Bacterial components in the synovial tissue of patients with advanced rheumatoid arthritis or osteoarthritis: analysis with gas chromatography-mass spectrometry and pan-bacterial polymerase chain reaction

Role of IFN-α in Rheumatoid Arthritis

PURPOSE OF REVIEW

Type 1 interferons (IFN-I) are of increasing interest across a wide range of autoimmune rheumatic diseases. Historically, research into their role in rheumatoid arthritis (RA) has been relatively neglected, but recent work continues to highlight a potential contribution to RA pathophysiology.

RECENT FINDINGS

We emphasise the importance of disease stage when examining IFN-I in RA and provide an overview on how IFN-I may have a direct role on a variety of relevant cellular functions. We explore how clinical trajectory may be influenced by increased IFN-I signalling, and also, the limitations of scores composed of interferon response genes. Relevant environmental triggers and inheritable RA genetic risk relating to IFN-I signalling are explored with emphasis on intriguing data potentially linking IFN-I exposure, epigenetic changes, and disease relevant processes. Whilst these data cumulatively illustrate a likely role for IFN-I in RA, they also highlight the knowledge gaps, particularly in populations at risk for RA, and suggest directions for future research to both better understand IFN-I biology and inform targeted therapeutic strategies.

Diagnosis and Treatment of Culture-Negative Periprosthetic Joint Infection

Identification of the causative organism(s) in periprosthetic joint infection (PJI) is a challenging task. The shortcomings of traditional cultures have been emphasized in recent literature, culminating in a clinical entity known as "culture-negative PJI." Amidst the growing burden of biofilm infections that are inherently difficult to culture, the field of clinical microbiology has seen a paradigm shift from culture-based to molecular-based methods. These novel techniques hold much promise in the demystification of culture-negative PJI and revolutionization of the microbiology laboratory. This article outlines the clinical implications of culture-negative PJI, common causes of this diagnostic conundrum, established strategies to improve culture yield, and newer molecular techniques to detect infectious organisms.

Acute monoarthritis in young children: comparing the characteristics of patients with juvenile idiopathic arthritis versus septic and undifferentiated arthritis

Acute arthritis is a common cause of consultation in pediatric emergency wards. Arthritis can be caused by juvenile idiopathic arthritis (JIA), septic (SA) or remain undetermined (UA). In young children, SA is mainly caused by Kingella kingae (KK), a hard to grow bacteria leading generally to a mild clinical and biological form of SA. An early accurate diagnosis between KK-SA and early-onset JIA is essential to provide appropriate treatment and follow-up. The aim of this work was to compare clinical and biological characteristics, length of hospital stays, duration of intravenous (IV) antibiotics exposure and use of invasive surgical management of patients under 6 years of age hospitalized for acute monoarthritis with a final diagnosis of JIA, SA or UA. We retrospectively analyzed data from < 6-year-old children, hospitalized at a French tertiary center for acute mono-arthritis, who underwent a joint aspiration. Non-parametric tests were performed to compare children with JIA, SA or UA. Bonferroni correction for multiple comparisons was applied with threshold for significance at 0.025. Among the 196 included patients, 110 (56.1%) had SA, 20 (10.2%) had JIA and 66 (33.7%) had UA. Patients with JIA were older when compared to SA (2.7 years [1.8–3.6] versus 1.4 [1.1–2.1], p < 0.001). Presence of fever was not different between JIA and SA or UA. White blood cells in serum were lower in JIA (11.2 × 10⁹/L [10–13.6]) when compared to SA (13.2 × 10⁹/L [11–16.6]), p = 0.01. In synovial fluid leucocytes were higher in SA 105.5 × 10³ cells/mm³ [46–211] compared to JIA and UA (42 × 10³ cells/mm³ [6.4–59.2] and 7.29 × 10³ cells/mm³ [2.1–72] respectively), p < 0.001. Intravenous antibiotics were administered to 95% of children with JIA, 100% of patients with SA, and 95.4% of UA. Arthrotomy-lavage was performed in 66.7% of patients with JIA, 79.6% of patients with SA, and 71.1% of patients with UA. In children less than 6 years of age with acute mono-arthritis, the clinical and biological parameters currently used do not reliably differentiate between JIA, AS and UA. JIA subgroups that present a diagnostic problem at the onset of monoarthritis before the age of 6 years, are oligoarticular JIA and systemic JIA with hip arthritis. The development of new biomarkers will be required to distinguish JIA and AS caused by Kingellakingae in these patients.

Think Twice before Prescribing Antibiotics for That Swollen Knee: The Influence of Antibiotics on the Diagnosis of Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is a rare but devastating complication after total joint arthroplasty. An estimated 7-12% of patients have negative cultures despite clear clinical evidence of infection. One oft-cited reason for this occurrence is the administration of antibiotics in the weeks prior to obtaining cultures. This article reviews the influence of antibiotics on the diagnosis of PJI. Specifically, we examine the effect of prophylactic and therapeutic antibiotic administration on the diagnostic accuracy of microbiological cultures as well as serum and synovial biomarkers. We also explore the potential of molecular techniques in overcoming these limitations in patients who have received antibiotics before specimen collection and propose areas for future research.

Bacterial citrullinated epitopes generated by Porphyromonas gingivalis infection-a missing link for ACPA production

OBJECTIVES

Porphyromonas gingivalis (P.g.) is discussed to be involved in triggering self-reactive immune responses. The aim of this study was to investigate the autocitrullinated prokaryotic peptidylarginine deiminase (PPAD) from P.g. CH2007 (RACH2007-PPAD) from a rheumatoid arthritis (RA) patient and a synthetic citrullinated PPAD peptide (CPP) containing the main autocitrullination site as potential targets for antibody reactivity in RA and to analyse the possibility of citrullinating native human proteins by PPAD in the context of RA.

METHODS

Recombinant RACH2007-PPAD was cloned and expressed in Escherichia coli. Purified RACH2007-PPAD and its enzymatic activity was analysed using two-dimensional electrophoresis, mass spectrometry, immunoblot and ELISA. Autoantibody response to different modified proteins and peptides was recorded and bioinformatically evaluated.

RESULTS

RACH2007-PPAD was capable to citrullinate major RA autoantigens, such as fibrinogen, vimentin, hnRNP-A2/B1, histone H1 and multiple peptides, which identify a common RG/RGG consensus motif. 33% of RA patients (n=30) revealed increased reactivity for α-cit-RACH2007-PPAD before RA onset. 77% of RA patients (n=99) presented α-cit-specific signals to CPP amino acids 57-71 which were positively correlated to α-CCP2 antibody levels. Interestingly, 48% of the α-CPP-positives were rheumatoidfactor IgM/anti-citrullinated peptide/protein antibodies (ACPA)-negative. Anti-CPP and α-RACH2007-PPAD antibody levels increase with age. Protein macroarrays that were citrullinated by RACH2007-PPAD and screened with RA patient sera (n=6) and controls (n=4) uncovered 16 RACH2007-PPAD citrullinated RA autoantigens and 9 autoantigens associated with lung diseases. We showed that the α-CPP response could be an important determinant in parenchymal changes in the lung at the time of RA diagnosis (n=106; p=0.018).

CONCLUSIONS

RACH2007-PPAD induced internal citrullination of major RA autoantigens. Anti-RACH2007-PPAD correlates with ACPA levels and interstitial lung disease autoantigen reactivity, supporting an infection-based concept for induction of ACPAs via enzymatic mimicry.

Infectious Triggers in Periodontitis and the Gut in Rheumatoid Arthritis (RA): A Complex Story About Association and Causality

Rheumatoid arthritis (RA) is a systemic immune mediated inflammatory disease of unknown origin, which is predominantly affecting the joints. Antibodies against citrullinated peptides are a rather specific immunological hallmark of this heterogeneous entity. Furthermore, certain sequences of the third hypervariable region of human leukocyte antigen (HLA)-DR class II major histocompatibility (MHC) molecules, the so called "shared epitope" sequences, appear to promote autoantibody positive types of RA. However, MHC-II molecule and other genetic associations with RA could not be linked to immune responses against specific citrullinated peptides, nor do genetic factors fully explain the origin of RA. Consequently, non-genetic factors must play an important role in the complex interaction of endogenous and exogenous disease factors. Tobacco smoking was the first environmental factor that was associated with onset and severity of RA. Notably, smoking is also an established risk factor for oral diseases. Furthermore, smoking is associated with extra-articular RA manifestations such as interstitial lung disease in anatomical proximity to the airway mucosa, but also with subcutaneous rheumatoid nodules. In the mouth, Porphyromonas gingivalis is a periodontal pathogen with unique citrullinating capacity of foreign microbial antigens as well as candidate RA autoantigens. Although the original hypothesis that this single pathogen is causative for RA remained unproven, epidemiological as well as experimental evidence linking periodontitis (PD) with RA is rapidly accumulating. Other periopathogens such as Aggregatibacter actinomycetemcomitans and Prevotella intermedia were also proposed to play a specific immunodominant role in context of RA. However, demonstration of T cell reactivity against citrullinated, MHC-II presented autoantigens from RA synovium coinciding with immunity against Prevotella copri (Pc.), a gut microbe attracted attention to another mucosal site, the intestine. Pc. was accumulated in the feces of clinically healthy subjects with citrulline directed immune responses and was correlated with RA onset. In conclusion, we retrieved more than one line of evidence for mucosal sites and different microbial taxa to be potentially involved in the development of RA. This review gives an overview of infectious agents and mucosal pathologies, and discusses the current evidence for causality between different exogenous or mucosal factors and systemic inflammation in RA.

Synovial tissue transcriptomes of long-standing rheumatoid arthritis are dominated by activated macrophages that reflect microbial stimulation

Advances in microbiome research suggest involvement in chronic inflammatory diseases such as rheumatoid arthritis (RA). Searching for initial trigger(s) in RA, we compared transcriptome profiles of highly inflamed RA synovial tissue (RA-ST) and osteoarthritis (OA)-ST with 182 selected reference transcriptomes of defined cell types and their activation by exogenous (microbial) and endogenous inflammatory stimuli. Screening for dominant changes in RA-ST demonstrated activation of monocytes/macrophages with gene-patterns induced by bacterial and fungal triggers. Gene-patterns of activated B- or T-cells in RA-ST reflected a response to activated monocytes/macrophages rather than inducing their activation. In contrast, OA-ST was dominated by gene-patterns of non-activated macrophages and fibroblasts. The difference between RA and OA was more prominent in transcripts of secreted proteins and was confirmed by protein quantification in synovial fluid (SF) and serum. In total, 24 proteins of activated cells were confirmed in RA-SF compared to OA-SF and some like CXCL13, CCL18, S100A8/A9, sCD14, LBP reflected this increase even in RA serum. Consequently, pathogen-like response patterns in RA suggest that direct microbial influences exist. This challenges the current concept of autoimmunity and immunosuppressive treatment and advocates new diagnostic and therapeutic strategies that consider microbial persistence as important trigger(s) in the etiopathogenesis of RA.

The etiology of rheumatoid arthritis

Rheumatoid arthritis is a heterogeneous disease, which can be, based on data combining genetic risk factors and autoantibodies, sub-classified into ACPA-positive and -negative RA. Presence of ACPA and RF as well as rising CRP-levels in some patients years before onset of clinical symptoms indicate that relevant immune responses for RA development are initiated very early. ACPA are highly specific for RA, whereas RF can also be found among healthy (elderly) individuals and patients with other autoimmune diseases or infection. The most important genetic risk factor for RA development, the shared epitope alleles, resides in the MHC class II region. Shared epitope alleles, however, only predispose to the development of ACPA-positive RA. Smoking is thus far the most important environmental risk factor associated with the development of RA. Studies on synovitis have shown the importance not only of adaptive but also of innate immune responses. In summary of the various results from immunological changes in blood and synovial tissue, the extension of the immune response from a diffuse myeloid to a lympho-myeloid inflammation appears to be associated with a more successful therapeutic response to biologics. With respect to advances in synovitis research, new targets for treatment against pathological subsets of immune cells or fibroblasts are already on the horizon. However, alternative strategies involving the microbiome may play an important role as well and research in this field is growing rapidly.

Detection of Shigella spp. nucleic acids in the synovial tissue of Tunisian rheumatoid arthritis patients and other forms of arthritis by quantitative real-time polymerase chain reaction

Enterobacterial components in the joints of patients are believed to contribute to a perpetuating inflammation leading to a reactive arthritis (ReA), a condition in which microbial agents cannot be recovered from the joint. At present, it is unclear whether nucleic acids from Shigella spp. are playing a pathogenic role in causing not only ReA but also other forms of arthritis. Quantitative real-time polymerase chain reaction assay (qPCR) is the method of choice for the identification of bacteria within the synovium. The aim of our study was to detect the presence of Shigella spp. nucleic acids in the synovial tissue (ST) of Tunisian arthritis patients. We investigated 57 ST samples from rheumatoid arthritis (RA) n = 38, undifferentiated oligoarthritis (UOA) n = 12, and spondyloarthritis (SpA) n = 7 patients; 5 ST samples from healthy individuals were used as controls. Shigella spp. DNA and mRNA transcripts encoding the virulence gene A (VirA) were examined using an optimized qPCR with newly designed primers and probes. Using qPCR, Shigella spp. DNA was found in 37/57 (65%) ST samples (24/38, i.e., 63.2% of RA, 8/12, i.e., 67% of UOA, and 5/7, i.e., 71.4% of SpA patients). Paired DNA and mRNA were extracted from 39 ST samples, whose VirA cDNA was found in 29/39 (74.4%) patients. qPCR did not yield any nucleic acids in the five healthy control ST samples. The qPCR assay was sensitive and showed a good intra- and inter-run reproducibility. These preliminary findings generated by an optimized, highly sensitive PCR assay underline a potential role of past gastrointestinal infections. In Tunisian patients, a bacterial etiology involving Shigella spp. in the manifestation of arthritic disorders including RA might be more common than expected.

Does the buck stop with the bugs?: an overview of microbial dysbiosis in rheumatoid arthritis

The human body is an environmental niche which is home to diverse co-habiting microbes collectively referred as the human microbiome. Recent years have seen the in-depth characterization of the human microbiome and associations with diseases. Linking of the composition or number of the human microbiota with diseases and traits date back to the original work of Elie Metchnikoff. Recent advances in genomic technologies have opened up finer details and dynamics of this new science with higher precision. Microbe-rheumatoid arthritis connection, largely related to the gut and oral microbiomes, has showed up as a result - apart from several other earlier, well-studied candidate autoimmune diseases. Although evidence favouring roles of specific microbial species, including Porphyromonas, Prevotella and Leptotricha, has become clearer, mechanistic insights still continue to be enigmatic. Manipulating the microbes by traditional dietary modifications, probiotics, and antibiotics and by currently employed disease-modifying agents seems to modulate the disease process and its progression. In the present review, we appraise the existing information as well as the gaps in knowledge in this challenging field. We also discuss the future directions for potential clinical applications, including prevention and management of rheumatoid arthritis using microbial modifications.

Do genetic susceptibility, Toll-like receptors, and pathogen-associated molecular patterns modulate the effects of wear?

Overwhelming evidence supports the concept that wear particles are the primary initiator of aseptic loosening of orthopaedic implants. It is likely, however, that other factors modulate the biologic response to wear particles. This review focuses on three potential other factors: genetic susceptibility, Toll-like receptors (TLRs), and bacterial pathogen-associated molecular patterns (PAMPs). WHERE ARE WE NOW?: Considerable evidence is emerging that both genetic susceptibility and TLR activation are important factors that modulate the biologic response to wear particles, but it remains controversial whether bacterial PAMPs also do so. WHERE DO WE NEED TO GO?: Detailed understanding of the roles of these other factors may lead to identification of novel therapeutic targets for patients with aseptic loosening. HOW DO WE GET THERE?: Highest priority should be given to polymorphism replication studies with large numbers of patients and studies to replicate the reported correlation between bacterial biofilms and the severity of aseptic loosening.

A case of erosive polyarthritis in a patient diagnosed with a suspicion of atypical mycobacteria

In this report, we introduce a case of erosive polyarthritis in a 55-year-old female diagnosed with Mycobacterium abscessus pulmonary infection. Her arthritis has been worsened after use of DMARDs. The patient demonstrated a significant response to the antimicrobial regimen that was administered. We call special attention to the possibility of Mycobacterium abscessus being a cause of reactive polyarthritis, particularly if symptoms worsened after use of disease-modifying antirheumatic drugs (DMARDs), but further studies are necessary for clarification.

Microbial Infection and Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a complex autoimmune disease affecting 1–2% of general worldwide population. The etiopathogenesis of RA involves the interplay of multiple genetic risk factors and environmental triggers. Microbial infections are believed to play an important role in the initiation and perpetuation of RA. Recent clinical studies have shown the association of microbial infections with RA. Accumulated studies using animal models have also found that microbial infections can induce and/or exaggerate the symptoms of experimental arthritis. In this review, we have identified the most common microbial infections associated with RA in the literature and summarized the current evidence supporting their pathogenic role in RA. We also discussed the potential mechanisms whereby infection may promote the development of RA, such as generation of neo-autoantigens, induction of loss of tolerance by molecular mimicry, and bystander activation of the immune system.

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.

Toll-like receptors: a new target in rheumatoid arthritis?

Rheumatoid arthritis (RA) is one of the most prevalent autoimmune diseases. It is characterized by chronic inflammation of the joint leading to its destruction. Although the initiating cause remains elusive, environmental factors and genetic background are known to contribute to the etiology of RA. The role of Toll-like receptors (TLRs) in innate immunity and their ability to recognize microbial products has been well characterized. TLRs are able to recognize endogenous molecules released upon cell damage and necrosis, and are present in RA synovial fluid. Although it appears unlikely that a pathogen underlies the pathogenesis or progression of RA, the release of endogenous TLR ligands during inflammation may activate TLRs and perpetuate the disease. An increasing body of circumstantial evidence implicates TLR signaling in RA, although, at present, their involvement is not defined comprehensively. Targeting individual TLRs or their signaling transducers may provide a more specific therapy without global suppression of the immune system.

[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.

Rheumatoid arthritis is linked to Proteus--the evidence

Rheumatoid arthritis (RA) is a chronic inflammatory arthritic and potentially disabling condition, mainly affecting women of middle age and having characteristic clinical features. Various microbial agents were implicated in the causation of RA. Extensive literature based on the results of various genetic, microbiological, molecular, and immunological studies carried out by independent research groups supports the role of Proteus mirabilis bacteria in the etiopathogenesis of RA. New diagnostic markers and criteria and the use of a novel therapeutic protocol in the form of antibiotic and dietary measures are suggested to be used together with current treatments in the management of RA. Prospective longitudinal studies with the use of antimicrobial measures in patients with RA are required to establish the therapeutic benefit of this microbe-disease association.

Development of a broad-range 16S rDNA real-time PCR for the diagnosis of septic arthritis in children

The broad-range PCR has been successfully developed to search for fastidious, slow-growing or uncultured bacteria, and is mostly used when an empirical antibiotic treatment has already been initiated. The technique generally involves standard PCR targeting the gene coding for 16S ribosomal RNA, and includes a post-PCR visualisation step on agarose gel which is a potential source of cross-over contamination. In addition, interpretation of the presence of amplified products on gels can be difficult. We then developed a new SYBR Green-based, universal real-time PCR assay targeting the gene coding for 16S ribosomal RNA, coupled with sequencing of amplified products. The real-time PCR assay was evaluated on 94 articular fluid samples collected from children hospitalised for suspicion of septic arthritis, as compared to the results obtained with bacterial cultures and conventional broad-range PCR. DNA extraction was performed with the automated MagNa Pure system. We could detect DNA from various bacterial pathogens including fastidious bacteria (Kingella kingae, Streptococcus pneumoniae, Streptococcus pyogenes, Salmonella spp, Staphylococcus aureus) from 23% of cases of septic arthritis giving negative culture results. The real-time technique was easier to interpret and allowed to detect four more cases than conventional PCR. PCR based molecular techniques appear to be essential to perform in case of suspicion of septic arthritis, provided the increase of the diagnosed bacterial etiologies. Real-time PCR technique is a sensitive and reliable technique, which can replace conventional PCR for clinical specimens with negative bacterial culture.

Mechanisms of disease: infection and spondyloarthritis

There is compelling evidence that some infections can initiate a chronic nonseptic arthritis. This has proved to be an important area of investigation into gene-environment interactions, particularly since HLA-B27 confers increased susceptibility to reactive arthritis. This research has investigated the microbiology of these events, and the strategies used by pathogens to induce chronic joint inflammation. Insights into the HLA-orchestrated immune response in this context have also shed light on the impact of HLA-B27 on immunity, which might provide insights into the mechanism of other HLA-B27-associated diseases. Despite the genetic link to reactive arthritis, there is no proven relationship between ankylosing spondylitis and an inciting infection. In general, most trials have found antibiotics to be ineffective in modifying the course of spondyloarthritis.

Data reduction in headspace analysis of blood and urine samples for robust bacterial identification

This paper demonstrates the application of chemical headspace analysis to the problem of classifying the presence of bacteria in biomedical samples by using computational tools. Blood and urine samples of disparate forms were analysed using a Cyrano Sciences C320 electronic nose together with an Agilent 4440 Chemosensor. The high dimensional data sets resulting from these devices present computational problems for parameter estimation of discriminant models. A variety of data reduction and pattern recognition techniques were employed in an attempt to optimise the classification process. A 100% successful classification rate for the blood data from the Agilent 4440 was achieved by combining a Sammon mapping with a radial basis function neural network. In comparison a successful classification rate of 80% was achieved for the urine data from the C320 which were analysed using a novel nonlinear time series model.

Pathogenesis of ankylosing spondylitis and reactive arthritis

PURPOSE OF REVIEW

The hallmark of ankylosing spondylitis is acute and chronic spinal inflammation initiating in the sacroiliac joints, often coupled with enthesitis, presenting as chronic inflammation at the sites of ligamentous and tendinous insertions into bone. Peripheral joint synovitis can be a prominent feature as well. Reactive arthritis is a sterile synovitis arising after an extra-articular infection of enteric or urogenital tracts. HLA-B27 has been known for about the past 30 years to be associated with ankylosing spondylitis and reactive arthritis, but the pathogenesis of ankylosing spondylitis and reactive arthritis is still not well defined. Although the clinical manifestations of ankylosing spondylitis and reactive arthritis may differ, this update discusses the two diseases together and focuses on recent evidence in both.

RECENT FINDINGS

With respect to HLA-B27 several recent studies address arthritogenic peptides, molecular mimicry, and aberrant forms of B27. Several candidate genes in addition to B27 have been implicated in recent genetic studies. With respect to bacterial infection, recent findings in bacterial antigenicity, host response through interactions of antigen-presenting cells, T cells, and cytokines are providing new understanding of host-pathogen interactions and the pathogenesis of arthritis. Endogenous host factors such as proteoglycans may play a role as autoantigens and contribute to chronic inflammation on that basis.

SUMMARY

Recent advances provide additional new insights into distinct pathogenetic mechanisms in AS and ReA that arise from a complex interplay between genetic factors including HLA-B27 and environmental factors.

Demonstration by PCR and DNA sequencing of Corynebacterium pseudodiphtheriticum as a cause of joint infection and isolation of the same organism from a surface swab specimen from the patient

A case of infectious arthritis following arthroscopy is described. Real-time PCR, using universal bacterial primers targeting the 16S rRNA gene, and subsequent DNA sequencing of the PCR product demonstrated the presence of DNA from Corynebacterium pseudodiphtheriticum in the synovial fluid from the affected knee. Culture from a surface swab from the site of purulent discharge from the knee was initially reported as growing normal skin microbiota. Knowing the result of the DNA analysis, the specimen was re-examined and a diphtheroid bacterium was isolated. The DNA sequence of the isolated bacterium was identical to that of the DNA in the joint. The isolated bacterium was tested for susceptibility to relevant antibiotics. Demonstration and identification of bacterial DNA by PCR and gene sequencing may not by itself give information on important characteristics such as susceptibility to antibiotics of the infecting bacterium. The present case illustrates that the results obtained by the method can be used to isolate the relevant bacterium in culture from other sites and thereby characterize it. It furthermore demonstrates that C. pseudodiphtheriticum can cause severe arthritis when inoculated into joints.

MMP-3 expression and release by rheumatoid arthritis fibroblast-like synoviocytes induced with a bacterial ligand of integrin alpha5beta1

Fibroblast-like synoviocytes (FLSs) play a major role in the pathogenesis of rheumatoid arthritis (RA) by secreting effector molecules that promote inflammation and joint destruction. How these cells become and remain activated is still elusive. Both genetic and environmental factors probably play a role in transforming FLSs into inflammatory matrix-degrading cells. As bacterial products have been detected in the joint and shown to trigger joint inflammation, this study was undertaken to investigate whether a bacterial ligand of integrin alpha5beta1, protein I/II, could contribute to the aggressive behavior of RA FLSs. Protein I/II is a pathogen-associated molecular pattern (PAMP) isolated from oral streptococci that have been identified in the joints of RA patients. The response of RA and osteoarthritis FLSs to protein I/II was analyzed using human cancer cDNA expression arrays. RT-PCR and pro-MMP-3 (pro-matrix metalloproteinase) assays were then performed to confirm the up-regulation of gene expression. Protein I/II modulated about 6% of all profiled genes. Three of these, those encoding IL-6, leukemia inhibitory factor, and MMP-3, showed a high expression level in all RA FLSs tested, whereas the expression of genes encoding other members of the cytokine or MMP-family was not affected. Furthermore, the up-regulation of MMP-3 gene expression was followed by an increase of pro-MMP-3 release. The expression of interferon regulatory factor 1 and fibroblast growth factor-5 was also up-regulated, although the expression levels were lower. Only one gene, that for insulin-like growth factor binding protein-4, was down-regulated in all RA FLSs. In contrast, in osteoarthritis FLSs only one gene, that for IL-6, was modulated. These results suggest that a bacterial ligand of integrin alpha5beta1 may contribute to the aggressive behavior of RA FLSs by inducing the release of pro-inflammatory cytokines and a cartilage-degrading enzyme, such as IL-6 and MMP-3, respectively.

Rheumatoid factor revisited

PURPOSE OF REVIEW

Initial studies of the pathogenesis of rheumatoid arthritis focused on the role of rheumatoid factor and immune complex-associated vasculitis and synovitis. Subsequent work has delineated T cell responses, the role of cytokines, chemokines, and the aggressive nature of rheumatoid synovitis. Recent findings underscore the importance of humoral immunity in this entity and are the subject of this review.

RECENT FINDINGS

By the discovery of anti-cyclic citrullinated peptide, anti-RA33, and anti-GPI antibodies in the human and mouse systems, respectively, the impact of humoral autoimmunity in rheumatoid arthritis regained remarkable interest. This review summarizes recent insights into humoral autoimmunity in rheumatoid arthritis in the context of the generation of rheumatoid factors, including B cell activation via toll-like receptors and genetic predispositions that can trigger the induction of rheumatoid arthritis. The generation of rheumatoid factors that can also be found during host defense against infectious agents and under pathologic conditions, such as rheumatoid arthritis, Sjögren syndrome, and hepatitis C-associated mixed cryoglobulinemia after hepatitis C infection is likely the result of genetic predispositions and the intensity of the (primary) immune reaction. Models of the role of rheumatoid factors in health and disease, including related lymphomagenesis, will be discussed.

SUMMARY

In patients with rheumatoid arthritis, the induction of rheumatoid factors can be taken as an indicator of severe disease with a striking involvement of B cell activation. Very recent clinical trials using B cell depletion support the concept that humoral immunity, as evidenced by the production of rheumatoid factors, plays a significant role in the course of the disease.

Normal intestinal microbiota in the aetiopathogenesis of rheumatoid arthritis

A series of observations have led to the hypothesis that normal intestinal microbiota in patients with rheumatoid arthritis may harbour, for genetic reasons, bacteria with cell walls capable of inducing arthritis. Differences occur between bacterial species, and even between strains of a single species, because some cell walls induce experimental chronic arthritis, whereas some others induce only a transient acute arthritis or no arthritis at all. In susceptible subjects, with continuous seeding of bacterial products from the gut, the synovial inflammation is followed by erosion, exposition of cartilage antigens, and self perpetuating chronic arthritis.