Several options for antiviral treatment trials in multiple sclerosis--but which targets should be selected?

Involvement of viruses in the pathogenesis of multiple sclerosis (MS) is a long-lived hypothesis, which is has not yet been proven nor refuted. This is partly due to difficulties in the evaluation of diagnostic findings on persistent infections by common viruses such as herpesviruses and endogenous retroviruses. Progress in antiviral treatment of central nervous system (CNS) herpesvirus infections has stimulated controlled trials of long-term therapy with acyclovir and valacyclovir in MS, but conclusive results are not yet available. Other treatment possibilities might include anti-retroviral therapy, as well as attempts to counteract the effects of viruses in triggering attacks of MS following upper respiratory tract infections. Before such trials are initiated, however, further diagnostic evidence of the involvement of target viruses seems warranted.