Autoimmunity to synovial extracellular matrix proteins in patients with postinfectious Lyme arthritis.

BACKGROUNDAutoimmune diseases often have strong genetic associations with specific HLA-DR alleles. The synovial lesion in chronic inflammatory forms of arthritis shows marked upregulation of HLA-DR molecules, including in postinfectious Lyme arthritis (LA). However, the identity of HLA-DR-presented peptides, and therefore the reasons for these associations, has frequently remained elusive.METHODSUsing immunopeptidomics to detect HLA-DR-presented peptides from synovial tissue, we identified T cell epitopes from 3 extracellular matrix (ECM) proteins in patients with postinfectious LA, identified potential Borreliella burgdorferi-mimic (Bb-mimic) epitopes, and characterized T and B cell responses to these peptides or proteins.RESULTSOf 24 postinfectious LA patients, 58% had CD4+ T cell responses to at least 1 epitope of 3 ECM proteins, fibronectin-1, laminin B2, and/or collagen Vα1, and 17% of 52 such patients had antibody responses to at least 1 of these proteins. Patients with autoreactive T cell responses had significantly increased frequencies of HLA-DRB1*04 or -DRB1*1501 alleles and more prolonged arthritis. When tetramer reagents were loaded with ECM or corresponding Bb-mimic peptides, binding was only with the autoreactive T cells. A high percentage of ECM-autoreactive CD4+ T cells in synovial fluid were T-bet-expressing Th1 cells, a small percentage were RoRγt-expressing Th17 cells, and a minimal percentage were FoxP3-expressing Tregs.CONCLUSIONAutoreactive, proinflammatory CD4+ T cells and autoantibodies develop to ECM proteins in a subgroup of postinfectious LA patients who have specific HLA-DR alleles. Rather than the traditional molecular mimicry model, we propose that epitope spreading provides the best explanation for this example of infection-induced autoimmunity.FUNDINGSupported by National Institute of Allergy and Infectious Diseases R01-AI101175, R01-AI144365, and F32-AI125764; National Institute of Arthritis and Musculoskeletal and Skin Diseases K01-AR062098 and T32-AR007258; NIH grants P41-GM104603, R24-GM134210, S10-RR020946, S10-OD010724, S10-OD021651, and S10-OD021728; and the G. Harold and Leila Y. Mathers Foundation, the Eshe Fund, and the Lyme Disease and Arthritis Research Fund at Massachusetts General Hospital.

Cell-Mediated Cytotoxicity in Lyme Arthritis.

OBJECTIVE: Obliterative microvascular lesions are found in the synovial tissue of ~50% of patients with post-antibiotic Lyme arthritis (LA) and correlate with autoantibodies to certain vascular antigens. In this study, we identified lymphocytes with cytotoxic potential that may also mediate this feature of synovial pathology. METHODS: The cytotoxic potential of lymphocytes and their T cell receptor (TCR) Vß gene usage were determined using samples of peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) from patients with antibiotic-responsive or post-antibiotic LA. Cell phenotypes were analyzed using flow cytometry and intracellular cytokine staining. Immunohistochemistry was performed on post-antibiotic synovial tissue samples. RESULTS: In SFMC and PBMC samples, the percentages of CD8+ T cells and double-negative T cells (primarily γδ T cells) were greater among 22 patients with post-antibiotic LA than in 14 patients with antibiotic-responsive LA. Moreover, CD8+ T cells and γδ T cells often expressed cytotoxic mediators, granzyme A/granzyme B, and perforin. The same 3 TCR Vß segments were over-represented in both CD4+ T cells and CD8+ T cells in SFMC samples from post-antibiotic LA patients. In synovial tissue samples from 3 patients with post-antibiotic LA, CD8+ T cells intermixed with CD4+ T cells were seen around blood vessels, and 2 patients with microvascular damage had autoantibodies to vascular-associated antigens. One of these 2 patients, the one in whom cytotoxicity appeared to be active, had complement (C5b-9) deposition on obliterated vessels. Very few natural killer cells or γδ T cells were seen. CONCLUSION: We propose that CD8+ T cell-mediated cytotoxicity, CD4+ T cell help, autoantibodies to vascular antigens, and complement deposition may each have a role in microvasculature damage in post-antibiotic LA.

Lyme Arthritis.

Arthritis is the most common late manifestation of Borrelia burgdorferi infection in the United States, usually beginning months after the tick bite. In most patients with Lyme arthritis (LA) today, arthritis is the presenting manifestation of the disease. Patients have swelling and pain in one or a few large joints, especially the knee. Serologic testing is the mainstay of diagnosis. Responses to antibiotic treatment are generally excellent, although a small percentage of patients have persistent, postinfectious synovitis after 2 to 3 months of oral and IV antibiotics, which respond to anti-inflammatory therapies. Herein we review the clinical presentation, diagnosis, and management of LA.

Lyme arthritis: linking infection, inflammation and autoimmunity.

Infectious agents can trigger autoimmune responses in a number of chronic inflammatory diseases. Lyme arthritis, which is caused by the tick-transmitted spirochaete Borrelia burgdorferi, is effectively treated in most patients with antibiotic therapy; however, in a subset of patients, arthritis can persist and worsen after the spirochaete has been killed (known as post-infectious Lyme arthritis). This Review details the current understanding of the pathogenetic events in Lyme arthritis, from initial infection in the skin, through infection of the joints, to post-infectious chronic inflammatory arthritis. The central feature of post-infectious Lyme arthritis is an excessive, dysregulated pro-inflammatory immune response during the infection phase that persists into the post-infectious period. This response is characterized by high amounts of IFNγ and inadequate amounts of the anti-inflammatory cytokine IL-10. The consequences of this dysregulated pro-inflammatory response in the synovium include impaired tissue repair, vascular damage, autoimmune and cytotoxic processes, and fibroblast proliferation and fibrosis. These synovial characteristics are similar to those in other chronic inflammatory arthritides, including rheumatoid arthritis. Thus, post-infectious Lyme arthritis provides a model for other chronic autoimmune or autoinflammatory arthritides in which complex immune responses can be triggered and shaped by an infectious agent in concert with host genetic factors.

Identification of Novel, Immunogenic HLA-DR-Presented Prevotella copri Peptides in Patients With Rheumatoid Arthritis.

OBJECTIVE: We previously identified HLA-DR-presented epitopes from a 27-kd protein of Prevotella copri (Pc) obtained from peripheral blood mononuclear cells (PBMCs) from 1 rheumatoid arthritis (RA) patient. Herein, we sought to identify other HLA-DR-presented Pc peptides and source proteins in PBMCs from additional patients to better understand Pc immune responses and RA disease pathogenesis. METHODS: Using tandem mass spectrometry, we searched for HLA-DR-presented Pc peptides in PBMCs from RA and Lyme arthritis (LA) patients. The identified peptides and source proteins were tested for reactivity in RA patients, those with other arthritides, and the general population. These results were assessed for correlation with clinical findings. RESULTS: Including Pc-p27, we identified 5 HLA-DR-presented Pc peptides, each derived from a different Pc protein, in 3 of 4 RA patients, but none in 2 LA patients. When tested in our RA cohort, 14 of 19 patients (74%) had T cell responses, and 47 of 89 patients (53%) had IgG or IgA responses to ≥1 of the 5 Pc peptides or proteins, most commonly IgA reactivity with Pc-p27. Additionally, 74% of RA patients with IgA antibodies to ≥1 Pc protein had anti-citrullinated protein antibodies (ACPAs) compared with 49% of patients who lacked IgA Pc antibody responses (P = 0.05), and IgA Pc antibody levels correlated with ACPA values. CONCLUSION: The majority of the RA patients had Pc immune responses. The correlation of IgA Pc antibody responses, particularly to Pc-p27, with ACPA supports the hypothesis that specific microbial antigens in the mucosa have a role in shaping or amplifying immune responses in RA joints.

Periodontal inflammation and distinct inflammatory profiles in saliva and gingival crevicular fluid compared with serum and joints in rheumatoid arthritis patients.

BACKGROUND: The association of periodontitis and Porphyromonas gingivalis (Pg) with rheumatoid arthritis (RA) is incompletely understood. To gain further insights, we evaluated periodontal status, oral, serum and joint inflammatory profiles, and Pg biomarkers in RA patients. METHODS: In this cross-sectional study, we evaluated 33 patients with predominantly untreated new-onset RA, 20 healthy individuals (HIs), and 20 non-RA chronic periodontitis patients. Thirteen mediators (IFN-γ, IL-10, IL-17A, IL-6, IL-8, CXCL10, TNF-α, CXCL13, IL-23, MMP-1, MMP-3, MMP-8, MMP-9) were measured in serum, synovial fluid, saliva and gingival crevicular fluid (GCF) by multiplex immunoassay. Serum Pg IgG antibodies and subgingival Pg DNA were determined. RESULTS: Most RA patients (91%) received routine dental care; only one currently smoked. Ten (30.3%) had periodontal health, 13 (39.4%) had gingivitis, and 10 (30.3%) had periodontitis. Th1 and innate immune responses predominated in serum. Many mediators were concentrated in joints, particularly IL-6, IL-8, and CXCL10. However, salivary and GCF profiles were more restricted, emphasizing neutrophilic inflammation (IL-8, MMP-8) and MMP-9. Compared with HI, most RA patients, regardless of periodontal status, had significantly elevated oral fluid levels of these mediators, with suppression of GCF IL-10, a pattern similar to non-RA periodontitis patients. Pg antibodies or DNA however were primarily associated with clinical periodontitis. CONCLUSIONS: Despite routine dental care, RA patients often had inflammation in oral fluids, but inflammatory profiles differed from serum and joints. Neutrophilic inflammatory profiles in oral fluids, regardless of periodontal status, suggests that gingival tissues are a common, and often unrecognized, site of extra-articular inflammation in RA.

Robust interferon signature and suppressed tissue repair gene expression in synovial tissue from patients with postinfectious, Borrelia burgdorferi-induced Lyme arthritis.

In most patients with Lyme arthritis (LA), antibiotic therapy results in Borrelia burgdorferi pathogen elimination, tissue repair, and return to homeostasis. However, despite spirochetal killing, some patients develop proliferative synovitis, characterised by synovial hyperplasia, inflammation, vascular damage, and fibrosis that persists for months to several years after antibiotic treatment, called postinfectious LA. In this study, we characterised the transcriptomes of postinfectious LA patients' synovial tissue, the target tissue of the immune response. High-throughput RNA sequencing to a depth of ~30 million reads per sample was used to profile gene expression in synovial tissue from 14 patients with postinfectious LA, compared with eight patients with other types of chronic inflammatory arthritis and five with minimally inflammatory osteoarthritis (OA). Synovium from postinfectious LA and other inflammatory arthritides shared gene signatures associated with antigen presentation, innate immune responses, and cell-mediated immune activation, whereas these responses were diminished in OA synovium. Unique to postinfectious LA was a particularly robust interferon-gamma (IFNγ) signature. Moreover, this heightened IFNγ signature inversely correlated with expression of genes involved in repair of damaged tissue, including genes associated with stromal cell proliferation and differentiation, neovascularisation, and extracellular matrix synthesis, which were markedly suppressed in postinfectious LA. Transcriptional observations were confirmed by cytokine profiling, histologic analyses, and clinical correlations. We propose that in patients with postinfectious LA, overexpression of IFNγ in synovium prevents appropriate repair of tissue damaged by B. burgdorferi infection, blocking return to tissue homeostasis long after completion of antibiotic therapy and resolution of active infection.

Interferon-gamma production in Lyme arthritis synovial tissue promotes differentiation of fibroblast-like synoviocytes into immune effector cells.

Lyme arthritis (LA), a late disease manifestation of Borrelia burgdorferi infection, usually resolves with antibiotic therapy. However, some patients develop proliferative synovitis lasting months to several years after spirochetal killing, called postinfectious LA. In this study, we phenotyped haematopoietic and stromal cell populations in the synovial lesion ex vivo and used these findings to generate an in vitro model of LA using patient-derived fibroblast-like synoviocytes (FLS). Ex vivo analysis of synovial tissue revealed high abundance of IFNγ-producing T cells and NK cells. Similar to marked IFNγ responses in tissue, postinfectious LA synovial fluid also had high levels of IFNγ. HLA-DR-positive FLS were present throughout the synovial lesion, particularly in areas of inflammation. FLS stimulated in vitro with B. burgdorferi, which were similar to conditions during infection, expressed 68 genes associated primarily with innate immune activation and neutrophil recruitment. In contrast, FLS stimulated with IFNγ, which were similar to conditions in the postinfectious phase, expressed >2,000 genes associated with pathogen sensing, inflammation, and MHC Class II antigen presentation, similar to the expression profile in postinfectious synovial tissue. Furthermore, costimulation of FLS with B. burgdorferi and IFNγ induced greater expression of IL-6 and other innate immune response proteins and genes than with IFNγ stimulation alone. These results suggest that B. burgdorferi infection, in combination with IFNγ, initiates the differentiation of FLS into a highly inflammatory phenotype. We hypothesise that overexpression of IFNγ by lymphocytes within synovia perpetuates these responses in the postinfectious period, causing proliferative synovitis and stalling appropriate repair of damaged tissue.

Two rheumatoid arthritis-specific autoantigens correlate microbial immunity with autoimmune responses in joints.

In rheumatoid arthritis (RA), immunological triggers at mucosal sites, such as the gut microbiota, may promote autoimmunity that affects joints. Here, we used discovery-based proteomics to detect HLA-DR-presented peptides in synovia or peripheral blood mononuclear cells and identified 2 autoantigens, N-acetylglucosamine-6-sulfatase (GNS) and filamin A (FLNA), as targets of T and B cell responses in 52% and 56% of RA patients, respectively. Both GNS and FLNA were highly expressed in synovia. GNS appeared to be citrullinated, and GNS antibody values correlated with anti-citrullinated protein antibody (ACPA) levels. FLNA did not show the same results. The HLA-DR-presented GNS peptide has marked sequence homology with epitopes from sulfatase proteins of the Prevotella sp. and Parabacteroides sp., whereas the HLA-DR-presented FLNA peptide has homology with epitopes from proteins of the Prevotella sp. and Butyricimonas sp., another gut commensal. Patients with T cell reactivity with each self-peptide also had responses to the corresponding microbial peptides, and the levels were directly correlated. Furthermore, HLA-DR molecules encoded by shared-epitope (SE) alleles were predicted to bind these self- and microbial peptides strongly, and these responses were more common in RA patients with SE alleles. Thus, sequence homology between T cell epitopes of 2 self-proteins and a related order of gut microbes may provide a link between mucosal and joint immunity in patients with RA.

MicroRNA Expression Shows Inflammatory Dysregulation and Tumor-Like Proliferative Responses in Joints of Patients With Postinfectious Lyme Arthritis.

OBJECTIVE: Lyme arthritis (LA) is caused by infection with Borrelia burgdorferi and usually resolves following spirochetal killing with antibiotics. However, in some patients, arthritis persists after antibiotic therapy. To provide insights into underlying pathogenic processes associated with antibiotic-refractory LA (postinfectious LA), we analyzed differences in microRNA (miRNA) expression between LA patients with active infection and those with postinfectious LA. METHODS: MicroRNA expression was assayed in synovial fluid (SF) from LA patients before and after oral and intravenous antibiotic therapy, and in synovial tissue obtained months after antibiotic therapy from patients with postinfectious LA. SF and tissue from patients with other forms of arthritis, such as rheumatoid arthritis (RA) and osteoarthritis, were used for comparison. RESULTS: SF from LA patients during active infection had marked elevations of white blood cells, particularly polymorphonuclear leukocytes, accompanied by elevated levels of microRNA-223 (miR-223). In contrast, SF from postantibiotic LA patients contained greater percentages of lymphocytes and mononuclear cells. SF from postantibiotic LA patients also exhibited marked inflammatory (miR-146a, miR-155), wound repair (miR-142), and proliferative (miR-17-92) miRNA signatures, and higher levels of these miRNAs correlated with longer arthritis duration. Levels of miR-146a, miR-155, miR-142, miR-223, and miR-17-92 were also elevated in synovial tissue in late postinfectious LA, and levels of let-7a were reduced, similar to RA. CONCLUSION: During active infection, miRNA expression in SF reflected an immune response associated with bacterial killing, while in postinfectious LA, miRNA expression in SF and synovial tissue reflected chronic inflammation, synovial proliferation, and breakdown of wound repair processes, showing that the nature of the arthritis was altered after spirochetal killing.

T-Helper 17 Cell Cytokine Responses in Lyme Disease Correlate With Borrelia burgdorferi Antibodies During Early Infection and With Autoantibodies Late in the Illness in Patients With Antibiotic-Refractory Lyme Arthritis.

BACKGROUND: Control of Lyme disease is attributed predominantly to innate and adaptive T-helper 1 cell (TH1) immune responses, whereas the role of T-helper 17 cell (TH17) responses is less clear. Here we characterized these inflammatory responses in patients with erythema migrans (EM) or Lyme arthritis (LA) to elucidate their role early and late in the infection. METHODS: Levels of 21 cytokines and chemokines, representative of innate, TH1, and TH17 immune responses, were assessed by Luminex in acute and convalescent sera from 91 EM patients, in serum and synovial fluid from 141 LA patients, and in serum from 57 healthy subjects. Antibodies to Borrelia burgdorferi or autoantigens were measured by enzyme-linked immunosorbent assay. RESULTS: Compared with healthy subjects, EM patients had significantly higher levels of innate, TH1, and TH17-associated mediators (P ≤ .05) in serum. In these patients, the levels of inflammatory mediators, particularly TH17-associated cytokines, correlated directly with B. burgdorferi immunoglobulin G antibodies (P ≤ .02), suggesting a beneficial role for these responses in control of early infection. Late in the disease, in patients with LA, innate and TH1-associated mediators were often >10-fold higher in synovial fluid than serum. In contrast, the levels of TH17-associated mediators were more variable, but correlated strongly with autoantibodies to endothelial cell growth factor, matrix metalloproteinase 10, and apolipoprotein B-100 in joints of patients with antibiotic-refractory LA, implying a shift in TH17 responses toward an autoimmune phenotype. CONCLUSIONS: Patients with Lyme disease often develop pronounced TH17 immune responses that may help control early infection. However, late in the disease, excessive TH17 responses may be disadvantageous by contributing to autoimmune responses associated with antibiotic-refractory LA.

Granulomatous skin involvement in a patient with an unusual NOD2 mutation.

Blau syndrome is a rare disorder that is classically characterised by granulomatous arthritis, skin eruptions and uveitis, which occur in the absence of lung involvement. Blau syndrome has been linked to encoding mutations in the NOD-2 gene and is inherited in an autosomal dominant form. The most commonly observed mutations are missense substitutions affecting the arginine residue at position 334. The rare E600A mutation has been described as causing uveitis without skin involvement. Our patient is a 54-year-old man with an unusual heterozygous c.1799A>C(E600A) mutation, who was seen for bilateral lower extremity swelling and pain. On physical examination, he was found to have lower leg oedema with decreased hair growth on the affected area. Biopsy showed non-caseating micro-granulomas consistent with a diagnosis of Blau syndrome. The patient had excellent response to colchicine, but this was stopped because he developed elevated transaminases. Thus, we present an unusual genetic form of a rare condition and we demonstrate skin involvement in a subtype where cutaneous involvement has not hitherto been reported. In addition, the type and presentation of the skin involvement is different from that normally found in classic Blau syndrome. Finally, we report his response to colchicine, although it was ultimately not tolerated by this patient.

Autoimmune Arthritides, Rheumatoid Arthritis, Psoriatic Arthritis, or Peripheral Spondyloarthritis Following Lyme Disease.

OBJECTIVE: To describe systemic autoimmune joint diseases that develop following Lyme disease, and to compare their clinical features with those of Lyme arthritis (LA). METHODS: We reviewed records of all adult patients referred to our LA clinic over a 13-year period, in whom we had diagnosed a systemic autoimmune joint disease following Lyme disease. For comparison, records of patients enrolled in our LA cohort over the most recent 2-year period were analyzed. Levels of IgG antibodies to Borrelia burgdorferi and to 3 Lyme disease-associated autoantigens were measured. RESULTS: We identified 30 patients who had developed a new-onset systemic autoimmune joint disorder a median of 4 months after Lyme disease (usually manifested by erythema migrans [EM]). Fifteen had rheumatoid arthritis (RA), 13 had psoriatic arthritis (PsA), and 2 had peripheral spondyloarthritis (SpA). The 30 patients typically had polyarthritis, and those with PsA or SpA often had previous psoriasis, axial involvement, or enthesitis. In the comparison group of 43 patients with LA, the usual clinical picture was monoarticular knee arthritis, without prior EM. Most of the patients with systemic autoimmune joint disorders were positive for B burgdorferi IgG antibodies, as detected by enzyme-linked immunosorbent assay, but had significantly lower titers and lower frequencies of Lyme disease-associated autoantibodies than patients with LA. Prior to our evaluation, these patients had often received additional antibiotics for presumed LA, without benefit. We prescribed antiinflammatory agents, most commonly disease-modifying antirheumatic drugs, resulting in improvement. CONCLUSION: Systemic autoimmune joint diseases (i.e., RA, PsA, SpA) may follow Lyme disease. Development of polyarthritis after antibiotic-treated EM, previous psoriasis, or low-titer B burgdorferi antibodies may provide insight into the correct diagnosis.

Evidence of the Immune Relevance of Prevotella copri, a Gut Microbe, in Patients With Rheumatoid Arthritis.

OBJECTIVE: Prevotella copri, an intestinal microbe, may overexpand in stool samples from patients with new-onset rheumatoid arthritis (RA), but it is not yet clear whether the organism has immune relevance in RA pathogenesis. METHODS: HLA-DR-presented peptides (T cell epitopes) from P copri were sought directly in the patients' synovial tissue or peripheral blood mononuclear cell (PBMC) samples using tandem mass spectrometry. The antigenicity of peptides or their source proteins was examined in samples from the RA patients or comparison groups. T cell reactivity was determined by enzyme-linked immunospot assay; antibody responses were measured by enzyme-linked immunosorbent assay, and cytokine/chemokine determinations were made by bead-based assays. Serum and synovial fluid samples were examined for 16S ribosomal DNA for P copri using nested polymerase chain reaction analysis. RESULTS: In PBMCs, we identified an HLA-DR-presented peptide from a 27-kd protein of P copri (Pc-p27), which stimulated Th1 responses in 42% of patients with new-onset RA. In both new-onset RA patients and chronic RA patients, 1 subgroup had IgA antibody responses to either Pc-p27 or the whole organism, which correlated with Th17 cytokine responses and frequent anti-citrullinated protein antibodies (ACPAs). The other subgroup had IgG P copri antibodies, which were associated with Prevotella DNA in synovial fluid, P copri-specific Th1 responses, and less frequent ACPAs. In contrast, P copri antibody responses were rarely found in patients with other rheumatic diseases or in healthy controls. CONCLUSION: Subgroups of RA patients have differential IgG or IgA immune reactivity with P copri, which appears to be specific for this disease. These observations provide evidence that P copri is immune-relevant in RA pathogenesis.

Matrix metalloproteinase-10 is a target of T and B cell responses that correlate with synovial pathology in patients with antibiotic-refractory Lyme arthritis.

Infection-induced autoimmunity is thought to be a contributing factor in antibiotic-refractory Lyme arthritis, but studies of autoimmunity have been hindered by difficulty in identifying relevant autoantigens. We developed a novel approach that begins with the identification of T cell epitopes in synovial tissue using tandem mass spectrometry. Herein, we identified an immunogenic HLA-DR-presented peptide (T cell epitope) derived from the source protein matrix metalloproteinase-10 (MMP-10) from the synovium of a patient with antibiotic-refractory arthritis. This finding provided a bridge for the identification of autoantibody responses to MMP-10, the "first autoimmune hit" in a subgroup of patients with erythema migrans, the initial skin lesion of the infection. Months later, after priming of the immune response to MMP-10 in early infection, a subset of patients with antibiotic-responsive or antibiotic-refractory arthritis had MMP-10 autoantibodies, but only patients with antibiotic-refractory arthritis had both T and B cell responses to the protein, providing evidence for a "second autoimmune hit". Further support for a biologically relevant autoimmune event was observed by the positive correlation of anti-MMP-10 autoantibodies with distinct synovial pathology. This experience demonstrates the power of new, discovery-based methods to identify relevant autoimmune responses in chronic inflammatory forms of arthritis.