Chlamydia and associated arthritis

Spondyloarthropathies and arthritis post-infection: a historical perspective

The spondyloarthropathies are a group of conditions characterised by spinal joint pain and have related clinical, epidemiological and genetic-related features. Ankylosing spondylitis, reactive arthritis, the spinal form of psoriatic arthritis and Crohn's and colitis enteropathic arthritis are the major clinical entities of the spondyloarthropathies, and principally occur in HLA-B27 positive individuals. Ankylosing spondylitis is much more common in males than females. Patients are usually seronegative for rheumatoid factor, and extra-articular features including iridocyclitis, mucous membrane and skin lesions: aortitis, may occur in some patients. The reactive arthritis form classically occurs following an infection of the gastrointestinal or genitourinary tract. The Crohn's and colitis enteropathic arthritis forms often have an associated large joint asymmetrical arthritis. Also discussed are acute rheumatic fever and Lyme disease which are conditions where the individual develops arthritis after an infection.

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.

A potential role for chlamydial infection in rheumatoid arthritis development

OBJECTIVES

To assess the relationship between self-reported and serologic evidence of prior chlamydial infection, rheumatoid arthritis (RA)-related autoantibodies and risk of RA-development.

METHODS

This is a nested study within a prospective Swiss-based cohort including all first-degree relatives of RA patients (RA-FDR) who answered a question on past chlamydial infections. Primary outcome was systemic autoimmunity associated with RA (RA-autoimmunity) defined as positivity for anti-citrullinated peptide antibodies (ACPA) and/or rheumatoid factor (RF). Secondary outcomes were high levels of RA-autoimmunity, RA-associated symptoms and RA-autoimmunity, and subsequent seropositive RA diagnosis. We conducted a nested case-control analysis by measuring the serological status against Chlamydia trachomatis' major outer membrane protein. We replicated our analysis in an independent United States-based RA-FDR cohort.

RESULTS

Among 1231 RA-FDRs, 168 (13.6%) developed RA-autoimmunity. Prevalence of self-reported chlamydial infection was significantly higher in individuals with RA-autoimmunity compared with controls (17.9% vs 9.8%, OR = 2.00, 95%CI: 1.27-3.09, p < 0.01). This association remained significant after adjustments (OR = 1.91, 95%CI: 1.20-2.95). Stronger effect sizes were observed in later stages of RA development. There was a similar trend between a positive C. trachomatis serology and high levels of RA-autoimmunity (OR = 3.05, 95% CI: 1.10-8.46, p= 0.032). In the replication cohort, there were significant associations between chlamydial infection and RF positivity and incident RA, but not anti-CCP positivity.

CONCLUSIONS

Self-reported chlamydial infections are associated with elevated RA-autoimmunity in at risk individuals. The differing association of chlamydial infections and ACPA/RF between cohorts will need to be explored in future studies but is consistent with a role of mucosal origin of RA-related autoimmunity.

Bioprospecting by Phage Display of Mimetic Peptides of Chlamydia trachomatis for Use in Laboratory Diagnosis

Background

Chlamydia trachomatis infection is a major public health problem and the most common sexually transmitted infection in the world. Although highly prevalent, 70% to 80% of cases are asymptomatic and undiagnosed.

Purpose

To overcome some limitations in terms of rapid diagnosis, phage display technology was used to bioprospect peptide mimetics of C. trachomatis immunoreactive and immunogenic antigens to be selected for the production of synthetic peptides.

Methods

Initially, IgG from 22 individuals with C. trachomatis and 30 negative controls was coupled to G protein magnetic beads. The phage display technique consisted of biopanning, genetic sequencing, bioinformatics analysis and phage ELISA.

Results

Clones G1, H5, C6 and H7 were selected for testing with individual samples positive and negative for C. trachomatis. Reactions were statistically significant (p < 0.05), with a sensitivity of 90.91, a specificity of 54.55, and AUC values >0.8. One-dimensional analysis with C. trachomatis components indicated that the G1 clone aligned with cell wall-associated hydrolase domain-containing protein, the H5 clone aligned with glycerol-3-phosphate acyltransferase PlsX protein, the C6 clone aligned with a transposase and inactivated derivatives, and the H7 clone aligned with GTP-binding protein. Molecular modeling and three-dimensional analysis indicated the best fit of the four clones with a protein known as chlamydial protease/proteasome-like activity factor (CPAF), an important virulence factor of the bacterium.

Conclusion

The peptides produced by phage display are related to the metabolic pathways of C. trachomatis, indicating that they can be used to understand the pathogenesis of the infection. Because of their high sensitivity and AUC values, the peptides present considerable potential for use in platforms for screening C. trachomatis infections.

Case Report of a Rare Cause of Reactive Arthritis: Leptospirosis

Introduction

Leptospirosis is a zoonosis caused by infection with pathogenic Leptospira species. Leptospirosis has protean manifestations and rare, unusual presentations should be kept in mind in relevant epidemiological scenario. Reactive arthritis refers to acute non-purulent arthritis complicating an infection elsewhere in the body. It is attributed to an immune activation following certain infections; it is, therefore considered as aseptic arthritis. Very few case reports are available attributing leptospirosis as an established cause of reactive arthritis. We present a case of reactive arthritis of the hip joint due to leptospirosis.

Case Report

Here, we present a case of a 12-years- old female child who was admitted to our hospital with complaints of fever, headache, and pain in the right hip joint since past 5 days from admission. Subsequent elaboration revealed a past history of fever, headache, and myalgia for around 5-7 days around a week before the present complaints. There was rat infestation near her house and her father was working as sewage cleaner. Routine investigations, Ultrasonography (USG), Magnetic Resonance Imaging (MRI) of both hips and subsequently, diagnostic hip aspiration was performed. USG revealed synovitis, MRI revealed hip joint arthritis of infective or inflammatory origin. Diagnostic hip aspiration was negative for any microorganism. On 10th day of admission, patient started developing icterus with yellowish discolouration of urine. Patient was evaluated for the cause of jaundice. Screening for Leptospira was positive. Synovial biopsy of hip was performed, which showed inflammation with no specific pathology and no growth of any microorganism. In addition, Leptospira IgM MAC ELISA was done which was positive. Patient was thus confirmed to be having leptospirosis and reactive arthritis as a consequence of it.

Conclusion

The presentation of reactive arthritis secondary to leptospirosis is rare. Leptospirosis can be an etiological factor for reactive arthritis, especially if reactive arthritis is complicated with jaundice.

Skin manifestations in spondyloarthritis

Spondyloarthritides (SpA) like psoriatic arthritis, axial spondyloarthritis/ankylosing spondylitis, reactive arthritis and inflammatory bowel disease (IBD)-associated SpA can present with characteristic skin manifestations. These SpA-associated skin disorders may precede joint involvement, reflect a loss of efficacy of a current systemic treatment or can even be treatment associated. Cutaneous manifestations in SpA not only add additional morbidity with physical impact but also impose a psychosocial burden on affected patients. Psoriasis (PsO) - the main skin disease in SpA - has a variety of clinical presentations, including plaque-type PsO, inverse PsO, guttate PsO, erythrodermic PsO, nail PsO and pustular types. SpA associated with IBD presents with neutrophilic and granulomatous skin disorders, including pyoderma gangrenosum, hidradenitis suppurativa and cutaneous Crohn's disease. Reactive arthritides has a favourable prognosis and may feature keratoderma blenorrhagicum or balanitis circinatum as typical skin manifestations. Immunologically, SpA-associated skin diseases share interleukin (IL)-17 and IL-23 dysregulation but show distinctive genetic and immunological profiles. Therefore, they vary in their treatment responses to targeted therapies with biologicals or small molecules. In this review, we highlight the clinical presentation of skin manifestations in SpA and discuss therapeutic approaches in this interdisciplinary field.

Infectious arthritis and the temporomandibular joint. A review

OBJECTIVE

Microorganisms can cause acute infectious arthritis, chronic infectious arthritis, or reactive inflammatory arthritis. The aim of this study is to perform a narrative review of the pathophysiology, etiology, and diagnostic features of infectious arthritis and TMJ infectious arthritis.

METHODS

A search of the literature was performed using Medline, Scielo, Embase, and Google Scholar databases. The terms employed for the search were "Temporomandibular Joint Disorders" and "Infectious Arthritis"; or "Septic Arthritis"; or "Bacterial, Fungal, or Viral Arthritis." Over three hundred articles were screened for eligibility.

RESULTS

The selected articles were utilized to perform a narrative review of the general aspects of infectious arthritis and infectious arthritis affecting the TMJ.

CONCLUSION

Infectious arthritis is a rare, yet very morbid, form of arthritis. Understanding general aspects of joint infections and specific features of TMJ infectious arthritis is imperative for an adequate diagnosis.

No evidence of Chlamydia pneumoniae in the synovia of patients with osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is a common cause of disability affecting millions of people of all ages worldwide. The pathogenesis involves an inflammatory component, but the cause of the inflammation remains incompletely understood. The intracellular bacteria Chlamydia trachomatis and C. pneumoniae have been demonstrated in patients with reactive arthritis. Both of these microorganisms can cause chronic and persistent infections, with C. trachomatis being the most common cause of reactive arthritis. This study was performed to investigate the presence of C. pneumoniae in a large number of patients with primary OA.

METHODS

The study included 75 patients who underwent total knee arthroplasty. During surgery, a synovial biopsy was performed and synovial fluid drawn. Real-time polymerase chain reaction (PCR) of C. pneumoniae was run on all patients, and real-time PCR of bacterial 16S rDNA was conducted on 30 of the 75 patients to screen for the presence of other bacteria.

RESULTS

Real-time PCR showed no evidence of the presence of C. pneumoniae in the patients' specimens, nor were other bacteria detected.

CONCLUSIONS

Although an inflammatory component is part of the pathogenesis of OA, we found no evidence indicating that C. pneumoniae is a stimulator of that inflammation.

The incidence of sexually acquired reactive arthritis: a systematic literature review

Reactive arthritis (ReA) is an inflammatory spondyloarthritis occurring after infection at a distant site. Chlamydia trachomatis is proposed to be the most common cause of ReA, yet the incidence of sexually acquired ReA (SARA) has not been well established. We therefore carried out a systematic literature review to collate and critically evaluate the published evidence regarding the incidence of SARA. MEDLINE and EMBASE databases were searched using free-text and MeSH terms relating to infection and ReA. The title and abstract of articles returned were screened independently by two reviewers and potentially relevant articles assessed in full. Data was extracted from relevant articles and a risk of bias assessment carried out using a validated tool. Heterogeneity of study methodology and results precluded meta-analysis. The search yielded a total of 11,680 articles, and a further 17 were identified from review articles. After screening, 55 papers were assessed in full, from which 3 met the relevant inclusion criteria for the review. The studies reported an incidence of SARA of 3.0-8.1 % and were found to be of low to moderate quality. More studies are required to address the lack of data regarding the incidence of SARA. Specific and sensitive classification criteria must be developed in order for consistent classification and valid conclusions to be drawn. In clinical practice, it is recommended clinicians discuss the possibility of ReA developing at the time of STI diagnosis and to encourage patients to return if they experience any relevant symptoms.

Incidence of Chlamydia trachomatis infection in patients with reactive arthritis

Objectives

The aim of the study was to evaluate the incidence of Chlamydia trachomatis in patients with reactive arthritis (ReA) within the area of the Podlaskie province (north eastern Poland).

Material and methods

The study concerned 323 patients including 132 women and 191 men diagnosed with ReA. The material for C. trachomatis was collected from the urethra in men and the cervical canal in women. Also, every patient was tested for the presence of anti-C. trachomatis IgG class antibodies, while 121 individuals were additionally tested for IgA class antibodies. In the direct studies, the direct immunofluorescence (DIF) method or polymerase chain reaction (PCR) was used. The immunoenzymatic method was used to detect anti-C. trachomatis antibodies. The control group in the case of direct studies comprised 125 individuals, while in the case of serology research it included 127 (IgG) and 109 (IgA) persons.

Results

Chlamydia trachomatis infection in the urethral and cervical smears was found in 42 patients (13.0%) including 20 women (15.2%) and 22 men (11.5%). In the control group chlamydia was detected in 3 patients (2.4%) including 4% of women and 2% of men. IgA class antibodies were present in 10/121 (8.3%) patients, similarly in women and in men (8.2% and 8.3% respectively). In the control group the specific IgA class antibodies were found in 3/85 patients (3.5%). Anti-C. trachomatis IgG antibodies were found in 70/323 patients (21.7%), similarly in men and women.

Conclusions

Chlamydia trachomatis is a common bacterial factor observed in the genitourinary system of patients with ReA. The outcomes of studies within the Podlaskie province indicate less frequent presence of chlamydial infection compared with Dolnośląskie province.

No correlations between detecting the presence of C. trachomatis in the urogenital tract and the presence of specific antibodies in the serum of ReA patients were observed.

Concurrent direct studies of the urogenital tract and a serological blood test increase the chance of detecting C. trachomatis infection.

Differential infection outcome of Chlamydia trachomatis in human blood monocytes and monocyte-derived dendritic cells

Background

Chlamydia trachomatis is an intracellular bacteria which consist of three biovariants; trachoma (serovars A-C), urogenital (serovars D-K) and lymphogranuloma venereum (L1-L3), causing a wide spectrum of disease in humans. Monocytes are considered to disseminate this pathogen throughout the body while dendritic cells (DCs) play an important role in mediating immune response against bacterial infection. To determine the fate of C. trachomatis within human peripheral blood monocytes and monocyte-derived DCs, these two sets of immune cells were infected with serovars Ba, D and L2, representative of the three biovariants of C. trachomatis.

Results

Our study revealed that the different serovars primarily infect monocytes and DCs in a comparable fashion, however undergo differential infection outcome, serovar L2 being the only candidate to inflict active infection. Moreover, the C. trachomatis serovars Ba and D become persistent in monocytes while the serovars predominantly suffer degradation within DCs. Effects of persistence gene Indoleamine 2, 3-dioxygenase (IDO) was not clearly evident in the differential infection outcome. The heightened levels of inflammatory cytokines secreted by the chlamydial infection in DCs compared to monocytes seemed to be instrumental for this consequence. The immune genes induced in monocytes and DCs against chlamydial infection involves a different set of Toll-like receptors, indicating that distinct intracellular signalling pathways are adopted for immune response.

Conclusion

Our results demonstrate that the host pathogen interaction in chlamydia infection is not only serovar specific but manifests cell specific features, inducing separate immune response cascade in monocytes and DCs.

Chlamydia trachomatis is present and metabolically active during the remitting phase in synovial tissues from patients with chronic Chlamydia-induced reactive arthritis

BACKGROUND

Patients with chronic Chlamydia-induced reactive arthritis (ReA) often show a remitting-relapsing disease phenotype. Some information regarding bacterial and host responses to one another during active disease is available but no information for quiescence. This article presents the first molecular genetic insight into the behavior of bacterium and host during remitting ReA.

METHODS

Synovial biopsies were procured from the knees of 4 patients with quiescent ReA by the Parker-Pearson technique. Nucleic acids prepared from them were analyzed by real-time polymerase chain reaction (PCR) and reverse transcription-PCR, and results were compared with data averaged from the knee synovial tissue samples of 10 patients with active ReA.

RESULTS

Real-time PCR indicated that bacterial load in remitting samples was approximately 20% of that in active disease samples. Transcripts from the p60-encoding gene were equal to or higher than those seen in active disease. Messenger RNAs (mRNAs) from the paralog p60-encoding genes were equal to or lower than those of active disease. Host mRNAs encoding interleukin-10, tumor necrosis factor-α and interferon-γ were 4-fold lower than those in active disease samples, whereas monocyte chemotactic protein 1 and regulated upon activation, normal t-cell expressed, and secreted mRNA levels were equal to or higher.

CONCLUSIONS

Bacterial load in synovial tissue of patients with remitting disease is lower than that of active disease, but mRNAs encoding proinflammatory proteins are equal to or higher than those of active disease. Transcription in the host is attenuated for cytokines and chemokines. These initial results demonstrate that organism is present and metabolically active in synovium during the remitting phase of chronic Chlamydia-induced ReA and that the genetic events characterizing quiescence are complex.

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.

Reactive arthritis

Reactive arthritis (ReA) can be defined as the development of sterile inflammatory arthritis as a sequel to remote infection, often in the gastrointestinal or urogenital tract. Although no generally agreed-upon diagnostic criteria exist, the diagnosis is mainly clinical, and based on acute oligoarticular arthritis of larger joints developing within 2-4 weeks of the preceding infection. According to population-based studies, the annual incidence of ReA is 0.6-27/100,000. In addition to the typical clinical picture, the diagnosis of ReA relies on the diagnosis of the triggering infection. Human leucocyte antigen (HLA)-B27 should not be used as a diagnostic tool for a diagnosis of acute ReA. In the case of established ReA, prolonged treatment of Chlamydia-induced ReA may be of benefit, not only in the case of acute ReA but also in those with chronic ReA or spondylarthropathy with evidence of persisting chlamydia antigens in the body. In other forms of ReA, there is no confirmed evidence in favour of antibiotic therapy to shorten the duration of acute arthritis. The outcome and prognosis of ReA are best known for enteric ReA, whereas studies dealing with the long-term outcome of ReA attributable to Chlamydia trachomatis are lacking.

Myeloradiculitis with meningoencephalopathy and optic neuritis in a case of previous Chlamydia psittaci infection

We present a case of optic neuritis and myelo-radiculopathy as a late association following Chlamydia psittaci infection. A 45-year-old female patient with a prior history of C psittaci pneumonia and subsequent reactive arthritis presented to the neurology unit with severe headache, constitutional symptoms and monocular disturbance in vision. Clinical examination revealed focal signs with brisk upper limb reflexes compared to lower limbs and mild left-sided pyramidal signs. Systemic inflammatory markers were raised and serological studies showed no evidence of re-infection. MRI showed multiple high signal foci within the brain parenchyma and pachymeningeal thickening and enhancement. There was marked clinical and haematological improvement with high dose corticosteroids.

The potential for the noninvasive delivery of polymeric nanocarriers using propellant-based inhalers in the treatment of Chlamydial respiratory infections

A novel strategy for pulmonary delivery of polymeric nanocarriers (NCs) pressurized-metered dose inhalers (pMDIs) is reported in this work. Core-shell particles consisting of a water soluble, hydrofluoroalkane(HFA)-philic biodegradable copolymer of chitosan and poly(lactic acid), and a core of poly(d,l-lactide-co-glycolide) (PLGA) NCs were prepared by a modified emulsification-diffusion methodology. Dispersions of the core-shell particles in HFA propellant revealed enhanced physical stability compared to polymeric NCs alone, and more importantly, excellent aerosol characteristics as determined by inertial impaction studies. Confocal microscopy revealed that the polymeric NCs from such core-shell particles are capable not only to be taken up by Calu-3 (airway epithelial) cells that have been infected with Chlamydia pneumoniae, an intracellular pathogen, but are also internalized within chlamydial inclusions. Our results suggest that the proposed methodology can be used as a general platform for the delivery of polymeric NCs to the respiratory tract using the inexpensive pMDIs, and that such an approach may be used to target and deliver drugs to treat chlamydial-related infections.

Detection of Chlamydophila pneumoniae in patients with arthritis: significance and diagnostic value

The aim of this study was to assess the potential clinical implications of Chlamydophila pneumoniae in patients with acute and chronic arthritic diseases and to investigate whether blood monocytes might reflect a concomitant synovial or persistent systemic infection. C. pneumoniae was investigated with advanced PCR and reverse transcriptase (RT) PCR techniques targeting different genes and combined with cell line cultures, in synovial fluid (SF) and peripheral blood mononuclear cell (PBMC) specimens collected from 28 patients with arthritis. Five out of twenty-eight patients (17.8%) were found to have C. pneumoniae DNA in either SF or PBMC specimens. Their diagnosis was reactive arthritis (ReA), S.A.P.H.O syndrome, psoriatic arthritis, undifferentiated oligoarthritis (UOA) and ankylosing spondylitis (AS). Specimens from patients with UOA and AS had also mRNA transcripts but those from AS yielded C. pneumoniae growth after co-culture. Moreover, C. pneumoniae DNA levels measured by Real-Time PCR (LightCycler) were higher in PBMC specimens compared to those found in SF at the end of antibiotic treatment. C. pneumoniae may have a role as triggering factor also in chronic arthritides including AS. The combined use of culture and molecular tools increases detection rates and improves the overall sensitivity, suggesting their potential use to detect C. pneumoniae. The different kinetics of bacterial DNA at both peripheral and synovial levels should be taken into consideration when monitoring and evaluating the effectiveness of antibiotic treatment.

Chlamydia trachomatis antigens in enteroendocrine cells and macrophages of the small bowel in patients with severe irritable bowel syndrome

BACKGROUND

Inflammation and immune activation have repeatedly been suggested as pathogentic factors in irritable bowel syndrome (IBS). The driving force for immune activation in IBS remains unknown. The aim of our study was to find out if the obligate intracellular pathogen Chlamydia could be involved in the pathogenesis of IBS.

METHODS

We studied 65 patients (61 females) with IBS and 42 (29 females) healthy controls in which IBS had been excluded. Full thickness biopsies from the jejunum and mucosa biopsies from the duodenum and the jejunum were stained with a monoclonal antibody to Chlamydia lipopolysaccharide (LPS) and species-specific monoclonal antibodies to C. trachomatis and C. pneumoniae. We used polyclonal antibodies to chromogranin A, CD68, CD11c, and CD117 to identify enteroendocrine cells, macrophages, dendritic, and mast cells, respectively.

RESULTS

Chlamydia LPS was present in 89% of patients with IBS, but in only 14% of healthy controls (p < 0.001) and 79% of LPS-positive biopsies were also positive for C. trachomatis major outer membrane protein (MOMP). Staining for C. pneumoniae was negative in both patients and controls. Chlamydia LPS was detected in enteroendocrine cells of the mucosa in 90% of positive biopsies and in subepithelial macrophages in 69% of biopsies. Biopsies taken at different time points in 19 patients revealed persistence of Chlamydia LPS up to 11 years. The odds ratio for the association of Chlamydia LPS with presence of IBS (43.1; 95% CI: 13.2-140.7) is much higher than any previously described pathogenetic marker in IBS.

CONCLUSIONS

We found C. trachomatis antigens in enteroendocrine cells and macrophages in the small bowel mucosa of patients with IBS. Further studies are required to clarify if the presence of such antigens has a role in the pathogenesis of IBS.

Rheumatoid arthritis: Disease or syndrome?

Rheumatoid arthritis (RA) has been described in the medical literature for over two hundred years, but its etiology remains unknown. RA displays phenotypic heterogeneity, and it is a relatively prevalent clinical entity: it affects approximately 1% of the population, resulting in enormous pathologic sequelae. Earlier studies targeting the cause(s) of RA suggested potential infectious involvement, whereas more recent reports have focused on a genetic origin of the disease. However, neither infection nor genetics, nor any other single factor is currently accepted as causative of RA. In this article we review studies relating to the etiology of RA, and those of several related matters, and we conclude that the literature indeed does provide insight into the causes underlying the initiation of RA pathogenesis. Briefly, given the remarkable phenotypic variation of RA, especially in its early stages, as well as a number of other characteristics of the condition, we contend that RA is not a discrete clinical entity with a single etiological source. Rather, we argue that it represents a common clinical endpoint for various starting points, each of which is largely guided by as yet poorly understood aspects of the genetic background of the affected individual. Adoption of this alternative view of the origin of RA will have significant consequences for future research and for development of new therapeutic interventions for this burdensome condition.

Patients with Chlamydia-associated arthritis have ocular (trachoma), not genital, serovars of C. trachomatis in synovial tissue

Some individuals with a genital Chlamydia trachomatis infection develop inflammatory arthritis, but it is unknown whether particular chlamydial serovar(s) engender the disease more often than others. We defined serovar in synovial tissues from arthritis patients infected with this organism. DNA from synovial biopsies of 36 patients with PCR-confirmed synovial C. trachomatis was analyzed. Diagnoses included reactive arthritis, undifferentiated oligoarthritis, rheumatoid arthritis, and osteoarthritis. The chlamydial omp1 and trpA genes were amplified, cloned, and 10 or more clones from each sample were sequenced. The cytotoxin locus also was analyzed. omp1 sequences showed 2 patients having only C. trachomatis A serovar, 1 with only B, and 33 having only C, all ocular serovars. Analyses of trpA and the cytotoxin locus uniformly displayed standard ocular serovar characteristics for each patient. Identification of ocular chlamydial serovars in the synovia of arthritis patients is unexpected. These observations suggest that urogenital chlamydial infections, while consisting primarily of organisms of genital serovars, include some of ocular serovar(s). They further suggest that during such infections unknown selection pressures favor establishment of the latter in the synovium to the exclusion of genital serovar chlamydiae.

[Applications of molecular pathology in the diagnosis of joint infections]

The diagnosis of infections in patients with arthritis and/or joint prostheses requires interdisciplinary cooperation and the use of up-to-date methods. Massive bacterial infection can be identified by bacterial culture, and minimal infection can be detected by molecular pathological methods. These processes include specific enrichment of bacterial and fungal DNA, amplification, and identification of the DNA by gel electrophoresis, sequencing techniques, and chip technologies.Anamnesis (enteral or urogenital infection), the clinical picture (oligoarthritis), and further parameters (e.g., HLA B27 status) are important for the diagnosis of reactive arthritis. In many cases of reactive arthritis, molecular methods allow detection of bacterial DNA or RNA in synovial fluid or tissue. Molecular pathological methods allow the fast and reliable differential diagnosis of granulomatous synovialitis without prior cultivation of bacteria or fungi. The development of new molecular pathological methods for detecting bacterial and fungal nucleic acids will increase diagnostic accuracy.

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.

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.

Altered host:pathogen interactions conferred by the Blau syndrome mutation of NOD2

Blau syndrome (BS) is a rare familial granulomatous disease manifested by uveitis, arthritis and skin rash. BS has recently been found to be associated with a distinctive mutation in NOD2, which encodes an intracellular toll-like receptor. We have compared host cell interaction with bacterial challenge in U937 cells expressing wild type human NOD2 (NOD2(wt)), mutant NOD2 (NOD2(Blau)), or a vector control (VC). The cells were incubated with Salmonella typhimurium. Intracellular uptake was assessed by harvesting the cells at different time points following invasion and quantitating the CFU, recovered after gentamicin treatment to kill extracellular organisms. Expression of TNF-alpha, TLR2 and TLR4 was determined by semi-quantitative RT-PCR under resting conditions and after stimulation by bacteria. Invasion of target cells with S. typhimurium was diminished in the presence of NOD2(Blau). Expression of TNF-alpha mRNA was enhanced following bacterial invasion in all cell lines but NOD2(Blau) was associated with a more rapid decline in TNF-alpha expression. Kinetics of intracellular clearance of bacteria indicated a relative defect in NOD2(Blau) compared to controls. This clearance defect may be related to the lack of sustained TNF-alpha seen in the early stages. These events were not related to differential TLR2 or TLR4 expression since there were no significant differences seen between the cell lines after bacterial stimulation. Our findings indicate that the NOD2 mutation associated with this syndrome alters host:microbial interaction, and this may have relevance to triggering factors in the ocular and joint inflammation seen in BS.

Reactive arthritis or post-infectious arthritis?

The term 'reactive arthritis' was first used in 1969 to describe the development of sterile inflammatory arthritis as a sequel to remote infection, often in the gastrointestinal or urogenital tract. The demonstration of antigenic material (e.g. Salmonella and Yersinia lipopolysaccharide), DNA and RNA, and, in occasional cases, evidence of metabolically active Chlamydia spp. in the joints has blurred the boundary between reactive and post-infectious forms of arthritis. No validated and generally agreed diagnostic criteria exist, but the diagnosis of reactive arthritis is mainly clinical based on acute oligoarticular arthritis of larger joints that develops within 2-4 weeks of the preceding infection. In about 25% of patients, the infection can be asymptomatic. Diagnosis of the triggering infection is very helpful for the diagnosis of reactive arthritis. This is mainly achieved by isolating the triggering infection (stools, urogenital tract) by cultures (stool cultures for enteric microbes) or ligase reaction (Chlamydia trachomatis). However, after the onset of arthritis, this is less likely to be possible. Therefore, the diagnosis must rely on various serological tests to demonstrate evidence of previous infection, but, these serological tests are unfortunately not standardized. Treatment with antibiotics to cure Chlamydia infection is important, but the use of either short or prolonged courses of antibiotics in established arthritis has not been found to be effective for the cure of arthritis. The long-term outcome of reactive arthritis is usually good; however, about 25-50% of patients, depending on the triggering infections and possible new infections, subsequently develop acute arthritis. About 25% of patients proceed to chronic spondyloarthritis of varying activity.

Detection of Chlamydia in the peripheral blood cells of normal donors using in vitro culture, immunofluorescence microscopy and flow cytometry techniques

BACKGROUND

Chlamydia trachomatis (Ct) and Chlamydia pneumoniae (Cp) are medically significant infectious agents associated with various chronic human pathologies. Nevertheless, specific roles in disease progression or initiation are incompletely defined. Both pathogens infect established cell lines in vitro and polymerase chain reaction (PCR) has detected Chlamydia DNA in various clinical specimens as well as in normal donor peripheral blood monocytes (PBMC). However, Chlamydia infection of other blood cell types, quantification of Chlamydia infected cells in peripheral blood and transmission of this infection in vitro have not been examined.

METHODS

Cp specific titers were assessed for sera from 459 normal human donor blood (NBD) samples. Isolated white blood cells (WBC) were assayed by in vitro culture to evaluate infection transmission of blood cell borne chlamydiae. Smears of fresh blood samples (FB) were dual immunostained for microscopic identification of Chlamydia-infected cell types and aliquots also assessed using Flow Cytometry (FC).

RESULTS

ELISA demonstrated that 219 (47.7%) of the NBD samples exhibit elevated anti-Cp antibody titers. Imunofluorescence microscopy of smears demonstrated 113 (24.6%) of samples contained intracellular Chlamydia and monoclonals to specific CD markers showed that in vivo infection of neutrophil and eosinophil/basophil cells as well as monocytes occurs. In vitro culture established WBCs of 114 (24.8%) of the NBD samples harbored infectious chlamydiae, clinically a potentially source of transmission, FC demonstrated both Chlamydia infected and uninfected cells can be readily identified and quantified.

CONCLUSION

NBD can harbor infected neutrophils, eosinophil/basophils and monocytes. The chlamydiae are infectious in vitro, and both total, and cell type specific Chlamydia carriage is quantifiable by FC.

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.

Recent advances in reactive arthritis

Reactive arthritis (ReA), one of the spondyloarthropathies, is an infectious related disease that occurs in a genetically predisposed individual, characterized by an immune-mediated synovitis with intra-articular persistence of viable nonculturable bacteria and/or immunogenic bacterial antigens. ReA long term prognosis is not as good as it was earlier believed. Two-thirds of patients develop prolonged joint discomfort, low back pain, or enthesopathies after acute ReA, and 15% to 30% of them develop chronic symptoms. The therapeutic options for patients with the more severe forms of the disease have been rather limited. The efficacy of tumor necrosis factor antagonists in other spondyloarthritis suggested that anticytokine therapy could also be effective for ReA. This paper reviews the latest concepts in urogenital and postenteric human leukocyte antigen-B27-associated ReA.

Chlamydia pneumoniae arthritis in a patient with common variable immunodeficiency

BACKGROUND

Arthritis is an important and sometimes life-threatening complication in patients with common variable immunodeficiency (CVID).

OBJECTIVE

To describe a patient with CVID and arthritis due to Chlamydia pneumoniae, which is usually regarded as a respiratory tract pathogen and has not previously been detected in the synovial fluid by cell culture technique.

METHODS

Routine bacteriologic, virologic, mycologic, and tuberculosis cultures were performed. The patient's synovial fluid was examined for fastidious organisms that might be causative pathogens of arthritis, such as chlamydiae, and special cell culture methods were used. Serologic tests were performed to determine viral and bacteriologic etiology.

RESULTS

The patient had a history of recurrent respiratory tract infections, and the latest exacerbation was followed by arthritis. Cytologic examination of the fluid yielded abundant lymphocytes. Chlamydia pneumoniae was detected in synovial fluid specimens by cell culture technique. Her nasopharyngeal swab and sputum culture specimens were also positive for this pathogen. She was diagnosed as having arthritis caused by C pneumoniae and was given antibiotherapy.

CONCLUSION

Chlamydia pneumoniae should be kept in mind as a causative pathogen in patients with CVID and arthritis, especially when effusion fluid is full of lymphocytes rather than polymorphonuclear cells and no organism is grown on routine cultures.

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.

Endogenous interleukin-6, but not tumor necrosis factor α, contributes to the development of toll-like receptor 4/myeloid differentiation factor 88-mediated acute arthritis in mice

OBJECTIVE

To generate a mouse model of reactive arthritis (ReA), an aseptic synovitis that develops in joints distant from the primary bacterial infection site, to examine roles for Toll-like receptors (TLRs) that recognize bacterial components involved in the development of this arthritis, and to identify the cytokine(s) relevant to this arthritis.

METHODS

Mice were treated with cell wall extract from Escherichia coli (ECW) gram-negative bacterium by injection into the footpads. Seven days later, the mice were challenged with lipopolysaccharide (LPS), a TLR-4 ligand, which was injected into the knee joint cavity. To investigate the cytokine(s) involved in this arthritis, mice deficient in various arthritogenic cytokines, such as interleukin-6 (IL-6), IL-12, IL-18, interferon-gamma, and tumor necrosis factor alpha (TNFalpha), were sequentially treated with ECW and LPS.

RESULTS

ECW-primed mice manifested acute severe arthritis after intraarticular challenge with ECW or LPS, while unprimed mice exhibited modest changes after these challenges. Mutant mice lacking functional TLR-4 or myeloid differentiation factor 88 (MyD88), an adaptor molecule of TLR-4 signaling, were resistant to this arthritis. Although both TNFalpha and IL-6 were equally expressed in the joint after LPS challenge, Il6(-/-) mice, but not Tnf(-/-) mice, were resistant to ECW/LPS-induced arthritis.

CONCLUSION

Our present results clearly indicate the importance of priming with ECW and the requirement of TLR-4/MyD88-mediated IL-6, but not TNFalpha, for the development of ECW/LPS-induced arthritis. LPS-induced IL-6, in the absence of TNFalpha, mediates LPS-induced arthritis. These results suggest that IL-6 is a rational target for therapeutic regimens for inflammatory arthritis, including ReA and rheumatoid arthritis.

Chlamydia-induced arthritis

PURPOSE OF REVIEW

Chlamydia-induced arthritis is the most frequent form of reactive arthritis in Western countries. This article gives an overview of the recent findings with respect to diagnosis, pathogenesis, and therapy of the disease.

RECENT FINDINGS

Recent advances in the modification and standardization of polymerase chain reaction techniques give promise to identify Chlamydia more frequently from joint samples. Based on the sequenced chlamydial genome, considerable progress has been achieved in the understanding of the Chlamydia-host cell interaction, indicating that persistence is an alternate state of the bacteria used by Chlamydia to escape the immune system of the host rather than a general stress response. Furthermore, Chlamydia has the ability to reprogram the host cell by chlamydial effector proteins, which are transported from the inclusion into the host cell cytoplasm. The role of HLA-B27 is discussed in view of the pathogenesis of the disease. HLA-B27 should be considered a risk factor for chronic and/or axial disease rather than a true susceptibility factor for the development of Chlamydia-induced arthritis. No progress has been made in terms of causative therapy aiming at eradication of the bacteria. Tumor necrosis factor-alpha blocking agents may represent a new option in cases that are refractory to therapy.

SUMMARY

Molecular biology not only has improved the ability to detect Chlamydia in the joint for diagnostic purposes but also has extended the current understanding of the pathogenesis of the disease. In contrast to this progress, causative therapy of Chlamydia-induced arthritis is still an unfulfilled need.

Is there any relationship between Chlamydophila pneumoniae infection and juvenile idiopathic arthritis?

The role of Chlamydophila pneumoniae in the development and exacerbation of juvenile idiopathic arthritis (JIA) was investigated. Blood samples were taken from 60 JIA patients during an active disease period and for 4 weeks after. Synovial fluid samples were obtained from 20 of the 60 patients. In addition, 22 patients with familial Mediterranean fever (FMF) during the active period and 35 healthy children were included in the study as control groups. Synovial fluid samples were also obtained from three children with FMF. IgG, IgM and IgA levels against C. pneumoniae in serum samples were studied by immunofluorescence and IgG antibody and PCR studies were performed for C. pneumoniae DNA in synovial fluid samples. Twenty-nine (48.3 %) patients with JIA, 18 (81.8 %) patients with FMF and 22 (62.8 %) healthy children were found to be pre-infected with C. pneumoniae. Pre-infection with C. pneumoniae among FMF patients was found to be significantly higher than among those with JIA. We did not find a significant difference between JIA patients and healthy children. Chronic C. pneumoniae infection was observed only in six JIA patients, one FMF patient and two healthy children. Synovial fluid antibodies were found at higher than 1/512-fold dilution in one JIA patient and four times higher than normal serum in three JIA patients. C. pneumoniae DNA was not detected in any synovial fluid sample from FMF or JIA patients by PCR. In conclusion, C. pneumoniae infection does not have a triggering or a progressive effect on the clinical situation in JIA aetiopathogenesis, as a result of a multifactorial aetiology. New, extensive and serial studies (especially PCR studies of synovial tissue) are needed in order to confirm the indirect results.

Chlamydia trachomatis-specific human CD8+ T cells show two patterns of antigen recognition

Chlamydia trachomatis is an intracellular gram-negative bacteria which causes several clinically important diseases. T-cell-mediated immunity and the production of gamma interferon (IFN-gamma) are known to be essential for the clearance of the bacteria in vivo. Here we have investigated CD8(+)-T-cell responses to C. trachomatis in patients with previous episodes of chlamydia infection. To isolate C. trachomatis-specific CD8(+)-T-cell lines, dendritic cells (DC) were infected with C. trachomatis and cocultured with purified CD8(+) T cells to generate C. trachomatis-specific CD8(+)-T-cell lines which were then cloned. Two patterns of recognition of C. trachomatis-infected cells by CD8(+)-T-cell clones were identified. In the first, C. trachomatis antigens were recognized in association with classical class I HLA antigens, and responses were inhibited by class I HLA-specific monoclonal antibodies. The second set of clones was unrestricted by classical HLA class I, and further studies showed that CD1 molecules were also not the restriction element for those clones. Both types of clones produced IFN-gamma in response to C. trachomatis and were able to lyse C. trachomatis-infected target cells. However, unrestricted clones recognized C. trachomatis-infected cells at much earlier time points postinfection than HLA-restricted clones. Coculture of C. trachomatis-infected DC with the C. trachomatis-specific clones induced DC activation and a rapid enhancement of interleukin-12 (IL-12) production. Early production of IL-12 during C. trachomatis infection, facilitated by unrestricted CD8(+)-T-cell clones, may be important in ensuring a subsequent Th1 T-cell-mediated response by classical major histocompatibility complex-restricted CD4(+) and CD8(+) T cells.

More than just innate immunity: comparative analysis of Chlamydophila pneumoniae and Chlamydia trachomatis effects on host-cell gene regulation

Chlamydophila pneumoniae and Chlamydia trachomatis cause infections of the respiratory or urogenital tract. In addition, both species have been associated with atherosclerosis or reactive arthritis respectively. For these intracellular pathogens the interaction with their host-cells is of particular importance. To get insight into this relationship, we conducted a comparative analysis of the host-cell gene regulation of human epithelial cells during infection with Chlamydia. In a screening of HeLa cells by Affymetrix-microchips, numerous regulated host-genes were identified. A detailed expression profile was obtained for 14 genes by real-time RT-PCR - comparing C. pneumoniae, C. trachomatis and intracellular S. typhimurium. The transcriptional responses induced by C. pneumoniae were similar (but usually smaller) compared to C. trachomatis, some were absent. UV-inactivated bacteria induced no differential gene expression suggesting that pathomechanisms other than those associated with innate immunity play here an important role. The expression pattern induced by Salmonella differed substantially. These genus- or group-specific transcriptional response patterns elicited by viable intracellular pathogens may considerably contribute to the different pathologies encountered in the clinic.

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.

Differential expression of three Chlamydia trachomatis hsp60-encoding genes in active vs. persistent infections

Real time RT-PCR was used to assess expression of the three Chlamydia trachomatis hsp60-encoding genes (Ct110, Ct604, Ct755) over time in in vitro systems of active vs. persistent infection, and in synovial samples from patients with Chlamydia-induced arthritis. In HEp-2 cells actively infected with C. trachomatis (serovar K), mRNA from Ct110 (groEL) was apparent by 8 h post-infection (p.i.) and increased more than 10-fold through 48 h p.i.; mRNA from Ct604 followed a similar pattern. Transcripts from Ct755 were abundant at 8 h p.i. and remained 2-3-fold higher than those from Ct110 at all times. In persistently infected human monocytes in culture, expression of Ct110 and Ct755 was low from 1 to 7d p.i., while mRNA from Ct604 was abundant at 1d p.i. and increased more than 3-fold from 1 to 3d p.i., as the organism transited to the persistent state. Those mRNA levels remained high through 7d p.i. Real time analyses of RNA/cDNA from synovial tissue of patients with Chlamydia-associated arthritis showed high Ct604 mRNA levels, consistent with results from the in vitro monocyte system of persistence. These data demonstrate that each chlamydial hsp60-encoding gene is expressed independently, and that the three genes are expressed differentially in active vs. persistent infection. The results further suggest that the Ct604 gene product may function importantly during chlamydial persistence.

Identification of HLA-B27-restricted peptides in reactive arthritis and other spondyloarthropathies: computer algorithms and fluorescent activated cell sorting analysis as tools for hunting of HLA-B27-restricted chlamydial and autologous crossreactive peptides involved in reactive arthritis and ankylosing spondylitis

The illustrated clinical and experimental results demonstrate the strong relationship between the MHC class I antigen HLA-B27 and synovial CD8+ T cells with specificity for bacterial and possible self-antigen in SpA. These new aspects obtained in recent experimental and clinical studies might also provide clues to the pathomechanisms of joint inflammation in SpA. In particular, the newly developed techniques will be of great relevance in the near future. New and more precise bioalgorithms reflecting new insights in the biology and biochemistry of proteins as recently presented [98, 99] can be helpful (e.g., a program with an improved prediction of the features of immunoproteasomes). Intracellular and secreted cytokine staining by FACScan allows examination of a great number of cells expressing certain antigens in response to certain stimuli. The analysis of T-cell responses with tetramer/peptide complexes can be useful to screen tissue sections for TCR, recognizing foreign or self-derived epitopes on those complexes loaded with selected (e.g., bacterial) peptides. Identification of arthritogenic peptides and a further understanding of the immunology of the pathomechanisms in SpA might open ways to design new peptide vaccines to prevent inflammation, autoimmunity, and other diseases by early intervention [100].

Reactive arthritis: newer developments

Reactive arthritis (ReA) is characterized by an aseptic inflammatory articular involvement occurring in a genetically predisposed individual secondary to an infectious process localized outside the joint. ReA usually refers to an acute or insidious oligoarthritis process after enteric (enteroarthritis) or urogenital (uroarthritis) infection. Conventional antirheumatic therapeutic modalities based on nonsteroid anti-inflammatory drugs, sulfasalazine, and steroids are effective in the majority of patients. In more refractory cases, the use of second-line agents including methotrexate and more recently biological agents such as etanercept and infliximab has been found highly effective. The role of antibiotics remains not well established, although they appear to be effective in acute ReA of urogenital origin.

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.

Chlamydia trachomatis genes whose products are related to energy metabolism are expressed differentially in active vs. persistent infection

The Chlamydia trachomatis genome encodes glycolysis and pentose phosphate pathway enzymes, two ATP/ADP exchange proteins, and other energy transduction-related components. We asked if and when chlamydial genes specifying products related to energy transduction are expressed during active vs. persistent infection in in vitro models and in synovia from Chlamydia-associated arthritis patients. Hep-2 cells infected with K serovar were harvested from 0-48 h post-infection (active infection). Human monocytes identically infected were harvested at 1, 2, 3, 5 days post-infection (persistent). RNA from each preparation and from synovial samples PCR-positive/-negative for Chlamydia DNA was subjected to RT-PCR targeting (a) chlamydial primary rRNA transcripts and adt1 mRNA, (b) chlamydial mRNA encoding enzymes of the glycolysis (pyk, gap, pgk) and pentose phosphate (gnd, tal) pathways, the TCA cycle (mdhC, fumC), electron transport system (cydA, cydB), and sigma factors (rpoD, rpsD, rpoN). Primary rRNA transcripts and adt1 mRNA were present in each infected preparation and patient sample; controls were negative for chlamydial RNA. In infected Hep-2 cells, all energy transduction-related genes were expressed by approximately 11 h post-infection. In monocytes, pyk, gap, pgk, gnd, tal, cydA mRNA were present in 1-2-day-infected cells but absent at 3 days and after; cydB, mdhC, fumC were expressed through 5 days post-infection. RT-PCR targeting mRNA from sigma factor genes indicated that lack of these gene products cannot explain selective transcriptional down-regulation during persistence. Analyses of RNA from synovial tissues mirrored those from the monocyte system. These data suggest that in the first phase of active chlamydial infection, ADP/ATP exchange provides energy required for metabolism; in active growth, glycolysis supplements host ATP. In persistence host, rather than bacterially produced, ATP is the primary energy source. Metabolic rate in persistent C. trachomatis is lower than in actively growing cells, as judged from assays for relative chlamydial primary rRNA transcript levels in persistent vs. actively growing cells.