Increased frequency of JC virus type 2 and of dual infection with JC virus type 1 and 2 in Italian progressive multifocal leukoencephalopathy patients

To verify the possibility of different role of JC virus genotypes in the etiology of progressive multifocal leukoencephalopathy, we analysed several JC virus isolates amplified from AIDS patients with and without progressive multifocal leukoencephalopathy and healthy controls by nucleotide sequencing. Cerebrospinal fluid (CSF), peripheral blood mononuclear cells (PBMCs) and urine from 52 AIDS patients suffering from various neurological diseases including 21 cases of progressive multifocal leukoencephalopathy, and PBMCs and urine from healthy subjects were evaluated by nested polymerase chain reaction (PCR) for the presence of DNA belonging to the highly conserved large T antigen (LT) of JC virus. The different JC virus subtypes were identified by nucleotide sequence analysis of the virion protein (VP1) genomic region. JC virus DNA was detected in all the CSF samples from the progressive multifocal leukoencephalopathy patients, but not in the CSF from non-progressive multifocal leukoencephalopathy cases, while the frequency of JC virus DNA detection in the PBMCs and urine did not differ among the three groups studied. JC virus type 2 was detected only in progressive multifocal leukoencephalopathy patients, and in particular in 52.4% of their CSF samples. Moreover, in the CSF of 19.0% of the progressive multifocal leukoencephalopathy cases, dual infection with both JC virus types 1 and 2 was found. The data obtained in this study indicate that the unexpected involvement of JC virus type 2, a strain not common in Italy, and the high frequency of dual infection with both JC virus types 1 and 2 in progressive multifocal leukoencephalopathy CSF, can be indications of risk factors for progressive multifocal leukoencephalopathy development.