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Infections Increase the Risk for MS Relapses

In this important study, immunologic and MRI data support the hypothesis that acute infections can trigger MS exacerbations.

These authors present a comprehensive study that goes well beyond previous reports in confirming the association of acute infections with clinical and immunologic signs of relapse in 60 patients with relapsing-remitting multiple sclerosis (MS). Of the cohort, 87% were receiving immunomodulatory drug therapy. The authors prospectively assessed clinical MS relapses and infections. Of the 60 patients, 20 also underwent MRI at baseline, at 2 weeks, and at 12 weeks. The "at-risk period" was considered to be 2 weeks before the onset of an acute infection to 5 weeks afterwards.

The risk for relapses was threefold higher during the at-risk period than outside that period. MRI activity was also relatively higher during the at-risk period. Most relapses and gadolinium-enhancing MRI lesions appeared within 2 weeks after an infection and were associated equally with viral and bacterial infections (previous reports had implicated only viruses). The association was similar regardless of the immunomodulatory drugs used (interferon-beta or glatiramer acetate).

In individual patients, the researchers identified T-cell responses that could trigger the process of inflammatory demyelination. However, no specific pathogen was predominantly responsible for MS relapses. Cells secreting proinflammatory cytokines, such as interleukin-12 and interferon-gamma, were found in patients during relapses in the at-risk period but not during relapses at other times. Further, when T-cell lines specific for myelin basic protein and those for myelin oligodendrocyte glycoprotein were stimulated by both the infectious agent and myelin peptide, immune responses were greatly augmented (compared with stimulation by myelin peptide alone).

Comment: Although an association between MS relapses and common respiratory infections was first established more than 20 years ago, the nature of the relationship remains complex and controversial. Like all good scientific experiments, this one raises nearly as many questions as it answers, but it also provides a benchmark for the design of further studies that may have important implications for MS therapy.

— Hillel Panitch, MD

Dr. Panitch is Professor of Neurology, University of Vermont College of Medicine, Burlington.

Published in Journal Watch Neurology December 19, 2006

Citation(s):

Correale J et al. The risk of relapses in multiple sclerosis during systemic infections. Neurology 2006 Aug 22; 67:652-9.

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