JC polyomavirus (JCV) is an important human pathogen that causes the fatal demyelinating disease progressive multifocal leukoencephalopathy (PML). In this study we further delineate the early events of JCV entry in human glial cells and demonstrate that a pentameric subunit of the viral capsid is able to recapitulate early events in viral trafficking. We show that JCV traffics to the endoplasmic reticulum (ER) by 6h post infection, and that VP1 pentamers arrive at the ER with similar kinetics. Further, this JCV localization to the ER is critical for infection, as treatment of cells with agents that prevent ER trafficking, ER function, or ER quality control reduce JCV infectivity. These pentamers represent a new tool to study polyomavirus entry, and will be particularly useful in studying recently identified polyomaviruses that are difficult to propagate.

Autophagy is important for a variety for virus life cycles. We sought to determine the role of autophagy in human BK polyomavirus (BKPyV) infection. The addition excess amino acids during viral infection reduced BKPyV infection. Perturbing autophagy levels using inhibitors, 3-MA, bafilomycin A1, and spautin-1, also reduced infection, while rapamycin treatment of host cells increased infection. siRNA knockdown of autophagy genes, ATG7 and Beclin-1, corresponded to a decrease in BKPyV infection. BKPyV infection not only correlated with autophagosome formation, but also virus particles localized to autophagy-specific compartments early in infection. These data support a novel role for autophagy in the promotion of BKPyV infection.

The human polyomavirus, JCV, has a highly restricted tropism and primarily infects glial cells. The mechanisms restricting infection of cells by JCV are poorly understood. Previously we developed and described a glial cell line that was resistant to JCV infection with the aim of using these cells to identify factors that determine JCV tropism. Gene expression profiling of susceptible and resistant glial cells revealed a direct correlation between the expression of inflammatory cytokines and susceptibility to JCV infection. This correlation manifested at the level of viral gene transcription. Previous studies have suggested a link between an increase in cytokine gene expression in HIV patients and the development of PML and these data supports this hypothesis.

JC virus (JCV) is a human polyomavirus that infects the majority of the human population worldwide. It is responsible for the fatal demyelinating disease Progressive Multifocal Leukoencephalopathy. JCV binds to cells using the serotonin receptor 5-HT(2A)R and alpha(2-6)- or alpha(2-3)-linked sialic acid. It enters cells using clathrin-dependent endocytosis and traffics to the early endosome and possibly to the endoplasmic reticulum. Viral DNA is then delivered to the nucleus where transcription, replication, and assembly of progeny occur. We found that the early regulatory protein large T antigen accumulates in microdomains in the nucleus adjacent to ND-10 or PML domains. This observation prompted us to explore the role of these domains in JCV infection. We found that a reduction of nuclear PML enhanced virus infection and that an increase in nuclear PML reduced infection. Infection with JCV did not directly modulate nuclear levels of PML but our data indicate that a host response involving interferon beta is likely to restrict virus infection by increasing nuclear PML.

The demyelinating disease progressive multifocal leukoencephalopathy (PML) is caused by the human polyomavirus, JCPyV, under conditions of prolonged immunosuppression. Initial infection is asymptomatic, and the virus establishes lifelong persistence in the host. Following the loss of immune surveillance, the virus can traffic to the central nervous system and infect oligodendrocytes to cause demyelination and PML. The mechanisms involved in glial cell infection are not completely understood. In a screen for N-glycosylated proteins that influence JCPyV pathology, we identified Adipocyte Plasma Membrane Associated Protein (APMAP) as a host cell modulator of JCPyV infection. The removal of APMAP by small interfering siRNA as well as by CRISPR-Cas9 gene editing resulted in a significant decrease in JCPyV infection. Exogenous expression of APMAP in APMAP knockout cell lines rescued susceptibility to infection. These data suggest that virus infection of glial cells is dependent on APMAP.