BK Polyomavirus Hijacks Extracellular Vesicles for En Bloc Transmission

Abstract

Most people are asymptomatic carriers of the BK polyomavirus (BKPyV), but the mechanisms of persistence and immune evasion remain poorly understood. Furthermore, BKPyV is responsible for nephropathies in kidney transplant recipients. Unfortunately, the sole therapeutic option is to modulate immunosuppression, which increases the risk of transplant rejection. Using iodixanol density gradients, we observed that Vero and renal proximal tubular epithelial infected cells release two populations of infectious particles, one of which cosediments with extracellular vesicles (EVs). Electron microscopy confirmed that a single vesicle could traffic tens of viral particles. In contrast to naked virions, the EV-associated particles (eBKPyVs) were not able to agglutinate red blood cells and did not use cell surface sialylated glycans as an attachment factor, demonstrating that different entry pathways were involved for each type of infectious particle. However, we also observed that naked BKPyV and eBKPyV were equally sensitive to neutralization by the serum of a seropositive patient or commercially available polyvalent immunoglobulin preparations, which occurred at a postattachment step, after endocytosis. In conclusion, our work shows a new mechanism that likely plays a critical role during the primary infection and in the persistence, but also the reactivation, of BKPyV. IMPORTANCE Reactivation of BKPyV is responsible for nephropathies in kidney transplant recipients, which frequently lead to graft loss. The mechanisms of persistence and immune evasion used by this virus remain poorly understood, and a therapeutic option for transplant patients is still lacking. Here, we show that BKPyV can be released into EVs, enabling viral particles to infect cells using an alternative entry pathway. This provides a new view of BKPyV pathogenesis. Even though we did not find any decreased sensitivity to neutralizing antibodies when comparing EV-associated particles and naked virions, our study also raises important questions about developing prevention strategies based on the induction or administration of neutralizing antibodies. Deciphering this new release pathway could enable the identification of therapeutic targets to prevent BKPyV nephropathies. It could also lead to a better understanding of the pathophysiology of other polyomaviruses that are associated with human diseases.

A non-enveloped arbovirus released in lysosome-derived extracellular vesicles induces super-infection exclusion

“…A seminal work on Hepatitis A virus revealed that virus particles are released both in enveloped and non-enveloped states, with the envelope protecting virus particles from neutralising antibodies [ 3 ]. More recently, it was reported that other non-enveloped lytic viruses, such as Coxsackievirus B [ 4 ], Hepatitis E virus [ 5 ], Poliovirus [ 6 , 7 ], Polyomavirus [ 8 , 9 ], Rotavirus and Norovirus [ 10 ], can also exit the cells as cloaked in extracellular vesicles (EV). Further, it was observed that EVs could contain multiple virus particles, allowing infection of a unique cell with many virus particles at a time [ 7 , 10 ].…”

Extracellular Vesicles in the Pathogenesis of Viral Infections in Humans

“…Most individuals are asymptomatics carriers of BK polyomavirus (BKPyV), which is responsible for nephropathies in recipients of kidney transplants [ 136 ]. Handala et al confirmed, via electron microscopy, that a single EV originating from an infected cell could transport dozens of viral particles [ 136 ].…”

“…Most individuals are asymptomatics carriers of BK polyomavirus (BKPyV), which is responsible for nephropathies in recipients of kidney transplants [ 136 ]. Handala et al confirmed, via electron microscopy, that a single EV originating from an infected cell could transport dozens of viral particles [ 136 ]. Additionally, the EV-associated BKPyV employed a cellular entry pathway differring from that of a non-EV-associated virion, as the EV-associated viral particles did not attach to the cell via cell surface sialylated glycans nor were they able to agglutinate red blood cells [ 136 ].…”

“…Handala et al confirmed, via electron microscopy, that a single EV originating from an infected cell could transport dozens of viral particles [ 136 ]. Additionally, the EV-associated BKPyV employed a cellular entry pathway differring from that of a non-EV-associated virion, as the EV-associated viral particles did not attach to the cell via cell surface sialylated glycans nor were they able to agglutinate red blood cells [ 136 ]. Overall, current research suggests that exosomes provide polyomaviruses a significant increase in tropism and virulence.…”

“…Overall, current research suggests that exosomes provide polyomaviruses a significant increase in tropism and virulence. However, there is a lack of data describing the mechanism for polyomavirus’ immune evasion and persistence [ 136 ].…”