Synoviocyte-packaged Chlamydia trachomatis induces a chronic aseptic arthritis

Chlamydia pecorum-Induced Arthritis in Experimentally and Naturally Infected Sheep

Chlamydia pecorum is an obligate intracellular pathogen with a wide host range including livestock such as sheep, cattle, goats, and pigs as well as wildlife species such as koalas. Chlamydial polyarthritis is an economically important disease resulting in swollen joints, lameness, stiffness, and weight loss in young sheep. In the present study, tissues from sheep experimentally or naturally infected with Chlamydia pecorum were assessed by histopathology and immunohistochemistry. Carpal, hock, and stifle joints as well as spleen, liver, kidney, lymph nodes, lung, and brain of 35 sheep from different inoculation groups were available. Two different C. pecorum strains (IPA and E58), different routes of administration (intraarticular or intravenous), UVA-irradiated IPA strain, and corresponding noninfected control groups were investigated. Similar investigations on tissues from 5 naturally infected sheep were performed. The most obvious inflammatory lesions were observed in synovial tissues and, notably, in the renal pelvis from the experimentally infected group and naturally infected animals. This resulted in chronic or chronic-active arthritis and pyelitis. Intralesional chlamydial inclusions could be demonstrated by immunohistochemistry in both tissues. Immunohistochemical evaluation of the presence and distribution of macrophages, T and B cells in synovial tissues revealed macrophages as the most prevalent inflammatory cell population. Previous observations indicated that C. pecorum isolates can infect circulating monocytes. Together with the finding of the histological lesions in synovial tissues and internal organs alongside the presence of C. pecorum DNA, these observations suggest chlamydial arthritis in lambs is the result of hematogeneous spread of C. pecorum.

The Importance of HLA-B27 in the Evolution of Reactive Arthritis

Reactive arthritis is an inflammatory joint disease which develops after 1-4 weeks following an enteral, genital or ORL infection, with a higher frequency in HLA-B27 positive patients.

AIMS

The objective of this paper is to study the importance of HLA-B27 antigen in the development of reactive arthritis.

PATIENTS AND METHODS

The transversal, observational study was conducted in the Rheumatology Clinic of the University of Medicine and Pharmacy of Craiova during the period 2012-2015 and included 112 patients. They were divided into three groups, as follows: group I (52 reactive arthritis cases), group II (30 other spondyloarthritis cases), group III (40 osteoarthritis cases). ELISA and PCR techniques were used to determine the antigen.

RESULTS

Those whom had this genetic marker present, the number of enthesitis almost doubled highlighting a possible correlation between the antigen and these imaging changes. We can confirm the same thing for the erosions as well. Unlike enthesitis, erosions occurred also in group III (37.5%), but if we refer to the first two groups, we will observe a significant relationship regarding HLA-B27. More specifically, in HLA-B27 positive patients (68.97%), erosions were found to be twice as numerous than in HLA-B27 negative patients (31.03%). In group I we identified stage 2 sacroiliitis in 68% of HLA-B27 positive patients and 32% in HLA-B27 negative, which shows another link to this antigen with both joint destruction and a possible unfavorable evolution of reactive arthritis.

CONCLUSIONS

This antigen specific to the seronegative group of spondyloarthritis determines the acceleration of articular destruction, translated by erosion, and the evolution of sacroiliitis to a more advanced stage.

Recent advances and future directions in understanding and treating Chlamydia-induced reactive arthritis

INTRODUCTION

Reactive arthritis (ReA) is an inflammatory disease that can follow gastrointestinal or genitourinary infections. The primary etiologic agent for post-venereal ReA is the bacterium Chlamydia trachomatis; its relative, C pneumoniae, has also been implicated in disease induction although to a lesser degree. Studies have indicated that the arthritis is elicited by chlamydiae infecting synovial tissue in an unusual biologic state designated persistence. We review clinical aspects, host-pathogen interactions, and treatments for the disease. Areas covered: We briefly discuss both the historic and,more extensively, the current medical literature describing ReA, and we provide a discussion of the biology of the chlamydiae as it relates to elicitation of the disease. A summary of clinical aspects of Chlamydia-induced ReA is included to give context for approaches to treatment of the arthritis. Expert commentary: Basic research into the biology and host-pathogen interactions characteristic of C trachomatis has provided a wealth of information that underlies our current understanding of the pathogenic processes occurring in the ReA synovium. Importantly, a promising approach to cure of the disease is at hand. However, both basic and clinical research into Chlamydia-induced ReA has lagged over the last 5 years, including required studies relating to cure of the disease.

Rho GTPases as pathogen targets: Focus on curable sexually transmitted infections

Pathogens have evolved highly specialized mechanisms to infect hosts. Several microorganisms modulate the eukaryotic cell surface to facilitate their engulfment. Once internalized, they hijack the molecular machinery of the infected cell for their own benefit. At different stages of phagocytosis, particularly during invasion, certain pathogens manipulate pathways governed by small GTPases. In this review, we focus on the role of Rho proteins on curable, sexually transmitted infections caused by Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis and Treponema pallidum. Despite the high, worldwide frequencies of these sexually-transmitted diseases, very little is known about the strategies developed by these microorganisms to usurp key eukaryotic proteins that control intracellular signaling and actin dynamics. Improved knowledge of these molecular mechanisms will contribute to the elucidation of how these clinically important pathogens manipulate intracellular processes and parasitize their hosts.

Virus-related liver cirrhosis: molecular basis and therapeutic options

Chronic infections with hepatitis B virus (HBV) and/or hepatitis C virus (HCV) are the major causes of cirrhosis globally. It takes 10-20 years to progress from viral hepatitis to cirrhosis. Intermediately active hepatic inflammation caused by the infections contributes to the inflammation-necrosis-regeneration process, ultimately cirrhosis. CD8(+) T cells and NK cells cause liver damage via targeting the infected hepatocytes directly and releasing pro-inflammatory cytokine/chemokines. Hepatic stellate cells play an active role in fibrogenesis via secreting fibrosis-related factors. Under the inflammatory microenvironment, the viruses experience mutation-selection-adaptation to evade immune clearance. However, immune selection of some HBV mutations in the evolution towards cirrhosis seems different from that towards hepatocellular carcinoma. As viral replication is an important driving force of cirrhosis pathogenesis, antiviral treatment with nucleos(t)ide analogs is generally effective in halting the progression of cirrhosis, improving liver function and reducing the morbidity of decompensated cirrhosis caused by chronic HBV infection. Interferon-α plus ribavirin and/or the direct acting antivirals such as Vaniprevir are effective for compensated cirrhosis caused by chronic HCV infection. The standard of care for the treatment of HCV-related cirrhosis with interferon-α plus ribavirin should consider the genotypes of IL-28B. Understanding the mechanism of fibrogenesis and hepatocyte regeneration will facilitate the development of novel therapies for decompensated cirrhosis.

The role of intracellular organisms in the pathogenesis of inflammatory arthritis

Inflammatory arthritis is a condition which is characterised by recurrent episodes of joint pain and swelling. It encompasses a spectrum of disorders ranging from rheumatoid arthritis to ankylosing spondylitis. In these conditions, for reasons that are poorly understood, the immune system raises an inflammatory response within the joint space. In some cases, autoantigens have been identified (e.g., anticitrullinated peptides in rheumatoid arthritis), but the absence of these, in the seronegative arthritides, for example, raises question as to the underlying pathogenesis. Interest has, therefore, turned to host-pathogen interactions and whether aberrant immune responses to these could explain the development of arthritis. This has been most widely studied in reactive arthritis (ReA), where an infectious episode precedes the development of the joint symptoms. In this review, we present the evidence for the role of host-bacterial interactions in the pathogenesis of joint inflammation with particular emphasis on ReA. We discuss a range of possible mechanisms including molecular mimicry, persistent low grade infections, and abnormal host responses to common bacterial causes of reactive arthritis as well as discussing some of the clinical challenges that we face in making the diagnosis and in treatment of persistent symptoms.

Nafamostat mesylate, a serine protease inhibitor, demonstrates novel antimicrobial properties and effectiveness in Chlamydia-induced arthritis

Introduction

Effective treatment of reactive arthritis would ideally achieve both control of inflammation and eradication of persisting arthritogenic pathogens. We use a model of experimental Chlamydia trachomatis-induced arthritis (CtIA) to evaluate the effectiveness of nafamostat mesilate (NM), a serine protease inhibitor with complement-modifying effects and anticoagulant properties. To date clinical use of NM has largely been in Asia and has been primarily confined to inflammatory states such as pancreatitis.

Methods

In vitro studies examined inhibition of Chlamydia proliferation using fibroblast cell lines as targets and phase contrast microscopy. In vivo studies used an established protocol, experimental CtIA, induced in Lewis rats by injection of synoviocyte-packaged C. trachomatis. NM was dissolved in water and administered by daily intraperitoneal injection at a dose of 10 mg/kg beginning the day prior to the administration of Chlamydia. Readouts in vivo included (i) joint swelling, (ii) histopathology scoring of severity of arthritis, (iii) host clearance of the pathogen (by ELISA, the IDEIA PCE Chlamydia).

Results

NM exerted a dose-dependent inhibition of chlamydial proliferation in vitro. Without NM, the mean number of inclusion bodies (IB) per well was 17,886 (± 1415). At 5 μg/mL NM, there were 8,490 (± 756) IB, at 25 μg/mL NM there were 35 IB and at 50 μg/mL NM no IB was observed. Chlamydial antigens in each well along the concentration gradient were assayed by ELISA, demonstrating that at 25 μg/mL NM inhibition of Chlamydia was almost complete. In the experimental arthritis model, joint swelling was significantly reduced with NM treatment: average joint width for the NM-treated animals was 8.55 mm (s.d. ± 0.6578, n = 10) versus 11.18 mm (s.d. ± 0.5672, n = 10) in controls (P < 0.001). Histopathology scoring indicated that NM resulted in a marked attenuation of the inflammatory infiltration and joint damage: mean pathology score in NM-treated animals was 10.9 (± 2.45, n = 11) versus 15.9 (± 1.45, n = 10) in controls (P < 0.0001). With respect to persistence of Chlamydia within the synovial tissues, NM treatment was accompanied by a reduction in the microbial load in the joint: mean optical density (O.D.) for ELISA with NM treatment was 0.05 (± 0.02, n = 4) versus 0.18 (± 0.05, n = 4) in controls (P < 0.001).

Conclusions

NM is a protease inhibitor not previously recognized to possess antimicrobial properties. The present study demonstrates for the first time that NM exerts significant impact on C. trachomatis-induced arthritis and suggests that such approaches may prove clinically useful in chronic reactive arthritis.

Is the role of Chlamydia trachomatis underestimated in patients with suspected reactive arthritis?

Reactive arthritis is usually caused by bacteria of either the enteric or genital tracts. In the genital tract, Chlamydia trachomatis is perhaps the only aetiological agent. In Iran, newer evidence suggests that as C. trachomatis is more commonly found in the general population than was previously believed, its role in reactive arthritis may well be currently overlooked. In this review, as well as emphasizing the potential role of C. trachomatis in reactive arthritis in patients from developing countries, we also make recommendations for further clinical studies to determine its prevalence. Moreover, we also stress the need for standardization of new testing methodologies for C. trachomatis, including the use of new commercial systems in an attempt to determine a truer picture of chlamydial infection in reactive arthritis.

Bone marrow-derived human hematopoietic stem cells engraft NOD/SCID mice and traffic appropriately to an inflammatory stimulus in the joint

OBJECTIVE

Studies of human inflammatory arthritis would be significantly aided by the development of better animal models. Our hypothesis is that it is possible to develop humanized arthritis models through novel techniques of hematopoietic stem and progenitor cell (HSPC) delivery.

METHODS

Bone marrow was obtained from patients with osteoarthritis who were undergoing total hip replacement. HSPC were enriched by negative selection and injected into the femur of irradiated anti-CD122 treated nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Human cell engraftment was analyzed by flow cytometry. Arthritis was induced by an intraarticular injection of Chlamydia trachomatis and injected knee joints were examined 5 days later by histology and immunohistochemistry.

RESULTS

Human bone marrow HSPC successfully engrafted NOD/SCID mice, with some mice showing up to 90% engrafted human cells. Human B lymphoid and myeloid cells were detected in the bone marrow and spleen 6 weeks following transfer of HSPC, and engrafted recipient mice remained healthy up to 12 weeks postinjection. Chlamydia-injected mice that had been repopulated with HSPC had synovial inflammation, consisting of human neutrophils and macrophages.

CONCLUSION

Bone marrow-derived human HSPC engraft NOD/SCID mice and traffic appropriately to an inflammatory stimulus in the joint, thus offering the potential for direct studies on the immunopathogenesis and treatment of human arthritis.

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.

Reactive arthritis

ReA consists of sterile axial or peripheral articular inflammation,enthesitis, and extra-articular manifestations. Most patients are HLA-B27 positive, although determining the B27 status of an individual patient is irrelevant. Exposure to specific bacterial antigens is usually the inciting factor. Diagnosis usually can be made by clinical examination and history. The current standard therapy is NSAIDs and physiotherapy, but molecular biologic treatment may ultimately become the mainstay in recalcitrant and severe ReA.

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.

Innate immunity and arthritis: neutrophil Rac and toll-like receptor 4 expression define outcomes in infection-triggered arthritis

OBJECTIVE

The role of innate immunity in Chlamydia-induced arthritis has not been defined. The purpose of this study was to examine the role of neutrophils in experimental arthritis in mice with targeted elimination of the small GTPases Rac1 and Rac2, as well as the role of Toll-like receptors (TLRs) in this model.

METHODS

Arthritis was induced by intraarticular inoculation of synoviocyte-packaged Chlamydia trachomatis. The degree of arthritis was assessed according to joint swelling and pathology scores. The persistence of Chlamydia in joints was assessed by immunoassay. The expression of TLR-2 and TLR-4 in neutrophils was detected by semiquantitative reverse transcription-polymerase chain reaction.

RESULTS

In the acute phase, wild-type mice developed more severe arthritis than did Rac-deficient mice, with abundant infiltration of neutrophils into the joint. In the chronic phase, the Rac-deficient mice developed more severe arthritis and demonstrated defective clearance of the pathogen from the joint. In vitro stimulation of neutrophils with Chlamydia up-regulated the expression of TLR-4, but not TLR-2, in wild-type mice. However, neutrophils from Rac-deficient mice did not show this up-regulation of TLR-4. Sustained TLR-4 expression in neutrophils was found to be dependent on the expression of Rac. Mice genetically deficient in TLR-4 demonstrated more severe arthritis than did the controls. Thus, Rac expression plays a profound role in infection-triggered arthritis and demonstrates a bimodal influence on the disease process, exacerbating acute joint inflammation but controlling chronic arthritis. Rac deficiency was associated with diminished TLR-4 expression, impaired host clearance of the pathogen, and more severe chronic arthritis.

CONCLUSION

In infection-triggered arthritis, innate immunity plays a critical role. Effective host clearance of an arthritogenic pathogen depends on intact expression of Rac and appropriate expression of TLR-4 by neutrophils.

Synovial fibroblasts infected with Salmonella enterica serovar Typhimurium mediate osteoclast differentiation and activation

The mechanisms whereby arthritogenic organisms may induce cartilage and bone erosions in infection-triggered arthritis remain unknown. In this study, we asked whether an arthritogenic organism could contribute to osteoclast differentiation and activation through regulation of the receptor activator of NF-kappaB ligand (RANKL) in synovial fibroblasts. Rat synovial fibroblasts were infected in vitro with Salmonella enterica serovar Typhimurium and monitored over time. The expression of RANKL in resting and infected synovial fibroblasts was quantified by reverse transcription-PCR and Western blotting. Osteoclast progenitors, isolated from femurs of 8-week-old rats and cultured in the presence of macrophage colony-stimulating factor, were cocultured with either infected or noninfected synovial fibroblasts for 2 to 4 days. Differentiation and maturation of osteoclasts were determined by morphology and tartrate-resistant acid phosphatase (TRAP) staining and by a bone resorption bioassay. RANKL expression was undetectable in resting synovial fibroblasts but was dose-dependently upregulated in cells after Salmonella infection. Osteoprotegerin was constitutively expressed by synovial fibroblasts and was not upregulated by infection. Further, we observed the formation of multinucleated TRAP-positive cells and formation of bone resorption pits in cocultures of bone marrow-derived osteoclast precursors with synovial fibroblasts infected with Salmonella but not with heat-killed Salmonella or noninfected cells. Arthritogenic bacteria may alter bone structure via synovial fibroblast intermediaries, since infected synovial fibroblasts (i) upregulate RANKL expression and (ii) enhance osteoclast precursor maturation into multinucleated, TRAP-positive, bone-resorbing, osteoclast-like cells. These data provide a link between infection and osteoclastogenesis. A better understanding of infection-mediated osteoclast differentiation and activation may provide new therapeutic strategies for inflammatory joint disease.

Chlamydial conjunctivitis (in adults), uveitis, and reactive arthritis, including SARA. Sexually acquired reactive arthritis

This chapter deals with Chlamydia -induced ocular and rheumatic diseases of the adult. All of these may follow a primary urogenital infection with Chlamydia trachomatis in genetically predisposed patients. Besides the infection with Chlamydia trachomatis, infections with Chlamydia pneumoniae and Chlamydia psittaci are also discussed as possible causative agents. Chlamydial conjunctivitis is frequently a secondary infection, and the organism is transferred from the urogenital tract to the eye by autoinoculation. Uveitis and reactive arthritis are believed to be triggered - among other infections - by a preceding urogenital infection. Both of them are closely associated with HLA-B27 positivity. The simultaneous occurrence of uveitis and reactive arthritis is termed Reiter's syndrome. We report on clinical characteristics, diagnosis and the role of Chlamydia in the pathogenesis of chlamydial conjunctivitis, uveitis and reactive arthritis as well as on the currently recommended treatment regimens.

Role of interferon-stimulated gene factor 3gamma and beta interferon in HLA class I enhancement in synovial fibroblasts upon infection with Chlamydia trachomatis

Chlamydia trachomatis infection can cause reactive arthritis that is associated with the persistence of chlamydial organisms in the joint. Fibroblasts of the synovial membrane represent host cells for Chlamydia during articular infection. In this study we investigated the expression of HLA class I molecules in synovial fibroblasts following infection with C. trachomatis D. The expression of HLA class I heavy chain (HLA-I) was up-regulated in infected cultures as shown by reverse transcription-PCR and immunoblotting. The increase in cell surface expression of HLA-I and beta(2) microglobulin on infected fibroblasts was demonstrated by flow cytometric analysis. Suppression of enhanced production of interferon-stimulated gene factor 3gamma (ISGF3gamma) in infected cell cultures by antisense oligonucleotide treatment reduced the level of HLA-I. Blocking antibodies to beta interferon (IFN-beta) inhibited the Chlamydia-induced enhancement of both ISGF3gamma and HLA-I. These findings show that the up-regulation of HLA-I in synovial fibroblasts infected with C. trachomatis is caused by the induction of IFN-beta, which in turn stimulates the synthesis of ISGF3gamma, a transcription factor participating in the regulation of the HLA-I gene. The IFN-beta-mediated expression of HLA-I on Chlamydia-infected cells may be a regulatory factor in the immune response in chlamydial infections.

Breakdown of CTL Tolerance to Self HLA-B*2705 Induced by Exposure toChlamydiatrachomatis

There is a strong association between seronegative arthritis and HLA B27, but it is still unresolved whether the contribution of B27 to disease pathogenesis is solely as a restriction element for an arthritogenic peptide, or whether B27 itself serves as an autoantigen. This study uses transgenic rats to address the question as to whether exposure to an arthritogenic pathogen can alter tolerance to B27. Unlike their nontransgenic counterparts, B27-transgenic rats are tolerant of B27 immunization using either B27(+) splenocytes or plasmid DNA and do not develop anti-B27 CTL. However, if splenocytes from such immunized animals are exposed to Chlamydia in vitro, CTL are generated that lyse B27(+) targets. No killing was seen with targets transfected with control B7, B14, B40, or B44. This phenomenon was not observed with immunization by nontransgenic splenocytes, or HLA-A2 DNA alone. Using targets expressing mutated B27, we show that the epitope for autoreactive CTL recognition of B27 involves the Lys(70) amino acid residue in the alpha(1) domain of the MHC class I molecule. The generation of CTL with specificity for B27 under these conditions demonstrates that tolerance to B27 can be subverted by CHLAMYDIA: This indicates a dynamic interrelationship between the pathogen and B27, which may have important implications for B27-related spondyloarthropathies triggered by intracellular bacteria.

Reactive arthritis or chronic infectious arthritis?

Microbes reach the synovial cavity either directly during bacteraemia or by transport within lymphoid cells or monocytes. This may stimulate the immune system excessively, triggering arthritis. Some forms of ReA correspond to slow infectious arthritis due to the persistence of microbes and some to an infection triggered arthritis linked to an extra-articular site of infection.

The reprogrammed host: Chlamydia trachomatis-induced up-regulation of glycoprotein 130 cytokines, transcription factors, and antiapoptotic genes

OBJECTIVE

Infection with Chlamydia trachomatis is a known cause of sexually transmitted diseases, eye infections (including trachoma), and reactive arthritis (ReA). Because the mechanisms of Chlamydia-induced changes leading to ReA are poorly defined, this study sought to identify the target genes involved at the molecular level.

METHODS

Chlamydia-induced changes in host cells were investigated by combining a screening technique, which utilized complementary DNA arrays on C trachomatis-infected and mock-infected epithelial HeLa cells, with real-time reverse transcription-polymerase chain reaction or enzyme-linked immunosorbent assay of gene products. Some responses were additionally demonstrated on human primary chondrocytes and a human synovial fibroblast cell line, both of which served as model cells for ReA.

RESULTS

Eighteen genes (of 1,176) were found to be up-regulated after 24 hours of infection with this obligate intracellular bacterium, among them the glycoprotein 130 family members IL-11 and LIF, the chemokine gene MIP2-alpha, the transcription factor genes EGR1, ETR101, FRA1, and c-jun, the apoptosis-related genes IEX-1L and MCL-1, adhesion molecule genes such as ICAM1, and various other functionally important genes. In the context of this rheumatic disease, the cytokines and transcription factors seem to be especially involved, since various connections to chondrocytes, synoviocytes, bone remodeling, joint pathology, and other rheumatic diseases have been demonstrated.

CONCLUSION

Infection with C trachomatis seems to reprogram the host cells (independent of activation by lipopolysaccharide or other ultraviolet-resistant bacterial components) at various key positions that act as intra- or intercellular switches, suggesting that these changes and similar Chlamydia-induced functional alterations constitute an important basis of the pathogenic inflammatory potential of these cells in ReA. Our results suggest that this approach is generally useful for the broad analysis of host-pathogen interactions involving obligate intracellular bacteria, and for the identification of target genes for therapeutic intervention in this rheumatic disease.

The effect of an anti-HLA-B27 immune response on CTL recognition of Chlamydia

The interplay between triggering bacteria and HLA-B27 in the pathogenesis of the spondyloarthropathies remains one of the most active areas of investigation in the rheumatic diseases. This has proved difficult to study systematically in the clinical setting, and in this study we utilized a rat model to address the influence that B27-related immunity may have on the process of generating anti-Chlamydia immunity. When splenocytes from HLA-B27 DNA-immunized Lewis (LEW) animals received restimulation in vitro with Chlamydia-treated cells from B27-transgenic LEW rats, we observed that in addition to the expected CTL recognition of HLA-B27, there was also anti-Chlamydia CTL killing of Chlamydia-sensitized syngeneic fibroblast targets. This was not seen when responding cells in vitro were naive LEW splenocytes. To confirm the existence of CTLs recognizing both HLA-B27 and Chlamydia, LEW rats were immunized with B27-transgenic LEW cells, instead of the B27 DNA construct. Splenocytes from the immune rats were restimulated in vitro with Chlamydia-treated B27-transgenic LEW cells. In this instance, the CTLs retained the allele-specific recognition of HLA-B27, as well as recognition of Chlamydia-sensitized syngeneic fibroblasts. Thus, if there is prior expansion of an immune response against HLA-B27, then the resulting splenocytes demonstrate a reduced threshold for generating a primary anti-Chlamydia CTL response. These studies implicate a dynamic interrelationship between recognition of HLA-B27 and Chlamydia trachomatis. The results may have implications for deciphering the cellular basis of Chlamydia-induced reactive arthritis.

Persistence of Chlamydia trachomatis is induced by ciprofloxacin and ofloxacin in vitro

An in vitro cell culture model was used to investigate the long-term effect of ciprofloxacin and ofloxacin on infection with Chlamydia trachomatis. Standard in vitro susceptibility testing clearly indicated successful suppression of chlamydial growth. To mimic better in vivo infection conditions, extended treatment with the drugs was started after infection in vitro had been well established. Incubation of such established chlamydial cultures with ciprofloxacin and ofloxacin not only failed to eradicate the organism from host cells, but rather induced a state of chlamydial persistence. This state was characterized by the presence of nonculturable, but fully viable, bacteria and the development of aberrant inclusions. In addition chlamydia exhibited altered steady-state levels of key chlamydial antigens, with significantly reduced major outer membrane protein and near constant hsp60 levels. Resumption of overt chlamydial growth occurred after withdrawal of ciprofloxacin, confirming the viability of persisting chlamydia. In vitro ciprofloxacin results are consistent with clinical data, thereby providing an explanation for treatment failures of ciprofloxacin. Parallel in vitro studies with ofloxacin suggest a better correlation between clinical and laboratory-defined efficacy, although the clinical studies on which this assessment is based did not include monitoring of chlamydial persistence. The data presented here clearly demonstrate that under at least some circumstances, standard determination of MICs and minimal bactericidal concentrations for C. trachomatis allows no more than a simple definition of whether an antibiotic has some anti chlamydial activity; however, such testing is not always sufficient to verify that the antibiotic will eliminate the organism in vivo.

Animal models of the spondyloarthropathies

Several lines of rats transgenic for human leukocyte antigen (HLA)-B27 spontaneously develop a multisystemic inflammatory disease resembling human spondyloarthropathies. This disease is mediated by cells of the immune system and is dependent on the presence of a normal bacterial flora. Both antigen-presenting cells expressing high levels of HLA-B27 and T cells appear to be of importance in the pathogenesis of this model. HLA-B27 transgenic/b2- microglobulin deficient mice also develop arthritis, under the influence of the bacterial flora. In both types of model, CD8+ T cells appear to be unnecessary, arguing against the "arthritogenic peptide" hypothesis.

Chlamydia and associated arthritis

An inflammatory arthritis is known to follow urogenital infection with the intracellular bacterium Chlamydia trachomatis in some individuals, and recent research results have elucidated important aspects of the characteristics of this Chlamydia-associated joint disease. Although the several extra-articular features of Chlamydia-induced arthritis have been defined clinically, their detailed causes remain largely unexplained. Current data indicate that the clinical characteristics of joint disease associated with C. trachomatis infection and those associated with postenteric arthritis are not easily distinguishable, although the response of each to antibiotic therapy does differ. The biologic characteristics of Chlamydia and enteric organisms in the joint show profound differences, and these are probably responsible for the variable responses to drug treatment. Molecular analyses of synovial C. trachomatis have demonstrated that long-term infection of the joint occurs primarily in synovial tissue and that the organism exhibits highly unusual biologic properties in its synovial context. These unusual molecular, biochemical, and other characteristics provide explanations for the frequent culture negativity of joint materials for C. trachomatis and for several other aspects of the arthritogenic process. Much remains to be learned concerning the behavior of this organism in the joint and concerning its interaction with its synovial host cells.

Detection of bacterial DNA in serial synovial samples obtained during antibiotic treatment from patients with septic arthritis

OBJECTIVE

The management of septic arthritis could benefit from sensitive tests that detect the persistence of microorganisms in the joint. The aim of this study was to determine the feasibility of monitoring the presence of bacterial DNA in synovial samples from septic arthritis patients during antibiotic treatment.

METHODS

Synovial fluid (SF) and synovial tissue (ST) samples were collected serially from 6 patients with septic arthritis before and during antibiotic therapy. In addition, peripheral blood (PB) samples were available for polymerase chain reaction (PCR) analysis from 5 of the 6 patients before treatment. All samples were analyzed for the presence of bacterial DNA with the use of a PCR with universal 16S ribosomal RNA primers. Automated sequencing and comparative data analysis were performed to identify the species. These data were compared with Gram staining and culture results.

RESULTS

The bacterial species cultured from the synovium could be identified in all 6 patients using PCR and subsequent sequence analysis of the amplicons. In virtually all cases, positive Gram stain and culture findings in the synovial samples became negative after 2-3 days of antibiotic treatment. Bacterial DNA persisted in the SF and/or ST after culture conversion; in 2 patients, bacterial DNA was still detected at day 10, in 1 patient, at day 20, and in another patient, at day 22 after the initiation of treatment. Synovial samples were available for PCR analysis from 2 patients at day 26. At this time point, bacterial DNA could not be detected anymore. All PB samples were negative by both culture and PCR analysis.

CONCLUSION

PCR analysis can be used to monitor the presence of bacterial DNA in synovial samples from patients with septic arthritis during antibiotic treatment. The absence of bacterial DNA could help in the decision to discontinue antibiotic treatment.

Tumor necrosis factor receptor p55 controls the severity of arthritis in experimental Yersinia enterocolitica infection

OBJECTIVE

To dissect the host defense mechanisms in relation to the development of Yersinia-associated arthritis by evaluating the impact of tumor necrosis factor receptor p55 (TNFRp55) deficiency on Yersinia enterocolitica infection.

METHODS

TNFRp55-/- and C57BL/6 mice were inoculated intravenously with arthritogenic strain 8081 of Yenterocolitica serotype 0:8. Mice were observed daily for generating survival curves and monitoring arthritis. In subsequent sets of experiments, mice were sacrificed at day 14 after infection for examination of histopathology of joints, bacterial clearance, macrophage microbicidal activity, nitric oxide (NO) production, oxidative burst generation, and cytokine production.

RESULTS

There was an 80% mortality rate in TNFRp55-/- mice compared with 25% in the controls at 8 weeks after inoculation with 70 colony-forming units of Y. enterocolitica 0:8. Histologic examination of joint tissues revealed that TNFRp55-/- mice developed more severe arthritis, including cartilage degradation and bony destruction, than controls at day 14 after infection. The more extensive joint pathology in TNFRp55-/- mice was correlated with the higher bacterial load in liver, spleen, and lungs, and with the increased levels of interleukin-10. TNFRp55-/- mice displayed impaired intracellular killing of bacteria by macrophages. This was associated with decreased NO production and impaired oxidative burst activity.

CONCLUSION

This study demonstrates that TNF signaling through TNFRp55 controls the severity of Yersinia-induced arthritis and implicates TNF-mediated macrophage microbicidal activity as a central event in this process.