Collagen epitope expression on B cells is sufficient to confer tolerance to collagen-induced arthritis.

BACKGROUND: The mechanisms underlying tolerance induction and maintenance in autoimmune arthritis remain elusive. In a mouse model of rheumatoid arthritis, collagen type II (CII)-induced arthritis, we explore the contribution of B cells to antigen-specific tolerance. METHODS: To generate expression of the CII-peptide specifically on B-cell major histocompatibility complex type II, lentiviral-based gene therapy including a B-cell-specific Igk promoter was used. RESULTS: Presentation of the CII-peptide on B cells significantly reduced the frequency and severity of arthritis as well as the serum levels of CII -specific IgG antibodies. Further, both frequency and suppressive function of regulatory T cells were increased in tolerized mice. Adoptive transfer of regulatory T cells from tolerized mice to naïve mice ameliorated the development of CII-induced arthritis. CONCLUSION: Our data suggest that endogenous presentation of the CII-peptide on B cells is one of the key contributors to arthritis tolerance induction and maintenance.

Gene Therapy Induces Antigen-Specific Tolerance in Experimental Collagen-Induced Arthritis.

Here, we investigate induction of immunological tolerance by lentiviral based gene therapy in a mouse model of rheumatoid arthritis, collagen II-induced arthritis (CIA). Targeting the expression of the collagen type II (CII) to antigen presenting cells (APCs) induced antigen-specific tolerance, where only 5% of the mice developed arthritis as compared with 95% of the control mice. In the CII-tolerized mice, the proportion of Tregs as well as mRNA expression of SOCS1 (suppressors of cytokine signaling 1) increased at day 3 after CII immunization. Transfer of B cells or non-B cell APC, as well as T cells, from tolerized to naïve mice all mediated a certain degree of tolerance. Thus, sustainable tolerance is established very early during the course of arthritis and is mediated by both B and non-B cells as APCs. This novel approach for inducing tolerance to disease specific antigens can be used for studying tolerance mechanisms, not only in CIA but also in other autoimmune diseases.

Antigen-specific gene therapy after immunisation reduces the severity of collagen-induced arthritis.

Reestablishment of tolerance induction in rheumatoid arthritis (RA) would be an optimal treatment with few, if any, side effects. However, to develop such a treatment further insights in the immunological mechanisms governing tolerance are needed. We have developed a model of antigen-specific tolerance in collagen type II (CII) induced arthritis (CIA) using lentivirus-based gene therapy. The immunodominant epitope of CII was inserted into a lentivirus vector to achieve expression on the MHC class II molecule and the lentiviral particles were subsequently intravenously injected at different time points during CIA. Injection of lentiviral particles in early phases of CIA, that is, at day 7 or day 26 after CII immunisation, partially prevented development of arthritis, decreased the serum levels of CII-specific IgG antibodies, and enhanced the suppressive function of CII-specific T regulatory cells. When lentiviral particles were injected during manifest arthritis, that is, at day 31 after CII immunisation, the severity of arthritis progression was ameliorated, the levels of CII-specific IgG antibodies decreased and the proportion of T regulatory cells increased. Thus, antigen-specific gene therapy is effective when administered throughout the inflammatory course of arthritis and offers a good model for investigation of the basic mechanisms during tolerance in CIA.

Negative feedback on IL-23 exerted by IL-17A during pulmonary inflammation.

It is now established that IL-17 has a broad pro-inflammatory potential in mammalian host defense, in inflammatory disease and in autoimmunity, whereas little is known about its anti-inflammatory potential and inhibitory feedback mechanisms. Here, we examined whether IL-17A can inhibit the extracellular release of IL-23 protein, the upstream regulator of IL-17A producing lymphocyte subsets, that is released from macrophages during pulmonary inflammation. We characterized the effect of IL-17A on IL-23 release in several models of pulmonary inflammation, evaluated the presence of IL-17 receptor A (RA) and C (RC) on human alveolar macrophages and assessed the role of the Rho family GTPase Rac1 as a mediator of the effect of IL-17A on the release of IL-23 protein. In a model of sepsis-induced pneumonia, intravenous exposure to Staphylococcus aureus caused higher IL-23 protein concentrations in cell-free bronchoalveolar lavage (BAL) samples from IL-17A knockout (KO) mice, compared with wild type (WT) control mice. In a model of Gram-negative airway infection, pre-treatment with a neutralizing anti-IL-17A Ab and subsequent intranasal (i.n.) exposure to LPS caused higher IL-23 and IL-17A protein concentrations in BAL samples compared with mice exposed to LPS, but pre-treated with an isotype control Ab. Moreover, i.n. exposure with IL-17A protein per se decreased IL- 23 protein concentrations in BAL samples. We detected IL-17RA and IL-17RC on human alveolar macrophages, and found that in vitro stimulation of these cells with IL-17A protein, after exposure to LPS, decreased IL-23 protein in conditioned medium, but not IL-23 p19 or p40 mRNA. This study indicates that IL-17A can partially inhibit the release of IL-23 protein during pulmonary inflammation, presumably by stimulating the here demonstrated receptor units IL-17RA and IL-17RC on alveolar macrophages. Hypothetically, the demonstrated mechanism may serve as negative feedback to protect from excessive IL-17A signaling and to control antibacterial host defense once it is activated.

Disease-dependent local IL-10 production ameliorates collagen induced arthritis in mice.

Rheumatoid arthritis (RA) is a chronic destructive autoimmune disease characterised by periods of flare and remission. Today's treatment is based on continuous immunosuppression irrespective of the patient's inflammatory status. When the disease is in remission the therapy is withdrawn but withdrawal attempts often results in inflammatory flares, and re-start of the therapy is commenced when the inflammation again is prominent which leads both to suffering and increased risk of tissue destruction. An attractive alternative treatment would provide a disease-regulated therapy that offers increased anti-inflammatory effect during flares and is inactive during periods of remission. To explore this concept we expressed the immunoregulatory cytokine interleukin (IL)-10 gene under the control of an inflammation dependent promoter in a mouse model of RA - collagen type II (CII) induced arthritis (CIA). Haematopoetic stem cells (HSCs) were transduced with lentiviral particles encoding the IL-10 gene (LNT-IL-10), or a green fluorescence protein (GFP) as control gene (LNT-GFP), driven by the inflammation-dependent IL-1/IL-6 promoter. Twelve weeks after transplantation of transduced HSCs into DBA/1 mice, CIA was induced. We found that LNT-IL-10 mice developed a reduced severity of arthritis compared to controls. The LNT-IL-10 mice exhibited both increased mRNA expression levels of IL-10 as well as increased amount of IL-10 produced by B cells and non-B APCs locally in the lymph nodes compared to controls. These findings were accompanied by increased mRNA expression of the IL-10 induced suppressor of cytokine signalling 1 (SOCS1) in lymph nodes and a decrease in the serum protein levels of IL-6. We also found a decrease in both frequency and number of B cells and serum levels of anti-CII antibodies. Thus, inflammation-dependent IL-10 therapy suppresses experimental autoimmune arthritis and is a promising candidate in the development of novel treatments for RA.

Interleukin 15 mediates joint destruction in Staphylococcus aureus arthritis.

BACKGROUND: Staphylococcus aureus arthritis causes severe and rapid joint damage despite antibiotics. Thus, there is a need to identify new treatment targets in addition to antibiotics. Lately, interleukin 15 (IL-15) has been implicated both in osteoclastogenesis and in bacterial clearance-2 important issues in S. aureus-induced joint destruction. This has prompted us to investigate the importance of IL-15 in S. aureus-induced arthritis. METHODS: Toxic shock syndrome toxin-1 producing S. aureus was intravenously inoculated in IL-15 knockout and wildtype mice and in wildtype mice treated with anti-IL-15 antibodies (aIL-15ab) or isotype control antibody. RESULTS: Absence of IL-15, either in knockout mice or after treatment with aIL-15ab, significantly reduced weight loss compared with controls during the infection. The severity of synovitis and joint destruction was significantly decreased in IL-15 knockout and aIL-15ab treated mice compared with controls. In IL-15 knockout mice there was a reduced number of osteoclasts in the joints. The host's ability to clear bacteria was not influenced in the IL-15 knockout mice, but significantly increased after treatment with aIL-15ab. CONCLUSIONS: IL-15 is a mediator of joint destruction in S. aureus-induced arthritis and contributes to general morbidity, which makes this cytokine an interesting treatment target in addition to conventional antibiotics.

Interleukin-17A during local and systemic Staphylococcus aureus-induced arthritis in mice.

Staphylococcus aureus is one of the dominant pathogens that induce septic arthritis in immunocompromised hosts, e.g., patients suffering from rheumatoid arthritis treated with immunosuppressive drugs. S. aureus-induced arthritis leads to severe joint destruction and high mortality despite antibiotic treatment. Recently, interleukin-17A (IL-17A) has been discovered to be an important mediator of aseptic arthritis both in mice and humans, but its function in S. aureus-induced arthritis is largely unknown. Here, we investigated the role of IL-17A in host defense against arthritis following systemic and local S. aureus infection in vivo. IL-17A knockout mice and wild-type mice were inoculated systemically (intravenously) or locally (intra-articularly) with S. aureus. During systemic infection, IL-17A knockout mice lost significantly more weight than the wild-type mice did, but no differences were found in the mortality rate. The absence of IL-17A had no impact on clinical arthritis development but led to increased histopathological erosivity late during systemic S. aureus infection. Bacterial clearance in kidneys was increased in IL-17A knockout mice compared to the level in wild-type mice only 1 day after bacterial inoculation. During systemic S. aureus infection, serum IL-17F protein levels and mRNA levels in the lymph nodes were elevated in the IL-17A knockout mice compared to the level in wild-type mice. In contrast to systemic infection, the IL-17A knockout mice had increased synovitis and erosions and locally decreased clearance of bacteria 3 days after local bacterial inoculation. On the basis of these findings, we suggest that IL-17A is more important in local host defense than in systemic host defense against S. aureus-induced arthritis.