Citations

The RNA-dependent RNA-polymerase,3Dpol, is an essential component in the picornavirus genome for the replication of single stranded RNA. However, transgenic expression of3Dpolin mice has antiviral effects. Here, we discuss the structure and function of3Dpolduring picornavirus replication, we review the evidence and consequence of a host immune response to epitopes in3Dpolafter picornavirus infection, highlight data showing the antiviral effects of transgenic3Dpolfrom Theiler's murine encephalomyelitis virus (TMEV), and discuss potential mechanisms by which3Dpolis causing this antiviral effect in mice.

The potential for endogenous remyelination and axonal protection can be an important factor in determining disease outcome in demyelinating diseases like multiple sclerosis. In many multiple sclerosis (MS) patients CNS repair fails or is incomplete whereas in others the disease is accompanied by extensive repair of demyelinated lesions. We have described significant differences in the ability of two strains of mice to repair CNS damage following Theiler’s virus-induced demyelination: FVB/NJ (FVB) mice repair damaged myelin spontaneously and completely, whereas B10.D1-H2 q /SgJ (B10.Q) mice are deficient in the repair process. A QTL analysis was performed to identify genetic loci that differentially regulate CNS repair following chronic demyelination in these strains and two QTL were detected: one on chromosome 3 with a LOD score of 9.3 and a second on chromosome 9 with a LOD score of 14.0. The mouse genes for epidermal growth factor (EGF) and Tyk2 are encoded within the QTL on chromosomes 3 and 9, respectively. Sequence polymorphisms between the FVB and B10.Q strains at both the EGF and Tyk2 loci define functional variations consistent with roles for these genes in regulating myelin repair. EGF is a key regulator of cell growth and development and we show a sevenfold increase in EGF expression in FVB compared to B10.Q mice. Tyk2 is a Janus kinase that plays a central role in controlling the T H 1 immune response and we show that attenuation of Tyk2 function correlates with enhanced CNS repair.

Stimulation of remyelination in multiple sclerosis lesions may be one possible therapeutic approach. However, since the pathology and pathogenesis of multiple sclerosis may be heterogeneous, it is important to analyze in what patients and at what stages of the disease such a therapy can be reasonable and feasible. Spontaneous remyelination is pronounced in some MS patients. The extent of remyelination correlates well with the presence of oligodendrocytes in the lesions. Yet, the source and origin of the remyelinating cells is still unclear. These may be derived from either undifferentiated progenitor cells or, in part from mature oligodendrocytes, that have escaped destruction during lesional activity. Complete remyelination of plaques is possible, leading to the formation of 'shadow plaques'. No reliable data are available at present on the frequency of remyelination in different forms of MS. However, most studies agree that remyelination is especially prominent at the early stages of the disease, whereas it is sparse after several years of disease duration. In addition, very little remyelination is found in cases of primary progressive MS.

Studies in both humans and experimental animals indicate that there is potential for full remyelination following CNS demyelination, but the factors that control the degree of myelin repair are unknown. In the Theiler's virus model of demyelination CNS remyelination can be promoted either by global immunosuppression or by selective immunoglobulin therapy. In this paper we discuss whether immunoglobulin-mediated remyelination is a characteristic of immune-mediated demyelination, or whether immunoglobulin-mediated remyelination also occurs in the toxic-traumatic model of lysolecithin-induced demyelination. Our data support the hypothesis that even in a non-primary immune model of demyelination, manipulating the immune system can be beneficial in myelin repair.