Yersinia-triggered reactive arthritis. Use of polymerase chain reaction and immunocytochemical staining in the detection of bacterial components from synovial specimens

The menace within: bacterial amyloids as a trigger for autoimmune and neurodegenerative diseases

Bacteria are known to produce amyloids, proteins characterized by a conserved cross-beta sheet structure, which exhibit structural and functional similarities to human amyloids. The deposition of human amyloids into fibrillar plaques within organs is closely linked to several debilitating human diseases, including Alzheimer's and Parkinson's disease. Recently, bacterial amyloids have garnered significant attention as potential initiators of human amyloid-associated diseases as well as autoimmune diseases. This review aims to explore how bacterial amyloid, particularly curli found in gut biofilms, can act as a trigger for neurodegenerative and autoimmune diseases. We will elucidate three primary mechanisms through which bacterial amyloids exert their influence: By delving into these three distinct modes of action, this review will provide valuable insights into the intricate relationship between bacterial amyloids and the onset or progression of neurodegenerative and autoimmune diseases. A comprehensive understanding of these mechanisms may open new avenues for therapeutic interventions and preventive strategies targeting amyloid-associated diseases.

Infective endocarditis: Role of molecular techniques in early diagnosis

Infective endocarditis (IE), a heart valve infection primarily caused by bacteria such as streptococci or staphylococci, causes significant morbidity and mortality. Despite the long-term use of broad-spectrum antimicrobials, the infection is often difficult to manage. The latest diagnostic modalities for IE are discussed in this study. Blood culture use in pathogen identification can lead to loss of precious time as well as generation of false negative reports. The first steps in diagnosis are blood cultures and echocardiography, but molecular techniques can be extremely useful and may be used for an accurate and early diagnosis.

Microbiome or Infections: Amyloid-Containing Biofilms as a Trigger for Complex Human Diseases

The human microbiota is the community of microorganisms that live upon or within their human host. The microbiota consists of various microorganisms including bacteria, fungi, viruses, and archaea; the gut microbiota is comprised mostly of bacteria. Many bacterial species within the gut microbiome grow as biofilms, which are multicellular communities embedded in an extracellular matrix. Studies have shown that the relative abundances of bacterial species, and therefore biofilms and bacterial byproducts, change during progression of a variety of human diseases including gastrointestinal, autoimmune, neurodegenerative, and cancer. Studies have shown the location and proximity of the biofilms within the gastrointestinal tract might impact disease outcome. Gram-negative enteric bacteria secrete the amyloid curli, which makes up as much as 85% of the extracellular matrix of enteric biofilms. Curli mediates cell-cell attachment and attachment to various surfaces including extracellular matrix components such as fibronectin and laminin. Structurally, curli is strikingly similar to pathological and immunomodulatory human amyloids such as amyloid-β, which has been implicated in Alzheimer's disease, α-synuclein, which is involved in Parkinson's disease, and serum amyloid A, which is secreted during the acute phase of inflammation. The immune system recognizes both bacterial amyloid curli and human amyloids utilizing the same receptors, so curli also induces inflammation. Moreover, recent work indicates that curli can participate in the self-assembly process of pathological human amyloids. Curli is found within biofilms of commensal enteric bacteria as well as invasive pathogens; therefore, evidence suggests that curli contributes to complex human diseases. In this review, we summarize the recent findings on how bacterial biofilms containing curli participate in the pathological and immunological processes in gastrointestinal diseases, systemic autoimmune diseases, and neurodegenerative diseases.

Bacterial Amyloids: The Link between Bacterial Infections and Autoimmunity

Molecular mimicry is a common mechanism used by many bacteria to evade immune responses. In recent years, it has become evident that bacteria also decorate the extracellular matrix (ECM) of their biofilms with molecules that resemble those of the host. These molecules include amyloids and other proteins, polysaccharides, and extracellular DNA. Bacterial amyloids, like curli, and extracellular DNA are found in the biofilms of many species. Recent work demonstrated that curli and DNA form unique molecular structures that are recognized by the immune system, causing activation of autoimmune pathways. Although a variety of mechanisms have been suggested as the means by which infections initiate and/or exacerbate autoimmune diseases, the mechanism remains unknown. In this article, we discuss recent work on biofilms that highlight the role of amyloids as a carrier for DNA and potentiator of autoimmune responses, and we propose a novel link between bacterial infections and autoimmune diseases.

Effects of aeration on microbes and intestinal bacteria in bioaerosols from the BRT of an indoor wastewater treatment facility

The generation and emission of airborne bacteria from a biochemical reaction tank (BRT) for wastewater treatment was investigated by altering the aeration rate. The levels of bioaerosols increased from 715 ± 69 to 1597 ± 135 CFU/m³ (total airborne bacteria) and from 78 ± 6 to 359 ± 18 CFU/m³ (intestinal bacteria) as the aeration rate increased from 0.3 to 1.2 m³/h. Most airborne bacteria were attached to particles smaller than 4.7 μm at an aeration rate of 0.3 m³/h. They were found attached to larger particles (>4.7 μm) when the aeration rate increased to 1.2 m³/h. A similar phenomenon was observed for intestinal bacteria. The high-throughput sequencing technique was used to assay the microbial populations of the bioaerosols. Both microbial counts and diversity increased as the aeration rate increased. Brevundimonas (63.82%), Chryseobacterium (16.54%), and Micrococcaceae (12.37%) were the dominant intestinal bacteria at an aeration rate of 0.3 m³/h. Pseudochrobactrum (33.10%), Citrobacter (21.28%), and Yersinia (18.21%) were the dominant intestinal bacteria at an aeration rate of 1.2 m³/h. The level, particle size distribution, population structure, and diversity of the bioaerosols were all affected by aeration rate. The source tracker results indicated that water and the surrounding air were the two main bioaerosol sources. The contribution of water is greater at larger levels of aeration. Inhalation was the main pathway of microbial aerosol intake for people in the surrounding area. The exposure hazard quotients for adult males were generally higher than those for adult females. Necessary measures should be taken to ensure worker safety.

Utility of a Direct 16S rDNA PCR and Sequencing for Etiological Diagnosis of Infective Endocarditis

Background

Cases of infective endocarditis (IE) require prompt etiological diagnosis for effective treatment. Molecular methods can aid in rapid and reliable diagnosis of culture-negative IE cases. We evaluated the utility of 16S rDNA PCR and sequencing in determining the causative agents of IE in valve tissues, especially when specimens were obtained after initiation of antimicrobial therapy.

Methods

We performed 16S rDNA PCR and sequencing in heart valve specimens and medical records review of 80 patients who underwent protocol-based cardiac surgery from 2013 to 2015. One patient did not meet the criteria for IE. Sixty-five (81.3%) and 14 pa-tients (17.5%) were diagnosed as having definite IE and possible IE, respectively. Blood and heart valve biopsy tissue were examined by using routine microbiological methods.

Results

Blood cultures in our hospital were IE-positive for 33 patients (41.8%), whereas 49 patients (62.0%) showed positive blood cultures when initial blood cultures performed at the referring hospital were included. Eighteen (22.8%) and 40 patients (50.6%) were IE-positive in valve tissue cultures and 16S rDNA PCR, respectively. Bacteria in the Streptococcus mitis group (n=26) were the most common etiological agents of IE. Eight (10.1%) culture-negative specimens tested positive by 16S rDNA PCR. In five of eight PCR-positive and culture-negative cases, fastidious or anaerobic organisms were the cause of IE.

Conclusions

Direct 16S rDNA PCR and sequencing can be used as a supplementary method to conventional blood and biopsy culture testing, especially in culture-negative IE cases that are negative for IE by culture.

Identification of potential Tpx inhibitors against pathogen-host interactions

Yersinia organisms cause many infectious diseases by invading human cells and delivering their virulence factors via the type three secretion system (T3SS). One alternative strategy in the fight against these pathogenic organisms is to interfere with their T3SS. Previous studies demonstrated that thiol peroxidase, Tpx is functional in the assembly of T3SS and its inhibition by salicylidene acylhydrazides prevents the secretion of pathogenic effectors. In this study, the aim was to identify potential inhibitors of Tpx using an integrated approach starting with high throughput virtual screening and ending with molecular dynamics simulations of selected ligands. Virtual screening of ZINC database of 500,000 compounds via ligand-based and structure-based pharmacophore models retrieved 10,000 hits. The structure-based pharmacophore model was validated using high-throughput virtual screening (HTVS). After multistep docking (SP and XP), common scaffolds were used to find common substructures and the ligand binding poses were optimized using induced fit docking. The stability of the protein-ligand complex was examined with molecular dynamics simulations and the binding free energy of the complex was calculated. As a final outcome eight compounds with different chemotypes were proposed as potential inhibitors for Tpx. The eight ligands identified by a detailed virtual screening protocol can serve as leads in future drug design efforts against the destructive actions of pathogenic bacteria.

Reactive arthritis

Reactive arthritis (ReA) is an immune-mediated seronegative arthritis that belongs to the group of spondyloarthropathies and develops after a gastrointestinal or genitourinary system infection. The condition is considered to be characterized by a triad of symptoms (conjunctivitis, arthritis and urethritis) although a constellation of other manifestations may also be present. ReA is characterized by psoriasiform dermatological manifestations that may resemble those of pustular psoriasis and, similar to guttate psoriasis, is a post-infectious entity. Also, the articular manifestations of the disorder are similar to those of psoriatic arthritis and both conditions show a correlation with HLA-B27. These facts have led several authors to suggest that there is a connection between ReA and psoriasis, listing ReA among the disorders related to psoriasis. However, the pathogenetic mechanism behind the condition is complex and poorly understood. Bacterial antigenicity, the type of host response (i.e. Th1/Th2 imbalance) and various genetic factors (i.e. HLA-B27 etc.) play an important role in the development of the disorder. It is unknown whether all the aforementioned factors are part of a mechanism that could be similar to, or share basic aspects with known psoriasis pathogenesis mechanisms.

Antibiotics for Treatment of Reactive Arthritis: A Systematic Review and Metaanalysis

Objective.

To examine the efficacy and safety of antibiotic treatments for reactive arthritis (ReA).

Methods.

We did a systematic review and metaanalysis of randomized controlled trials of antibiotics for treatment of ReA. We searched electronic databases and conference proceedings up to November 2011. Included trials reported on remission, joint counts, and pain or patient global scores in any language.

Results.

Twelve trials were eligible for inclusion and 10 provided data for metaanalysis. The pooled relative risk of failure to achieve remission from a random effects model showed no significant benefit of antibiotic treatment on remission (7 trials, 375 participants, RR 0.74, 95% CI 0.49–1.10); however, substantial heterogeneity was observed (I2 = 76.3%, p < 0.0001). The treatment effect did not differ significantly by the type of organism triggering the ReA (chlamydia, 4 trials, RR 0.80, 95% CI 0.63–1.03, vs other microorganisms, 5 trials, RR 0.72, 95% CI 0.29–1.79, metaregression p = 0.477) or use of combination antibiotics (monotherapy, 6 trials, RR 0.70, 95% CI 0.39–1.26, vs combination therapy, 1 trial, RR 0.79, 95% CI 0.63–0.99, metaregression p = 0.466). When unblinded trials were excluded, the treatment effect was attenuated and heterogeneity decreased (RR 0.87, 95% CI 0.70–1.10, I2 = 32.8%, p = 0.19). No significant effects of antibiotic treatment were observed on joint counts, pain, or patient global scores; however, antibiotics were associated with a 97% increase in gastrointestinal adverse events.

Conclusion.

Trials of antibiotic treatment for ReA have produced heterogeneous results that may be related to differences in study design. The efficacy of antibiotics is uncertain.

Bacterial agents in spondyloarthritis: a destiny from diversity?

The spondyloarthritides (SpAs) are a group of diseases that share clinical, radiographic and laboratory features; these arthritides also display a tendency for family aggregation. Given the intimate relationship that these types of arthritis share, it suggests that the SpAs might share a common aetiology. Of all the SpAs, the role of bacteria is most clearly defined in reactive arthritis. Tremendous recent insights into the pathophysiology of reactive arthritis have been made, demonstrating that the causative bacteria play a much more complex role than previously thought. The bacteria that are proven to cause reactive arthritis, one of the five types of SpA, will be reviewed and their role in the pathophysiology of reactive arthritis will be examined. The speculative data suggesting links between various other bacteria and the other types of SpAs will be critically analysed. Although these data are not definitive, when viewed using the paradigm that the SpAs might actually represent a common end point from several diverse starting points, they are provocative, suggesting that bacteria might, indeed, be aetiological for the entire group of SpAs.

Combination antibiotics as a treatment for chronic Chlamydia-induced reactive arthritis: a double-blind, placebo-controlled, prospective trial

OBJECTIVE

Chlamydia trachomatis and Chlamydophila (Chlamydia) pneumoniae are known triggers of reactive arthritis (ReA) and exist in a persistent metabolically active infection state in the synovium, suggesting that they may be susceptible to antimicrobial agents. The goal of this study was to investigate whether a 6-month course of combination antibiotics is an effective treatment for patients with chronic Chlamydia-induced ReA.

METHODS

This study was a 9-month, prospective, double-blind, triple-placebo trial assessing a 6-month course of combination antibiotics as a treatment for Chlamydia-induced ReA. Eligible patients had to be positive for C trachomatis or C pneumoniae by polymerase chain reaction (PCR). Groups received 1) doxycycline and rifampin plus placebo instead of azithromycin; 2) azithromycin and rifampin plus placebo instead of doxycycline; or 3) placebos instead of azithromycin, doxycycline, and rifampin. The primary end point was the number of patients who improved by 20% or more in at least 4 of 6 variables without worsening in any 1 variable in both combination antibiotic groups combined and in the placebo group at month 6 compared with baseline.

RESULTS

The primary end point was achieved in 17 of 27 patients (63%) receiving combination antibiotics and in 3 of 15 patients (20%) receiving placebo. Secondary efficacy end points showed similar results. Six of 27 patients (22%) randomized to combination antibiotics believed that their disease went into complete remission during the trial, whereas no patient in the placebo arm achieved remission. Significantly more patients in the active treatment group became negative for C trachomatis or C pneumoniae by PCR at month 6. Adverse events were mild, with no significant differences between the groups.

CONCLUSION

These data suggest that a 6-month course of combination antibiotics is an effective treatment for chronic Chlamydia-induced ReA.

[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.

Reactive arthritis: clinical aspects and medical management

Reactive arthritis (ReA) is an inflammatory arthritis that arises after certain gastrointestinal or genitourinary infections, representing a classic interplay between host and environment. It belongs to the group of arthritidies known as the spondyloarthropathies. The classic syndrome is a triad of symptoms, including the urethra, conjunctiva, and synovium; however, the majority of patients do not present with this triad. Diagnostic criteria for ReA exist, but data suggest new criteria are needed. Epidemiologic and prospective studies have been difficult to perform because of over-reliance on the complete classic triad of symptoms and the different terms and eponyms used. Studies assessing various treatment strategies are ongoing.

Reactive arthritis: defined etiologies, emerging pathophysiology, and unresolved treatment

ReA is unique in that it is one of the few disease states of which there is a known trigger. This insight into disease initiation has led to great advances in the pathophysiology. Despite this detailed knowledge, the proper treatment remains elusive. In the years to come it is possible that the specific treatment will be dictated by the triggering microbe.

Aetiological diagnosis of infective endocarditis by direct amplification of rRNA genes from surgically removed valve tissue. An 11-year experience in a Finnish teaching hospital

BACKGROUND/AIMS

The aetiology of infective endocarditis (IE) can be determined directly from surgically removed valve tissue using broad-range bacterial rDNA polymerase chain reaction (PCR) followed by sequencing. We sought to assess the value of this methodology in a routine clinical setting.

METHODS

Broad-range PCR with primers targeting conserved bacterial rDNA sequences was applied to directly analyse valve samples from 56 patients operated on for diagnosed or suspected IE. Identification of the aetiological agent was performed by partial DNA sequencing of the 16S and 23S rDNA genes.

RESULTS

The final diagnosis was definite IE in 36 patients and possible IE in 2 patients, while the diagnosis of IE was rejected in 18 patients. PCR analysis from removed valve tissue was positive in 25 patients with IE. Molecular identification was consistent with the blood culture finding in 20 of these patients. The PCR approach was the only method to yield the aetiological diagnosis in additional 4 patients (2 Staphylococcus species, 1 Streptococcus bovis, 1 Bartonella quintana), all of whom had received antimicrobials before blood cultures were taken. The mean duration of preoperative antimicrobial treatment for the patients with PCR-positive valves was 19.6 (range 1-58) days.

CONCLUSIONS

Bacterial DNA may persist during treatment in infected valves for long periods. The PCR method is especially useful when the causative agent of IE is fastidious or when the specimen is taken during antimicrobial treatment.

Three month treatment of reactive arthritis with azithromycin: a EULAR double blind, placebo controlled study

OBJECTIVE

To determine the efficacy of weekly treatment with oral azithromycin for 13 weeks on the severity and resolution of reactive arthritis (ReA).

METHODS

186 patients from 12 countries were enrolled in a randomised, double blind, placebo controlled trial. Inclusion criteria were inflammatory arthritis of < or =6 swollen joints, and disease duration of < or =2 months. All patients received a single azithromycin dose (1 g) as conventional treatment for possible Chlamydia infection, and were then randomly allocated to receive weekly azithromycin or placebo. Clinical assessments were made at 4 week intervals for 24 weeks.

RESULTS

152 patients were analysable (34 failed entry criteria), with a mean (SD) age of 33.8 (9.4) and duration of symptoms 30.7 (17.5) days. Mean C reactive protein (CRP) was 48 mg/l, and approximately 50% of those typed were HLA-B27+, suggesting that the inclusion criteria successfully recruited patients with acute ReA. Treatment and placebo groups were well matched for baseline characteristics. There were no statistical differences for changes in any end point (swollen and tender joint count, joint pain, back pain, heel pain, physician and patient global assessments, and CRP) between the active treatment and placebo groups, analysed on an intention to treat basis or according to protocol completion. The time to resolution of arthritis and other symptoms or signs by life table analyses was also not significantly different. Adverse events were generally mild, but were more commonly reported in the azithromycin group.

CONCLUSIONS

This large trial has demonstrated that prolonged treatment with azithromycin is ineffective in ReA.

Do temporal arteritis lesions contain bacterial DNA?

BACKGROUND

Temporal arteritis is a primary vascular inflammatory disease. The aetiology of temporal arteritis is unknown, but the influence of environmental factors such as infections has been suggested.

MATERIALS AND METHODS

We used broad-range PCR, targeting conserved regions of the gene encoding for ribosomal RNA, to detect bacterial DNA in 27 temporal artery biopsies. Five uninvolved temporal arteries were also included. A lung sample of confirmed bacterial pneumonia served as a positive control. Inflammation was examined by histochemistry and light microscopy.

RESULTS

The sensitivity of the broad-range PCR assay was 5.0 fg of DNA. Bacterial DNA sequences were neither detected in 27 temporal arteritis specimens nor in the normal temporal artery samples. However, bacterial DNA was successfully amplified from the lung sample of a subject with pneumonia. In addition, human DNA was amplified by primers for human beta-actin from all clinical specimens, suggesting lack of significant inhibitors of the molecular amplification reaction. Histochemistry showed signs of strong inflammation in the arteritis samples.

CONCLUSIONS

The lack of detectable amounts of bacterial DNA suggests that viable bacteria do not have a role in chronic stages of temporal arteritis. However, these findings do not rule out the possibility of bacterial degradation products as stimulants of chronic inflammation, or of viable microbes as triggering factors of acute temporal arteritis.

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].

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

OBJECTIVE

To study the presence of bacterial components in the synovial tissue (ST) of patients with advanced rheumatoid arthritis (RA).

METHODS

ST was collected during joint surgery from 41 RA patients. Tissue from 39 patients with osteoarthritis (OA), 4 patients with undifferentiated inflammatory arthritis (UA), and 3 cases of accidental deaths served as controls. The pan-bacterial polymerase chain reaction (PCR) with primers for the 23S ribosomal RNA (rRNA) and 16S rRNA genes was used to detect bacterial DNA. In addition, synovial fluid (SF) samples from patients with chlamydial reactive arthritis (ReA) were also examined by the same method. The positive controls, bacterial DNA or ST spiked with different living bacteria, were analyzed alongside clinical samples. Most of the ST samples were also analyzed by gas chromatography-mass spectrometry (GC-MS) for determining the presence of bacteria-derived muramic acid. Strict precautions were followed in the clinics and the laboratory to prevent contamination.

RESULTS

In GC-MS analysis, muramic acid was observed in the ST from 4 of 35 RA patients and from 2 of 14 OA patients, but not in ST from 2 patients with UA and 3 cadavers. Bacterial DNA was not detected by either one of the PCR primers used in ST from 42 patients with RA and 39 patients with OA. However, 5 of 15 SF samples from ReA patients were PCR positive. The sensitivity of GC-MS to detect muramic acid was 2 pg/injected amount (227 pg muramic acid/mg ST), and that of the pan-bacterial PCR was 2-20 bacteria colony forming units/reaction.

CONCLUSION

These results indicate that a bacterial component, muramic acid, is detectable by GC-MS in ST from a few patients with advanced RA or OA. However, no bacterial DNA was detectable by PCR.

Aetiological diagnosis of brain abscesses and spinal infections: application of broad range bacterial polymerase chain reaction analysis

OBJECTIVE

To evaluate the usefulness of the broad range bacterial rDNA polymerase chain reaction (PCR) method combined with DNA sequencing in the aetiological diagnosis of intracranial or spinal infections in neurosurgical patients.

METHODS

In addition to conventional methods, the broad range bacterial PCR approach was applied to examine pus or tissue specimens from cerebral or spinal lesions in patients treated in a neurosurgical unit for a clinical or neuroradiological suspicion of bacterial brain abscess or spondylitis.

RESULTS

Among the 44 patients with intracranial or spinal lesions, the final diagnosis suggested bacterial disease in 25 patients, among whom the aetiological agent was identified in 17. A causative bacterial species was identified only by the rDNA PCR method in six cases, by both the PCR methodology and bacterial culture in six cases, and by bacterial culture alone in five. All samples in which a bacterial aetiology was identified only by the PCR approach were taken during antimicrobial treatment, and in three patients the method yielded the diagnosis even after >/= 12 days of parenteral treatment. One case also identified by the PCR approach alone involved a brain abscess caused by Mycoplasma hominis, which is not readily cultured by routine methods.

CONCLUSIONS

In patients with brain abscesses and spinal infections, the broad range bacterial rDNA PCR approach may be the only method to provide an aetiological diagnosis when the patient is receiving antimicrobial treatment, or when the causative agent is fastidious.

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.

Presence of parvovirus B19 DNA in chronic urticaric and healthy human skin

BACKGROUND

The etiology of chronic urticaria is undefined, but the potential role of infectious agents as one triggering factor has been suggested. The appearance of chronic urticaria in a 16-year old male after a history of a recent parvovirus B19 (B19) infection led us to investigate the association between B19 and chronic urticaria.

OBJECTIVES

To investigate whether parvovirus B19 (B19) has a role in chronic urticaria.

STUDY DESIGN

We amplified B19 DNA from skin biopsy samples of 36 adult chronic urticaria patients as well as of 22 healthy controls using two sets of separate primers and probe. Circulating IgG and IgM antibodies to B19 were measured from 27 patients and from all controls.

RESULTS

B19 DNA was detected in 18 (50%) skin biopsy samples of 36 patients with chronic urticaria. Unexpectedly, also 14 (64%) skin biopsy samples from 22 healthy controls harbored B19 DNA. All 32 persons with positive B19 PCR findings had circulating IgG-class antibodies to B19 major structural protein VP2, but no IgM antibodies.

CONCLUSION

Our results show that B19 DNA commonly exists in human skin. Therefore, the association between B19 infection and chronic urticaria remains uncertain. However, these findings raise the question whether the skin may constitute a reservoir for B19.

Infection of synovial fibroblasts in culture by Yersinia enterocolitica and Salmonella enterica serovar Enteritidis: ultrastructural investigation with respect to the pathogenesis of reactive arthritis

Synovial fibroblasts were infected with Yersinia enterocolitica or Salmonella enterica serovar Enteritidis and analyzed by electron microscopy and fluorescence in situ hybridization. Intracellular bacterial replication was followed by degradation leading to "ghosts" possessing lipopolysaccharides but not DNA. However, single bacteria survived for more than 2 weeks. Therefore, transient intra-articular infection might be the missing link between initial intestinal infection and late synovial inflammation in the pathogenesis of reactive arthritis.

Development of conventional and real-time PCR assays for detection of Legionella DNA in respiratory specimens

The development and validation of a PCR assay based on the use of new 16S ribosomal DNA (rDNA)-targeted primers to detect Legionella DNA in respiratory specimens are described. The assay was originally developed as conventional PCR followed by electrophoretic detection and was then adapted to Lightcycler format with SYBR Green I detection and melting curve analysis. The 73 Legionella pneumophila strains tested were amplified with both applications. In addition, 21 and 23 out of 27 other Legionella strains were found positive by conventional and real-time PCR assays, respectively, including the clinically important species L. micdadei, L. bozemaniae, and L. dumoffii. Two DNA purification methods were compared using artificially seeded clinical specimens: a standard organic extraction method and a commercial kit based on adsorption of DNA to silica particles. The detection limit of the assay varied from 2 CFU to >200,000 CFU per ml of clinical specimen, depending on the background sample (i.e., pooled sputa or BAL fluids) and the DNA purification method, the silica method achieving lower detection limits. Analysis of 77 clinical samples (66 bronchoalveolar lavage fluid and 11 sputum samples) by conventional PCR yielded results that were consistent with Legionella culture results. The melting curve analysis in the Lightcycler system readily detected the specific amplification products. However, run-to-run variations in the measured melting temperatures required normalization against the standard sample in each run. The results obtained with the clinical specimens were similar to those obtained with conventional PCR, but more samples are required to determine whether the system can be applied to routine screening of samples for the presence of Legionella DNA.

Recognition of B cells epitopes of the Klebsiella pneumoniae GroEL-like protein by HLA-B27 positive subjects

The presence of antibodies against antigens of K. pneumoniae in HLA-B27 positive patients with ankylosing spondylitis (AS), has been well documented. We have previously reported that sera from HLA-B27 positive subjects react with the K. pneumoniae GroEL-like protein (HSP60Kp) and have higher titers than HLA-B27 negative individuals. We cloned the gene that codes for this protein, determined hydrophilic regions by computer analysis of the predicted amino acid sequence and found that residues 389-397, 360-368 and 282-290, were possible B cell epitopes. To test this prediction, and to determine if the HLA-B27 positive and negative AS patients recognize the same or different epitopes, we truncated the hsp60Kp gene, from the 3; terminal nucleotide, to obtain fragments having or not the predicted epitopes. Four polypeptides of 40, 37, 30 and 18 kDa were obtained and analysed, by ELISA and inhibition of ELISA, for their reactivity with IgG antibodies from three high responders HLA-B27 positive AS patients and three HLA-B27 negative subjects who recognized the rHSP60Kp. Sera from both HLA-B27 positive and negative subjects reacted equally well with rHSP60Kp or with the 40 and 37 kDa peptides, which do not have residues 389-397 and 360-368, respectively, but reactivity was lost with the 30 kDa peptide, which also lacks residues 282-290. Contrary to what we expected, antibodies from HLA-B27 negative and positive individuals recognized the same epitope of the HSP60Kp. Our results indicate that the important epitope for B cells could be the 282-290 region and that the contribution of the two other predicted regions is minimal. We also conclude that the differences in response to the HSP60Kp in HLA-B27 positive AS patients and HLA-B27 negative individuals is not qualitative, but only quantitative.

Direct amplification of rRNA genes in diagnosis of bacterial infections

A broad-range bacterial PCR targeting rRNA genes (rDNAs) was used to directly analyze 536 clinical samples obtained from 459 hospitalized patients during a 4-year study period. The molecular diagnosis based on DNA sequencing of the PCR product was compared to that obtained by bacterial culture. The bacteriological diagnosis was concordant for 447 (83%) specimens. Broad-range rDNA PCR was the only method that yielded an etiologic diagnosis for 11 (2.4%) of 459 patients. Compared to culture and clinical assessment, the sensitivity of the PCR method combined with sequencing was 74.2%, and the specificity was between 98.7 and 99.6%. At present, the described molecular approach proved superior to bacterial culture in two clinical situations: infections caused by bacteria with unusual growth requirements and specimens taken during antimicrobial treatment of the patient.

Clinical and experimental evidence for persistent Yersinia infection in reactive arthritis

The findings of bacterial antigens in the joint and persistent triggering infection elsewhere in the body are thought to be important in the pathogenesis of reactive arthritis (ReA). We describe a patient with clinical and laboratory features consistent with this. The initial presentation with erythema nodosum and periarthritis due to infection with Yersinia pseudotuberculosis IV was followed 13 months later by recurrent erythema nodosum with joint effusion. At that time, synovial fluid was shown to contain Yersinia antigens, and, surprisingly, Yersinia-specific 16S ribosomal RNA (rRNA) sequences were also identified by reverse transcriptase-polymerase chain reaction and sequencing. Since there was no serologic evidence of reinfection, we postulate that a silent persistent Yersinia infection was reactivated, leading to dissemination of organisms to the joint, with consequent induction of ReA. Although the finding of synovial Yersinia antigens years after the original infection in ReA has previously been reported, the presence of Yersinia 16S rRNA indicates that viable organisms were also able to reach the joint.

No benefit of long-term ciprofloxacin treatment in patients with reactive arthritis and undifferentiated oligoarthritis: a three-month, multicenter, double-blind, randomized, placebo-controlled study

OBJECTIVE

To investigate the effect of long-term antibiotic treatment in patients with reactive arthritis (ReA) and undifferentiated oligoarthritis.

METHODS

One hundred twenty-six patients were treated with ciprofloxacin (500 mg twice a day) or placebo for 3 months, in a double-blind, randomized study. Of these patients, 104 (48 treated with ciprofloxacin and 56 treated with placebo) were valid for clinical evaluation: 55 were diagnosed as having ReA with a preceding symptomatic urogenic or enteric infection and 49 as having undifferentiated oligoarthritis. These 2 groups were randomized separately. The triggering bacterium was sought by serology and/or culture. The percentage of patients in remission after 3 months of treatment was chosen as the primary efficacy parameter.

RESULTS

A triggering bacterium could be identified in 52 patients (50%): Chlamydia trachomatis in 13, Yersinia in 14, and Salmonella in 25. No patient was positive for Campylobacter jejuni or for Shigella. No difference in outcome was found between treatment with ciprofloxacin or placebo in the whole group or in subgroups of patients with ReA or undifferentiated oligoarthritis. No difference was seen in patients with a disease duration <3 months. Ciprofloxacin was not effective in Yersinia- or Salmonella-induced arthritis but seemed to be better than placebo in Chlamydia-induced arthritis. This difference was not significant, however, which might be due to the small sample size.

CONCLUSION

Long-term treatment of ReA with ciprofloxacin is not effective; however, it might be useful in the subgroup of patients who have Chlamydia-induced arthritis. This has to be proven in a bigger study focusing on patients with Chlamydia-induced arthritis.

Salmonella-triggered reactive arthritis: use of polymerase chain reaction, immunocytochemical staining, and gas chromatography-mass spectrometry in the detection of bacterial components from synovial fluid

OBJECTIVE

To investigate whether microbial components are present in the cells of synovial fluid or peripheral blood from patients with Salmonella-triggered reactive arthritis (ReA).

METHODS

Synovial fluid cells and/or peripheral blood cells from 23 patients with Salmonella-triggered ReA and from 19 control patients with newly diagnosed rheumatoid arthritis were studied using 3 different polymerase chain reaction (PCR) techniques and immunocytochemical staining. Muramic acid from the synovial fluid was studied by gas chromatography-mass spectrometry.

RESULTS

Salmonella chromosomal DNA was not detectable in the synovial fluid cells and peripheral blood leukocytes of patients with Salmonella ReA. Initially, positive reactions were observed in the synovial fluid cells and peripheral blood leukocytes of 3 of 17 and 3 of 18 patients with ReA, respectively, but in the subsequent PCR studies, these findings were not reproducible. Salmonella-specific antigen was detectable by immunofluorescence in the synovial fluid cells and peripheral blood leukocytes of 4 of 11 and 2 of 7 patients with ReA, respectively. Muramic acid was present in 2 of 15 synovial fluid samples from patients with ReA, but the bacterial cultures from synovial fluid were negative.

CONCLUSION

These findings indicate the presence of bacterial degradation products, but not bacterial DNA, in the inflamed joints of patients with Salmonella-triggered ReA.

Pathogenesis of human leukocyte antigen B27-positive arthritis. Information from clinical materials

In the spondyloarthropathies human leukocyte antigen (HLA) B27 confers a strong genetic predisposition to the development and to the chronicity of disease after extra-articular infection with certain gram-negative bacteria. The close relationships between infection, HLA-B27, other genetic factors, and the host immune system, however, still are unexplained. HLA-B27-positive arthritis continues to be an area of intensive investigation in basic and clinical research. New animal models with HLA-B27 transgenic mice and rats, as well as recent developments in understanding the processes involved in signal transduction, cytokine production, and human T-lymphocyte activation, contribute to the development of new pathogenic models of the spondyloarthropathies. This article summarizes the current concepts of the cause and pathogenesis of the spondyloarthropathies resulting from studies of clinical materials. The host-microbial interplay in human disease, namely in bacteria-induced reactive arthritis, may eludicate principle disease mechanisms in acute disease and in the development of chronic autoimmune arthritis or ankylosing spondylitis.

Bowel inflammation and the spondyloarthropathies

The concept of spondyloarthropathies gathers together a group of chronic diseases in which not only the locomotor system is involved but also other organs, especially the gastrointestinal tract. In humans, ileocolonoscopic studies demonstrated the presence of inflammatory gut lesions in all the diseases in the spondyloarthropathy group; their presence varied in the different diseases between 20% and 70%. The inflammation could be related to specific disease features in the spondyloarthropathies. Further research supports the hypothesis of subclinical inflammatory bowel disease in some patients with spondyloarthropathy, in which the locomotor inflammation was the only clinical manifestation. The link between gut inflammation and arthropathy has also been demonstrated in animal models, notably the human leukocyte antigen B27 transgenic rats. The temporal relationship between activity and severity of colonic involvement and flares of peripheral arthritis directs treatment of choice. For all forms of enterogenic arthropathies, nonsteroidal anti-inflammatory drugs remain the acute treatment form. Caution is in order, however, because of their possible harmful effects on intestinal integrity, permeability, and even on gut inflammation.

The pathogenesis of HLA-B27 arthritis: role of HLA-B27 in bacterial defense

The way in which a host accommodates invasive facultative intracellular bacteria must be the key to the development of reactive arthritis. Investigators have analyzed the bacterial events at several levels: invasion into host cells, intracellular survival, translocation from the sites of infection to the joints, residence in the joints, and evasion of host defense. Because HLA-B27 is present in higher incidence in patients with reactive arthritis and is an essential gene in the related ankylosing spondylitis, the role of HLA-B27 in host defense is also assumed to be important in the development of reactive arthritis. This review summarizes the various studies in this field.

Infectious agents as triggers of reactive arthritis

Reactive arthritis was originally defined as a sterile joint inflammation after infection elsewhere in the body, but this view has been challenged in the past decade since different antigens and DNA and RNA of various triggering microbes have been shown to exist at the sites of inflammation in the joints. It has been suggested that microbial antigens, or intact pathogens, are important for the pathogenesis of reactive arthritis, at least in the early phase of the disease, but the exact mechanism of how the pathogens contribute to the development of this usually self-limiting polyarthritis has not been discovered. This article reviews the theories on the role of infectious agents as triggers of reactive arthritis.

Reactive arthritis

Concepts about reactive arthritis are changing and must embrace consideration of the fact that bacteria or their products are present in the joint, not just at the portal of entry in the gastrointestinal (GI) or genitourinary (GU) tracts. With chlamydia-associated disease, atypical elementary bodies can be seen in synovium by electron microscopy, and nucleic acids, including RNA, can be found. It is not yet clear if bacterial nucleic acids are present in postenteric reactive arthritis and whether disease courses are predictably different after GI or GU infection. How bacteria are disseminated to joints and local factors, including cytokines that influence their persistence, are under study. Treatment with antibiotics may help some chlamydia-associated reactive arthritis but is not invariably effective.

Arthritogenicity of Yersinia enterocolitica O:8 in hamsters: analysis of the immune response

An animal model, hamster, was used for the study of Yersinia-induced arthritis. The development of arthritis, estimated by measuring the inflammation on hind paws after infection, was correlated with the kinetics of the immune response. Histological and immunofluorescence (IFI) studies and serum antibody measurements were performed. Two inflammatory peaks were observed: an acute one on day 11 post-infection (p.i.) and a chronic one on days 26-35 p.i. Joint cultures were positive until day 14 p.i. IFI was used to demonstrate the deposit of bacterial antigens in the joint. A persistent response of cellular extract-specific IgG antibodies was observed until day 94. Lipopolysaccharide-specific IgG was statistically significant on day 26 p.i. Antibodies against bands 66 and 54 were observed by immunoblotting. Polyclonal activation was detected during reactive arthritis. It is shown that Y. enterocolitica is arthritogenic in hamsters, immune mechanisms participating in the development of this disease.

Humoral immune response in Yersinia enterocolitica O:5 induced arthritis in hamsters

Yersinia enterocolitica can cause extraintestinal sequelae such as reactive arthritis. The immunopathogenic mechanisms of this disease have not been completely clarified. Autoimmunity and persistent immune responses against bacterial antigens have been related to Yersinia-induced arthritis. The arthritogenic capacity of Y. enterocolitica O:5 and the kinetics of the development of autoantibodies and Yersinia antigen-specific antibodies were studied in hamsters. The results indicated that Y. enterocolitica O:5 was arthritogenic in the animal model studied. The animals developed septic arthritis on day 2 post-infection (p.i.) and reactive arthritis on day 65 p.i. An important IgG response to types I and II collagen and the persistence of antibodies against lipopolysaccharide and bacterial cellular extract were observed. By immunoblotting, it was obtained that IgG reacted against a large number of bacterial antigens, the strongest being the responses against 88, 76, 63 and 36-33 kDa peptides. From the results obtained, it can be concluded that serovar O:5 was experimentally arthritogenic, and that both autoimmune mechanisms and Yersinia-specific antibodies participated in the development of Yersinia-induced reactive arthritis in the animal model studied.

HLA-B27 modulates the survival of Salmonella enteritidis in transfected L cells, possibly by impaired nitric oxide production

Reactive arthritis is triggered by certain microbes that cause primary infections mainly on the gastrointestinal or urogenital mucosa. The disease is strongly associated with HLA-B27. Long persistence of causative microbes or their structures in the body has been thought to have an important role in the pathogenesis of reactive arthritis. This suggests that the elimination of the microbes causing reactive arthritis is ineffective or disturbed in HLA-B27-positive individuals developing this complication. We examined the role of the HLA-B27 antigen in microbe-host interaction in vitro by monitoring the invasion and intracellular survival of Salmonella enteritidis in mouse fibroblasts transfected with HLA-B27, HLA-B7, or beta2-microglobulin only. S. enteritidis invaded into all the three transfectants with the same efficiency. However, at 6 and 10 days after incubation, there were more living intracellular Salmonella organisms in HLA-B27 transfectants than in the other transfected cell lines (P < 0.05), suggesting that the bactericidal effect is impaired in these cells. Impaired NO production in HLA-B27-transfected cells was indicated as a possible mechanism, since the amount of nitrite in the supernatants of the Salmonella-infected HLA-B27-transfected cells was smaller than that in the supernatants of the Salmonella-infected HLA-B7- or beta2-microglobulin-transfected cells (P < 0.001). The inhibition of NO synthesis by N-monomethyl-L-arginine resulted in impaired elimination of Salmonella also in HLA-B7and beta2-microglobulin-transfected cells. The inverse correlation between intracellular survival of Salmonella and the amount of nitrite detected in culture supernatants supports the hypothesis that the L-arginine-dependent NO pathway plays an important role in the murine fibroblast response against Salmonella. We suggest that a major histocompatibility complex class I antigen, HLA-B27, may contribute to the intracellular persistence of Salmonella by a mechanism which involves the NO pathway.

Infection-related arthritis

Postinfection arthritis represents a significant portion of the referrals to pediatric rheumatology centers, particularly in the United States. Many viral and common bacterial infections can be associated with arthritis, and their recognition can sometimes be difficult on a clinical basis. In patients with acute onset of arthritis, the clinician should actively seek epidemiologic, clinical, or laboratory evidence of infection. Diagnostic tests should be used rationally and results interpreted carefully. Some infections, once recognized, require antibiotic treatment, but in most cases anti-inflammatory therapy is successful in treating articular symptoms.

HLA-B27 modulates intracellular survival of Salmonella enteritidis in human monocytic cells

Human major histocompatibility complex class I allele HLA-B27 is associated with a group of diseases called spondyloarthropathies. In reactive arthritis (ReA), the disease is triggered by certain infections, e.g. gastroenteritis caused by Salmonella. The host/microbe interaction is abnormal in susceptible individuals leading to inefficient elimination of arthritis-triggering bacteria, fragments of them, or both, after the initial infection. Using transfected human monocytic U937 cell lines, we demonstrate that the expression of the HLA-B27 antigen does not influence the uptake of S. enteritidis into U937 cells in vitro. Interestingly, HLA-B27 remarkably impairs the elimination of S. enteritidis within the HLA-B27 transfected U937 cells. The impaired elimination of ReA-triggering microbes by HLA-B27+ monocytes may offer an explanation for the persistence of ReA-triggering microbes in susceptible HLA-B27+ individuals. This modulation of the host/microbe interaction by HLA-B27 may have an important role in the pathogenesis of ReA.

Host-microbe interaction in HLA-B27-associated diseases

The mechanisms leading to the development of HLA-B27-associated diseases, spondyloarthropathies, are unknown. One of them, reactive arthritis, is clearly caused by an infection, and joint inflammation develops soon after or during an infection elsewhere in the body. In other forms of spondyloarthropathies, such as ankylosing spondylitis, association with infection is suggested but it is not as clear. Pathogenetic mechanisms of reactive arthritis are a focus of great interest as causative infections and strong genetic association are known. How HLA-B27 determines the appearance of joint complications after certain infections is not clear. Several theories have been proposed to explain the association, and they usually include the idea that interaction between microbe and host is abnormal and inefficient in HLA-B27-positive subjects in whom reactive arthritis develops.

Absolute identification of muramic acid, at trace levels, in human septic synovial fluids in vivo and absence in aseptic fluids

This is the first report of a study employing the state-of-the-art technique of gas chromatography-tandem mass spectrometry for absolute identification of muramic acid (a marker for peptidoglycan) at trace levels in a human or animal body fluid or tissue. Daughter mass spectra of synovial fluid muramic acid peaks (> or = 30 ng/ml) were identical to those of pure muramic acid. Absolute chemical identification at this level represents a 1,000-fold increase in sensitivity over previous gas chromatography-mass spectrometry identifications. Muramic acid was positively identified in synovial fluids during infection and was eliminated over time but was absent from aseptic fluids.

Antibiotic prophylaxis and treatment of reactive arthritis. Lessons from an animal model

OBJECTIVE

To study the effect of antibiotic prophylaxis and treatment of reactive arthritis (ReA), using an experimental model.

METHODS

Yersinia enterocolitica O:8, when injected intravenously into Lewis rats, causes a sterile arthritis closely resembling human ReA in 70% of the animals. Arthritis develops in 1-2 weeks; in some of the animals it remains chronic, and exacerbations occur. This model was applied to study the effect of a 7-day treatment with ciprofloxacin, using 2 different dosages (20 or 100 mg/kg/day) and 4 different schedules for initiation of treatment. The effects were evaluated by determining the daily arthritis score, the number of rats developing arthritis, and fecal excretion of Yersinia. In addition, weight gain was monitored. At autopsy (35 or 60 days after inoculation with bacteria), samples were obtained for determination of Yersinia-specific antibodies in the serum. At the same time, samples were collected from mesenteric lymph nodes, lung, spleen, and liver for bacterial cultures, and from the ankle joints for histologic evaluation. In a separate experiment, ciprofloxacin concentrations in samples from serum and mesenteric lymph nodes were analyzed by high performance liquid chromatography.

RESULTS

A 7-day course with 100 mg/kg/day of ciprofloxacin, started on day 3 after bacterial inoculation, completely prevented the development of ReA and eliminated Yersinia during the 60-day experiment. If a dosage of 20 mg/kg/day was used, development of acute arthritis was prevented, but some of the animals had positive fecal cultures at the end of experiment. If antibiotic treatment was started on day 5, the preventive effect was still observed, but was less pronounced. If the treatment was started at the peak of the development of arthritis, no effect on arthritis was observed.

CONCLUSION

These results indicate that if any effect of antibiotic treatment in Yersinia-triggered ReA is to be expected, the treatment must be started early and given in sufficient dosage. However, antibiotic treatment has no effect on fully developed arthritis.

Aetiological agents and immune mechanisms in enterogenic reactive arthritis

Reactive arthritis is triggered by an infection, either of the genitourinary or gastrointestinal tracts; the common triggering bacteria in enteric ReA include salmonella, shigella, yersinia, and campylobacter. It is still not clear how such different bacteria can lead to a similar clinical picture and have a similar association with the MHC class I antigen HLA-B27. Common both to enterogenic and urogenic bacteria is the type of peripheral joint involvement. However, this is not so different from other bacteria-associated arthritides and is probably the consequence of bacteria persistent inside the joint. What is unique to these bacteria is the HLA-B27-association and the nearly exclusively B27-linked clinical manifestations as sacroiliitis and iritis. Shigella-induced ReA has the highest B27-association while in salmonella- and chlamydia-induced ReA a lower association can be found. Mucosal entry of enterogenic bacteria give easy access to macrophages which might be important for the transport into the joint. Although bacteria-specific antibodies are of diagnostic value, the humoral immune response does not explain the immunopathogenesis and MHC-association of this disease. Bacteria-specific T-cells have been constantly found in the synovial fluid from ReA patients and have been further analysed. The identification of immunodominant antigens of these bacteria is of great importance to understand the pathogenesis. Although an antigen shared by all bacteria has not been identified until now progress is being made in this field. We have also to consider the possibility that these bacteria are not only driving the immune response themselves but rather work as a trigger for autoimmunity.

Spondylarthropathies: from gut to target organs

Recent studies strongly support the concept that gut and joint inflammation are closely related. Progress also has been made in identifying individual mechanisms that contribute to the pathogenesis of joint disease in IBD and in undifferentiated SpAs. However, the interrelationship of these mechanisms that result in chronic disease manifestations at a site distant from the initiating event remain to be elucidated. The local absence of homing molecule receptors in the gut wall combined with an expression of these receptors in target organs can be responsible for the transformation of the synovial membrane and/or the enthesis into an aberrant tertiary lymphoid organ of the gut.

Reactive arthritis-associated bacteria can stimulate lymphocyte proliferation in non-exposed individuals and newborns

In reactive arthritis (ReA) a specific T cell response to the triggering bacterial antigen is present in the synovial fluid, while in paired peripheral blood T cells the response is markedly reduced. The proliferative response to ReA-associated bacteria in the peripheral blood of ReA patients was compared with that seen in the blood of healthy adults, who denied exposure to these microbes, and in the umbilical cord blood of newborns, who have clearly not been exposed to bacterial antigen. Peripheral blood mononuclear cells (PBMC) from non-exposed adults and those from umbilical cord blood proliferated to ReA-associated bacteria, whilst little response was seen in ReA PBMC. The response was MHC class II-restricted, required processing of the bacterial antigen, was seen in both CD45RO+ and CD45RA+ subsets, and was not oligoclonal. These T cell responses are similar to those previously demonstrated in non-exposed individuals to malaria, leishmania and trypanosoma antigen, and may reflect the existence of 'natural' T cell immunity to ReA-associated bacteria. The lack of such responses in ReA peripheral blood may suggest that such 'natural' responses may restrict the dissemination or progression of infection.