Chlamydia pneumoniae and atherosclerosis: critical assessment of diagnostic methods and relevance to treatment studies

Currently used nucleic acid amplification tests for the detection of viruses and atypicals in acute respiratory infections

For the detection of respiratory viruses conventional culture techniques are still considered as the gold standard. However, results are mostly available too late to have an impact on patient management. The latest developments include appropriate DNA- and RNA-based amplification techniques (both NASBA and PCR) for the detection of an extended number of agents responsible for LRTI. Real time amplification, the latest technical progress, produces, within a considerable shorter time, results with a lower risk of false positives. As results can be obtained within the same day, patient management with appropriate therapy or reduction of unnecessary antibiotic therapy in LRTI will be possible. A number of technical aspects of these amplification assays, and their advantages are discussed.

The availability and use of these new diagnostic tools in virology has contributed to a better understanding of the role of respiratory viruses in LRTI. The increasing importance of the viral agents, Mycoplasma pneumoniae and Chlamydophila pneumoniae in ARI is illustrated. A great proportion of ARI are caused by viruses, but their relative importance depends on the spectrum of agents covered by the diagnostic techniques and on the populations studied, the geographical location and the season. The discovery of new viruses is ongoing; examples are the hMPV and the increasing number of coronaviruses. Indications for the use of these rapid techniques in different clinical situations are discussed. Depending on the possibilities, the laboratory could optimize its diagnostic strategy by applying a combination of immunofluorescence for the detection of RSV an IFL, and a combination of real-time amplification tests for other respiratory viruses and the atypical agents. When implementing a strategy, a compromise between sensitivity, clinical utility, turn around time and cost will have to be found.

Lack of association between Chlamydophila pneumoniae seropositivity and abdominal aortic aneurysm

Chronic Chlamydophila pneumoniae infection has been suggested as a possible contributing factor for the development and expansion of abdominal aortic aneurysm (AAA). The relevance of C pneumoniae involved in the processes underlying aneurysmal rupture is unknown. The aim of this study was to examine the relationship between C pneumoniae seropositivity and AAA rupture. In a case-control study, 119 patients with AAA and 36 matched controls were prospectively investigated with C pneumoniae serology. Patients with ruptured AAA have similar levels of IgG antibodies against C pneumoniae as patients with an electively operated AAA, a small AAA, and controls. In conclusion, this study fails to demonstrate a connection between C pneumoniae seropositivity and AAA rupture.

Measurement of Chlamydia pneumoniae bacterial load in peripheral blood mononuclear cells may be helpful to assess the state of chlamydial infection in patients with carotid atherosclerotic disease

BACKGROUND

Chlamydia pneumoniae has been repeatedly associated with atherosclerotic cardiovascular diseases. We investigated the pattern of distribution of C. pneumoniae among patients with carotid atherosclerotic disease evaluating chlamydial load in carotid plaque, peripheral blood mononuclear cells (PBMC) and lymph node from same patient.

METHODS AND RESULTS

Thirty carotid plaques, 30 PBMC and 30 lymph nodes were examined by real-time PCR assay. C. pneumoniae DNA was detected, in carotid plaques, PBMC and lymph nodes in 11 patients; in carotid plaques and PBMC in five patients; in PBMC and lymph nodes in four patients; in lymph nodes in two patients; and in PBMC only in one patient. C. pneumoniae DNA in PBMC significantly coincided with the presence of the respective DNA in carotid plaque (p=0.0001) and lymph node (p=0.02). A higher chlamydial load was detected in PBMC than in lymph nodes and carotid plaques. More than 90% of patients with carotid plaques, PBMC and lymph nodes positive to C. pneumoniae were symptomatic, smokers, hypertensives, dyslipidemics and showed carotid plaques with rupture on the surface, hemorrhage and thrombosis.

CONCLUSION

The measurement of chlamydial load in PBMC may be helpful in the future to assess the state of C. pneumoniae infection and the risk of developing sequelae.

Chlamydiae and Atherosclerosis: Can Psittacine Cases Support the Link?

Atherosclerosis is a common disease in pet birds, particularly in psittacines. Little is known about the role of risk factors predisposing birds to this disease. In our study, we tried to detect chlamydiae in formalin-fixed and paraffin-embedded atherosclerotic tissue from 103 pet birds to clarify their role in atherosclerosis. Methods used were polymerase chain reaction (PCR), sequencing, and immunohistochemistry. Histopathologic examination served to classify the extent of atherosclerotic lesions. In the PCR, 4 (3.9%) of 103 cases, all of them with advanced stages of atherosclerosis, were positive. Subsequent sequence analysis revealed high identities (94%-100%) with Chlamydophila psittaci in three cases. Interestingly, two of these birds came from C. psittaci-infected populations. Because of the low incidence (3.9%), the occurrence only in advanced stages, and the association with C psittaci-infected avian populations, a causal relationship between chlamydiae and atherosclerosis in pet birds is rather improbable.

Persistent Chlamydia pneumoniae infection of cardiomyocytes is correlated with fatal myocardial infarction

Acute myocardial infarction (AMI) associated with unfavorable prognosis is likely to be the consequence of a diffuse active chronic inflammatory process that destabilizes the whole coronary tree and myocardium, suggesting a possible common causal agent underlying both conditions. The main objective of this study was to investigate whether Chlamydia pneumoniae (CP) infection occurred beyond the coronary plaques, namely in the myocardium of individuals who died of AMI. The presence of CP cell wall antigen (OMP-2) and CP-HSP60 was investigated in the myocardium and coronary plaques of 10 AMI and 10 age-matched control patients by immunohistochemistry, electron microscopy, and molecular biology. OMP-2 antigens were found in the unaffected myocardium of 9 of 10 AMI patients. Conversely, only 1 of 10 control patients exhibited a positive staining for CP. Moreover, OMP-2 and CP-HSP60 were detected in the whole coronary tree. CP presence was strongly associated with a T-cell inflammatory infiltrate. Our results suggest that CP may underlie both coronary and myocardial vulnerabilities in patients who died of AMI and corroborate the notion that CP may act by reducing cardiac reserves, thus worsening the ischemic burden of myocardium.

Chlamydia pneumoniae antibody levels before coronary events in the Helsinki Heart Study as measured by different methods

The lack of specific tests for the diagnosis of chronic Chlamydia pneumoniae infection has led to the use of enzyme immunoassay (EIA) instead of the gold standard, that is, microimmunofluorescence (MIF), in the measurement of C. pneumoniae antibodies. We assessed the predictive values of C. pneumoniae antibody levels and seroconversions measured by MIF and EIA for coronary events in the prospective Helsinki Heart Study. Sera from 239 cases with coronary events and 239 controls were available at the baseline and data from 210 cases and 211 controls before and after the event. The agreement between MIF and EIA antibody levels was best in high antibody titers. In conditional logistic regression analysis, only high IgA MIF titers (>/=40) at the baseline predicted future coronary events, and the participants with MIF seroconversion between consecutive sera had a higher (nonsignificant) risk for coronary events than the controls. The difference in the kinetics of EIA and MIF antibodies demonstrated that MIF should remain the gold standard.

Perfluorocarbons decrease Chlamydophila pneumoniae-mediated inflammatory responses of rat type II pneumocytes in vitro

Chlamydophila pneumoniae alter the expression of Toll-like receptor (TLR) 4 in alveolar type II (ATII)-cells. Subsequently nuclear factor kappaB (NF-kappaB) is activated and tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein 2 (MIP-2) are produced. Perfluorocarbons (PFC) are beneficial in animals with bacterial pneumonia and reduce production of TNF-alpha. Using isolated ATII-cells, it was studied whether PFC prevent C. pneumoniae-induced TNF-alpha and MIP-2 release and what the underlying pathway is. PF5080 preincubation prevented C. pneumoniae-induced secretion of TNF-alpha (43 +/- 10 versus 661 +/- 41 pg/mL) and MIP-2 (573 +/- 41 versus 4786 +/- 502 pg/mL). The C. pneumoniae-induced 2.2-fold increase of TNF-alpha Receptor 1 expression was reduced by PF5080. C. pneumoniae reduced cytoplasmatic IkappaBalpha (3.7 +/- 0.3 versus 14 +/- 1) and increased NF-kappaB p65 (31 +/- 7.5 versus 3.6 +/- 1.1) compared with control. PF5080 prevented NF-kappaB activation. TLR4 expression was 1.5-fold higher after C. pneumoniae incubation, but remained at control levels after PF5080 pretreatment. After 24 h of C. pneumoniae incubation, in 88 +/- 6% of cells bacteria were found in the perinuclear region and in 50% of these cells bacteria adhered to cellular surface. After PF5080 preincubation, C. pneumoniae were in 32 +/- 4% attached to and in 5 +/- 1% internalized in ATII-cells. Since PF5080 was found in ATII-cell membranes, PF5080 effect could be explained by an alteration of the cellular membrane, preventing activation of the inflammatory cascade.

Rapid molecular dissection of viral and bacterial immunomes

The development of preventive or therapeutic recombinant vaccines and the generation of serodiagnostic assays for infectious diseases depend essentially on the availability of molecularly defined antigens. A major bottleneck for the identification of suitable target antigens for many pathogens is the isolation of sufficient amounts of material for subsequent genomic or proteomic screening. Applying a highly efficient expression cloning strategy to the human pathogens vaccinia virus (VV) and Chlamydia pneumoniae (CP), we demonstrate that sub-nanogram amounts of isolated nucleic acids can be utilized to determine comprehensive sets of immunodominant antigens. Remarkably, the approach not only confirmed the immunogenicity of previously reported antigens but also disclosed novel vaccine candidates conserved in orthopoxviruses, including antigenic envelope proteins and immunodominant CTL epitopes. Moreover, as illustrated for CP infection, we show that a panel of novel antigens can be readily selected from the initially discovered pool to build up pathogen-specific seroassays. The established approach is rapid, making it an attractive procedure for the comprehensive dissection of immunomes of known human pathogens and newly emerging infectious agents.

Macrophage antioxidant enzymes regulate Chlamydia pneumoniae chronicity: evidence of the effect of redox balance on host-pathogen relationship

Latency, chronicity and recurrent nature are the features of Chlamydia pneumoniae biology which play a central role in the course and outcome of C. pneumoniae-host interaction. Since redox status is directly an indicator of inflammatory response via molecular signaling mechanisms, we decided to study the regulatory role of macrophage cellular redox balance on the molecular indices of C. pneumoniae chronicity. We examined GSH-GSSG status, the activities of antioxidant enzymes (SOD, GPx and gamma-GCS), along with their protein and gene expression, the MOMP and cHSP-60 protein and gene expression, and the consequence of redox balance on the establishment of productive infection in macrophages. Results showed that C. pneumoniae caused changes in GSH-GSSG levels, antioxidant enzymes activity, mRNA gene and protein expression in macrophages. The relevance of this to the state and status of C. pneumoniae in macrophages was assessed by inhibitor induced attenuation of antioxidant enzymes and there was evidence that, while SOD attenuation did not significantly affect MOMP and cHSP-60 gene and protein expression, gamma-GCS attenuation increased cHSP-60 gene and protein expression. The increase in molecular evidence of chronic forms of C. pneumoniae (cHSP-60) was consistent with decrease in normal forms of C. pneumoniae. These findings reflect the importance of redox balance modulation on the outcome of C. pneumoniae infection in macrophages, a significant process in the pathogenesis of chlamydial diseases.

Pathogenic potential of novel Chlamydiae and diagnostic approaches to infections due to these obligate intracellular bacteria

Novel chlamydiae are newly recognized members of the phylum Chlamydiales that are only distantly related to the classic Chlamydiaceae, i.e., Chlamydia and Chlamydophila species. They also exhibit an obligate biphasic intracellular life cycle within eukaryote host cells. Some of these new chlamydiae are currently considered potential emerging human and/or animal pathogens. Parachlamydia acanthamoebae and Simkania negevensis are both emerging respiratory human pathogens, Waddlia chondrophila could be a novel abortigenic bovine agent, and Piscichlamydia salmonis has recently been identified as an agent of the gill epitheliocystis in the Atlantic salmon. Fritschea spp. and Rhabdochlamydia spp. seem to be confined to arthropods, but some evidence for human exposure exists. In this review, we first summarize the data supporting a pathogenic potential of the novel chlamydiae for humans and other vertebrates and the interactions that most of these chlamydiae have with free-living amoebae. We then review the diagnostic approaches to infections potentially due to the novel chlamydiae, especially focusing on the currently available PCR-based protocols, mammalian cell culture, the amoebal coculture system, and serology.

Chlamydophila pneumoniae and human cytomegalovirus in atherosclerotic carotid plaques--combined presence and possible interactions

The aim of our study was to investigate the combination of Chlamydophila pneumoniae and human cytomegalovirus (HCMV) as a pathogenic factor in atherosclerosis. Accordingly, we tested by means of PCR and immunohistochemistry the presence of these pathogens in the same atherosclerotic carotid specimen. The histology of the samples and the patients' antibodies against these pathogens were evaluated. Further, we examined the impact of C. pneumoniae and HCMV infection on the gene expression of the human monocytic cell line U937. Six of the 22 samples contained only C. pneumoniae, 4 contained only HCMV, 7 contained both C. pneumoniae DNA and/or antigens of both pathogens, and 5 samples were negative. No correlation was found between the presence of these microbes and either the cellular structure of the plaques, or the serostatus of the patients. The infection of U937 cells with HCMV and especially C. pneumoniae induced inflammation and atherosclerosis-related genes. Furthermore, the doubly-infected cells produced higher levels of the mRNA of pro-platelet basic protein and fatty acid binding protein 4. In conclusion, C. pneumoniae is often present in combination with HCMV in atherosclerotic carotid lesions. The in vitro coinfection model reveals that the doubly-infected monocytes are potent expressors of proatherosclerotic genes, suggesting that this coinfected population may accelerate the process of atherosclerosis.

Seropositivity to Chlamydia pneumoniae is associated with risk of first ischemic stroke

BACKGROUND AND PURPOSE

Serologic evidence of infection with Chlamydia pneumoniae has been associated with cardiovascular disease, but its relationship with stroke risk remains uncertain. The objective of this study is to determine whether serological evidence of C pneumoniae infection is associated with risk of ischemic stroke.

METHODS

A population-based case-control study was performed in an urban, multiethnic population. Cases (n=246) had first ischemic stroke, and controls (n=474) matched for age, sex, and race-ethnicity were derived through random-digit dialing. Titers of C pneumoniae-specific IgG and IgA antibodies were measured using microimmunofluorescence, and positive titers were prospectively defined. Conditional logistic regression was used to calculate odds ratios (ORs) and 95% CIs adjusting for medical, behavioral, and socioeconomic factors.

RESULTS

Mean age among cases was 72.3+/-9.7 years; 50.8% were women. Elevated C pneumoniae IgA titers were associated with increased risk of ischemic stroke after adjusting for hypertension, diabetes mellitus, current cigarette use, atrial fibrillation, and levels of high-density lipoprotein and low-density lipoprotein (adjusted OR, 1.5; 95% CI, 1.0 to 2.2). Elevated IgG titers were not associated with stroke risk (adjusted OR, 1.2; 95% CI, 0.8 to 1.8). There was a trend toward an association of elevated IgA titers with atherosclerotic and lacunar stroke but less so cardioembolic or cryptogenic subtypes.

CONCLUSIONS

Serologic evidence of C pneumoniae infection is associated with ischemic stroke risk. IgA titers may be a better marker of risk than IgG. This association is independent of other stroke risk factors and is present for atherosclerotic, lacunar, and cardioembolic subtypes. Further studies of the effect of C pneumoniae on stroke risk are warranted.

Presence of Chlamydia pneumoniae in patients with and without atherosclerosis

Data published over the past decade show that Chlamydia pneumoniae is likely associated with the development of atherosclerosis. The aim of this study was to ascertain whether C. pneumoniae infections occur more frequently in patients with atherosclerosis than in healthy subjects. A total of 517 persons were studied. Serum samples, leukocytes, and tissue samples were assayed for the presence of C. pneumoniae-specific IgG and IgA antibodies and C. pneumoniae DNA. C. pneumoniae DNA was found in renal, iliac, and brachial vessels, but it was not detected in radial arteries. C. pneumoniae DNA was found most often in directional coronary atherectomy tissue specimens (11/41, 26.8%), but it was also found in the leukocytes of 14.9% (28/188) of patients with atherosclerosis and 24.6% (28/114) of patients without atheroma changes in vessels. Specific IgG and IgA antibodies were present in 63.8 and 49.9% of atheroma patients, respectively. The prevalence of C. pneumoniae antibodies differs significantly in patients with and without atherosclerosis (for IgG, p=0.002, and for IgA, p=0.006). The identification of persons with chlamydial infection of atherosclerotic arteries necessitates the examination of vascular tissues obtained during revascularization procedures. Serological investigation alone cannot identify individuals with vascular chlamydial infections. Detection of C. pneumoniae DNA in peripheral blood mononuclear cells does not seem to be the exclusive marker of persistent vascular infection. A more easily accessible parameter that allows prediction of chlamydial vascular infection is required.

Prevalence and persistence of Chlamydia pneumoniae antibodies in healthy laboratory personnel in Finland

The rates of Chlamydia pneumoniae seroconversions suggesting acute primary infections or reinfections and the prevalences of antibodies were followed up among healthy laboratory workers. Annual serum samples were collected from 47 persons in Helsinki from 1958 to 1990 and from 40 persons in Oulu from 1994 to 1999. C. pneumoniae species-specific immunoglobulin G (IgG), IgA, and IgM antibodies were measured by microimmunofluorescence (MIF) in 407 sera from Helsinki. The 185 sera collected in Oulu were tested both by MIF and by commercial enzyme immunoassay (EIA). During the follow-up periods of 31 years in Helsinki and 6 years in Oulu, seroconversions were demonstrated by MIF in 45% and 15% of the study groups, respectively. In Helsinki 9% of the persons seroconverted twice during the follow-up period. By MIF, the total incidence rate per 100 person-years at risk was 6.9 in Helsinki and 4.9 in Oulu, and annual incidence rates varied from 0 to 15.4. By EIA, annual incidence rates in Oulu varied from 0 to 10.8. The seroconversions by MIF were usually not confirmed by EIA and vice versa. Prevalence and persistence rates, respectively, of IgA antibodies were higher in EIA (62% and 26%) than in MIF (26% and 17%), whereas the figures for IgG were quite similar. The prevalence of IgG and IgA antibodies was higher in older persons than in younger ones. The presence of antibodies did not offer protection from reinfection.

Therapeutic approaches toChlamydiainfections

Chlamydia trachomatis ocular and urogenital infections represent major public health problems, whereas Chlamydophila pneumoniae is a common aetiological agent of community-acquired pneumonia. The obligate intracellular lifestyle of these established pathogens poses challenges to both their diagnosis and treatment. Tetracyclines, macrolides and quinolones remain the antimicrobials of choice for the treatment of infections due to Chlamydiaceae.

Chlamydia pneumoniae in an ex vivo human artery culture model

The role of the obligate intracellular pathogen Chlamydia pneumoniae in the development of atherosclerosis could not be completely clarified. Reasons are the highly discrepant results obtained in the hitherto existing studies and the lack of an experimental system allowing the direct examination of chlamydial effects in the human vasculature. We established a human ex vivo organ culture model for the characterization of vascular chlamydial infection. Ninety sections of renal arteries, obtained from nephrectomies, were inoculated with Chlamydia pneumoniae. Using a monoclonal FITC-conjugated antibody, chlamydial LPS was broadly detected in inoculated arteries during the entire observation period of 35 days. However, recultivation of viable organisms from the artery vessel wall was impossible, indicating that productive infection in human arteries did not occur even under optimized conditions. This was substantiated by low recovery rates of Chlamydia pneumoniae, low amounts of detectable chlamydial 16S rRNA and ultramorphological presence of polymorph multilamellar bodies in experimentally infected smooth muscle cells originating from aortas, coronary and renal arteries. We could demonstrate that the complex environment of a human artery did not support the growth of Chlamydia pneumoniae although the presence of chlamydial LPS in the artery vessel wall following experimental infection was a common event. The presence of chlamydial LPS in the absence of viable organisms within the artery vessel wall may explain the failure of antibiotic treatment strategies for atherosclerosis.

Chlamydia pneumoniae and atherosclerosis: from Koch postulates to clinical trials

Atherosclerosis is increasingly viewed as an inflammatory process. A number of infectious agents have been implicated in the pathogenesis of coronary artery disease. Chlamydia pneumoniae has been the most popular and well-studied of these pathogens. It is difficult to prove a causal relationship which requires the fulfillment of Koch's postulates, first developed in the late 1800s, to establish an infectious agent as the cause of a disease process. This paper reviews the evidence for and against Chlamydia pneumoniae infection as a contributing factor to atherosclerosis disease. It examines seroepidemiologic and histopathologic studies as well as animal models using Koch's postulates and then provides an analysis of current clinical trial data.

Azithromycin reduces Chlamydia pneumoniae-induced attenuation of eNOS and cGMP production by endothelial cells

BACKGROUND

Intracellular infections with cytomegalovirus (CMV) or Chlamydia pneumoniae (Cp) may play a role in the aetiology of atherosclerosis. Nitric oxide (NO) is a key regulator of endothelial function. Under pathological conditions uncoupling of endothelial nitric oxide synthase (eNOS) leads to vessel damage as a result of production of oxygen radicals instead of NO. We hypothesized that infection-induced atherosclerosis is initiated by changes in NO metabolism and may be reversed by azithromycin treatment.

METHODS

Confluent human umbilical vein endothelial cells (HUVECs) were infected with Cp or CMV. After 48 h of infection, production of eNOS, cyclic guanosine monophosphate (cGMP) and reactive oxygen species (ROS) was measured. Detection of cGMP was used as a reporter assay for the bioavailability of NO. Subsequently, Cp- and CMV-infected HUVECs were coincubated with 0.016 mg L(-1) and 1 mg L(-1) azithromycin.

RESULTS

Infection with Cp (MOI 1 and MOI 0.1) and CMV (MOI 1) caused a dose- and time-dependent reduction of eNOS production in the HUVECs: Cp MOI 1: 1141 +/- 74 pg mL(-1) (P < 0.01); Cp MOI 0.1: 3189 +/- 30 pg mL(-1) (P < 0.01); CMV: 3213 +/- 11 pg mL(-1) (P < 0.01) vs. 3868 +/- 83 pg mL(-1) for uninfected HUVECs. Chlamydia pneumoniae- but not CMV-infection also reduced cGMP-production (Cp: 0.195 +/- 0.030 pmol mL(-1) (P < 0.01); CMV: 0.371 +/- 27 pmol mL(-1) (P > 0.05) vs. 0.378 +/- 0.019 pmol mL(-1) for uninfected HUVECs). CMV-infection did not affect ROS production either, but Cp-infection reduced ROS-production by 21% (P > 0.05; Cp MOI 0.1) to 68% (P < 0.01; Cp MOI 1). Azithromycin treatment restored Cp-induced eNOS, cGMP and ROS production in a dose-dependent manner.

CONCLUSIONS

Infection with Cp in endothelial cells in vitro attenuates eNOS, cGMP and ROS production in HUVECs and azithromycin reverses Cp-induced effects on eNOS, cGMP and ROS-production. The results from our in vitro research support the role of antibiotic therapy for infection-induced atherosclerosis by indicating that azithromycin does actually improve endothelial function.

Could Chlamydia Pneumoniae Be Considered an Infectious Risk Factor for Inflammatory Diseases Such as Atherosclerosis ?

Chlamydia pneumoniae, a Gram-negative intracellular obligate bacteria, is recognised as a common cause of upper respiratory tract infections, and accounts for ∼10% of community-acquired pneumonia. In recent years, chronic and persistent infection with C. pneumoniae has been implicated in the pathogenesis of atherosclerosis. Atherosclerosis is regarded as a chronic inflammatory disease that results from complex interactions between a variety of cell types such as endothelial cells, vascular smooth muscle cells, monocytes/macrophages and inflammatory mediators. Involvement of C. pneumoniae in the pathogenesis of atherosclerosis has been supported by findings from seroepidemiologic studies, direct detection of chlamydial DNA, experimental animal and in vitro studies, and antibiotic intervention trials. The spectrum of cell biological, animal, and human clinical data suggests that C. pneumoniae may be considered an infectious risk factor for atherosclerosis but further studies are needed to clarify the etiopathogenetic role of C. pneumoniae in atherosclerotic vessel walls.

A population based seroepidemiological survey of Chlamydia pneumoniae infections in schoolchildren

AIM

A serosurvey was carried out in schoolchildren from a northeastern area of Italy to define the burden of Chlamydia pneumoniae infection.

METHODS

A sample of 649 schoolchildren underwent a simplified version of the International Study of Asthma and Allergies in Childhood questionnaire and IgG and IgA antibodies were investigated using an enzyme immunoassay, followed by a microimmunofluorescence assay in reactive sera.

RESULTS

Of the children examined, 29% and 19.7% had IgG and IgA antibodies, respectively. The IgG prevalence increased with age. No other sociodemographical variable was related to C pneumoniae infection. An association was established between IgA prevalence and previous otitis media.

CONCLUSIONS

A mesoendemic (intermediate between high and low endemic level) pattern of C pneumoniae infection is present in schoolchildren from this area and the prevalence rate is related to age. Moreover, this is the first epidemiological evidence of the role of C pneumoniae in otitis.

Chlamydia pneumoniae and lung cancer: epidemiologic evidence

Chlamydia pneumoniae is a common cause of acute respiratory infection and has been hypothesized to cause several chronic diseases, including lung cancer. The purpose of this article is to identify, describe, and critically examine the published studies on the association between C. pneumoniae infection and risk of lung cancer. In the six studies identified, previous C. pneumoniae infection was defined on the basis of serologic criteria, which varied between studies. All studies reported elevated relative risk estimates for the association of serologic evidence of infection and risk of lung cancer. The three studies in which past infection was defined based on testing of prediagnostic blood specimens tended to have weaker results (odds ratio range, 1.2-2.1) than those based on postdiagnostic blood specimens (odds ratio range, 1.4-9.9). Selection bias, measurement error, and inadequate control for confounding are concerns in some of these studies. Nevertheless, results were relatively consistent, supporting a causal association. Inflammation caused by chronic infection with C. pneumoniae may be involved in the carcinogenic process but this relationship will be difficult to further define through serologic data. To better understand the nature of this association, both experimental study designs, such as those based on animal models or randomized controlled antibiotic treatment trials in humans, and observational study designs (e.g., studies that involve detection of C. pneumoniae in pulmonary specimens obtained before cancer onset) could be explored and may shed additional light on this important association.

Chlamydia pneumoniae seropositivity and risk of ischemic stroke: a nested case-control study

Chlamydia pneumoniae has been linked with increased risk of cardiovascular disease, but data on stroke are sparse. We examined whether seropositivity to Chlamydia pneumoniae was associated with the risk of ischemic stroke in a nested case-control study. Data on Chlamydia pneumoniae serology, lifestyle factors, and medical history were obtained at baseline. Verified cases (n = 254) were compared with gender- and age-matched controls (n = 254). Positive IgA (> or = 1:16) or IgG (> or = 1:64) titers were associated with an increased risk of acute ischemic stroke, i.e. adjusted odds ratios (ORs) were 1.54 (95% confidence interval, CI: 0.96-2.47) and 1.28 (95% CI: 0.83-1.95). The adjusted OR was 1.77 (95% CI: 1.04-3.00) when both titers were elevated. The highest point estimates were seen for ischemic stroke due to large-artery atherosclerosis, adjusted OR: 6.32 (95% CI: 0.76-52.61) (IgG (> or = 1:64)). No clear associations were found for other types of ischemic stroke. The strength of the association varied depending on gender and the chosen cut-off values for the antibody titers. These results partly support the hypothesis that serologic evidence of Chlamydia pneumoniae infection may be associated with an increased risk of ischemic stroke. However, the risk may differ according to gender, subtype of ischemic stroke, and cut-off value of antibody titers.

Effect of clarithromycin treatment on Chlamydia pneumoniae in vascular tissue of patients with coronary artery disease: a randomized, double-blind, placebo-controlled trial

Several small clinical trials have indicated that antibiotic treatment of Chlamydia pneumoniae infection is associated with a better outcome in patients with coronary artery disease (CAD). It has not been demonstrated whether antibiotic treatment eradicates C. pneumoniae from vascular tissue. The aim of the present study was to assess the effect of clarithromycin on the presence of C. pneumoniae in the vascular tissue of patients with CAD. Patients who had CAD and who were waiting for coronary artery bypass graft surgery were enrolled in a randomized, double-blind, placebo-controlled trial. Patients were treated with clarithromycin at 500 mg or placebo once daily from the day of inclusion in the study until surgery. Several vascular tissue specimens were obtained during surgery. The presence of C. pneumoniae in vascular tissue specimens was examined by immunohistochemical staining (IHC) and two PCR assays. Chlamydia immunoglobulin G (IgG) titers were determined by an enzyme-linked immunosorbent assay at the time of inclusion in the study and 8 weeks after surgery. A total of 76 patients were included, and 180 vascular tissue specimens were obtained (80 specimens from the group treated with clarithromycin and 100 specimens from the group treated with placebo). Thirty-five patients received clarithromycin (mean duration, 27 days; standard deviation [SD], 12.2 days), and 41 patients received placebo (mean duration, 27 days; SD, 13.9 days). IHC detected the C. pneumoniae major outer membrane protein antigen in 73.8% of the specimens from the group treated with clarithromycin and 77.0% of the specimens from the group treated with placebo (P was not significant). Chlamydia lipopolysaccharide antigen was found in only one specimen from the group that received placebo. C. pneumoniae DNA was not detected in any specimen. Baseline Chlamydia-specific IgG titers were equally distributed in both groups and were not significantly different after treatment. There was no indication of an active C. pneumoniae infection in vascular tissue. Chlamydia-specific IgG titers remained unchanged throughout the study in both the antibiotic- and the placebo-treated patients.

Molecular genetic methods in the diagnosis of lower respiratory tract infections

Molecular diagnostic techniques, such as PCR, have become useful tools for the rapid etiological diagnosis of lower respiratory tract infections. Nucleic acid amplification tests (NAATs) have been evaluated for detecting most respiratory pathogens, and commercial assays are available for some pathogens. However, standardized protocols are needed before these assays are introduced into routine diagnostic use. For pneumonia, NAATs offer advantages over conventional tests for the detection of Mycoplasma pneumoniae, Legionella spp. and Chlamydia pneumoniae. For pneumococcal pneumonia in adults, PCR adds little to existing diagnostic tests, and is unable to distinguish pneumococcal colonization from infection when testing respiratory samples. Although less sensitive than culture-based methods, several commercial molecular diagnostic assays have been developed for tuberculosis and are useful rapid tests for selected patients. PCR can now be considered the rapid diagnostic test of choice for pertussis and some respiratory virus infections. Further work is required to better characterize the role of molecular diagnostic tests for diagnosing lower respiratory tract infections, and to develop standard assays that can be readily adopted by routine diagnostic laboratories.

Chlamydia pneumoniae infection promotes a proliferative phenotype in the vasculature through Egr-1 activation in vitro and in vivo

Atherosclerosis is characterized by inflammation and proliferation of vascular cells. The intracellular bacterium Chlamydia (Chlamydophila) pneumoniae uses blood monocytes [peripheral blood mononuclear cells (PBMCs)] for dissemination, has been found to persist in atherosclerotic lesions, and has been implicated in atherogenesis by small GTPase activation and T lymphocyte recruitment. Infection of human coronary artery smooth muscle cells with C. pneumoniae significantly induced mRNA and protein for the angiogenic transcription factor Egr-1, resulting in enhanced coronary artery smooth muscle cell proliferation, which was reduced by transfection with small interfering RNA duplexes targeted at Egr-1 mRNA. These effects required viable chlamydiae and depended on p44/42 mitogen-activated protein kinase activity but not on the p38 mitogen-activated protein kinase pathway. Postinfectious Egr-1 mRNA up-regulation in arterial vessels was confirmed ex vivo in a rat aortic ring model of focal vascular chlamydial infection. An in vivo model based on the injection of C. pneumoniae-infected PBMCs into mice confirmed Egr-1 mRNA up-regulation within 24 h of endovascular infection. Arterial injury from repeated direct chlamydial infections and cell-to-cell contact with C. pneumoniae-infected PBMCs might represent a chronic focus of proliferative activity linked to the media proliferation seen in advanced atherosclerosis. Overall, chlamydial infection induces a proliferative phenotype in vascular cells via transcription factor Egr-1 activation in vitro, ex vivo, and in vivo.

Is the perceived association between Chlamydia pneumoniae and vascular diseases biased by methodology?

Inter- and intralaboratory inconsistencies in detection rates of Chlamydia pneumoniae in vascular specimens have been demonstrated. In this study, 66 vascular tissue specimens from 66 patients with vascular disease were tested by three PCR assays: a 16S PCR-based reverse line blot (RLB) assay, a single-step PCR, and a nested PCR. Also, we explored the impacts of different DNA polymerase enzymes on the results based on gel electrophoresis and hybridization. The PCR results by gel electrophoresis in the single-step PCR depended on which DNA polymerase was used. All samples were negative with AmpliTaq Gold DNA polymerase, and 54.5% (36 of 66) were positive with the conventional Taq DNA polymerase. All samples were negative after hybridization with a C. pneumoniae-specific probe. In the nested PCR, all specimens were negative by gel electrophoresis and after hybridization. The RLB assay failed to detect C. pneumoniae in any specimen; however, 20 specimens were Chlamydia sp. positive. The sequence analysis of six of these samples demonstrated Chlamydia-like organisms. RLB detected Chlamydia sp. DNA in water and in the elution buffer after passage of the Qiagen columns (11 of 40). This study identified factors that may influence the detection of C. pneumoniae DNA in vascular tissues and consequently bias the perception of a link between C. pneumoniae and vascular diseases. The following are strongly recommended: to use DNA polymerases that have to be activated, to decontaminate with dUTP-uracil-DNA glycosylase, to hybridize with specific probes, to include sufficient controls, and to use molecular grade water.

Bacteriophages in autoimmune disease and other inflammatory conditions

There are several autoimmune diseases and other inflammatory conditions where an infectious aetiology is suggested by the epidemiology, clinical course and pathological findings. Many candidate bacteria and viruses have been considered as potential aetiological agents but mostly without firm proof. Bacteriophages are viruses that infect bacteria and may be found wherever bacteria are located, but would not be detected unless specifically sought. They have not previously been considered to be pathogens. Bacteriophages are immunogenic and therefore could play a role in the pathogenesis of autoimmune and other inflammatory diseases by acting as antigens on epithelial surfaces, bound to antibody as immune complexes, through molecular mimicry or possibly as superantigens.

Antibody levels against Chlamydia pneumoniae and outcome of roxithromycin therapy in patients with acute myocardial infarction. Results from a sub-study of the randomised Antibiotic Therapy in Acute Myocardial Infarction (ANTIBIO) trial

BACKGROUND

Results of studies concerning prevention of cardiovascular disease by treatment with macrolide antibiotics targeting C. pneumoniae infection are still controversial. This study describes the results of different tests for infection with C. pneumoniae as well as the effect of treatment with roxithromycin in patients with acute myocardial infarction (AMI) in relation to their serostatus against C. pneumoniae.

METHODS

We analysed blood of 160 patients who came from the ANTIBIOtic therapy after an AMI ( ANTIBIO-) study, a prospective, randomised, placebo-controlled, double-blind study to investigate the effect of roxithromycin 300 mg/OD for 6 weeks in patients with an AMI. Anti- Chlamydia IgG-, IgA-, and IgM-antibodies of these patients were analysed by means of different test systems.

RESULTS

There was a good correlation between the two IgG and IgA methods (r = 0.900, p < 0.001 and r = 0.878, p < 0.001, respectively), but marked differences in the prevalence of positive tests. This resulted in only moderate concordance values, as expressed by the Kappa coefficients, for IgG kappa = 0.611 (95% CI = 0.498-0.724, p < 0.001) and for IgA kappa = 0.431 (95% CI: 0.322-0.540, p < 0.001). No significant association between positive C. pneumonia titers and the combined clinical endpoint during the 12 month follow-up could be found. In all test systems used, patients with positive anti- C. pneumoniae titers did not benefit from roxithromycin therapy (p = ns).

CONCLUSION

Depending on the test system used, there are large differences in the prevalence of anti- C. pneumoniae seropositive patients. Clinical events during the 12 month follow-up after AMI did not depend on serostatus against C. pneumoniae and treatment with roxithromycin did not influence these events, independently of the serostatus against C. pneumoniae. However, the power of this subgroup analysis was low to detect small but significant differences.

Asymptomatic carotid atherosclerosis is associated with circulating chlamydia pneumoniae DNA in younger normotensive subjects in a general population survey

OBJECTIVE

Chlamydia pneumoniae infection has been associated with atherosclerosis, but serodiagnosis is unreliable in predicting vascular infection. Direct detection of circulating chlamydial DNA in peripheral blood mononuclear cells (PBMCs) was thus evaluated as a marker for cardiovascular risk in a general population survey using the common carotid intima-media thickness (IMT) as surrogate marker of asymptomatic atherosclerosis.

METHODS AND RESULTS

C pneumoniae DNA in PBMCs was determined by nested polymerase chain reaction and associated with IMT for 1032 healthy participants of a general population survey who were within the highest or lowest IMT distribution quartile. C pneumoniae DNA was more prevalent in those with increased IMT (13.4% versus 10.7%), but this was not significant in univariate and of borderline significance in multivariate analysis. Testing for potential effect modifications by known strong determinants of an increased IMT in group interaction analysis revealed an independent association between C pneumoniae DNA and IMT in normotensive subjects (odds ratio [OR], 2.06; 95% CI, 1.05 to 4.03; P=0.04) and in those <70 years old (OR, 1.84; 95% CI, 1.06 to 3.19; P=0.03).

CONCLUSIONS

Asymptomatic atherosclerosis is associated with circulating C pneumoniae DNA independently of classical cardiovascular risk factors in normotensive subjects and those <70 years old. C pneumoniae has been implicated in atherogenesis. We determined the association of chlamydial DNA in peripheral blood mononuclear cells with the carotid intima-media thickness from 1032 healthy subjects from a general population survey. A stratified group interaction analysis revealed an independent association in normotensive subjects and those <70 years old.

Effect of levofloxacin on the viability of intracellular Chlamydia pneumoniae and modulation of proinflammatory cytokine production by human monocytes

Although antibiotics are known to affect the intracellular growth of Chlamydia pneumoniae in acute infections, their efficacy in therapy for chronic infections, including atherosclerosis, remains debatable. Human monocyte-derived macrophages (MDM) obtained from monocytes of healthy donors were infected with C. pneumoniae AR-39 and treated with levofloxacin (8 microg/mL) immediately after infection (0 hours) or 24 hours after infection. Levofloxacin treatment at 24 hours, but not at 0 hours, resulted in a significant decrease in the number of C. pneumoniae inclusions within the MDM (p < 0.05). Also decreased were concentrations of proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and IL-8 in the extracellular medium (p < 0.01). Viable counts in titrations remained similar to those in untreated controls. In summary, levofloxacin administered to MDM at serum-attainable levels 24 hours after C. pneumoniae infection significantly decreased inclusion counts and proinflammatory cytokine production, but did not eliminate the C. pneumoniae infection.

Genetic and culture-based approaches for detecting macrolide resistance in Chlamydia pneumoniae

Three clinical Chlamydia pneumoniae isolates for which the MIC of azithromycin increased after treatment were investigated for genetic evidence of macrolide resistance. Attempts to induce antibiotic resistance in vitro were made. No genetic mechanism was identified for the phenotypic change in these C. pneumoniae isolates. No macrolide resistance was obtained in vitro.

Chlamydia Pneumoniae Seropositivity and Cardiovascular Risk Factors: The InCHIANTI Study

OBJECTIVES

To assess the prevalence of Chlamydia pneumoniae (CP) seropositivity and test the hypothesis that CP infection (CPI) is associated with cardiovascular (CV) risk factors and levels of inflammatory biomarkers.

DESIGN

Cross-sectional survey.

SETTING

Representative sample of the residents of Greve in Chianti and Bagno a Ripoli, two small towns located in the Chianti geographic area (Tuscany, Italy).

PARTICIPANTS

A total of 1,304 (age-range: 20-103, 79% aged> or =65) participants of the InCHIANTI study.

MEASUREMENTS

CP seropositivity was assessed using immunofluorescence. Previous CPI was defined as immunoglobulin (Ig) G > or =1/16 and <1/256, and recent CPI was defined as IgG > or =1/512 or IgM > or =1/16. Inflammatory markers included interleukin (IL)-6, soluble IL-6 receptor (sIL-6r), tumor necrosis factor-alpha (TNF-alpha), IL-1beta, IL-1 receptor antagonist (IL-1ra), iron, ferritin, and C-reactive protein (CRP). CV risk factors included smoking, body mass index (BMI), lipid profile, and hypertension.

RESULTS

The prevalence of CP seropositivity was 75%, increased with age, and was higher in men than in women (P<.01). CPI was not associated with IL-1beta, IL-1ra, iron, ferritin, CRP, BMI, lipids, and smoking. After adjusting for age and sex, previous or recent CPI was associated with higher TNF-alpha (P<.01), IL-6 (P<.03), sIL-6R (P<.01), and hypertension (P<.02). In additional age and sex-adjusted models, the associations between CPI and TNF-alpha, IL-6, sIL-6r, and hypertension appeared to be mutually independent.

CONCLUSION

CP seropositivity is highly prevalent in the older population and is a significant, independent correlate of hypertension and circulating levels of TNF-alpha, IL-6, and sIL-6r.

Effects of fluoroquinolones on the migration of human phagocytes through Chlamydia pneumoniae-infected and tumor necrosis factor alpha-stimulated endothelial cells

The anti-inflammatory activities of three quinolones, levofloxacin, moxifloxacin, and gatifloxacin, were investigated with an in vitro model of transendothelial migration (TEM). Human umbilical vein endothelial cells (HUVEC) were seeded in Transwell inserts, treated with serial dilutions of antibiotics, infected with Chlamydia pneumoniae, or stimulated with tumor necrosis factor alpha (TNF-alpha). Neutrophils or monocytes were also preincubated with serial dilutions of each antibiotic. TEM was assessed by light microscopic examination of the underside of the polycarbonate membrane, and levels of interleukin-8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) were measured by enzyme-linked immunosorbent assay. In HUVEC infected with C. pneumoniae or stimulated with TNF-alpha, all fluoroquinolones significantly decreased neutrophil and monocyte TEM, compared to antibiotic-free controls. Moxifloxacin and gatifloxacin produced a significant decrease in IL-8 in C. pneumoniae-infected and TNF-alpha-stimulated HUVEC; however, moxifloxacin was the only fluoroquinolone that produced a significant decrease in MCP-1 levels under both conditions. Results from this study indicate similarities in the anti-inflammatory activities of these fluoroquinolones, although no statistically significant decrease in chemokine secretion was observed when levofloxacin was used. Mechanisms of neutrophil and monocyte TEM inhibition by fluoroquinolone antibiotics are unknown but may be partially due to inhibition of IL-8 and MCP-1 production, respectively.

Chlamydia pneumoniae decreases smooth muscle cell proliferation through induction of prostaglandin E2 synthesis

Chlamydia pneumoniae may modulate the proliferation of smooth muscle cells (SMC) in atherosclerotic plaques. Conditioned medium from C. pneumoniae-infected SMC decreased the proliferation of uninfected SMC. Treatment of infected cells with the cyclooxygenase-2 inhibitor NS-398 [N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide] suppressed the up-regulation of prostaglandin E(2) (PGE(2)) and abolished the antimitogenic effect of conditioned medium, suggesting that C. pneumoniae can decrease SMC proliferation via stimulation of PGE(2) synthesis.

Chlamydia pneumoniae and Atherosclerosis: No Way-Out or Long Way?

Recently, Chlamydia pneumoniae is the microorganism frequently implicated in the infection-based inflammatory atherogenous hypothesis. Although in vitro experimental data and initial sero-epidemiologic, pathology-based studies and antibiotic trials supported this interesting hypothesis, later data are conflicting. Some confounding factors are the causes of uncertainty; lacking of standard methods for C. pneumoniae detection, co-existence of other atherosclerotic risk factors and anti-inflammatory effects of antibiotics used in clinical trials seem to be the principal ones. Standardization of methodology used, antibiotic trials with a different orientation-design and a vaccine preparation that eventually will be tested in clinical trials with a long follow-up, should provide a definite answer regarding the probability C. pneumoniae to be a main, a secondary or an irrelevant factor to atherosclerosis. Studies linking C. pneumoniae to inflammation and accelerated atherosclerosis in renal failure patients are accumulated but limitations are similar to the above mentioned.

Comparison of quantitative and semiquantitative enzyme-linked immunosorbent assays for immunoglobulin G against Chlamydophila pneumoniae to a microimmunofluorescence test for use with patients with respiratory tract infections

We previously reported a high degree of variation in the sensitivities of serodiagnostic kits for the detection of Chlamydophila pneumoniae in sera from healthy donors. Since a low predictive value of a test can impair its diagnostic value, we have extended our studies to samples from patients with pneumonia. We focused on the most promising enzyme-linked immunosorbent assays (ELISAs) (SeroCP and SeroCP Quant; Savyon) identified in our previous study and included a new ELISA (sELISA; Medac). The agreement between all ELISAs for immunoglobulin G (IgG) and a reference microimmunofluorescence (MIF) test for IgG (SeroFIA; Savyon) was > or = 90% for a collective of 80 patients. The positive predictive values were all > or = 93%. The negative predictive values ranged from 68 to 83%. False-negative results were obtained only for samples that had low titers in the MIF test. The correlation of the IgG antibody titers determined by the MIF and SeroCP Quant tests was high (r(sp) = 0.9). Since the semiquantitative SeroCP and quantitative SeroCP Quant ELISAs achieved the highest sensitivities, they were evaluated further by using a second batch of sera from 50 patients with predominantly medium and low antibody titers in the MIF test and a control collection of sera from 80 children with negative MIF results. Again, the tests showed a high concordance with the MIF results (96%), and the antibody titers in the SeroCP Quant and MIF tests correlated well (r(sp) = 0.8). The specificities determined with the negative sera were > or = 99% for the SeroCP Quant test and 86% for the SeroCP test. These results show that ELISAs that are fast and objective deliver seroprevalence results, sensitivities, and specificities that are very similar to those of the MIF test.

Immunohistostaining assays for detection of Chlamydia pneumoniae in atherosclerotic arteries indicate cross-reactions with nonchlamydial plaque constituents

Detection of Chlamydia pneumoniae antigens in PCR-negative atheromata by immunohistochemistry assays has given rise to controversies regarding a link between the bacterium and atherosclerosis. One hundred ninety-seven human arterial segments removed surgically were examined for C. pneumoniae DNA by conventional PCR with three different primer pairs and by real-time PCR in two different laboratories. No C. pneumoniae DNA was detected. Eighty atherosclerotic lesions were studied by immunohistochemistry assays. Immunoreactivity for C. pneumoniae was frequently present but was not related to the extent of atherosclerosis. Mammary arteries showed immunoreactivity. Serial sections of 17 atheromata were analyzed by Western blotting, histological staining, and UV fluorescence microscopy. Chlamydial proteins were not detected. The sites with positive results by C. pneumoniae immunohistostaining assays precisely matched the sites with autofluorescent ceroid deposits. Immunoblotting and antigenic staining for C. pneumoniae were negative in tests with fetal aortas. The absence of C. pneumoniae DNA in human atherosclerotic lesions, together with negative results for C. pneumoniae proteins by Western blotting analysis, and the perfect matching of C. pneumoniae immunoreactive sites with sites with autofluorescent ceroid deposits suggest a nonspecific reactivity of antichlamydial antibodies with plaque constituents. On the basis of the results of the present study, there are no arguments for an etiologic role of C. pneumoniae in atherosclerosis.

Endothelial Chlamydia pneumoniae infection promotes oxidation of LDL

The bacterium Chlamydia pneumoniae chronically infects atheromatous lesions and is linked to atherosclerosis by modifying inflammation, proliferation, and the lipid metabolism of blood monocytes. As continuous LDL modification in the vascular intima is crucial for atherogenesis we investigated the impact of endothelial infection on LDL oxidation. HUVEC were infected with a vascular C. pneumoniae strain. Supernatants of infected cells but not cell lysates increased lipid peroxidation products (6.44 vs 6.14 nmol/ml, p<0.05) as determined by thiobarbituric acid reacting substances assay. Moreover, supernatants rendered human LDL more susceptible to oxidation as shown in a copper-ion catalysed LDL oxidation assay by a 16% reduction of LDL resistance against pro-oxidative stimuli (p<0.05). Chlamydial infection of vascular endothelial cells releases acellular components that convert LDL to its proatherogenic form and reduce its resistance against oxidation. Foci of chronic endothelial chlamydial infection may thus continuously contribute to the dysregulated lipid metabolism that promotes atherogenesis.

[Infectious features of atherosclerosis]

As an inflammatory focus, the atherosclerotic plaque is viewed as a response to aggressions. Suppressing these causal injuries appears as the best means for preventing the disease. Infection is among the clues for answering the etiological challenge of atherosclerosis. Through direct or indirect, and specific or non specific pathways, some candidate viruses or bacteria are suspected to induce or stimulate plaque formation or complications. Yet, none of these working hypotheses has reached the level of proof required for establishing a valid concept. Although submitted to intensive investigations, anti-infectious drugs and antimicrobial vaccinations are still far-sighted expectations in the treatment and prevention of coronary artery disease.

Chlamydia pneumoniae together with collagenase-2 (MMP-8) in periodontal lesions

OBJECTIVE

Dental infections may be associated with subsequent atherosclerosis. In this regard we wanted to study if traces of Chlamydia pneumoniae can be found from deep periodontal pockets characterized with elevated collagenase-2 [matrix metalloproteinase (MMP)-8] levels in gingival crevicular fluid (GCF). Chlamydia pneumoniae has not previously been found to infect the oral cavity.

SUBJECTS AND METHODS

Subgingival samples of dental plaque were collected from 31 teeth in 12 adult periodontitis patients by means of sterile curettes and examined for C. pneumoniae using a quantitative PCR technique. GCF samples were also collected and assayed by an immunofluorometric assay (IFMA) for MMP-8.

RESULTS

Chlamydia pneumoniae RNA was demonstrated in a sample from one of the patients studied. Periodontal treatment eliminated the C. pneumoniae from the patient's subgingival dental plaque as well as reduced GCF MMP-8 level.

CONCLUSIONS

Our findings suggest that C. pneumoniae, which is not normally thought to be involved in periodontitis, can be found in dental plaque.

Development of radiocontrast agents for vascular imaging: progress to date

The revolution in molecular imaging techniques is profoundly changing the understanding of the pathophysiology and treatment of atherosclerosis. With these rapid changes there is an increasing demand for development of sensitive and well tolerated novel imaging agents that can be rapidly translated from small animal models into patients with atherosclerosis. Nuclear medicine and positron emission tomography techniques have the ability to detect and serially monitor a variety of biologic and pathophysiologic processes usually with tracer quantities of radiolabeled peptides, drugs, and other molecules at dosages free of pharmacologic adverse effects unlike the current generation of intravenous agents required for magnetic resonance imaging (MRI) and computed axial tomography (CT) scanning. A representative sampling of the wide array of radiopharmaceuticals developed specifically for radionuclide imaging of atherosclerosis, that have been approved for clinical use and those in pre-clinical trials, have been reviewed in this article. The presence of an inflammatory stimulus increases expression of CC (cysteine-cysteine motif) chemokine receptor (CCR)-2 on monocytes and macrophages, and somatostatin receptors on T lymphocytes. Radiolabeled monocyte chemoattractant protein (MCP)-1 binds with high affinity to CCR-2 and can be used to detect subacute and chronic inflammatory lesions. Similarly, radiolabeled octreotide or depreotide can be used to detect activated T lymphocytes which may identify the vulnerable plaque. Animal models indicate that (99m)Tc-annexin V, (125)I-MCP-1 and [(18)F]-fluoro-2-deoxyglucose are effective in identifying apoptotic cell death, macrophage infiltration and metabolic activity in atheromatous lesions, respectively. Expression of alpha(v)beta(3) integrin is increased in activated endothelial cells and vascular smooth muscle cells after vascular injury, and alpha(v)beta(3) integrin is minimally expressed on smooth muscle cells and is not expressed on quiescent epithelial cells. Radiolabeled high-affinity peptides can be used to target the alpha(v)beta(3) integrin and visualize areas of vascular damage. Advances in technology such as the micro-single photon emission computed tomography (microSPECT) have the potential to overcome the drawbacks of older CT and MRI methodologies, such as lack of biologically relevant ligands and compatible blood pool contrast agents for imaging. Despite these advances in imaging technology, the small size of atheromatous lesions makes it difficult to detect using external imaging techniques. Therefore, recently there has been renewed interest in the use of intravascular catheter-based radiation detectors.

Is Chlamydia pneumoniae infection associated with stroke in children with sickle cell disease?

BACKGROUND

Stroke is often a devastating complication of sickle cell disease (SCD). Most children with SCD-related stroke have stenotic and occlusive disease of cerebral blood vessels due to intimal hyperplasia. This hyperplasia is hypothesized to result from an inflammatory response similar to that in atherosclerosis and has been attributed to infection by Chlamydia pneumoniae.

OBJECTIVE

To determine whether C pneumoniae infection is associated with stroke and cerebrovascular disease, including transient ischemic attacks and abnormal transcranial Doppler examinations, in children with SCD.

METHODS

Children with SCD on chronic transfusion due to a history of stroke, transient ischemic attack, or abnormal transcranial Doppler; children with SCD without stroke; healthy controls; and children being transfused for other reasons were enrolled. Peripheral blood and nasopharyngeal (NP) swab specimens were collected from all patients. In patients on transfusion, pretransfusion specimens and samples from the unit of packed red blood cells being transfused were obtained. Peripheral blood monocytic cells (PBMCs) and NP swab specimens were cultured for C pneumoniae in HEp-2 cells. C pneumoniae polymerase chain reaction was performed on PBMCs with a nested touch-down method with primers from the omp-1gene (in duplicate) and a second real-time polymerase chain reaction by using 16S ribosomal RNA primers.

RESULTS

C pneumoniae DNA was detected in the PBMCs of 1 of 14 (7.1%) children with SCD on chronic transfusion, 1 of 10 (10%) sickle cell controls, 1 of 10 (10%) healthy controls, and none of the 5 children receiving chronic transfusion for other reasons. It was not detected in specimens from transfusion units. One child with SCD and stroke, 1 sickle cell control, and 1 transfusion control had positive NP cultures for C pneumoniae. C pneumoniae DNA was not detected in their PBMCs, and all 3 children were asymptomatic. C pneumoniae was not detected by culture of PBMCs from any of the patients after 7 passages.

CONCLUSION

Stroke in children with SCD does not seem to be associated with C pneumoniae infection in our population.

Chlamydia pneumoniae infections in asthma: clinical implications

Chlamydia pneumoniae is an intracellular pathogen that has been suggested to play a role in the pathology of asthma. However, so far none of the studies have provided clear evidence for a causative role of C. pneumoniae infections in asthma, although there is little doubt that chronic C. pneumoniae infection does aggravate asthma and should be treated. The diagnosis of C. pneumoniae infection is still a matter of concern for it is dependent on trained skilled personnel and can vary significantly between different diagnostic laboratories. This fact is also one of the major problems encountered when comparing epidemiological studies investigating the possible role of C. pneumoniae infections and their impact on the pathogenesis of other diseases. With regard to therapy, long-term treatment with macrolides is the best available method to eradicate C. pneumoniae. Successful therapy for C. pneumoniae, however, can also be complicated by the high possibility of de novo infection as epidemiological studies have shown that the prevalence of antibodies to C. pneumoniae increases with age in all populations studied. In the northern hemisphere the prevalence of C. pneumoniae is also affected by seasonal conditions. It is too early to draw any conclusions from the equatorial belt countries. The available data on C. pneumoniae in tropical countries indicate a much faster infection rate during early adulthood with 100% serological prevalence at an age greater than 25 years. This data, if confirmed, would argue against C. pneumoniae causing asthma since the asthma prevalence in those countries does not increase in a parallel pattern. An alternative interpretation of most studies could be that the increased rate of C. pneumoniae infections in patients with asthma results from a modified susceptibility towards the microorganism, due to yet unknown changes of the host cell's physiology. It should be kept in mind that increased prevalence of C. pneumoniae infection is not restricted to asthma. Further studies are needed to understand the role of C. pneumoniae, especially of chronic infection, in the pathogenesis of inflammatory diseases with a specific focus on the effect that the microorganism triggers in the infected host cell. Only when we understand what C. pneumoniae does to its host cell will we be able to judge its impact on the overall status of an affected patient, and this knowledge will help us to develop a successful therapy.