Chronic viral infections of the central nervous system: Aspects specific to multiple sclerosis

The involvement of a viral infection in the physiopathology of multiple sclerosis has been said to cause certain viruses to target the central nervous system and induce neuroinflammation leading to cell dysfunction, as seen, for example, by demyelination or neuronal death. The most recent results of the literature have focused on the Herpes family viruses (HHV-6 and HHV-4/Epstein-Barr virus) and their possible role in the development of multiple sclerosis. Even if no virus has been identified so far as the multiple sclerosis etiological agent, our aim here is to show that some viruses may be responsible for triggering or sustaining neurological diseases. This is particularly the case for Paramyxoviruses, in the late appearance of functional alterations, Picornaviruses, in inducing a breakdown of immune tolerance, epitope spreading and demyelination, and Herpes viruses in inducing T and B lymphocyte activation, T lymphocytes dysregulation and autoimmunity after their reactivation. Therefore, common viruses can play a role as potential modulators of the immune and nervous systems which, in the specific context of dysimmunity and genetic susceptibility, stimulate a favorable background to the development of multiple sclerosis. Tracing and studying viruses in multiple sclerosis patients may improve our understanding of their actual involvement in multiple sclerosis physiopathology. (C) 2009 Elsevier Masson SAS. All rights reserved.