Prognostic value of JC virus load in cerebrospinal fluid of patients with progressive multifocal leukoencephalopathy.

JC virus (JCV) load was determined by using quantitative polymerase chain reaction in cerebrospinal fluid (CSF) of 12 patients with AIDS-associated progressive multifocal leukoencephalopathy (PML) and compared with clinical outcome. JCV loads varied widely (3-7 log10 JCV equivalents/mL of CSF) and were apparently not related to absolute CD4 cell counts or CSF and plasma human immunodeficiency virus type 1 loads. A significant correlation was observed between JCV load and survival time (Spearman's rank correlation, -0.83; P<. 01). Moreover, CSF JCV load decreased and then became undetectable in 1 PML patient receiving cidofovir treatment, and this was associated with clinical improvement. These results show that CSF JCV load may be useful as a prognostic parameter and in monitoring the effectiveness of anti-JCV therapies in PML patients.