CPAF: a Chlamydial protease in search of an authentic substrate

Bacteria in the genus Chlamydia are major human pathogens that cause an intracellular infection. A chlamydial protease, CPAF, has been proposed as an important virulence factor that cleaves or degrades at least 16 host proteins, thereby altering multiple cellular processes. We examined 11 published CPAF substrates and found that there was no detectable proteolysis when CPAF activity was inhibited during cell processing. We show that the reported proteolysis of these putative CPAF substrates was due to enzymatic activity in cell lysates rather than in intact cells. Nevertheless, Chlamydia-infected cells displayed Chlamydia-host interactions, such as Golgi reorganization, apoptosis resistance, and host cytoskeletal remodeling, that have been attributed to CPAF-dependent proteolysis of host proteins. Our findings suggest that other mechanisms may be responsible for these Chlamydia-host interactions, and raise concerns about all published CPAF substrates and the proposed roles of CPAF in chlamydial pathogenesis.

Chlamydia are bacteria that invade eukaryotic host cells and live within a membrane-bound compartment called the chlamydial inclusion. Growth and survival of these important human and animal pathogens depends on extensive interactions with the host cell, which allow chlamydiae to acquire critical nutrients and to avoid host anti-microbial defenses. Chlamydiae are proposed to cause many of these host-pathogen interactions through the cleavage or degradation of host proteins by the chlamydial protease CPAF, which is secreted into the host cytoplasm. Here, we raise questions about the proposed roles of this virulence factor during infection, as well as its published substrates. We found that there was no detectable cleavage or degradation of 11 previously reported CPAF substrates in Chlamydia-infected cells and that CPAF-mediated proteolysis of these host proteins occurs during cell harvest and lysis. However, we still observed host-pathogen interactions previously attributed to CPAF proteolysis of these proteins, suggesting that Chlamydia is likely to cause these effects on the host cell through other mechanisms. Our findings call for a re-evaluation of all published CPAF substrates as well as the proposed roles of this protease in chlamydial pathogenesis.

Caspase-1 dependent IL-1β secretion is critical for host defense in a mouse model of Chlamydia pneumoniae lung infection

Chlamydia pneumoniae (CP) is an important human pathogen that causes atypical pneumonia and is associated with various chronic inflammatory disorders. Caspase-1 is a key component of the ‘inflammasome’, and is required to cleave pro-IL-1β to bioactive IL-1β. Here we demonstrate for the first time a critical requirement for IL-1β in response to CP infection. Caspase-1^−/− mice exhibit delayed cytokine production, defective clearance of pulmonary bacteria and higher mortality in response to CP infection. Alveolar macrophages harbored increased bacterial numbers due to reduced iNOS levels in Caspase-1^−/− mice. Pharmacological blockade of the IL-1 receptor in CP infected wild-type mice phenocopies Caspase-1-deficient mice, and administration of recombinant IL-1β rescues CP infected Caspase-1^−/− mice from mortality, indicating that IL-1β secretion is crucial for host immune defense against CP lung infection. In vitro investigation reveals that CP-induced IL-1β secretion by macrophages requires TLR2/MyD88 and NLRP3/ASC/Caspase-1 signaling. Entry into the cell by CP and new protein synthesis by CP are required for inflammasome activation. Neither ROS nor cathepsin was required for CP infection induced inflammasome activation. Interestingly, Caspase-1 activation during CP infection occurs with mitochondrial dysfunction indicating a possible mechanism involving the mitochondria for CP-induced inflammasome activation.

Among pregnant women with bacterial vaginosis, the hydrolytic enzymes sialidase and prolidase are positively associated with interleukin-1beta

OBJECTIVE

The objective of the study was to explore the mechanisms of local innate immunity induction and modulation in pregnant women with bacterial vaginosis (BV).

STUDY DESIGN

A total of 200 singleton pregnant women in early gestation (12 +/- 4 weeks) with BV (Nugent 7-10) without concurrent vaginal infections with Trichomonas vaginalis, Chlamydia trachomatis, Neisseria gonorrhoeae, syphilis, and yeast. Concentrations of vaginal interleukin (IL)-1beta and IL-8, the number of neutrophils, and the levels of sialidase and prolidase hydrolytic enzymes were determined in vaginal fluid.

RESULTS

Concentrations of vaginal IL-1beta had a strong positive correlation with levels of sialidase (P < .001) and prolidase (P < .001). Conversely, such enzymes were negatively correlated with the ratio of IL-8/IL-1beta (both P < .001) and were not significantly associated with concentrations of IL-8. Notably, the number of vaginal neutrophils had a negative correlation with sialidase (P = .007).

CONCLUSION

The strong induction of IL-1beta in BV-positive women appears to be associated with the production of the hydrolytic enzymes sialidase and prolidase by BV-associated bacteria. However, these 2 enzymes may inhibit the expected amplification of the proinflammatory IL-1beta cascade as evaluated by the down-regulation of the IL-8/IL-1beta ratio. A blunted response to IL-1beta signals may cause the poor rise of neutrophils, which is peculiar to BV. This impairment of local defense may contribute to increased susceptibility to adverse outcomes in BV-positive pregnant women.

[State of antioxidant defense and L-arginin-nitrogen oxide system in blood of patients with urogenital chlamydiosis]

The system L-arginine-nitrogen oxide plays a significant role in maintenance of the anti-infectious protection of an organism. A condition of the given system and activity of a enzymatic part of antiradical protection in the blood of patients with chlamydiosis has been studied. Obtained data specify an intensification of processes of an oxidizing way of recycling of arginine in an organism of patients. Substantial increase of NO-synthase activity and insignificant activity of arginase in the blood is revealed. The level of nitrite-anion in blood cells of patients authentically increases: 1.7 times in erythrocytes, and 1.4 times in lymphocytes. It is shown, that in patients with chlamydiosis glutathione system is intensified, that is evidenced by an increase glutathione-peroxidase activity and authentic increase of glutathione level. It is assummed that the established features of nitrogen oxide exchange play a significant role in formation of a pathological condition at urogenital chlamydia infections.

The extracellular signal-regulated kinase/mitogen-activated protein kinase pathway induces the inflammatory factor interleukin-8 following Chlamydia trachomatis infection

Diseases associated with Chlamydia infection, such as pelvic inflammatory disease and ectopic pregnancy, are due to inflammation-mediated tissue damage and scarring that occur after chronic or repeated infections. The inflammatory chemokine interleukin-8 (IL-8) is produced by Chlamydia-infected cells through an endogenous mechanism of activation, independent of soluble factors in the supernatant. The host signaling pathways necessary for this response are not understood, but the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK) has been shown to be activated at similar times as IL-8 mRNA up-regulation. The purpose of this study was to elucidate the MAPK pathways necessary to induce the endogenous IL-8 response to Chlamydia trachomatis infection of epithelial cells. IL-8 induced by infection with C. trachomatis L2 was shown to be dependent on ERK and independent of p38 and Jun N-terminal MAPK by use of chemical inhibitors of the signaling pathways. Persistent ERK activation during IL-8 mRNA production at 24 h postinfection was necessary to maintain the response. C. trachomatis serovar D also induced IL-8 in an ERK-dependent manner. We concluded that IL-8 induced during infection of epithelial cells is dependent on continual activation of ERK by C. trachomatis.

Inhibition of matrix metalloproteinases protects mice from ascending infection and chronic disease manifestations resulting from urogenital Chlamydia muridarum infection

Matrix metalloproteinases (MMP) are a family of host-derived enzymes involved in the turnover of extracellular matrix molecules. We have previously reported enhanced expression of matrix metalloproteinases in Chlamydia muridarum urogenital tract infection of female mice. Kinetics and patterns of MMP expression as well as enhanced expression in susceptible strains of mice in the prior study implied a role for MMP in pathogenesis. To explore this further, we infected a susceptible strain of mice (C3H/HeN) with C. muridarum and treated two groups of mice with either one of two chemical inhibitors of MMP (MMPi; captopril and a chemically modified tetracycline) and reserved infected sham-treated mice as controls. Neither of the treatments affected shedding of viable chlamydiae from the lower urogenital tract, but the administration of either MMPi protected mice from the formation of hydrosalpinx-a surrogate marker of oviduct occlusion and infertility. Interestingly, the mechanism of protection for mice treated with chemically modified tetracycline 3, appeared to be related to prevention of ascending upper genital tract infection. These results imply that MMP are involved in pathogenesis of chlamydial infection in this model by mediating ascension of the infection into the upper genital tract.

Chlamydia pneumoniae infection of microglial cells in vitro: a model of microbial infection for neurological disease

Chlamydia pneumoniae is the aetiological cause of a wide variety of chronic inflammatory diseases and may be associated with neurological disease. Microbiological and immunological aspects of the interaction between C. pneumoniae and the central nervous system (CNS) are not well understood because of the lack of a suitable infection model for neuronal studies. In the present study, an in vitro C. pneumoniae infection model was developed in the established microglial cell line EOC 20. Infection of the cells resulted in obvious induction of proinflammatory cytokines. The infection also selectively induced matrix metalloproteinase-9 (MMP-9) but not MMP-2. Moreover, beta interferon, which is known to modulate CNS disease, inhibited induction of MMP-9 following C. pneumoniae infection. These results support the view that C. pneumoniae infection may be associated with marked alteration of the ability of microglial cells to enhance cytokine production as well as induction of an MMP.

Role of matrix metalloproteinase-7 in the modulation of a Chlamydia trachomatis infection

To determine the role of matrix metalloproteinase-7 (MMP-7) in the pathogenesis of chlamydial infection, C57BL/6 wild-type (WT) and MMP-7 knockout (KO) mice were infected intravaginally with Chlamydia trachomatis mouse pneumonitis (MoPn). Over a period of 6 weeks postinfection, various organs were cultured for C. trachomatis. Other infected animals were mated to assess their fertility status. No significant differences were observed between WT and KO mice in the number of animals with positive vaginal cultures, length of time of C. trachomatis shedding, or the number of C. trachomatis inclusion-forming units (IFU) recovered from their genital tracts. Likewise, the number of animals with hydrosalpinx, and the fertility rates and the number of embryos per mouse, were similar in WT and KO mice. Cultures from the spleen, lungs, kidneys and large intestine yielded similar numbers of IFU from WT and KO mice. However, the number of C. trachomatis IFU recovered from the small intestine of KO mice was significantly higher than that recovered from the small intestine of WT mice at 2 weeks postinfection. Because MMP-7 KO mice are deficient in active intestinal alpha-defensins, the results suggest that these components play a role in regulating colonization of the gastrointestinal tract by Chlamydia. By contrast, MMP-7 is dispensable in the progression and resolution of the genital tract infection.

Inhibition of chlamydiae by primary alcohols correlates with the strain-specific complement of plasticity zone phospholipase D genes

Members of the genus Chlamydia are obligate intracellular pathogens that have a unique biphasic developmental cycle and interactions with host cells. Many genes that dictate host infection tropism and, putatively, pathogenic manifestations of disease are clustered in a hypervariable region of the genome termed the plasticity zone (PZ). Comparative genomics studies have determined that an uncharacterized family of PZ genes encoding orthologs of eukaryotic and prokaryotic members of the phospholipase D (PLD) enzyme family varies among chlamydiae. Here, we show that the PZ PLD (pzPLD) of Chlamydia trachomatis are transcribed during both normal and persistent infection and that the corresponding PLD proteins are predominantly localized in reticulate bodies on the inner leaflet of the inclusion membrane. Further, we show that strains of chlamydiae encoding the pzPLD, but not a strain lacking these genes, are inhibited by primary alcohols, potent PLD inhibitors, during growth in HeLa 229 cells. This inhibitory effect is amplified approximately 5,000-fold during recovery from persistent infection. These findings suggest that the chlamydial pzPLD may be important, strain-specific, pathogenesis factors in vivo.

Comparison of gamma interferon-mediated antichlamydial defense mechanisms in human and mouse cells

Gamma interferon (IFN-gamma)-induced effector mechanisms have potent antichlamydial activities that are critical to host defense. The most prominent and well-studied effectors are indoleamine dioxygenase (IDO) and nitric oxide (NO) synthase. The relative contributions of these mechanisms as inhibitors of chlamydial in vitro growth have been extensively studied using different host cells, induction mechanisms, and chlamydial strains with conflicting results. Here, we have undertaken a comparative analysis of cytokine- and lipopolysaccharide (LPS)-induced IDO and NO using an extensive assortment of human and murine host cells infected with human and murine chlamydial strains. Following cytokine (IFN-gamma or tumor necrosis factor alpha) and/or LPS treatment, the majority of human cell lines induced IDO but failed to produce NO. Conversely, the majority of mouse cell lines studied produced NO, not IDO. Induction of IDO in human cell lines inhibited growth of L2 and mouse pneumonitis agent, now referred to as Chlamydia muridarum MoPn equally in all but two lines, and inhibition was completely reversible by the addition of tryptophan. IFN-gamma treatment of mouse cell lines resulted in substantially greater reduction of L2 than MoPn growth. However, despite elevated NO production by murine cells, blockage of NO synthesis with the l-arginine analogue N-monomethyl-l-arginine only partially rescued chlamydial growth, suggesting the presence of another IFN-gamma-inducible antichlamydial mechanism unique to murine cells. Moreover, NO generated from the chemical nitric oxide donor sodium nitroprusside showed little direct effect on chlamydial infectivity or growth, indicating a natural resistance to NO. Finally, IFN-gamma-inducible IDO expression in human HeLa cells was inhibited following exogenous NO treatment, resulting in a permissive environment for chlamydial growth. In summary, cytokine- and LPS-inducible effectors produced by human and mouse cells differ and, importantly, these host-specific effector responses result in chlamydial strain-specific antimicrobial activities.

Expression of matrix metalloproteinases subsequent to urogenital Chlamydia muridarum infection of mice

The central hypothesis of this study was that matrix metalloproteinases (MMPs) would be enhanced following murine chlamydial infection and that their expression would vary in mouse strains that differ in their susceptibility to chronic chlamydia-induced disease. To address this hypothesis, female C3H/HeN and C57BL/6 mice were infected intravaginally with Chlamydia muridarum. Uterine and oviduct tissues were assessed for transcription of MMP genes and their tissue inhibitors. An increased activity of MMP genes relative to preinfection tissues was observed in the C3H/HeN mice when compared to C57BL/6 mice. Using gelatin zymography, we detected constitutive MMP-2 activity in both strains of mice but an increase in MMP-9. Casein zymography indicated the presence of two elastase-like activities consistent with MMP-12 and possibly MMP-7. Western blotting and antigen capture enzyme-linked immunoassay also confirmed an increase in MMP-9 but constitutive MMP-2 expression subsequent to the infection in both strains of mice. In C57BL/6 mice, MMP-9 was present in monomer and dimer form throughout the 56-day monitoring period. C3H/HeN mice produced dimeric MMP-9, but increases in the monomer form were also observed through day 14. Post-translational modification of MMP-9 between the two strains also differed. Immunohistochemistry revealed neutrophils as a prominent source for MMP-9 in both strains of mice. We conclude that differences in the relative expression and activity of MMPs, particularly MMP-9, occur in mice differing in their susceptibility to the development of chronic chlamydial disease. These differences may account for disparate outcomes with regard to chronic sequelae of the disease.

Up-Regulation of the JAK/STAT1 Signal Pathway duringChlamydia trachomatisInfection

Chlamydia trachomatis infection is the most common cause of sexually transmitted disease, leading to female pelvic inflammatory disease and infertility. The disease process has been linked to cellular response to this bacterial pathogen. This obligate intracellular pathogen infects macrophages, fibroblast cells, and epithelial and endothelial cells. We show in this study that infection of cervical epithelial cells, the primary target of Chlamydia trachomatis, leads to up-regulation and activation of the JAK/STAT signal pathway. Specifically, Chlamydia trachomatis infection of HeLa 229 cells selectively induces STAT1, STAT2, and IFN-stimulated transcription factor 3gamma expression and promotes STAT1 activation. The up-regulation of STAT1 is dependent on bacterial replication, because treatment of infected cells with antibiotics prevents STAT1 up-regulation. By analysis of the gene transcriptional and cytokine expression profiles of host cells combined with the use of neutralizing Abs, we show that IFN-beta production is critical for STAT1 induction in epithelial cells. Finally, we demonstrate that the host up-regulates STAT1 to restrict bacterial infection, because Chlamydia propagates more efficiently in STAT1-null or STAT1 knockdown cells, whereas Chlamydia growth is inhibited in cells with up-regulated STAT1 expression. This study demonstrates that the infected cells up-regulate the host innate antimicrobial response to chlamydial infection. It also highlights the importance of cellular response by nonimmune cells in host clearance of chlamydial infection.

Salt in the wound: a possible role of Na+ gradient in chlamydial infection

Genome analysis has revealed the presence of key components of the Na(+) chemiosmotic cycle, including the primary Na(+) pump (Na(+)-translocating NADH:ubiquinone oxidoreductase), in the cytoplasmic membrane of two ubiquitous human pathogens, Chlamydia trachomatis and Chlamydiophyla pneumoniae. This observation seemed paradoxical in the case of obligatory intracellular parasites because the Na(+) cycle is thought to be primarily a mechanism that enhances the adaptive potential in free-living bacteria that are often facing drastic changes in the salinity and pH of the environment. We present a model suggesting that operation of the Na(+) cycle may play an important role in the course of chlamydial infection, when the Na(+) and H(+) homeostasis of the host cell become severely impaired. This introduces the intriguing possibility of the application of drugs targeting Na(+)-transporting enzymes to chlamydial infections, which are notoriously difficult to treat.

Matrix metalloproteinase-9 expression is associated with the presence of Chlamydia pneumoniae in human coronary atherosclerotic plaques

OBJECTIVE

To investigate the association between Chlamydia pneumoniae and matrix metalloproteinase-9 (MMP-9) in atherosclerotic plaques.

DESIGN

31 coronary atherosclerotic plaque specimens were studied by immunohistochemistry, polymerase chain reaction (PCR), and reverse transcription PCR for the presence of C pneumoniae antigen and genomic DNA, and of MMP-9 protein and transcripts.

RESULTS

Immunohistochemical analysis identified a strong association between the presence of C pneumoniae antigen and production of MMP-9 in coronary atherosclerotic plaques (p = 0.001). Furthermore, analysis of the intralesional amount of C pneumoniae and MMP-9 indicated an increased number of cells positive for MMP-9 in arterial sections that had increased C pneumoniae positivity (p < 0.05).

CONCLUSIONS

This study provides evidence of an association between expression of MMP-9 and the intravascular presence of C pneumoniae and may suggest a potential pathological mechanism whereby C pneumoniae may contribute to the progression of coronary atherosclerosis.

Intramolecular dimerization is required for the chlamydia-secreted protease CPAF to degrade host transcriptional factors

We previously identified a chlamydial protein designated CPAF (chlamydia protease/proteasome-like activity factor) that is secreted into host cell cytosol for degrading host transcription factors required for major histocompatibility complex antigen expression. Here we report that CPAF, synthesized as a 70-kDa proprotein, is processed into two fragments (designated CPAFn and CPAFc) to form intramolecular dimers that are much more stable than the naïve CPAF. Precipitation with antibodies that recognized CPAF dimers removed the proteolytic activity responsible for degrading host transcription factor RFX5 from chlamydia-infected host cell cytosol, while precipitation with antibodies that recognized free CPAF fragments alone did not remove this activity. Separation of CPAFn from CPAFc resulted in a loss of proteolytic activity. Furthermore, neither expressed full-length CPAF that was not processed nor coexpressed CPAFn and CPAFc fragments that failed to form dimers degraded RFX5. These observations demonstrate that intramolecular dimerization is required for CPAF to degrade host transcription factors, a strategy that is utilized by an obligate intracellular bacterial species to evade host defenses.

Cleavage of host keratin 8 by a Chlamydia-secreted protease

Chlamydiae have to replicate within a cytoplasmic vacuole in eukaryotic cells. Expansion of the chlamydia-laden vacuole is essential for chlamydial intravacuolar replication, which inevitably causes host cell cytoskeleton rearrangements. A cleavage fragment of keratin 8 corresponding to the central rod region was detected in the soluble fraction of chlamydia-infected cells. Since keratin 8 is a major component of the intermediate filaments in simple epithelial cells, cleavage of keratin 8 may increase the solubility of the host cell cytoskeleton and thus permit vacuole expansion in chlamydia-infected cells. A chlamydia-secreted protease designated CPAF (chlamydial protease/proteasome-like activity factor) was both necessary and sufficient for keratin 8 cleavage in chlamydia-infected cells, suggesting that chlamydiae have evolved specific mechanisms for modifying the host cell cytoskeleton.

4th meeting of the EU research network EUROME: from the identification of genes and cellular networks in murine models of arthritis to novel therapeutic intervention strategies in rheumatoid arthritis, London, UK, 9 March 2004

Rheumatoid arthritis (RA) is a common human disease with a prevalence of about 1% in most parts of the world. At the time of symptom onset it is difficult to predict the severity of subsequent disease course. After 2 years joint erosions are seen in most patients, and most patients become clinically disabled within 20 years. A recent meeting at the Kennedy Institute of Rheumatology (Imperial College, London) brought together representatives from several European centres of excellence, to discuss research funded by the EU Framework 5 Quality of Life Programme. This research network combines gene and protein expression profiling with different animal models of RA to identify cells, genes and pathways contributing to arthritis initiation, progression and chronicity. The studies discussed highlight the reality that collaboration between different research groups is the basis of groundbreaking research and, it is hoped, eventual new therapies for RA.

Nitric oxide synthase plays a role in Chlamydia pneumoniae-induced atherosclerosis

OBJECTIVE

Chlamydia pneumoniae infection has been associated with atherosclerosis, although the mechanisms by which C. pneumoniae contribute to atherogenesis remain unclear. Altered production of nitric oxide, a known bactericidal and anti-inflammatory agent, represents one possible mechanistic link. To examine this issue, a diet-induced, hyperlipidemic mouse model of early atherosclerosis was used.

METHODS

A series of intranasal inoculations of C. pneumoniae strain AR-39 were administered to mice lacking endothelial or inducible nitric oxide synthase and to normal controls. After 18 weeks on an atherogenic diet, atherosclerotic lesion area in the aortic sinus was measured using computer-assisted morphometry.

RESULTS

In the absence of C. pneumoniae infection, diet-fed eNOS(-/-) mice developed enlarged fatty streak lesions of borderline significance in comparison to uninfected, wild-type mice, while the lesion area in uninfected, diet-fed iNOS(-/-) mice did not differ significantly from lesion area in wild-type animals. In contrast, lesion area in infected eNOS(-/-) mice increased slightly, but not significantly in comparison to uninfected eNOS(-/-) mice. Lesion area in the infected iNOS(-/-) mice was significantly enlarged when compared to both uninfected iNOS(-/-) mice as well as to infected wild-type mice.

CONCLUSIONS

These data suggest that production of nitric oxide by eNOS protects against development of fatty streak lesions in uninfected hyperlipidemic mice, but does not offer additional protection in infected hyperlipidemic mice, while iNOS may play a protective role, thus limiting chlamydial exacerbation of fatty streak lesions.

Upregulation of extracellular matrix metalloproteinase inducer (EMMPRIN) and gelatinases in human atherosclerosis infected with Chlamydia pneumoniae: the potential role of Chlamydia pneumoniae infection in the progression of atherosclerosis

Chlamydia pneumoniae infection implicated as an important etiologic factor of atherosclerosis, especially in coronary artery disease (CAD), was found in vitro to be associated with the induction of matrix metalloproteinases (MMPs). An extracellular matrix metalloproteinase inducer (EMMPRIN)/ membrane-type 1 matrix metalloproteinase (MT1-MMP) system which induces and activates MMPs, is suggested to be functional and were upregulated in the failing myocardium. However, the upstream regulation of MMPs by C. pneumoniae within atheroma itself remains unclear. We evaluated the seroepidemiologic study of C. pneumoniae infection in CAD patients (n= 391) and controls (n=97) and performed histopathological and in vitro analysis in atherosclerotic vascular tissues obtained from patients with seropositive to C. pneumoniae (n=20), by using immunochemistry for C. pneumoniae, EMMPRIN/MT1-MMP, MMP-2, and MMP-9. The seropositive rates of both anti-C. pneumoniae IgG and IgA were 56.7% in CAD group and 43.3% in control group (P=0.033). Seropositive rate was increased in subgroups of CAD patients without conventional coronary risk factors compared to those with conventional risk factors. Immunoreactivities of EMMPRIN, MT1-MMP, MMP-2, and MMP-9 were increased in the atheromatous plaque itself, predominantly in immunoreactive macrophages/mononuclear cells to C. pneumoniae. Furthermore, Western blot analysis showed that EMMPRIN and MMP-2 were detected more prominently in atherosclerotic tissues infected with C. pneumoniae compared to control tissues. Zymographic analysis revealed that activities of MMP-2 and MMP-9 were more increased in atherosclerotic tissues infected with C. pneumoniae compared to control tissues. The present study demonstrated upstream regulation of MMPs can be induced by C. pneumoniae within atheromatous plaque itself. These findings help to understand the potential role of C. pneumoniae in the progression of atherosclerosis.

Chlamydia trachomatis enhances the expression of matrix metalloproteinases in an in vitro model of the human fallopian tube infection

OBJECTIVE

The sequelae of sexually transmitted Chlamydia trachomatis infection include fallopian tube scarring, which implies modification of the extracellular matrix. Our objective was to describe the production of two matrix metalloproteinases in response to chlamydial infection in vitro.

STUDY DESIGN

Human fallopian tube organ cultures were infected with Chlamydia, and the production of matrix metalloproteinases was assessed by gelatin zymography, antigen capture enzyme-linked immunosorbent assay, immunohistochemistry, and in situ zymography.

RESULTS

Significantly elevated levels of matrix metalloproteinase-2 and matrix metalloproteinase-9 were found in supernatants of infected segments. Immunohistochemistry and in situ zymography revealed that epithelial cells tended toward matrix metalloproteinase-2 production and that matrix metalloproteinase-9 exhibited a more diffuse stromal staining pattern.

CONCLUSION

Matrix metalloproteinase-2 and matrix metalloproteinase-9 are expressed in vitro in response to chlamydial infection. Enhanced matrix metalloproteinase production in some individuals in response to infection may lead to tubal scarring through the increased turnover and subsequent repair of the extracellular matrix.

The quantity of nitric oxide released by macrophages regulates Chlamydia-induced disease

Intracellular bacteria of the genus Chlamydia cause numerous typically chronic diseases, frequently with debilitating sequelae. Genetic determinants of disease susceptibility after infection with Chlamydia bacteria are unknown. C57BL/6 mice develop severe pneumonia and poor immunity against Chlamydia after moderate respiratory infection whereas BALB/c mice are protected from disease and develop vigorous Th1 immunity. Here we show that infected C57BL/6 macrophages release more NO synthesized by NO synthase 2 (NOS2) than BALB/c macrophages and have lower mRNA concentrations of arginase II, a competitor of NOS2 for the common substrate, l-arginine. Reduction, but not elimination, of NO production by incomplete inhibition of NOS2 abolishes susceptibility of C57BL/6 mice to Chlamydia-induced disease. Thus, the quantity of NO released by infected macrophages is the effector mechanism that regulates between pathogenic and protective responses to chlamydial infection, and genes controlling NO production determine susceptibility to chlamydial disease.

Chlamydia trachomatis persistence in the female mouse genital tract: inducible nitric oxide synthase and infection outcome

It was previously reported that female mice resolve a primary Chlamydia trachomatis urogenital infection independent of inducible nitric oxide synthase (iNOS). We now report that although iNOS-deficient (NOS2(-/-)) mice resolve culture-apparent infection in a fashion similar to that of normal control (NOS2(+/+)) mice, they sustain significantly increased rates of disease, as assessed by hydrosalpinx formation. PCR amplification of ompA followed by Southern blot detection of amplicands revealed the presence of chlamydial DNA in the lower genital tracts of both NOS2(-/-) and NOS2(+/+) mice at > or =120 days postinfection and in upper genital tract tissues at >120 days postinfection. However, only NOS2(-/-) mice shed low numbers of viable chlamydiae from the lower genital tract after immunosuppressive treatment at 120 days postinfection. When cultured primary murine lung fibroblasts were activated in the presence of gamma interferon (IFN-gamma), inhibition of chlamydial growth occurred in both NOS2(+/+) and NOS2(-/-) cells, but the inhibition was reversible after removal of the cytokine in the NOS2(-/-) primary cell culture only. The iNOS-independent inhibition was microbistatic but was independent of 2,3-indoleamine dioxygenase activity. We conclude that chlamydial DNA and antigens persist in mice subsequent to culture-apparent resolution. In addition, IFN-gamma induces in vivo inhibition of chlamydial growth through microbistatic mechanisms in the absence of iNOS activity, but in the presence of iNOS activity, IFN-gamma is microbicidal and effects eradication.

Endothelial dysfunction after repeated Chlamydia pneumoniae infection in apolipoprotein E-knockout mice

BACKGROUND

Arterial relaxation is largely regulated by endothelial nitric oxide (NO). Its diminished activity has been associated with incipient atherosclerosis. We investigated the endothelium-dependent relaxation of aorta in apolipoprotein E-knockout (apoE-KO) mice exposed to single or repeated Chlamydia pneumoniae inoculation.

METHODS AND RESULTS

Forty-eight apoE-KO mice, 8 weeks old, were inoculated intranasally with C pneumoniae (n=24) or saline (n=24) every 2 weeks over a 6-week period. Twenty mice (10 infected and 10 controls) were killed at 2 weeks and 6 weeks, respectively, after the first inoculation. The smooth muscle tone of aortic rings was measured in vitro at both time points. The norepinephrine-precontracted thoracic aortic rings were successively exposed to methacholine in the absence and presence of N:(G)-nitro-L-arginine methyl ester (L-NAME) and diclofenac. The methacholine-induced relaxation was attenuated in the infected mice at 6 weeks in both the absence and presence of L-NAME (P:<0.05 and P:<0.01, respectively). When administered together with L-NAME, diclofenac enhanced the relaxation of the L-NAME-pretreated aortas in infected mice at 2 weeks (P:<0.05) but not in noninfected mice. The relaxation response from infected mice tended to differ in the same manner at 6 weeks (P:<0.1). No intimal thickening was detected at either time point.

CONCLUSIONS

C pneumoniae impairs arterial endothelial function, and the NO pathway is principally involved. Cyclooxygenase-dependent vasoconstricting products may also account for the infection-induced impaired relaxation. These findings further support the role of C pneumoniae infection in atherosclerosis development.

Hydroxymethylglutaryl coenzyme A reductase inhibitors modify the inflammatory response of human macrophages and endothelial cells infected with Chlamydia pneumoniae

BACKGROUND

In patients with atherosclerosis, hepatic hydroxymethylglutaryl coenzyme A reductase (CSE) inhibitors may reduce the activation of inflammation. Because Chlamydia pneumoniae infection has been linked to coronary artery disease through the induction of plaque inflammation, we investigated whether cerivastatin affects the infection rate of human macrophages and endothelial cells (ECs) and their proinflammatory activation after chlamydial infection.

METHODS AND RESULTS

Macrophages were collected from the alveolar compartment of 6 volunteers and 10 patients with chronic bronchitis. ECs were obtained from 10 umbilical cords. The C. pneumoniae strain CWL was incubated with macrophages or ECs in the presence and absence of the CSE inhibitor cerivastatin. The infection rate was determined by immunofluorescence microscopy. The release of monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), and tumor necrosis factor (TNF)-alpha was quantified by ELISA. The release of oxygen radicals was determined by ferricytochrome assay. Infection rates were tendentially lower after the preincubation of macrophages with CSE inhibitors (17.2% versus 9. 3% and 18.2% versus 10.4%, respectively; P=NS). The secretion of MCP-1, IL-8, and TNF-alpha by infected macrophages from volunteers increased. Coincubation with cerivastatin resulted in significantly lower MCP-1 and IL-8 production, whereas the release of TNF-alpha remained unaffected. Similar effects regarding chemokine release were observed in ECs.

CONCLUSIONS

CSE inhibitors modify the inflammatory response of human immune cells to C. pneumoniae. This finding could be relevant for the therapeutic potential of CSE statins in patients with atherosclerosis and C. pneumoniae infection.

Reappraising the value of urine leukocyte esterase testing in the age of nucleic acid amplification

BACKGROUND

The leukocyte esterase (LE) test has a limited role in determination of empiric therapy for male patients screened for urethritis because of its poor positive predictive value in low (< 5%) prevalence settings. The recent advent of nucleic acid amplification testing of first-void urine (FVU) has dramatically increased the ease with which widespread screening for Chlamydia trachomatis and Neisseria gonorrhoeae can be performed, but the costs of such testing may be prohibitive. The LE test may therefore have a role in management of urethritis because of its high negative predictive value.

OBJECTIVES

To determine the sensitivity, specificity, and positive and negative predictive value of LE testing for the diagnosis of N. gonorrhoeae and C. trachomatis in male FVU specimens in a low-prevalence urban setting using a commercial polymerase chain reaction (PCR) as the gold standard.

METHODS

Data were obtained on men presenting to an urban sexually transmitted disease clinic over a 16-month period. Patients were included if an FVU had been tested for the presence of LE using a rapid dipstick, read by an automated urine analyzer, and the sample (either an FVU or urethral swab) had then been processed for the detection of N. gonorrhoeae and C. trachomatis by PCR.

RESULTS

Of 301 assessable patients, there were 14 cases of gonorrhoea, 21 cases of chlamydia, and 1 case of dual infection detected by PCR. Most men (245/301; 81.4%) were asymptomatic, of whom 12 of 245 (4.9%) had an infection detected compared with 24 of 56 (42.9%) in the symptomatic men (P < 0.001). Using a "< or = trace" cutoff, the overall value for the sensitivity of the LE test was 77.8% (95% confidence interval, 60.4-89.3), specificity 80.8% (75.4-85.2), positive predictive value 35.4% (25.2-47.1), and negative predictive value 96.4% (92.8-98.3).

CONCLUSIONS

The negative predictive value of the LE test may be of use in determining which patients should proceed to specific diagnosis by nucleic amplification methods (e.g., PCR or ligase chain reaction). By limiting testing to patients with positive LE results, cost savings may be made, enabling the technology to be used in a wider community setting. The value of the LE test in higher prevalence populations with access to nucleic amplification testing remains to be established.

Role of nitric oxide in the inhibition of cytochrome P450 in the liver of mice infected with Chlamydia trachomatis

In this study, we attempted to determine the effect of a systemic infection with Chlamydia trachomatis on cytochrome P450(CYP)-dependent metabolism in mice. Furthermore, we wanted to assess if these effects were mediated through NO. BALB/c(H-2d) female mice were inoculated intraperitoneally with the C. trachomatis mouse pneumonitis (MoPn) biovar, and induction of NO synthase (NOS) was detected by measuring [NOx] levels and inducible NOS protein content in peritoneal macrophages by Western blotting. Recovery of C. trachomatis from liver, lung, and spleen peaked at 4 days postinfection. Following cotreatment with N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, there was a significant increase in the intensity and the length of the infection. Six days after inoculation with C. trachomatis, CYP1A- and CYP2B-mediated metabolism in the liver of the mice was diminished up to 49% of control levels. However, when animals were treated with N(G)-nitro-L-arginine methyl ester at days 4 and 6 postinfection, the decrease in the metabolism of CYP1A and CYP2B was largely blocked. These results suggest that C. trachomatis infection can depress cytochrome P450 in a manner similar to other types of infections and that NO is likely to be a mediator of this depression. This finding may be of significance to patients taking drugs that are metabolized by phase I enzymes during infections with some bacteria such as C. trachomatis.

Use of ligase chain reaction with urine versus cervical culture for detection of Chlamydia trachomatis in an asymptomatic military population of pregnant and nonpregnant females attending Papanicolaou smear clinics

Ligase chain reaction (LCR) (Abbott Laboratories, Abbott Park, Ill.) with first-catch urine specimens was used to detect Chlamydia trachomatis infections in 465 asymptomatic military women attending clinics for routine Papanicolaou smear tests. Results were compared to results of cervical culture to determine the sensitivity of the urine LCR and the possible presence of inhibitors of amplification in pregnant and nonpregnant women. Discrepant results for LCR and culture were resolved by direct fluorescent antibody staining of culture sediments, two different PCR assays, and LCR for the outer membrane protein 1 gene. The prevalence of Chlamydia in specimens by urine LCR was 7.3% compared to 5% by culture. For 434 women with matching specimens, there were 11 more specimens positive by LCR than were positive by culture, of which all but one were determined to be true positives. There were four culture-positive, LCR-negative specimens, all from nonpregnant women. The sensitivity, specificity, and positive and negative predictive values of urine LCR after discrepant results were resolved were 88.6, 99.7, 96.9, and 99.0%, respectively. The sensitivity of culture was 71.4%. From the 148 pregnant women (prevalence by LCR, 6.8%), there were no patients who were cervical culture positive and urine LCR negative to indicate the presence in pregnant women of inhibitors of LCR. Additionally, a subset of 55 of the LCR-negative frozen urine specimens from pregnant women that had been previously processed in LCR buffer were inoculated with 5 cell culture inclusion forming units of C. trachomatis each and retested by LCR; all tested positive, indicating the absence of inhibitors of LCR in urine from these pregnant women. The use of LCR testing of urine specimens from asymptomatic women, whether pregnant or not, offers a sensitive and easy method to detect C. trachomatis infection in women.

Inhibition of apoptosis in chlamydia-infected cells: blockade of mitochondrial cytochrome c release and caspase activation

We report that chlamydiae, which are obligate intracellular bacterial pathogens, possess a novel antiapoptotic mechanism. Chlamydia-infected host cells are profoundly resistant to apoptosis induced by a wide spectrum of proapoptotic stimuli including the kinase inhibitor staurosporine, the DNA-damaging agent etoposide, and several immunological apoptosis-inducing molecules such as tumor necrosis factor-alpha, Fas antibody, and granzyme B/perforin. The antiapoptotic activity was dependent on chlamydial but not host protein synthesis. These observations suggest that chlamydia may encode factors that interrupt many different host cell apoptotic pathways. We found that activation of the downstream caspase 3 and cleavage of poly (ADP-ribose) polymerase were inhibited in chlamydia-infected cells. Mitochondrial cytochrome c release into the cytosol induced by proapoptotic factors was also prevented by chlamydial infection. These observations suggest that chlamydial proteins may interrupt diverse apoptotic pathways by blocking mitochondrial cytochrome c release, a central step proposed to convert the upstream private pathways into an effector apoptotic pathway for amplification of downstream caspases. Thus, we have identified a chlamydial antiapoptosis mechanism(s) that will help define chlamydial pathogenesis and may also provide information about the central mechanisms regulating host cell apoptosis.

The usefulness of screening for chlamydial trachomatis infection with cervical mucus leukocyte esterase

OBJECTIVE

To evaluate the ability of leukocyte esterase dipstick test (LET) performed in cervical mucus to predict direct immunofluorescent (DIF)-verified Chlamydia trachomatis (Ct) cervical infection.

METHOD

Eighty women with inflammatory cervico-vaginal smear were submitted to both an endocervical smear, to verify Ct cervicitis by DIF technique; and a cervical mucus sample to perform LET. Results of LET and DIF were matched.

RESULTS

Among 30 Chlamydial positive subjects, cervical mucus esterase test was positive in 28 (93.3%); while among 50 Chlamydial negative controls, esterase test was negative in 43 subject (86%). The sensitivity, specificity, positive and negative predictive values for LET were 93.3%, 86%, 80% and 95% respectively.

CONCLUSION

Cervical mucus LET is a simple, cost effective screening test, with promising accuracy, for Ct cervical infection among women with inflammatory cervico-vaginal smears.

Screening urine samples by leukocyte esterase test and ligase chain reaction for chlamydial infections among asymptomatic men

Urine samples from 358 asymptomatic males were screened for urethral inflammation by the leukocyte esterase (LE) test and for Chlamydia trachomatis by the ligase chain reaction (LCR). LE and LCR positivity rates were 7.5% (27 of 358 samples) and 2.8% (10 of 358 samples), respectively. Eight of the 10 LCR-positive samples were detected by the LE screening test. The urine LE prescreening test in combination with the LCR assay may be a reasonable approach for genitourinary chlamydial disease control.

Reduction of matrix metalloproteinase 8-neutrophil collagenase levels during long-term doxycycline treatment of reactive arthritis

The aim of this work was to determine whether human polymorphonuclear neutrophilic interstitial collagenase (matrix metalloproteinase 8 [MMP-8]) levels are reduced during long-term doxycycline treatment in humans with reactive arthritis. Serum MMP-8 levels were reduced (mean +/- standard error of the mean, 678.9 +/- 185.6 versus 491.2 +/- 144.8 ng of MMP-8 per ml), but not statistically significantly. However, the reduction of salivary MMP-8 levels was statistically significant (3,729 +/- 1,905.3 versus 1,866 +/- 780.0 ng of MMP-8 per ml, P < 0.05). This study demonstrated that a 2-month regimen of doxycycline can reduce MMP-8 levels in serum and especially in body fluids (i.e., saliva) containing inflammatory exudates and thus may contribute to reduced tissue destruction.

Chlamydia pneumoniae in Swedish patients

Chlamydia pneumoniae infections have earlier been described as mycoplasma-like illnesses in young people, and also appear to be associated with community-acquired pneumonia in adults. In this retrospective study, 12.2% (23/188) of patients with pneumonia who required hospitalization during the 3 years 1985-87 had serological evidence of recent C. pneumoniae infection. Many of these patients had symptoms similar to ornithosis. The most interesting finding was that half of the patients with a 4-fold IgG antibody titre rise to C. pneumoniae also had an increased alkaline phosphatase concentration.

Evaluation of an enzyme immunoassay (Chlamydiazyme) with confirmatory test for the detection of chlamydial antigen in urine from men

First catch urine specimens from 312 male patients were examined for the presence of chlamydial antigen by an enzyme immunoassay (Chlamydiazyme). Positive results were repeated and confirmed using a blocking assay. In addition, urethral swabs were examined by cell culture for Chlamydia trachomatis. Discrepant results were further analysed by direct immunofluorescence (IF) of the spun urine deposit. Paired specimens were positive from 26 subjects, and negative from 276 subjects. Eight paired specimens were urethral culture positive, and urine EIA negative. Two specimens, urine EIA positive but urethral culture negative, were positive on direct IF. The sensitivity, specificity, predictive value of a positive result, and predictive value of a negative result for urine EIA against cell culture and/or direct IF were 77.8%, 100%, 100% and 97.2% respectively.

[Comparison of cytology and ELISA in the research on cervical Chlamydia infection]

Papanicolaou smears from 100 woman with ELISA Chlamydia-positive (42) and negative (58) endocervical smears were examined. Chlamydial endocellular inclusions were found in 3 ELISA positive and 2 negative smears, with an evident low sensitivity (7%) of cytology in the diagnosis of the endocervical infection. Furthermore, by statistical analysis it is clear that a negative test doesn't add anything to the pre-test probability (prevalence) of the infection. On the other hand a positive pap-smear adds a poor information, if compared with immunoenzimathic assay and IF staining. Thus, the Papanicolaou smear can't be considered of diagnostic value for Chlamydial infection. Furthermore, it proves unsuitable even for screening programs on high-risk patients, concerning which the immunoenzymatic assay appears, as previously affirmed, the most suitable effort.

Serum adenosine deaminase in viral and bacterial pneumonia

We measured the activity of serum adenosine deaminase (ADA) in paired sera from 171 military conscripts with radiographically verified pneumonia. Patient serum samples were selected on the basis of serologic analyses identifying as single etiologic agents Streptococcus pneumoniae in 29 patients, Haemophilus influenzae in 7, Mycoplasma pneumoniae in 43, adenovirus in 24, influenza A or B in 12, and parainfluenza in 5 patients. In 14 patients Neisseria meningitidis and in 31 Chlamydia spp were considered the main etiologic agent. Compared with a control group of 45 healthy men, the ADA activity in patients with pneumonia was significantly higher (p less than 0.001) in all patient groups except those with meningococcal pneumonia. The highest ADA levels were seen in patients with pneumonia caused by M pneumoniae (27.4 +/- 9.7 U/L), Chlamydia spp (26.3 +/- 9.1 U/L), and adenovirus (28.5 +/- 10.9 U/L) compared with the controls (11.1 +/- 3.0 U/L). In patients with meningococcal pneumonia, the ADA activity was significantly decreased (p less than 0.001). Serum ADA activity probably reflects differences in cellular immune response to different infectious agents. The ADA determinations may give corroborative information on the etiologic agent of pneumonia.

Lack of specificity of Chlamydiazyme for detection of vaginal chlamydial infection in prepubertal girls

A 1-year prospective study was undertaken of 65 prepubertal girls referred for evaluation of sexual abuse or vulvovaginitis to compare Chlamydiazyme, an enzyme immunoassay (EIA), with culture for the detection of Chlamydia trachomatis i in vaginal specimens. Five (8%) of 65 patients were initially EIA-positive. On repeat sampling without intervening antibiotic treatment, 4 girls who were initially positive became negative and 1 remained persistently positive. Chlamydial cultures were negative in all patients. The patient with the persistently positive EIA also had Group A streptococcal vaginitis. We were able to demonstrate that some strains of Group A Streptococcus can cause a positive reaction with the EIA. Cross-reactions with other bacterial species are also known to occur. We therefore conclude that Chlamydiazyme is not specific for the detection of chlamydial infection in the vagina of prepubertal girls and, for medicolegal reasons, should not be used for evaluation of sexual abuse.

Leukocyte esterase activity in the rapid detection of urinary tract and lower genital tract infections in obstetric patients

Infections of the vagina and urinary tract are important problems for the obstetrician. Examination of the vaginal discharge and urine for the presence of leukocytes is an important part of the evaluation for vaginitis and urinary tract infections. Neutrophils contain several esterases that are not present in serum, urine, or vaginal secretions. These esterases are not influenced by bacteria, commonly used drugs, or variable compositions of urine or vaginal secretions. A prospective study was performed to assess the sensitivity and specificity of leukocyte esterase activity as measured by dipstick (Chemstrip 9, Biodynamics) for the prediction of vaginitis and urinary tract infections during pregnancy. Results were compared with those obtained from potassium hydroxide smears, wet preps, and urine cultures. The vaginal discharge and urine of 65 patients was tested for leukocyte esterase activity on their initial OB visit. Leukocyte esterase was 100% sensitive and 100% specific for detecting urinary tract infections. It was 100% sensitive and 90% specific for predicting vaginal infections. Trichomonas infections accounted for the positive leukocyte esterase results when the urine culture was negative. On the basis of this study we believe that leukocyte esterase activity is sufficiently sensitive and specific to permit use of this test as a rapid and inexpensive screening procedure for vaginitis and urinary tract infections.

[Superoxide dismutase and catalase activity in HeLa 229 cells infected with Chlamydia trachomatis]

Cytosolic superoxide dismutase (SOD) activity was found to increase with time during HeLa cell culture, this increase being due exclusively to Mn-SOD. Infection of the cells by Chlamydia trachomatis resulted in a further enhancement of this Mn-SOD activity, whereas cytosolic catalase activity was decreased in these infected cells. Superoxide (O-2.) being able to induce Mn-SOD and to inhibit catalase, these data suggest that Chlamydia trachomatis infection could be responsible for an increase in O-2. production by the infected HeLa cells.

Detection of DNA polymerase activity in Chlamydia psittaci

DNA polymerase activities of intact and disrupted suspensions of the mature infectious, extracellular elementary bodies of the meningopneumonitis strain of Chlamydia psittaci were studied. Intact elementary bodies failed to incorporate labeled thymidine triphosphate (TTP), but homogenates of the organisms did incorporate TTP into the acid insoluble fraction; the reaction continued at a linear rate for 60 min and the newly synthesized DNA hybridized exclusively with DNA derived from C. psittaci elementary bodies. Synthesized DNA sedimented in 2 fractions in alkaline sucrose gradients, one in the 50S region and the other in the 10S region, corresponding to molecular weights of 2 X 10(7) and 5 X 10(5) daltons, respectively.