Abstract
Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system (CNS) caused by reactivation of dormant JC polyomavirus (JCPyV). PML was mainly observed in immunocompromised individuals, such as HIV-positive patients, autoimmune disease patients, and cancer patients. Given that the presence of anti-JCPyV antibodies in serum is a risk indicator for PML development, it is essential to monitor anti-JCPyV antibody levels. In the present study, we established reporter-based single-infection neutralization assays for JCPyV and the genetically similar BK polyoma virus (BKPyV). We then confirmed the lack of cross-reactivity between the two viruses using test sera obtained from mice immunized with plasmids encoding the JCPyV or BKPyV capsid. Next, we compared neutralization antibody titers in sera from healthy donors, patients with multiple sclerosis (MS), and HIV-positive patients using an in-house enzyme-linked immunosorbent assay (ELISA) with JCPyV-like particles (virus-like particles; VLPs). A positive correlation was demonstrated between the neutralization titer (75% infectious concentration; IC75) against JCPyV and the antibody titer obtained by VLP-based JCPyV ELISA. This assay system may be applied to detect antibodies against other PyVs by generation of pseudoviruses using the respective capsid expression plasmids, and is expected to contribute to the surveillance of PyV as well as basic research on these viruses.