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

Anti-RA33 Antibodies Are Present in Patients With Lyme Disease

BACKGROUND/OBJECTIVE

To determine if anti-RA33 antibodies, which can be seen in early forms of inflammatory arthritis, are present in patients with Lyme arthritis (LA).

METHODS

Anti-RA33 antibodies were tested using a commercially available assay in patients with LA (n = 47) and compared with patients with erythema migrans who returned to health (EM RTH, n = 20) and those with post-treatment Lyme disease (PTLD) (n = 50), characterized by noninflammatory arthralgia, as an observational comparative study utilizing Lyme-exposed patients from various original cohorts.

RESULTS

We found that anti-RA33 was present in higher proportions of patients with LA (23.4% vs. 0%, p = 0.001) and PTLD (12.0% vs. 0%, p = 0.040) than healthy controls. There was also a trend toward a higher percentage of anti-RA33 positivity in patients with EM RTH versus controls (10.0% vs. 0%, p = 0.080). There were no statistically significant differences among groups of patients with LA, PTLD, and EM RTH ( p ≥ 0.567). There was also no difference in the proportion of patients with antibiotic-responsive LA compared with those with persistent synovitis after antibiotics, termed post-infectious LA, and there were no differences in clinical manifestations, musculoskeletal ultrasound evaluation (synovial hypertrophy, power Doppler, tendinopathy), or patient-reported outcomes based on anti-RA33 status.

CONCLUSIONS

This is the first study to identify anti-RA33 antibodies in patients with LA, though these antibodies did not identify a unique clinical subset of patients in this cohort. Unexpectedly, we found anti-RA33 antibodies at similar levels in patients with PTLD and EM RTH; further study is needed to determine the relevance of this finding.

Proposed Immunopathogenetic Mechanisms Underlying Lyme Arthritis

ABSTRACT

Lyme disease is commonly associated with musculoskeletal features, inflammatory and noninflammatory. The precise pathogenesis of the clinical features of this infection are complex and often multiple. A better understanding of how Borrelia burgdorferi causes these musculoskeletal manifestations is necessary in order to determine the proper treatment and eschew that which is unlikely to work, often associated with toxicities. The following review seeks to summarize the various immunopathogenic mechanisms that may cause these features of Lyme disease and suggests a series of approaches based on the most likely underlying mechanism(s).

Bridging the gap: Insights in the immunopathology of Lyme borreliosis

Lyme borreliosis (LB), caused by Borrelia burgdorferi sensu lato (Bbsl) genospecies transmitted by Ixodes spp. ticks, is a significant public health concern in the Northern Hemisphere. This review highlights the complex interplay between Bbsl infection and host-immune responses, impacting clinical manifestations and long-term immunity. Early localized disease is characterized by erythema migrans (EM), driven by T-helper 1 (Th1) responses and proinflammatory cytokines. Dissemination to the heart and CNS can lead to Lyme carditis and neuroborreliosis respectively, orchestrated by immune cell infiltration and chemokine dysregulation. More chronic manifestations, including acrodermatitis chronica atrophicans and Lyme arthritis, involve prolonged inflammation as well as the development of autoimmunity. In addition, dysregulated immune responses impair long-term immunity, with compromised B-cell memory and antibody responses. Experimental models and clinical studies underscore the role of Th1/Th2 balance, B-cell dysfunction, and autoimmunity in LB pathogenesis. Moreover, LB-associated autoimmunity parallels mechanisms observed in other infectious and autoimmune diseases. Understanding immune dysregulation in LB provides insights into disease heterogeneity and could provide new strategies for diagnosis and treatment.

HLA-DR-Expressing Fibroblast-Like Synoviocytes Are Inducible Antigen Presenting Cells That Present Autoantigens in Lyme Arthritis

OBJECTIVE

HLA-DR-expressing fibroblast-like synoviocytes (FLS) are a prominent cell type in synovial tissue in chronic inflammatory forms of arthritis. FLS-derived extracellular matrix (ECM) proteins, including fibronectin-1 (FN1), contain immunogenic CD4+ T cell epitopes in patients with postinfectious Lyme arthritis (LA). However, the role of FLS in presentation of these T cell epitopes remains uncertain.

METHODS

Primary LA FLS and primary murine FLS stimulated with interferon gamma (IFNγ), Borrelia burgdorferi, and/or B burgdorferi peptidoglycan (PG) were assessed for properties associated with antigen presentation. HLA-DR-presented peptides from stimulated LA FLS were identified by immunopeptidomics analysis. OT-II T cells were co-cultured with stimulated murine FLS in the presence of cognate ovalbumin antigen to determine the potential of FLS to act as inducible antigen presenting cells (APCs).

RESULTS

FLS expressed HLA-DR molecules within inflamed synovial tissue and tendons from patients with postinfectious LA in situ. Major histocompatibility complex (MHC) class II and co-stimulatory molecules were expressed by FLS following in vitro stimulation with IFNγ and B burgdorferi and presented both foreign and self-MHC-II peptides, including an immunogenic T cell epitope derived from Lyme autoantigen FN1. Stimulated FLS induced proliferation of naive OT-II CD4+ T cells that were dependent on OT-II antigen and CD40. Stimulation with B burgdorferi PG enhanced FLS-mediated T cell activation.

CONCLUSION

MHC-II+ FLS are inducible APCs that can induce CD4+ T cell activation in an antigen- and CD40-dependent manner. Activated FLS can also present ECM-derived Lyme autoantigens, implicating FLS in amplifying tissue-localized autoimmunity in LA.

Variants in the Late Cornified Envelope Gene Locus Are Associated With Elevated T-helper 17 Responses in Patients With Postinfectious Lyme Arthritis

BACKGROUND

Postinfectious Lyme arthritis (LA) is associated with dysregulated immunity and autoreactive T- and B-cell responses in joints. Here we explored the role of host genetic variation in this outcome.

METHODS

The frequency of 253 702 single-nucleotide polymorphisms (SNPs) was determined in 147 patients with LA (87 with postinfectious LA and 60 with antibiotic-responsive LA), and for comparison in 90 patients with erythema migrans or the general population (n = 2504). Functional outcome of candidate SNPs was assessed by evaluating their impact on clinical outcome and on immune responses in blood and synovial fluid in patients with LA.

RESULTS

Six SNPs associated with late cornified envelope (LCE3) genes were present at greater frequency in patients with postinfectious LA compared to those with antibiotic-responsive LA (70% vs 30%; odds ratio, 2; P < .01). These SNPs were associated with heightened levels of inflammatory Th17 cytokines in serum but lower levels of interleukin 27, a regulatory cytokine, implying that they may contribute to dysregulated Th17 immunity in blood. Moreover, in patients with postinfectious LA, the levels of these Th17 mediators correlated directly with autoantibody responses in synovial fluid, providing a possible link between LCE3 SNPs, maladaptive systemic Th17 immunity, and autoreactive responses in joints.

CONCLUSIONS

Variation in the LCE3 locus, a known genetic risk factor in psoriasis and psoriatic arthritis, is associated with dysregulated systemic Th17 immunity and heightened autoantibody responses in joints. These findings underscore the importance of host genetic predisposition and systemic Th17 immunity in the pathogenesis of postinfectious (antibiotic-refractory) Lyme arthritis.

Identification of Major Histocompatibility Complex Class II Epitopes From Lyme Autoantigen Apolipoprotein B-100 and Borrelia burgdorferi Mcp4 in Murine Lyme Arthritis

BACKGROUND

During infection with the Lyme arthritis (LA) pathogen Borrelia burgdorferi, T-cell responses to both host and pathogen are dysregulated, resulting in chronic infection and frequent development of autoimmunity.

METHODS

To assess CD4+ T-cell epitopes presented during development of LA, we used an unbiased, immunopeptidomics approach to characterize the major histocompatibility complex (MHC) class II immunopeptidome in B burgdorferi-infected C57BL/6 (B6) mice, which develop mild, self-limiting LA, and infected B6 Il10-/- mice, which develop severe, persistent LA at 0, 4, and 16 weeks postinfection (22-23 mice per group).

RESULTS

Peptides derived from proteins involved in adaptive T- and B-cell responses and cholesterol metabolism, including human Lyme autoantigen apolipoprotein B-100 (apoB-100), were enriched in infected Il10-/- mice; whereas peptides derived from proteins involved in neutrophil extracellular net formation were enriched in infected B6 mice. Presentation of apoB-100 peptides showed evidence of epitope expansion during infection. Of several identified B burgdorferi peptides, only 1, a methyl-accepting chemotaxis protein peptide Mcp4442-462, was immunogenic.

CONCLUSIONS

ApoB-100, a human Lyme autoantigen, undergoes marked epitope expansion during LA development. The paucity of immunogenic B burgdorferi epitopes supports previous findings suggesting CD4+ T-cell responses are suppressed in murine LA.

Lyme Arthritis: A 50-Year Journey

Lyme arthritis (LA) was recognized as a separate entity in 1975 because of geographic clustering of children often diagnosed with juvenile rheumatoid arthritis in Lyme, Connecticut. After identification of erythema migrans as a common early feature of the illness, a prospective study of such patients implicated Ixodes scapularis ticks in disease transmission. In 1982, the causative agent, now called Borrelia burgdorferi, was cultured from these ticks and from Lyme disease patients. Subsequently, it was shown that LA could usually be treated successfully with oral antibiotics but sometimes required intravenous antibiotics. Yet, a small percentage of patients developed a dysregulated, proinflammatory immune response leading to persistent postinfectious synovitis with vascular damage, cytotoxic and autoimmune responses, and fibroblast proliferation, a lesion similar to that of rheumatoid arthritis. The message from postinfectious LA for other autoimmune arthritides is that a complex immune response with autoimmune features can begin with a microbial infection.

Synthesis of a Borrelia burgdorferi-Derived Muropeptide Standard Fragment Library

The interplay between the human innate immune system and bacterial cell wall components is pivotal in understanding diseases such as Crohn's disease and Lyme arthritis. Lyme disease, caused by Borrelia burgdorferi, is the most prevalent tick-borne illness in the United States, with a substantial number of cases reported annually. While antibiotic treatments are generally effective, approximately 10% of Lyme disease cases develop persistent arthritis, suggesting a dysregulated host immune response. We have previously identified a link between the immunogenic B. burgdorferi peptidoglycan (PG) and Lyme arthritis and showed that this pathogen sheds significant amounts of PG fragments during growth. Here, we synthesize these PG fragments, including ornithine-containing monosaccharides and disaccharides, to mimic the unique composition of Borrelia cell walls, using reproducible and rigorous synthetic methods. This synthetic approach allows for the modular preparation of PG derivatives, providing a diverse library of well-defined fragments. These fragments will serve as valuable tools for investigating the role of PG-mediated innate immune response in Lyme disease and aid in the development of improved diagnostic methods and treatment strategies.

Disease-specific T cell receptors maintain pathogenic T helper cell responses in postinfectious Lyme arthritis

BACKGROUNDAntibiotic-Refractory Lyme Arthritis (ARLA) involves a complex interplay of T cell responses targeting Borrelia burgdorferi antigens progressing toward autoantigens by epitope spreading. However, the precise molecular mechanisms driving the pathogenic T cell response in ARLA remain unclear. Our aim was to elucidate the molecular program of disease-specific Th cells.METHODSUsing flow cytometry, high-throughput T cell receptor (TCR) sequencing, and scRNA-Seq of CD4+ Th cells isolated from the joints of patients with ARLA living in Europe, we aimed to infer antigen specificity through unbiased analysis of TCR repertoire patterns, identifying surrogate markers for disease-specific TCRs, and connecting TCR specificity to transcriptional patterns.RESULTSPD-1hiHLA-DR+CD4+ effector T cells were clonally expanded within the inflamed joints and persisted throughout disease course. Among these cells, we identified a distinct TCR-β motif restricted to HLA-DRB1*11 or *13 alleles. These alleles, being underrepresented in patients with ARLA living in North America, were unexpectedly prevalent in our European cohort. The identified TCR-β motif served as surrogate marker for a convergent TCR response specific to ARLA, distinguishing it from other rheumatic diseases. In the scRNA-Seq data set, the TCR-β motif particularly mapped to peripheral T helper (TPH) cells displaying signs of sustained proliferation, continuous TCR signaling, and expressing CXCL13 and IFN-γ.CONCLUSIONBy inferring disease-specific TCRs from synovial T cells we identified a convergent TCR response in the joints of patients with ARLA that continuously fueled the expansion of TPH cells expressing a pathogenic cytokine effector program. The identified TCRs will aid in uncovering the major antigen targets of the maladaptive immune response.FUNDINGSupported by the German Research Foundation (DFG) MO 2160/4-1; the Federal Ministry of Education and Research (BMBF; Advanced Clinician Scientist-Program INTERACT; 01EO2108) embedded in the Interdisciplinary Center for Clinical Research (IZKF) of the University Hospital Würzburg; the German Center for Infection Research (DZIF; Clinical Leave Program; TI07.001_007) and the Interdisciplinary Center for Clinical Research (IZKF) Würzburg (Clinician Scientist Program, Z-2/CSP-30).

Antigenicity and immunogenicity of different morphological forms of Borrelia burgdorferi sensu lato spirochetes

Borrelia burgdorferi sensu lato is a species complex of pleomorphic spirochetes, including species that cause Lyme disease (LD) in humans. In addition to classic spiral forms, these bacteria are capable of creating morphological forms referred to as round bodies and aggregates. The subject of discussion is their possible contribution to the persistence of infection or post-infection symptoms in LD. This study investigates the immunological properties of these forms by monitoring reactivity with early (n = 30) and late stage (n = 30) LD patient sera and evaluating the immune response induced by vaccination of mice. In patient sera, we found a quantitative difference in reactivity with individual morphotypes, when aggregates were recognized most intensively, but the difference was statistically significant in only half of the tested strains. In post-vaccination mouse sera, we observed a statistically significant higher reactivity with antigens p83 and p25 (OspC) in mice vaccinated with aggregates compared to mice vaccinated with spiral forms. The importance of the particulate nature of the antigen for the induction of a Th1-directed response has also been demonstrated. In any of morphological forms, the possibility of inducing antibodies cross-reacting with human nuclear and myositis specific/associated autoantigens was not confirmed by vaccination of mice.

Human leukocyte antigen HLA-DR-expressing fibroblast-like synoviocytes are inducible antigen presenting cells that present autoantigens in Lyme arthritis

Background

HLA-DR-expressing fibroblast-like synoviocytes (FLS) are a prominent cell type in synovial tissue in chronic inflammatory forms of arthritis. We recently showed that peptides from several extracellular matrix (ECM) proteins, including fibronectin-1 (FN1), contained immunogenic CD4+ T cell epitopes in patients with postinfectious Lyme arthritis (LA). However, the role of FLS in presentation of these T cell epitopes remains uncertain.

Methods

Primary LA FLS and primary murine FLS stimulated with interferon gamma (IFNγ), Borrelia burgdorferi, and/or B. burgdorferi peptidoglycan (PG) were assessed for properties associated with antigen presentation. HLA-DR-presented peptides from stimulated LA FLS were identified by immunopeptidomics analysis. OT-II T cells were cocultured with stimulated murine FLS in the presence of cognate ovalbumin antigen to determine the potential of FLS to act as inducible antigen presenting cells (APC).

Results

FLS expressed HLA-DR molecules within inflamed synovial tissue and tendons from patients with post-infectious LA patients in situ. MHC class II and costimulatory molecules were expressed by FLS following in vitro stimulation with IFNγ and B. burgdorferi and presented both foreign and self MHC-II peptides, including T cell epitopes derived from two Lyme autoantigens fibronectin-1 (FN1) and endothelial cell growth factor (ECGF). Stimulated murine FLS induced proliferation of naïve OT-II CD4+ T cells, particularly when FLS were stimulated with both IFNγ and PG.

Conclusions

MHC-II+ FLS are inducible APCs that can induce CD4+ T cell activation and can present Lyme autoantigens derived from ECM proteins, thereby amplifying tissue-localized autoimmune CD4+ T cell responses in LA.

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.

Anti-Inflammatory Effects of Dietary Polyphenols through Inhibitory Activity against Metalloproteinases

Matrix metalloproteinases (MMPs) are zinc-dependent metalloproteinases that play important roles in a variety of diseases, including cancer, cardiovascular disease, diabetes, obesity, and brain diseases. Dietary polyphenols are thought to have a variety of beneficial effects on these diseases characterized by inflammation. Clinical studies have demonstrated that MMPs are in most cases upregulated in various inflammatory diseases, including osteoarthritis, rheumatoid arthritis, inflammatory bowel disease, and Alzheimer's disease. Studies using patient-derived human samples, animal studies, and cellular experiments have suggested that polyphenols may be beneficial against inflammatory diseases by suppressing MMP gene expression and enzyme activity. One important mechanism by which polyphenols exert their activity is the downregulation of reactive oxygen species that promote MMP expression. Another important mechanism is the direct binding of polyphenols to MMPs and their inhibition of enzyme activity. Molecular docking analyses have provided a structural basis for the interaction between polyphenols and MMPs and will help to explore new polyphenol-based drugs with anti-inflammatory properties.

Lyme disease and the pursuit of a clinical cure

Lyme disease, caused by the spirochete Borrelia burgdorferi, is the most common vector-borne illness in the United States. Many aspects of the disease are still topics of controversy within the scientific and medical communities. One particular point of debate is the etiology behind antibiotic treatment failure of a significant portion (10-30%) of Lyme disease patients. The condition in which patients with Lyme disease continue to experience a variety of symptoms months to years after the recommended antibiotic treatment is most recently referred to in the literature as post treatment Lyme disease syndrome (PTLDS) or just simply post treatment Lyme disease (PTLD). The most commonly proposed mechanisms behind treatment failure include host autoimmune responses, long-term sequelae from the initial Borrelia infection, and persistence of the spirochete. The aims of this review will focus on the in vitro, in vivo, and clinical evidence that either validates or challenges these mechanisms, particularly with regard to the role of the immune response in disease and resolution of the infection. Next generation treatments and research into identifying biomarkers to predict treatment responses and outcomes for Lyme disease patients are also discussed. It is essential that definitions and guidelines for Lyme disease evolve with the research to translate diagnostic and therapeutic advances to patient care.

Improving Lyme disease testing with data driven test design in pediatrics

Diagnostic advances have not kept pace with the expansion of Lyme disease caused by Borrelia burgdorferi and transmitted by ticks. Lyme disease clinical manifestations can overlap with many other diagnoses making Lyme disease a critical part of many differential diagnoses in endemic areas. Current diagnostic blood tests rely on a 2-tiered algorithm for which the second step is either a time-consuming western blot or a whole cell lysate immunoassay. Neither of these second step tests allow for rapid results of this critical rule out test. We hypothesized that using western blot confirmation information, we could create computational models to propose recombinant second-tier tests that would allow for more rapid, automated, and specific testing algorithms. We propose here a framework for assessing retrospective data to determine putative recombinant assay components. A retrospective pediatric cohort of 2755 samples submitted for Lyme disease screening was assessed using support vector machine learning algorithms to optimize tier 1 diagnostic thresholds for the Vidas IgG II assay and determine optimal tier 2 components for both a positive and negative confirmation test. In cases where the tier 1 screen was negative, but clinical suspicion was high, we found that 1 protein (L58) could be used to reduce false-negative results. For second-tier testing of screen positive cases, we found that 6 proteins could be used to reduce false-positive results (L18, L39M, L39, L41, L45, and L58) with a final machine learning classifier or 2 proteins using a final rules-based approach (L41, L18). This led to an overall accuracy of 92.36% for the proposed algorithm without a final machine learning classifier and 92.12% with integration of the machine learning classifier in the final algorithm when compared to the IgG western blot as the gold-standard. Use of this framework across multiple assays and institutions will allow for a data-driven approach to assay development to provide laboratories and patients with the improvements in turnaround time needed for this testing.

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.

Tumor-reactive antibodies evolve from non-binding and autoreactive precursors

The tumor microenvironment hosts antibody-secreting cells (ASCs) associated with a favorable prognosis in several types of cancer. Patient-derived antibodies have diagnostic and therapeutic potential; yet, it remains unclear how antibodies gain autoreactivity and target tumors. Here, we found that somatic hypermutations (SHMs) promote antibody antitumor reactivity against surface autoantigens in high-grade serous ovarian carcinoma (HGSOC). Patient-derived tumor cells were frequently coated with IgGs. Intratumoral ASCs in HGSOC were both mutated and clonally expanded and produced tumor-reactive antibodies that targeted MMP14, which is abundantly expressed on the tumor cell surface. The reversion of monoclonal antibodies to their germline configuration revealed two types of classes: one dependent on SHMs for tumor binding and a second with germline-encoded autoreactivity. Thus, tumor-reactive autoantibodies are either naturally occurring or evolve through an antigen-driven selection process. These findings highlight the origin and potential applicability of autoantibodies directed at surface antigens for tumor targeting in cancer patients.

Seroprevalence of Antibodies against Tick-Borne Pathogens in Czech Patients with Suspected Post-Treatment Lyme Disease Syndrome

The hypothesized importance of coinfections in the pathogenesis of post-treatment Lyme disease syndrome (PTLDS) leads to the use of combined, ongoing antimicrobial treatment in many cases despite the absence of symptoms typical of the presence of infection with specific pathogens. Serum samples from 103 patients with suspected post-treatment Lyme disease syndrome were tested for the presence of antibodies to the major tick-borne pathogens Anaplasma phagocytophilum, Bartonella henselae/Bartonella quinatana, and Babesia microti. Although the presence of anti-Anaplasma antibodies was detected in 12.6% of the samples and anti-Bartonella antibodies in 9.7% of the samples, the presence of antibodies against both pathogens in the same samples or anti-Babesia antibodies in the selected group of patients could not be confirmed. However, we were able to detect autoantibodies, mostly antinuclear, in 11.6% of the patients studied. Our results are in good agreement with previously published studies showing the presence of a wide spectrum of autoantibodies in some patients with complicated forms of Lyme disease and post-treatment Lyme disease syndrome, but they do not reveal a significant influence of co-infections on the development of PTLDS in the studied group of patients.

Recent Progress in Lyme Disease and Remaining Challenges

Lyme disease (also known as Lyme borreliosis) is the most common vector-borne disease in the United States with an estimated 476,000 cases per year. While historically, the long-term impact of Lyme disease on patients has been controversial, mounting evidence supports the idea that a substantial number of patients experience persistent symptoms following treatment. The research community has largely lacked the necessary funding to properly advance the scientific and clinical understanding of the disease, or to develop and evaluate innovative approaches for prevention, diagnosis, and treatment. Given the many outstanding questions raised into the diagnosis, clinical presentation and treatment of Lyme disease, and the underlying molecular mechanisms that trigger persistent disease, there is an urgent need for more support. This review article summarizes progress over the past 5 years in our understanding of Lyme and tick-borne diseases in the United States and highlights remaining challenges.

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.

Matrix Metalloproteinase Inspired Therapeutic Strategies for Bone Diseases

Matrix Metalloproteinases (MMPs), as a family of zinc-containing enzymes, show the function of decomposing Extracellular Matrix (ECM) and participate in the physiological processes of cell migration, growth, inflammation, and metabolism. Clinical and experimental studies have indicated that MMPs play an essential role in tissue injury and repair as well as tumor diagnosis, metastasis, and prognosis. An increasing number of researchers have paid attention to their functions and mechanisms in bone health and diseases. The present review focuses on MMPs-inspired therapeutic strategies for the treatment of bone-related diseases. We introduce the role of MMPs in bone diseases, highlight the MMPs-inspired therapeutic options, and posit MMPs as a trigger for smart cell/drug delivery.

The peptidoglycan-associated protein NapA plays an important role in the envelope integrity and in the pathogenesis of the lyme disease spirochete

The bacterial pathogen responsible for causing Lyme disease, Borrelia burgdorferi, is an atypical Gram-negative spirochete that is transmitted to humans via the bite of an infected Ixodes tick. In diderms, peptidoglycan (PG) is sandwiched between the inner and outer membrane of the cell envelope. In many other Gram-negative bacteria, PG is bound by protein(s), which provide both structural integrity and continuity between envelope layers. Here, we present evidence of a peptidoglycan-associated protein (PAP) in B. burgdorferi. Using an unbiased proteomics approach, we identified Neutrophil Attracting Protein A (NapA) as a PAP. Interestingly, NapA is a Dps homologue, which typically functions to bind and protect cellular DNA from damage during times of stress. While B. burgdorferi NapA is known to be involved in the oxidative stress response, it lacks the critical residues necessary for DNA binding. Biochemical and cellular studies demonstrate that NapA is localized to the B. burgdorferi periplasm and is indeed a PAP. Cryo-electron microscopy indicates that mutant bacteria, unable to produce NapA, have structural abnormalities. Defects in cell-wall integrity impact growth rate and cause the napA mutant to be more susceptible to osmotic and PG-specific stresses. NapA-linked PG is secreted in outer membrane vesicles and augments IL-17 production, relative to PG alone. Using microfluidics, we demonstrate that NapA acts as a molecular beacon-exacerbating the pathogenic properties of B. burgdorferi PG. These studies further our understanding of the B. burgdorferi cell envelope, provide critical information that underlies its pathogenesis, and highlight how a highly conserved bacterial protein can evolve mechanistically, while maintaining biological function.

Lyme Disease in Humans

Lyme disease (Lyme borreliosis) is a tick-borne, zoonosis of adults and children caused by genospecies of the Borrelia burgdorferi sensu lato complex. The ailment, widespread throughout the Northern Hemisphere, continues to increase globally due to multiple environmental factors, coupled with increased incursion of humans into habitats that harbor the spirochete. B. burgdorferi sensu lato is transmitted by ticks from the Ixodes ricinus complex. In North America, B. burgdorferi causes nearly all infections; in Europe, B. afzelii and B. garinii are most associated with human disease. The spirochete's unusual fragmented genome encodes a plethora of differentially expressed outer surface lipoproteins that play a seminal role in the bacterium's ability to sustain itself within its enzootic cycle and cause disease when transmitted to its incidental human host. Tissue damage and symptomatology (i.e., clinical manifestations) result from the inflammatory response elicited by the bacterium and its constituents. The deposition of spirochetes into human dermal tissue generates a local inflammatory response that manifests as erythema migrans (EM), the hallmark skin lesion. If treated appropriately and early, the prognosis is excellent. However, in untreated patients, the disease may present with a wide range of clinical manifestations, most commonly involving the central nervous system, joints, or heart. A small percentage (~10%) of patients may go on to develop a poorly defined fibromyalgia-like illness, post-treatment Lyme disease (PTLD) unresponsive to prolonged antimicrobial therapy. Below we integrate current knowledge regarding the ecologic, epidemiologic, microbiologic, and immunologic facets of Lyme disease into a conceptual framework that sheds light on the disorder that healthcare providers encounter.

Immune Response to Borrelia: Lessons from Lyme Disease Spirochetes

The mammalian host responds to infection with Borrelia spirochetes through a highly orchestrated immune defense involving innate and adaptive effector functions aimed toward limiting pathogen burdens, minimizing tissue injury, and preventing subsequent reinfection. The evolutionary adaptation of Borrelia spirochetes to their reservoir mammalian hosts may allow for its persistence despite this immune defense. This review summarizes our current understanding of the host immune response to B. burgdorferi sensu lato, the most widely studied Borrelia spp. and etiologic agent of Lyme borreliosis. Pertinent literature will be reviewed with emphasis on in vitro, ex vivo and animal studies that influenced our understanding of both the earliest responses to B. burgdorferi as it enters the mammalian host and those that evolve as spirochetes disseminate and establish infection in multiple tissues. Our focus is on the immune response of inbred mice, the most commonly studied animal model of B. burgdorferi infection and surrogate for one of this pathogen's principle natural reservoir hosts, the white-footed deer mouse. Comparison will be made to the immune responses of humans with Lyme borreliosis. Our goal is to provide an understanding of the dynamics of the mammalian immune response during infection with B. burgdorferi and its relation to the outcomes in reservoir (mouse) and non-reservoir (human) hosts.

Lyme borreliosis: diagnosis and management

Lyme borreliosis is the most common vectorborne disease in the northern hemisphere. It usually begins with erythema migrans; early disseminated infection particularly causes multiple erythema migrans or neurologic disease, and late manifestations predominantly include arthritis in North America, and acrodermatitis chronica atrophicans (ACA) in Europe. Diagnosis of Lyme borreliosis is based on characteristic clinical signs and symptoms, complemented by serological confirmation of infection once an antibody response has been mounted. Manifestations usually respond to appropriate antibiotic regimens, but the disease can be followed by sequelae, such as immune arthritis or residual damage to affected tissues. A subset of individuals reports persistent symptoms, including fatigue, pain, arthralgia, and neurocognitive symptoms, which in some people are severe enough to fulfil the criteria for post-treatment Lyme disease syndrome. The reported prevalence of such persistent symptoms following antimicrobial treatment varies considerably, and its pathophysiology is unclear. Persistent active infection in humans has not been identified as a cause of this syndrome, and randomized treatment trials have invariably failed to show any benefit of prolonged antibiotic treatment. For prevention of Lyme borreliosis, post-exposure prophylaxis may be indicated in specific cases, and novel vaccine strategies are under development.

A joint effort: The interplay between the innate and the adaptive immune system in Lyme arthritis

Articular joints are a major target of Borrelia burgdorferi, the causative agent of Lyme arthritis. Despite antibiotic treatment, recurrent or persistent Lyme arthritis is observed in a significant number of patients. The host immune response plays a crucial role in this chronic arthritic joint complication of Borrelia infections. During the early stages of B. burgdorferi infection, a major hinder in generating a proper host immune response is the lack of induction of a strong adaptive immune response. This may lead to a delayed hyperinflammatory reaction later in the disease. Several mechanisms have been suggested that might be pivotal for the development of Lyme arthritis and will be highlighted in this review, from molecular mimicry of matrix metallopeptidases and glycosaminoglycans, to autoimmune responses to live bacteria, or remnants of Borrelia spirochetes in joints. Murine studies have suggested that the inflammatory responses are initiated by innate immune cells, but this does not exclude the involvement of the adaptive immune system in this dysregulated immune profile. Genetic predisposition, via human leukocyte antigen-DR isotype and microRNA expression, has been associated with the development of antibiotic-refractory Lyme arthritis. Yet the ultimate cause for (antibiotic-refractory) Lyme arthritis remains unknown. Complex processes of different immune cells and signaling cascades are involved in the development of Lyme arthritis. When these various mechanisms are fully been unraveled, new treatment strategies can be developed to target (antibiotic-refractory) Lyme arthritis more effectively.

Microbiota-mediated mucosal inflammation in arthritis

Mucosal surfaces are a unique symbiotic environment between a host and a vast and diverse ecology of microbes. These microbes have great immunomodulatory potential with respect to the host organism. Indeed, the mucosal immune system strikes a delicate balance between tolerance of commensal organisms and overt inflammation to ward off pathogens. Disruptions of the microbial ecology at mucosal surfaces has been described in a vast number of different human disease processes including many forms of arthritis, and the resulting implications are still being understood to their fullest. Herein, we review the current state of knowledge in microbe-host interactions as it relates to the development of arthritis through bacterial translocation, bacterial metabolite production, education of the immune response, and molecular mimicry.

Differences in clinicopathologic variables between Borrelia C6 antigen seroreactive and Borrelia C6 seronegative glomerulopathy in dogs

Background

Rapidly progressive glomerulonephritis has been described in dogs that seroreact to Borrelia burgdorferi, but no studies have compared clinicopathologic differences in Lyme‐seroreactive dogs with protein‐losing nephropathy (PLN) versus dogs with Borrelia‐seronegative PLN.

Hypothesis/Objectives

Dogs with Borrelia C6 antigen‐seroreactive PLN have distinct clinicopathologic findings when compared to dogs with Borrelia seronegative PLN.

Animals

Forty dogs with PLN and Borrelia C6 antigen seroreactivity and 78 C6‐seronegative temporally matched dogs with PLN.

Methods

Retrospective prevalence case‐control study. Clinical information was retrieved from records of dogs examined at the University of California, Davis, Veterinary Medical Teaching Hospital. Histopathologic findings in renal tissue procured by biopsy or necropsy of dogs with PLN were reviewed.

Results

Retrievers and retriever mixes were overrepresented in seroreactive dogs (P < .001). Seroreactive dogs were more likely to have thrombocytopenia (P < .001), azotemia (P = .002), hyperphosphatemia (P < .001), anemia (P < .001), and neutrophilia (P = .003). Hematuria, glucosuria, and pyuria despite negative urine culture were more likely in seroreactive dogs (all P ≤ .002). Histopathologic findings were consistent with immune‐complex glomerulonephritis in 16 of 16 case dogs and 7 of 23 control dogs (P = 006). Prevalence of polyarthritis was not different between groups (P = .17).

Conclusions and Clinical Importance

C6 seroreactivity in dogs with PLN is associated with a clinicopathologically distinct syndrome when compared with other types of PLN. Early recognition of this syndrome has the potential to improve outcomes through specific aggressive and early treatment.

Borrelia burgdorferi peptidoglycan is a persistent antigen in patients with Lyme arthritis

Lyme disease, caused by the spirochete Borrelia burgdorferi, is the most common vector-borne disease in North America. If early infection is untreated, it can result in late-stage manifestations, including arthritis. Although antibiotics are generally effective at all stages of the disease, arthritis may persist in some patients for months to several years despite oral and intravenous antibiotic treatment. Excessive, dysregulated host immune responses are thought to play an important role in this outcome, but the underlying mechanisms are not completely understood. This study identifies the B. burgdorferi peptidoglycan, a major component of the cell wall, as an immunogen likely to contribute to inflammation during infection and in cases of postinfectious Lyme arthritis.

Lyme disease is a multisystem disorder caused by the spirochete Borrelia burgdorferi. A common late-stage complication of this disease is oligoarticular arthritis, often involving the knee. In ∼10% of cases, arthritis persists after appropriate antibiotic treatment, leading to a proliferative synovitis typical of chronic inflammatory arthritides. Here, we provide evidence that peptidoglycan (PG), a major component of the B. burgdorferi cell envelope, may contribute to the development and persistence of Lyme arthritis (LA). We show that B. burgdorferi has a chemically atypical PG (PG^Bb) that is not recycled during cell-wall turnover. Instead, this pathogen sheds PG^Bb fragments into its environment during growth. Patients with LA mount a specific immunoglobulin G response against PG^Bb, which is significantly higher in the synovial fluid than in the serum of the same patient. We also detect PG^Bb in 94% of synovial fluid samples (32 of 34) from patients with LA, many of whom had undergone oral and intravenous antibiotic treatment. These same synovial fluid samples contain proinflammatory cytokines, similar to those produced by human peripheral blood mononuclear cells stimulated with PG^Bb. In addition, systemic administration of PG^Bb in BALB/c mice elicits acute arthritis. Altogether, our study identifies PG^Bb as a likely contributor to inflammatory responses in LA. Persistence of this antigen in the joint may contribute to synovitis after antibiotics eradicate the pathogen. Furthermore, our finding that B. burgdorferi sheds immunogenic PG^Bb fragments during growth suggests a potential role for PG^Bb in the immunopathogenesis of other Lyme disease manifestations.

Contribution of LTi and TH17 cells to B cell aggregate formation in the central nervous system in a mouse model of multiple sclerosis

Background

In a subgroup of patients suffering from progressive multiple sclerosis (MS), which is an inflammation-mediated neurodegenerative disease of the central nervous system (CNS), B cell aggregates were discovered within the meninges. Occurrence of these structures was associated with a more severe disease course and cortical histopathology. We have developed the B cell-dependent MP4-induced experimental autoimmune encephalomyelitis (EAE) as a mouse model to mimic this trait of the human disease. The aim of this study was to determine a potential role of lymphoid tissue inducer (LTi) and T_H17 cells in the process of B cell aggregate formation in the MP4 model.

Methods

We performed flow cytometry of cerebellar and splenic tissue of MP4-immunized mice in the acute and chronic stage of the disease to analyze the presence of CD3⁻CD5⁻CD4⁺RORγt⁺ LTi and CD3⁺CD5⁺CD4⁺RORγt⁺ T_H17 cells. Myelin oligodendrocyte glycoprotein (MOG):35–55-induced EAE was used as B cell-independent control model. We further determined the gene expression profile of B cell aggregates using laser capture microdissection, followed by RNA sequencing.

Results

While we were able to detect LTi cells in the embryonic spleen and adult intestine, which served as positive controls, there was no evidence for the existence of such a population in acute or chronic EAE in neither of the two models. Yet, we detected CD3⁻CD5⁻CD4⁻RORγt⁺ innate lymphoid cells (ILCs) and T_H17 cells in the CNS, the latter especially in the chronic stage of MP4-induced EAE. Moreover, we observed a unique gene signature in CNS B cell aggregates compared to draining lymph nodes of MP4-immunized mice and to cerebellum as well as draining lymph nodes of mice with MOG:35–55-induced EAE.

Conclusion

The absence of LTi cells in the cerebellum suggests that other cells might take over the function as an initiator of lymphoid tissue formation in the CNS. Overall, the development of ectopic lymphoid organs is a complex process based on an interplay between several molecules and signals. Here, we propose some potential candidates, which might be involved in the formation of B cell aggregates in the CNS of MP4-immunized mice.

Collagenolytic Enzymes and their Applications in Biomedicine

Nowadays, enzymatic therapy is a very promising line of treatment for many different diseases. There is a group of disorders and conditions, caused by fibrotic and scar processes and associated with the excessive accumulation of collagen that needs to be catabolized to normalize the connective tissue content. The human body normally synthesizes special extracellular enzymes, matrix metalloproteases (MMPs) by itself. These enzymes can cleave components of extracellular matrix (ECM) and different types of collagen and thus maintain the balance of the connective tissue components. MMPs are multifunctional enzymes and are involved in a variety of organism processes. However, under pathological conditions, the function of MMPs is not sufficient, and these enzymes fail to deal with disease. Thus, medical intervention is required. Enzymatic therapy is a very effective way of treating such collagen-associated conditions. It involves the application of exogenous collagenolytic enzymes that catabolize excessive collagen at the affected site and lead to the successful elimination of disease. Such collagenolytic enzymes are synthesized by many organisms: bacteria, animals (especially marine organisms), plants and fungi. The most studied and commercially available are collagenases from Clostridium histolyticum and from the pancreas of the crab Paralithodes camtschatica, due to their ability to effectively hydrolyse human collagen without affecting other tissues, and their wide pH ranges of collagenolytic activity. In the present review, we summarize not only the data concerning existing collagenase-based medications and their applications in different collagen-related diseases and conditions, but we also propose collagenases from different sources for their potential application in enzymatic therapy.

CD1b presents self and Borrelia burgdorferi diacylglycerols to human T cells

Lyme disease is a common multisystem disease caused by infection with a tick‐transmitted spirochete, Borrelia burgdorferi and related Borrelia species. The monoglycosylated diacylglycerol known as B. burgdorferi glycolipid II (BbGL‐II) is a major target of antibodies in sera from infected individuals. Here, we show that CD1b presents BbGL‐II to human T cells and that the TCR mediates the recognition. However, we did not detect increased frequency of CD1b‐BbGL‐II binding T cells in the peripheral blood of Lyme disease patients compared to controls. Unexpectedly, mapping the T cell specificity for BbGL‐II‐like molecules using tetramers and activation assays revealed a concomitant response to CD1b‐expressing APCs in absence of BbGL‐II. Further, among all major classes of self‐lipid tested, BbGL‐II responsive TCRs show strong cross‐reactivity to diacylglycerol, a self‐lipid antigen with structural similarities to BbGL‐II. Extending prior work on MHC and CD1b, CD1c, and CD1d proteins, this study provides evidence for cross‐reactive CD1b‐restricted T cell responses to bacterial and self‐antigens, and identifies chemically defined targets for future discovery of self and foreign antigen cross‐reactive T cells.

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.

Lyme borreliosis-from tick bite to diagnosis and treatment

Lyme borreliosis is caused by certain genospecies of the Borrelia burgdorferi sensu lato complex, which are transmitted by hard ticks of the genus Ixodes. The most common clinical manifestation is erythema migrans, an expanding skin redness that usually develops at the site of a tick bite and eventually resolves even without antibiotic treatment. The infecting pathogens can spread to other tissues and organs, resulting in manifestations that can involve the nervous system, joints, heart and skin. Fatal outcome is extremely rare and is due to severe heart involvement; fetal involvement is not reliably ascertained. Laboratory support-mainly by serology-is essential for diagnosis, except in the case of typical erythema migrans. Treatment is usually with antibiotics for 2 to 4 weeks; most patients recover uneventfully. There is no convincing evidence for antibiotic treatment longer than 4 weeks and there is no reliable evidence for survival of borreliae in adequately treated patients. European Lyme borreliosis is a frequent disease with increasing incidence. However, numerous scientifically questionable ideas on its clinical presentation, diagnosis and treatment may confuse physicians and lay people. Since diagnosis of Lyme borreliosis should be based on appropriate clinical signs, solid knowledge of clinical manifestations is essential.

Biologic Markers of Antibiotic-Refractory Lyme Arthritis in Human: A Systematic Review

INTRODUCTION

Lyme disease-also known as Lyme borreliosis (LB)-is the most common vector-borne disease in North America and Europe. It may result in substantial morbidity, primarily from persistent Lyme arthritis (LA) that-although treatable-can develop into antibiotic-refractory LA (A-RLA). The aim of this study is to systematically review and evaluate a range of biomarkers for their potential predictive value in the development of A-RLA.

METHODS

We conducted a systematic review of studies examining biomarkers among patients with A-RLA from MEDLINE via OVID, EMBASE and Web of Science databases and identified a total of 26 studies for qualitative analysis.

RESULTS

All studies were of patient populations from the USA, with the exception of one from Europe. We identified an array of biomarkers that are commonly modulated in the A-RLA compared with subjects with antibiotic-responsive LA. These included a range of inflammatory markers (IL-6, IL-8, IL-10, IL-1β, IL-23, IL-17F, TNFα, IFNγ, CXCL9, CXCL10, CCL2, CCL3 and CCL4, CRP), factors along the innate and adaptive immune response pathways (e.g., CD4⁺ T cells, GITR receptors, OX40 receptors, IL-4⁺CD4⁺Th2 cells, IL-17⁺CD4⁺ T cells) and an array of miRNA species (e.g., miR-142, miR-17, miR-20a, let-7c and miR-30fam).

CONCLUSION

The evidence base of biologic markers for A-RLA is limited. However, a range of promising biomarkers have been identified. Cytokines and chemokines related to Th17 pathway together with a number of miRNAs species (miR-146a, miR-155 and let-7a) may be promising candidates in the prediction of A-RLA. A panel of multiple biomarkers may yield clinically relevant prediction of the possible resistance at the time of LA first diagnosis.

FUNDING

Public Health Agency of Canada.

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.

Characteristics and clinical outcomes after treatment of a national cohort of PCR-positive Lyme arthritis

OBJECTIVES

To describe the clinical and microbiological characteristics and outcomes after antibiotic treatment of a national cohort of patients with Lyme arthritis confirmed by PCR testing on synovial fluid and by serology, when available.

METHODS

Using the French National Reference Center for Borrelia database, patients with a positive PCR on synovial fluid for Borrelia were identified. Patient clinical and biological characteristics were reviewed from patient records. Long-term outcomes after treatment were studied through a questionnaire and with follow-up data.

RESULTS

Among 357 synovial fluid testing by PCR between 2010 and 2016, 37 (10.4%) were positive for Borrelia. Patients' median age was 36 years (range 6-78) with 61% of men and 28% patients under 18. The presentation was monoarticular in 92% and the knee was involved in 97%. Contrary to the Borrelia species repartition in European ticks, B. burgdorferi sensu stricto was the most prevalent species found in synovial fluid (54%) followed by B. azfelii (29%) and B. garinii (17%). Antibiotic treatments were mainly composed of doxycycline (n = 24), ceftriaxone (n = 10) and amoxicillin (n = 6), for a median duration of 4 weeks (range 3-12). Despite a properly conducted treatment, 34% of patients (n = 12) developed persistent synovitis for at least 2 months (median duration 3 months, range 2-16). Among those, 3 developed systemic inflammatory oligo- or polyarthritis in previously unaffected joints with no signs of persistent infection (repeated PCR testing negative), which mandated Disease-Modifying Antirheumatic Drugs (DMARD) introduction, leading to remission.

CONCLUSION

In France and contrary to ticks ecology, Lyme arthritis is mainly caused by B. burgdorferi sensu stricto. Despite proper antibiotic therapy, roughly one third of patients may present persistent inflammatory synovitis and a small proportion may develop systemic arthritis. In such cases, complete remission can be reached using DMARD.

Correlation of Lyme Disease-Associated IgG4 Autoantibodies With Synovial Pathology in Antibiotic-Refractory Lyme Arthritis

OBJECTIVE

To determine whether IgG subclasses of Borrelia burgdorferi antibodies differ from those of 3 Lyme disease (LD)-associated autoantibodies.

METHODS

IgG antibody subclasses were determined by enzyme-linked immunosorbent assay in serum samples from 215 patients with features representative of each of the 3 stages of LD. Antibody and cytokine profiles were measured in matched serum and synovial fluid (SF) samples from patients with Lyme arthritis. Synovial tissue from patients with antibiotic-refractory arthritis was examined for histologic features, IgG subclasses of plasma cells, and messenger RNA (mRNA) subclass expression.

RESULTS

B burgdorferi antibodies were primarily of the IgG1 and IgG3 subclasses, and the levels increased as the infection progressed. In contrast, LD-associated autoantibodies were mainly of the IgG2 and IgG4 subclasses, and these responses were found primarily in patients with either antibiotic-refractory or antibiotic-responsive arthritis, particularly in SF. However, compared with the responsive group, the inflammatory milieu in SF in the refractory group was enriched for cytokines representative of innate, Th1, Th2, and Th17 responses. Synovial tissue in a subgroup of patients with refractory arthritis showed marked expression of mRNA for IgG4 antibodies and large numbers of IgG4-staining plasma cells. IgG4 autoantibodies in SF to each of the 3 LD-associated autoantigens correlated with the magnitude of obliterative microvascular lesions and fibrosis in the tissue.

CONCLUSION

Our findings indicate that the subclasses of IgG antibodies to B burgdorferi differ from those of LD-associated autoantibodies. Furthermore, the correlation of IgG4 autoantibodies with specific synovial pathology in the refractory group suggests a role for these autoantibodies, either protective or pathologic, in antibiotic-refractory Lyme arthritis.

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.

[Cutaneous manifestations of Lyme disease : Pitfalls in the serological diagnostic workup]

Serology, the detection of B. burgdorferi-specific IgM and IgG serum antibodies, is the most common laboratory test to diagnose cutaneous manifestations of Lyme disease. In a two-tiered approach, an ELISA is used as a screening test. A positive or equivocal ELISA result needs confirmation by a specific immunoblot. The sensitivity of this approach reaches 80-95%. The diagnosis of erythema migrans is based on its typical clinical appearance. Serology is only indicated in atypical cases. In contrast, serology is mandatory in the diagnostic workup of borrelial lymphocytoma and acrodermatitis chronica atrophicans. A positive serology can persist for many years, even after adequate antibiotic treatment. A positive serology is no indication for antibiotic treatment if typical symptoms of Lyme disease are absent.

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.

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.

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.

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.

Lyme borreliosis

Lyme borreliosis is a tick-borne disease that predominantly occurs in temperate regions of the northern hemisphere and is primarily caused by the bacterium Borrelia burgdorferi in North America and Borrelia afzelii or Borrelia garinii in Europe and Asia. Infection usually begins with an expanding skin lesion, known as erythema migrans (referred to as stage 1), which, if untreated, can be followed by early disseminated infection, particularly neurological abnormalities (stage 2), and by late infection, especially arthritis in North America or acrodermatitis chronica atrophicans in Europe (stage 3). However, the disease can present with any of these manifestations. During infection, the bacteria migrate through the host tissues, adhere to certain cells and can evade immune clearance. Yet, these organisms are eventually killed by both innate and adaptive immune responses and most inflammatory manifestations of the infection resolve. Except for patients with erythema migrans, Lyme borreliosis is diagnosed based on a characteristic clinical constellation of signs and symptoms with serological confirmation of infection. All manifestations of the infection can usually be treated with appropriate antibiotic regimens, but the disease can be followed by post-infectious sequelae in some patients. Prevention of Lyme borreliosis primarily involves the avoidance of tick bites by personal protective measures.

Immunogenic HLA-DR-Presented Self-Peptides Identified Directly from Clinical Samples of Synovial Tissue, Synovial Fluid, or Peripheral Blood in Patients with Rheumatoid Arthritis or Lyme Arthritis

Human leukocyte antigen-antigen D related (HLA-DR) molecules are highly expressed in synovial tissue (ST), the target of the immune response in chronic inflammatory forms of arthritis. Here, we used LC-MS/MS to identify HLA-DR-presented self-peptides in cells taken directly from clinical samples: ST, synovial fluid mononuclear cells (SFMC), or peripheral blood mononuclear cells (PBMC) from five patients with rheumatoid arthritis (RA) and eight with Lyme arthritis (LA). We identified 1593 non-redundant HLA-DR-presented peptides, derived from 870 source proteins. A total of 67% of the peptides identified in SFMC and 55% of those found in PBMC were found in ST, but analysis of SFMC/PBMC also revealed new antigen-presented peptides. Peptides were synthesized and examined for reactivity with the patients' PBMC. To date, three autoantigens in RA and four novel autoantigens in LA, presented in ST and/or PBMC, were shown to be targets of T- and B-cell responses in these diseases; ongoing analyses may add to this list. Thus, immunoprecipitation and LC-MS/MS can now identify hundreds of HLA-DR-presented self-peptides from individual patients' tissues or fluids with mixed cell populations. Importantly, identification of HLA-DR-presented peptides from SFMC or PBMC allows testing of more patients, including those early in the disease. Direct analysis of clinical samples facilitates identification of novel immunogenic T-cell epitopes.