A PML-Synonymous Mutation in MuPyV Results in Viral Escape from a Neutralizing Monoclonal Antibody

Abstract

Abstract Progressive Multifocal Leukoencephalopathy (PML) is a fatal demyelinating brain disease caused by JC polyomavirus (JCPyV). Most individuals are asymptomatically infected with JCPyV, but those with immunological perturbations are at risk of developing PML. PML pathogenesis is closely linked with the emergence of JCPyV mutants bearing mutations in regions of the VP1 major capsid protein that bind host cell receptors; these mutations may mediate immune escape or result in altered cell tropism/neurovirulence. A frequent PML mutation in VP1, S269F, is located in the receptor-binding pocket of the virus capsid. To investigate the effects of the S269F mutation on viral infection and the immune response, we utilized mouse polyomavirus (MuPyV) as a natural pathogen-host model of JCPyV infection. We generated a MuPyV mutant containing a V296F substitution in VP1, which maps to the S269F mutation in JCPyV, to ask whether this mutation on immune evasion and host cell tropism. The MuPyV DNA genome incorporates cellular histones; thus we generated infectious fluorescent MuPyV by infecting a host cell line expressing an H2B histone-GFP protein. Using this fluorescently-labeled virus, we determined that a VP1 monoclonal antibody (mAb), which neutralizes wild type virus, binds the V296F mutant, but is unable to block viral attachment and infection. We are currently generating cryo-EM reconstructions to visualize the interaction of this mAb with the wild type and V296F mutant viruses. This data suggests that this PML-synonymous mutation in MuPyV may allow escape from antiviral humoral immunity.