Effects of Antiviral Therapies on Epstein-Barr Virus Replication

The proposed trial is built on the premise that multiple sclerosis (MS) is, in part, triggered by infection with the human herpesvirus Epstein Barr virus (EBV), and that targeting the virus could be a more effective and safer strategy for MS treatment than immunomodulation or immunosuppression alone. The evidence supporting a causal role for EBV in MS initially came from epidemiological studies that showed similarities in the distribution of infectious mononucleosis and MS, a 2-3 fold increased MS risk among individuals with a clinical history of infectious mononucleosis, and by compelling evidence that MS rarely, if ever, develops in individuals who are not infected with EBV. Furthermore, in a longitudinal study based on the Department of Defense Serum Repository with samples from over 7 million young adults free of MS, individuals who were EBV-seronegative at baseline did not develop symptoms of MS until at least several months after EBV seroconversion, and high serum antibody titers against the EBV-encoded nuclear antigen-1 were associated with an over 30-fold increase in MS risk. Antiviral agents repurposed from treating other herpesviruses, like acyclovir or valacyclovir, have had minimal clinical efficacy against EBV in studies for infectious mononucleosis and multiple sclerosis. Prodrugs of tenofovir, such as tenofovir disoproxil fumarate (TDF), are significantly more potent inhibitors of EBV replication in cell culture than other drugs that have been clinically ineffective for EBV. TDF is a safe drug used clinically for HIV pre-exposure prophylaxis (PrEP) in HIV-negative patients as the drug Truvada. Truvada has been widely used since its approval in 2004 for the treatment of human immunodeficiency virus (HIV), and has a well-known safety profile that makes it a good candidates for clinical studies.