Virus infection in demyelinating diseases.

Several animal and human demyelinating diseases of the central nervous system (CNS) are associated with RNA or DNA viruses. These viruses infect CNS cells lytically or persistently. They mainly belong to the group of envelope viruses which derive their envelope partly from the host cell membrane. The process of virus release may result in the appearance of new antigens of virus-infected cells or the incorporation of cell membrane material into the viral envelope. These changes may lead to an immune response which selectively injures the CNS. These alterations of host cell membranes and host cell functions, together with the immune mechanism, are central to many of the hypotheses regarding virus-induced demyelination. The role of virus infection in progressive multifocal leukoencephalopathy, subacute sclerosing panencephalitis, visna and mouse hepatitis virus infections, is discussed in relation to the demyelinating process of these diseases.