In one aspect, the disclosure provides neutralizing antibodies against JCV and methods for the treatment of PML. In some embodiments, aspects of the invention relate to an isolated JC-vims neutralizing monoclonal antibody against JCV capsid protein VPI (JCV-VP1). In some embodiments, the antibody suppresses infectivity of the JC-vims. In some embodiments, the antibody binds the sialic acid binding pocket of JCV-VP1.