Herbert P.M. Brok

Transfer of Central Nervous System Autoantigens and Presentation in Secondary Lymphoid Organs

Dendritic cells are thought to regulate tolerance induction vs immunization by transferring Ags and peripheral signals to draining lymph nodes (LN). However, whether myelin Ag transfer and presentation in LN occurs during demyelinating brain disease is unknown. In this study, we demonstrate redistribution of autoantigens from brain lesions to cervical LN in monkey experimental autoimmune encephalomyelitis (EAE) and in multiple sclerosis (MS). Immunohistochemical analysis revealed significantly more cells containing myelin Ags in cervical LN of monkeys with EAE compared with those of healthy control monkeys. Myelin Ags were observed in cells expressing dendritic cell/macrophage-specific markers, MHC class II, and costimulatory molecules. Moreover, these cells were directly juxtaposed to T cells, suggesting that cognate interactions between myelin-containing APC and T cells are taking place in brain-draining LN. Indeed, myelin Ag-reactive T cells were observed in cervical LN from marmosets and rhesus monkeys. Importantly, these findings were paralleled by our findings in human tissue. We observed significantly more myelin Ag-containing cells in LN of individuals with MS compared with those of control individuals. These cells expressed APC markers, as observed in marmosets and rhesus monkeys. These findings suggest that during MS and EAE, modulation of T cell reactivity against brain-derived Ags also takes place in cervical LN and not necessarily inside the brain. A major implication is that novel therapeutic strategies may be targeted to peripheral events, thereby circumventing the blood-brain barrier.

Prevention of Experimental Autoimmune Encephalomyelitis in Common Marmosets Using an Anti-IL-12p40 Monoclonal Antibody

The experimental autoimmune encephalomyelitis (EAE) model in the common marmoset approximates recognized features of the human disease multiple sclerosis (MS) with regard to its clinical presentation as well as neuropathological and radiological aspects of the lesions in brain and spinal cord. IL-12 is a proinflammatory cytokine that is produced by APC and promotes differentiation of Th1 effector cells. IL-12 is produced in the developing lesions of patients with MS as well as in EAE-affected animals. Previously it was shown that interference in IL-12 pathways effectively prevents EAE in rodents. In this study we report that in vivo neutralization of IL-12p40 using a novel Ab has beneficial effects in the myelin-induced EAE model in common marmosets. The Ab was injected i.v. at 7-day intervals starting well after immunization (day 14) and was continued until the end of the study (day 86). Stable levels of the Ab were measured 3 days after each injection throughout the study period. During this period anti-Ab responses could not be detected. We demonstrate that anti-IL-12p40 treatment has a protective effect on the neurological dysfunction as well as on neuropathological changes normally observed in the brain and spinal cord of EAE-affected individuals.

Prevention of Experimental Autoimmune Encephalomyelitis in the Common Marmoset ( Callithrix jacchus ) Using a Chimeric Antagonist Monoclonal Antibody Against Human CD40 Is Associated with Altered B Cell Responses

Inhibition of CD40-CD40 ligand interaction is a potentially effective approach for treatment of autoimmune diseases, such as multiple sclerosis. We have investigated this concept with a chimeric antagonist anti-human CD40 mAb (ch5D12) in the marmoset monkey experimental autoimmune encephalomyelitis (EAE) model. Marmosets were immunized with recombinant human myelin oligodendrocyte glycoprotein (rMOG) and treated from the day before immunization (day −1) until day 50 with either ch5D12 (5 mg/kg every 2–4 days) or placebo. On day 41 after the induction of EAE, four of four placebo-treated monkeys had developed severe clinical EAE, whereas all animals from the ch5D12-treated group were completely free of disease symptoms. High serum levels of ch5D12 associated with complete coating of CD40 on circulating B cells were found. At necropsy placebo- and ch5D12-treated animals showed similar MOG-specific lymphoproliferative responses in vitro, but ch5D12 treatment resulted in strongly reduced anti-MOG IgM Ab responses and delayed anti-MOG IgG responses. Most importantly, treatment with ch5D12 prevented intramolecular spreading of epitope recognition. Postmortem magnetic resonance imaging and immunohistologic analysis of the CNS showed a markedly reduced lesion load after ch5D12 treatment. In conclusion, the strong reduction of clinical, pathological, and radiological aspects of EAE by ch5D12 treatment in this preclinical model points to a therapeutic potential of this engineered antagonist anti-CD40 mAb for multiple sclerosis.

Myelin/Oligodendrocyte Glycoprotein-Induced Autoimmune Encephalomyelitis in Common Marmosets: The Encephalitogenic T Cell Epitope pMOG24–36 Is Presented by a Monomorphic MHC Class II Molecule

Immunization of common marmosets (Callithrix jacchus) with a single dose of human myelin in CFA, without administration of Bordetella pertussis, induces a form of autoimmune encephalomyelitis (EAE) resembling in its clinical and pathological expression multiple sclerosis in humans. The EAE incidence in our outbred marmoset colony is 100%. This study was undertaken to assess the genetic and immunological basis of the high EAE susceptibility. To this end, we determined the separate contributions of immune reactions to myelin/oligodendrocyte glycoprotein (MOG) and myelin basic protein to the EAE induction. Essentially all pathological features of myelin-induced EAE were also found in animals immunized with MOG in CFA, whereas in animals immunized with myelin basic protein in CFA clinical and pathological signs of EAE were lacking. The epitope recognition by anti-MOG Abs and T cells were assessed. Evidence is provided that the initiation of EAE is based on T and B cell activation by the encephalitogenic phMOG14–36 peptide in the context of monomorphic Caja-DRB*W1201 molecules.

Suppression of Ongoing Disease in a Nonhuman Primate Model of Multiple Sclerosis by a Human-Anti-Human IL-12p40 Antibody

IL-12p40 is a shared subunit of two cytokines with overlapping activities in the induction of autoreactive Th1 cells and therefore a potential target of therapy in Th1-mediated diseases. We have examined whether ongoing disease in a nonhuman primate model of multiple sclerosis (MS) can be suppressed with a new human IgG1κ Ab against human IL-12p40. Lesions developing in the brain white matter were visualized and characterized with standard magnetic resonance imaging techniques. To reflect the treatment of MS patients, treatment with the Ab was initiated after active brain white matter lesions were detected in T2-weighted images. In placebo-treated control monkeys we observed the expected progressive increase in the total T2 lesion volume and markedly increased T2 relaxation times, a magnetic resonance imaging marker of inflammation. In contrast, in monkeys treated with anti-IL-12p40 Ab, changes in the total T2 lesion volume and T2 relaxation times were significantly suppressed. Moreover, the time interval to serious neurological deficit was delayed from 31 ± 10 to 64 ± 20 days (odds ratio, 0.312). These results, in a disease model with high similarity to MS, are important for ongoing and planned trials of therapies that target IL-12 and/or IL-23.

Non-human primate models of multiple sclerosis.

Summary: The phylogenetic proximity between non‐human primate species and humans is reflected by a high degree of immunological similarity. Non‐human primates therefore provide important experimental models for disorders in the human population that are caused by the immune system, such as autoimmune diseases. In this paper we describe non‐human primate models of multiple sclerosis, a chronic inflammatory and demyelinating disease of the human central nervous system. While reviewing data from the literature and our own research we will discuss the unique role of such models in the research of basic disease mechanisms and the development of new therapies.

Feasibility of Adenovirus-Mediated Nonsurgical Synovectomy in Collagen-Induced Arthritis-Affected Rhesus Monkeys

Gene transfer to synovial tissue by adenoviral vectors (Ad) was studied in vitro in cultured human synoviocytes and in vivo in seven primates with arthritis. Hyperplastic synovium was efficiently transduced with Ad.lacZ in vitro and in vivo in rhesus monkeys with collagen-induced arthritis, whereas chondrocytes were not transduced. Intraarticular injection of recombinant Ad harboring the luciferase gene showed the presence of reporter gene products only in Ad-injected joints. In addition, the feasibility of synovectomy by Ad harboring the herpes simplex virus thymidine kinase gene (tk) was studied. In vitro infection of synovium from rheumatoid arthritis patients with Ad.TK, followed by administration of ganciclovir, resulted in death of >90% of the synoviocytes. By mixing Ad.TK-infected with noninfected cells, it appeared that the presence of 10% infected synoviocytes resulted in the killing of more than 85% of the synoviocytes, demonstrating a substantial bystander effect. Intraarticular injection of Ad.TK in the knees of rhesus monkeys with arthritis, followed by treatment with ganciclovir for 14 days, resulted in increased apoptotic cell death in the synovium of Ad.TK-injected as compared with noninjected joints and ablation of the synovial lining layer. The procedure revealed no toxic side effects. These data suggest that nonsurgical synovectomy by tK gene therapy is feasible.

Demyelination and axonal damage in a non-human primate model of multiple sclerosis

The demyelinating plaque is the paradigmatic lesion of multiple sclerosis (MS), but only recently attention has been given to axonal damage and to its role in the pathophysiology of disease. Albeit the possible relevance of axonal loss in MS and its experimental models, the amount and timing of axonal sufferance has been addressed only in experimental autoimmune encephalomyelitis (EAE) of rodents. In this report we observed that, in the marmoset model of EAE, axonal damage occurs early during the demyelinating process as assessed by immunoreactivity for amyloid precursor protein (APP) and non-phosphorylated neurofilaments (SMI-32 positive) detected mostly in early active lesions compared to late active and normal appearing white matter. The rare occurrence of morphological features of axonal transection, such as APP or SMI-32 positive spheroids and swellings, as well as an increase of neurofilament density in the demyelinated axons without accumulation of electron dense organelles or osmiophilic bodies, at electron microscopy, suggests that early axonal damage may be, at least in part, a reversible process. These findings are of relevance for the development of therapies, which can protect axons and enhance their function and survival.

Rhesus monkeys are highly susceptible to experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein: characterisation of immunodominant T- and B-cell epitopes.

Eight rhesus monkeys with different MHC backgrounds were immunized with myelin oligodendrocyte glycoprotein (MOG). All developed severe experimental autoimmune encephalomyelitis associated with large inflammatory foci and extensive demyelination. T-cell autoreactivity to MOG was directed against three main epitopes encompassed within amino acids 4-20, 35-50 and 94-116, of which two are also immunodominant epitopes for the autoimmune T cell response to MOG in patients with MS. A strong B cell response to MOG was observed in all monkeys and major epitopes recognized were located within amino acids 4-26, 24-46 and 44-66/54-76.

Protection of marmoset monkeys against EAE by treatment with a murine antibody blocking CD40 (mu5D12)

CD40‐CD40 ligand interactions are crucial to cognate interactions between T cells, B cells and antigen‐presenting cells (APC), and contribute to non‐antigen‐specific effector functions of APC in inflammatory disorders. Here we demonstrate that functional blockade of CD40 with an antagonist mouse anti‐human CD40 monoclonal antibody (mAb mu5D12) effectively prevents clinical expression of chronic demyelinating experimental autoimmune encephalomyelitis (EAE) in outbred marmoset monkeys, a preclinical model of multiple sclerosis. Anti‐CD40 mAb interfered with development of clinical symptoms of marmoset EAE during the treatment period, even when treatment was started several weeks after T cell priming. Magnetic resonance imaging demonstrated inflammatory activity in the brain at initiation of antibody treatment, confirming that treatment interfered with the disease process. Access of therapeutic anti‐CD40 to potential sites of action, the secondary lymphoid organs and the brain white matter lesions, was visualized in situ. The present data are the first to demonstrate the clinical potential of blocking APC and effector cell functions using murine antagonist anti‐CD40 mAb in the treatment of chronic inflammatory diseases.