摘要: Methods and compositions for determining whether a subject is at risk PML, including subjects being treated with immunosuppressants, by the harbors JCV variant reduced binding sialic acid relative to normal JCV, are presented. Furthermore, combinations of JCV-VP1 sequence variations that associated PML can be used as basis an assay identifying susceptible (e.g., early stage PML), or developing in response immunosuppressive treatment provided.