JC Virus infected choroid plexus epithelial cells produce extracellular vesicles that infect glial cells independently of the virus attachment receptor

The human polyomavirus, JCPyV, is the causative agent of progressive multifocal leukoencephalopathy (PML) in immunosuppressed and immunomodulated patients. Initial infection with JCPyV is common and the virus establishes a long-term persistent infection in the urogenital system of 50-70% of the human population worldwide. A major gap in the field is that we do not know how the virus traffics from the periphery to the brain to cause disease. Our recent discovery that human choroid plexus epithelial cells are fully susceptible to virus infection together with reports of JCPyV infection of choroid plexus in vivo has led us to hypothesize that the choroid plexus plays a fundamental role in this process. The choroid plexus is known to relay information between the blood and the brain by the release of extracellular vesicles. This is particularly important because human macroglia (oligodendrocytes and astrocytes), the major targets of virus infection in the central nervous system (CNS), do not express the known attachment receptors for the virus and do not bind virus in human tissue sections. In this report we show that JCPyV infected choroid plexus epithelial cells produce extracellular vesicles that contain JCPyV and readily transmit the infection to human glial cells. Transmission of the virus by extracellular vesicles is independent of the known virus attachment receptors and is not neutralized by antisera directed at the virus. We also show that extracellular vesicles containing virus are taken into target glial cells by both clathrin dependent endocytosis and macropinocytosis. Our data support the hypothesis that the choroid plexus plays a fundamental role in the dissemination of virus to brain parenchyma. Author summary JC polyomavirus (JCPyV) is a common human pathogen that causes a central nervous system demyelinating disease known as progressive multifocal leukoencephalopathy (PML). To cause PML, JCPyV has to traffic from peripheral tissues to the central nervous system (CNS) and invade glial cells. In previous work we found that choroid plexus epithelial cells express receptors for JCPyV in vivo and are fully susceptible to virus infection in vitro. In contrast, glial cells do not express the receptors for JCPyV and virus does not bind to these cells in human tissue sections. Because choroid plexus epithelial cells are known to relay information between the blood and the brain using extracellular vesicles we hypothesized that this could be important f