An infectious basis for multiple sclerosis - Perspectives on the role of Chlamydia pneumoniae and other agents

The aetiology of multiple sclerosis (MS) remains unknown. Epidemiological, clinical and pathological data support the theory that MS is a complex dise ase/syndrome with many factors affecting its development and progression. I t may be appropriate to regard MS as a syndrome with differing clinical and pathological features occurring along a spectrum. Patients with MS an more likely to have an affected relative than are individuals without MS, which suggests that there is a genetic component to this illness. Despite this g enetic susceptibility, 85% of MS patients do not have an affected relative and only 1 in 3 monozygotic (identical) twins develops MS if the other twin already has it. These data strongly suggest that environmental factors inf luence the development of MS. Many putative infectious agents have been proposed to be involved in the ae tiology of MS. Although research into identifying MS-causative agents dates back for more than 5 decades, no agent has yet emerged with any consensus as the cause of MS. This controversy is due to a number of factors, includi ng lack of specificity of an agent to MS, lack of reproducibility in other laboratories, inappropriate controls, laboratory contamination and lack of a standard and easily reproducible assay system. Chlamydia pneumoniae is a recently described pathogen that may have a role in the pathogenesis of MS. C. pneumoniae is an intracellular bacterial orga nism that is infectious to humans. It has recently been detected in the cer ebrospinal fluid (CSF) of MS patients but not in that of patients with othe r neurological diseases. There is also a case report of a patient with CNS C. pneumoniae infection and rapidly progressive MS responding to antimicrob ial therapy directed against this pathogen. An association between C. pneum oniae in the CSF and MS is now apparent, but its role in the development of MS remains unknown. Further work exploring the role of C. pneumoniae in inflammatory demyelinat ion is required. This may be accomplished either by developing an animal mo del or in a therapeutic trial in patients with MS.