IL-23 Dependent and Independent Stages of Experimental Arthritis: No Clinical Effect of Therapeutic IL-23p19 Inhibition in Collagen-induced Arthritis

IL-23p19 deficient mice have revealed a critical role of IL-23 in the development of experimental autoimmune diseases, such as collagen-induced arthritis (CIA). Neutralizing IL-23 after onset of CIA in rats has been shown to reduce paw volume, but the effect on synovial inflammation and the immunological autoimmune response is not clear. In this study, we examined the role of IL-23 at different stages of CIA and during T cell memory mediated flare-up arthritis with focus on changes in B cell activity and Th1/Th17 modulation. Anti-IL-23p19 antibody (anti-IL23p19) treatment, starting 15 days after the type II collagen (CII)-immunization but before clinical signs of disease onset, significantly suppressed the severity of CIA. This was accompanied with significantly lower CII-specific IgG1 levels and lower IgG2a levels in the anti-IL-23p19 treated mice compared to the control group. Importantly, neutralizing IL-23 after the first signs of CIA did not ameliorate the disease. This was in contrast to arthritic mice that underwent an arthritis flare-up since a significantly lower disease score was observed in the IL-23p19 treated mice compared to the control group, accompanied by lower synovial IL-17A and IL-22 expression in the knee joints of these mice. These data show IL-23-dependent and IL-23-independent stages during autoimmune CIA. Furthermore, the memory T cell mediated flare-up arthritis is IL-23-mediated. These data suggest that specific neutralization of IL-23p19 after onset of autoimmune arthritis may not be beneficial as a therapeutic therapy for patients with rheumatoid arthritis (RA). However, T cell mediated arthritis relapses in patients with RA might be controlled by anti-IL-23p19 treatment

Interleukin-33 Contributes Toward Loss of Tolerance by Promoting B-Cell-Activating Factor of the Tumor-Necrosis-Factor Family (BAFF)-Dependent Autoantibody Production

Breaking tolerance is a key event leading to autoimmunity, but the exact mechanisms responsible for this remain uncertain. Here we show that the alarmin IL-33 is able to drive the generation of autoantibodies through induction of the B cell survival factor BAFF. A temporary, short-term increase in IL-33 results in a primary (IgM) response to self-antigens. This transient DNA-specific autoantibody response was dependent on the induction of BAFF. Notably, radiation resistant cells and not myeloid cells, such as neutrophils or dendritic cells were the major source of BAFF and were critical in driving the autoantibody response. Chronic exposure to IL-33 elicited dramatic increases in BAFF levels and resulted in elevated numbers of B and T follicular helper cells as well as germinal center formation. We also observed class-switching from an IgM to an IgG DNA-specific autoantibody response. Collectively, the results provide novel insights into a potential mechanism for breaking immune-tolerance via IL-33-mediated induction of BAFF

IL-23 plays a critical role in the arthritis flare-up reaction.

<p>In C57BL/6 mice, antigen-induced arthritis (AIA) was induced. Four weeks after the induction of AIA either IgG control or anti-IL-23p19 was administrated intra-peritoneally weekly for 5 weeks. One day after the final injection mice were given an intra-articular injection with mBSA to induce a flare-up or were left untreated. (<b>A</b>) Twenty-four hours later, knee joints were assessed macroscopically on a 0–2 scale. Each symbol represents data from an individual knee joint and the horizontal line depicts the median. Data are from n = 5 mice per group assessing both knee joints. *P<0.05; **P<0.01; ***P<0.001 by Mann-Whitney U test. (<b>B</b>) Cells from the knee-joints were isolated, RNA was extracted and gene expression for the indicated genes was quantified by quantitative RT-PCR and normalized for GAPDH. Data are the mean+SEM from 5 mice per group.</p

Neutralizing IL-23 after onset of CIA does not ameliorate disease activity.

<p>CIA was induced in DBA/1 mice and directly after the first signs of CIA anti-IL-23p19 or control antibody was injected when an arthritis score between 0.5–1.5 was observed. (<b>A</b> and <b>C</b>) Arthritis severity was scored macroscopically. Numbers on the x-axis indicate the day after the first injection with either antibody and the arrows indicate each time point an injection was given. Data are from (<b>A</b>) n = 8 and (<b>B</b>) n = 10 mice per group. (<b>B and D</b>) At the end of each experiment, serum was collected and anti-CII antibody production of the IgG1, IgG2a and IgG2b subclasses was measured.</p

Primers used in this study.

*<p>refers to the Roche Universal probe library kit.</p

IL-23 does not enhance CII-specific IL-17A production.

<p>(<b>A</b>) DBA/1 mice were immunized with CFA only, with CII/CFA or left untreated. At days 10 (CFA and CFA/CII) and 25 (CFA/CII) post-immunization, splenocytes were isolated and assessed for intracellular expression of IL-17A and IFN-γ. Numbers in quadrant indicate percentage positive cells in that quadrant. Plots are representative of n = 3–6 per group. (<b>B</b>) IL-17A and IFN-γ secretion levels after antigen (CII) specific restimulation of purified splenic CD4+ T cells with irradiated APCs in the absence (−) or presence of exogenous IL-23. Data are the mean +SEM from n = 3 mice per group and *P<0.05; **P<0.01; ***P<0.001 as calculated by Mann-Whitney U test.</p

Administration of anti-IL-23p19 before onset prevents full-blown CIA.

<p>(<b>A</b>) DBA/1 mice were immunized with CII/CFA and three weeks later mice received a booster-injection. On days 15, 22 and 29 either anti-IL-23p19 (filled squares) or control antibody (open circles) was given intra-peritoneally. Macroscopic score (+SEM) and the average macroscopic score (average macroscopic score per individual mouse of all time points assessed, assessed by student t-test) of n = 20 mice per group from 2 independent experiments is shown, as well as the incidence.</p