Alteration of Chlamydia trachomatis biologic behavior in synovial membranes. Suppression of surface antigen production in reactive arthritis and Reiter's syndrome

Reactive arthritis: the convoluted history of Reiter's disease

Reactive arthritis, previously known as Reiter's Syndrome or Disease was a post-dysenteric, asymmetrical acute large joint polyarthritis, with fever, conjunctivitis, iritis, purulent urethral discharge, rash and penile soft tissue swelling. Although the eponym was given to Hans Reiter, various forms of the condition have been recorded in history a few hundred years before Reiter. Two French doctors, Noel Fiessinger (1881-1946) and Edgar Leroy (d. 1965), presented a paper at la Societe des Hopitaux-in Paris on the 8th December 1916 on dysentery in 80 soldiers on the Somme, and four of whom developed a "syndrome conjunctivo-uretro-synovial". Their paper was given 4 days before Reiter's presentation on 12th December 1916 at the Society of Medicine in Berlin, on a German army officer with an illness similar to those described by Fiessinger and Edgar Leroy. It is documented that Hans Reiter was one of a number of University professors who signed an oath of allegiance to Adolf Hitler in 1932. For socio-ethical reasons and for clinical utility, Reiter's syndrome is now known as reactive arthritis.

López Font F, A. Zayas Rodríguez F. Persistence in Chlamydia

Chlamydia spp. are important causes of acute and persistent/chronic infections. All Chlamydia spp. display a unique biphasic developmental cycle alternating between an infectious elementary body (EB) and a replicative form, the reticulate body (RB), followed by the multiplication of RBs by binary fission and progressive differentiation back into EBs. During its intracellular life, Chlamydia employs multiple mechanisms to ensure its persistence inside the host. These include evasion of diverse innate immune responses, modulation of host cell structure and endocytosis, inhibition of apoptosis, activation of pro-signaling pathways, and conversion to enlarged, non-replicative but viable “aberrant bodies” (ABs). Early research described several systems for Chlamydial persistence with a significant number of variables that make a direct comparison of results difficult. Now, emerging tools for genetic manipulations in Chlamydia and advances in global microarray, transcriptomics, and proteomics have opened new and exciting opportunities to understand the persistent state of Chlamydia and link the immune and molecular events of persistence with the pathogenesis of recurrent and chronic Chlamydial infections. This chapter reviews our current understanding and advances in the molecular biology of Chlamydia persistence.

Chlamydia in adolescent/adult reproductive management trial study (CHARM): Clinical core protocol

INTRODUCTION

Chlamydia trachomatis (CT) is a common sexually transmitted pathogen with significant reproductive health implications. Data are mounting that the bacterial communities that reside within the vagina, collectively termed the vaginal microbiota, aid in defense against sexually transmitted infections. Disruptions in the vaginal microbiota, such as during episodes of bacterial vaginosis, may increase susceptibility to infection. Herein, we describe the clinical core protocol for a NIH NIAID Cooperative Research Center titled Eco-Pathogenomic of Chlamydial Reproductive Tract Infection. The primary goals of the project are to describe the interrelationships between the urogenital microenvironment, the properties of the pathogen and immunologic responses of the host in men and women, and their association with clinical outcomes of CT infection in women.

METHODS

Men and women with confirmed genital CT infections were recruited to a number of study protocols, including cross-sectional and longitudinal sub-studies. Participants completed a demographic and sexual health questionnaire and underwent a physical exam at baseline. In the longitudinal study arms, biologic samples were collected daily, weekly, and monthly to determine the relationships between the vaginal microbiota, prevalent CT infection, re-infection and treatment.

DISCUSSION

The biological samples and the demographic and history information collected throughout this study will be used for various analyses evaluating genomics, metabolomics and host immune responses in the context of CT infection.

Exploiting induced pluripotent stem cell-derived macrophages to unravel host factors influencing Chlamydia trachomatis pathogenesis

Chlamydia trachomatis remains a leading cause of bacterial sexually transmitted infections and preventable blindness worldwide. There are, however, limited in vitro models to study the role of host genetics in the response of macrophages to this obligate human pathogen. Here, we describe an approach using macrophages derived from human induced pluripotent stem cells (iPSdMs) to study macrophage–Chlamydia interactions in vitro. We show that iPSdMs support the full infectious life cycle of C. trachomatis in a manner that mimics the infection of human blood-derived macrophages. Transcriptomic and proteomic profiling of the macrophage response to chlamydial infection highlighted the role of the type I interferon and interleukin 10-mediated responses. Using CRISPR/Cas9 technology, we generated biallelic knockout mutations in host genes encoding IRF5 and IL-10RA in iPSCs, and confirmed their roles in limiting chlamydial infection in macrophages. This model can potentially be extended to other pathogens and tissue systems to advance our understanding of host-pathogen interactions and the role of human genetics in influencing the outcome of infections.

In vitro models to study the role of host genetics in the response to chlamydial infection are limited. Here, Yeung et al. show that macrophages derived from human induced pluripotent stem cells (which can be genetically manipulated) support chlamydial infection and can be used for this purpose.

Chlamydial Antibiotic Resistance and Treatment Failure in Veterinary and Human Medicine

The Chlamydiaceae are widespread pathogens of both humans and animals. Chlamydia trachomatis infection causes blinding trachoma and reproductive complications in humans. Chlamydia pneumoniae causes human respiratory tract infections and atypical pneumonia. Chlamydia suis infection is associated with conjunctivitis, diarrhea, and failure to gain weight in domestic swine. Chlamydial infections in humans and domesticated animals are generally controlled by antibiotic treatment—particularly macrolides (usually azithromycin) and tetracyclines (tetracycline and doxycycline). Tetracycline-containing feed has also been used to limit infections and promote growth in livestock populations, although its use has decreased because of growing concerns about antimicrobial resistance development. Because Sandoz and Rockey published an elegant review of chlamydial anti-microbial resistance in 2010, we will review the following: (i) antibiotic resistance in C. suis, (ii) recent evidence for acquired resistance in human chlamydial infections, and (iii) recent non-genetic mechanisms of antibiotic resistance that may contribute to treatment failure.

High Chlamydia Burden Promotes Tumor Necrosis Factor-Dependent Reactive Arthritis in SKG Mice

OBJECTIVE

Chlamydia trachomatis is a sexually transmitted obligate intracellular pathogen that causes inflammatory reactive arthritis, spondylitis, psoriasiform dermatitis, and conjunctivitis in some individuals after genital infection. The immunologic basis for this inflammatory response in susceptible hosts is poorly understood. As ZAP-70(W163C) -mutant BALB/c (SKG) mice are susceptible to spondylo-arthritis after systemic exposure to microbial β-glucan, we undertook the present study to compare responses to infection with Chlamydia muridarum in SKG mice and BALB/c mice.

METHODS

After genital or respiratory infection with C muridarum, conjunctivitis and arthritis were assessed clinically, and eye, skin, and joint specimens were analyzed histologically. Chlamydial major outer membrane protein antigen-specific responses were assessed in splenocytes. Treg cells were depleted from FoxP3-DTR BALB/c or SKG mice, and chlamydial DNA was quantified by polymerase chain reaction.

RESULTS

Five weeks after vaginal infection with live C muridarum, arthritis, spondylitis, and psoriasiform dermatitis developed in female SKG mice, but not in BALB/c mice. Inflammatory bowel disease did not occur in mice of either strain. The severity of inflammatory disease was correlated with C muridarum inoculum size and vaginal burden postinoculation. Treatment with combination antibiotics starting 1 day postinoculation prevented disease. Chlamydial antigen was present in macrophages and spread from the infection site to lymphoid organs and peripheral tissue. In response to chlamydial antigen, production of interferon-γ and interleukin-17 was impaired in T cells from SKG mice but tumor necrosis factor (TNF) responses were exaggerated, compared to findings in T cells from BALB/c mice. Unlike previous observations in arthritis triggered by β-glucan, no autoantibodies developed. Accelerated disease triggered by depletion of Treg cells was TNF dependent.

CONCLUSION

In the susceptible SKG strain, Chlamydia-induced reactive arthritis develops as a result of deficient intracellular pathogen control, with antigen-specific TNF production upon dissemination of antigen, and TNF-dependent inflammatory disease.

The Role of the Immune Response in Chlamydia trachomatis Infection of the Male Genital Tract: A Double-Edged Sword

Chlamydia trachomatis (CT) is the most prevalent bacterial sexually transmitted infection in the world, with more than 100 million cases reported annually. While there have been extensive studies into the adverse effects that CT infection has on the female genital tract, and on the subsequent ability of these women to conceive, studies into the consequences on male fertility have been limited and controversial. This is in part due to the asymptomatic nature of the infection, where it is estimated that 50% of men with Chlamydia fail to show any symptoms. It is accepted, however, that acute and/or persistent CT infection is the causative agent for conditions such as urethritis, epididymitis, epididymo-orchitis, and potentially prostatitis. As with most infections, the immune system plays a fundamental role in the body’s attempts to eradicate the infection. The first and most important immune response to Chlamydia infection is a local one, whereby immune cells such as leukocytes are recruited to the site of infections, and subsequently secrete pro-inflammatory cytokines and chemokines such as interferon gamma. Immune cells also work to initiate and potentiate chronic inflammation through the production of reactive oxygen species (ROS), and the release of molecules with degradative properties including defensins, elastase, collagenase, cathespins, and lysozyme. This long-term inflammation can lead to cell proliferation (a possible precursor to cancer), tissue remodeling, and scarring, as well as being linked to the onset of autoimmune responses in genetically disposed individuals. This review will focus on the ability of the immune system to recognize and clear acute and persistent chlamydial infections in the male genital tract, and on the paradoxical damage that chronic inflammation resulting from the infection can cause on the reproductive health of the individual.

Mucosal immune responses to microbiota in the development of autoimmune disease

The etiology of most systemic autoimmune diseases remains unknown. There is often a preclinical period of systemic autoimmunity prior to the onset of clinically classifiable disease; established and emerging data suggest that dysregulated immune interactions with commensal microbiota may play a role in the initial generation of autoimmunity in this preclinical period. This article reviews potential mechanisms by which alterations of healthy microbiota may induce autoimmunity as well as mucosal microbial associations with autoimmune diseases. If mucosal microbiota lead to the development of autoimmunity, these mucosal sites, microorganisms, and immunologic mechanisms can be targeted to prevent the onset of systemic autoimmune disease.

Membrane vesicle production by Chlamydia trachomatis as an adaptive response

Bacteria have evolved specific adaptive responses to cope with changing environments. These adaptations include stress response phenotypes with dynamic modifications of the bacterial cell envelope and generation of membrane vesicles (MVs). The obligate intracellular bacterium, Chlamydia trachomatis, typically has a biphasic lifestyle, but can enter into an altered growth state typified by morphologically aberrant chlamydial forms, termed persistent growth forms, when induced by stress in vitro. How C. trachomatis can adapt to a persistent growth state in host epithelial cells in vivo is not well understood, but is an important question, since it extends the host-bacterial relationship in vitro and has thus been indicated as a survival mechanism in chronic chlamydial infections. Here, we review recent findings on the mechanistic aspects of bacterial adaptation to stress with a focus on how C. trachomatis remodels its envelope, produces MVs, and the potential important consequences of MV production with respect to host-pathogen interactions. Emerging data suggest that the generation of MVs may be an important mechanism for C. trachomatis intracellular survival of stress, and thus may aid in the establishment of a chronic infection in human genital epithelial cells.

Commonly prescribed β-lactam antibiotics induce C. trachomatis persistence/stress in culture at physiologically relevant concentrations

Chlamydia trachomatis, the most common bacterial sexually transmitted disease agent worldwide, enters a viable, non-dividing and non-infectious state (historically termed persistence and more recently referred to as the chlamydial stress response) when exposed to penicillin G in culture. Notably, penicillin G-exposed chlamydiae can reenter the normal developmental cycle upon drug removal and are resistant to azithromycin-mediated killing. Because penicillin G is less frequently prescribed than other β-lactams, the clinical relevance of penicillin G-induced chlamydial persistence/stress has been questioned. The goal of this study was to determine whether more commonly used penicillins also induce C. trachomatis serovar E persistence/stress. All penicillins tested, as well as clavulanic acid, induced formation of aberrant, enlarged reticulate bodies (RB) (called aberrant bodies or AB) characteristic of persistent/stressed chlamydiae. Exposure to the penicillins and clavulanic acid also reduced chlamydial infectivity by >95%. None of the drugs tested significantly reduced chlamydial unprocessed 16S rRNA or genomic DNA accumulation, indicating that the organisms were viable, though non-infectious. Finally, recovery assays demonstrated that chlamydiae rendered essentially non-infectious by exposure to ampicillin, amoxicillin, carbenicillin, piperacillin, penicillin V, and clavulanic acid recovered infectivity after antibiotic removal. These data definitively demonstrate that several commonly used penicillins induce C. trachomatis persistence/stress at clinically relevant concentrations.

Porcine epidemic diarrhea virus (PEDV) co-infection induced chlamydial persistence/stress does not require viral replication

Chlamydiae may exist at the site of infection in an alternative replicative form, called the aberrant body (AB). ABs are produced during a viable but non-infectious developmental state termed “persistence” or “chlamydial stress.” As persistent/stressed chlamydiae: (i) may contribute to chronic inflammation observed in diseases like trachoma; and (ii) are more resistant to current anti-chlamydial drugs of choice, it is critical to better understand this developmental stage. We previously demonstrated that porcine epidemic diarrhea virus (PEDV) co-infection induced Chlamydia pecorum persistence/stress in culture. One critical characteristic of persistence/stress is that the chlamydiae remain viable and can reenter the normal developmental cycle when the stressor is removed. Thus, we hypothesized that PEDV-induced persistence would be reversible if viral replication was inhibited. Therefore, we performed time course experiments in which Vero cells were C. pecorum/PEDV infected in the presence of cycloheximide (CHX), which inhibits viral but not chlamydial protein synthesis. CHX-exposure inhibited PEDV replication, but did not inhibit induction of C. pecorum persistence at 24 h post-PEDV infection, as indicated by AB formation and reduced production of infectious EBs. Interestingly, production of infectious EBs resumed when CHX-exposed, co-infected cells were incubated 48–72 h post-PEDV co-infection. These data demonstrate that PEDV co-infection-induced chlamydial persistence/stress is reversible and suggest that this induction (i) does not require viral replication in host cells; and (ii) does not require de novo host or viral protein synthesis. These data also suggest that viral binding and/or entry may be required for this effect. Because the PEDV host cell receptor (CD13 or aminopeptidase N) stimulates cellular signaling pathways in the absence of PEDV infection, we suspect that PEDV co-infection might alter CD13 function and induce the chlamydiae to enter the persistent state.

Atypical morphological characteristics and surface antigen expression of Burkholderia pseudomallei in naturally infected human synovial tissues

Abstract Burkholderia pseudomallei is the causative agent of melioidosis, a disease that frequently runs a protracted course and is very difficult to eradicate. The mechanisms that this organism uses to escape from host defense mechanisms and antibiotics are not well understood. The aim of the study was to compare the morphological characteristics and surface antigen expression of B. pseudomallei in naturally infected human synovial tissues with the characteristics of bacteria grown in culture media. Immunoelectron microscopic study was performed in four synovial biopsies taken from four B. pseudomallei septic arthritis patients. Colonies of pathogenic B. pseudomallei collected from culture media were used as positive controls. Polyclonal antibody to whole cell B. pseudomallei was used as a primary antibody. Complete bacteria-like particles were demonstrated both extracellularly and intracellularly in all four synovial specimens. The intracytoplasmic location of B. pseudomallei and mononuclear phagosome containing microcolony-like structures were demonstrated. B. pseudomallei found in the synovial membrane samples were mostly atypical, with fewer cytoplasmic electron lucent granules. Immunogold staining of bacterial surface antigens was weaker than staining of positive controls. We demonstrated atypical forms of B. pseudomallei and evidence for suppression of its surface antigens in naturally infected human synovial tissues. This adaptation may help bacteria to survive despite host immune surveillance and treatment with antibiotics.

Chlamydia trachomatis-infected epithelial cells and fibroblasts retain the ability to express surface-presented major histocompatibility complex class I molecules

The obligate intracellular bacterial pathogen Chlamydia trachomatis is the causative agent of a variety of infectious diseases such as trachoma and sexually transmitted diseases. In infected target cells, C. trachomatis replicates within parasitophorous vacuoles and expresses the protease-like activity factor CPAF. Previous studies have suggested that CPAF degrades the host transcription factors RFX5 and NF-κB p65, which are involved in the regulation of constitutive and inducible expression of major histocompatibility complex class I (MHC I). It was speculated that Chlamydia suppresses the surface presentation of MHC I in order to evade an effective immune response. Nevertheless, a recent study suggested that RFX5 and NF-κB p65 may not serve as target substrates for CPAF-mediated degradation, raising concerns about the proposed MHC I subversion by Chlamydia. Hence, we investigated the direct influence of Chlamydia on MHC I expression and surface presentation in infected host cells. By using nine different human cells and cell lines infected with C. trachomatis (serovar D or LGV2), we demonstrate that chlamydial infection does not interfere with expression, maturation, transport, and surface presentation of MHC I, suggesting functional antigen processing in bacterium-infected cells. Our findings provide novel insights into the interaction of chlamydiae with their host cells and should be taken into consideration for the design of future therapies and vaccines.

Chlamydia and chronic arthritis

Certain bacterial infections have been demonstrated to be causative of reactive arthritis. The most common bacterial trigger of reactive arthritis is Chlamydia trachomatis. Chlamydia pneumoniae is another known cause, albeit far less frequently. Although Chlamydia-induced reactive arthritis will often spontaneously remit, approximately 30% of patients will develop a chronic course. Modern medicine has provided rather remarkable advances in our understanding of the chlamydiae, as these organisms relate to chronic arthritis and the delicate balance between host and pathogen. C. trachomatis and C. pneumoniae both have a remarkable ability to disseminate from the initial site of infection and establish persistently viable organisms in distant organ sites, namely the synovial tissue. How these persistent chlamydiae contribute to disease maintenance remains to be fully established, but recent data demonstrating that long-term combination antimicrobial treatment can not only ameliorate the symptoms but eradicate the persistent infection suggest that these chronically infecting chlamydiae are indeed a driving force behind the chronic inflammation. We are beginning to learn that this all appears possible even after an asymptomatic initial chlamydial infection. Both C. trachomatis and C. pneumoniae are a clear cause of chronic arthritis in the setting of reactive arthritis; the possibility remains that these same organisms are culpable in other forms of chronic arthritis as well.

Chlamydia muridarum enters a viable but non-infectious state in amoxicillin-treated BALB/c mice

In culture, exposure to penicillin and other stressors induce chlamydiae to enter a non-infectious but viable state termed persistence. Chlamydiae may reenter their normal developmental cycle after stressor removal. Though aberrant RB similar to those present in culture models of persistence have been observed within infected tissues, the existence of persistent chlamydiae has not been definitively demonstrated in vivo. As a result, the role of persistent organisms in pathogenesis is undefined. In order to establish an experimentally tractable model of in vivo persistence, Chlamydia muridarum vaginally-infected mice were gavaged with either water or amoxicillin (amox). Vaginal swabs were collected for chlamydial titration and RNA isolated for quantification of pre-16s rRNA. Uterine tissue was analyzed by transmission electron microscopy (TEM). Although amox-treatment reduced vaginal shedding by >99%, C. muridarum pre-16s rRNA accumulation was unchanged by treatment. These data indicate that the amox-exposed organisms were viable but not infectious. Furthermore, TEM analyses demonstrated that inclusions in amox-treated animals contained primarily large, aberrant RB, but those observed in untreated control animals were normal. Collectively, these data suggest that amoxicillin treatment induces C. muridarum to enter the persistent state in vivo. This model also represents the first experimentally tractable animal model of chlamydial persistence.

Inhibitory effects of 405 nm irradiation on Chlamydia trachomatis growth and characterization of the ensuing inflammatory response in HeLa cells

Background

Chlamydia trachomatis is an intracellular bacterium that resides in the conjunctival and reproductive tract mucosae and is responsible for an array of acute and chronic diseases. A percentage of these infections persist even after use of antibiotics, suggesting the need for alternative treatments. Previous studies have demonstrated anti-bacterial effects using different wavelengths of visible light at varying energy densities, though only against extracellular bacteria. We investigated the effects of visible light (405 and 670 nm) irradiation via light emitting diode (LEDs) on chlamydial growth in endocervical epithelial cells, HeLa, during active and penicillin-induced persistent infections. Furthermore, we analyzed the effect of this photo treatment on the ensuing secretion of IL-6 and CCL2, two pro-inflammatory cytokines that have previously been identified as immunopathologic components associated with trichiasis in vivo.

Results

C. trachomatis-infected HeLa cells were treated with 405 or 670 nm irradiation at varying energy densities (0 – 20 J/cm²). Bacterial growth was assessed by quantitative real-time PCR analyzing the 16S: GAPDH ratio, while cell-free supernatants were examined for IL-6 and monocyte chemoattractant protein-1 (CCL2) production. Our results demonstrated a significant dose-dependent inhibitory effect on chlamydial growth during both active and persistent infections following 405 nm irradiation. Diminished bacterial load corresponded to lower IL-6 concentrations, but was not related to CCL2 levels. In vitro modeling of a persistent C. trachomatis infection induced by penicillin demonstrated significantly elevated IL-6 levels compared to C. trachomatis infection alone, though 405 nm irradiation had a minimal effect on this production.

Conclusion

Together these results identify novel inhibitory effects of 405 nm violet light on the bacterial growth of intracellular bacterium C. trachomatis in vitro, which also coincides with diminished levels of the pro-inflammatory cytokine IL-6.

The role of Chlamydia and Chlamydophila infections in reactive arthritis

Chlamydia trachomatis and Chlamydophila pneumoniae are human pathogens; the former being the etiologic agent for trachoma as well as a prevalent sexually transmitted bacterium, while C. pneumoniae is a respiratory pathogen responsible for community-acquired pneumonia. Patients with reactive arthritis show evidence of present or past Chlamydial infection. Chlamydia spp., has been strongly implicated as a triggering factor for reactive arthritis. We describe the simultaneous occurrence of C. pneumoniae and C. trachomatis infections in a subject with reactive arthritis. We suggest treatment for a patient with Chlamydia-associated arthritis to define a means by which persistent organisms can be induced to return to the active developmental cycle, thereby making them more accessible to antibiotic activity.

Chlamydia-induced ReA: immune imbalances and persistent pathogens

Reactive arthritis (ReA), an inflammatory arthritic condition that is commonly associated with Chlamydia infections, represents a significant health burden, yet is poorly understood. The enigma of this disease is reflected in its problematic name and in its ill-defined pathogenesis. The existence of persistent pathogens in the arthritic joint is acknowledged, but their relevance remains elusive. Progress is being made in understanding the underlying mechanisms of ReA, whereby an imbalance between type 1 and type 2 immune responses seems to be critical in determining susceptibility to disease. Such an imbalance occurs prior to the initiation of an adaptive immune response, suggesting that innate cellular and molecular mechanisms in ReA should be prioritized as fruitful areas for investigation.

Combination antibiotics for the treatment of Chlamydia-induced reactive arthritis: is a cure in sight?

The inflammatory arthritis that develops in some patients subsequent to urogenital infection by the obligate intracellular bacterial pathogen Chlamydia trachomatis, and that induced subsequent to pulmonary infection with C. pneumoniae, both have proved difficult to treat in either their acute or chronic forms. Over the last two decades, molecular genetic and other studies of these pathogens have provided a good deal of information regarding their metabolic and genetic structures, as well as the detailed means by which they interact with their host cells. In turn, these insights have provided for the first time a window into the bases for treatment failures for the inflammatory arthritis. In this article we discuss the biological bases for those treatment failures, provide suggestions as to research directions that should allow improvement in treatment modalities, and speculate on how treatment regimens that currently show promise might be significantly improved over the near future using nanotechological means.

Permissivity of Vero cells, human pneumocytes and human endometrial cells to Waddlia chondrophila

Growing evidence suggests that the bacterium Waddlia chondrophila, a novel member of the Chlamydiales order, is an agent of miscarriage in humans and abortion in ruminants. We thus investigated the permissivity of three epithelial cell lines, primate Vero kidney cells, human A549 pneumocytes and human Ishikawa endometrial cells to this strict intracellular bacteria. Bacterial growth kinetics in these cell lines was assessed by quantitative PCR and immunofluorescence and our results demonstrated that W. chondrophila enters and efficiently multiplies in these epithelial cell lines. Additionally, confocal and electron microscopy indicated that the bacteria co-localize with host cell mitochondria. Within Vero and A549 cells, intracellular growth of W. chondrophila was associated with a significant decrease in host cell viability while no such cytophatic effect was detected in Ishikawa cells. Bacterial cell growth in this endometrial cell line stopped 48 h after infection. This stop in the replication of W. chondrophila coincided with the appearance of large aberrant bodies, a form of the bacteria also observed in Chlamydiaceae and associated with persistence. This persistent state of W. chondrophila may explain recurrent episodes of miscarriage in vivo, since the bacteria might reactivate within endometrial cells following hormonal changes that occur during pregnancy.

Interaction of herpes simplex virus type 2 (HSV-2) glycoprotein D with the host cell surface is sufficient to induce Chlamydia trachomatis persistence

When presented with certain unfavourable environmental conditions, Chlamydia trachomatis reticulate bodies (RBs) enter into a viable, yet non-cultivable state called persistence. Previously, we established an in vitro C. trachomatis and herpes simplex virus type 2 (HSV-2) co-infection model. These data indicate that (i) viral co-infection stimulates chlamydial persistence, (ii) productive HSV replication is not required for persistence induction, and (iii) HSV-induced persistence is not mediated by any currently characterized anti-chlamydial pathway or persistence inducer. In this study we demonstrated that chlamydial infectivity, though initially suppressed, recovered within 44 h of co-infection with UV-inactivated HSV-2, demonstrating that HSV-induced persistence is reversible. Co-incubation of chemically fixed, HSV-2-infected inducer cells with viable, C. trachomatis-infected responder cells both suppressed production of infectious chlamydial progeny and stimulated formation of swollen, aberrantly shaped RBs. In addition, pre-incubation of viral particles with viral glycoprotein D (gD)-specific neutralizing antibody prevented co-infection-induced persistence. Finally, exposure of C. trachomatis-infected cells to a soluble, recombinant HSV-2 gD : Fc fusion protein decreased production of infectious EBs to a degree similar to that observed in co-infected cultures. Thus, we conclude that interaction of HSV gD with the host cell surface is sufficient to trigger a novel host anti-chlamydial response that restricts chlamydial development.

Detection of Chlamydia trachomatis-DNA in synovial fluid: evaluation of the sensitivity of different DNA extraction methods and amplification systems

INTRODUCTION

Polymerase chain reaction (PCR) and ligase chain reaction (LCR) are used in research for detection of Chlamydia trachomatis (C. tr.) in synovial fluid (SF). However there is no standardized system for diagnostic use in clinical practice, therefore this study aimed at determining the molecular biology method best suited to detect C. tr. from SF.

METHODS

SF samples were spiked with C. tr. elementary bodies (EB) and human peripheral blood monocytes (PBMo) persistently infected with C. tr. in vitro to evaluate the sensitivity of different molecular biology methods and assays. Five different DNA-extraction methods were tested: 1) Alkaline lysis, 2) QIAex II Gel Extraction Kit+ CTAB, 3) Chelex-extraction, 4) QIAmp Tissue Kit and 5) QIAmp DNA Stool Kit. All DNA extracts were subjected to 5 different DNA amplification systems to detect C. tr.- DNA in the spiked SF samples: two C. tr. -omp1-- directed PCR, one C. tr.-plasmid-PCR, one C. tr. -16s RNA directed PCR, and one commercially available LCR (LCX), Abbott laboratories).

RESULTS

In SF samples spiked with C. tr.-EB and with C. tr.-PBMo, alkaline lysis, detecting 1 C. tr.-EB/ml SF, 0,1 C. tr.-PBMo/ml SF and QIAmp gel extraction kit+ CTAB detecting 0,1 C. tr. -EB/ml SF, 1 C. tr.-PBMo/ml, respectively, allowed most sensitive detection of the organism in combination with the C. tr.- omp1-(152 bp) PCR. Sensitivity decreased in all methods after storage of the DNA of C. tr.- dilution series at -20 degrees C for 4 months by at least one log phase.

CONCLUSIONS

The sensitivity to detect C. tr.- DNA from SF is highly dependent on the DNA extraction method and the detection system applied. Alkaline lysis as well as the QIAmp Gel extraction kit + CTAB in combination with C. tr.- omp1 - (152 bp) PCR evolved as the most sensitive methods to identify C. tr. in serial dilutions.

Molecular biology of infectious agents in chronic arthritis

Severe and chronic inflammatory arthritis sometimes follows urogenital infection with Chlamydia trachomatis or gastrointestinal infection with enteric bacterial pathogens. A similar clinical entity can be elicited by the respiratory pathogen Chlamydophila (Chlamydia) pneumoniae. Arthritogenesis does not universally require viable enteric bacteria in the joint. In arthritis induced by either of the chlamydial species, organisms are viable and metabolically active in the synovium. They exist in a "persistent" state of infection. Conventional antibiotic treatment of patients with Chlamydia-induced arthritis is largely ineffective. The authors outline the current understanding of the molecular genetic and biologic aspects underlying bacterially-induced joint pathogenesis, available information regarding host-pathogen interaction at that site, and several directions for future study to inform development of more effective therapies.

Heavy metal exposure reverses genetic resistance to Chlamydia-induced arthritis

INTRODUCTION

We have previously observed that Brown Norway (BN) rats display a relative resistance to experimental Chlamydia-induced arthritis. In the present study, we examine an environmental toxin, mercuric chloride (HgCl2), as a modulator of this innate resistance to arthritis.

METHODS

To assess the effect of the heavy metal exposure, one group of rats received two subcutaneous injections of HgCl2 (1 mg/kg) 48 hours apart. Seven days later, the animals received the intra-articular injection of synoviocyte-packaged Chlamydia.

RESULTS

Histopathology revealed that BN rats receiving only Chlamydia had a minimal cellular infiltration in the joint, which was predominantly mononuclear in character. In contrast, mercury-exposed rats had a marked exacerbation of the histopathological severity of the arthritis, and the infiltration was predominantly neutrophilic. Mercury exposure was also associated with marked enhancement in IgE levels and an alteration in IgG2a/IgG1 ratio, reflecting a Th2 shift. The local cytokine profile in the joint was markedly altered after mercury exposure, with a suppression of tumour necrosis factor-alpha and interferon-gamma but an enhancement of vascular endothelial growth factor. This was associated with decreased host clearance capacity reflected in enhanced bacterial load in both the spleen and the joint and was accompanied by enhanced detection of microbial antigens in the synovial tissues by immunohistological staining.

CONCLUSIONS

Genetically defined cytokine production in the joint defines the severity of reactive arthritis by dictating the local clearance of the pathogen. This interplay can be altered dramatically by heavy metal exposure, which results in suppression of protective cytokines in the microenvironment of the joint.

Chlamydia trachomatis infection: host immune responses and potential vaccines

Chlamydia trachomatis causes genital tract infections that affect men, women, and children on a global scale. This review focuses on innate and adaptive immune responses in the female reproductive tract (FRT) to genital tract infections with C. trachomatis. It covers C. trachomatis infections and highlights our current knowledge of genital tract infections, serovar distribution, infectious load, and clinical manifestations of these infections in women. The unique features of the immune system of the FRT will be discussed and will include a review of our current knowledge of innate and adaptive immunity to chlamydial infections at this mucosal site. The use of animal models to study the pathogenesis of, and immunity to, Chlamydia infection of the female genital tract will also be discussed and a review of recent immunization and challenge experiments in the murine model of chlamydial FRT infection will be presented.

Reactive arthritis which occurred one year after acute chlamydial urethritis

A 30-year-old Japanese man developed dactylitis with sausage-like fingers in addition to balanitis and stomatitis. One year prior to these symptoms, acute chlamydial urethritis had been successfully treated by levofloxacin. On admission, Chlamydia trachomatis DNA was not detected in the urine sediment by PCR method, however, he was diagnosed to have reactive arthritis based on the clinical findings of asymmetric dactylitis, circinate balanitis, stomatitis and positivity for HLA B27 antigen. He was treated with methotrexate and his arthritis improved. The past chlamydial infection may have been involved in the pathogenesis of reactive arthritis in this patient.

Effects of levofloxacin and doxycycline on interleukin-6 production of Chlamydia trachomatis-infected human synovial fibroblasts

BACKGROUND

A large amount (80,000-100,000 pg/ml) of interleukin-6 (IL-6) was detected in cultures of human synoviocytes infected with Chlamydia trachomatis. In this study, we investigated the effect of antibiotics on the IL-6 production of C. trachomatis-infected human fibroblast-like synovial cells (HFLS).

METHODS

The minimum inhibitory concentrations of levofloxacin and doxycycline against C. trachomatis were determined in either HFLS or HeLa 229 cells. The number of live Chlamydia was also examined. IL-6 in the supernatants of infected cultures was quantified by capture ELISA.

RESULTS

The production of IL-6 was suppressed to as low as 1,800 pg/ml in the infected HFLS treated with levofloxacin or doxycycline immediately or early after infection. In HFLS treated with levofloxacin and doxycycline, the IL-6 levels decreased to 37,000 and 21,000 pg/ml, respectively, 48 h after infection, and levofloxacin was thus found to be less effective than doxycycline. In addition, the number of viable C. trachomatis in the infected cultures treated with levofloxacin 24 h after infection was higher than when treated with doxycycline.

CONCLUSIONS

The early administration and proper selection of antibiotics is important for the suppression of inflammatory cytokine production. These findings indicate that antibiotic therapy will not only work in treating infections but might also be useful in treating reactive arthritis secondary to the infection.

Survival of Chlamydia muridarum within dendritic cells

Immune responses to Chlamydia trachomatis underlay both immunity and immunopathology. Immunopathology in turn has been attributed to chronic persistent infection with persistence being defined as the presence of organisms in the absence of replication. We hypothesized that dendritic cells (DCs) play a central role in Chlamydia immunity and immunopathology by favoring the long-term survival of C. muridarum. This hypothesis was examined based on (i) direct staining of Chlamydia in infected DCs to evaluate the development of inclusions, (ii) titration of infected DCs on HeLa cells to determine cultivability, and (iii) transfer of Chlamydia-infected DCs to naive mice to evaluate infectivity. The results show that Chlamydia survived within DCs and developed both typical and atypical inclusions that persisted in a subpopulation of DCs for more than 9 days after infection. Since the cultivability of Chlamydia from DCs onto HeLa was lower than that estimated by the number of inclusions in DCs, this suggests that the organisms may be in state of persistence. Intranasal transfer of long-term infected DCs or DCs purified from the lungs of infected mice caused mouse lung infection, suggesting that in addition to persistent forms, infective Chlamydia organisms also developed within chronically infected DCs. Interestingly, after in vitro infection with Chlamydia, most DCs died. However, Chlamydia appeared to survive in a subpopulation of DCs that resisted infection-induced cell death. Surviving DCs efficiently presented Chlamydia antigens to Chlamydia-specific CD4+ T cells, suggesting that the bacteria are able to both direct their own survival and still allow DC antigen-presenting function. Together, these results raise the possibility that Chlamydia-infected DCs may be central to the maintenance of T-cell memory that underlies both immunity and immunopathology.

Staining of Chlamydia trachomatis elementary bodies: A suitable method for identifying infected human monocytes by flow cytometry

Persistence of Chlamydia trachomatis (C. trachomatis) in the joint is the most frequent cause of reactive arthritis following urogenital tract infection. The resulting changes of host cell antigen- and cytokine-expression are not precisely understood. We developed and evaluated a direct cytometric approach to visualize in vitro C. trachomatis-infected monocytes. Infectious elementary bodies (EBs) of C. trachomatis serovar K were labelled by incubation with 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester (CFSE). Afterwards, human peripheral blood monocytes were cultured with the CFSE-labelled EBs and analysed by flow cytometry. Real-time polymerase chain reaction (PCR) was used to demonstrate intracellular uptake and viability of CFSE-labelled C. trachomatis by the determination of gene expression. Labelling EBs with CFSE may become a valuable tool for studying the interaction between C. trachomatis and the host cell.

Reactive arthritis

Reactive arthritis (ReA) has been recognized as a clinical disease entity for nearly 100 years. The prevalence is estimated to be 30-40/100,000 adults. The HLA-B27-associated form is part of the spondyloarthritis concept. According to the current hypothesis the arthritis follows a primary extra-articular infection and is characterized by the presence of bacterial antigen and/or of viable but non-culturable bacteria persisting within the joint. Pathogenesis involves the modification of host cells by pathogen-associated molecular patterns (PAMPs, e.g. lipopolysaccharide), bacterial effector proteins, the adaptive immune system, and the genetic background. Up to 30% of patients develop chronic symptoms, and therapeutic options for these patients are still limited. Data for recommendations to apply conventional disease-modifying anti-rheumatic drugs (DMARDs) are rare; however, sulfasalazine seems to be effective, and first reports on agents that block tumour necrosis factor (TNF) are promising. Combination therapy of several antibiotics might open the window to curing the disease; however, controlled clinical studies are needed.

Early cytokine profiles in the joint define pathogen clearance and severity of arthritis inChlamydia-induced arthritis in rats

OBJECTIVE

Although Chlamydia trachomatis-induced arthritis is among the most common rheumatic diseases having an identified infectious trigger, the pathogenesis of this arthritis is not well defined. We sought to investigate the host-microbe interactions that contribute to the severity of arthritis initiated by chlamydial infection.

METHODS

We established an experimental rat model of C. trachomatis-induced arthritis that recapitulates many pathologic features of the clinical disease. The severity of the arthritis was defined using an established histopathologic scoring system. Host clearance of the pathogen and local cytokine production were examined by enzyme-linked immunosorbent assays.

RESULTS

Lewis rats were susceptible to C. trachomatis-induced arthritis, whereas BN rats were relatively resistant to this disease. Significant differences in the histopathologic severity of arthritis were originally observed on day 21, and this prompted an examination of the acute phase of the arthritis. As early as day 5 after the onset of the arthritis, pathologic changes in Lewis rats were more severe than those in BN rats. An evaluation of the role of complement using cobra venom factor treatment excluded complement as being the key to differential sensitivity, because decomplementation did not eliminate the differences in arthritis severity between Lewis and BN rats. Host clearance, in contrast, was significantly different between the rat strains, with BN rats showing more prompt and effective clearance of the pathogen from both synovial tissues and spleen compared with Lewis rats. Local cytokine profiles demonstrated that host resistance was characterized by enhanced synovial expression of tumor necrosis factor alpha, interferon-gamma (IFNgamma), and interleukin-4.

CONCLUSION

These studies demonstrated that cytokines thought to be proinflammatory in nature can play an important role in host defense in infection-triggered arthritis and serve to highlight the dynamic cytokine relationships that constitute effective host-pathogen interactions.

Frequency of spontaneous mutations that confer antibiotic resistance in Chlamydia spp

Mutations in rRNA genes (rrn) that confer resistance to ribosomal inhibitors are typically recessive or weakly codominant and have been mostly reported for clinical strains of pathogens possessing only one or two rrn operons, such as Helicobacter pylori and Mycobacterium spp. An analysis of the genome sequences of several members of the Chlamydiaceae revealed that these obligate intracellular bacteria harbor only one or two sets of rRNA genes. To study the contribution of rRNA mutations to the emergence of drug resistance in the Chlamydiaceae, we used the sensitivities of Chlamydia trachomatis L2 (two rrn operons) and Chlamydophila psittaci 6BC (one rrn operon) to the aminoglycoside spectinomycin as a model. Confluent cell monolayers were infected in a plaque assay with about 10(8) wild-type infectious particles and then treated with the antibiotic. After a 2-week incubation time, plaques formed by spontaneous spectinomycin-resistant (Spc(r)) mutants appeared with a frequency of 5 x 10(-5) for C. psittaci 6BC. No Spc(r) mutants were isolated for C. trachomatis L2, although the frequencies of rifampin resistance were in the same range for both strains (i.e., 10(-7)). The risk of emergence of Chlamydia strains resistant to tetracyclines and macrolides, the ribosomal drugs currently used to treat chlamydial infections, is discussed.

Production of prostaglandin E2 in monocytes stimulated in vitro by Chlamydia trachomatis, Chlamydophila pneumoniae, and Mycoplasma fermentans

Chlamydia trachomatis (CT) as well as Chlamydophila pneumoniae (CP) cause chronic inflammatory diseases in humans. Persistently infected monocytes are involved in the pathogenesis by inducing mediators of inflammation. An in vitro system of chlamydial persistence in human peripheral blood monocytes (HPBM) was used to investigate prostaglandin E(2) (PGE(2)) production and the expression of the key enzyme for prostaglandin production, cyclooxygenase-2 (COX-2). PGE(2) production was determined by PGE(2)-ELISA of HPBM-culture supernatants. Cox-2 mRNA expression was measured by real-time RT-PCR of total RNA isolated from HPBM. Both, CT and CP, stimulated PGE(2) production of HPBM in vitro. Equivalent numbers of CT per host cell induced a higher PGE(2)-response compared to CP. The amount of synthesized PGE(2) depended on the chlamydial multiplicity of infection (MOI). Even at an MOI of 10 the amount of CT- and CP-induced prostaglandin, respectively, was lower than the amount of prostaglandin induced by E. coli lipopolysaccharide (LPS) at a concentration of 10microg/ml. In contrast to stimulation with LPS, Chlamydia-induced PGE(2) production as well as cox-2 mRNA decreased after day 1 post infection (p.i.). These data indicate that Chlamydia stimulate PGE(2) production in human monocytes. Since Chlamydia are often contaminated by mycoplasma, the influence of mycoplasma on the prostaglandin production was investigated additionally. Mycoplasma fermentans (MF) also stimulated PGE(2) production. The co-infection of mycoplasma and Chlamydia resulted in an additive effect in the production of PGE(2). Thus it is important to use host cells and Chlamydia free of mycoplasma contamination for the analysis of Chlamydia-induced prostaglandin production.

Chlamydial infection preceding the development of rheumatoid arthritis: a brief report

Chlamydia trachomatis-triggered reactive arthritis is a well-documented entity that has been extensively described. We do not have a clear understanding about the inflammatory oligoarthritis associated with the presence of this organism. It is rarely cultured from the synovial fluid, but is usually detectable by molecular biological techniques. Typically, Chlamydia trachomatis causes a sterile but inflammatory oligoarthritis. We report an unusual case of inflammatory monoarthritis in a young woman in whom Chlamydia was isolated from the synovial fluid. This is the first case of documented isolation of Chlamydia from synovial fluid, which subsequently was diagnosed as rheumatoid arthritis.

HLA-B27-associated reactive arthritis: pathogenetic and clinical considerations

Current evidence supports the concept that reactive arthritis (ReA) is an immune-mediated synovitis resulting from slow bacterial infections and showing intra-articular persistence of viable, non-culturable bacteria and/or immunogenetic bacterial antigens synthesized by metabolically active bacteria residing in the joint and/or elsewhere in the body. The mechanisms that lead to the development of ReA are complex and basically involve an interaction between an arthritogenic agent and a predisposed host. The way in which a host accommodates to invasive facultative intracellular bacteria is the key to the development of ReA. The details of the molecular pathways that explain the articular and extra-articular manifestations of the disease are still under investigation. Several studies have been done to gain a better understanding of the pathogenesis of ReA; these constitute the basis for a more rational therapeutic approach to this disease.

The occurrence of antibodies against chlamydia species in patients with monoarthritis and chronic closed lock of the temporomandibular joint

PURPOSE

The study goal was to investigate the occurrence of serum antibodies to Chlamydia trachomatis, Chlamydia pneumoniae, and Chlamydia psittaci in patients with temporomandibular joint (TMJ) monoarthritis or chronic closed lock and in control subjects.

PATIENTS AND METHODS

An indirect microimmunofluorescence test for detecting antibodies against C trachomatis was used. Twenty-three patients (12 with monoarthritis and 11 with chronic closed lock) and 42 control subjects were evaluated.

RESULTS

Six patients with monoarthritis, 5 patients with chronic closed lock of the TMJ, and 6 control individuals were considered to have had a past C trachomatis infection based on their immunoglobulin G titers. Corresponding groups for C pneumoniae investigation included 3 patients with monoarthritis, 4 patients with chronic closed lock, and 17 control subjects, and for C psittaci, 1 patient with monoarthritis, 2 patients with chronic closed lock, and 1 control subject. Statistically significant differences between patients and control subjects were found for C trachomatis only; monoarthritis versus control (P =.016), chronic closed lock versus control (P =.038), and all patients versus control (P =.007). Patients with monoarthritis did not differ from patients with chronic closed lock with regard to antibodies against C trachomatis.

CONCLUSION

The occurrence of serum antibodies to C trachomatis was significantly higher in patients than in control subjects, but this occurrence did not correlate with severity of observed tissue changes. Nevertheless, an association may exist between the presence of C trachomatis and TMJ disease.

Chlamydia trachomatis-infected macrophages induce apoptosis of activated T cells by secretion of tumor necrosis factor-alpha in vitro

Chlamydia trachomatis-infected macrophages induce T cell apoptosis. This ability might promote intracellular survival of Chlamydia and perpetuate chronic chlamydial infection. The purpose of this study was to examine the molecular mechanisms by which C. trachomatis-infected macrophages induce T cell apoptosis. Monocytes and T cells were isolated from the peripheral blood of healthy donors. Macrophages were infected with C. trachomatis, and autologous T cells were stimulated by mitogen. After 6 days, both populations were cultured together using a two-chamber transwell membrane system to differentiate between mechanisms involving either cell-to-cell contact or secretion of apoptotic factors. Apoptotic T cells were identified by propidium iodide through-flow cytometry, and tumor necrosis factor-alpha (TNF-alpha) concentrations were measured by enzyme-linked immunosorbent assay. Antagonists of TNF-alpha, the Fas (CD95) molecule, TNF-related apoptosis-inducing ligand (TRAIL), and catalase were added to differentiate between the pathways of apoptosis. C. trachomatis-infected macrophages significantly induced T cell apoptosis by cell-to-cell contact (mean +/- standard deviation, 30+/-4%; P<0.001) and by humoral mechanisms (mean +/- standard deviation, 22+/-3%, P<0.001). Humoral apoptosis was mediated by secretion of TNF-alpha from infected macrophages. Inhibition of secretory TNF-alpha by the monoclonal anti-TNF-alpha antibody adalimumab (D2E7) blocked T cell death in vitro. In contrast, T cell apoptosis mediated by cell-to-cell contact was not inhibited by the different anti-apoptotic reagents. In summary, TNF-alpha derived from infected macrophages is an important apoptosis factor for T cell apoptosis induced by C. trachomatis-infected cells.

[Diagnostic significance of synovial biopsy in patients with Reiter's syndrome]

INTRODUCTION

Arthritis in Reiter's syndrome (RS) is a reactive synovitis associated with a localized infection of the urogenital or gastrointestinal tract with a genetic predisposition. The pathogenetic mechanisms for synovitis in RS are still unknown. Our aim was to examine some of the pathogenetic mechanisms in Reiter's syndrome looking for morphologic changes, immunoprotein deposits and microorganism antigens in synovial biopsies and to determine whether synovial biopsy is useful in diagnosis of RS.

MATERIAL AND METHODS

Thirty patients with urogenital form of RS were examined within a four-year period. Table 1 illustrates laboratory findings in our patients. We performed synovial biopsies looking for histopathological changes, deposits of immunoproteins and microorganism antigens. Analysis of synovial biopsy specimens was performed using light and immunofluorescence microscopy and fluorescein-labelled monoclonal antibodies to Chlamydia trachomatis.

RESULTS

Histopathological examination of synovial membrane revealed marked proliferation of the synovial lining cells (SLC) with less or more abundant papillary projections, hypertrophic and edematous tissue with marked vascularisation in 28 (93.3%) cases. Fibrinoid necrosis foci were seen on the surface of synovial tissue. Chronic inflammatory cells (CIC) were diffusely distributed. Edema of the vessel walls, swollen endothelial cells, fibrinoid necrosis in vessel walls as well as multilaminated basement membranes were observed. All histopathologic changes are presented in Table 2. Immunofluorescent techniques in 12 out of 30 (40%) synovial membranes showed immunoglobulin deposits: IgG and IgA deposits were found in vessel walls in 7 cases each and IgM in 10 biopsy specimens. C3 was present perivascularly or within the vessel wall in 4 (13.3%) cases. Sections treated using fluorescein-conjugated antibody revealed Chlamydia in the synovial tissue in 2 patients.

CONCLUSION

Biopsy specimens with previously described changes in patients with suspected Reiter's syndrome can be useful to confirm the diagnosis. According to our experience, multiple biopsies of abnormal synovia are recommended in these patients.

Inhibition of chlamydial infectious activity due to P2X7R-dependent phospholipase D activation

Chlamydia trachomatis survives within host cells by inhibiting fusion between Chlamydia vacuoles and lysosomes. We show here that treatment of infected macrophages with ATP leads to killing of chlamydiae through ligation of the purinergic receptor, P2X(7)R. Chlamydial killing required phospholipase D (PLD) activation, as PLD inhibition led to rescue of chlamydiae in ATP-treated macrophages. However, there was no PLD activation nor chlamydial killing in ATP-treated P2X(7)R-deficient macrophages. P2X(7)R ligation exerts its effects by promoting fusion between Chlamydia vacuoles and lysosomes. P2X(7)R stimulation also resulted in macrophage death, but fusion with lysosomes preceded macrophage death and PLD inhibition did not prevent macrophage death. These results suggest that P2X(7)R ligation leads to PLD activation, which is directly responsible for inhibition of infection.

How does Chlamydia cause arthritis?

Because the bacterial cause of CIA has been identified and proven to persist at the site of inflammation, the understanding of how Chlamydia cause arthritis has made much progress. The site of entry and the route of dissemination have been identified, the molecular state of persistence is increasingly described, some mechanisms of how Chlamydia can persist despite an actively reacting immune system have been identified, and data regarding how persistent Chlamydia induce inflammation have been obtained. What needs to be achieved in the future--in addition to better understanding the molecular basis of persistence--is to reveal how persisting bacteria can be eliminated. If this information is insufficient for a cure of the disease, it must be determined how the inflammation can be treated more specifically and effectively to cure CIA early and prevent the development of chronic forms that develop into spondyloarthritis.

Infection of human fibroblast-like synovial cells with Chlamydia trachomatis results in persistent infection and interleukin-6 production

Recent studies have shown that the urogenital pathogen Chlamydia trachomatis to be a major bacterium triggering reactive arthritis (ReA), and is able to induce interleukin-6 (IL-6) production in human fibroblast-like synovial cells (FSC) in vitro. In the present study, we examined the correlation between IL-6 production and multiplication of chlamydia in FSC. All FSC from five patients secreted highly increased quantities of IL-6 in a dose-dependent and time-dependent fashion. Heat and UV inactivated chlamydia failed to enhance production of IL-6. When azithromycin was added to infected cultures of FSC at 0 or 48 h after infection, the level of IL-6 production was very low. Transmission electron microscopy of such infected cultures revealed many abnormal forms of chlamydia within the inclusions in FSC. From one step-growth curve experiments, it was suggested that C. trachomatis hardly multiplied in FSC. In contrast, in C. trachomatis infected HeLa 229 cells, chlamydia multiplied as usual, but little IL-6 production were found. These observations indicated that live chlamydia and the persistence of chlamydia may be essential for stimulating the synthesis of IL-6 in FSC.