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.

No abstract

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 (PGBb) that is not recycled during cell-wall turnover. Instead, this pathogen sheds PGBb fragments into its environment during growth. Patients with LA mount a specific immunoglobulin G response against PGBb, which is significantly higher in the synovial fluid than in the serum of the same patient. We also detect PGBb 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 PGBb. In addition, systemic administration of PGBb in BALB/c mice elicits acute arthritis. Altogether, our study identifies PGBb 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 PGBb fragments during growth suggests a potential role for PGBb in the immunopathogenesis of other Lyme disease manifestations.

During the past decade, the immune and endocrine systems have been discovered to interact in controlling physiologic processes as diverse as cell growth and differentiation, metabolism, and even human and animal behavior. The interaction between these two major physiological systems is a bi-directional process. While it has been well documented that hormones, including prolactin (PRL), growth hormone (GH), insulin-like growth factor-I (IGF-I), and thyroid-stimulating hormone (TSH), regulate a variety of immune events, a great deal of data have accumulated supporting the notion that cytokines from the innate immune system also affect the neuroendocrine system. Communication between these two systems coordinates processes that are necessary to maintain homeostasis. Proinflammatory cytokines often act as negative regulatory signals that temper the action of hormones and growth factors. This system of 'checks and balances' is an active, ongoing process, even in healthy individuals. Dysregulation of this process has been implicated as a potential pathogenic factor in the development of co-morbid conditions associated with several chronic inflammatory diseases, including type 2 diabetes, cardiovascular disease, cerebrovascular disease, inflammatory bowel disease, rheumatoid arthritis, major depression, and even normal aging. Over the past decade, research in our laboratory has focused on the ability of the major proinflammatory cytokines, tumor necrosis factor (TNF)alpha and interleukin (IL)-1beta, to induce a state of IGF resistance. This review will highlight these and other new findings by explaining how proinflammatory cytokines induce resistance to the major growth factor, insulin-like growth factor-I (IGF-I). We also highlight that IGF-I can induce resistance or reduce sensitivity to brain TNFalpha and discuss how TNFalpha, IL-1beta, and IGF-I interact to regulate several aspects of behavior and cognition.

Objective Single-nucleotide polymorphisms (SNPs) have been identified in several genes encoding Toll-like receptors (TLRs) that alter immune function, inflammatory responses and disease susceptibility. The SNPs with best evidence for affecting immune function are TLR1 (1805GG), TLR2 (2258GA) and TLR5 (1174CT). Methods We studied the frequency and functional outcome of these polymorphisms in 248 patients with Lyme disease. Cytokine and chemokine levels were determined in serum of patients with erythema migrans (EM), joint fluid of patients with Lyme arthritis, and supernatants of B. burgdorferi-stimulated PBMC from Lyme arthritis patients, using multiplex assays. Results The frequency of TLR1-1805GG polymorphism was greater in patients with antibiotic-refractory arthritis compared with patients with EM or antibiotic-responsive arthritis. Early in the illness, EM patients with 1805GG, primarily those infected with B. burgdorferi RST1 strains, had higher serum levels of IFNγ, CXCL9 and CXCL10, and more severe infection than patients with 1805TG/TT. These inflammatory responses were amplified in patients with Lyme arthritis, and the highest responses were observed in antibiotic-refractory arthritis patients with 1805GG who had been infected with RST1 strains. When PBMC from Lyme arthritis patients were stimulated with a B. burgdorferi RST1 strain, the 1805GG group had significantly larger fold-increase in the levels of IFNγ, CCL2, CXCL9 and CXCL10, than the 1805TG/TT group. In contrast, the TLR2 and TLR5 polymorphisms did not vary among groups in frequency or function. Conclusion The TLR1-1805GG polymorphism in B. burgdorferi RST1-infected patients was associated with stronger TH1-like inflammatory responses, which may set the stage for antibiotic-refractory arthritis.

No abstract

Objective Autoantigen presentation by HLA-DR molecules is thought to be a central component of many autoimmune diseases, but uncovering disease-relevant autoantigens has been a difficult challenge. Our goal was to identify autoantigens in patients with antibiotic-refractory Lyme arthritis, which is thought to result from infection-induced autoimmunity. Methods Using tandem mass spectrometry, naturally presented HLA-DR self-peptides from a patient’s synovium were identified, synthesized and reacted with his peripheral blood mononuclear cells (PBMC). Immunoreactive peptides and their source proteins were then tested for T and B cell responses using large numbers of patients’ cells or sera. Results Of 120 HLA-DR-presented self-peptides identified from one patient, one peptide derived from endothelial cell growth factor (ECGF) caused his PBMC to proliferate. We then found that T and B cell responses to ECGF occurred systemically in about 10–30% of patients with early or late manifestations of Lyme disease, primarily in those with refractory arthritis-associated HLA-DR alleles, such as DRB1*0101 and 0401. Compared with patients with antibiotic-responsive arthritis, those with antibiotic-refractory arthritis had significantly higher concentrations of ECGF in synovial fluid (P<0.0001) and more often had ECGF antibody reactivity. In non-antibiotic-treated historic patients who developed arthritis, 26% had ECGF reactivity, which often developed before the onset of arthritis and was associated with significantly longer courses of arthritis. Conclusion T and B cell responses to ECGF occur in a subset of patients with Lyme disease, particularly in those with antibiotic-refractory arthritis, providing the first direct evidence for autoimmune T and B cell responses in this illness.

Evidence is emerging for differential pathogenicity among Borrelia burgdorferi genotypes in the United States. By using two linked genotyping systems, ribosomal RNA intergenic spacer type (RST) and outer surface protein C (OspC), we studied the inflammatory potential of B. burgdorferi genotypes in cells and patients with erythema migrans or Lyme arthritis. When macrophages were stimulated with 10 isolates of each RST1, RST2, or RST3 strain, RST1 (OspC type A)-stimulated cells expressed significantly higher levels of IL-6, IL-8, chemokine ligand (CCL) 3, CCL4, tumor necrosis factor, and IL-1β, factors associated with innate immune responses. In peripheral blood mononuclear cells, RST1 strains again stimulated significantly higher levels of these mediators. Moreover, compared with RST2, RST1 isolates induced significantly more interferon (IFN)-α, IFN-γ, and CXCL10, which are needed for adaptive immune responses; however, OspC type I (RST3) approached RST1 (OspC type A) in stimulating these adaptive immune mediators. Similarly, serum samples from patients with erythema migrans who were infected with the RST1 genotype had significantly higher levels of almost all of these mediators, including exceptionally high levels of IFN-γ-inducible chemokines, CCL2, CXCL9, and CXCL10; and this pronounced inflammatory response was associated with more symptomatic infection. Differences among genotypes were not as great in patients with Lyme arthritis, but those infected with RST1 strains more often had antibiotic-refractory arthritis. Thus, the B. burgdorferi RST1 (OspC type A) genotype, followed by the RST3 (OspC type I) genotype, causes greater inflammation and more severe disease, establishing a link between spirochetal virulence and host inflammation.