Characterization of the VP1 loop mutations widespread among JC polyomavirus isolates associated with progressive multifocal leukoencephalopathy.

Recently, we found that JC polyomavirus (JCPyV) associated with progressive multifocal leukoencephalopathy (PML) frequently undergoes amino acid substitutions (designated VP1 loop mutations) in the outer loops of the major capsid protein, VP1. To further characterize the mutations, we analyzed the VP1 region of the JCPyV genome in brain-tissue or cerebrospinal fluid samples from 20 PML patients. VP1 loop mutations occurred far more frequently than silent mutations.