JC Polyomavirus Uses Extracellular Vesicles To Infect Target Cells

Abstract

The endemic human JC polyomavirus (JCPyV) causes progressive multifocal leukoencephalopathy in immune-suppressed patients. The mechanisms of virus infection in vivo are not understood because the major target cells for virus in the brain do not express virus receptors and do not bind virus. We found that JCPyV associates with extracellular vesicles (EVs) and can infect target cells independently of virus receptors. Virus particles were found packaged inside extracellular vesicles and attached to the outer side of vesicles. Anti-JCPyV antisera reduced infection by purified virus but had no effect on infection by EV-associated virus. Treatment of cells with the receptor-destroying enzyme neuraminidase inhibited infection with purified virus but did not inhibit infection by EV-associated virus. Mutant pseudoviruses defective in sialic acid receptor binding could not transduce cells as purified pseudovirions but could do so when associated with EVs. This alternative mechanism of infection likely plays a critical role in the dissemination and spread of JCPyV both to and within the central nervous system. IMPORTANCE JC polyomavirus (JCPyV) is a ubiquitous human pathogen that causes progressive multifocal leukoencephalopathy (PML), a severe and often fatal neurodegenerative disease in immunocompromised or immunomodulated patients. The mechanisms responsible for initiating infection in susceptible cells are not completely known. The major attachment receptor for the virus, lactoseries tetrasaccharide c (LSTc), is paradoxically not expressed on oligodendrocytes or astrocytes in human brain, and virus does not bind to these cells. Because these are the major cell types targeted by the virus in the brain, we hypothesized that alternative mechanisms of infection must be responsible. Here we provide evidence that JCPyV is packaged in extracellular vesicles from infected cells. Infection of target cells by vesicle-associated virus is not dependent on LSTc and is not neutralized by antisera directed against the virus. This is the first demonstration of a polyomavirus using extracellular vesicles as a means of transmission.

BK Polyomavirus Hijacks Extracellular Vesicles for En Bloc Transmission

“…1B). The population with the higher density peaked at 1.18 g/ml and likely corresponded to naked virions, consistent with the densities reported for the related JC polyomavirus (JCPyV) and Merkel cell polyomavirus (MCPyV) in such gradients (7,8). In contrast, the second population of infectious particles, called eBKPyVs, exhibited a density ranging between 1.05 and 1.15 g/ml, which was consistent with membrane association.…”

“…We expected that the membranes surrounding eBKPyVs would protect them from neutralization by antibodies. Such results were obtained with EV-associated JCPyV by Morris-Love et al (7). In contrast, we did not find any difference when we compared the sensitivities of eBKPyV and naked BKPyV to neutralization, by performing dose-response curves with the serum of a seropositive patient or commercially available IVIg preparations.…”

“…Thus, naked virions and eBKPyVs use different entry pathways, which could play a critical role in the dissemination and spread of BKPyV not only during primary infection but also during BKVN. Such an alternative mechanism of infection has also been elegantly demonstrated for EV-associated JCPyV (7). Besides, it has been proposed that this plays a critical role in the dissemination and spread of JCPyV both to and within the central nervous system (7,31).…”

“…Interestingly, it was shown in 1989 that the release of simian virus 40 (SV40) virions from epithelial cells was polarized and occurred without cell lysis (22), and we also observed the release of two populations of SV40 infectious particles, one of which cosedimented with EVs (data not shown). In addition, during the preparation of our manuscript, Morris-Love et al provided evidence that the JC polyomavirus (JCPyV), which shares 75% sequence homology with BKPyV, also uses EVs as a means of transmission (7). Thus, several members of the polyomavirus family hijack EVs for their release, and the question is raised for other polyomaviruses such as MCPyV and trichodysplasia spinulosa polyomavirus (TSPyV), which are associated with Merkel cell carcinoma and trichodysplasia spinulosa, respectively.…”

“…Such an alternative mechanism of infection has also been elegantly demonstrated for EV-associated JCPyV (7). Besides, it has been proposed that this plays a critical role in the dissemination and spread of JCPyV both to and within the central nervous system (7,31). For some viruses, en bloc delivery enables enhancement of the specific infectivity and viral fitness of viruses thanks to genetic cooperativity among viral quasispecies (17)(18)(19).…”