Methotrexate an Old Drug with New Tricks

Methotrexate (MTX) is the first line drug for the treatment of a number of rheumatic and non-rheumatic disorders. It is currently used as an anchor disease, modifying anti-rheumatic drug in the treatment of rheumatoid arthritis (RA). Despite the development of numerous new targeted therapies, MTX remains the backbone of RA therapy due to its potent efficacy and tolerability. There has been also a growing interest in the use of MTX in the treatment of chronic viral mediated arthritis. Many viruses-including old world alphaviruses, Parvovirus B19, hepatitis B/C virus, and human immunodeficiency virus-have been associated with arthritogenic diseases and reminiscent of RA. MTX may provide benefits although with the potential risk of attenuating patients' immune surveillance capacities. In this review, we describe the emerging mechanisms of action of MTX as an anti-inflammatory drug and complementing its well-established immunomodulatory activity. The mechanisms involve adenosine signaling modulation, alteration of cytokine networks, generation of reactive oxygen species and HMGB1 alarmin suppression. We also provide a comprehensive understanding of the mechanisms of MTX toxic effects. Lastly, we discussed the efficacy, as well as the safety, of MTX used in the management of viral-related rheumatic syndromes.

Clinical and pathologic aspects of arthritis due to Ross River virus and other alphaviruses

PURPOSE OF REVIEW

Arthritogenic alphaviruses are globally distributed mosquito-borne RNA viruses causing epidemics of polyarthritis/arthralgia, with disease emerging or reemerging and increasingly being reported in travelers. This article summarizes the current knowledge of these diseases, focusing on recent developments in the understanding of Ross River virus disease.

RECENT FINDINGS

Alphaviral arthritides have often been blamed for protracted chronic illnesses. However, validated quality-of-life questionnaires and exhaustive searches for differential diagnoses showed that Ross River virus disease, although severe at onset, progressively resolved over 3 to 6 months. Many patients did experience long-term disease lasting more than 12 months, but in nearly all cases this was due to other conditions, primarily unrelated rheumatic conditions or depression. There is no indication that alphaviral arthritides predispose to other conditions; thus, patients whose Ross River virus disease has actually resolved may be underdiagnosed for other conditions. Ross River virus polyarthritis probably arises from inflammation associated with productive viral infections in synovial macrophages, which persist despite neutralizing antibodies and antiviral cytokine responses. Persistence may be facilitated by downregulation of cytokine responses by virus-antibody complexes binding to Fc receptors and induction of interleukin-10. How virus escapes neutralizing antibodies remains unclear but may involve phagocytosis of apoptotic virus-infected cells and infection of the phagocyte via the phagosome.

SUMMARY

Diagnosis of alphaviral arthritides is complicated by nonspecific symptoms and the lack of commercial serodiagnostic kits, except for Ross River and Barmah Forest virus infections in Australia. Differential diagnoses should be actively pursued, especially if symptoms persist. Treatment with nonsteroidal anti-inflammatory drugs appears largely effective, with no evidence of long-term sequelae or relapse.

Advances in the biology, diagnosis and host-pathogen interactions of parvovirus B19

Increased recognition of parvovirus B19 (B19), an erythrovirus, as a significant human pathogen that causes fetal loss and severe disease in immunocompromised patients has resulted in intensive efforts to understand the pathogenesis of B19-related disease, to improve diagnostic strategy that is deployed to detect B19 infection and blood-product contamination and, finally, to elucidate the nature of the cellular immune response that is elicited by the virus in diverse patient cohorts. It is becoming clear that at least three related erythrovirus strains (B19, A6/K71 and V9) are circulating in the general population and that viral entry into target cells is mediated by an expanding range of cellular receptors, including P antigen and beta-integrins. Persistent infection by B19 is emerging as a contributory factor in autoimmune disease, a hypothesis that is constrained by the detection of B19 in the skin of apparently healthy individuals. B19 infection during pregnancy may account for thousands of incidences of fetal loss per annum in Europe, North America and beyond, yet there is currently only minimal screening of pregnant women to assess serological status, and thereby risk of infection, upon becoming pregnant. Whilst major advances in diagnosis of B19 infection have taken place, including standardization of serological and DNA-based detection methodologies, blood donations that are targeted at high-risk groups are only beginning to be screened for B19 IgG and DNA as a means of minimizing exposure of at-risk patients to the virus. It is now firmly established that a Th1-mediated cellular immune response is mounted in immunocompetent individuals, a finding that should contribute to the development of an effective vaccine to prevent B19 infection in selected high-risk groups, including sickle-cell anaemics.

Chronic parvovirus B19 infection induces the production of anti-virus antibodies with autoantigen binding properties

Human parvovirus B19 infection in adults shows some clinical features similar to those found in autoimmune connective tissue diseases. To better clarify the relationship between viral infection and autoimmunity, we have evaluated the ability of anti-parvovirus antibodies to specifically recognize autoantigens in ten patients with chronic symmetric arthritis resembling rheumatoid arthritis or with recurrent episodes of arthritis and cutaneous manifestations and persistence of specific IgM antibodies against B19 parvovirus. We synthetized a 24-amino acid immunodominant peptide corresponding to a part of the virus protein 1 and virus protein 2 overlapping region. The peptide has been used to test patients' sera at different time points with an enzyme-linked immunosorbent assay (ELISA) and to purify anti-virus antibodies by affinity chromatography on a peptide-Sepharose column. Eluted immunoglobulins recognized the B19 peptide in both direct and competitive ELISA. Affinity-purified anti-parvovirus antibodies were then tested on a panel of autoantigens including human keratin, collagen type II, thyreoglobulin, single-strand (ss)DNA, cardiolipin and ribonucleoprotein antigen Sm. Eluted antibodies specifically recognized keratin, collagen type II, ssDNA and cardiolipin. Autoantibody activity was not detected in the immunoglobulin fraction after complete removal of anti-peptide antibodies and in antibodies eluted from normal donors. Epstein-Barr virus-transformed cell clones obtained from two subjects produced antibodies which simultaneously recognize the viral peptide and several autoantigens. To further confirm the role of the virus in inducing an autoantibody response, eight BALB/c mice were immunized with the viral peptide coupled to a carrier protein. Autoantibody activity against keratin, collagen II, cardiolipin and ssDNA was detected in six of the eight mice which developed a strong anti-virus response. Together, these data indicate that B19 parvovirus may be linked to the induction of an autoimmune response.

Musculoskeletal manifestations and autoantibody profile in 90 hepatitis C virus infected Israeli patients

OBJECTIVES

Recent interest has been expressed in rheumatic manifestations in hepatitis C virus (HCV)-infected populations. The aim of this study was to determine the prevalence and characteristics of the musculoskeletal manifestations and serological markers of autoimmunity in HCV-infected patients in Israel.

METHODS

Ninety anti-HCV-positive patients were consecutively interviewed and examined. The prevalence of autoantibodies and their association with rheumatologic symptoms were also determined.

RESULTS

Rheumatic manifestations were found in 28 subjects (31%), and included arthralgias (9%), arthritis (4%), cryoglobulinemia (11%), sicca symptoms (8%), cutaneous vasculitis (2%), polymyositis (1%), and antiphospholipid syndrome (1%). Rheumatic complications were not associated with liver disease severity, or subjects' gender. In addition, myalgia was reported by 22 patients (24%), and fibromyalgia was diagnosed in 14 (16%). Sixty-nine percent of the patients had at least one autoantibody detected in their serum, the most prevalent being rheumatoid factor (RF), 44%; antinuclear antibody (ANA), 38%; and IgM and IgG anticardiolipin antibodies (ac1), 28% and 22%, respectively. The frequency of autoantibodies was not associated with liver disease severity or rheumatic disorders.

CONCLUSIONS

Musculoskeletal manifestations and autoimmune markers are common in HCV infection. An investigation of risk factors for HCV infection is pertinent in a patient presenting new rheumatic manifestations and should be included in the history of present illness. Future studies of these disorders may uncover the full spectrum of these associations and provide new insights into their operating mechanisms.

Roles of IL-1 in the development of rheumatoid arthritis: consideration from mouse models

Expression of inflammatory cytokines is augmented in the joints of patients with rheumatoid arthritis (RA). We found that cytokine levels are also elevated in the joints of a mouse arthritis model, human T-cell leukemia virus type I (HTLV-I) transgenic (Tg) mouse. Depletion of IL-1 by gene targeting greatly reduced the incidence of the disease, indicating the importance of this cytokine in the development of arthritis. Furthermore, IL-1 receptor antagonist (IL-1Ra)-deficient mice develop autoimmunity and arthritis spontaneously. These observations suggest that excess IL-1 signaling the causes autoimmunity. We show that IL-1 activates the immune system non-specifically by inducing CD40L and OX40 co-signaling molecules on T cells. In this review, the roles of IL-1 in the development of autoimmunity and arthritis in mouse models will be discussed.

Detection of multiple viral DNA species in synovial tissue and fluid of patients with early arthritis

OBJECTIVE

Viruses have a role in the pathogenesis of various forms of arthritis. This study aimed at determining whether viral DNA can be detected in joint samples in the early stages of idiopathic arthritides.

METHODS

Synovial fluid (SF) and synovial tissue (ST) samples were obtained from 73 patients, with undifferentiated arthritis (n=22), rheumatoid arthritis (n=13), spondyloarthropathy (n=17), crystal arthropathy (n=8), osteoarthritis (n=7), septic arthritis (n=5), and trauma (n=1). The presence of viral DNA was investigated by polymerase chain reaction analysis.

RESULTS

Cytomegalovirus was present in 25 patients, parvovirus B19 in 15 patients, Epstein-Barr virus in 12 patients, and herpes simplex virus in 16 patients (in ST, SF, or both), respectively. The joint samples were negative for viral DNA from adenovirus and varicella-zoster virus. In ST, eight patients were double positive for parvovirus B19 and another viral DNA, with herpes simplex virus being the most prevalent. Seven patients were double positive for other viruses (cytomegalovirus, herpes simplex virus, Epstein-Barr virus). In SF, four patients were double or triple positive for viral DNA. Paired samples were available in 56 patients. In these, viral DNA was detected in 37 patients in ST, as compared with 19 in SF.

CONCLUSION

These data show that one or more viruses can be detected in the synovial specimens of patients with early arthritis, irrespective of the clinical diagnosis. This observation might be explained by migration of inflammatory cells harbouring viral DNA into the inflamed joints.

Specificity of T cells in synovial fluid: high frequencies of CD8(+) T cells that are specific for certain viral epitopes

INTRODUCTION

Epstein-Barr virus (EBV) is transmitted orally, replicates in the oropharynx and establishes life-long latency in human B lymphocytes. T-cell responses to latent and lytic/replicative cycle proteins are readily detectable in peripheral blood from healthy EBV-seropositive individuals. EBV has also been detected within synovial tissue, and T-cell responses to EBV lytic proteins have been reported in synovial fluid from a patient with rheumatoid arthritis (RA). This raises the question regarding whether T cells specific for certain viruses might be present at high frequencies within synovial fluid and whether such T cells might be activated or able to secrete cytokines. If so, they might play a 'bystander' role in the pathogenesis of inflammatory joint disease.

OBJECTIVES

To quantify and characterize T cells that are specific for epitopes from EBV, cytomegalovirus (CMV) and influenza in peripheral blood and synovial fluid from patients with arthritis.

METHODS

Peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) were obtained from patients with inflammatory arthritis (including those with RA, osteoarthritis, psoriatic arthritis and reactive arthritis). Samples from human leucocyte antigen (HLA)-A2-positive donors were stained with fluorescent-labelled tetramers of HLA-A2 complexed with the GLCTLVAML peptide epitope from the EBV lytic cycle protein BMLF1, the GILGFVFTL peptide epitope from the influenza A matrix protein, or the NLVPMVATV epitope from the CMV pp65 protein. Samples from HLA-B8-positive donors were stained with fluorescent-labelled tetramers of HLA-B8 complexed with the RAKFKQLL peptide epitope from the EBV lytic protein BZLF1 or the FLRGRAYGL peptide epitope from the EBV latent protein EBNA3A. All samples were costained with an antibody specific for CD8. CD4+ T cells were not analyzed. Selected samples were costained with antibodies specific for cell-surface glycoproteins, in order to determine the phenotype of the T cells within the joint and the periphery. Functional assays to detect release of IFN- or tumour necrosis factor (TNF)- were also performed on some samples.

RESULTS

The first group of 15 patients included 10 patients with RA, one patient with reactive arthritis, one patient with psoriatic arthritis and three patients with osteoarthritis. Of these, 11 were HLA-A2 positive and five were HLA-B8 positive. We used HLA-peptide tetrameric complexes to analyze the frequency of EBV-specific T cells in PBMCs and SFMCs (Figs 1 and 2). Clear enrichment of CD8+ T cells specific for epitopes from the EBV lytic cycle proteins was seen within synovial fluid from almost all donors studied, including patients with psoriatic arthritis and osteoarthritis and those with RA. In donor RhA6, 9.5% of CD8+ SFMCs were specific for the HLA-A2 restricted GLCTLVAML epitope, compared with 0.5% of CD8+ PBMCs. Likewise in a donor with osteoarthritis (NR4), 15.5% of CD8+ SFMCs were specific for the HLA-B8-restricted RAKFKQLL epitope, compared with 0.4% of CD8+ PBMCs. In contrast, we did not find enrichment of T cells specific for the HLA-B8-restricted FLRGRAYGL epitope (from the latent protein EBNA3A) within SFMCs compared with PBMCs in any donors. In selected individuals we performed ELISpot assays to detect IFN- secreted by SFMCs and PBMCs after a short incubation in vitro with peptide epitopes from EBV lytic proteins. These assays confirmed enrichment of T cells specific for epitopes from EBV lytic proteins within synovial fluid and showed that subpopulations of these cells were able to secrete proinflammatory cytokines after short-term stimulation. We used a HLA-A2/GILGFVFTL tetramer to stain PBMCs and SFMCs from six HLA-A2-positive patients. The proportion of T cells specific for this influenza epitope was low (<0.2%) in all donors studied, and we did not find any enrichment within SFMCs. We had access to SFMCs only from a second group of four HLA-A2-positive patients with RA. A tetramer of HLA-A2 complexed to the NLVPMVATV epitope from the CMV pp65 protein reacted with subpopulations of CD8+ SFMCs in all four donors, with frequencies of 0.2, 0.5, 2.3 and 13.9%. SFMCs from all four donors secreted TNF after short-term incubation with COS cells transfected with HLA-A2 and pp65 complementary DNA. We analyzed the phenotype of virus-specific cells within PBMCs and SFMCs in three donors. The SFMC virus-specific T cells were more highly activated than those in PBMCs, as evidenced by expression of high levels of CD69 and HLA-DR. A greater proportion of SFMCs were CD38+, CD62L low, CD45RO bright, CD45RA dim, CD57+ and CD28- when compared with PBMCs.

DISCUSSION

This work shows that T cells specific for certain epitopes from viral proteins are present at very high frequencies (up to 15.5% of CD8+ T cells) within SFMCs taken from patients with inflammatory joint disease. This enrichment does not reflect a generalized enrichment for the 'memory pool' of T cells; we did not find enrichment of T cells specific for the GILGFVFTL epitope from influenza A or for the FLRGRAYGL epitope from the EBV latent protein EBNA3A, whereas we found clear enrichment of T cells specific for the GLCTLVAML epitope from the EBV lytic protein BMLF1 and for the RAKFKQLL epitope from the EBV lytic protein BZLF1. The enrichment might reflect preferential recruitment of subpopulations of virus-specific T cells, perhaps based on expression of selectins, chemokine receptors or integrins. Alternatively, T cells specific for certain viral epitopes may be stimulated to proliferate within the joint, by viral antigens themselves or by cross-reactive self-antigens. Finally, it is theoretically possible that subpopulations of T cells within the joint are preferentially protected from apoptotic cell death. Whatever the explanation, the virus-specific T cells are present at high frequency, are activated and are able to secrete proinflammatory cytokines. They could potentially interact with synoviocytes and contribute to the maintenance of inflammation within joints in many different forms of inflammatory arthritis.

Vasculitis and infections: contribution to the issue of autoimmunity reviews devoted to "autoimmunity and infection"

Infections are associated with secondary forms of vasculitis. However, there is increasing evidence that microbial agents play a role also in primary systemic vasculitides. For a long time it has been noted that Hepatitis B virus (HBV) is involved in polyarteritis nodosa (PAN) although the incidence of HBV-associated PAN seems to decline. Cryoglobulinemic vasculitis has been shown to be strongly associated with Hepatitis C Virus (HCV) infection, but this is most striking in Southern Europe and less in Northern Europe. Different microbial agents have been suggested to influence disease expression in other primary vasculitides but no specific association has been established. In Wegener’s Granulomatosis (WG) chronic carriage of Staphylococcus aureus (S. aureus) is associated with a strongly increased risk for relapsing disease. Various pathogenic pathways for this association have been suggested by clinical and experimental observations. Recent studies even suggest that S. aureus derived peptides, amongst others, may induce proteinase 3-ANCA via idiotypic–anti-idiotypic interactions. Treatment with co-trimoxazole in WG localized to the upper airways may result in (temporary) remission of the disease.

Epstein-Barr virus induces erosive arthritis in humanized mice

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of rheumatoid arthritis (RA) on the basis of indirect evidence, such as its presence in affected joint tissues, antigenic cross reactions between EBV and human proteins, and elevated humoral and cellular anti-EBV immune responses in patients. Here we report development of erosive arthritis closely resembling RA in humanized mice inoculated with EBV. Human immune system components were reconstituted in mice of the NOD/Shi-scid/IL-2Rγ^null (NOG) strain by transplantation with CD34⁺ hematopoietic stem cells isolated from cord blood. These humanized mice were then inoculated with EBV and examined pathologically for the signs of arthritis. Erosive arthritis accompanied by synovial membrane proliferation, pannus formation, and bone marrow edema developed in fifteen of twenty-three NOG mice transplanted with human HSC and inoculated with EBV, but not in the nine NOG mice that were transplanted with HSC but not inoculated with EBV. This is the first report of an animal model of EBV-induced arthritis and strongly suggest a causative role of the virus in RA.

Mosquito-borne viruses and epidemic polyarthritis

The two most common mosquito-borne viruses associated with epidemic polyarthritis and polyarticular disease are Ross River and Barmah Forest viruses, accounting for about 90% and 10%, respectively, of serologically confirmed cases. Occasional cases of polyarticular disease in Australia have been associated with infection by other mosquito-borne arboviruses, but the role of these viruses in human disease remains to be confirmed.

Chikungunya virus takes centre stage in virally induced arthritis: possible cellular and molecular mechanisms to pathogenesis

Chikungunya virus (CHIKV) causes an acute symptomatic illness with fever, skin rash (hypersensitivity vasculitis), incapacitating arthralgia which can evolve to chronic arthritis in elderly patients. Clinical observations from cohort studies have been corroborated with data from experimental infection in several mouse and non-human primate models as discussed herein.

Outcome of hepatitis E virus infection in patients with inflammatory arthritides treated with immunosuppressants: a French retrospective multicenter study

The clinical presentation and outcome of hepatitis E virus (HEV) infection in inflammatory rheumatic diseases are unknown. We aimed to investigate the severity of acute HEV infection and the risk of chronic viral replication in patients with inflammatory arthritides treated with immunosuppressive drugs. All rheumatology and internal medicine practitioners belonging to the Club Rhumatismes et Inflammation in France were sent newsletters asking for reports of HEV infection and inflammatory arthritides. Baseline characteristics of patients and the course of HEV infection were retrospectively assessed by use of a standardized questionnaire. From January 2010 to August 2013, we obtained reports of 23 cases of HEV infection in patients with rheumatoid arthritis (n = 11), axial spondyloarthritis (n = 5), psoriatic arthritis (n = 4), other types of arthritides (n = 3). Patients received methotrexate (n = 16), antitumor necrosis factor α agents (n = 10), rituximab (n = 4), abatacept (n = 2), tocilizumab (n = 2), and corticosteroids (n = 10, median dose 6 mg/d, range 2-20). All had acute hepatitis: median aspartate and alanine aminotransferase levels were 679 and 1300 U/L, respectively. Eleven patients were asymptomatic, 4 had jaundice. The HEV infection diagnosis relied on positive PCR results for HEV RNA (n = 14 patients) or anti-HEV IgM positivity (n = 9). Median follow-up was 29 months (range 3-55). Treatment included discontinuation of immunosuppressants for 20 patients and ribavirin treatment for 5. Liver enzyme levels normalized and immunosuppressant therapy could be reinitiated in all patients. No chronic infection was observed. Acute HEV infection should be considered in patients with inflammatory rheumatism and elevated liver enzyme values. The outcome of HEV infection seems favorable, with no evolution to chronic hepatitis or fulminant liver failure.

Viral infections: alpha-viral arthropathy

Six different mosquito-borne viruses (Chikungunya, O'nyong-nyong, Mayaro, Ross River, Sindbis and Barmah Forest) have been associated with arthritis in humans. These viruses are prevalent in the tropics and subtropics and they produce similar symptoms, consisting of fever, joint pains and rash. The symptoms are usually of short duration, around 1 week; complete recovery is the rule apart from exceptional cases of Chik infection. Precise diagnosis requires a serological service which is not available in many parts of the tropics these days. Treatment is symptomatic and there is no vaccine currently available. With an increasing number of visitors to the tropics being exposed to potential infection and with rapid air transport it is possible that visitors may return home during the viraemic incubation stage, infect the local mosquito populations and then develop clinical disease.

Potential infectious agents in the induction of arthritides

In the multifactorial etiology of rheumatic diseases, infectious agents are regarded as the major environmental factors that may cause inflammatory arthritides in genetically susceptible hosts. Two not mutually exclusive pathogenetic pathways are hypothesized to explain the initiation and perpetuation of chronic arthritides by infectious agents: persistent infection and induction of immunopathology. In this review we focus on the role of infections in the etiopathogenesis of rheumatoid arthritis. Retroviruses and enteropathogenic bacteria continue to be the most intensively discussed candidates as possible etiologic factors of rheumatoid arthritis. Although there is ample indirect evidence for the involvement of infections in the pathogenesis of autoimmune disease, direct proof is still missing. There may be no single infectious trigger for rheumatoid arthritis, but multiple infectious agents that share antigenic motifs. The "reverse immunology" approach addresses this issue and is discussed in our outlook on future research directions.

Parvovirus B19 in the acute arthropathies and juvenile rheumatoid arthritis

OBJECTIVE

To evaluate the prevalence of recent parvovirus B19 infection in a cohort of children presenting with acute arthropathy and to determine the prevalence of a subsequent diagnosis of juvenile rheumatoid arthritis in this cohort.

METHOD

In this prospective study, parvovirus B19 IgM antibody was investigated in 75 patients who were referred to our clinic with acute joint complaints and also in 75 healthy controls. One patient in each group was excluded due to neuroblastoma and acute lymphoblastic leukaemia. The characteristics of parvovirus B19 IgM positive patients who were accepted as parvovirus B19 arthropathy were further evaluated. All the patients were followed up for at least 6 weeks and the patients with chronic progression of joint complaints were followed for at least 6 months to determine their progress. The cases of juvenile rheumatoid arthritis in this chronic group were identified.

RESULTS

Parvovirus B19 IgM was detected in 16 of 74 patients (21.6%) with acute arthropathy compared with 3 of 74 (4.1%) in the healthy control group (chi(2) = 8.67; P = 0.003). The parvovirus B19 positive patients with arthropathy were more likely to become chronic (P = 3.7 x 10(-7)) and to be diagnosed as juvenile rheumatoid arthritis (P = 0.03) than the parvovirus B19 IgM negative group with arthropathy. Additional joint destruction developed in one case who was parvovirus B19 IgM positive in whom juvenile rheumatoid arthritis was diagnosed during follow up.

CONCLUSION

These data support the hypothesis that parvovirus B19 infection may be associated with the onset of juvenile rheumatoid arthritis in a proportion of patients.

Systems analysis of subjects acutely infected with the Chikungunya virus

The largest ever recorded epidemic of the Chikungunya virus (CHIKV) broke out in 2004 and affected four continents. Acute symptomatic infections are typically associated with the onset of fever and often debilitating polyarthralgia/polyarthritis. In this study, a systems biology approach was adopted to analyze the blood transcriptomes of adults acutely infected with the CHIKV. Gene signatures that were associated with viral RNA levels and the onset of symptoms were identified. Among these genes, the putative role of the Eukaryotic Initiation Factor (eIF) family genes and apolipoprotein B mRNA editing catalytic polypeptide-like (APOBEC3A) in the CHIKV replication process were displayed. We further compared these signatures with signatures induced by the Dengue virus infection and rheumatoid arthritis. Finally, we demonstrated that the CHIKV in vitro infection of murine bone marrow-derived macrophages induced IL-1 beta production in a mechanism that is significantly dependent on the inflammasome NLRP3 activation. The observations provided valuable insights into virus-host interactions during the acute phase and can be instrumental in the investigation of new and effective therapeutic interventions.

The Chikungunya virus (CHIKV) has infected millions of people worldwide and presents a serious public health issue. Acute symptomatic infections caused by contracting this mosquito-transmitted arbovirus are typically associated with an abrupt onset of fever and often debilitating polyarthralgia/ polyarthritis, as well as prolonged periods of disability in some patients. These dramatic effects call for a careful evaluation of the molecular mechanisms involved in this puzzling infection. By analyzing the blood transcriptome of adults acutely infected with CHIKV, we were able to provide a detailed picture of the early molecular events induced by the infection. Additionally, the systems biology approach revealed genes that can be investigated extensively as probable therapeutic targets for the disease.

Requirement of type I interferon signaling for arthritis triggered by double-stranded RNA

OBJECTIVE

Arthralgias and overt arthritides are often associated with viral infections. Viral infections expose the infected host to proinflammatory double-stranded RNA (dsRNA), which can cause joint inflammation and is a potent activator of interferon-alpha (IFNalpha). The aim of this study was to determine the role of IFNalpha and dsRNA-related signaling molecules in the onset of joint inflammation induced by viral dsRNA.

METHODS

IFNalpha and different forms of RNA were injected into the knee joints of wild-type mice, mice lacking the type I interferon receptor (IFNAR(-/-)), and mice deficient in dsRNA-dependent protein kinase (PKR(-/-)). Histologic evidence of joint damage and the ability of splenocytes to produce cytokines in response to dsRNA or IFNalpha were assessed.

RESULTS

Viral dsRNA, but not short single-stranded RNA, induced arthritis. The arthritis was aggravated by intracellular delivery of dsRNA. The expression of PKR was not mandatory for dsRNA-induced joint inflammation. In contrast, IFNalpha/beta signaling was important for dsRNA-induced joint inflammation because IFNAR(-/-) mice did not develop arthritis. Furthermore, intraarticular deposition of IFNalpha induced arthritis in PKR(-/-) and control mice, whereas IFNAR(-/-) mice were protected. The arthritogenic effect of IFNalpha was attenuated by in vivo depletion of monocyte/macrophages.

CONCLUSION

Arthritis triggered by dsRNA is not dependent on the expression of the dsRNA-signaling molecule PKR (or Toll-like receptor 3, as previously shown), but is associated with the ability to produce type I IFN and is critically dependent on type I IFN receptor signaling. The intrinsic arthritogenic properties of IFNalpha implicate a role of this cytokine in joint manifestations triggered by various interferogenic stimuli.

Persistence of parvovirus B19 DNA in synovium of patients with haemophilic arthritis

A progressive arthropathy develops commonly in haemophiliacs and its pathogenesis is not fully understood. Human parvovirus B19 has been associated with several diseases including acute and chronic arthropathy and some studies suggest its implication in chronic inflammatory diseases of the joints such as rheumatoid arthritis. In haemophiliacs parvovirus B19 infection occurs very frequently because of its transmission with plasma derivatives. In order to assess a role of B19 virus in haemophilic arthritis, synovial tissue samples from patients with haemophilia with arthritis and from patients, nonhaemophiliacs, with arthrosis or with joint trauma were examined for B19 DNA by nested PCR. In addition, the prevalence of antibody to parvovirus B19 NS1 protein as a possible serological marker of persistent B19 infection was tested and the association of the outcome of parvovirus infection with genetic diversity of B19 P6 promoter sequences was investigated. B19 DNA was detected in the synovial tissue of 31% of haemophiliacs with progressive arthropathy and of 5% of control patients. Fourteen out of 17 patients (82%) with haemophilic arthritis and with B19 DNA in their synovial membranes had IgG antibodies against the nonstructural protein NS1 of parvovirus B19. On the other hand, 19% of patients with haemophilia with B19 PCR negative synovial tissue and 21% of controls showed anti-NS1 antibodies. The P6 promoter presented specific sites of point mutations shared frequently by isolates from patients with haemophilia and arthritis. These results indicate that B19 DNA can persist in the synovial membranes of patients with haemophilic arthritis significantly more frequently in comparison to control individuals with arthrosis or joint trauma and show a correlation between anti- NS1 antibody presence and B19 DNA persistence in the synovial tissue.

Management of hepatitis C virus-related arthritis

Hepatitis C virus (HCV) infection is often associated with extrahepatic manifestations among which arthropathy is common, affecting up to 20% of HCV-infected individuals. This arthropathy is to be distinguished from the more superficially prominent myalgias and fatigue. HCV-related arthritis is commonly presented as rheumatoid-like, symmetrical inflammatory polyarthritis involving mainly small joints, or, less commonly, as mono- or oligoarthritis, usually of the large joints. HCV arthritis usually runs a relatively benign course that, in contrast to 'true' rheumatoid arthritis (RA), is typically non-deforming and is not associated with articular bony erosions. In addition, unlike 'classic' RA, erythrocyte sedimentation rate is elevated only in about half of the patients and subcutaneous nodules are absent. In about two-thirds of the affected individuals morning stiffness may be severe, resolving after more than an hour. Several pathogenetic mechanisms may be involved: HCV arthritis may be part of the syndrome of mixed cryoglobulinaemia, or may be directly or indirectly mediated by HCV. Such possible, but yet not proven, mechanisms include direct invasion of synovial cells by the virus eliciting local inflammatory response, cytokine-induced disease or immune complex disease, particularly in genetically susceptible individuals. The diagnosis of HCV arthritis in patients with positive rheumatoid factor and chronic inflammatory polyarthritis may be difficult. Positive HCV antibody and HCV RNA, and the absence of bony erosions, subcutaneous nodules and antikeratin antibodies, may be useful in distinguishing between HCV-related arthritis and RA. The optimal treatment of HCV-related arthritis has not yet been established. Concerns may be raised regarding the use of immunosuppressive or potentially hepatotoxic drugs. However, it may be suggested that once the diagnosis of HCV-associated arthritis is made, combination antiviral treatment with interferon-alpha and ribavirin should be initiated as part of the therapeutic armamentarium. Low dose oral corticosteroids, nonsteroidal anti-inflammatory drugs, hydroxychloroquine or sulfasalazine in addition to the antiviral therapy can be used to control arthritis-related symptoms. Some patients may need long term anti-inflammatory treatment in various combinations, along with antiviral therapy. In patients with severe, disabling or life-threatening cryoglobulinaemia-related symptoms refractory to antiviral or anti-inflammatory treatment, high dose corticosteroids (including pulse therapy) and/or plasmapheresis may be needed.

Animal model of arthritis and myositis induced by the Mayaro virus

BACKGROUND

The Mayaro virus (MAYV) is an endemic arbovirus in South American countries, where it is responsible for sporadic outbreaks of Mayaro fever. Clinical manifestations include fever, headache, ocular pain, rash, myalgia, and debilitating and persistent polyarthralgia. Understanding the mechanisms associated with MAYV-induced arthritis is of great importance due to the potential for its emergence, urbanization and dispersion to other regions.

METHODS

15-day old Balb/c mice were infected by two distinct pathways, below the forelimb and in the rear footpad. Animals were observed for a period of 21 days. During this time, they were monitored every 24 hours for disease signs, such as weight loss and muscle weakness. Histological damage in the muscles and joints was evaluated 3, 7, 10, 15 and 20 days post-infection. The cytokine profile in serum and muscles during MAYV infection was evaluated by flow cytometry at different post-infection times. For pain analysis, the animals were submitted to the von Frey test and titre in different organs was evaluated throughout the study to obtain viral kinetics.

FINDINGS

Infection by two distinct pathways, below the forelimb and in the rear footpad, resulted in a homogeneous viral spread and the development of acute disease in animals. Clinical signs were observed such as ruffled fur, hunched posture, eye irritation and slight gait alteration. In the physical test, both groups presented loss of resistance, which was associated with histopathological damage, including myositis, arthritis, tenosynovitis and periostitis. The immune response was characterized by a strong inflammatory response mediated by the cytokines TNF-α, IL-6 and INF-γ and chemokine MCP-1, followed by the action of IL-10 and IL-4 cytokines.

INTERPRETATION

The results showed that Balb/c mice represent a promising model to study mechanisms involved in MAYV pathogenesis and for future antiviral testing.

Prime-boost vaccination with plasmid DNA encoding caprine-arthritis encephalitis lentivirus env and viral SU suppresses challenge virus and development of arthritis

This study evaluated the efficacy of prime-boost vaccination for immune control of caprine arthritis-encephalitis virus (CAEV), a macrophage tropic lentivirus that causes progressive arthritis in the natural host. Vaccination of Saanen goats with pUC-based plasmid DNA expressing CAEV env induces T helper type 1 (Th1) biased immune responses to vector-encoded surface envelope (SU), and the plasmid-primed Th1 response is expanded following boost with purified SU in Freund's incomplete adjuvant (SU-FIA) (J. C. Beyer et al., 2001, Vaccine 19, 1643-1651). Four goats vaccinated with env expression plasmids and boosted with SU-FIA were challenged intravenously with 1 x 10(4) TCID(50) of CAEV at 428 days after SU-FIA boost and evaluated by immunological, virological, and disease criteria. Controls included two goats primed with pUC18 and eight unvaccinated goats. Goats receiving prime-boost vaccination with CAEV env plasmids and SU-FIA became infected but suppressed postchallenge virus replication, provirus loads in lymph node, and development of arthritis for at least 84 weeks.

Arthritis syndromes associated with human T cell lymphotropic virus type I infection

Arthritis syndromes occur associated with HTLV-I infection both in the presence and in the absence of clinical ATL, and polyarthritis may be the presenting manifestation of HTLV-I-associated ATL. In both clinical settings, HTLV-I-infected T cells home to affected joints, and tax-transgenic mouse studies have suggested a pathogenic role for the HTLV-I tax gene in inducing synovial cell proliferation in HAA. Understanding the pathogenesis of rheumatoid arthritis-like arthritis syndromes that occur in the setting of HTLV-I infection should also provide insights into understanding of cellular and molecular mechanisms of synovial cell proliferation in HTLV-I-negative rheumatoid arthritis.