Viruses in chronic progressive neurologic disease.

Viruses have long been implicated as triggers of disease onset and progression in multiple sclerosis (MS) and similar neuroinflammatory disorders. Decades of epidemiological, molecular, and pathologic studies have most strongly linked the human herpesviruses Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV-6) with MS. However, these viruses are ubiquitous in the general population and typically acquired decades before disease presentation, complicating the study of how they might contribute to disease. As experimental animal models may help elucidate mechanisms that have linked viruses with MS, we have been studying HHV-6 infections in a small nonhuman primate. We recently demonstrated that the subsequent induction of an MS-like experimental neuroinflammatory disease results in significantly accelerated disease in HHV-6 inoculated marmosets compared to controls. Ultimately, disease intervention in the form of clinical trials with an antiviral agent is the best way to concretely demonstrate a role for HHV-6 or any other virus in MS.