Objective Prevotella copri, an intestinal microbe, may over-expand in stool samples of patients with new-onset rheumatoid arthritis (NORA), 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 from patients' synovial tissue or peripheral blood mononuclear cells (PBMC) using tandem mass spectrometry, followed by testing the antigenicity of peptides or their source proteins using samples from RA patients or comparison groups. T cell reactivity was determined by ELISpot assays; antibody responses were measured by ELISA, and cytokine/chemokine determinations were made by Luminex. 16S rDNA of P. copri was sought in serum and synovial fluid samples using nested PCR. Results In PBMC, we identified an HLA-DR-presented peptide from a 27-kD protein of P. copri (Pc-p27), which stimulated Th1 responses in 42% of NORA patients. In both NORA and chronic RA patients, one subgroup had IgA antibody responses to Pc-p27 or the whole organism, which correlated with Th17 cytokine responses and frequent anti-citrullinated protein antibodies (ACPA). 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 ACPA. 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.

Poxviruses encode proteins that suppress host immune responses, including secreted decoy receptors for pro-inflammatory cytokines such as interleukin-1 (IL-1) and the vaccinia virus proteins A46R and A52R that inhibit intracellular signaling by members of the IL-1 receptor (IL-1R) and Toll-like receptor (TLR) family. In vivo, the TLRs mediate the innate immune response by serving as pathogen recognition receptors, whose oligomerized intracellular Toll/IL-1 receptor (TIR) domains can initiate innate immune signaling. A family of TIR domaincontaining adapter molecules transduces signals from engaged receptors that ultimately activate NF-B and/or interferon regulatory factor 3 (IRF3) to induce proinflammatory cytokines. Data base searches detected a significant similarity between the N1L protein of vaccinia virus and A52R, a poxvirus inhibitor of TIR signaling. Compared with other poxvirus virulence factors, the poxvirus N1L protein strongly affects virulence in vivo; however, the precise target of N1L was previously unknown. Here we show that N1L suppresses NF-B activation following engagement of Toll/IL-1 receptors, tumor necrosis factor receptors, and lymphotoxin receptors. N1L inhibited receptor-, adapter-, TRAF-, and IKK-␣ and IKK-␤-dependent signaling to NF-B. N1L associated with several components of the multisubunit I-B kinase complex, most strongly associating with the kinase, TANK-binding kinase 1 (TBK1). Together these findings are consistent with the hypothesis that N1L disrupts signaling to NF-B by Toll/IL-1Rs and TNF superfamily receptors by targeting the IKK complex for inhibition. Furthermore, N1L inhibited IRF3 signaling, which is also regulated by TBK1. These studies define a role for N1L as an immunomodulator of innate immunity by targeting components of NF-B and IRF3 signaling pathways.

SYNOPSIS In the United States, Lyme arthritis is the most common feature of late stage infection with the tick-borne spirochete, Borrelia burgdorferi, usually beginning months after the initial tick bite. However, in some patients, including most of those seen today, the earlier phases of the infection are asymptomatic and arthritis is the presenting manifestation of the disease. Patients with Lyme arthritis have intermittent or persistent attacks of joint swelling and pain in one or a few large joints, especially the knee, usually over a period of several years, without prominent systemic manifestations. Serologic testing is the mainstay of diagnosis. Synovial fluid PCR testing for B. burgdorferi DNA is often positive prior to treatment, but it is not a reliable marker of spirochetal eradication after antibiotic therapy. Responses to oral or intravenous antibiotic treatment are generally excellent, although a small percentage of patients have persistent synovitis after 2-3 months of oral and IV antibiotics, which usually then responds to anti-inflammatory therapies, disease modifying anti-rheumatic drugs (DMARDs), or synovectomy. This chapter reviews the clinical manifestations, diagnosis, and management of Lyme arthritis.

Objective. The interleukin-6 pathway is up-regulated in giant cell arteritis (GCA), Takayasu arteritis (TA), and polymyalgia rheumatica (PMR). We retrospectively assessed the outcomes of 10 patients with relapsing/refractory GCA, TA, or PMR treated with tocilizumab (TCZ). Methods. Patients with GCA (n ‫؍‬ 7), TA (n ‫؍‬ 2), and PMR (n ‫؍‬ 1) received TCZ. Seven subjects had failed at least 1 second-line agent. The outcomes evaluated were symptoms of disease activity, inflammatory markers, ability to taper glucocorticoids, and cross-sectional imaging when indicated clinically. Results. The mean followup time of this cohort since diagnosis was 27 months (range 16 -60 months). The patients were treated with TCZ for a mean period of 7.8 months (range 4 -12 months). Before TCZ therapy, the patients experienced an average of 2.4 flares/year. All patients entered and maintained clinical remission during TCZ therapy. The mean daily prednisone dosages before and after TCZ initiation were 20.8 mg/day (range 7-34.3 mg/day) and 4.1 mg/day (range 0 -10.7 mg/day), respectively (P ‫؍‬ 0.0001). The mean erythrocyte sedimentation rate declined from 41.5 mm/hour (range 11-68 mm/hour) to 7 mm/hour (range 2.2-11.3 mm/hour; P ‫؍‬ 0.0001). The adverse effects of TCZ included mild neutropenia (n ‫؍‬ 4) and transaminitis (n ‫؍‬ 4). One patient flared 2 months after TCZ discontinuation. An autopsy on 1 patient who died from a postoperative myocardial infarction following elective surgery revealed persistent vasculitis of large and mediumsized arteries. Conclusion. TCZ therapy led to clinical and serologic improvement in patients with refractory/relapsing GCA, TA, or PMR. The demonstration of persistent large-vessel vasculitis at autopsy of 1 patient who had shown a substantial response requires close scrutiny in larger studies.