bInfection with Theiler's murine encephalomyelitis virus (TMEV) in the central nervous system (CNS) of susceptible mice results in an immune-mediated demyelinating disease which is considered a relevant viral model of human multiple sclerosis. We previously demonstrated that the expression of positive costimulatory molecules (CD40, CD80, and CD86) is higher on the microglia of TMEV-resistant C57BL/6 (B6) mice than the microglia of TMEV-susceptible SJL/J (SJL) mice. In this study, we analyzed the expression levels of the negative costimulatory molecules PD-1 and PDL-1 in the CNS of TMEV-infected SJL mice and B6 mice. Our results indicated that TMEV infection induces the expression of both PD-1 and PDL-1 on microglia and macrophages in the CNS but not in the periphery. The expression of PD-1 only on CNS-infiltrating macrophages and not on resident microglia was considerably higher (>4-fold) in TMEV-infected SJL mice than TMEV-infected B6 mice. We further demonstrated that interleukn-6 (IL-6) is necessary to induce the maximal expression of PDL-1 but not PD-1 after TMEV infection using IL-6-deficient mice and IL-6-transgenic mice in conjunction with recombinant IL-6. In addition, cells from type I interferon (IFN) receptor knockout mice failed to upregulate PD-1 and PDL-1 expression after TMEV infection in vitro, indicating that type I IFN signaling is associated with the upregulation. However, other IFN signaling may also participate in the upregulation. Taken together, these results strongly suggest that the expression of PD-1 and PDL-1 in the CNS is primarily upregulated following TMEV infection via type I IFN signaling and the maximal expression of PDL-1 additionally requires IL-6 signaling.
The therapeutic potency of M2000 (beta-D-mannuronic acid), a novel designed nonsteroidal anti-inflammatory drug with immunosuppressive property in T-cell-mediated autoimmune disease, was tested. The influence of M2000 on myelin basic protein (MBP)-induced experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, was assessed. M2000 at two doses, 40 and 80 mg/kg/day, was administered intraperitoneally (i.p.) to prevention and treatment groups, respectively. Onset of i.p. injections of M2000 to prophylactic and therapeutic groups was day-1 and day-7 postimmunization. The WEHI-164 cell line was used for assaying the tolerability against M2000. The results of this experiment showed that the treatment of EAE with M2000 could significantly suppress disease development both prophylactically and therapeutically; the onset and symptoms of EAE in Lewis rats could be suppressed following the administration of M2000. Clinical improvement was accompanied by a marked decrease in mean numbers of vessels with perivascular cellular infiltration in M2000-treated rats compared with nontreated control. Disease suppression was associated with a marked suppression of MBP-specific T-cell reactivity in vitro, without any evidence for a generalized impairment of T-cell activity. Moreover, M2000 also showed a very high tolerability compared with certain steroidal and nonsteroidal anti-inflammatory drugs. Collectively, our data suggest that M2000 may provide a novel therapeutic option for T-cell-mediated autoimmune diseases in animal models and possibly in humans.
We examined the role of Notch ligand Delta-like 4 (Dll4) in the development of Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease (TMEV-IDD). Treatment with mAb to Dll4, especially during the effector phase, resulted in significant suppression of the disease development both clinically and histologically. The number of infiltrating mononuclear inflammatory cells in the spinal cords was also decreased in mice treated with anti-Dll4 mAb. Semi-quantitative analysis of mRNA by using real-time PCR revealed that mRNAs of T(h)1-derived cytokines such as IFN-gamma and T(h)17-derived cytokines such as IL-17 were decreased in mice treated with anti-Dll4 mAb, whereas those of T(h)2-derived cytokines such as IL-4 and IL-10 were not. Flow cytometric analysis of cytokines indicated that there were no significant differences between mAb-treated mice and control mice in the relative frequency of splenic T(h)1 and T(h)2. However, absolute cell numbers of T(h)1-derived cytokine-producing cells in spinal cord were markedly decreased in mice treated with anti-Dll4 mAb in effector phase compared with control mice treated with non-specific IgG. These data suggest that Dll4 is critically involved in the pathogenesis of TMEV-IDD and that antibodies to Dll4 could be used as a novel therapeutic treatment of demyelinating diseases such as human multiple sclerosis.
The levels of tumor necrosis factor (TNF)-alpha producing cells were analyzed in mice with Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD). Using an ELISPOT assay, we demonstrate an increase in TNF-alpha producing cells in the spinal cords of TMEV-infected SJL/J mice, especially at an active disease stage. The numbers of TNF-alpha producing cells were extremely high in susceptible SJL/J mice compared with the numbers in resistant BALB/c and C57BL/6 mice. TNF-alpha producing cells were also immunohistochemically identified in active lesions of TMEV-IDD at acute as well as chronic stages. The percentage of TNF-alpha producing cells compared with the total number of cells isolated from spinal cords was higher in TMEV-infected SJL/J mice than resistant BALB/c and C57BL/6 mice. Correspondingly, the level of TNF-alpha was much higher in the culture supernatants of both infiltrating cells in the spinal cords and spleen cells from clinically affected animals than that from similarly treated resistant mice. Treatment of virus-infected mice with a mAb specific for TNF-alpha at the beginning of the onset of disease suppressed the development of the demyelinating disease. These findings suggest that TNF-alpha may play an important role in the pathogenicity of TMEV-IDD.
Intracerebral inoculation of susceptible strains of mice with Theiler’s murine encephalomyelitis virus (TMEV) results in immune-mediated demyelination. Three major T-cell epitopes have previously been identified within the VP1 (VP1233–250), VP2 (VP274–86), and VP3 (VP324–37) capsid proteins in virus-infected SJL/J mice. These epitopes appear to account for the majority (∼90%) of major histocompatibility complex class II-restricted T-cell responses to TMEV. Interestingly, the effect of immunization with synthetic peptides bearing the predominant T-cell epitopes on the course of TMEV-induced demyelination indicates that T cells reactive to the VP1 and VP2 epitopes, but not VP3, accelerate the pathogenesis of demyelination. The predominant pathogenic role of the T cells is verified by similar immunization with the fusion proteins containing the entire individual capsid proteins. The order of appearance and level of T cells specific for the individual epitopes during the course of demyelination are similar to each other. However, cytokine profiles of T cells from virus-infected mice indicate that T cells specific for the VP1 (and perhaps the VP2) epitope are Th1, whereas T cells reactive to VP3 are primarily Th2. These results suggest that Th1-type cells specific for VP1 and VP2 are involved in the pathogenesis of viral demyelination induced by TMEV. Thus, a predominance of Th1-inducing viral epitopes is likely critical for the pathogenesis of demyelination.
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