ABSTRACT
Several latent infectious agents have been associated recently with human neurological disease. However, the appearance of infectious agents within the central nervous system (CNS) does not always induce pathogenesis. Here, we will discuss the putative association of specific human herpesvirus family members, endogenous retroviruses, coronaviruses and Chlamydia pneumoniae in the pathogenesis of the demyelinating disease, multiple sclerosis (MS) as well as other diseases of the CNS. Because human herpesvirus type 6 (HHV-6) has received extensive attention in recent years, we will discuss in detail the pros and cons for involvement of this virus in the pathogenesis of MS. Other research has implicated a role for the reactivation of endogenous retroviruses or coronaviruses in MS. Further, a non-viral entity C. pneumoniae also is implicated as a causative agent. How can so many different agents cause a selective pathological response? Current thinking suggests that a two-step process is involved in the autoimmunity of MS which individuals who are genetically predisposed are
exposed to an infectious trigger that removes tolerance of T cells. Removal of Tcell tolerance by infectious agents activating the Toll receptor family for example, would enable autoimmune cells to attack self-antigens. If true, this hypothesis would help to explain why so many infectious agents have been associated with MS.
