Mouse models of multiple sclerosis: lost in translation?

Multiple sclerosis (MS) is a chronic neurological disorder of the central nervous system (CNS) leading to progressive accumulation of neurological deficits arising from recurrent episodes of inflammation, demyelination and neuronal degeneration. While the aetiology of the disease is unknown MS is widely considered to be the result of aberrant T cell and antibody responses to CNS antigens giving rise to the common concept that MS is an autoimmune disease or that there is an autoimmune component in the pathogenesis. This idea has lead to the development of experimental autoimmune encephalomyelitis (EAE) mouse models of MS in which immunisation with CNS antigens induces neurological and pathological signs of disease in mice. In addition to EAE models, injection with neurotropic viruses has been used to examine how infections are implicated in the disease process and how they may generate autoimmune responses in the CNS. Viral models are also crucial to investigate the impact of blocking trafficking of immune responses into the CNS since an emerging side-effect of current immunotherapeutic approaches in MS is the reactivation of viruses within the CNS. To investigate myelin damage and repair in the absence of the adaptive immune response, toxin-induced demyelination using cuprizone, ethidium bromide and lysolecithin, which rapidly leads to remyelination when the toxins are withdrawn, is also reviewed. Mice also lend themselves to the vast array of transgenic technologies to probe specific pathways as well as the use of humanised transgenic mice to examine the impact of human molecules. Despite the vast array of mouse models EAE is the most frequently exploited paradigm used to develop therapeutic approaches. However, despite over one thousand compounds used in the treatment of EAE few have become licenced for treatment of MS so far. Thus, this review also debates the reasons for these failures in mouse models as well as discusses how mouse models can be better utilised to provide more powerful preclinical tools to develop rational therapies for multiple sclerosis.