1. Antibody and polymyxin B blocking of the Toll-like receptor 4 (TLR4) partially reduced the C pneumoniae-induced expression of TF and Egr-1. In conclusion, the C pneumoniae-induced increase in TF expression in macrophages is mediated in part by Egr-1, signaling through TLR4, and activation of the MEK-ERK1/2 pathway.

Chlamydia pneumoniae and coronary artery disease: the antibiotic trials

Parallel with the mounting evidence that atherosclerosis has a major inflammatory component, provoking agents that may initiate and drive this process have been sought. Infectious agents such as Chlamydia pneumoniae have been alleged to be activators of inflammation that may contribute to atherosclerosis and thus coronary artery disease (CAD) and its associated complications. A logical pneumoniae extension of this theory whether treating C pneumoniae infection with antibiotics and/or modulating inflammatory processes can affect CAD and its sequelae. This article discusses the potential role of C pneumoniae in atherosclerosis, its detection, and the rationale for antibiotics. Additionally, it summarizes the current randomized clinical trials of antichlamydial antibiotics in patients with CAD and draws conclusions based on the results.

The cellular paradigm of chlamydial pathogenesis

Diseases caused by Chlamydia are based on intense and chronic inflammation elicited and maintained by reinfection or persistent infection. The traditional view in the field is that disease is mediated by antigen-dependent delayed-type hypersensitivity or autoimmunity. This immunological paradigm has served as the basis for years of chlamydial research but the mechanism or the antigen that causes pathology has yet to be unequivocally revealed. Recent research on responses elicited in Chlamydia-infected cells defines a new direction for our understanding of this microorganism-host interaction and provides the basis for a reassessment of disease mechanisms. Chlamydia-infected non-immune mammalian cells produce proinflammatory chemokines, cytokines, growth factors and other cellular modulators. This cellular response to infection supports an alternative hypothesis for chlamydial pathogenesis: the inflammatory processes of chlamydial pathogenesis are elicited by infected host cells and are necessary and sufficient to account for chronic and intense inflammation and the promotion of cellular proliferation, tissue remodeling and scarring, the ultimate cause of disease sequelae.

Infection of myocytes with chlamydiae

Chlamydial infection has been associated with myocarditis in animals and humans. However, the mechanism resulting in myocarditis following infection is not known. Here, evidence is presented that both Chlamydia trachomatis and Chlamydia pneumoniae can infect and replicate in myocytes isolated from neonate rats. The infected myocytes contained chlamydial inclusions, indicative of chlamydial growth, and infectious particles were recovered from the infected myocytes. It was also found that chlamydial infection at a late stage induced significant damage to the infected myocytes, as evidenced by an increased lactate dehydrogenase release, reactive oxygen species production and a reduced ATP level. However, no nuclear apoptosis was detected in the infected myocytes. Collectively, these observations have demonstrated that Chlamydia spp. are able to both infect and damage myocytes, suggesting a potential role of chlamydial infection in myocarditis.

KN-62 enhances Chlamydia pneumoniae-induced p44/p42 mitogen-activated protein kinase activation in murine fibroblasts and attenuates in vitro infection

Chlamydia pneumoniae elementary bodies were demonstrated to increase the proliferation of murine fibroblast cell line L-929 and rapidly activate p44/p42 mitogen-activated protein kinase (MAPK) in a protein kinase C (PKC) and protein kinase A (PKA)-independent way. Ca(2+)/calmodulin-dependent protein kinase (CaM kinase) inhibitor KN-62 significantly enhanced C. pneumoniae-induced MAPK phosphorylation, suggesting negative control of CaM kinase pathway on the MAPK cascade. In in vitro infection assay, the upstream MAPK kinase 1/2 inhibitor U0126 increased 2.5-fold C. pneumoniae infectivity in L-929 cells, while KN-62 reduced the infection by 36%. Our findings provide insight into the molecular mechanisms of bacterium-host cell interactions and demonstrate the protective role of MAPK in murine fibroblasts, suggesting novel therapeutic approaches to the treatment and prevention of chlamydial infections.