Longitudinal testing of samples from Multiple Sclerosis patients positive for JCV DNA in urine, and/or serum, and/or PBMCs. Black boxes correspond to positive samples, white boxes to negative samples. JCV viral load (VL) is indicated for each positive sample and median value are shown at the bottom. Patients with PBMCs analyzed for JCV-specific immunity are underlined. For each patient anti-JCV antibody status and any clinical relapse (*) during follow up are also indicated.