Oliver Neuhaus

Mechanisms of action of glatiramer acetate in multiple sclerosis

Glatiramer acetate (GA, Copaxone [Teva Pharmaceuticals, Kansas City, MO], formerly known as copolymer-1) and interferon- (IFN)-β are both used for the immunomodulatory treatment of multiple sclerosis, but they act in different ways. Four major mechanisms of GA have been identified: 1) competition with myelin-basic protein (MBP) for binding to major histocompatibility complex (MHC) molecules; 2) competition of GA/MHC with MBP/MHC for binding to the T-cell receptor; 3) partial activation and tolerance induction of MBP-specific T cells (action as an altered peptide ligand); and 4) induction of GA-reactive T-helper 2- (TH2)-like regulatory cells. Of these four mechanisms, 1 and 2 presumably occur only in vitro and are therefore irrelevant for the in vivo effects of GA. In contrast, mechanisms 3 and 4 could occur in vivo and both could contribute to the clinical effects of GA.

Statins as immunomodulators Comparison with interferon-β1b in MS

Background Recent data suggest that statins may be potent immunomodulatory agents. In order to evaluate the potential role of statins as immunomodulators in MS, the authors studied their immunologic effects in vitro and compared them to interferon (IFN)&bgr;-1b. Methods Peripheral blood mononuclear cells (PBMC) obtained from untreated or IFN&bgr;-1–treated patients with relapsing-remitting MS or from healthy donors (HD) and T cells were stimulated with concanavalin A, phytohemagglutinin, or antibody to CD3 in the presence of lovastatin, simvastatin, mevastatin, IFN&bgr;-1b, or statins plus IFN&bgr;-1b. The authors analyzed proliferative activity of T cells and B cells, cytokine production and release, activity of matrix metalloproteinases (MMP), and surface expression of activation markers, adhesion molecules, and chemokine receptors on both T and B cells. Results All three statins inhibited proliferation of stimulated PBMC in a dose-dependent manner, with simvastatin being the most potent, followed by lovastatin and mevastatin. IFN&bgr;-1b showed a similar effect; statins and IFN&bgr;-1b together added their inhibitory potentials. Furthermore, statins reduced the expression of activation-induced adhesion molecules on T cells, modified the T helper 1/T helper 2 cytokine balance, reduced MMP-9, and downregulated chemokine receptors on both B and T cells. Besides strong anti-inflammatory properties, statins also exhibited some proinflammatory effects. Conclusions Statins are effective immunomodulators in vitro that merit evaluation as treatment for MS.

Immunomodulation in multiple sclerosis: from immunosuppression to neuroprotection.

Multiple sclerosis (MS) is the most common disabling neurological disease of young adulthood. Following advances in the understanding of the immunological mechanisms that underlie the pathogenesis of MS, a growing arsenal of immunomodulatory agents is available. Two classes of immunomodulators are approved for long-term treatment of MS, the efficacy of several promising new concepts is being tested in clinical trials and classical immunosuppressive agents used in MS treatment have been shown to exert specific, immunomodulatory effects. Furthermore, two recent observations have changed our basic understanding of the pathogenesis of MS. First, immune cells in MS lesions have neuroprotective activity, which indicates a beneficial role of neuroinflammation. Second, there is evidence that axonal loss, rather than demyelination, underlies the progression of MS and, hence, constitutes a therapeutic target.

Glatiramer acetate in the treatment of multiple sclerosis: emerging concepts regarding its mechanism of action.

Glatiramer acetate is a synthetic, random copolymer widely used as a first-line agent for the treatment of relapsing-remitting multiple sclerosis (MS). While earlier studies primarily attributed its clinical effect to a shift in the cytokine secretion of CD4+ T helper (Th) cells, growing evidence in MS and its animal model, experimental autoimmune encephalomyelitis (EAE), suggests that glatiramer acetate treatment is associated with a broader immunomodulatory effect on cells of both the innate and adaptive immune system. To date, glatiramer acetate-mediated modulation of antigen-presenting cells (APC) such as monocytes and dendritic cells, CD4+ Th cells, CD8+ T cells, Foxp3+ regulatory T cells and antibody production by plasma cells have been reported; in addition, most recent investigations indicate that glatiramer acetate treatment may also promote regulatory B-cell properties. Experimental evidence suggests that, among these diverse effects, a fostering interplay between anti-inflammatory T-cell populations and regulatory type II APC may be the central axis in glatiramer acetate-mediated immune modulation of CNS autoimmune disease. Besides altering inflammatory processes, glatiramer acetate could exert direct neuroprotective and/or neuroregenerative properties, which could be of relevance for the treatment of MS, but even more so for primarily neurodegenerative disorders, such as Alzheimer’s or Parkinson’s disease. In this review, we provide a comprehensive and critical overview of established and recent findings aiming to elucidate the complex mechanism of action of glatiramer acetate.

Are statins a treatment option for multiple sclerosis

BACKGROUND Treatment options for multiple sclerosis (MS) are limited. The immunomodulatory drugs interferon beta and glatiramer acetate are only partly effective in reducing the relapse rate, slowing disease progression, and diminishing the number and volume of lesions on MRI. Mitoxantrone is an immunosuppressant approved for the treatment of active forms of relapsing-remitting or secondary progressive MS, but is dose-limited owing to its potential cardiotoxicity. Thus, identifying new effective therapeutic options with few side-effects is highly desirable. RECENT DEVELOPMENTS Evidence has emerged that statins, which are inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, have immunomodulatory effects. Recent reports showed that statins prevent and reverse chronic and relapsing experimental autoimmune encephalomyelitis, an animal model of MS. Furthermore, in vitro experiments with human immune cells have shown an immunomodulatory profile of statins comparable to that of interferon beta. An open label clinical trial of simvastatin for MS revealed a significant decrease in the number and volume of new MRI lesions and a favourable safety profile. WHERE NEXT?: The obvious advantage of statins over existing MS therapies is their oral route of dosing. Statins might be beneficial for MS patients as monotherapy or as an add-on to established disease modifying drugs. As the evidence of the benefit of statins in MS is currently insufficient, large controlled clinical trials are needed. The first of these trials is about to start.

Monocyte-derived HLA-G acts as a strong inhibitor of autologous CD4 T cell activation and is upregulated by interferon-β in vitro and in vivo: rationale for the therapy of multiple sclerosis

Peripheral antigen presenting cells (APCs) contribute to the maintenance of immune tolerance and are considered to play a critical role in promoting the (re)activation of autoreactive T cells in multiple sclerosis (MS). Interferon-beta (IFN-beta) is the principle immune-modulatory agent used in the treatment of MS, but its mechanism of action remains elusive. HLA-G is a non-classical MHC molecule (MHC class Ib) attributed chiefly immune-regulatory functions. We here investigated the role of monocyte-derived HLA-G in the immune-regulatory processes of MS and its implications for current immune-modulatory therapies. Monocytes constitutively express cell surface HLA-G1 and soluble HLA-G5. Comparison of monocytic HLA-G expression between patients with relapsing-remitting MS (n=17) and healthy donors (n=20) revealed significantly lower levels of HLA-G1 protein in MS patients. However, both groups showed a significant upregulation of HLA-G in response to IFN-beta in vitro. Serial measurements of HLA-G mRNA levels in MS patients before and during IFN-beta therapy corroborated the relevance of these results in vivo: 1 month after initiation of IFN-beta1b therapy (n=9), HLA-G1 and HLA-G5 were significantly increased compared to baseline levels and remained elevated during treatment for 6 months (n=3). Importantly, functional experiments demonstrated that monocyte-derived HLA-G inhibits both Th1 (IFN-gamma, IL-2) and Th2 (IL-10) cytokine production by antigen-stimulated autologous CD4 T cells. Soluble HLA-G added to antigen-specific T cell lines (TCLs) has similar effects on the release of cytokines and reduces T cell proliferation. Although both IFN-beta and IFN-gamma strongly enhance HLA-G1 and HLA-G5 expression by monocytes in vitro, IFN-beta leads to a stronger relative upregulation of HLA-G compared to classical MHC class I molecules than stimulation with IFN-gamma. Taken together, monocyte-derived HLA-G mediates the inhibition of autologous CD4 T cell activation and might be involved in immune-regulatory pathways in the pathogenesis of MS. We conclude that some desirable immune-modulatory effects of INF-beta might be accomplished via the upregulation of the immune-tolerogenic molecule HLA-G.

Neuromyelitis optica: Evaluation of 871 attacks and 1,153 treatment courses.

Neuromyelitis optica (NMO) attacks often are severe, are difficult to treat, and leave residual deficits. Here, we analyzed the frequency, sequence, and efficacy of therapies used for NMO attacks.

Multiple sclerosis: Mitoxantrone promotes differential effects on immunocompetent cells in vitro

Mitoxantrone is an anti-neoplastic anthracenedione derivative that, based on its immunosuppressive properties, is approved for the treatment of severe forms of relapsing-remitting or secondary progressive multiple sclerosis (MS). Whether the beneficial clinical effects of mitoxantrone in MS are due to a broad immunosuppression, or whether there is a specific mechanism of action remains unknown. Peripheral blood mononuclear cells (PBMCs) from untreated or interferon-beta-treated patients with MS or from healthy donors were stimulated in the presence or absence of mitoxantrone. Irrespective of the source of the cells and the cellular phenotype, mitoxantrone inhibited proliferation of activated PBMCs, B lymphocytes, or antigen-specific T-cell lines (TCLs) stimulated on antigen-presenting cells (APCs) in a dose-dependent manner. For functional analysis, TCLs or APCs were incubated separately with mitoxantrone. Pre-incubation of APC more effectively impaired TCL proliferation than pre-incubation of TCLs. Production of cytokines, expression of activation markers, matrix metalloproteinases, and chemokine receptors were not influenced substantially by mitoxantrone. In contrast, in dendritic cells (DCs), mitoxantrone interfered with the antigen-presenting capabilities. For evaluation of apoptotic cell death of target cells, annexin-V-conjugates and a DNA fragmentation assay were applied. Mitoxantrone induced apoptosis of PBMCs, monocytes and DCs at low concentrations, whereas higher doses caused cell lysis. Our observations suggest that the beneficial effects of mitoxantrone in MS result (i) from its immunosuppressive action based on nonspecific cytotoxic effects on lymphocytes, (ii) by inducing programmed cell death of professional APCs, such as DCs.

Secretion of brain-derived neurotrophic factor by glatiramer acetate-reactive T-helper cell lines: Implications for multiple sclerosis therapy

Treatment with glatiramer acetate (GA) is thought to induce an in vivo change of the cytokine secretion pattern and the effector function of GA-reactive T helper (TH) cells (TH1-TH2-shift). Current theories propose that GA-reactive TH2 cells can penetrate the CNS, since they are activated by daily immunization. Inside the CNS, GA-reactive T cells may cross-react with products of the local myelin turnover presented by local antigen-presenting cells (APCs). Thus, some of the GA-specific TH2 cells may be stimulated to release anti-inflammatory cytokines inhibiting neighbouring inflammatory cells by a mechanism called bystander suppression. We demonstrate that both GA-specific TH2 and TH1 cells produce the neurotrophin brain-derived neurotrophic factor (BDNF). To demonstrate that GA-reactive T cells produce BDNF, we analyzed GA-specific, long-term T-cell lines (TCLs) and used a combination of reverse-transcription PCR and two specially designed techniques for BDNF protein detection: one was based on ELISA of supernatants from co-cultures of GA-specific TCLs plus GA-pulsed antigen-presenting cells, and the other, on the direct intracellular staining of BDNF in individual T cells and flow-cytometric analysis. The different assays and different TCLs yielded similar, consistent results. All GA-specific TH1, TH2 and TH0 lines could be stimulated to produce BDNF.

Autoimmune CD4+ T cell memory: lifelong persistence of encephalitogenic T cell clones in healthy immune repertoires.

We embedded green fluorescent CD4+ T cells specific for myelin basic protein (MBP) (TMBP-GFP cells) in the immune system of syngeneic neonatal rats. These cells persisted in the animals for the entire observation period spanning >2 years without affecting the health of the hosts. They maintained a memory phenotype with low levels of L-selectin and CD45RC, but high CD44. Although persisting in low numbers (0.01–0.1% of lymph node cells) they were sufficient to raise susceptibility toward clinical autoimmune disease. Immunization with MBP in IFA induced CNS inflammation and overt clinical disease in animals carrying neonatally transferred TMBP-GFP cells, but not in controls. The onset of the clinical disease coincided with mass infiltration of TMBP-GFP cells into the CNS. In the periphery, following the amplification phase a rapid contraction of the T cell population was observed. However, elevated numbers of fully reactive TMBP-GFP cells remained in the peripheral immune system after acute experimental autoimmune encephalomyelitis mediating reimmunization-induced disease relapses.