Qingyu Cheng

The proteasome inhibitior bortezomib depletes plasma cells and ameliorates clinical manifestations of refractory systemic lupus erythematosus

Objectives To investigate whether bortezomib, a proteasome inhibitor approved for treatment of multiple myeloma, induces clinically relevant plasma cell (PC) depletion in patients with active, refractory systemic lupus erythematosus (SLE). Methods Twelve patients received a median of two (range 1–4) 21-day cycles of intravenous bortezomib (1.3 mg/m2) with the coadministration of dexamethasone (20 mg) for active SLE. Disease activity was assessed using the SLEDAI-2K score. Serum concentrations of anti–double-stranded DNA (anti-dsDNA) and vaccine-induced protective antibodies were monitored. Flow cytometry was performed to analyse peripheral blood B-cells, PCs and Siglec-1 expression on monocytes as surrogate marker for type-I interferon (IFN) activity. Results Upon proteasome inhibition, disease activity significantly declined and remained stable for 6 months on maintenance therapies. Nineteen treatment-emergent adverse events occurred and, although mostly mild to moderate, resulted in treatment discontinuation in seven patients. Serum antibody levels significantly declined, with greater reductions in anti-dsDNA (∼60%) than vaccine-induced protective antibody titres (∼30%). Bortezomib significantly reduced the numbers of peripheral blood and bone marrow PCs (∼50%), but their numbers increased between cycles. Siglec-1 expression on monocytes significantly declined. Conclusions These findings identify proteasome inhibitors as a putative therapeutic option for patients with refractory SLE by targeting PCs and type-I IFN activity, but our results must be confirmed in controlled trials.

Autoantibodies from long-lived 'memory' plasma cells of NZB/W mice drive immune complex nephritis.

Objectives We have previously shown that both short- and long-lived plasma cells (PCs) significantly contribute to autoantibody production in NZB/W mice as a model of lupus nephritis. The aim of this study was to determine the role of autoreactive long-lived (memory) PCs refractory to immunosuppression and B cell depletion in the pathogenesis of systemic lupus erythematosus. Methods Splenic CD138+ antibody-secreting cells (ASCs) from >6-month-old NZB/W mice with high titres of anti-dsDNA autoantibodies or from Balb/c mice 5 days after secondary immunisation with ovalbumin (OVA) were adoptively transferred to immunodeficient Rag1−/− mice, in which the development of nephritis was investigated by measuring proteinuria. Total IgG and IgM as well as anti-dsDNA and anti-OVA antibody levels were followed up by ELISA. After 21 weeks the recipient mice were sacrificed so that PCs in spleen and bone marrow could be analysed using ELISPOT and flow cytometry and renal immunohistology performed. Results The adoptive transfer of NZB/W and anti-OVA ASCs resulted in the continuous generation of anti-dsDNA antibodies and anti-OVA antibodies, respectively, exclusively by long-lived PCs that had homed to the spleen and bone marrow of recipient Rag1−/− mice. Rag1−/− mice generating autoantibodies including anti-dsDNA had reduced survival, proteinuria and immune complex nephritis with C1q, C3, IgG and IgM deposits 21 weeks after transfer. Conclusions These findings demonstrate that autoantibodies exclusively secreted by long-lived (memory) PCs contribute to autoimmune pathology and should be considered as candidate targets for future therapeutic strategies.

gamma-secretase directly sheds the survival receptor BCMA from plasma cells

Survival of plasma cells is regulated by B-cell maturation antigen (BCMA), a membrane-bound receptor activated by its agonist ligands BAFF and APRIL. Here we report that γ-secretase directly cleaves BCMA, without prior truncation by another protease. This direct shedding is facilitated by the short length of BCMAs extracellular domain. In vitro, γ-secretase reduces BCMA-mediated NF-κB activation. In addition, γ-secretase releases soluble BCMA (sBCMA) that acts as a decoy neutralizing APRIL. In vivo, inhibition of γ-secretase enhances BCMA surface expression in plasma cells and increases their number in the bone marrow. Furthermore, in multiple sclerosis, sBCMA levels in spinal fluid are elevated and associated with intracerebral IgG production; in systemic lupus erythematosus, sBCMA levels in serum are elevated and correlate with disease activity. Together, shedding of BCMA by γ-secretase controls plasma cells in the bone marrow and yields a potential biomarker for B-cell involvement in human autoimmune diseases.

Bortezomib Plus Continuous B Cell Depletion Results in Sustained Plasma Cell Depletion and Amelioration of Lupus Nephritis in NZB/W F1 Mice.

Long-lived plasma cells (LLPCs) are an unmet therapeutic challenge, and developing strategies for their targeting is an emerging goal of autoantibody-mediated diseases such as systemic lupus erythematosus (SLE). It was previously shown that plasma cells can be depleted by agents such as bortezomib (Bz) or by blocking LFA-1 and VLA-4 integrins. However, they regenerate quickly after depletion due to B cell hyperactivity in autoimmune conditions. Therefore, we compared different therapies for the elimination of LLPCs combined with selective B-cell targeting in order to identify the most effective treatment to eliminate LLPCs and prevent their regeneration in lupus-prone NZB/W F1 mice. Methods NZB/W F1 mice were treated with: 1) anti-CD20, 2) anti-CD20 plus bortezomib, 3) anti-CD20 plus anti-LFA-1/anti-VLA-4 blocking antibodies, 4) anti-CD20 plus bortezomib and anti-LFA-1/anti-VLA4 blocking antibodies. Short- and long-lived plasma cells including autoreactive cells in the bone marrow and spleen were enumerated by flow cytometry and ELISPOT seven days after treatment. Based on these data in another experiment, mice received one cycle of anti-CD20 plus bortezomib followed by four cycles of anti-CD20 therapy every 10 days and were monitored for its effect on plasma cells and disease. Results Short-lived plasma cells in bone marrow and spleen were efficiently depleted by all regimens targeting plasma cells. Conversely, LLPCs and anti-dsDNA-secreting plasma cells in bone marrow and spleen showed resistance to depletion and were strongly reduced by bortezomib plus anti-CD20. The effective depletion of plasma cells by bortezomib complemented by the continuous depletion of their precursor B cells using anti-CD20 promoted the persistent reduction of IgG anti-dsDNA antibodies, delayed nephritis and prolonged survival in NZB/W F1 mice. Conclusions These findings suggest that the effective depletion of LLPCs using bortezomib in combination with a therapy that continuously targeting B cells as their precursors may prevent the regeneration of autoreactive LLPCs and, thus, might represent a promising treatment strategy for SLE and other (auto)antibody-mediated diseases.

Development and resolution of secondary autoimmunity after autologous haematopoietic stem cell transplantation for systemic lupus erythematosus: competition of plasma cells for survival niches?

Haematopoietic stem cell transplantation (HSCT) is an effective treatment for severe autoimmune diseases such as systemic lupus erythematosus (SLE).1 However, it is increasingly recognised that these patients have an added propensity to develop secondary autoimmune disorders.2 ,3 Here, we report on a 21-year-old male patient who received a CD34-selected autologous HSCT following conditioning with antithymocyte-globulin and cyclophosphamide (CYC) after written informed consent for refractory, severe SLE with renal, haematological, mucocutaneous and musculoskeletal manifestations (SLEDAI 19).1 Clinical remission was achieved for SLE within 3 months after HSCT and anti-double-stranded DNA (anti-dsDNA) antibodies disappeared despite immunosuppressive drug withdrawal. Eight months after HSCT, the patient presented with spontaneous joint and skin bleeding and was diagnosed with factor VIII (FVIII) inhibitor haemophilia with an activated partial thromboplastin time >100 s, FVIII activity <1% and a FVIII inhibitor titre of 435 Bethesda units (figure 1A). At that time point, flow cytometric analyses revealed a drastic increase in B cell numbers, expansion of circulating plasmablasts and a predominance of CD45RO memory CD4 T cells with oligoclonal T cell receptor Vβ expression (table 1), but clinical and laboratory tests showed no evidence of lupus activity. FVIII haemophilia was refractory to methylprednisolone, plasmapheresis, intravenous immunoglobulin (IVIG), intravenous CYC, rituximab and extracorporeal …

Analyzing pathogenic (double-stranded (ds) DNA-specific) plasma cells via immunofluorescence microscopy

IntroductionWhile protective plasma cells (PCs) are an important part of the individual’s immune defense, autoreactive plasma cells such as dsDNA-specific plasma cells contribute to the pathogenesis of autoimmune diseases like systemic lupus erythematosus (SLE). However, the research on dsDNA-specific plasma cells was restricted to the ELISpot technique, with its limitations, as no other attempt for identification of dsDNA-reactive plasma cells had been successful.MethodsWith improved fluorochrome labeling of dsDNA, removal of DNA aggregates, and enhanced blocking of unspecific binding, we were able to specifically detect dsDNA-reactive plasma cells by immunofluorescence microscopy.ResultsVia this novel technique we were able to distinguish short-lived (SLPCs) and long-lived (LLPCs) autoreactive plasma cells, discriminate dsDNA-specific plasma cells according to their immunoglobulin class (IgG, IgM, and IgA) and investigate autoreactive (dsDNA) and vaccine-induced ovalbumin (Ova) plasma cells in parallel.ConclusionsThe detection of autoreactive dsDNA-specific plasma cells via immunofluorescence microscopy allows specific studies on pathogenic and protective plasma cell subsets and their niches, detailed evaluation of therapeutic treatments and therefore offers new possibilities for basic and clinical research.

Proteasome inhibition with bortezomib induces a therapeutically relevant depletion of plasma cells in SLE but does not target their precursors

Long‐lived plasma cells (PCs) not only provide protective humoral immunity, they are also an essential component of the autoreactive immunologic memory that may drive chronic immune responses in systemic autoimmunity, such as systemic lupus erythematosus (SLE). The therapeutic relevance of their targeting has been demonstrated in preclinical models and severe, treatment‐refractory cases of autoimmune diseases using the proteasome inhibitor bortezomib. Herein, we describe in detail the dynamic serologic changes and effects on immune effector cells in eight SLE patients receiving a median two cycles of 1.3 mg/m2 intravenous bortezomib. Upon proteasome inhibition, immunoglobulin levels gradually declined by ∼30%, associated with a significant reduction of autoantibodies, and serum complement whereas B‐cell activation factor levels increased. While proteasome inhibition was associated with a significant depletion of short‐ and long‐lived PCs in peripheral blood and bone marrow by ∼50%, including those with a distinctly mature CD19− phenotype, their precursor B cells and T cells largely remained unaffected, resulting in a rapid repopulation of short‐lived PCs after bortezomib withdrawal, accompanied by increasing autoantibody levels. Collectively, these findings identify proteasome inhibitors as a promising treatment option for refractory SLE, but also indicate that PC depletion needs to be combined with targeted B‐cell therapies for sustained responses in systemic autoimmunity.

FRI0394 The Proteasome Inhibitor Bortezomib Ameliorates Refractory Systemic Lupus Erythematosus (SLE): A Prospective Multi-Centre Observational Study

Objectives The proteasome inhibitor bortezomib, approved for the therapy of multiple myeloma, depletes plasma cells (PCs) and ameliorates nephritis in mouse models of systemic lupus erythematosus (SLE). Here, we analyzed the efficacy of bortezomib as induction therapy in patients with refractory SLE. Methods Twelve patients with active SLE were included in this prospective multicentre cohort study. The patients received one to four cycles of intravenous bortezomib (Velcade®) 1.3mg/m2 as “off-label” treatment. Disease activity was evaluated using the SELENA-SLEDAI score. We determined serum concentrations of anti–double-stranded DNA (anti-dsDNA) and protective antibodies. Multicolor flow cytometry was performed to analyze peripheral blood B and PC subsets as well as Siglec-1 expression on monocytes as surrogate marker for type I interferon (IFN) activity. Results The disease activity significantly decreased upon induction therapy with bortezomib and remained stable for the following 3 months under maintenance therapies. Treatment-related adverse events were mild or moderate. During proteasome inhibition, serum antibody concentrations significantly declined with greater reductions in anti-dsDNA (∼60%) than protective (∼30%) antibodies. Upon bortezomib treatment, numbers of HLA-DR+ short-lived (p=0.024) and HLA-DR– long-lived (p=0.038) peripheral blood PCs were strongly decreased, whereas circulating B cells remained virtually unaffected. Notably, PC numbers significantly increased in-between cycles. Siglec-1 expression on monocytes significantly declined (p<0.001) indicating reduced type 1 IFN activity. Conclusions Bortezomib targeting PCs and type I IFN activation may represent an effective treatment option with rather low toxicity in refractory SLE patients. Bortezomib efficiently induces short-term remissions but requires maintenance treatment inhibiting PC regeneration for sustained efficacy. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.5884

A3.26 Proteasome inhibition with bortezomib in refractory SLE inhibits type I interferon and depletes plasma cells but does not inhibit their regeneration

Background The proteasome inhibitor bortezomib, approved for the treatment of multiple myeloma, has been demonstrated to deplete short- and long-lived plasma cells (PCs) and ameliorate nephritis in murine models of systemic lupus erythematosus (SLE). Here, we aimed to analyse the effect of bortezomib in refractory SLE patients. Methods In this single-centre cohort study, eight SLE patients with active disease despite immunosuppressive treatment received up to four 21-day cycles of bortezomib 1.3mg/m2, on days 1, 4, 8, and 11 by intravenous injection as an “off-label” treatment. Multicolor flow cytometry was performed to analyse peripheral blood B and PC subsets as well as Siglec-1 expression on monocytes. Autoantibody and vaccine titres as well as B cell activating factor (BAFF) levels in serum were analysed with ELISA. Results From 2009 until 2012, eight SLE patients received a median of two bortezomib cycles (range one to four). Under proteasome inhibition, disease activity significantly improved with a median SLEDAI reduction from 13 to 4 (p>0.001). Bortezomib treatment had profound effects on antibody titers, with greater reduction in pathogenic (anti-dsDNA-abs. 58.7%) than protective antibody titers (e.g. anti-Tetanus-abs. 29.2%). In addition, total immunoglobulin levels and Siglec-1 expression on monocytes (as surrogate for type I interferon) significantly decreased (p = 0.016), whereas BAFF and complement levels significantly increased. While circulating B-cell numbers remained unaffected, bortezomib treatment resulted in a significant depletion of both HLA-DR+ short-lived (55.5% reduction, p = 0.024) and HLA-DR- long-lived (53.5% reduction, p = 0.038) peripheral blood PCs. Also IgA secreting PCs were depleted (61.8% reduction). Nevertheless, PCs were rapidly regenerated with a median increase of 268.8% within 10 days from the last bortezomib application. Conclusion Proteasome inhibition with bortezomib has beneficial effects on disease manifestations in SLE by PC depletion and inhibition of type I interferon but regeneration of PCs is not prevented. Overall, proteasome inhibition has demonstrated the therapeutic relevance of targeting autoreactive memory plasma cells as such, and it constitutes a new therapeutic option. Nevertheless, fur sustained efficacy, proteasome inhibition needs to be combined with therapeutic approaches targeting B cell activation and differentiation to inhibit PC regeneration.

S1D:6 Targeting plasma cells and their precursors by immunoablation versus bortezomib plus rituximab in systemic lupus erythemtosus

Purpose To investigate the therapeutic relevance of targeting long-lived plasma cells (PC), which contribute to the chronicity of SLE through continuous secretion of pathogenic antibodies, using immunoablation with antithymocyte-globulin (ATG) in the context of haematopoietic stem cell transplantation (HSCT) or proteasome inhibition with Bortezomib. Methods Prospective analysis of outcome in 10 SLE patients after receiving autologous HSCT between 1998 and 2012 and 8 SLE patients after receiving a median 2 cycles (range 1–4) of Bortezomib 1.3 mg/m2 between 2009 and 2012 at the Charité – University Medicine Berlin. Multiparametric flow cytometry was applied to characterise peripheral blood or bone marrow PC subsets and B cells. Autoantibodies and vaccine titres were investigated with ELISA. Results In all HSCT treated patients clinical remissions (SLEDAI <3) were achieved, accompanied by a complete normalisation of anti-dsDNA antibody titres (92.6% reduction) and a significant reduction of antinuclear antibodies and vaccine titres (measles 82.3%). Peripheral blood B and PCs were virtually absent and bone marrow PCs largely depleted (97.6% reduction, n=1) shortly after HSCT and regenerating B cells almost exclusively displayed a naïve phenotype. Upon proteasome inhibition, clinical improvements were associated with a significant reduction of anti-dsDNA autoantibodies (69.3%) and vaccine titers (measles 32.5%). While B cell number/phenotype remained stable, both bone marrow and circulating PC were significantly reduced (~50%) but rapidly regenerated after proteasome inhibition, which could be prevented by additional rituximab therapy in one patient applied. Conclusions Although less prominent compared to HSCT, proteasome inhibition with Bortezomib promoted a therapeutically relevant PC depletion in refractory SLE. Nevertheless, for sustained responses, PC depletion needs to be combined with therapeutic strategies targeting their precursor B cells, e.g. with rituximab, as indicated by our preclinical studies in murine lupus.